Zircon (U-Th)/He (ZHe) dates are presented from eight samples (⁠n=55⁠) collected from three ranges including the Carrizo and Franklin Mountains in western Texas and the Cookes Range in southern New Mexico. ZHe dates from Proterozoic crystalline rocks range from 6 to 731 Ma in the Carrizo Mountains, 19 to 401 Ma in the Franklin Mountains, and 63 to 446 Ma in the Cookes Range, and there is a negative correlation with eU values. These locations have experienced a complex tectonic history involving multiple periods of uplift and reburial, and we use a combination of forward and inverse modeling approaches to constrain plausible thermal histories. Our final inverse models span hundreds of millions of years and multiple tectonic events and lead to the following conclusions: (1) Proterozoic exhumation occurred from 800 to 500 Ma, coinciding with the break-up of Rodinia; (2) elevated temperatures at approximately 100 Ma occurred during final development of the Bisbee basin and are a likely result of elevated heat flow in the upper crust during continental rifting; (3) a pulse of cooling associated with Laramide shortening is observed from 70 to 45 Ma in the Cooks Range and 80 to 50 Ma in the Franklin Mountains, whereas the Carrizo Mountains were largely unaffected by this event; and (4) final cooling to near-surface temperatures began 30–25 Ma at all three locations and was likely a result of Rio Grande rift extension. These data help to bridge the gap between higher and lower temperature isotopic systems to constrain complex thermal histories in tectonically mature regions.Thermochronology is a powerful tool to constrain the ages and durations of past geologic events because exhumation leads to cooling, the timing of which is recorded by different isotopic systems. Cooling ages are interpreted in context of closure temperatures of different minerals (e.g., [1]) in which diffusion of radiogenic daughter isotopes slows significantly below a known temperature range. However, there can be a gap in the dates obtained from high-temperature thermochronologic systems such as titanite U-Pb, hornblende 40Ar/39Ar, and mica 40Ar/39Ar, which record the timing of cooling from ~600 to 300°C [2], versus low-temperature systems such as apatite fission-track and (U-Th)/He, which record the timing of cooling below 120–60°C and 90–30°C, respectively [3, 4]. Multidiffusion domain (MDD) analysis of K-feldspar using the 40Ar/39Ar system [5] could fill in the temperature gap between biotite 40Ar/39Ar and apatite (U-Th)/He, although it has been shown to be problematic in some instances (e.g., [6–8]), whereas MDD analysis of muscovite shows promise [9, 10]. Zircon fission-track, sensitive to temperatures of ~270–210°C [11], is a widely used thermochronometer to partially fill this temperature range, although there can still be a gap in the thermochronologic history between 40Ar/39Ar methods and apatite (U-Th)/He because of variations in closure temperature related to cooling rate.Limitations in deciphering thermochronologic histories related to this gap may be overcome by the work of Guenthner et al. [12], who describe a helium diffusion model that incorporates an important relationship between zircon (U-Th)/He (ZHe) dates and radiation damage accumulation and annealing in zircon crystals. This relationship is typically expressed by intrasample ZHe dates that sometimes span hundreds of millions of years. For grains that have experienced identical thermal histories, differences in ZHe dates are governed by differences in the effective uranium (⁠eU=U+0.235Th⁠) that are reflected as either positive or negative ZHe date-eU relationships. These relationships result from differences in the ability of each grain to retain helium that are dependent on eU values. Positive and negative ZHe date-eU trends are the cumulative result of the overall thermal history and the effects of radiation damage on helium diffusion, and these allow for continuous thermal histories to be reconstructed. Helium diffusion models in zircon suggest a temperature sensitivity window ranging from approximately 210 to 50°C [12, 13], which partially overlaps with zircon fission-track and K-feldspar 40Ar/39Ar data at the higher range and with apatite fission-track and (U-Th)/He techniques at the lower end. The large ZHe temperature sensitivity window makes it possible to constrain more complete and continuous thermal histories, offering an opportunity to bridge the gap between higher and lower temperature methods. Previous studies have relied on this intrasample spread in ZHe dates to investigate a wide range of geologic processes, such as the Proterozoic thermal history of rocks (e.g., [14]), timing of Laramide exhumation [15], and development of the South American passive margin [16]. However, additional studies are needed to further assess the efficacy of this method.Proterozoic crystalline rocks of southwestern North America have experienced a complex tectonic history that spans over a billion years (e.g., [17]). In southwestern New Mexico and western Texas, this history includes, but is not limited to, Mesoproterozoic and Neoproterozoic assembly and break-up of the supercontinent Rodinia, Pennsylvanian-Permian Ancestral Rocky Mountain deformation, widespread Paleozoic and Mesozoic sedimentation, latest Cretaceous-Eocene Laramide compression, and culminating with Neogene extension related to development of the Rio Grande rift (e.g., [18–22]).40Ar/39Ar cooling ages from Proterozoic crystalline rocks in New Mexico typically range from approximately 1600 to 1000 Ma and reflect thermal pulses during intracontinental tectonism and plutonism (e.g., [23, 24]). However, apatite fission-track and (U-Th)/He studies from the same region in New Mexico yield dates that are typically younger than about 100 Ma, reflective of cooling during exhumation associated with the Laramide orogeny and Rio Grande rift extension [25–28]. These two disparate datasets each provide brief snapshots into a more complex thermal history, but a continuous thermal record remains lacking, particularly in the range from about 1000 Ma to younger than 100 Ma. Thus, this region of the southwest U.S. is an exceptional natural laboratory for investigating long-term thermal histories using ZHe thermochronologic methods.Here, we present the first ZHe dates from three ranges in southern New Mexico and west Texas: the Cookes Range in New Mexico and the Franklin Mountains and Carrizo Mountains of west Texas (Figure 1). ZHe dates for each sample have significant intrasample ZHe date variability which we use to produce a series of forward and inverse thermal history models. We also present ZHe data from several detrital samples and discuss the ways in which these data compliment ZHe dates from crystalline samples. Our new thermal history models capture multiple pulses of cooling and reheating that can be directly tied to known geologic events and provide an important link between disparate higher-temperature 40Ar/39Ar cooling ages and lower-temperature apatite fission-track and (U-Th)/He datasets. Finally, we evaluate the use of both inverse and forward models to compare the long-term thermal history of rocks in this region and determine an improved application of the ZHe thermochronology method.From 1.8–1.6 Ga, Paleoproterozoic growth of southwest Laurentia occurred by progressive accretion of arc terranes, including the Yavapai and Mazatzal Provinces [29–31], where final assembly of the supercontinent Rodinia occurred during Grenville tectonism in the late Mesoproterozoic (Figure 1) [32]. The Grenville orogeny in southwestern Laurentia records arc accretion and continent-continent collision between 1350 and 980 Ma [33]. Some of the Grenville orogenic foreland is exposed in western Texas in the Carrizo Mountains [33, 34]. The ca. 1380–1327 Ma Carrizo Mountain Group (Figure 1(b)), composed of immature clastic rocks, within-plate rhyolitic volcanic rocks, and minor carbonates, likely records rifting of continental crust within a back-arc basin during overall convergence [35–37]. The Franklin Mountains (Figure 1(b)) record continued sedimentation within this back-arc basin from ca. 1260–1240 Ma [36] until continent-continent collision ca. 1150–1120 Ma [36]. North of the Grenville deformation front (Figure 1), magmatism in the Franklin Mountains is represented by ~1.1 Ga plutonic and volcanic rocks, including the Red Bluff granite which was targeted in this study for ZHe dating [38, 39]. Petrological and geochemical studies classify the Red Bluff granite as a within-plate, A-type granite and support a model where these rocks were emplaced within a more regional strain field dominated by NW-SE shortening and orthogonal NE-SW extension related to Grenville convergence [39, 40]. Final shortening along the southern margin of Laurentia occurred between ~1035 and 980 Ma [33, 41].Models for the breakup of Rodinia suggest diachronous disassembly with early rifting occurring between 780 and 680 Ma, followed by the main rifting phase between 620 and 550 Ma [18, 21, 42, 43]. Supercontinent breakup may have also been accompanied by a major pulse of denudation recorded in ZHe datasets [14]. Breakup was followed by deposition of Paleozoic passive margin sediment on Precambrian basement (e.g., [44]) to create the Great Unconformity, a globally significant feature in the rock record. In southern New Mexico and western Texas, Proterozoic crystalline rocks beneath the Great Unconformity typically consist of 1.45-1.35 and some 1.1 Ga granites intruded into 1.68-1.65 supracrustal rocks of the Mazatzal Province [17]. These rocks are generally overlain by the Cambrian-Ordovician Bliss Sandstone, which define a Great Unconformity that encompasses 600 m.y. to more than 1,000 m.y. of missing time.Late Paleozoic deformation in western North America resulted in the development of the Ancestral Rocky Mountains (e.g., [19, 45]). In the Cookes Range (Figure 1), Ancestral Rocky Mountain deformation is evident by a near absence of sedimentation from approximately 320 to 290 Ma [19]. In contrast, the Franklin Mountains record near continuous sedimentation during this timeframe [46], suggesting minimal exhumation. In west Texas, deformation locally stripped early Paleozoic sedimentary rocks and exposed Proterozoic basement which was subsequently covered by early Permian rocks [47].Starting in the Late Jurassic, a continental rift developed in the region of northern Sonora, Mexico, and southern Arizona (e.g., [48]). The resulting rift basin was originally termed the Bisbee basin [49] and now referred to as the Mexican Border Rift (Figure 1) [50]. Marine strata have Tethyan fossils indicating a connection to the Gulf of Mexico (e.g., [51]). Volcanogenic material such as mafic volcanic rocks and pillow basalts