Most metasedimentary rocks in the southern Coast Mountains batholith are of uncertain tectonic affinity because they occur in discontinuous pendants surrounded by large intrusive bodies, and many protolith features are obscured by regional deformation and metamorphism. This study uses U-Th-Pb ages and Lu-Hf isotope signatures of detrital zircons in metasedimentary rocks in Bute, Loughborough, and Knight Inlets in an effort to test possible correlations with the adjacent Wrangellia, Alexander, Taku, Yukon-Tanana, and Stikine terranes. Detrital zircons from metasedimentary samples yield ages that belong to age groups of 590-528 Ma (peak age of 560 Ma), 485-432 Ma (peak age of 452 Ma), 356-286 Ma (peak age of 307 Ma), and 228-185 Ma (peak ages of 215 and 198 Ma). A small number of ~1.1-1.9 Ga grains are also present. εHft values of the 590-185 Ma grains yield a progression from intermediate (0 to +5) values to more juvenile (mostly +4 to +15) values from Neoproterozoic through early Mesozoic time. The Comparison of these results with similar data sets from adjacent terranes demonstrates that primary connections with the Yukon-Tanana and Taku terranes are unlikely but are consistent with primary connections with the Wrangellia, Stikine, and/or Alexander terranes. Unfortunately, the available constraints are not sufficient to eliminate any of these options or the possibility that the pendants are a unique tectonic fragment. Zircons from the metasedimentary samples also yield U-Th-Pb ages of 165-128 Ma (peak age of 152 Ma) and 114-88 Ma (peak age of 102 Ma). εHft values of these zircon domains are mostly juvenile (+7 to +13). Comparison of U concentrations, U/Th values, and CL textures of zircons from the metasedimentary samples, leucocratic sills that intrude the pendants, and surrounding plutonic bodies suggests that most of the young grains, as well as widespread younger rims on older grains, grew during metamorphism associated with emplacement of the adjacent plutonic bodies. Some young grains were derived from thin felsic sills or veins that were unintentionally included in the sampled material.The Coast Mountains of western British Columbia and southeast Alaska are underlain mainly by Jurassic, Cretaceous, and early Tertiary plutons that intrude a variety of metasedimentary and metavolcanic rocks (Figure 1). In the northern and central Coast Mountains, the tectonic affinity of metasedimentary and metavolcanic pendants has been reconstructed on the basis of lithic characteristics combined with U-Th-Pb geochronology and Hf isotope analyses of detrital zircons [1–5]. From west to east, the main terranes/assemblages include the Alexander, Taku, Yukon-Tanana, and Stikine terranes (Figure 1).The tectonic affinity of metasedimentary assemblages in the southern Coast Mountains was originally assigned on the basis of protolith characteristics by Wheeler and McFeely [6], Wheeler et al. [7], and Journeay et al. [8] (Figure 1). Components are interpreted to include Paleozoic and lower Mesozoic rocks of the Wrangellia terrane (Insular superterrane), Upper Jurassic-Lower Cretaceous volcanic and clastic rocks of the Gambier Group, and metamorphic rocks of uncertain affinity. More recently, Rusmore et al. [9] have raised the possibility that rocks in this portion of the Coast Mountains belong to inboard terranes of the Intermontane superterrane (e.g., Stikine terrane). Distinguishing between these two possibilities is important given that inboard rocks of Intermontane superterrane likely formed and evolved in proximity to the Cordilleran margin, whereas outboard rocks of the Insular superterrane likely formed in the paleo-Arctic ocean basin (e.g., [10]). This study attempts to evaluate these tectonic affinities and possible connections with the nearby Alexander or Yukon-Tanana/Taku terranes, by presenting U-Th-Pb geochronologic data and Hf isotopic data on detrital zircons that have been extracted from metasedimentary rocks in Bute, Loughborough, and Knight Inlets (Figure 1).Rocks of the Coast Mountains batholith are spectacularly exposed along the glacially scoured and wave-washed fjord walls of Bute, Loughborough, Knight, and associated smaller inlets (Figure 2). As reported by Cecil et al. [11], the batholith in this region consists mainly of dioritic, tonalitic, and granodioritic plutons and intrusive complexes that range in age from ~170 Ma to ~85 Ma. Metasedimentary and metavolcanic rocks occur as highly elongate pendants separating plutons that are also elongate northwest-southeast [11]. The width of the pendants is highly variable, with most on the order of 10s to 100s of meters, but some over a kilometer in width. All rocks are strongly foliated parallel to the pendant margins, which is parallel to the foliation in all but the youngest plutons in the area (Figure 3(a)).Metasedimentary and metavolcanic rocks in the study area have been divided into three assemblages that have varying proportions of quartzite, marble, pelitic schist, and metabasalt and a fourth assemblage that lacks these lithic associations and consists only of fine-grained metaclastic and metavolcanic rocks (Figure 2). All four assemblages are found entirely east of low-grade sedimentary and volcanic rocks of the Karmutsen, Quatsino, Parsons Bay, and Harbledown formations ([12, 13]; Figure 2), which belong to the Wrangellia terrane.The first assemblage, extending across the southwestern part of the study area and in upper Knight Inlet, is found in pendants that consist mainly of interlayered quartzite and marble (Figure 3(b)) with subordinate pelitic schist and local calcsilicate. Layering is on a 1-3 cm scale, and quartzite is generally more abundant than marble. The quartzite layers are quite pure, consisting almost exclusively of quartz and calcite. Sampling these rocks for detrital zircons is challenging because most outcrops are intruded by swarms of intrusions which occur as several cm-thick aplitic sills. In most cases, these bodies share the regional foliation exhibited in their host rocks. In rare exposures, they can be seen to intrude at oblique angles across the metasedimentary layering.A second assemblage, tracing northwest-southeast across upper Bute Inlet, consists of pelitic schist and quartzite that are interlayered on a cm scale (Figure 3(c)). Interlayered quartzite and marble, similar to the unit described above, is a minor component of this assemblage. In most outcrops, pelitic schist is dominant over thin (cm-thick) layers of quartzite (Figure 3(c)). Garnet is present in some outcrops. These pendants also include foliated leucocratic sills, but they are easy to distinguish from the dominantly pelitic host rock (e.g., Figure 3(c)).A third assemblage consists of two belts of metabasalt and subordinate marble that crop out in Bute and Knight Inlets (Figure 2). These layers are present near sequences dominated by quartzite and marble, but continuity with adjacent units could not be established. The metabasalt is dominantly massive, with pillows observed locally. Meter-thick layers of white marble are locally interlayered with the metabasalt.The fourth assemblage, extending across the middle of the study area, consists of several pendants that are dominantly intermediate-composition metavolcanic rocks with subordinate metasedimentary layers. Most metavolcanic rocks are tuffaceous and interlayered with fine-grained volcanic-rich strata. Several outcrops also include more massive layers that display relict pillows and fragmental textures. No occurrences of quartzite, marble, or pelitic schist have been found in this assemblage, suggesting that these rocks comprise a distinct tectonostratigraphic unit.Most previous workers have suggested that metamorphic rocks in the study area belong to the Wrangellia terrane and overlying strata of the Gambier Group (Figure 1). Journeay et al. [8] assigned the quartzite-marble-metapelite-metabasalt assemblages described above to the Karmutsen Formation, which consists mainly of Triassic basalt flows and subordinate sedimentary units that are exposed on much of Vancouver Island (Figure 1). Extensive Triassic basalts are one of the hallmarks of the Wrangellia terrane [14, 15]. Roddick and Woodsworth [16] expanded this assignment to include the possibility that some protoliths may be Paleozoic (pre-Karmutsen) in age.Volcanic-rich rocks that occur in the middle portion of the study area were assigned to the Lower Cretaceous Gambier Group by Journeay et al. [8] and Roddick and Woodsworth [16]. The Gambier Group is interpreted as a basinal arc that accumulated along the inboard margin of the Wrangellia terrane [17, 18].Rusmore et al. [9] suggested instead that pendants in the study area may belong to terranes that are located inboard of the Coast Mountains (e.g., the Stikine terrane) on the basis of (1) the occurrence of plutons with distinctive Early Cretaceous ages that, to the north, intrude rocks of the Stikine terrane and (2) paleomagnetic inclinations of plutons in the study area that are more similar to inboard terranes than outboard terranes.Seventeen samples were collected and analyzed in an effort to test the interpretations noted above. Most samples were collected from quartz-rich layers that are interpreted to be metaclastic based on the low abundance of mafic minerals, cm-scale interlayering with marble and/or pelitic schist, and lack of cross-cutting relations with adjacent compositional layers. As noted above, one of the challenges in collecting metasedimentary samples is the common occurrence of foliated leucocratic sills that resemble the quartz-rich metaclastic layers in low color index, orientation (generally parallel to layering), degree of development of foliation and lineation, and resistance to weathering. In an effort to determine whether our metasedimentary samples also contained igneous material, we collected three samples of leucocratic sills to serve as a reference for comparison. Recognition of zircons with similar ages and Hf isotope signatures in both metasedimentary and metaplutonic samples would indicate that our metasedimentary samples contained unrecognized igneous material. Conversely, grains in the metasedimentary samples that are older than the intrusive bodies (and surrounding plutons) would be confidently interpreted as detrital components. The ages of the sills also provide a minimum depositional age for the metasedimentary pendants. Approximately 5-10 kg of rock was collected for each sample. Samples are described in DR Table 1; locations are shown in Figure 2.Considerable time was spent examining the metavolcanic pendants in the study area (Figure 2). Samples were not collected from these strata, however, because of the fine grain size and quartz-poor composition of the rare metaclastic strata.Samples were processed and analyzed at the Arizona LaserChron Center utilizing methods of Gehrels [19], Gehrels et al. [20], Cecil et al. [21], Gehrels and Pecha [22], and Pullen et al. [23] (https://www.laserchron.org). Zircons were extracted with a jaw crusher and a roller mill and then separated from lighter minerals with a Wilfley table. The resulting heavy mineral fraction was further separated with a Frantz LB-1 magnetic barrier separator and methylene iodide.Several hundred grains from each sample were mounted along with three zircon standards (Sri Lanka, FC-1, and R33) for U-Th-Pb analyses and six zircon standards (R33, Mud Tank, FC-1, Plesovice, Temora2, and 91500) for Lu-Hf isotopes. Mounts were polished to a depth of ~20 microns in order to reveal grain interiors and then imaged with back-scattered electron (BSE) and Cathode Luminescence (CL) detector systems connected to a Hitachi S-3400N scanning electron microscope.All U-Th-Pb analyses were performed by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) using a Photon Machines G2 excimer laser connected to either a Nu multicollector ICPMS [20, 22] or an Element2 single-collector ICPMS [23]. For an initial set of analyses, the Element2 ICPMS was used to analyze between 110 and 315 zircon grains per detrital sample and ~35 zircon grains per igneous sample. One spot was analyzed per grain using a laser beam diameter of 20 microns. Details of the analytical methodology are reported in DR Table 2. Results of the U-Th-Pb analyses are reported in DR Table 3.As described below, this first set of analyses yielded ages of ~151, 150, 150, 104, and 102 Ma for the leucocratic sill samples and ages that range from ~1948 to ~88 Ma for metasedimentary samples. The occurrence of ages in metasedimentary samples that overlap with ages of the sills indicated that igneous material may have been incorporated into the samples during collection and/or that the young ages record growth of metamorphic zircon. In an effort to distinguish between these two explanations, the following sections explore the CL characteristics of the analyzed grains [as described by Corfu et al. [24]] as well as their Hf isotope signatures, U concentrations, and U/Th values. In regard to the latter, we follow Rubatto [25], Kirkland et al. [26], and Yakymchuk et al. [27] in recognizing that metamorphic zircon commonly has higher U concentration and higher U/Th than igneous zircon. We also compare our data with values from nearby plutonic bodies given the possibility that sills of other ages are present in the metasedimentary samples. In conducting these comparisons, we use 170 Ma as the cutoff between older grains that are likely detrital in origin and younger grains that may be igneous and/or metamorphic in origin given that metasedimentary pendants in the study area are intruded by plutons as old as ~167 Ma [11] and yield few ages between ~185 Ma and 165 Ma.In an effort to further explore the possibility that some of the analyzed domains are metamorphic in origin, we conducted a second set of analyses that involved acquiring high-resolution CL images to examine grain textures and conducting U-Th-Pb analyses on each of the domains recognized on CL images. These age-mapping analyses were conducted with the Nu multicollector ICPMS utilizing a 10 μm laser beam diameter. Between 5 and 33 analyses were conducted on each grain. Spot locations were determined from postanalysis BSE images. Details of the analytical procedures are reported in DR Table 2, and the analytical results are reported in DR Table 3.U-Th-Pb ages of zircons from the metasedimentary samples are summarized in Figure 4, following the interpretation that >170 Ma grains are detrital and <170 Ma grains are igneous and/or metamorphic in origin. Maximum depositional ages are determined from the peak ages on probability density plots [e.g., Gehrels [19], Dickinson and Gehrels [28], Gehrels [22]]. Figure 5 explores the origin of the <170 Ma grains by comparing the age versus U/Th of zircons from the three samples of leucocratic sills, the metasedimentary rocks intruded by these sills, and nearby plutons. Figure 6 presents images and age information for several of the more informative grains that have been analyzed by age mapping.Hf isotopic analyses were carried out utilizing methods reported by Cecil et al. [21] and Gehrels and Pecha [22], using settings reported in DR Table 2. Analyses were conducted on grains from each age group from each sample. Hf analyses were conducted with a 40 μm laser beam, with the Hf pit located on top of the U-Th-Pb pit. This increases the likelihood that the U-Th-Pb and Hf data are from the same age domain. All of the Hf isotopic data are presented in Table DR 4, including Hf-evolution plots for each sample.Figure 7 displays the Lu-Hf isotopic data from all samples. This diagram reports the data in terms of εHft, which is the 176Hf/177Hf ratio relative to the chondritic uniform reservoir (CHUR) [29] at the time of crystallization. Also shown on this diagram are the depleted mantle array (DM) from Vervoort and Blichert-Toft [30] and the Hf isotopic evolution of average continental crust, which is based on a 176Lu/177Hf ratio of 0.0115 [31, 32]. The average precision of our measurements is 2.2 epsilon units (at 2σ⁠).As noted above and shown in Figure 4, nearly all of the metasedimentary samples yield both <170 Ma grains that overlap with the ages of nearby plutons, as well as >170 Ma grains that are interpreted to be detrital in origin. Each set of ages is described in a separate section below.Twelve samples collected from pendants dominated by quartzite and marble yield variable proportions of ages that range from ~590 Ma to ~185 Ma, with dominant peak ages for each sample of 560, 452, 411, 345, 331, 322, 319, 216, 209, and 198 Ma (Figure 4). Three samples from the pelitic schist-quartzite pendant consist mainly of grains in the 370-270 Ma range, with dominant age peaks of 349, 310, and 302 Ma. With all ages combined (upper curve of Figure 4), there are four main age groups of 590-528 Ma (peak age of 560 Ma), 485-432 Ma (peak age of 452 Ma), 356-286 Ma (peak age of 307 Ma), and 228-185 Ma (peak ages of 216 and 199 Ma). Although each sample is dominated by grains from only one of these age groups, most samples contain subordinate populations from other age groups: three samples contain ages in the 590-528 Ma range, five samples contain 485-432 Ma ages, thirteen samples yield 356-286 Ma ages, and twelve samples contain 228-185 Ma ages.Maximum depositional ages are assigned for the metasedimentary protoliths using the