were deposited in this rift [52–54]. Several of the samples from this study were collected from the northern rift shoulder in southwestern New Mexico. Rifting in this region ended by the middle Cretaceous based on subsidence studies indicating a transition from rift-related thermal subsidence to the formation of a foreland basin beginning in the Albian [50, 55].Late Mesozoic to Eocene deformation during the Laramide orogeny involved northeast-directed crustal shortening that resulted in a series of uplifts and basins [22]. These basins and uplifts trend northwest in southern New Mexico and extend into northern Mexico and western Texas; our Carrizo Mountains study site lies at the easternmost extent of Laramide deformation (Figure 1). These structures were extensively dissected by younger continental extension related to development of the Rio Grande rift [22]. Initial rifting in southern New Mexico began during the Oligocene to produce a series of fault-block uplifts and basins that create the modern topographic grain of the region [20]. The Cookes Range is bounded on three sides by normal faults related to development of the Rio Grande rift, and the Franklin Mountains and Carrizo Mountains are both associated with active normal faults that document continued deformation in this region.Uplifts within the southern Rio Grande rift, such as the Carrizo Mountains, Franklin Mountains, and Cookes Range, expose Proterozoic crystalline basement that has been exhumed to the surface in the footwalls of Cenozoic normal faults. Samples were collected from crystalline basement rocks and clastic coarse-grained sandstone or granule conglomerate sedimentary rocks because they likely contain abundant zircon crystals. In addition, sample locations were targeted to avoid possible effects of widespread Oligocene plutonism. Sample collection along an E-W transect across southern New Mexico suggests that many samples farther to the west have been completely reset, and all ZHe dates are Oligocene-Miocene [25, 56, 57]. These studies found that along this EW transect, the Cookes Range was the westernmost location to preserve older ZHe dates, although it does contain Oligocene intrusive and extrusive rocks (Figure 1(b)) that may have partially affected the ZHe data (as described in more detail below). Therefore, mountain ranges east of and including the Cookes Range were selected because they are removed from the effects of Oligocene magmatism and likely retain a record of the older, long-term thermal history.Whole-rock samples were processed using standard mineral separation techniques to isolate the zircon fraction. Zircon separates were inspected with a petrographic microscope equipped with a digital camera used for measuring grain dimensions, including length, width, and depth. Ideal zircon crystals for ZHe thermochronology are euhedral with no inclusions and a minimum diameter of 70 μm. Five to ten of the best zircons from each sample were hand-picked and loaded into Nb tubes for analysis. All samples were analyzed at the Thermochronology Research and Instrumentation Laboratory at CU Boulder (CU TRaIL).Since all samples yield a range of ZHe dates and eU values, a forward modeling approach was first used to constrain the long-term thermal history of each mountain range since crystallization of the sample. Forward modeling allows for the calculation of a thermochronometric age from a determined time-temperature path, using helium diffusion or annealing kinetics [58]. Multiple hypothetical time-temperature paths are investigated that are based on known geologic constraints, including formation of the Great Unconformity, periods of Paleozoic and Mesozoic sedimentation, and possible exhumation during Ancestral Rocky Mountain, Laramide, and Rio Grande rift deformation events (Table S1, Fig. S1). For each of these paths, we vary maximum or minimum temperatures achieved during different segments of the sample’s thermal history. ZHe date-eU curves are calculated from each t-T path using a Matlab script (Guenthner, pers. comm., 2018) that incorporates the zircon radiation damage accumulation and annealing model (ZRDAAM) from Guenthner et al. [12]. Inputs include a specific time-temperature path, zircon eU values, and zircon grain size. These date-eU paths are then compared to ZHe data. Model date-eU paths that are drastically different than the observed data are not viable thermal histories. By varying different segments of the thermal history, the model date-eU paths from each sample are incrementally adjusted to provide a range of permissible thermal histories. This approach assumes that the only control on ZHe dates is helium diffusion related to crystal damage and annealing that evolves through time. However, the spread in ZHe dates could also be influenced by other factors such as crystal size, U and Th zoning in the zircon crystal, and implantation of helium from neighboring grains (e.g., [59–61]). Although possible He implantation is generally not known, and zoning information is not typically obtained in ZHe studies, the effects of crystal size on resulting date-eU curves can be investigated. To do this, we use a method similar to other workers (e.g., [14, 62, 63]) in which three separate date-eU curves are modeled to create an envelope within which the ZHe dates should lie. To create the three curves, we use the mean grain size±2 standard deviations⁠.We also use inverse modeling to further refine possible thermal histories. Whereas forward modeling was used to test tens of possible paths, an inverse modeling approach can test tens of thousands of possible paths and explore additional possible t-T paths that are permissible by the ZHe data. Inverse modeling allows for the calculation of t-T paths that match measured thermochronometric ages to within a specified amount of statistical error [58]. We use HeFTy v. 1.9.3 [4], which uses a Monte Carlo method to plot possible time-temperatures paths based on entered data. Input data into HeFTy includes U, Th, Sm concentrations, grain radius, measured age, and age uncertainty. HeFTy requires a set of temperature-time parameters for modeling, such as start times, end times, and temperatures. All inverse models explore a total of 50,000 paths, where resulting “acceptable” paths have goodness-of-fit parameters >0.05, and “good” paths have goodness-of-fit criteria >0.5. Complete model constraints and inputs are available in Table S1 and Figure S1 and follow methods outlined in Flowers et al. [64].Finally, we explore the significance of detrital ZHe dates from samples collected from the Cookes Range and Franklin Mountains. In contrast to igneous rock samples, partially reset detrital zircon grains only share a common post-depositional thermal history, but each individual grain may still retain an older, unique thermal imprint. As a result, they should not necessarily lie along a single date-eU curve, but will instead have potentially highly variable ZHe dates [15]. Analysis of detrital grains entails constructing inheritance envelopes for each location, following methods outlined in Reiners et al. [65] and Guenthner et al. [15]. The inheritance envelope is created by combining a zero-inheritance date-eU curve with multiple maximum inheritance curves that assume different zircon crystallization ages. The zero-inheritance date-eU curve is constructed from the thermal history that begins at the depositional age of the detrital sample and assumes no inherited radiation damage at that time, a situation that can be achieved by either complete resetting of detrital grains at the time of deposition or zero U-Pb ages at the time of deposition. Maximum inheritance curves incorporate the effects of inherited radiation damage by assuming zircon crystallization at surface temperatures prior to the depositional age. These grains then share an identical thermal history as the zero-inheritance curve after deposition. When combined, these different curves yield an inheritance envelope that should contain the observed ZHe dates if the t-T path is a plausible result of the sample’s thermal history.A total of 37 new ZHe dates are presented, including 10 dates from the Carrizo Mountains, 20 dates from the Franklin Mountains, and seven dates from the Cookes Range. These are combined with 18 ZHe dates previously reported [25, 56], including nine dates from the Franklin Mountains and nine dates from the Cookes Range (Figure 2). In total, this project incorporates 55 individual grain ZHe dates from eight samples to investigate patterns in long-term thermal histories spanning hundreds of millions of years (Table 1).Ten ZHe dates from two samples were obtained from the Mesoproterozoic Hackett Peak Formation of the Carrizo Mountain Group in the northern Carrizo Mountains (Figures 1(b) and 2, Table 1). These data show a wide range in both ZHe date (6–731 Ma) and eU concentration (52–1729 ppm). There is also a well-defined negative ZHe date-eU correlation that shows a steep trend until eU values of approximately 400 ppm. ZHe dates show a slight positive relationship with grain radius. The oldest ZHe dates correspond to the largest grains, suggesting a possible grain size control on ZHe dates.Twenty-nine ZHe dates from four samples were obtained from the Mesoproterozoic Red Bluff granite and the Cambrian-Ordovician Bliss Sandstone in the Franklin Mountains (Figures 1(b) and 2). ZHe dates from the Red Bluff granite have a large range from 19 to 401 Ma. Their eU concentrations show a large spread as well, ranging from 63 to 828 ppm. Together, these data have a slightly negative, although poorly defined, ZHe date-eU correlation, where older ZHe dates typically correspond to lower eU values. However, individual samples from the Franklin Mountains do not always show a negative trend, and some (17FR03) show more of a flat trend. The majority of crystalline zircon grains from the Franklin Mountains cluster within a narrow size range of 35-55 μm such that a ZHe date-grain size trend is not observed. ZHe dates from the Bliss Sandstone show a ZHe date range of 62–649 Ma, with eU concentrations ranging from 90 to 374 ppm. Many of these ZHe dates are older than ZHe dates from crystalline basement samples, and together, they define a negative trend date-eU trend. This sample displays a wider range in crystal sizes than the crystalline grains, where most of the grains are older and larger. However, ZHe dates do not appear to increase with larger crystals.A total of 16 ZHe dates are presented from the Cookes Range (Figures 1(b) and 2). Ten ZHe dates are from a Proterozoic granite exposed in Rattlesnake Ridge along the southern edge of Cookes Range. These ZHe dates range from 63 to 446 Ma with an eU range of 232–945 ppm. These data show a steep negative ZHe date-eU relationship at lower