rubric that the most reliable age is determined from the youngest cluster of at least three ages that overlap within 2-sigma uncertainty [28]. This yields maximum depositional ages of 349, 310, and 302 Ma for the three pelitic schist-quartzite samples, with ages that decrease northeastward across the pendant (Figure 2). Maximum depositional ages for the quartzite-marble samples are 345, 341, 319, and 216 Ma for the southern pendant and 333, 331, 322, 209, and 198 Ma for the northern pendant. Given that four of the six samples with >300 Ma maximum depositional ages also contain individual ages between 250 and 170 Ma, it is likely that all of the quartzite-marble samples accumulated after 250 Ma. No spatial pattern of dominant or maximum depositional ages within or between the two quartz-marble pendants is apparent. The comparison of maximum depositional ages of the pelitic schist-quartzite versus quartzite-marble pendants suggests that pelitic schist-quartzite protoliths likely accumulated during late Paleozoic time, whereas quartzite-marble protoliths likely accumulated during Triassic-Early Jurassic time. In addition to these <590 Ma ages, six older grains were found in the quartzite-marble samples, with ages of ~1948, ~1845, ~1775, ~1701, ~1429, and~1109 Ma. Only one age of ~1119 Ma was found in a sample from the pelitic schist-quartzite assemblage.All of the quartzite-marble samples, and one of the three pelitic schist-quartzite samples, also yield a significant number of <170 Ma ages (Figure 4). Most samples display two sets of ages that range from 165 to 128 Ma and from 114 to 88 Ma. As noted above, these cannot be detrital ages given that the pendants are intruded by plutons that are as old as ~167 Ma. The following sections highlight the available U-Th-Pb, U/Th, U concentration, and CL textural information that constrains the origin of these young grains. Information from three pendants with both igneous and metasedimentary samples is described first to provide interpretive guides for pendants that do not have igneous samples.Figure 5 summarizes the ages, U concentrations, and U/Th values of zircons from leucocratic sills and host-rock metasedimentary samples from three outcrops. The results presented in this section are from our first set of analyses, which consisted of one analysis per grain. For each sample, patterns of age, U concentration, and U/Th are evaluated in an effort to distinguish whether ages from the metasedimentary samples record igneous versus metamorphic crystallization. In distinguishing between the two, we follow Rubatto [25], Kirkland et al. [26], and Yakymchuk et al. [27] in the interpretation that metamorphic zircon commonly has higher U concentration and higher values of U/Th than igneous zircon.For locality 15KN63 (Figures 5(a) and 5(b)), the igneous sample (15KN63C) yields thirty-two younger ages (peak age of ~104 Ma) and three older ages (peak age of ~149 Ma) (DR Table 3). The three older ages are from clearly visible cores in CL images. Analyses from both age groups yield relatively low U concentrations and U/Th values, which suggests that all analyzed domains are igneous in origin. Zircons in the metasedimentary samples from this outcrop (15KN63A and B) yield similar age groups (peak ages of ~153 and ~104 Ma), with a greater proportion of older ages. Most of the younger grains yield U concentrations and U/Th values suggestive of igneous crystallization, whereas some older grains yield higher values suggestive of metamorphic crystallization.For locality 15KN68 (Figures 5(c) and 5(d)), the igneous sample (15KN68B) yields both older and younger ages, with peak ages of ~102 Ma (dominant, mostly from rims) and ~151 Ma (subordinate, mostly from cores) (DR Table 3). There also are cores that yield considerably older detrital ages. U concentrations and U/Th values for all grains in this sample are typical of igneous zircon. The metasedimentary sample from this outcrop yields similar age groups, with most ages defining a peak age of ~153 Ma, as well as a smaller proportion of ages with a peak age of ~107 Ma. There are a small number of older detrital grains that range in age from ~1109 to ~173 Ma. U concentrations and U/Th values for most grains are low, suggestive of igneous crystallization, although some range to higher values suggestive of metamorphic crystallization.For locality 15KN69 (Figures 5(e) and 5(f)), the igneous sample (15KN69B) yields only one main age group with a peak age of ~149 Ma, plus two older core ages of ~215 and ~365 Ma (DR Table 3). Metasedimentary sample 15KN69A yields subequal proportions of older and younger grains (peaks at ~149 and~92 Ma). Most analyses from both igneous and metasedimentary samples yield low U concentrations and U/Th values, suggestive of igneous crystallization.Zircon grains with <170 Ma ages were also found in most of the other metasedimentary samples (Figure 4). The ages, U concentrations, and U/Th values from analyses of these grains are shown in Figures 5(g) and 5(h). These samples yield a subequal proportion of grains with ages between 167 and 125 Ma (peaks at ~150 and~142 Ma) and between 115 and 84 Ma (peak at ~101 Ma). Most U/Th values are low, and presumably igneous in origin, but a significant number have considerably higher values consistent with a metamorphic origin.In an effort to further constrain the origin of the <170 Ma grains in these samples, we conducted age-mapping analyses on 16 zircon crystals from five samples (one igneous and four metasedimentary). Details of these analyses are presented in DR Tables 2 and 3. Figure 6 summarizes results of our findings, with one grain from a leucocratic sill that records igneous crystallization at ~101 Ma, two grains from metasedimentary samples that record igneous crystallization at ~151 and~104 Ma, and two grains from metasedimentary samples that are interpreted to record metamorphic crystallization at ~155 Ma and ~103 Ma.The grain shown in Figures 6(a) and 6(b) is from a leucocratic sill (15KN63C) that intrudes metasedimentary rocks (15KN63A and B). The oscillatory and sector zoning (cf. Corfu et al., 2013) seen in the CL image combined with the low U/Th values suggest that this grain is igneous in origin, with an age of ~101 Ma. Figures 6(c) and 6(d) show a grain from the host metasedimentary rocks (sample 15KN63A), which has similar oscillatory zoning, an age of ~104 Ma, and a typical igneous U/Th average value of ~3.0. The similarity in characteristics of these two grains suggests that metasedimentary sample 15KN63A included unrecognized igneous material from one or more leucocratic sills.The grain shown in Figures 6(e) and 6(f) is from metasedimentary sample 15KS51. This grain has a highly disaggregated core with ages of 236-198 Ma (average of ~212 Ma) that is surrounded by a rim with an average age of ~103 Ma. The convolute texture (cf. [24]) of this outer rim, combined with U/Th values of 46-14 (average of ~24.2), suggests that this grain records growth of metamorphic zircon during mid-Cretaceous time.The grain shown in Figures 6(g) and 6(h) is also from metasedimentary sample 15KN63A. It has convolute zoning and low U/Th values, similar to the grain shown in Figures 6(c) and 6(d), but it yields an age of ~151 Ma. The occurrence of this grain, and others with similar properties (DR Tables 2 and 3), suggests that Late Jurassic igneous components are also present in some of the metasedimentary samples.In contrast, a metamorphic origin for other Late Jurassic grains is suggested by the grain shown in Figures 6(i) and 6(j), which is from metasedimentary sample 15KN73. This grain contains a core with an average age of ~559 Ma and a rim with an average age of ~155 Ma. U/Th values suggest that the core is igneous in origin, whereas the rim grew during regional metamorphism. Between the two is an intermediate domain that yields ages ranging from 457 to 230 Ma, presumably due to the analysis of a mixture of material from older and younger domains. Relations displayed by this grain suggest that some Late Jurassic zircon is metamorphic in origin.Figures 8(a) and 8(b) present a comparison of the ages, U/Th values, and U concentrations of zircons from metasedimentary samples, leucocratic sills, and plutons near the sample sites [pluton data from Cecil et al. [11]]. The overlap of ages, U/Th values, and U concentrations of the leucocratic sills and adjacent plutons suggest that the sills are genetically related to the adjacent plutonic bodies. The similarity of ages, U/Th values, U concentrations, and CL textures in zircons from the metasedimentary samples and leucocratic sills suggest that many of the grains in our metasedimentary samples are igneous in