eU values, which transitions to a flatter trend at higher eU values.An additional six ZHe dates were obtained from the Permian Abo Formation from the Cookes Range. ZHe dates range from 44 to 130 Ma, with corresponding eU values from 56 to 351 ppm. Although this sample does not yield as large of an eU range, these ZHe dates have a slight negative trend where older ZHe dates correspond to lower eU values. In contrast to Franklin Mountains samples, detrital grains from the Cookes Range are mostly younger than crystalline zircon grains. Individual ZHe dates do not seem to show a well-defined trend with grain size.Hypothetical time-temperature paths were constructed for crystalline samples at each location for two purposes (Figures 3–5). First, these paths are used to eliminate thermal histories that are incompatible with the observed ZHe dates and begin to refine possible thermal histories. Second, these paths are used to test which periods of burial or uplift have the largest effect on the resulting ZHe date-eU pattern and which events have relatively minor effects. To do this, we used a Matlab routine that incorporates the zircon radiation damage accumulation and annealing model (ZRDAAM) from Guenthner et al. [12]. Forward model outputs are calculated ZHe date-eU curves that are predicted from the input data. Hypothetical time-temperature paths were constructed for each mountain range by varying the amount of burial or exhumation from different deformational events in that area. Specific geologic constraints for each location are provided in Table S1 and Figure S1. Each ZHe date-eU curve calculated from an input time-temperature is then compared to the ZHe data collected from each location. Below, we first present preliminary forward models for each of the three study locations. Then, we refine these results and produce best-fit models that represent the closest match to the observed data acquired through this approach.Four sets of representative t-T paths were constructed for the Carrizo Mountains that each varies a different segment of the history. The first set of representative paths varies the timing of Proterozoic exhumation prior to deposition of Paleozoic strata (Figure 3(a)). Three possible thermal histories are examined to test how sensitive ZHe data are to Proterozoic exhumation. These three paths all cool through the range of 500 to 350°C at 1035 Ma, consistent with 40Ar/39Ar hornblende and muscovite data [41]. From there, they diverge to include early exhumation to 15°C at 1000 Ma (blue path), intermediate exhumation from 300 to 15°C from 800 to 700 Ma (teal path), and late exhumation from 300 to 15°C from 600 to 500 Ma (yellow path) (Figure 3(a)). The post-500 Ma segments of these paths are identical. These three paths each yields a date-eU curve that is notably different than the others, suggesting that the Proterozoic cooling history imparts a significant influence on the resulting date-eU relationship. Of the three proposed cooling scenarios, rapid exhumation to the surface from 1050 to 1000 Ma predicts maximum ZHe dates that are similar to the observed dates, although it does not match the negative slop of the data. However, this result supports rapid cooling followed by prolonged residence at the Earth’s surface.The second set of representative paths builds off the first iteration by using 1050–1000 Ma exhumation from Figure 3(a). Here, we vary the depth of maximum Paleozoic burial after formation of the Great Unconformity (Table S1, Figure 3(b), and Figure S1). Eight thermal histories are examined that vary the maximum burial temperature from 110 to 180°C at 325 Ma, signifying maximum burial before Ancestral Rocky Mountain uplift. The resulting ZHe date-eU patterns vary slightly in width, but there is a larger variation in the maximum ZHe age. However, maximum burial depths of less than 140°C all yield almost identical date-eU paths, suggesting that this dataset is insensitive to lower temperatures. Modeled date-eU paths of 110–140°C predict maximum ZHe dates that are most similar to the observed data.The third set of representative paths incorporates 1050–1000 Ma Proterozoic cooling and uses a maximum Paleozoic burial temperature of 120°C. This iteration varies depths of Mesozoic burial after Ancestral Rocky Mountain uplift (Table S1; Figure S1). Eight thermal histories are examined that vary maximum depth from 130 to 200°C at 80 Ma (Figure 3(c)). These t-T paths yield date-eU curves with a wide range in maximum ZHe dates and widths. When compared to the observed data, there is a trade-off between matching the oldest ZHe dates and matching the negative date-eU slope of the data. For example, a temperature of 160°C predicts oldest ZHe dates that match the observed data, while a temperature of 170-180°C predicts a negative slope that closely follows the data. Of the calculated date-eU curves, a maximum Mesozoic burial depth of 170°C gives a predicted curve that somewhat matches the steep negative date-eU slope in the observed data, as well as the kink where the slope changes to a much shallower trend.The final set of representative paths was constructed to vary the transition from Laramide shortening-related uplift to Rio Grande rift extensional uplift. To do this, we vary the temperature at which the sample resided after Laramide uplift and prior to Rio Grande rift uplift (Figure 3(d)). Eight thermal histories are examined that vary the temperature between 60 and 130°C from 40 to 30 Ma. All of the paths are nearly identical, suggesting that the overall ZHe date-eU pattern is not as sensitive to this younger deformational event in the Carrizo Mountains.Neogene faulting and tilting of the Franklin Mountains expose Proterozoic granite along the eastern base of the range (Figure 1(b)). A total of three Proterozoic samples from the Franklin Mountains were collected from various locations along the range. Although they were all collected from similar elevations, calculated depths for each sample beneath the Great Unconformity varied. For example, although samples 15FR03 and 17FR03 resided at paleodepths of 361 m and 229 m, respectively, sample 17FR04 was located at a significantly greater depth of approximately 1587 m. For modeling purposes, samples 15FR03 and 17FR03 were combined into a single sample because they likely experienced near-identical thermal histories, and together, these grains show a larger range in eU values that allows for tighter constraints on the thermal history. ZHe dates from sample 17FR04 were excluded, and no attempt was made to model this sample, in part, because only four ZHe dates are available for this sample with limited spread in eU values (Figure 2, Table 1).Four sets of representative paths were constructed for the Franklin Mountains (Figure 4). The four sets of paths are presented in the order of decreasing date-eU curve variability. For example, Mesozoic burial yields date-eU curves that vary widely in terms of maximum ZHe date and the location of the steep negative trend, whereas different Proterozoic paths have little effect on date-eU curves. The first set of representative paths was constructed to vary the amount of Mesozoic burial after regional uplift ceased in the Cretaceous (Figure 4(a)). Eight paths are examined that vary the maximum burial temperature between 80 and 220°C at 80 Ma, signifying maximum burial before Laramide uplift. These paths produce date-eU curves with marked differences. The most notable differences between these curves are the maximum ZHe date and the position of the negative slope, suggesting that this segment of the path has a significant effect on the final ZHe date-eU curve. Of the eight proposed t-T paths, burial to 180°C yields a date-eU curve that closely aligns with the observed data.The second set of representative paths was constructed to vary the amount of Paleozoic burial after the Great Unconformity. This path includes a period of constant temperature from 250 to 150 Ma because in the Franklin Mountains, lower Cretaceous rocks unconformably overlie Permian rocks, suggesting a period of no deposition [66]. Eight thermal histories are examined that vary the maximum burial temperature between 40 and 180°C from 250 to 150 Ma (Figure 4(b)). A minimum temperature of 40°C was chosen to represent minimal Paleozoic burial, and a maximum temperature of 180°C was chosen because it is near the higher end of the ZHe temperature sensitivity window. The resulting date-eU curves are similar at eU values greater than 400 ppm. At lower values, the curves diverge to form peaks at different ZHe dates. Although multiple resultant date-eU curves roughly match the observed ZHe dates, an intermediate burial temperature of 120°C produces a curve that bisects the data.Next, the transition from Laramide shortening-related uplift to Rio Grande rift extensional uplift is varied (Figure 4(c)). Eight possible thermal histories are examined that vary post-Laramide temperatures between 40 and 180°C at 40 Ma. Higher burial temperatures yield date-eU curves that are nearly flat. Burial temperatures less than about 120°C produce curves with little variation, yet these curves predict oldest ZHe dates that more closely align with the observed data. A temperature of 60°C is selected because it produces a curve with the highest ZHe peak.In the final iteration, the Proterozoic thermal history is examined (Figure 4(d)). All of the possible paths are forced to near-surface temperatures shortly after crystallization because the Red Bluff granite intrudes the overlying Thunderbird Rhyolite in some locations, suggesting it was emplaced at shallow levels in the crust. From here, eight different paths are examined that postulate that the Red Bluff granite may have been buried and then exhumed back to the surface prior to deposition of Paleozoic strata. Maximum burial temperatures vary from 15 to 200°C. In addition, two different times of exhumation are investigated, including exhumation from 800 to 750 Ma and exhumation from 650 to 550 Ma. These different t-T paths give predicted date-eU curves with little variability, suggesting that the observed ZHe date-eU values are not strongly affected by the Proterozoic thermal history of these samples. This is consistent with the observed ZHe dates, which are mostly younger than 250 Ma.Four sets of representative paths were constructed for Cookes Range. The first set of paths was constructed to vary the amount of Paleozoic burial after the Great Unconformity. Eight thermal histories are examined that vary the maximum burial depth to temperatures that range from 60 to 200°C at 325 Ma, signifying maximum burial before Ancestral Rocky Mountain uplift (Figure 5(a)). The higher temperature t-T paths yield date-eU curves with prominent flat pediments at intermediate eU