origin and were inadvertently incorporated into the samples despite careful selection of material on the outcrop and during sample processing. On subsequent inspection, a 5 mm wide aplite vein was discovered in a hand sample from sample 15KN73—similar veins may have been the source of igneous material in this and other samples. The higher U/Th values, U concentrations, and convolute CL textures seen in some whole grains and the rims of many grains indicate that metamorphic zircon is also present. The presence of metamorphic zircon in these samples is not surprising given the occurrence of garnet in the northeastern pendants.Given the interpretation that zircons (or zircon rims) with high U/Th and high U concentration are metamorphic in origin, the patterns shown in Figures 8(a) and 8(b) are interpreted to provide a record of the spatial and temporal distribution of metamorphism in the study area. Assuming that a U/Th value of 8 is a reasonable cutoff for igneous versus metamorphic zircon growth (Figure 8(a)), 425 of the 1074 analyses (~40%) are metamorphic in origin. Although we cannot assume that new zircon growth was associated with all metamorphic events, these data indicate that metamorphism occurred between ~111 and ~90 Ma, with peaks at 106, 101, and 92 Ma, and between ~171 and ~127 Ma, with peaks at 153 and 136 Ma. Assuming instead that a U concentration of 1100 ppm is a reasonable cutoff for igneous versus metamorphic zircon growth (Figure 8(b)), 572 of the 1074 analyses (~53%) are metamorphic in origin. Metamorphism appears to have occurred between ~115 and ~86 Ma, with peaks at 107, 101, and 93 Ma, and between ~168 and ~131 Ma, with peaks at 152 and 136 Ma.εHft values for our metasedimentary and igneous samples are shown in Figure 7. Shown separately are >170 Ma analyses that are interpreted to be detrital and <170 Ma analyses from leucocratic sills versus metasedimentary samples. The latter are further divided into analyses with U/Th>8 (interpreted to be of metamorphic origin) versus analyses with U/Th<8 (interpreted to be igneous in origin).Analyses from metasedimentary samples yield a progressive evolution from more evolved to more juvenile through time. As shown in Figure 7, the sliding window average of εHft values increases from ~three for 590-528 Ma grains to ~eight for 485-432 Ma grains to ~twelve for 356-286 Ma grains. This is interpreted to record a progressive increase in the proportion of juvenile material through time. The εHft values remain juvenile through time in the 228-185 Ma grains.Average εHft values for <170 Ma grains show slightly lower average values for 165-128 Ma grains and then a return to more juvenile values for 114-88 Ma grains. For 165-128 Ma analyses, εHft values from grains that are interpreted to be of igneous origin (grains from sills and from metasedimentary samples with low U/Th) are more negative than εHft values from grains interpreted to be of metamorphic origin (Figure 7). This suggests that the grains (or rims) of metamorphic origin were derived from a different source than the grains of igneous origin. Assuming that the metamorphic zircon grew at the presently exposed crustal level, whereas the igneous zircons grew primarily at deeper crustal levels (where the magmas were generated), the occurrence of more negative εHft values for igneous zircons may reflect the presence of somewhat more evolved crustal materials at lower crustal levels during 165-128 Ma magmatism. One possibility is that these more evolved crustal materials included rocks from which the 600-400 Ma grains in our samples were derived (Figure 7).It is also possible that metamorphic zircons yield higher εHft values than igneous zircons due to interaction with other minerals (e.g., apatite or amphibole) during metamorphism. This interpretation is not supported by the observation that igneous and metamorphic grains of both ~165-128 Ma and~114-88 Ma age yield similar ranges and average values of 176Lu/177Hf (DR Table 5).Our results are compared with data from relevant terranes in Figures 9–11 and in the following sections. Most appropriate for comparison are the Wrangellia and Stikine terranes given the previous interpretations that pendants in Bute, Loughborough, and Knight Inlets are metamorphic equivalents of strata belonging to these terranes. We also compare with (1) strata of the Alexander terrane, which occur outboard of the Coast Mountains north of the study area, and (2) the Taku and Yukon-Tanana terranes, which occur within and along the western flank of the Coast Mountains north of the study area (Figure 1).The Vancouver Island portion of Wrangellia, as described by Yorath et al. [15] and Ruks [14], contains several exposures of Paleozoic rocks that include Upper Devonian-Lower Mississippian (366-336 Ma) bimodal volcanic rocks of the Sicker Group, Mississippian-Pennsylvanian argillite, shale, chert, limestone, and sandstone of the Fourth Lake and Thelwood Formations, upper Pennsylvanian-Lower Permian (312-292 Ma) mostly felsic volcanic rocks, and Lower-Middle Permian carbonate rocks of the Buttle Lake Formation. These rocks are overlain by a regionally extensive cover that consists, from oldest to youngest, of Middle and Upper Triassic basalt (Karmutsen Formation), thick-bedded to massive limestone (Quatsino Formation), and thin-bedded siltstone, shale, and limestone (Parson Bay Formation). These rocks are overlain by Lower Jurassic (~200-170 Ma) basaltic to rhyolitic volcanic rocks and subordinate volcanic-rich sedimentary rocks of the Bonanza Group [15, 33].Jurassic and older rocks are overlain along the eastern margin of Vancouver Island by unconformably overlying Upper Cretaceous conglomerate, sandstone, mudstone, and shale of the Nanaimo Group [15], the basal unit of which contains abundant ~400-170 Ma detrital zircon grains that are interpreted to have been derived from rocks of Wrangellia [34]. Intrusive components include the latest Devonian-earliest Mississippian Saltspring Intrusive Suite [359-356 Ma; Ruks [14]] and the Early-Middle Jurassic Island Intrusions [190-165 Ma; DeBari et al. [33]].In the study area (Figure 2), strata along the eastern edge of Wrangellia [12, 13] include the following, from oldest to youngest: (i)~6 km of massive lava flows, pillow basalt, and fragmental breccia of the Karmutsen Formation (Upper Triassic)(ii)0-800 m of thick-bedded to massive gray limestone of the Quatsino Formation (Upper Triassic)(iii)Up to 600 m of gradationally overlying calcareous siltstone, shale, graywacke, and limestone of the Parsons Bay Formation (Upper Triassic)(iv)Up to 500 m of black argillite and subordinate fine-grained graywacke of the Harbledown Formation (Lower Jurassic)~6 km of massive lava flows, pillow basalt, and fragmental breccia of the Karmutsen Formation (Upper Triassic)0-800 m of thick-bedded to massive gray limestone of the Quatsino Formation (Upper Triassic)Up to 600 m of gradationally overlying calcareous siltstone, shale, graywacke, and limestone of the Parsons Bay Formation (Upper Triassic)Up to 500 m of black argillite and subordinate fine-grained graywacke of the Harbledown Formation (Lower Jurassic)Although Wheeler and McFeely [6], Wheeler et al. [7], and Journeay et al. [8] have proposed that metasedimentary and metavolcanic rocks in the pendants are metamorphic equivalents of strata belonging to Wrangellia, our field studies do not support these correlations. Primary differences are that (1) protoliths for the quartzite-marble assemblage have not been described in previous studies on Vancouver Island (or any other portion of Wrangellia) and were not recognized during our detailed mapping of lower Mesozoic strata belonging to Wrangellia within the study area; (2) protoliths for the pelitic schist-quartzite assemblage also have not been recognized in the study area, on Vancouver Island, or anywhere else in Wrangellia; and (3) mafic- to intermediate-composition volcanic rocks are widespread on Vancouver Island (and most other portions of Wrangellia) but are a minor component of the pendants in the study area.In contrast to these geologic differences, our U-Pb ages and Hf isotopic results are very similar to the results available from Vancouver Island, which include U-Pb ages on Paleozoic igneous rocks [14] and U-Pb/Lu-Hf data from detrital zircons extracted from Mississippian-Pennsylvanian sandstone layers of the Fourth Lake and Thelwood Formations and from Upper Cretaceous sandstone layers of the overlying Comox Formation of the Nanaimo Group [34]. As part of this project, we attempted to complement these results by analyzing detrital zircons from strata of the Karmutsen, Quatsino, Parsons Bay, and Harbledown Formations (Figure 2) but were unable to identify quartz-rich clastic strata in any of these units. Two samples of the coarsest-available graywacke horizons of the Harbledown Formation failed to yield zircons of sufficient size for analysis. Data from Ruks [14] and Alberts et al. [34] are summarized in Figure 9, with the age distributions of igneous and detrital zircons in the lower panel and εHft values of detrital zircons in the upper panel.U-Pb (zircon) ages from metasedimentary rocks in Bute and Knight Inlets show considerable overlap with ages from igneous and sedimentary rocks of Wrangellia (Figure 9(b)). Both sets display two dominant sets of ages, with age peaks of 307, 215, 198, and 179 Ma in the Bute-Knight pendants and age peaks of 341, 195, and 171 Ma for detrital grains and age peaks of 357, 308, 199, and 176 Ma for igneous grains from Wrangellia. Most impressive are the nearly identical age peaks of 307-308 Ma and 198-199 Ma for Bute-Knight pendants and igneous rocks of Vancouver Island. Both detrital zircon data sets also contain scattered >400 Ma grains, with age peaks of 560 and 452 Ma from Bute-Knight pendants but no distinct groups from Vancouver Island. εHft values from <400 Ma grains in the two regions are also similar, with highly juvenile values for both (Figure 9(a)).On the basis of these comparisons, we conclude that the metasedimentary and metavolcanic rocks in the study area may have primary connections with upper Paleozoic-lower Mesozoic strata on Vancouver Island. Such connections would require significant lateral changes in stratigraphy, including an eastward increase in the abundance of quartz-rich clastic strata and decrease in the proportion and extent of volcanic rocks.The Stikine terrane consists of Devonian limestone and marine clastic strata, Upper Devonian-Lower Mississippian volcanic rocks and associated 380-345 Ma plutons, Mississippian mafic volcanic rocks and marine strata, Pennsylvanian bimodal volcanic rocks (319-312 Ma), Permian carbonates, Middle and Upper Triassic volcanic rocks and associated plutons (226-200 Ma), and Lower-Middle Jurassic volcanic rocks and associated plutons (195-176 Ma) [35–40]. These rocks are overlain by Upper Jurassic through mid-Cretaceous marine strata of the Bowser Lake Group [41].Data from rocks of the Stikine terrane are relevant for comparison given that they occur along the eastern margin of the Coast Mountains batholith (Figure 1) and at least locally consist of upper Paleozoic-lower Mesozoic quartz-rich metaclastic strata, marble, and metapelite [35–40]. In addition, Rusmore et al. [9] report geochronologic and paleomagnetic data which they interpret as evidence that intrusive rocks in the study area were emplaced into these inboard assemblages. As shown in Figure 9(b), 380-170 Ma ages in the Bute-Knight pendants overlap to a significant degree with the main phases of igneous activity in the Stikine terrane, as recorded by detrital zircon ages [41] and igneous ages [35–38, 40]. These similarities support the conclusion of Rusmore et al. [9] that the prebatholithic rocks in the study area may belong to inboard terranes (e.g., Stikine terrane or Intermontane superterrane). εHft data that could be used as an additional means of comparison are not available from strata of the Stikine terrane, although the juvenile signatures of Sr and Nd data from rocks of the Stikine terrane [37, 42] suggest that εHft values would likely overlap with juvenile values from the metasedimentary pendants. On the basis of the geologic, geochronologic, and potential isotopic similarities, we conclude that possible correlations with rocks of the Stikine terrane are also supported by our data.The Alexander terrane consists of Neoproterozoic through Upper Triassic rocks that can be divided into three distinct assemblages. Nearest the study area is the Banks Island assemblage, which consists of quartzite, marble, and metapelite that are interpreted to range in age from Ordovician to Permian [3]. As shown in Figures 6(d) and 6(e) of Tochilin et al. [3], this assemblage consists primarily of interlayered quartzite and marble that are very similar to the quartzite-marble assemblage in the study area. The youngest components of the Banks Island assemblage, interpreted to be late Paleozoic in age, occur in pendants of the westernmost Coast Mountains batholith north of Vancouver Island (Figure 1).In southeast Alaska, the Alexander terrane is characterized by Neoproterozoic-Cambrian and Ordovician-Silurian volcanic and plutonic rocks that are interpreted to have formed in juvenile magmatic arc systems [4, 43]. These rocks are overlain by a variety of middle and upper Paleozoic marine strata and an Upper Triassic bimodal volcanic sequence. Rocks belonging to this portion of the terrane are found in much of southeast Alaska and continue southeastward along the western margin of the Coast Mountains batholith, inboard of the Banks Island assemblage, to the central coast of British Columbia (Figure 1).To the north, in the Saint Elias Mountains, the terrane consists of lower Paleozoic mafic volcanic rocks overlain by middle-upper Paleozoic marine clastic strata and limestones and an Upper Triassic rift assemblage [44–46]. Similarities in lithic types, ages of detrital zircons, and εHft isotopic values suggest that the Banks Island assemblage formed adjacent to the Saint Elias Mountains assemblage prior to ~800 km of southward (relative) motion of the Banks Island assemblage in Early Cretaceous time [3, 47]. The Alexander terrane is known to have been located next to Wrangellia by Permian time [48] and most likely Late Devonian time [49].Figure 10 compares the information from Bute-Knight pendants with U-Pb ages and Hf isotope ratios from the Banks Island [3], Saint Elias Mountains [44–46], and southeast Alaska [4, 21] portions of the Alexander terrane. Rocks of the Banks Island assemblage are emphasized in our comparison because they contain abundant quartzite and marble, are at least least locally of late Paleozoic age, and are the closest portion of the Alexander terrane to the study area (Figure 1). The Saint Elias Mountains assemblage is included because it is interpreted to have been adjacent to the Banks Island assemblage during Paleozoic-early Mesozoic time [3]. Geochronologic and isotopic results from the southeast Alaska portion of the terrane are included because these rocks yield similar age distributions and trace southeastward toward the study area.As shown in Figure 10(b), most ages from Bute-Knight metasedimentary rocks are younger than zircon ages from rocks of the Alexander terrane, which is not surprising given that most rocks analyzed from the Alexander terrane are early to mid-Paleozoic in age, whereas strata in this study are interpreted to be upper Paleozoic-lower Mesozoic. Although the proportions of ages are quite different, some age groups overlap, for example, the 560, 452, and 307 Ma age peaks in our samples; 630, 468-441, and 304 Ma age peaks in strata of the Banks Island Assemblage-Saint Elias Mountains; and 574, 446-431, 363, and 288 Ma age peaks in rocks from southeast Alaska. As shown in Figure 10(a), εHft values for older zircons from the Bute-Knight metasedimentary rocks are intermediate between more evolved and more juvenile components of the Alexander terrane. In contrast, εHft values for ~330-280 Ma grains in the pendants and in upper Paleozoic strata of the Banks Island assemblage are nearly identical (filled symbols in Figure 10(a)).These comparisons raise the possibility that Bute-Knight metasedimentary rocks may have primary connections with at least some portions of the Alexander terrane. The strongest similarities are with the upper Paleozoic quartzite-marble unit in the southern portion of the Banks Island assemblage, which occurs north of Vancouver Island and projects southeastward toward the study area (Figure 1). The U-Pb ages and εHft results from these rocks are very similar to values from the Bute-Knight pendants (Figure 10(a)). Other potential connections include the occurrence in both assemblages of 500-400 Ma ages (with somewhat similar εHft values) and 600-550 Ma ages (with very different εHft values) (Figure 10(a)).The Yukon-Tanana terrane consists of Neoproterozoic(?)-lower Paleozoic quartzite, marble, and metapelite overlain by middle Paleozoic volcanic-rich strata and Carboniferous limestone, conglomerate, basalt, and pelitic strata [2, 50]. The Taku terrane consists of Carboniferous strata that are equivalent to upper units of the Yukon-Tanana terrane, plus overlying Permian and Triassic mafic volcanic rocks, pelitic strata, and limestone [1]. Comparison with data from the Taku and Yukon-Tanana terranes is appropriate given that these terranes contain abundant quartzite and marble of Paleozoic and early Mesozoic age [2] and occur along the western flank of the Coast Mountains north of the study area (Figure 1).As shown in Figure 11(b), U-Pb ages from rocks of the Taku and Yukon-Tanana terranes overlap to some degree with the older age groups of the Bute-Knight pendants. As shown in Figure 11(a), however, the Lu-Hf data are quite different, with more juvenile values for >360 Ma grains and more negative values for <360 Ma grains. We accordingly conclude that rocks of the Bute-Knight pendants do not have primary connections with rocks of the Taku and Yukon-Tanana terranes.The geologic, U-Pb geochronologic, and Lu-Hf isotopic relations described above suggest that primary connections with the Yukon-Tanana terrane are unlikely given the very different U-Pb ages and Lu-HF isotope signatures (Figure 11).Connections with the Wrangellia terrane are supported by the similar U-Pb ages and εHft values (Figure 9) but are problematic given the abundance of quartz-rich metasedimentary rocks and scarcity of metabasalt in the pendants versus the lack of quartz-rich clastic strata and abundance of mafic volcanic rocks on Vancouver Island. Primary connections would require significant lateral facies changes between strata of the Karmutsen, Quatsino, Parsons Bay, and Harbledown Formations (in the southwest corner of the study area) and the metasedimentary pendants now tens of km to the northeast (Figure 2).Primary connections with the Stikine terrane are also plausible but are difficult to fully evaluate given the lack of Lu-Hf data from Stikine strata. The occurrence of similar U-Pb ages in the two assemblages and the presence of quartz-rich clastic strata in upper Paleozoic Stikine strata are consistent with the geochronologic and paleomagnetic ties reported by Rusmore et al. [9].An additional possibility, not considered by previous workers, is that the Bute-Knight metasedimentary rocks have primary connections with the Alexander terrane. Although most strata of the Alexander terrane lack quartz-rich clastic horizons and yield primarily >400 Ma detrital zircons, metasedimentary rocks in the southern portion of the terrane consist mainly of interlayered quartzite, marble, and metapelite that yield mainly 400-270 Ma detrital zircon grains with juvenile εHft values (Figure 10(a)). Rocks of the Alexander terrane also contain ~550 Ma and~450 Ma detrital zircons, although εHft values for most of these grains do not overlap with εHft values for grains of these ages in the Bute-Knight pendants. These similarities raise the possibility that the Bute-Knight pendants may be a southeastern continuation of the Alexander terrane.Given the geologic, U-Pb geologic, and Lu-Hf isotopic differences noted above, it is also possible that the Bute-Knight pendants are not correlative with rocks in any of these nearby terranes. Perhaps, connections with more distant Cordilleran terranes will emerge when additional U-Pb geochronologic and Lu-Hf isotopic data become available, or the pendants may be recognized as a distinct terrane. An additional possibility is that the metasedimentary rocks belong to several different tectonostratigraphic units with differing tectonic affinities. Structural boundaries separating the various components may have been obliterated by the widespread plutons that separate the pendants. This possibility is consistent with the observation that the quartzite-marble samples yield a surprisingly broad range of age distributions (Figure 4).As noted above, the available geologic, U-Pb geochronologic, and Lu-Hf isotopic data do not establish or rule out primary connections with the Wrangellia terrane [as suggested by Wheeler and McFeely [6], Wheeler et al. [7], and Journeay et al. [8]] or the Stikine terrane [as suggested by Rusmore et al. [9]]. The available data also raise the possibility that connections may have existed with rocks of the Banks Island assemblage of the Alexander terrane.Given that the Wrangellia and Alexander terranes belong to the Insular superterrane whereas Stikine belongs to the Intermontane superterrane, we are unable to document whether the Insular-Intermontane boundary traces inboard or outboard of the Bute-Knight pendants. The two possible locations for this boundary are shown with dashed lines in Figure 1. This is unfortunate given the tectonic significance of this boundary, as noted above and discussed recently by Pavlis et al. [51].The interpretation that ~50% of the <170 Ma analyses from metasedimentary samples record growth of metamorphic zircon provides an opportunity to use the patterns of age versus U/Th and U concentration to reconstruct the history of metamorphism along the western flank of the Coast Mountains batholith. Such an approach has been used by Rubatto [25], Kirkland et al. [26], Yakymchuk et al. [27], and many others to reconstruct the metamorphic history of other orogens.The patterns shown in Figures 8(a) and 8(b) suggest that metamorphism occurred primarily between ~170 and ~130 Ma and between ~110 and ~87 Ma, with apparent peaks at ~153, ~136 Ma, and ~101 Ma. The younger age range is an excellent match with the main age of metamorphism along the western flank of the Coast Mountains near Prince Rupert (e.g., [52]) and to the north (e.g., [53]). In contrast, evidence for the older phase of metamorphism has been recognized only locally on outer islands northwest of the study area (Figure 1), where [3] report that metamorphic rocks of the Banks Island assemblage are intruded by nondeformed dikes as old as ~156 Ma.The similarity between this interpreted record of metamorphism and the timing of plutonism in the study area [Figure 8; Cecil et al. [11]] suggests that metamorphism was driven largely by heat from the adjacent plutons. The apparent pull-down of εHft values for 165-128 Ma igneous zircons suggests that both metamorphism and plutonism may have been related to Late Jurassic-Early Cretaceous crustal thickening [e.g., Girardi et al. [54], Tochilin et al. [3], Beranek et al. [55]].The analysis of leucocratic sills as well as metasedimentary samples indicates that ~50% of the <170 Ma ages (~28% of the total ages) generated from our metasedimentary samples are igneous in origin. Despite careful examination of the sampled material on the outcrop and inspection of the sampled material during processing, we inadvertently incorporated material from leucocratic sills or veins into several of our samples during collection. This suggests that extreme care must be used when collecting metasedimentary samples in batholithic terranes.Our geologic observations combined with U-Th-Pb geochronologic and Lu-Hf isotopic results lead to several first-order conclusions regarding the tectonic affinity of metasedimentary pendants in the Bute-Knight area: (1)Approximately 2/3 of the U-Th-Pb ages generated from zircons from Bute-Knight metasedimentary samples are <170 Ma, with two main groups of 165-128 Ma (peak age of 152 Ma) and 114-88 Ma (peak age of 102 Ma). These ages match well with the ages of plutons [11] and sills that intrude the metamorphic pendants, which indicates that the <170 Ma ages must record postdepositional igneous and/or metamorphic processes. Conversely, >170 Ma ages in the samples are interpreted to provide a reliable record of the crystallization ages of detrital zircons(2)Most of the >170 Ma detrital zircons in our metasedimentary samples belong to four main groups of 590-528 Ma (peak age of 560 Ma), 485-432 Ma (peak age of 452 Ma), 356-286 Ma (peak age of 307 Ma), and 228-185 Ma (peak ages of 216 and 198 Ma) (Figure 4). Three samples collected from the pelitic schist-quartzite pendant are all dominated by ages between 365 and 285 Ma, with individual age peaks (interpreted to be maximum depositional ages) at 349, 310, and 302 Ma. These maximum depositional ages, combined with the scarcity of ages belonging to the 228-185 Ma group (Figure 4), suggest that these strata accumulated during late Paleozoic time. Samples collected from the quartzite-marble pendants yield a range of ages, with dominant age peaks of 560, 452, 411, 345, 331, 322, 319, 216, 209, and 198 Ma. Maximum depositional ages for these samples include an older group of 345, 341, 333, 331, 322, and 319 Ma ages and a younger group of 246, 216, 209, and 198 Ma ages. The presence of at least a few 228-185 Ma ages in nearly all samples suggests that these strata accumulated during early Mesozoic time. Several samples yield older single-grain ages of approximately 1948, 1845, 1775, 1701, 1429, 1119, and 1109 Ma(3)Many of the <170 Ma analyses yield U concentrations and U/Th values and