values. This pediment disappears with lower burial temperatures. Although the observed ZHe date-eU relationships do not show this pediment, the higher burial temperatures provide a better match because the maximum ZHe dates are similar to the observed dates, whereas lower burial temperatures predict ZHe dates older than 1000 Ma.The second set of paths was constructed to vary the amount of Mesozoic burial after Ancestral Rocky Mountain uplift. These paths use a Paleozoic burial temperature constraint of 160°C (Figure 5(a)). Eight thermal histories are examined that vary the temperature from 60 to 200°C (Figure 5(b)). The resulting date-eU curves show dramatic variability. At lower burial temperatures, a prominent pediment is observed, although this pediment gradually diminishes at higher temperatures. A Mesozoic burial temperature of 160°C produces a date-eU curve that lies along the path of observed ZHe dates and captures the broad date-eU pattern at intermediate and high eU values (200–1000 ppm).In the third iteration, Paleozoic and Mesozoic burial temperatures are held at 160°C, and the transition from Laramide shortening to Rio Grande rift extensional uplift is varied from 20 to 160°C (Figure 5(c)). Lower temperatures of 20–120°C produce nearly identical date-eU curves. The highest temperature of 160°C predicts oldest ZHe dates that are too young to match the observed data. Because lower temperatures appear to be insensitive to the resulting date-eU pattern, a temperature of 80°C closely follows the observed dates and is used in the final iteration.Finally, the three previous iterations are used to constrain the Phanerozoic segments of the t-T history, and the Proterozoic uplift history is varied (Figure 5(d)). Five possible histories are evaluated that vary the timing of exhumation to the surface. Three paths of either early cooling or constant cooling are nearly identical at eU values greater than 250 ppm. At lower values, they diverge. t-T paths involving rapid cooling younger than 1000 Ma produce distinctively broad date-eU patterns. The three early cooling scenarios yield date-eU curves that are similar to the observed ZHe date-eU trends. The only significant difference between these three date-eU curves is the predicted maximum ZHe date. However, no ZHe grains are available with eU values lower than 200 ppm where these paths diverge.The above analysis serves as a useful guide for interpreting ZHe datasets. For all three locations, the final forward models are nonunique such that our approach to refine the thermal history only manages to produce a single t-T path out of many. However, this approach does highlight which segments of the t-T history the resulting date-eU curve is most sensitive to. For example, at all three locations varying the magnitude of Mesozoic burial has a drastic effect on the resulting date-eU curves. In the Carrizo Mountains and Cookes Range, the timing of Proterozoic exhumation also produces date-eU curves that show significant differences. In contrast, at all three locations, the post-Laramide/pre-Rio Grande rift temperature does not appear to significantly affect the date-eU curves. This analysis highlights some of the uses of a forward modeling technique for understanding which events may be preserved in the thermal record and which events the data are not sensitive to. Below, we use these results and incorporate the possible effects of grain size to produce our best-fit forward models.The preliminary forward modeling efforts above fail to yield a single t-T path that adequately aligns with the observed date-eU patterns (Figures 3–5). These results suggest that the effects of radiation damage and annealing on helium diffusion through the crystal lattice [12] may not be the only control on the observed ZHe dates. As described above, other factors that could possibly influence ZHe dates are crystal size, U and Th zoning in the zircon crystal, and implantation of helium from neighboring grains. Although the effects of zoning and implantation are unknown, for some samples, grain size does seem to be related to ZHe date (Figure 2). Here, we produce refined forward model t-T paths for each location that incorporate possible ZHe date effects related to differences in grain size. For each t-T path, we create three separate date-eU curves using the average grain size±2 standard deviations⁠, based on similar published methods (e.g., [14, 62, 63]). These curves define a date-eU envelope that shows the combined effects of radiation damage and grain size.For the Carrizo Mountains, we use the average grain size of 53±17 μm (±2 standard deviations) to create a date-eU envelope of the best-fit preliminary curve (Figure 6(a)). This t-T path includes cooling to surface temperatures from 1050 to 1000 Ma, early Paleozoic burial to 120°C, exhumation to surface temperatures by 285 Ma, Paleozoic through Mesozoic reheating to a maximum temperature of 170°C at 80 Ma, and a post-Laramide temperature of 60°C before final cooling to surface temperatures. This best-fit t-T path yields a date-eU envelope that encompasses all but the oldest ZHe date.The best-fit forward model for the Franklin Mountains samples uses an average zircon grain size of 43±10 μm to produce a date-eU envelope (Figure 6(b)). This t-T path includes no Proterozoic burial, Paleozoic burial depths to a temperature of 120°C, renewed Mesozoic burial to a maximum temperature of 180°C, post-Laramide residence at a temperature of 60°C, and final uplift to the surface during Rio Grande rift extension. The best-fit t-T path yields a date-eU envelope that encompasses nine of the 18 total ZHe dates. This model fails to account for the oldest as well as the youngest ZHe dates at low eU values. The large spread in ZHe dates from 19 to 402 Ma at eU values <200 ppm suggests that other factors, such as crystal zoning, may also significantly affect ZHe dates in the Franklin Mountains.The best-fit forward model for the Cookes Range uses zircon grain sizes of 46±9 μm (Figure 6(c)). Unlike the other two locations, here, we show the results of three separate best-fit models. Two models involve early cooling, whereas the third model is constant cooling from the time of crystallization. Each of the resulting date-eU envelopes are nearly identical at intermediate and high eU values, but diverge at low eU values where no ZHe dates are available. The resulting best-fit t-T paths encompass nearly all of the observed ZHe dates. However, the yellow and green paths are slightly skewed towards lower eU grains and do not encompass the oldest ZHe date or the three grains at eU values of ~300 ppm. The blue path appears to yield a slightly better fit with the overall ZHe date-eU trend.The forward modelling method described above is successful at finding possible t-T paths that yield date-eU curves that are consistent with the observed data. However, with that approach, it is only feasible to investigate a limited number of possible t-T paths. Here, an inverse modeling approach is used to continue to refine the thermal histories and explore additional possible t-T paths that may have been overlooked during the forward modeling analysis. In this section, we present a single inverse model for each of the three study locations. The inverse models use synthetic grains that represent binned averages of the observed ZHe data. This is necessary because of the large number of individual ZHe dates for each location and the limited number of inputs available in HeFTy. Complete inverse modeling methods and data inputs are provided in Table S1 and Figure S1.The final inverse model for the Carrizo Mountains produced nine paths with a good fit to the input synthetic grains (Figure 7(a)). These paths suggest that after metamorphism, the sample remained at elevated temperatures until rapid uplift at approximately 1035 Ma based on 40Ar/39Ar hornblende and muscovite ages [41]. ZHe data also document the timing of this pulse of exhumation and suggest that the sample was cooled to near-surface temperatures at this time (Figure 7(a)). However, some t-T paths also suggest that the sample could have remained at shallow levels in the crust and was further exhumed to the surface during a second event at approximately 600–500 Ma. Increasing temperatures during Paleozoic sedimentation are not well constrained by the model, as maximum burial temperatures from the nine t-T paths range from 50 to 180°C prior to Ancestral Rocky Mountain uplift which exposed Proterozoic basement to the surface by around 285 Ma. The Mesozoic segment of the inverse model is tightly constrained and suggests that the sample reached maximum temperatures of 150–160°C. Inverse modeling shows minimal cooling associated with the Laramide orogeny, and most paths remain at temperatures >130°C until approximately 30 Ma, when the sample was rapidly cooled to near-surface temperatures.A total of 13 good paths were obtained from inverse modeling of samples collected from the Red Bluff granite (Figure 7(b)). Field relationships suggest that this granite was emplaced at relatively shallow crustal levels, as it intrudes into and cuts an ignimbrite within the Thunderbird Group. These volcanic rocks are interpreted to be the erupted equivalent of the Red Bluff granite, which is supported by geochemical evidence [67] and overlapping geochronologic ages [38]. Inverse models suggest that the Red Bluff granite was then reheated to temperatures ranging from 50 to 250°C. While this large uncertainty likely suggests the ZHe data from the Franklin Mountains may be largely insensitive to the Proterozoic history, the observation that all good paths require some amount of heating is consistent with a model of possible Proterozoic reburial following crystallization. All 13 paths show relatively monotonic reheating throughout the Paleozoic and Mesozoic, and converge within a temperature range of 155–190°C by the time of incipient Laramide deformation. These paths then cool rapidly from approximately 80 to 50 Ma to temperatures less than 100°C. A period of slower cooling is observed beginning at 50 Ma, and by 25–15 Ma, all paths show a final rapid pulse of cooling to surface temperatures.The inverse model for the Cookes Range yielded a total of nine good paths that are consistent with the available geologic constrains and synthetic grains (Figure 7(c)). Following crystallization of this sample, all t-T paths show rather monotonic Proterozoic cooling towards surface temperatures. However, all t-T paths preserve a pulse of more rapid cooling between 800 and 500 Ma that terminated at near-surface temperatures. As with previous inverse models from the Carrizo and Franklin Mountains, the Paleozoic thermal history of this sample is relatively unconstrained. However, the nine paths suggest the sample reached maximum burial temperatures that range from 85 to 180°C prior to Ancestral Rocky Mountain uplift. The uplift history during the Ancestral Rocky Mountain deformational event is also relatively unconstrained, with uplift temperatures ranging from 40 to 165°C. However, during renewed heating during Mesozoic burial, the paths converge to a maximum temperature of 140–180°C. This sample shows a strong component of cooling that is coeval with Laramide deformation. All paths display rapid cooling to lower temperatures of 50–70°C beginning 60–70 Ma and ending by approximately 45 Ma. The sample remained within this temperature range until approximately 25 Ma, when it was cooled to near-surface temperatures.Two Paleozoic detrital samples were collected for ZHe thermochronology from the Cookes Range and the Franklin Mountains. ZHe data from these locations were obtained in order to compare to ZHe data from crystalline basement samples, test whether zircon grains had been reset after deposition, and test for possible influences of magmatism. A total of six ZHe dates were obtained from the Permian Abo Formation from the Cookes Range [25]. Here, the Abo Formation consists of fine- to medium-grained sandstone. An additional seven ZHe dates were obtained from the Cambrian-Ordovician Bliss Sandstone in the Franklin Mountains, including three presented by Biddle et al. [25]. Ideally, more detrital zircon grains would have been selected, but these samples did not yield sufficient zircon grains that were euhedral and of sufficient size.For both samples, we rely on the inverse modeling constraints described above to aid with the construction of inheritance envelopes. To do this, we use the best-fit path from the inverse models as the assumed post-depositional thermal history of the detrital samples (Figure 8). The best-fit path highlighted in red in Figure 8 represents the thermal history used to create the zero inheritance curves. The maximum inheritance curves are created using published detrital zircon U-Pb ages for the Permian Abo Formation and Cambrian-Ordovician Bliss Sandstone in southern New Mexico. Below, we describe each sample in more detail.The Abo Formation in the Cookes Range lies approximately 600 m above the Proterozoic granite based on thicknesses of older Paleozoic units [68]. Assuming a geothermal gradient of 25°C/km, this is equal to a temperature difference of 16°C. This difference is likely minimal in the resulting date-eU curves such that the thermal history of the Proterozoic granite is likely similar to the post-depositional thermal history of the overlying detrital sample. The zero-inheritance date-eU curve that is constructed using the best-fit path from the inverse model is combined with three other maximum inheritance curves to create an inheritance envelope (Figure 8(a)). The maximum inheritance curves use zircon crystallization ages of 1250 Ma, 1465 Ma, and 1785 Ma, based on peaks in U-Pb detrital zircon ages from the Abo Formation in southern New Mexico [69]. When compared with the inheritance envelopes, detrital ZHe dates all fall along the zero-inheritance curve or below the inheritance envelope (Figure 8(a)). If the post-depositional thermal history is correct, then these observations would suggest that the three grains that lie along the zero-inheritance curve could be derived from a ca. 280–300 Ma source. However, probability density plots do not show abundant Paleozoic detrital zircon U-Pb ages [69]. This would also not account for the three ZHe dates that fall below the inheritance envelope. Alternatively, all ZHe detrital grains could be derived from Proterozoic sources if the post-depositional history is modified to include a thermal pulse to partially reset ZHe dates. A granodioritic stock and several basaltic and dacitic dikes and sills with reported K-Ar and 40Ar/39Ar ages that range from 38 to 45 Ma [68, 70, 71] intrude Paleozoic and Mesozoic rocks in the Cookes Range [68], possibly resulting in partial resetting of zircon grains. Partial resetting of detrital ZHe dates from the Abo Formation is also supported by the date-eU plots in Figure 2, where Abo Formation ZHe dates are all younger than the Proterozoic ZHe dates at low eU values.The Bliss Sandstone sample was collected approximately 300 m stratigraphically above the Proterozoic samples used for inverse modeling, suggesting a temperature difference of only 7–8°C, assuming a geothermal gradient of 25°C/km. The best-fit inverse path should therefore be a good approximation of the postdepositional thermal history of the Bliss Sandstone (Figure 8(b)). Maximum inheritance curves were constructed using zircon crystallization ages of 1250 Ma, 1465 Ma, 1625 Ma, 1710 Ma, and 1850 Ma based on U-Pb detrital zircon age probability plots from the Bliss Sandstone in southern New Mexico [72]. The resulting inheritance envelope encompasses all but one ZHe date from the Bliss Sandstone (Figure 8(b)). These observations are consistent with the zircon grains in the Bliss Sandstone in the Franklin Mountains being derived from Proterozoic sources, similar to other regions of southern New Mexico. These results also suggest that the post-depositional t-T path for the Bliss Sandstone (red curve in Figure 8(b)) is a plausible solution for its thermal history.The analysis above incorporates multiple methods to constrain a ZHe date-eU dataset. Southern New Mexico and western Texas have experienced a prolonged and complex tectonic history and, while the ZHe dataset may not be sensitive to all tectonic and sedimentation events, the datasets do constrain parts of the overall history with varying confidence. Below, we first comment on similarities and differences between the forward and inverse modeling methods. We then use the inverse modeling and detrital inheritance curve results to explore the more regional tectonic significance. These results are used to comment on multiple tectonic events in the study area spanning more than a billion years of Earth history.Our modeling approach uses two methods for investigating thermal histories using ZHe date-eU relationships. The forward modeling approach was designed to incrementally narrow the possible thermal history by varying separate segments of the t-T path. This approach was successful at producing best-fit paths for each region that yield date-eU curves that are consistent with the observed ZHe data (Figure 6). However, because the entire thermal history of each region is considered (over a billion years of time), the best-fit paths are inevitably simplistic, allowing for the possibility that additional t-T paths might exist that are also consistent with the data. Our next attempt to constrain each thermal history was to use an inverse model approach to test for this possibility by investigating a total of 50,000 paths per sample, rather than tens of paths with the forward model approach.In the Carrizo Mountains, the best-fit forward model and the inverse modeling paths are similar (Figure 7(a)), although the inverse modeling results allow for more complexity in the sample’s thermal history. For example, the inverse modeling paths suggest that the sample may have remained at shallow depths in the crust from 1000 to 600 Ma, followed by a second pulse of uplift. The inverse modeling paths also allow for a wider range of Paleozoic burial temperatures prior to Ancestral Rocky Mountain uplift. The largest difference between the two modeling results is during 80–40 Ma Laramide deformation. The forward model predicts significant Laramide uplift, followed by a smaller pulse of Rio Grande rift exhumation. The inverse model results, however, suggest that Laramide exhumation was minimal, and much of the final cooling was accomplished within the last 30 Ma (Figure 7(a)).In the Franklin Mountains, the best-fit forward model and the inverse model paths are also similar for most of the thermal history (Figure 7(b)). The biggest inconsistency between the two is from 1000 to 500 Ma, where the best-fit forward model remains at surface temperatures, whereas the inverse model paths all show some amount of reheating prior to Paleozoic deposition. However, both approaches predict similar Mesozoic burial temperatures followed by more recent cooling to surface temperatures.Similar to the other two locations, comparison of forward and inverse modeling results from the Cookes Range also shows the widest discrepancy during the Proterozoic (Figure 7(c)). Whereas our forward modeling analysis yielded multiple Proterozoic cooling paths that are consistent with the observed data, the inverse modeling results are most consistent with steady cooling from 1600 to 500 Ma, rather than earlier pulses of rapid cooling. The inverse models also suggest that the Proterozoic history of this region is more complex than the simplistic forward models, possibly involving multiple pulses of cooling separated by hundreds of millions of years. The Phanerozoic segment of the forward model is consistent with the inverse model results, although the inverse model paths allow for more variability.Overall, the comparison between forward and inverse modeling results is similar at all three locations. However, in instances such as this where the goal is to constrain the entire thermal history from ZHe data, the forward modeling approach is overly simplistic and is unable to explore the full range of possible thermal histories. Thermal histories from these regions are complex and a thorough investigation is not plausible using a forward model approach where tens of paths are investigated. An inverse modeling approach that tests thousands of paths is better equipped to fully explore possible thermal histories in order to more confidently interpret the results. As a result, we will refer to the inverse model results during the remainder of the discussion below.In the Carrizo Mountains, inverse modeling results combined with existing 40Ar/39Ar data [41] suggest rapid cooling to temperatures <150°C at 1030–1000 Ma (Figure 7(a)). This period of cooling is similar to 40Ar/39Ar cooling ages and likely reflects movement along the Streeruwitz thrust during continent-continent collision (Figure 1(b)). All but three of the paths remain at temperatures higher than approximately 75°C until 600 Ma. These results are consistent with sedimentological analyses of the synorogenic Hazel Formation in the footwall of the Streeruwitz thrust. Metavolcanic and metasedimentary clasts derived from the Carrizo Mountain Group are notably absent in the Hazel conglomerate, suggesting that these rocks were most likely not exhumed to the Earth’s surface at this time [73]. Instead, most inverse paths preserve a second pulse of cooling to near-surface temperatures from 600 to 500 Ma (Figure 7), which coincides with the final breakup of Rodinia (Figure 9). Although slightly less constrained, final exhumation in the Franklin Mountains and Cookes Range occurred within a similar timeframe. In the Franklin Mountains, the Red Bluff granite was emplaced at shallow depths and subsequently buried, consistent with geochemical studies of the Red Bluff granite that suggest it formed within an extensional stress field [39]. Good paths for the Franklin Mountains and Cookes Range both preserve a pulse of cooling to near-surface temperatures between approximately 800 and 500 Ma (Figures 7(b) and 7(c)). These results are similar to previous ZHe thermochronologic investigations. DeLucia et al. [14] presented ZHe data and inverse modeling results from the Ozark Plateau of Missouri that document pulses in exhumation from 850 to 680 Ma and 225 to 150 Ma, coinciding with the breakup of Rodinia and the breakup of Pangaea. They suggest a genetic relationship between continental uplift/denudation and the supercontinent cycle that is also observed in rocks from southern New Mexico and western Texas.In southern New Mexico and western Texas, Ancestral Rocky Mountain intracontinental deformation resulted in a series of uplifts and sedimentary basins (e.g., [19]). The sedimentary record preserved in Ancestral Rocky Mountain basins suggests diachronous subsidence histories that young to the west, a pattern that is interpreted to reflect diachronous closure of the Ouachita suture [74]. Within the study area, the Pedregosa and Orogrande basins experienced similar times of peak subsidence rates from approximately 300 to 285 Ma [74]. Inverse models for the Carrizo Mountains and Cookes Range include Paleozoic constraint boxes that allow for a wide range of burial temperatures (50–300°C) from 450 to 290 Ma (Figure 7). Good paths are not sensitive to peak burial temperatures in either model other than they could not have been heated to temperatures >180°C. These paths are also not sensitive to the timing of reheating, with paths reaching peak temperatures from 450 to 300 Ma.These observations suggest that, at least in this study area, ZHe datasets are not sensitive to either the timing or magnitude of Ancestral Rocky Mountain deformation (Figure 9). Instead, ZHe date-eU patterns are largely controlled by the timing and magnitude of both older and younger events that affected the thermal history of these rocks. These observations are useful for possible future studies. In order to investigate burial and exhumation related to the Ancestral Rocky Mountain event using ZHe thermochronology, we suggest either focusing on a location with a less complicated tectonic history so that the date-eU pattern is largely controlled by Ancestral Rocky Mountain deformation or combining ZHe data with additional datasets that constrain either the older or younger tectonic history.Southwestern New Mexico, southeastern Arizona, and northern Sonora, Mexico experienced rifting starting in the Late Jurassic which created the Bisbee basin [48, 49]. The rift basin strata in southern New Mexico reached a maximum thickness of about 2800 m by Albian time [48]. Near the base of the section (TSA1 of Lawton et al., in press), these strata are interlayered with asthenospherically derived mafic volcanic rocks [52]. The strata on the flanks of the basin are much thinner or nonexistent, as the rift shoulder was a topographic high during basin development. The samples from this study were all along the inferred edge of the rift (Lawton et al., in press), but they still could have experienced the elevated geothermal gradients that are common in continental rifts (e.g., [75, 76]). In addition, the injection of mafic magmas into the upper crust in the areas near our study area could have been a factor in conducting heat from the mantle. Gradients in rifts can exceed 60°C/km [77] but can decrease rapidly after extension ends. These elevated geothermal gradients are a likely cause of the maximum temperatures of all three sample locations. In the Bisbee basin, rifting was followed by shortening resulting in the creation of a basin in Albian time dominated by dynamic subsidence in response to arc-continent collision in Mexico (Lawton et al., in press). Thus, geothermal gradients likely reverted to normal values by 100 Ma in the study area.Southern New Mexico and western Texas are at the eastern limit of Laramide deformation. In southern New Mexico, NE-directed shortening produced a series of NW-trending basins and uplifts that range in age from Late Cretaceous to Eocene [22]. Most, if not all, Laramide faults are reactivated normal faults that developed during the formation of the Mexican Border rift [22, 78], and many thrust faults have fault throws that exceed several kilometers (e.g., [79]). Faults and folds related to Laramide shortening follow the Texas-Mexico border towards Big Bend National Park [80]. However, these structures do not extend to the Carrizo Mountains, where Laramide deformation consists of small-amplitude folds and minor thrust faults [81].Laramide magmatism in southwestern New Mexico occurred in several pulses between about 75–70 Ma and 60–55 Ma, and 45–40 Ma [82, 83]. Evidence includes tuffs [82], andesite boulders in basins [84], plutonic rocks such as the Sylvanite complex [79], and various intrusions associated with ore deposits [85]. Our inverse modeling results are designed to include only exhumation and cooling during Laramide uplift, although the nonuniqueness of these models does not preclude some amount of Laramide reheating. In addition to the exposed volcanic and plutonic rocks, deeper Laramide plutons could also have affected ZHe dates. For example, Murray et al. [86] provide numerical models that suggest midcrustal plutons can reset low-temperature thermochronologic ages in upper crustal rocks. This is a result that is not explored here, but could also be a contributing factor in the observed ZHe data.Cooling that is coeval with the Laramide orogeny is preserved in inverse models from the Cookes Range and the Franklin Mountains. In the Cookes Range, paths show a pulse of cooling beginning 60–70 Ma and ending by 45 Ma (Figure 9). The Franklins preserve a similar time of cooling from approximately 80 to 50 Ma. Although scattered Laramide basins in southern New Mexico were present during the Late Cretaceous, the majority of basins and uplifts developed largely during the Paleocene–Eocene [22], overlapping with the inverse models from the Cookes Range and Franklin Mountains. In contrast, the Carrizo Mountains show almost no cooling during this timeframe, and Cenozoic cooling to near-surface temperatures was delayed until after 30 Ma (Figure 9). These observations are consistent with the location of the Carrizo Mountains at the edge of the belt of Laramide shortening where total deformation was minimal.The Neogene Rio Grande rift of southern New Mexico disrupted all previous tectonic elements and imparted the present topographic grain in the landscape. At the latitude of El Paso, Texas, the rift makes a sudden bend and structures south of here trend NW-SE instead of N-S as they do in the central and northern segments of the rift. In Colorado and New Mexico, combined apatite fission-track and apatite (U-Th)/He data suggest that extension was largely synchronous across this region, and these data record a main pulse of cooling from 25 to 10 Ma that is interpreted to reflect extensional exhumation (e.g., [28, 87–89]).Inverse models from all three study locations preserve a pulse of cooling that is coeval with the development of the Rio Grande rift. Rapid cooling began at approximately 25 Ma in the Cookes Range, 25–15 Ma in the Franklin Mountains, and 30 Ma in the Carrizo Mountains (Figure 9). Although this timeframe is only a fraction of the entire thermal history investigated (over a billion years), it seems to have a significant effect on the resulting ZHe date-eU curve at each location. These results are consistent with previously published low-temperature thermochronologic data and modeling from the southern rift that suggest that the southern segment of the rift was active at the same time as the central and northern segments and that cooling of rocks was accomplished through fault exhumation rather than through magmatic injection [28, 87].A total of 55 individual grain ZHe dates are presented from three ranges in southern New Mexico and western Texas. ZHe dates span hundreds of millions of years and record long-term thermal histories of Proterozoic crystalline rocks. These rocks have experienced a prolonged tectonic history involving multiple periods of cooling and reheating. A combination of forward and inverse modeling techniques was used to investigate plausible thermal histories of these samples. We find that although a forward modeling approach is advantageous for quickly comparing several dissimilar thermal histories, an inverse modeling approach can further refine these results and can test tens or hundreds of thousands of possible t-T paths.Our thermal history inverse modeling results lead to the following conclusions: (1) the Red Bluff granite in the Franklin Mountains was likely buried and exhumed prior to deposition of Paleozoic sediments, and the unconformity at this location is therefore a compound erosional surface; (2) Proterozoic exhumation at all three locations occurred between 800 and 500 Ma, coinciding with the break-up of Rodinia; (3) all three study sites record elevated temperatures at approximately 100 Ma that likely reflects elevated heat flow during continental rifting to form the Mesozoic Bisbee basin. These results suggest that elevated heat flow within the rift extended into the rift shoulder, rather than being confined to the rift axis; (4) Laramide cooling occurred from 70 to 45 Ma in the Cookes Range and 80 to 50 Ma in the Franklin Mountains. In contrast, the Carrizo Mountains shows no cooling during Laramide shortening, which likely reflects its location at the edge of observed Laramide deformation; and (5) all three study sites preserve a pulse of cooling that begins at 30–25 Ma, simultaneous with observed cooling in the central and northern segments of the rift.In contrast, these data provide almost no information on the timing or magnitude of Ancestral Rocky Mountain deformation. These data provide important information on the broad thermal history of southern New Mexico and western Texas and highlight the effectiveness of using the ZHe method in tectonically complex regions. These data also help to bridge the gap between lower temperature systems such as apatite (U-Th)/He and fission-track and higher temperature methods of thermochronology such as 40Ar/39Ar.The authors declare that they have no conflicts of interest.JWR was supported by NSF-EAR 1624538 and JMA was supported by NSF-EAR 1624575. ZHe data were obtained from the (U-Th)/He thermochronology lab at CU Boulder. We thank Rebecca Flowers and James Metcalf for their help with data acquisition and discussions and Michelle Gavel for assistance with mineral preparation. Two anonymous reviewers provided very useful feedback that helped improve the quality of this manuscript.Table S1: thermal history model inputs and assumptions for forward and inverse models. Figure S1: description of geologic constraints used in forward and inverse models.