display zonation patterns in CL images that are similar to values and CL patterns from zircons in leucocratic sills which intrude the metasedimentary rocks. Conversely, many of the young analyses yield higher U concentrations and U/Th values and display convolute zoning in CL images, which suggests that the grains (or in many cases just thin rims) are metamorphic in origin. A comparison of U/Th values (Figure 8(a)) and U concentrations (Figure 8(b)) of analyses of zircons from plutons, leucocratic sills, and metasedimentary samples provides a means of estimating the proportion of metamorphic versus igneous zircon. As shown in Figure 8(a), a cutoff of U/Th=8 suggests that 60% of the analyses record igneous zircon growth, whereas 40% are metamorphic. Instead, a cutoff of U concentration=1100 ppm suggests that 47% of the analyses are igneous and 53% are igneous in origin(4)Given that zircon commonly grows during moderate to high-grade metamorphism [e.g., Rubatto [25], Kirkland et al. [26], Yakymchuk et al. [27]], the age distribution of zircon grains (or rims) that are interpreted to be metamorphic in origin provides an opportunity to reconstruct the metamorphic history in the study area. As shown in Figures 8(a) and 8(b), it appears that metamorphism occurred primarily between ~170 and ~130 Ma and between ~110 and ~87 Ma, with apparent peaks at 153, 136 Ma, and 101 Ma. The occurrence of very similar ages of plutons and sills (Figure 8) raises the possibilities that metamorphism may have been caused mainly by heat related to the adjacent plutons and/or that both metamorphism and plutonism may have resulted from crustal thickening(5)The occurrence of a significant number of <170 Ma zircons in our metasedimentary samples that are interpreted to be of igneous origin demonstrates that most of our samples included igneous material (e.g. felsic veins or sills) that was incorporated during sample collection. This suggests that our procedure of checking the outcrop for igneous material during collection and inspecting each rock fragment during processing was not sufficient to ensure that only metasedimentary material was analyzed(6)εHft values of the zircon grains from metasedimentary samples record a trend from intermediate values (0 to +5; average of +3) for 590-528 Ma grains, through highly variable but generally more juvenile values (+2 to +13; average of +8) for 485-432 Ma grains, to highly juvenile values (mostly +4 to +15; average of +12) for 356-286 Ma and 228-185 Ma grains (Figure 7). εHft values of <170 Ma grains from metasedimentary samples that are interpreted to be of metamorphic origin (e.g., U/Th>8 and U concentration>1100 ppm⁠) remain juvenile (Figure 7), suggesting that the zircons grew during metamorphism of the surrounding (juvenile) metasedimentary rocks. εHft values of <170 Ma grains from sills and from igneous zircons in the metasedimentary samples are less positive for 165-128 Ma ages and return to more juvenile values for 114-88 Ma ages. The slight pull-down of 165-128 Ma εHft values may record melting of more evolved rocks at deeper crustal levels during Late Jurassic-Early Cretaceous time(7)Comparisons of our U-Th-Pb and Lu-Hf results with available data from adjacent terranes (Figures 9–11) indicate that the Bute-Knight pendants have no primary connection with rocks of the Yukon-Tanana terrane but are not sufficient to document or rule out primary connections with the Wrangellia, Stikine, or Alexander terranes. Given that the Wrangellia and Alexander terranes belong to the Insular superterrane, whereas Stikine belongs to the Intermontane superterrane, we are accordingly unable to contribute new insights into the long-standing debate concerning the location, age, and origin of the Insular-Intermontane terrane boundary (e.g., [51, 56])Approximately 2/3 of the U-Th-Pb ages generated from zircons from Bute-Knight metasedimentary samples are <170 Ma, with two main groups of 165-128 Ma (peak age of 152 Ma) and 114-88 Ma (peak age of 102 Ma). These ages match well with the ages of plutons [11] and sills that intrude the metamorphic pendants, which indicates that the <170 Ma ages must record postdepositional igneous and/or metamorphic processes. Conversely, >170 Ma ages in the samples are interpreted to provide a reliable record of the crystallization ages of detrital zirconsMost of the >170 Ma detrital zircons in our metasedimentary samples belong to four main groups of 590-528 Ma (peak age of 560 Ma), 485-432 Ma (peak age of 452 Ma), 356-286 Ma (peak age of 307 Ma), and 228-185 Ma (peak ages of 216 and 198 Ma) (Figure 4). Three samples collected from the pelitic schist-quartzite pendant are all dominated by ages between 365 and 285 Ma, with individual age peaks (interpreted to be maximum depositional ages) at 349, 310, and 302 Ma. These maximum depositional ages, combined with the scarcity of ages belonging to the 228-185 Ma group (Figure 4), suggest that these strata accumulated during late Paleozoic time. Samples collected from the quartzite-marble pendants yield a range of ages, with dominant age peaks of 560, 452, 411, 345, 331, 322, 319, 216, 209, and 198 Ma. Maximum depositional ages for these samples include an older group of 345, 341, 333, 331, 322, and 319 Ma ages and a younger group of 246, 216, 209, and 198 Ma ages. The presence of at least a few 228-185 Ma ages in nearly all samples suggests that these strata accumulated during early Mesozoic time. Several samples yield older single-grain ages of approximately 1948, 1845, 1775, 1701, 1429, 1119, and 1109 MaMany of the <170 Ma analyses yield U concentrations and U/Th values and display zonation patterns in CL images that are similar to values and CL patterns from zircons in leucocratic sills which intrude the metasedimentary rocks. Conversely, many of the young analyses yield higher U concentrations and U/Th values and display convolute zoning in CL images, which suggests that the grains (or in many cases just thin rims) are metamorphic in origin. A comparison of U/Th values (Figure 8(a)) and U concentrations (Figure 8(b)) of analyses of zircons from plutons, leucocratic sills, and metasedimentary samples provides a means of estimating the proportion of metamorphic versus igneous zircon. As shown in Figure 8(a), a cutoff of U/Th=8 suggests that 60% of the analyses record igneous zircon growth, whereas 40% are metamorphic. Instead, a cutoff of U concentration=1100 ppm suggests that 47% of the analyses are igneous and 53% are igneous in originGiven that zircon commonly grows during moderate to high-grade metamorphism [e.g., Rubatto [25], Kirkland et al. [26], Yakymchuk et al. [27]], the age distribution of zircon grains (or rims) that are interpreted to be metamorphic in origin provides an opportunity to reconstruct the metamorphic history in the study area. As shown in Figures 8(a) and 8(b), it appears that metamorphism occurred primarily between ~170 and ~130 Ma and between ~110 and ~87 Ma, with apparent peaks at 153, 136 Ma, and 101 Ma. The occurrence of very similar ages of plutons and sills (Figure 8) raises the possibilities that metamorphism may have been caused mainly by heat related to the adjacent plutons and/or that both metamorphism and plutonism may have resulted from crustal thickeningThe occurrence of a significant number of <170 Ma zircons in our metasedimentary samples that are interpreted to be of igneous origin demonstrates that most of our samples included igneous material (e.g. felsic veins or sills) that was incorporated during sample collection. This suggests that our procedure of checking the outcrop for igneous material during collection and inspecting each rock fragment during processing was not sufficient to ensure that only metasedimentary material was analyzedεHft values of the zircon grains from metasedimentary samples record a trend from intermediate values (0 to +5; average of +3) for 590-528 Ma grains, through highly variable but generally more juvenile values (+2 to +13; average of +8) for 485-432 Ma grains, to highly juvenile values (mostly +4 to +15; average of +12) for 356-286 Ma and 228-185 Ma grains (Figure 7). εHft values of <170 Ma grains from metasedimentary samples that are interpreted to be of metamorphic origin (e.g., U/Th>8 and U concentration>1100 ppm⁠) remain juvenile (Figure 7), suggesting that the zircons grew during metamorphism of the surrounding (juvenile) metasedimentary rocks. εHft values of <170 Ma grains from sills and from igneous zircons in the metasedimentary samples are less positive for 165-128 Ma ages and return to more juvenile values for 114-88 Ma ages. The slight pull-down of 165-128 Ma εHft values may record melting of more evolved rocks at