中文翻译：

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锆石（U-Th）/ He对新墨西哥州南部和德克萨斯州西部长期热演化的热年代学约束

锆石（U-Th）/ He（ZHe）日期是从三个范围收集的八个样本（⁠n=55⁠）给出的，这些范围包括德克萨斯州西部的卡里佐山脉和富兰克林山脉以及新墨西哥州南部的库克斯山脉。ZHe起源于Carrizo山脉的6至731 Ma，富兰克林山脉的19至401 Ma，Cookes山脉的63至446 Ma的元古代晶体岩，与eU值呈负相关。这些位置经历了复杂的构造历史，涉及多个隆起和回生时期，并且我们使用正向和反向建模方法的组合来约束可能的热历史。我们最终的反演模型跨越数亿年的历史，并经历了多次构造事件，得出以下结论：（1）生代掘出发生在800至500 Ma，与罗迪尼亚解体相吻合；（2）Bisbee盆地的最终发育过程中出现了大约100 Ma的高温，这可能是大陆裂谷期间上地壳热流升高的结果；（3）在库克山脉从70到45 Ma，在富兰克林山脉从80到50 Ma观察到与拉米酰胺缩短有关的冷却脉冲，而卡里佐山脉在很大程度上不受这一事件的影响；（4）在所有三个地点，最终冷却至近地表温度均始于30-25 Ma，这可能是里奥格兰德裂谷扩展的结果。这些数据有助于弥合高温同位素系统和低温同位素系统之间的鸿沟，以约束构造成熟区域中的复杂热史。热年代学是限制过去地质事件的年龄和持续时间的有力工具，因为发掘会导致冷却，冷却的时间由不同的同位素系统记录。冷却年龄是根据不同矿物的封闭温度（例如，[1]）来解释的，在该温度下，放射源子同位素的扩散在已知温度范围以下会明显减慢。但是，从高温热年代学系统（例如钛铁矿U-Pb，角闪石40Ar / 39Ar和云母40Ar / 39Ar）获得的日期可能会有差距，它们记录了从约600到300°C的冷却时间[2]。 ]，而低温系统（如磷灰石裂变径迹和（U-Th）/ He）分别记录了低于120–60°C和90–30°C的冷却时间[3，4]。使用40Ar / 39Ar系统对钾长石进行多扩散域（MDD）分析[5]可以填补黑云母40Ar / 39Ar与磷灰石（U-Th）/ He之间的温差，尽管已证明在某些情况下存在问题实例（例如[6-8]），而白云母的MDD分析显示出了希望[9，10]。锆石裂变径迹对〜270–210°C的温度敏感[11]，尽管在40Ar / 39Ar方法和磷灰石之间的热年代史上仍然存在差距，但它是一种广泛用于部分填充该温度范围的热力计时表。由于与冷却速率有关的封闭温度的变化，U-Th）/He.Guenthner等人的工作可以克服解密与该间隙相关的热年代史的局限性。[12]，他们描述了一个氦扩散模型，该模型结合了锆石（U-Th）/ He（ZHe）日期与锆石晶体中的辐射损伤积累和退火之间的重要关系。这种关系通常由有时跨越数亿年的内部采样日期表示。对于经历相同热历史的晶粒，ZHe日期的差异由有效铀的差异（⁠eU = U +0.235Th⁠）控制，这些差异反映为ZHe date-eU正负关系。这些关系是由于每种晶粒保留氦气的能力不同而产生的，而该能力取决于eU值。ZHe date-eU的正负趋势是整体热历史的累积结果，以及辐射损伤对氦扩散的影响，这些都可以重建连续的热历史。锆石中的氦扩散模型表明温度敏感度范围约为210至50°C [12，13]，与较高范围的锆石裂变径迹和钾长石40Ar / 39Ar数据以及磷灰石裂变径迹有部分重叠和（U-Th）/ He技术在较低端。较大的ZHe温度敏感度窗口使得可以约束更完整和连续的热历史，从而为弥合较高和较低温度方法之间的差距提供了机会。以前的研究都依赖于此日期内的样本内扩散来研究广泛的地质过程，例如岩石的元古代热史（例如[14]），拉拉胺挖出的时间[15]和南美的发展。被动余量[16]。然而，还需要进一步的研究来进一步评估这种方法的有效性。北美西南部的元古代晶体岩石经历了跨越十亿年的复杂构造历史（例如，[17]）。在新墨西哥州西南部和得克萨斯州西部，这一历史包括但不限于中元古代和新元古代的组装以及超大陆罗丹尼亚的破裂，宾夕法尼亚州-二叠纪祖先的洛基山变形，广泛的古生代和中生代沉积，最新的白垩纪-始新世拉拉酰胺压缩，最后达到与里奥格兰德大裂谷发展有关的新近纪扩展（例如[18-22]）。新墨西哥州元古生代晶体岩石的40Ar / 39Ar冷却年龄通常在1600Ma至1000Ma之间，并反映了陆内构造和成矿作用期间的热脉动（例如[23，24]）。然而，在新墨西哥州同一地区进行的磷灰石裂变径迹和（U-Th）/ He研究表明，它们的年龄通常小于约100 Ma，这反映出与拉拉米德造山运动和里奥格兰德裂谷伸展有关的发掘过程中的降温[25 –28]。这两个不同的数据集每个都提供了更复杂的热历史的简短快照，但是仍然缺乏连续的热记录，尤其是在从约1000 Ma到小于100 Ma的范围内。因此，美国西南部地区是使用ZHe热年代学方法研究长期热史的出色自然实验室。我们介绍了第一个ZHe日期，它来自新墨西哥州南部和德克萨斯州西部的三个山脉：新墨西哥州的库克斯山脉以及德克萨斯州西部的富兰克林山脉和卡里佐山脉（图1）。每个样本的ZHe日期都有显着的样本内ZHe日期变异性，我们使用它来产生一系列正向和反向热历史模型。我们还提供了来自几个碎屑样品的ZHe数据，并讨论了这些数据补充ZHe源自结晶样品的方式。我们的新热历史模型捕获了可以直接与已知地质事件联系在一起的多个冷却和再加热脉冲，并提供了不同的高温40Ar / 39Ar冷却年龄与低温磷灰石裂变径迹和（U-Th）之间的重要联系/ He数据集。最后，我们评估了反向和正向模型的使用，以比较该地区岩石的长期热历史，并确定了ZHe热年代学方法的改进应用。在1.8-1.6 Ga范围内，西南劳伦西亚的古元古代生长是通过逐渐增生的弧形地形，包括亚瓦派和马扎茨尔省[29-31]，其中超大陆罗迪尼亚的最终组装发生在中元古生代晚期的格伦维尔构造运动中（图1）[32]。Laurentia西南部的Grenville造山运动记录了1350至980 Ma之间的弧吸积和大陆-大陆碰撞[33]。在德克萨斯州西部的卡里佐山脉中，一些格伦维尔造山带前陆裸露[33，34]。该ca。1380–1327年，马卡里佐山脉群（图1（b））由未成熟的碎屑岩组成，板块内的流纹质火山岩和少量碳酸盐可能记录了整个辐合过程中后弧盆地内大陆壳的裂谷[35-37]。富兰克林山脉（图1（b））记录了该后弧盆地内大约从加利福尼亚开始持续沉积。1260–1240 Ma [36]直到大陆与大陆碰撞。1150-1120 Ma [36]。在Grenville变形锋以北（图1），富兰克林山脉的岩浆作用由〜1.1 Ga的火山岩和火山岩代表，其中包括Red Bluff花岗岩，该研究针对的是ZHe年代[38，39]。岩石学和地球化学研究将Red Bluff花岗岩分类为板内岩，一个A型花岗岩和一个支持模型，其中这些岩石被放置在一个更区域性的应变场中，该应变场主要由与Nren-SE收敛有关的NW-SE缩短和正交NE-SW扩展控制[39，40]。沿Laurentia南部边缘的最终缩短发生在约1035至980 Ma之间[33，41]。Rodinia破裂的模型表明，历时的逆向分解与早期裂谷发生在780 Ma和680 Ma之间，随后是主要裂谷阶段在620和550之间。马[18，21，42，43]。超大陆破裂可能还伴随着记录在ZHe数据集中的主要剥蚀脉冲[14]。破碎之后，在前寒武纪基底上沉积了古生界被动边缘沉积物（例如[44]），从而形成了巨大不整合面，这是岩石记录中的全球重要特征。在新墨西哥州南部和德克萨斯州西部，大不整合面下的元古代晶体岩石通常由1.45-1.35组成，一些1.1 Ga花岗岩侵入Mazatzal省的1.68-1.65上壳岩[17]。这些岩石通常被寒武纪-奥陶纪极乐砂岩所覆盖，定义了一个严重不整合面，涵盖了600至1000我的失踪时间。北美西部晚期的古生代形变导致了祖先洛矶山脉的发展（例如， [19，45]）。在库克斯山脉（图1）中，从大约320到290 Ma的沉积几乎没有[19]，这表明了洛矶山的祖先变形。相比之下，富兰克林山脉在这段时间内记录了近乎连续的沉积[46]，表明尸体的挖掘很少。在德克萨斯州西部，变形局部剥夺了早古生代沉积岩，露出了元古代的基底，随后被早二叠世岩覆盖[47]。从侏罗纪晚期开始，在索诺拉北部，墨西哥和亚利桑那州南部地区形成了大陆裂谷（例如，[48] ]）。由此产生的裂谷盆地最初被称为比斯比盆地[49]，现在被称为墨西哥边境裂谷（图1）[50]。海相地层中有特提斯化石，表明与墨西哥湾有联系（例如[51]）。镁铁质火山岩和枕形玄武岩等火山成因物质沉积在该裂谷中[52-54]。这项研究的一些样品是从新墨西哥州西南部的北裂谷采集的。根据沉降研究表明，该地区的裂谷以白垩纪中期为终点，表明从与裂谷有关的热沉降过渡到始于阿尔比亚的前陆盆地的形成[50，55]。拉拉米德造山带在东北部发生了晚中生代至始新世的变形。定向的地壳缩短导致一系列隆升和盆地[22]。这些盆地和隆升在新墨西哥州南部向西北延伸，并延伸到墨西哥北部和德克萨斯州西部。我们的Carrizo山研究地点位于Laramide变形的最东端（图1）。这些结构被与里奥格兰德大裂谷发展有关的年轻大陆扩张广泛地剖析[22]。在渐新世开始于新墨西哥州南部的裂谷，开始产生一系列断层隆起和盆地，形成了该地区的现代地形[20]。库克山脉（Cookes Range）由与里奥格兰德大裂谷发育有关的正断层在三个方面界定，富兰克林山脉和卡里佐山脉均与活跃的正断层有关，这些断层记录了该地区的持续变形。诸如卡里佐山脉，富兰克林山脉和库克斯山脉等，暴露出了新生代晶体基底，该基底已被挖掘到新生代正断层下盘的表面。从晶体基底岩石和碎屑粗粒砂岩或粒状砾岩沉积岩中收集样品，因为它们可能含有丰富的锆石晶体。另外，以样品位置为目标，以避免渐新世广泛的胶体作用的可能影响。沿新墨西哥州南部的EW断面收集的样本表明，距离西部较远的许多样本已被完全重置，并且所有ZHe日期均为渐新世-中新世[25，56，57]。这些研究发现，沿着该EW断面，库克斯山脉是保存较旧ZHe日期的最西端位置，尽管它确实包含渐新世侵入岩和挤出岩（图1（b）），可能部分影响了ZHe数据（如详情请见下文）。因此，选择了库克斯山脉以东及包括该山脉的山脉，因为它们已从渐新世岩浆作用的影响中移除，并且可能保留了较长期的长期热史记录。使用标准的矿物分离技术对整个岩石样品进行处理，以分离出锆石馏分。用配备有用于测量谷物尺寸（包括长度，宽度和深度）的数码相机的岩相显微镜检查锆石分离物。适用于ZHe热年代学的理想锆石晶体是平整的，没有夹杂物，最小直径为70μm。从每个样本中挑选出五到十个最佳锆石，并装入Nb管中进行分析。所有样品均在CU Boulder（CU TRaIL）的热年代学研究与仪器实验室进行了分析。由于所有样品均产生一定范围的ZHe日期和eU值，因此首先使用正向建模方法来约束每个山脉的长期热历史自样品结晶以来的范围。正向建模允许使用氦扩散或退火动力学从确定的时间-温度路径计算热计时年龄[58]。根据已知的地质约束条件研究了多个假想的时间-温度路径，包括大不整合面的形成，古生代和中生代沉积期以及在祖先洛矶山，拉拉米德和里奥格兰德裂谷变形事件期间可能的掘出（表S1，图S1）。对于这些路径中的每条路径，我们都会改变在样品热历史的不同阶段所达到的最高或最低温度。使用Matlab脚本（Guenthner，pers。comm。，2018）从每个tT路径计算出zHe date-eU曲线，该脚本结合了Guenthner等人的锆石辐射损伤累积和退火模型（ZRDAAM）。[12]。输入内容包括特定的时间-温度路径，锆石eU值和锆石晶粒尺寸。然后将这些date-eU路径与ZHe数据进行比较。与观测数据大不相同的模型日期-欧洲单位路径不是可行的热历史。通过改变热历史的不同段，每个样本的模型日期-eU路径将进行增量调整，以提供一定范围的允许热历史。该方法假设对ZHe的唯一控制是氦扩散，该扩散与晶体损伤和随时间演变的退火有关。但是，ZHe年代的扩散也可能受到其他因素的影响，例如晶体大小，锆石晶体中的U和Th分区以及从相邻晶粒中注入氦气（例如[59-61]）。尽管通常不知道可能的He植入，并且在ZHe研究中通常无法获得分区信息，因此可以研究晶体尺寸对所得date-eU曲线的影响。为此，我们使用与其他工作人员类似的方法（例如[14，62，63]），其中对三个单独的date-eU曲线进行建模以创建一个应该包含ZHe日期的信封。要创建三个曲线，我们使用平均晶粒度±2标准偏差⁠。我们还使用逆模型来进一步细化可能的热历史。正向建模用于测试数十条可能的路径，而逆向建模方法可以测试数以万计的可能路径，并探索ZHe数据允许的其他可能的tT路径。逆建模允许计算tT路径，该路径将测得的测温年龄与指定的统计误差相匹配[58]。我们使用HeFTy v。1.9.3 [4]，该方法使用蒙特卡洛方法根据输入的数据绘制可能的时间-温度路径。HeFTy中的输入数据包括U，Th，Sm浓度，晶粒半径，测得的年龄和年龄不确定性。HeFTy需要用于建模的一组温度时间参数，例如开始时间，结束时间和温度。所有逆模型都探索了总共50,000条路径，其中得到的“可接受”路径的拟合优度参数> 0.05，而“良好”路径的拟合优度标准> 0.5。表S1和图S1中提供了完整的模型约束和输入，并遵循Flowers等人中概述的方法。[64]。最后，我们探索从库克斯山脉和富兰克林山脉采集的样品中碎屑状ZHe的重要性。与火成岩样品相比，部分重置的碎屑锆石晶粒仅具有共同的沉积后热历史，但是每个晶粒仍可能保留较旧的独特热烙印。因此，它们不必一定沿着单一的date-eU曲线摆放，而应该具有潜在的高度可变的ZHe日期[15]。碎屑颗粒的分析需要按照Reiners等人（2008年）中概述的方法为每个位置构建继承包络。[65]和Guenthner等。[15]。继承包络是通过将零继承date-eU曲线与假定具有不同锆石结晶年龄的多个最大继承曲线相结合而创建的。零继承日期-eU曲线是根据热史建立的，该热史始于碎屑样品的沉积年龄，并假设当时没有遗传的辐射损伤，这种情况可以通过在沉积时完全重置碎屑晶粒或在沉积时将U-Pb年龄设为零来实现。最大继承曲线通过假设锆石在沉积年龄之前在表面温度下结晶而合并了遗传辐射损伤的影响。然后这些颗粒在沉积后与零继承曲线具有相同的热历史。如果tT路径是样品热历史的合理结果，则这些不同的曲线组合在一起便会得到一个继承包络，其中应包含观察到的ZHe日期。总共显示了37个新的ZHe日期，包括10个来自Carrizo山的日期，20个日期来自富兰克林山脉，七个日期来自库克斯山脉。这些与之前报道的18个ZHe日期结合在一起[25，56]，包括来自富兰克林山脉的九个日期和来自库克斯山脉的九个日期（图2）。该项目总共包含来自八个样本的55个单独的ZHe年代，以研究跨越亿万年的长期热史的模式（表1）。来自两个样本的十个ZHe年代是从该地区的中元古代Hackett峰组获得的。北部卡里佐山脉的卡里佐山脉群（图1（b）和2，表1）。这些数据显示，在ZHe年代（6-731 Ma）和eU浓度（52-1729 ppm）中，变化很大。还有一个明确定义的ZHe date-eU负相关性，显示出陡峭的趋势，直到eU值约为400 ppm。这些日期与籽粒半径显示出轻微的正相关。最早的日期对应最大的谷物，这表明可能对ZHe日期进行粒度控制。从富兰克林山的中元古代红布拉夫花岗岩和寒武纪-奥陶纪极乐砂岩中获得了四个样品的29个ZHe日期（图1（b）和2）。ZRed布拉德布拉夫花岗岩的日期范围从19到401 Ma。它们的eU浓度也显示出很大的范围，范围从63至828 ppm。这些数据加在一起，虽然定义不明确，但其ZHe date-eU相关性略有负数，其中较旧的ZHe日期通常对应于较低的eU值。但是，富兰克林山脉的个别样本并不总是呈负趋势，有些（17FR03）则呈平缓趋势。来自富兰克林山脉的大多数结晶锆石晶粒聚集在35-55μm的狭窄尺寸范围内，因此未观察到ZHe枣粒尺寸趋势。来自极乐砂岩的ZHe日期显示ZHe日期范围为62–649 Ma，eU浓度范围为90至374 ppm。这些ZHe日期中有许多比晶体基底样品中的ZHe日期更早，并且一起定义了负趋势日期-eU趋势。该样品显示出的晶粒尺寸范围比晶粒大得多，在晶粒中大多数晶粒更老，更大。但是，随着较大晶体的出现，ZHe的日期似乎没有增加。在Cookes范围内总共显示了16个ZHe的日期（图1（b）和2）。十个ZHe年代是从沿Cookes山脉南缘Rattlesnake Ridge暴露的元古代花岗岩中提取的。这些ZHe日期范围从63到446 Ma，eU范围为232–945 ppm。这些数据显示，在较低eU值下，ZHe数据与eU呈负的负相关关系，在较高eU值下则转换为较平坦的趋势。从库克斯山脉的二叠纪Abo组获得了另外六个ZHe日期。ZHe日期范围从44到130 Ma，相应的eU值从56到351 ppm。尽管此样本产生的eU范围不大，但是这些ZHe日期具有轻微的负趋势，其中ZHe日期越旧对应的eU值越低。与富兰克林山脉的样品相反，库克斯山脉的碎屑颗粒比晶状锆石颗粒年轻。单个ZHe日期似乎没有显示出明确的晶粒尺寸趋势。为两个目的在每个位置构造了晶体样品的假想时间-温度路径（图3-5）。首先，这些路径用于消除与观测到的ZHe日期不兼容的热历史，并开始细化可能的热历史。其次，这些路径用于测试哪个时期的埋葬或隆升对产生的ZHe date-eU模式影响最大，哪些事件影响相对较小。为此，我们使用了Matlab例程，其中包含了Guenthner等人的锆石辐射损伤累积和退火模型（ZRDAAM）。[12]。正向模型输出是根据输入数据预测的Zhe date-eU曲线。通过改变该地区不同变形事件的埋葬或挖掘出的数量，为每个山脉构建了假想的时间-温度路径。表S1和图S1提供了每个位置的特定地质约束。然后将根据输入时间-温度计算出的每条ZHe日期-eU曲线与从每个位置收集的ZHe数据进行比较。下面，我们首先介绍三个研究地点中每个地点的初步正向模型。然后，我们对这些结果进行优化，并生成最合适的模型，这些模型代表与通过此方法获取的观测数据最匹配的模型。为卡里佐山脉构建了四组代表性tT路径，每条路径均不同的历史段。第一组代表性路径在沉积古生界之前改变了元古代掘出的时间（图3（a））。考察了三种可能的热历史，以测试ZHe数据对元古代掘出的敏感性。这三个路径均在1035 Ma时在500至350°C的温度范围内冷却，这与40Ar / 39Ar角闪石和白云母数据一致[41]。从那里开始，它们发散，包括在1000 Ma时早期发掘到15°C（蓝色路径），从800到700Ma中部挖掘从300到15°C（蓝宝石路径）和从600时300°C到15°C的晚期挖掘物。到500 Ma（黄色路径）（图3（a））。这些路径的500 Ma后段是相同的。这三个路径各自产生的date-eU曲线与其他路径明显不同，这表明元古代的冷却历史对所得的日期-电子单位关系产生了重大影响。在提出的三种降温方案中，从1050到1000 Ma的表面快速发掘可以预测出最大的ZHe日期，与观察到的日期相似，尽管它与数据的负斜率不匹配。但是，该结果支持快速冷却，然后在地球表面长时间停留。第二组代表性路径是通过使用图3（a）的1050–1000 Ma掘尸程序建立的第一轮迭代。在这里，我们在形成极大不整合面之后改变了最大的古生代埋葬深度（表S1，图3（b）和图S1）。考察了八种热史，它们将最高埋葬温度在325 Ma下从110升高到180°C，表示在落基山祖先隆起之前的最大埋葬次数。生成的ZHe date-eU模式的宽度略有变化，但是最大ZHe年龄存在较大的变化。但是，小于140°C的最大埋葬深度都产生几乎相同的date-eU路径，这表明该数据集对较低温度不敏感。建模的110-140°C的eE路径预测的最大ZHe日期与观测数据最为相似。第三组代表性路径结合了1050-1000 Ma的元古代冷却，并使用了120°C的古生代最高埋藏温度。该迭代改变了祖先洛矶山隆起后的中生代埋葬深度（表S1；图S1）。检查了八种热历史，这些热历史在80 Ma下将最大深度从130改变为200°C（图3（c））。这些tT路径生成的date-eU曲线的最大ZHe日期和宽度范围很大。与观察到的数据进行比较时，在匹配最旧的ZHe日期和匹配数据的负date-eU斜率之间需要权衡。例如，温度为160°C时预测与记录的数据相匹配的最古老的ZHe日期，而温度为170-180°C时则预测紧随数据的负斜率。在计算出的date-eU曲线中，最大的中生代埋藏深度为170°C，给出的预测曲线与观测数据中陡峭的date-eU负斜率以及弯折变为更浅趋势的扭结相匹配。最后一组代表性路径的构建是为了改变从拉拉米德起酥油相关隆升到里奥格兰德裂谷伸展隆升的过渡。去做这个，在拉拉米德隆升之后和里奥格兰德裂谷隆升之前，我们改变了样品驻留的温度（图3（d））。检查了八种热历史，这些历史在60到130°C之间使温度从40 Ma变到30 Ma。所有的路径都几乎相同，这表明整个ZHe date-eU模式对Carrizo山脉的这种年轻的变形事件不那么敏感.Franklin山脉的新近纪断裂和倾斜使该地区东部基部的元古代花岗岩暴露（图1（b））。从该范围的不同地点收集了总共三份来自富兰克林山的元古代样品。尽管它们都是从相似的海拔高度收集的，但在“大不整合面”下方每个样品的计算深度有所不同。例如，尽管样品15FR03和17FR03分别位于古深度361 m和229 m，但样品17FR04却位于大约1587 m的更大深度处。出于建模目的，将样品15FR03和17FR03合并为一个样品，因为它们可能经历了几乎相同的热历史，并且这些晶粒在一起显示的eU值范围更大，从而允许对热历史进行更严格的约束。排除了来自样品17FR04的ZHe日期，并且未尝试对此样品进行建模，部分原因是因为该样品仅具有四个eHe值分布有限的ZHe日期（图2，表1）。为富兰克林山脉而建（图4）。按日期-eU曲线变异性递减的顺序显示了这四组路径。例如，中生代的埋藏日期-eU曲线在最大ZHe日期和陡峭负趋势的位置方面变化很大，而不同的元古代路径对日期-eU曲线影响很小。在白垩纪区域隆升停止后，构造了第一组代表性路径以改变中生代的埋葬量（图4（a））。检查了八条路径，这些路径在80 Ma下将最高埋葬温度在80到220°C之间变化，这表示在拉拉米德隆起之前的最高埋葬温度。这些路径会产生具有明显差异的date-eU曲线。这些曲线之间最显着的差异是最大的ZHe日期和负斜率的位置，这表明路径的这一部分对最终的ZHe date-eU曲线有重大影响。在8条建议的tT路径中，将其埋藏到180°C时会产生一条日期-eU曲线，该曲线与所观察到的数据非常吻合。第二组代表性路径被构造为在严重不整合之后改变古生代埋葬的数量。这条路径包括250至150 Ma的恒温期，因为在富兰克林山脉中，下白垩纪岩石不整合地覆盖在二叠纪岩石上，表明没有沉积期[66]。检查了八种热历史，这些历史在40到180°C之间将最大埋葬温度从250 Ma改变到150 Ma（图4（b））。选择最低温度40°C代表最小的古生代墓葬，选择最高温度180°C，因为它接近ZHe温度敏感性窗口的高端。结果eU曲线在eU值大于400 ppm时相似。在较低的值，曲线在不同的ZHe日期发生分歧形成峰。尽管多个最终的date-eU曲线大致与观测到的ZHe日期相匹配，但中等埋葬温度为120°C时会产生一条将数据二等分的曲线。 4（c））。检查了八种可能的热历史，这些热历史在40 Ma时在40至180°C的拉拉酰胺后温度之间变化。较高的埋葬温度会产生几乎平坦的date-eU曲线。埋藏温度低于约120°C时，曲线几乎没有变化，但是这些曲线预测最古老的ZHe日期与观测数据更加吻合。选择60°C的温度是因为它会产生最高ZHe峰的曲线。在最后的迭代中，检查了元古代的热历史（图4（d））。结晶后不久，所有可能的路径都被迫接近地表温度，这是因为Red Bluff花岗岩在某些位置侵入了上覆的雷鸟流纹岩，表明它被放置在地壳的浅层。从这里开始，检查了八种不同的路径，这些路径假定可能是Red Bluff花岗岩被埋藏，然后在古生代地层沉积之前被挖掘回地面。最高埋葬温度为15至200°C。此外，还研究了两种不同的发掘时间，包括800至750 Ma的发掘和650至550 Ma的发掘。这些不同的tT路径使预测的date-eU曲线几乎没有变化，这表明所观察到的ZHe date-eU值不受这些样品的元古代热历史的强烈影响。这与观测到的ZHe日期相吻合，这些日期大多小于250 Ma，为Cookes Range构建了四组代表性路径。构造第一套路径是为了在严重不整合之后改变古生代的埋葬数量。考察了八种热史，这些史将最大埋葬深度改变为325 Ma下60至200°C的温度范围，这表明在落基山隆起之前最大的埋葬（图5（a））。较高的温度tT路径会在中间eU值处产生具有明显平整的date-eU曲线。随着较低的埋葬温度，这种山墙饰消失了。尽管观察到的Zhe date-eU关系没有显示出这种沉淀，较高的埋藏温度提供了更好的匹配度，因为最大的ZHe日期与观测到的日期相似，而较低的埋藏温度则预测ZHe日期早于1000 Ma。第二组路径用于改变先祖落基山之后的中生代埋葬量隆起。这些路径使用了160°C的古生代埋藏温度限制（图5（a））。检查了八种热历史，这些历史使温度在60到200°C之间变化（图5（b））。所得的date-eU曲线显示出巨大的可变性。在较低的埋葬温度下，观察到了明显的沉积物，尽管该沉积物在较高的温度下逐渐消失。中生代的埋葬温度为160°C时，会生成一条沿观测到的ZHe日期路径的date-eU曲线，并在中等和较高eU值（200-1000 ppm）下捕获宽大的date-eU模式。在第三次迭代中，古生代中生代的埋藏温度保持在160°C，从拉拉米特缩短到里奥格兰德大裂谷的伸展隆升的转变从20到160°C不等（图5（c））。较低的20–120°C温度会产生几乎相同的date-eU曲线。最高温度160°C预测最古老的ZHe日期太年轻而无法与观察到的数据相匹配。由于较低的温度似乎对所得的date-eU模式不敏感，因此80°C的温度紧随观察到的日期，并用于最终迭代中。前三个迭代用于约束tT历史的生代时代段，而元古代隆升历史则有所不同（图5（d））。评估了五种可能的历史，这些历史改变了掘尸到地面的时间。在eU值大于250 ppm时，早期冷却或恒定冷却的三个路径几乎相同。值较低时，它们会发散。涉及不到1000 Ma的快速冷却的tT路径会产生明显宽广的date-eU模式。三种早期降温方案产生的date-eU曲线与观测到的ZHe date-eU趋势相似。这三个date-eU曲线之间的唯一显着差异是预测的最大ZHe日期。但是，在这些路径发生分歧的地方，没有eU值低于200 ppm的ZHe晶粒可用。以上分析为解释ZHe数据集提供了有用的指导。对于所有三个位置，最终的正向模型都是不唯一的，因此，我们改进热历史的方法只能设法从多个路径中产生一条tT路径。但是，这种方法的确突出了日期eU曲线对tT历史的哪些段最敏感。例如，在所有三个位置，改变中生代埋葬的规模都会对生成的date-eU曲线产生巨大影响。在卡里佐山脉和库克斯山脉，元古代掘出的时间也会产生显示出显着差异的date-eU曲线。相比之下，在所有三个位置上，拉拉酰胺后/里奥格兰德前裂谷温度似乎并未显着影响date-eU曲线。该分析强调了正向建模技术的某些用途，用于了解哪些事件可能保留在热记录中以及哪些事件对数据不敏感。下面，我们使用这些结果并结合晶粒尺寸的可能影响，以生成最合适的正向模型。上面的初步正向建模工作未能产生一条与所观察到的date-eU模式充分吻合的tT路径（图3– 5）。这些结果表明，辐射损伤和退火对氦气通过晶格扩散的影响[12]可能不是观察到的ZHe日期的唯一控制。如上所述，可能影响ZHe日期的其他因素是晶体大小，锆石晶体中的U和Th分区以及从相邻晶粒中注入氦气。尽管分区和注入的影响尚不清楚，但对于某些样品，晶粒尺寸似乎确实与ZHe的日期有关（图2）。在这里，我们为每个位置生成了改进的前向模型tT路径，其中包含了与晶粒尺寸差异有关的可能的ZHe日期效应。对于每个tT路径，我们基于类似的公开方法（例如[14、62、63]），使用平均晶粒尺寸±2标准偏差⁠创建三个独立的date-eU曲线。这些曲线定义了一个date-eU包络线，它显示了辐射损伤和晶粒尺寸的综合影响。对于Carrizo山脉，我们使用53±17μm的平均晶粒尺寸（±2个标准偏差）来创建一个date-eU包络线。最佳拟合初步曲线（图6（a））。此tT路径包括冷却至1050至1000 Ma的表面温度，早古生代埋葬至120°C，到285 Ma时被掘回至地表温度，中生代通过在80 Ma时再加热至170°C的最高温度来进行古生代，以及在最终冷却至表面温度之前的拉拉酰胺后温度为60°C。这条最适合的tT路径产生的date-eU包络涵盖了除最古老的ZHe日期以外的所有日期。富兰克林山脉样本的最适合正向模型使用43±10μm的平均锆石粒度生成date-eU包络（图6（b））。此tT路径不包括元古代的埋葬，古生代的埋葬深度达到120°C，中生代的新埋葬到最高温度180°C，拉拉酰胺在60°C的温度下停留以及在此过程中最终抬升至地面里约格兰德裂谷扩展。最佳拟合tT路径产生的date-eU信封包含18个全部ZHe日期中的9个。此模型无法说明eU值较低的最老和最年轻的ZHe日期。当eU值<200 ppm时，ZHe的大范围扩散发生在19-402 Ma之间，这表明其他因素（例如晶体分区）也可能会显着影响富兰克林山脉的ZHe发生日期。库克斯山脉的最佳正向模型使用锆石晶粒尺寸为46±9μm（图6（c））。与其他两个位置不同，我们在这里显示三个单独的最佳拟合模型的结果。两种模型都涉及早期冷却，而第三种模型是从结晶开始就持续冷却。每个得到的date-eU信封在中高eU值时几乎相同，但在低eU值（没有可用的ZHe日期）时发散。最终的最佳拟合tT路径涵盖了几乎所有观测到的ZHe日期。然而，黄色和绿色路径稍微偏向较低的eU晶粒，并且不包含最古老的ZHe日期或eU值为〜300 ppm的三个晶粒。蓝色的路径似乎与ZHE date-eU的总体趋势略有契合。上述正向建模方法成功地找到了可能的tT路径，这些路径产生了与观测数据一致的date-eU曲线。但是，使用该方法，仅可行的方法是研究有限数量的可能的tT路径。在这里，使用逆建模方法来继续完善热历史并探索在正向建模分析过程中可能已被忽略的其他可能的tT路径。在本节中，我们为三个研究位置中的每个位置提供一个逆模型。逆模型使用合成颗粒，代表观察到的ZHe数据的装箱平均值。这是必需的，因为每个位置的大量ZHe日期大量且HeFTy中可用的输入数量有限。表S1和图S1提供了完整的逆建模方法和数据输入。卡里索山脉的最终逆模型产生了九条路径，这些路径与输入的合成谷物非常吻合（图7（a））。这些路径表明，在变质后，基于40Ar / 39Ar角闪石和白云母的年龄，样品一直处于升高的温度，直到在1035 Ma处迅速隆升[41]。ZHe数据还记录了该掘尸脉冲的时间，并建议此时将样品冷却至近地表温度（图7（a））。然而，一些tT路径也表明，样品可能保留在地壳中的浅层，并在大约600-500 Ma的第二次事件中被进一步挖掘到地表。该模型没有很好地限制古生代沉积过程中温度的升高，因为在落基山隆起之前，九个tT路径的最高埋藏温度范围为50至180°C，这使元古代的基底暴露于地表约285 Ma。逆模型的中生代部分受到严格约束，表明样品达到了150-160°C的最高温度。逆向模型显示与Laramide造山带有关的冷却降到最低，并且当样品迅速冷却到近地表温度时，大多数路径保持在> 130°C直到大约30 Ma。从Red Bluff花岗岩收集的样品的逆向建模中，总共获得了13条好的路径（图7（b））。田间关系表明，该花岗岩被侵入并切入雷鸟集团内部的一个火成岩时，被置于相对浅的地壳水平上。这些火山岩被解释为与Red Bluff花岗岩的喷发等效，这由地球化学证据[67]和重叠的年代学年龄[38]来支持。反模型表明，Red Bluff花岗岩随后被重新加热到50至250°C的温度。尽管这种巨大的不确定性可能暗示富兰克林山脉的ZHe数据可能对元古代历史不太敏感，所有好的路径都需要加热的观察结果与结晶后可能的元古代回生的模型一致。所有13条路径在整个古生代和中生代都表现出相对单调的再加热，并且在拉曼酰胺发生初始变形时收敛在155-190°C的温度范围内。这些路径然后从大约80 Ma迅速冷却到50 Ma，直到温度低于100°C。从50 Ma开始观察到一段较慢的冷却时间，到25-15 Ma，所有路径都显示出最终快速冷却到表面温度的脉动。库克斯山脉的逆模型产生了总共9条与现有的地质约束和合成晶粒（图7（c））。该样品结晶后，所有的tT路径都显示出对表面温度相当单调的元古代冷却。但是，所有的tT路径都保留了在800至500 Ma之间更快冷却的脉冲，该脉冲终止于近地表温度。与以前来自卡里佐（Carrizo）和富兰克林（Franklin）山脉的逆模型一样，该样品的古生代热史相对不受限制。但是，这九条路径表明，在落基山隆起之前，样品达到的最高埋葬温度范围为85至180°C。祖先洛矶山变形事件期间的隆升历史也相对不受限制，隆升温度范围为40至165°C。但是，在中生代埋葬期间重新加热时，路径会收敛到最高温度140–180°C。该样品显示出与Laramide变形同时存在的强大的冷却成分。所有路径均显示出快速冷却至50-70°C的较低温度，开始于60-70 Ma，结束于大约45 Ma。样品冷却至近地表温度之前一直保持在该温度范围内，直到大约25 Ma。从库克斯山脉和富兰克林山脉收集了两个古生代碎屑样品用于ZHe热年代学。从这些位置获得的ZHe数据是为了与晶体基底样品的ZHe数据进行比较，测试锆石颗粒在沉积后是否已重置，并测试岩浆作用的可能影响。从库克斯山脉[25]的二叠纪阿波组总共获得了6个ZHe枣。在这里，阿博地层由细至中粒度的砂岩组成。从富兰克林山脉的寒武纪-奥陶纪极乐砂岩中获得了另外七个ZHe日期，其中Biddle等人提出了三个。[25]。理想情况下，应该选择更多的碎屑锆石晶粒，但这些样品不能产生足够的正方面体和足够大小的锆石晶粒。对于这两个样品，我们都依赖于上述逆建模约束来帮助构造继承包络。为此，我们使用逆模型中的最佳拟合路径作为碎屑样本的沉积后热历史假设（图8）。图8中红色突出显示的最佳拟合路径表示用于创建零继承曲线的热历史。使用已发布的新墨西哥州南部二叠系Abo组和寒武纪-奥陶纪极乐砂岩的碎屑锆石U-Pb年龄来创建最大继承曲线。下面，我们将更详细地描述每个样品。基于较旧的古生代单元的厚度，库克斯山脉的Abo地层位于元古代花岗岩上方约600 m处[68]。假设地热梯度为25°C / km，则等于16°C的温差。这种差异在生成的date-eU曲线中可能很小，因此，元古代花岗岩的热史可能与上覆碎屑样品的沉积后热史相似。使用逆模型中的最佳拟合路径构造的零继承日期eU曲线与其他三个最大继承曲线合并以创建继承包络（图8（a））。基于新墨西哥州南部Abo组U-Pb碎屑锆石年龄的峰值，最大继承曲线使用1250 Ma，1465 Ma和1785 Ma的锆石结晶年龄[69]。与继承信封相比，碎屑ZHe日期全部沿零继承曲线下降或低于继承信封（图8（a））。如果沉积后的热历史是正确的，那么这些观察结果将表明，沿着零继承曲线分布的三个晶粒可以从一个ca得出。280–300 Ma的源。然而，概率密度图未显示丰富的古生代碎屑锆石U-Pb年龄[69]。这也不会考虑低于继承范围的三个ZHe日期。或者，如果将沉积后的历史记录修改为包括热脉冲以部分重置ZHe日期，则所有ZHe碎屑颗粒都可以来源于元古代。据报道，K-Ar和40Ar / 39Ar年龄范围从38Ma到45Ma [68，70，71]的一个古生物种群和几个玄武和大堤堤和基岩侵入库克斯山脉[68]的古生代和中生代岩石。在部分重置锆石。图2中的date-eU图也支持了Abo组碎屑ZHe日期的部分复位，其中在低eU值下，Abo组ZHe日期都比元古代ZHe日期年轻。Bliss砂岩样品是在地层以上大约300 m地层上收集的，用于反演，其元古代温度假设为25°C / km，表明温差仅为7-8°C。因此，最佳拟合的反向路径应与Bliss砂岩的沉积后热历史（图8（b））近似。根据新墨西哥州南部Bliss砂岩的U-Pb碎屑锆石年龄概率图，使用1250 Ma，1465 Ma，1625 Ma，1710 Ma和1850 Ma的锆石结晶年龄绘制了最大继承曲线。[72] 由此产生的继承包络涵盖了极乐砂岩中除一个日期外的所有ZHe日期（图8（b））。这些观察结果与富兰克林山的极乐砂岩中的锆石晶粒与新墨西哥州南部的其他地区类似，这些锆石晶粒来源于元古代。这些结果还表明，Bliss砂岩的沉积后tT路径（图8（b）中的红色曲线）是其热历史的合理解决方案。以上分析结合了多种方法来约束ZHe date-eU数据集。新墨西哥州南部和得克萨斯州西部经历了漫长而复杂的构造历史，尽管ZHe数据集可能对所有构造和沉积事件都不敏感，但这些数据集确实以不同的置信度约束了整个历史的一部分。下面，我们首先对正向和反向建模方法之间的异同进行评论。然后，我们使用反演模型和碎屑继承曲线结果来探索更多区域性的构造意义。这些结果用于评论研究区域中超过10亿年的地球历史的多个构造事件。我们的建模方法使用两种方法通过ZHe date-eU关系调查热史。设计正向建模方法是通过改变tT路径的各个不同部分来逐渐缩小可能的热历史。该方法成功地为每个区域生成了最佳拟合路径，从而产生了与观测到的ZHe数据一致的date-eU曲线（图6）。但是，由于考虑了每个区域的整个热历史（超过十亿年的时间），因此最佳拟合路径不可避免地会变得简单，考虑到可能存在与数据一致的其他tT路径。我们限制每个热历史的下一个尝试是使用反模型方法来测试这种可能性，方法是调查每个样本总共50,000条路径，而不是使用正向模型方法研究数十条路径。正向模型和逆向建模路径相似（图7（a）），尽管逆向建模结果使样品的热历史更加复杂。例如，反向建模路径表明样品可能已保留在地壳的浅层深度（从1000 Ma到600 Ma），然后是第二个隆升脉冲。逆建模路径还允许在祖先洛矶山隆起之前有较广泛的古生代埋藏温度。两种模拟结果之间的最大差异是在80–40 Ma Laramide变形期间。前向模型预测，Laramide会显着抬升，随后Rio Grande裂谷发掘出较小的脉动。然而，反演模型的结果表明，Laramide的发掘很少，并且最后的冷却大部分都在最后30 Ma内完成（图7（a））。在富兰克林山脉，最佳拟合正演模型和反演模型大多数热历史过程中的路径也相似（图7（b））。两者之间最大的不一致性是从1000到500 Ma，其中最适合的正向模型保持在地表温度，而反向模型路径都显示出在古生代沉积之前一定程度的重新加热。然而，两种方法都可以预测相似的中生代埋藏温度，然后再降温到地表温度。与其他两个位置类似，库克斯山脉正反模型结果的比较也表明，元古代存在最大的差异（图7（c））。尽管我们的正向建模分析产生了与观测数据一致的多个元古代冷却路径，但逆向建模结果与从1600到500 Ma的稳定冷却最一致，而不是较早的快速冷却脉冲。反演模型还表明，该地区的元古代历史比简单的正演模型更为复杂，可能涉及到由数亿年分隔的多个冷却脉冲。尽管反向模型路径允许更多的可变性，但正向模型的Phanerozoic段与反向模型的结果一致。总的来说，正向和反向建模结果之间的比较在所有三个位置都是相似的。但是，在这种情况下（例如，目标是从ZHe数据中限制整个热历史），正向建模方法过于简单，无法探索所有可能的热历史。这些区域的热历史很复杂，使用正向模型方法（其中研究了数十条路径），无法进行全面的研究。测试数千条路径的逆建模方法可以更好地装备以充分探究可能的热历史，以便更自信地解释结果。结果是，在下面的其余讨论中，我们将参考反模型结果。在卡里佐山脉中，反模型结果与现有40Ar / 39Ar数据[41]相结合，表明在1030–1000 Ma时温度迅速降至<150°C（图7（a））。这个冷却期类似于40Ar / 39Ar的冷却年龄，并且可能反映了大陆-大陆碰撞期间沿Streeruwitz推力的运动（图1（b））。除三个路径外，所有路径均保持在高于约75°C的温度下直至600 Ma。这些结果与Streeruwitz逆冲推力下盘的协同成因的榛树形成的沉积学分析一致。在榛树集团中，明显没有来自Carrizo山脉的变火山岩和沉积沉积岩屑，这表明这些岩石目前很可能没有被挖掘到地球表面[73]。取而代之的是，大多数反向路径都将第二次冷却脉冲保留到近地表温度600至500 Ma（图7），这与罗迪尼亚的最终破裂相吻合（图9）。尽管受约束的程度稍有减少，但在富兰克林山脉和库克斯山脉的最终发掘发生在相似的时间范围内。在富兰克林山脉中，将红崖石花岗岩置于浅层深度，然后将其埋藏，压实。在富兰克林山脉和库克斯山脉的最后一次挖掘是在相似的时间范围内进行的。在富兰克林山脉中，将红崖石花岗岩置于浅层深度，然后将其埋藏，压实。在富兰克林山脉和库克斯山脉的最后一次挖掘是在相似的时间范围内进行的。在富兰克林山脉中，将红崖石花岗岩置于浅层深度，然后将其埋藏，压实。根据对Red Bluff花岗岩的地球化学研究，表明它是在伸展应力场中形成的[39]。富兰克林山脉和库克斯山脉的良好路径都保持了冷却至近地表温度在800至500 Ma之间的脉冲（图7（b）和7（c））。这些结果与以前的ZHe热年代学研究相似。DeLucia等。[14]给出了密苏里州奥扎克高原的ZHe数据和反演模拟结果，记录了从850至680 Ma和225至150 Ma的回火脉动，与Rodinia的破裂和Pangaea的破裂相吻合。他们提出了大陆隆升/剥蚀与超大陆循环之间的遗传关系，在新墨西哥州南部和德克萨斯州西部的岩石中也观察到这种关系。在新墨西哥州南部和德克萨斯州西部，落基山祖先的大陆内部变形导致一系列隆升和沉积盆地（例如，[19]）。祖先洛矶山脉盆地中保存的沉积记录表明，西部的逆时针沉降历史很年轻，这种模式被解释为反映了Ouachita缝合线的历时闭合[74]。在研究区域内，佩德雷戈萨和奥罗格兰德盆地经历了相似的峰值下沉速率，从大约300 Ma到285 Ma [74]。卡里佐山脉和库克山脉的反演模型包括古生代约束箱，其允许在450至290 Ma范围内的广泛埋葬温度（50–300°C）（图7）。好的路径对任何一个模型中的峰值埋藏温度都不敏感，除非它们不能被加热到> 180°C的温度。这些路径对再加热的时间也不敏感，路径达到了450至300 Ma的峰值温度。这些观察结果表明，至少在这个研究区域中，ZHe数据集对祖先洛矶山的时间或大小都不敏感。变形（图9）。取而代之的是，这些日期-铀的模式主要由影响这些岩石热史的较早和较年轻事件的时间和大小控制。这些观察对于将来可能的研究很有用。为了使用ZHe热年代学研究与落基山祖先事件相关的墓葬和掘尸活动，我们建议要么将重点放在构造历史不太复杂的位置上，以使date-eU模式主要受祖先洛矶山变形控制，要么将ZHe数据与约束较早或较年轻构造历史的其他数据集结合使用。西南新墨西哥州，东南亚利桑那州和墨西哥北部的索诺拉（Sonora）经历了侏罗纪晚期的裂谷作用，形成了比斯比盆地[48，49]。到阿比安时代，新墨西哥州南部的裂谷盆地地层达到最大厚度约2800 m [48]。在剖面底部（Lawton等人的TSA1，已出版）附近，这些地层夹有软流圈衍生的镁铁质火山岩[52]。流域两侧的地层较薄或根本不存在，因为裂谷台肩是盆地发展过程中的地形高点。这项研究的样本都沿着裂谷的推断边缘（Lawton等，已出版），但它们仍然可能经历了大陆裂谷中常见的升高的地热梯度（例如，[75，76]）。此外，在我们研究区域附近的地区上地壳中注入铁镁质岩浆可能是传导地幔热量的一个因素。裂谷中的梯度可以超过60°C / km [77]，但在延伸结束后可以迅速降低。这些升高的地热梯度可能是所有三个样品位置最高温度的原因。在比斯比盆地，裂谷后又缩短，导致在阿尔本时代建立了一个盆地，该盆地以对墨西哥弧-大陆碰撞的动态沉降为主导（Lawton等，印刷中）。从而，在研究区域内，地热梯度可能会恢复到100 Ma的正常值。新墨西哥州南部和德克萨斯州西部处于拉拉米德变形的东部。在新墨西哥州南部，东北向缩短作用产生了一系列西北向的盆地和隆升，其年龄从白垩纪晚期到始新世[22]。大部分（如果不是全部）拉拉酰胺断层是在墨西哥边境裂谷形成过程中重新激活的正常断层[22，78]，许多逆冲断层的抛距范围超过几公里（例如，[79]）。与拉拉米德缩短有关的断层和褶皱沿着德克萨斯州-墨西哥边境向大弯国家公园（Big Bend National Park）延伸[80]。但是，这些结构并不延伸到卡里佐山脉，那里的拉拉米德变形由小振幅褶皱和较小的逆冲断层构成[81]。新墨西哥州西南部的拉拉胺岩浆作用发生在大约75–70 Ma和60–55 Ma之间以及45–40 Ma之间的几个脉冲中[82，83]。证据包括凝灰岩[82]，盆地中的安山岩巨石[84]，诸如Sylvanite复合体的深成岩[79]，以及与矿床有关的各种侵入岩[85]。我们的逆建模结果旨在仅包括Laramide隆起期间的发掘和冷却，尽管这些模型的非唯一性并不排除一定量的Laramide再加热。除了裸露的火山岩和深成岩外，更深的拉拉酰胺深成岩也可能影响了这两个年代。例如，Murray等。[86]提供了数值模型，表明中地壳俯冲体可以重置上地壳岩石的低温热年代学年龄。这是此处未探讨的结果，在库克斯山脉和富兰克林山脉的反演模型中保留了与拉拉米德造山运动同等的冷却效果。在库克斯山脉中，路径显示出冷却脉冲，开始于60-70 Ma，结束于45 Ma（图9）。富兰克林家族保留了大约80到50 Ma的相似冷却时间。尽管新墨西哥州南部在晚白垩世存在散布的拉拉酰胺盆地，但大多数盆地和隆升主要在古新世-始新世[22]发育，与库克斯山脉和富兰克林山脉的反演模型重叠。相比之下，卡里佐山脉在这段时间内几乎没有降温，新生代降温到近地表温度的时间推迟到30 Ma之后（图9）。这些观察结果与拉里酰胺缩短带边缘的卡里佐山脉位置一致，那里的总变形很小。新墨西哥州南部的新近纪里奥格兰德大裂谷破坏了所有先前的构造元素，并赋予了景观当前的地形颗粒。在得克萨斯州埃尔帕索的纬度，该裂谷突然弯曲，并在该趋势南北向东南向构造，而不是像在裂谷中部和北部那样沿南北向构造。在科罗拉多州和新墨西哥州，磷灰石裂变径迹和磷灰石（U-Th）/ He数据相结合，表明该区域的扩展在很大程度上是同步的，这些数据记录了从25Ma到10Ma的主要冷却脉冲，这被解释为反映了延伸性掘尸（例如[28，87–89]）。来自所有三个研究地点的逆模型都保留了与里奥格兰德裂谷的发展同时出现的冷却脉动。快速冷却开始于Cookes山脉约25 Ma，富兰克林山脉约25-15 Ma，卡里索山脉约30 Ma（图9）。尽管这个时间范围只是整个热历史记录（超过十亿年）的一小部分，但似乎对每个位置产生的ZHe date-eU曲线都产生了重大影响。这些结果与先前发表的来自南部裂谷的低温热年代学数据和模型一致，表明该裂谷的南部部分与中部和北部部分同时处于活动状态，岩石的冷却是通过断层发掘来完成的。比通过岩浆注入[28，87]。在新墨西哥州南部和得克萨斯州西部的三个范围内总共提供了55种ZHe枣粒。该日期跨越亿万年，并记录了元古代晶体岩石的长期热历史。这些岩石经历了较长的构造历史，涉及多个时期的冷却和再加热。正向和反向建模技术的组合用于研究这些样品的合理热历史。我们发现，尽管前向建模方法有利于快速比较几个不同的热历史，但逆向建模方法可以进一步完善这些结果并可以测试成千上万的可能的tT路径。结论：（1）富兰克林山脉的红色布拉夫花岗岩可能在古生代沉积物沉积之前就被掩埋和掘出，因此该位置的不整合面是一个复合的侵蚀面；（2）在这三个地点的元古代发掘出土都发生在800至500 Ma之间，这与Rodinia的分裂相吻合；（3）这三个研究地点均记录到约100 Ma的高温，这很可能反映了大陆裂谷形成中生代比斯比盆地时热流的升高。这些结果表明，裂谷内部升高的热流延伸到裂谷肩部，而不是局限于裂谷轴上。（4）拉克酰胺的冷却在库克斯山脉从70到45 Ma，在富兰克林山脉从80到50 Ma。相比之下，卡里佐山脉在拉拉米德缩短期间没有降温，这很可能反映了其在观察到的拉拉米德变形边缘的位置；（5）所有三个研究地点都保留了始于30-25 Ma的降温脉冲，同时在裂谷的中部和北部都观察到了降温。相反，这些数据几乎没有提供有关降温时间或幅度的信息。祖先的落基山变形。这些数据提供了有关新墨西哥州南部和德克萨斯州西部广泛的热史的重要信息，并突出说明了在构造复杂的地区中使用ZHe方法的有效性。这些数据还有助于弥合诸如磷灰石（U-Th）/ He之类的低温系统与诸如40Ar / 39Ar之类的裂变径迹和高温年代学方法的高温方法之间的鸿沟。作者宣称，它们没有利益冲突。JWR得到了NSF-EAR 1624538的支持，而JMA得到了NSF-EAR 1624575的支持。这些数据是从CU Boulder的（U-Th）/ He热年代学实验室获得的。我们感谢Rebecca Flowers和James Metcalf在数据采集和讨论方面的帮助，以及Michelle Gavel在矿物准备方面的帮助。两名匿名审稿人提供了非常有用的反馈，有助于改善该手稿的质量。表S1：热历史模型输入以及正向和反向模型的假设。图S1：正向和反向模型中使用的地质约束条件的描述。两名匿名审稿人提供了非常有用的反馈，有助于改善该手稿的质量。表S1：热历史模型输入以及正向和反向模型的假设。图S1：正向和反向模型中使用的地质约束条件的描述。两名匿名审稿人提供了非常有用的反馈，有助于改善该手稿的质量。表S1：热历史模型输入以及正向和反向模型的假设。图S1：正向和反向模型中使用的地质约束条件的描述。