deeper crustal levels during Late Jurassic-Early Cretaceous timeComparisons of our U-Th-Pb and Lu-Hf results with available data from adjacent terranes (Figures 9–11) indicate that the Bute-Knight pendants have no primary connection with rocks of the Yukon-Tanana terrane but are not sufficient to document or rule out primary connections with the Wrangellia, Stikine, or Alexander terranes. Given that the Wrangellia and Alexander terranes belong to the Insular superterrane, whereas Stikine belongs to the Intermontane superterrane, we are accordingly unable to contribute new insights into the long-standing debate concerning the location, age, and origin of the Insular-Intermontane terrane boundary (e.g., [51, 56])The authors declare that there is no conflict of interest regarding the publication of this article.The analyses reported herein were conducted largely by M. Dafov, A. Carrera, and M. Pereira as part of an undergraduate research project at the University of Arizona. Field work and laboratory analyses were supported by NSF EAR award 1347375. Laboratory analyses were also supported by NSF EAR awards 1338583 and 1649254 to the Arizona LaserChron Center. We thank Don Willson for the logistical support of our field work and Mark Pecha, Nicky Giesler, Dan Alberts, Kojo Plange, Martin Pepper, Gayland Simpson, and Ken Kanipe for the assistance with the laboratory analyses.DR Table 1: Information about analyzed samples.

中文翻译：

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南部沿海山区基岩的沉积岩中碎屑锆石的U-Th-Pb年代学和Lu-Hf同位素地球化学

南部海岸山脉岩床的大多数沉积沉积岩具有不确定的构造亲和力，因为它们发生在被大型侵入体包围的不连续垂体中，并且许多原生岩特征被区域变形和变质所掩盖。这项研究使用了Bute，Loughborough和Knight Inlets的准沉积岩中碎屑锆石的U-Th-Pb年龄和Lu-Hf同位素特征，以测试与邻近的Wrangellia，Alexander，Taku，Yukon-Tanana和Stikine地形。来自沉积沉积样品的碎屑锆石的年龄分别为590-528 Ma（峰值年龄560 Ma），485-432 Ma（峰值年龄452 Ma），356-286 Ma（峰值年龄307 Ma）和228-185马（峰值年龄为215和198马）。也存在少量〜1.1-1.9 Ga晶粒。590-185 Ma晶粒的εHft值从中元古代到中生代，从中间（0到+5）值发展到更幼稚（大多数是+4到+15）值。将这些结果与相邻地块的相似数据集进行比较，结果表明与Yukon-Tanana和Taku地块的主要联系不太可能，但与Wrangellia，Stikine和/或Alexander地块的主要联系是一致的。不幸的是，可用的约束条件不足以消除这些选项中的任何一个，也无法消除垂饰是独特的构造碎片的可能性。沉积沉积样品中的锆石还产生U-Th-Pb年龄为165-128 Ma（峰值年龄为152 Ma）和114-88 Ma（峰值年龄为102 Ma）。这些锆石结构域的εHft值大多为青少年（+7至+13）。铀浓度比较 变质沉积样品中的锆石的U / Th值和CL质构，侵入垂坠的白垩纪基岩以及周围的深部小体表明，大多数新晶粒以及较旧晶粒上普遍分布的较年轻的轮缘在与位置相关的变质过程中生长相邻的岩体。一些年轻的谷物是从稀疏的长裙梁或脉中获得的，这些长石是不经意地包含在样本材料中的。不列颠哥伦比亚省西部和阿拉斯加东南部的沿海山脉主要是侏罗纪，白垩纪和第三纪早期的青藏岩，侵入了各种变质沉积和变火山岩。岩石（图1）。在北部和中部沿海山脉，根据岩性特征，结合U-Th-Pb年代学和碎屑锆石的Hf同位素分析，重建了沉积沉积和变火山垂体的构造亲和力[1-5]。从西向东，主要的地层/组合包括亚历山大，塔库，育空-塔纳纳和斯蒂基因地体（图1）。南部海岸山脉中的沉积沉积组合的构造亲和力最初是根据Wheeler的原生岩特征来分配的和McFeely [6]，Wheeler等。[7]，和Journeay等。[8]（图1）。成分被解释为包括Wrangellia地层（Insular上层地层）的古生界和下中生界岩石，Gambier组的上侏罗统-下白垩统火山岩和碎屑岩以及亲和力不确定的变质岩。最近，Rusmore等人。[9]提出了海岸山脉这一部分的岩石属于山间超地带的内侧地层（例如Stikine地层）的可能性。考虑到山际上空的内侧岩石很可能在科迪勒兰边缘附近形成并演化，而岛屿上空的外侧岩石可能在古北极海洋盆地中形成，因此区分这两种可能性非常重要。这项研究试图通过提供从碎屑锆石中提取的U-Th-Pb年代学数据和Hf同位素数据，来评估这些构造亲和力以及与附近的Alexander或Yukon-Tanana / Taku地层的可能联系，和Knight Inlets（图1）。沿着Bute，Loughborough，Knight和相关较小入口的冰川冲刷和波浪冲刷的峡湾壁，海岸线深处的岩基岩显露出来（图2）。正如塞西尔等人报道的。[11]，该地区的岩蜡岩主要由闪长岩，色泥岩和粒二闪岩体和侵入性复合体组成，年龄从〜170 Ma到〜85 Ma不等。沉积沉积和变火山岩以高度细长的悬垂物的形式出现，分隔悬垂的云母也为西北偏东南[11]。吊坠的宽度变化很大，大多数在10s至100s米的数量级，但有些则超过一公里。所有岩石均强烈地平行于悬垂线边缘，除了该区域中最年轻的岩屑外，所有岩石均平行于叶面（图3（a））。研究区的准沉积和超火山岩被分为三部分，分别具有不同比例的石英岩，大理石，片岩片岩和偏玄武岩，第四部分则缺乏这些岩性联系，仅由细粒的超碎屑岩和准火山岩组成（图2）。这四个组合都完全位于属于Wrangellia地层的Karmutsen，Quatsino，Parsons Bay和Harbledown地层的低级沉积和火山岩的东部（[12，13]；图2）。在研究区域的西南部和上骑士入口处，发现了垂饰，其主要由层状石英岩和大理石组成（图3（b）），并带有下级的片岩片岩和局部的钙硅酸盐。分层尺寸为1-3厘米，石英岩通常比大理石丰富。石英岩层非常纯净，几乎仅由石英和方解石组成。对这些岩石进行碎屑锆石采样是具有挑战性的，因为大多数露头都被成群的侵入侵入，这些侵入以几厘米厚的顶梁出现。在大多数情况下，这些岩体共享其宿主岩中表现出的区域叶状结构。在罕见的暴露中，可以看到它们以倾斜的角度跨过沉积沉积层侵入。第二个组合是从西北向东南穿过上部的Bute入口，由黄土片岩和石英岩组成，它们以cm的比例夹层（图3（c）） ）。与上述单元类似，夹层石英岩和大理石是该组件的次要组件。在大多数露头中 在薄（厘米厚）的石英岩层上，胶生岩片岩占主导地位（图3（c））。石榴石有一些露头。这些吊坠还包括叶状白垩纪门槛，但很容易与占优势的骨质宿主岩区分开（例如，图3（c））。第三个组合由两条玄武岩带和下级大理石带组成，它们出现在Bute和Knight Inlets中（图2）。这些层存在于石英岩和大理石为主的层序附近，但无法确定与相邻单元的连续性。偏玄武岩占主导地位，局部观察到枕头。米厚的白色大理石层与偏玄岩层之间局部夹层。第四类​​组合遍及研究区域的中部，由几个悬垂物组成，这些悬垂物主要是中间组成的准火山岩，具有次要的沉积层。大多数中火山岩为凝灰质，夹层有细粒火山岩。几个露头还包括较厚的地层，显示出残缺的枕头和碎片状纹理。在该组合中没有发现石英岩，大理石或片状片岩，表明这些岩石具有明显的构造地层单元。以前的大多数工作人员认为，研究区的变质岩属于Wrangellia地层和Gambier上覆地层。组（图1）。Journeay等。[8]将上述石英岩-大理石-亚辉石-玄武岩组合物分配给了Karmutsen组，它主要由三叠纪玄武岩流和在温哥华岛大部分地区暴露的次要沉积单元组成（图1）。广泛的三叠纪玄武岩是Wrangellia地貌的标志之一[14，15]。Roddick和Woodsworth [16]扩展了这项研究的范围，包括某些原生生物可能是古生代（Karmutsen以前）的可能性。研究区中部出现的富火山岩被指定为下白垩纪甘比尔群。 Journeay等。[8]和罗迪克和伍德斯沃思[16]。Gambier组被解释为沿Wrangellia地表的内侧边缘积累的盆地弧[17，18]。[9]建议研究区域中的悬垂物可能属于沿海山脉内陆的地形（例如，（Stikine地貌）（1）出现具有明显早白垩纪年龄的云母，向北侵入云层的Stikine地岩，以及（2）研究区的云母的古磁倾角与内侧相似收集并分析了17个样品，以测试上述解释。大多数样品是从富含石英的岩层中收集的，这些岩层是基于镁铁质矿物含量低，厘米级的大理石和/或胶粒岩片岩夹层以及与相邻成分层的横切关系而被解释为超碎屑的。如上所述，收集沉积沉积样品中的挑战之一是常见的叶状白屑基岩现象，类似于低色指数的富含石英的碎屑岩层，方向（通常与分层平行），叶和纹的发育程度以及耐候性。为了确定我们的沉积沉积样品是否还包含火成岩物质，我们收集了三个白细胞基层样品，以作比较参考。在沉积沉积的和沉积沉积的样品中识别出具有相似年龄和H同位素特征的锆石，表明我们沉积沉积的样品中含有无法识别的火成岩。相反，在沉积沉积样品中，比侵入体（和周围的岩体）更早的颗粒将被确信地解释为碎屑成分。窗台的年龄也为准沉积物垂饰提供了最小的沉积年龄。每个样品收集大约5-10公斤的岩石。样品在DR表1中进行了描述；位置如图2所示。在研究区域中花费了相当多的时间来检查超火山垂体（图2）。然而，由于稀有的碎屑岩地层的粒度细，石英成分差，因此没有从这些地层中收集样品。样品在Georges LaserChron中心使用Gehrels [19]的方法进行处理和分析。[20]，塞西尔等。[21]，Gehrels和Pecha [22]，以及Pullen等。[23]（https://www.laserchron.org）。用颚式破碎机和辊磨机提取锆石，然后用Wilfley工作台将其与轻质矿物分离。用Frantz LB-1磁障分离器和二碘甲烷进一步分离得到的重质矿物馏分。将每个样品中的数百粒谷物与三个用于U-Th-Pb分析的锆石标准品（斯里兰卡，FC-1和R33）以及六个锆石标准品（R33，Mud Tank，FC-1，Plesovice，Temora2和91500）用于Lu-Hf同位素。座架被抛光至约20微米的深度，以揭示晶粒内部，然后用连接到Hitachi S-3400N扫描电子显微镜的背向散射电子（BSE）和阴极发光（CL）检测器系统进行成像。 -Pb分析是通过使用与Nu multicollector ICPMS [20，22]或Element2 Single-collector ICPMS [23]连接的Photon Machines G2准分子激光通过激光烧蚀电感耦合等离子体质谱法（LA-ICPMS）进行的。对于最初的分析，Element2 ICPMS用于分析每个碎屑样品中的110至315个锆石晶粒和每个火成岩样品中的〜35个锆石晶粒。使用20微米的激光束直径对每个谷物分析一个斑点。在DR表2中报告了详细的分析方法。在DR DR表3中报告了U-Th-Pb分析的结果。如下所述，第一组分析得出的年龄分别为151、150、150、104和104。白带基层样本为102 Ma，元沉积样本的年龄范围为〜1948〜88 Ma。与基石年龄重叠的沉积沉积样品中出现的年龄表明，在采集过程中可能已将火成岩物质掺入样品中和/或年轻年龄记录了变质锆石的生长。为了区分这两种解释，以下几节探讨了分析晶粒的CL特性[如Corfu等人所述。[24]以及它们的Hf同位素特征，U浓度和U / Th值。关于后者，我们遵循Rubatto [25]，Kirkland等。[26]，以及Yakymchuk等。[27]在认识到变质锆石通常比火成锆石具有更高的U浓度和更高的U / Th。我们也将我们的数据与附近的古生物体的值进行了比较，假设在沉积沉积样品中可能存在其他年龄的基石。在进行这些比较时，考虑到研究区的沉积物垂体被约167Ma的胶体侵入，我们用170 Ma作为可能起源于碎屑的较粗晶粒与可能是火成岩和/或变质的较年轻晶粒的分界。并产生约185 Ma至165 Ma的几个年龄。为了进一步探索某些被分析域是起源于变质的可能性，我们进行了第二组分析，涉及获取高分辨率CL图像以检查晶粒纹理。并对在CL图像上识别的每个域进行U-Th-Pb分析。这些年龄图分析是通过使用10微米激光束直径的Nu multicollector ICPMS进行的。对每种谷物进行了5到33次分析。斑点位置由分析后的BSE图像确定。在DR表2中报告了分析程序的详细信息，在DR表3中报告了分析结果。根据解释，认为> 170 Ma的晶粒是来自准沉积样品的锆石的U-Th-Pb年龄总结在图4中。碎屑和<170 Ma的晶粒起源是火成岩和/或变质的。最大沉积年龄由概率密度图上的峰值年龄确定[例如，Gehrels [19]，Dickinson和Gehrels [28]，Gehrels [22]]。图5通过比较三个白垩纪基岩，这些基岩侵入的准沉积岩和附近的云母的锆石的年龄与U / Th的比值来探究<170 Ma晶粒的起源。图6显示了一些通过年龄映射分析的信息量更高的谷物的图像和年龄信息。利用Cecil等人报道的方法进行Hf同位素分析。[21]和Gehrels和Pecha [22]，使用DR表2中报告的设置。对每个样品的每个年龄组的谷物进行了分析。使用40μm激光束进行Hf分析，Hf凹坑位于U-Th-Pb凹坑的顶部。这增加了U-Th-Pb和Hf数据来自同一年龄域的可能性。所有Hf同位素数据均列于表DR 4中，包括每个样品的Hf演化图。图7显示了所有样品的Lu-Hf同位素数据。该图以εHft报告数据，即结晶时相对于软骨均匀储层（CHUR）的176Hf / 177Hf比[29]。该图还显示了来自Vervoort和Blichert-Toft的枯竭地幔阵列（DM）[30]和平均陆壳的Hf同位素演化，其基于0.0115的176Lu / 177Hf比[31，32]。我们的测量平均精度为2.2ε单位（在2σ处）。如上所述，如图4所示，几乎所有的沉积沉积样品均产生<170 Ma的晶粒，并与附近胶体的年龄重叠，并且> 170 Ma谷物被认为是有害的。每组年龄在下面的单独部分中进行描述。从石英岩和大理石为主的垂饰中收集的十二个样品产生的年龄段的可变比例从〜590 Ma到〜185 Ma，每个样品的主要峰值年龄为560、452， 411、345、331、322、319、216、209和198 Ma（图4）。胶粒岩片岩-石英岩垂饰的三个样品主要由370-270 Ma范围内的晶粒组成，主要年龄峰值为349、310和302 Ma。综合所有年龄段（图4的上部曲线），有四个主要年龄段：590-528 Ma（峰值年龄560 Ma），485-432 Ma（峰值年龄452 Ma），356-286 Ma（峰值年龄） 307 Ma）和228-185 Ma（峰值年龄分别为216和199 Ma）。尽管每个样本仅由其中一个年龄组的谷物占主导，但大多数样本包含其他年龄组的从属种群：三个样本的年龄在590-528 Ma之间，五个样本的年龄在485-432 Ma之间，十三个样本的产量为356 -286 Ma年龄，十二个样本包含228-185 Ma年龄。最大沉降年龄是为准沉积初生岩分配的，其中最可靠的年龄是由至少三个年龄最小的年轻群体确定的，这些年龄在2-sigma不确定度内重叠[28]。这对三个胶质片岩-石英岩样品产生的最大沉积年龄分别为349 Ma，310 Ma和302 Ma，随着年龄的增加，整个悬垂物向东北逐渐减小（图2）。南部垂体的石英岩-大理石样品的最大沉积年龄为345、341、319和216 Ma，北部垂体的最大沉积年龄为333、331、322、209和198 Ma。鉴于六个最大沉积年龄大于300 Ma的样本中有四个也包含250至170 Ma的单个年龄，很可能所有石英岩-大理石样本都在250 Ma之后累积。在两个石英大理石垂饰之间或之间没有明显的占主导或最大沉积年龄的空间格局。比较黄铁片岩-石英岩和石英岩-大理石垂体的最大沉积年龄，表明黄铁片岩-石英岩原生岩可能在古生代晚期积累，而石英岩-大理石原生岩可能在三叠纪-早侏罗世时期积累。除了这些<590 Ma的年龄外，在石英岩-大理石样品中还发现了六个较老的晶粒，年龄分别为〜1948，〜1845，〜1775，〜1701，〜1429和〜1109 Ma。黄土片岩片岩-石英岩组合的样品中仅发现一个〜1119 Ma的年龄，所有石英岩-大理石样品，以及三大片岩片岩-石英岩样品之一，也产生了大量的<170 Ma年龄（图4）。大多数样本显示两组年龄范围从165到128 Ma，从114到88 Ma。如上所述，考虑到吊坠被约167 Ma的云母侵入，这些年龄不能算是有害的。以下各节重点介绍了可用的U-Th-Pb，U / Th，U浓度和CL纹理信息，这些信息限制了这些年轻晶粒的起源。首先描述来自三个具有火成岩和沉积沉积样品的垂体的信息，为没有火成岩样品的垂体提供解释性指导。图5总结了白垩纪基岩和基质岩石沉积沉积物中锆石的年龄，U浓度和U / Th值。三个露头的样本。本节中显示的结果来自我们的第一组分析，该分析包括对每种谷物的一次分析。对于每个样本，年龄模式 对U浓度和U / Th进行了评估，以区分年龄和年龄的变质沉积样品是否记录了火成岩和变质结晶。在区分两者时，我们遵循Rubatto [25]，Kirkland等人的观点。[26]，以及Yakymchuk等。[27]在解释中，变质锆石通常比火成锆石具有更高的U浓度和更高的U / Th值。对于局部15KN63（图5（a）和5（b）），火成样品（15KN63C）产生30-两个年龄较小的人（约104 Ma的峰值年龄）和三个年龄较大的人（约149 Ma的峰值年龄）（DR表3）。这三个年龄较大的年龄来自CL图像中清晰可见的核心。来自两个年龄组的分析均得出相对较低的U浓度和U / Th值，这表明所有分析域的来源均为火成岩。该露头（15KN63A和B）的沉积沉积样品中的锆石产生相似的年龄组（峰值年龄为〜153和〜104 Ma），其中较大年龄段的比例更高。大多数年轻的晶粒产生的U浓度和U / Th值暗示着火成岩的结晶，而一些较旧的晶粒产生的高值暗示了变质的结晶。对于局部15KN68（图5（c）和5（d）），火成样品（ 15KN68B）的年龄较大，年龄也较小，峰值年龄约为102 Ma（主要来自边缘）和151 Ma（从属主要来自岩心）（DR表3）。也有一些岩心产生较大的碎屑年龄。该样品中所有晶粒的U浓度和U / Th值都是火成锆石的典型特征。该露头的沉积物样品具有相似的年龄段，大多数年龄段的最高年龄段定义为〜153 Ma，而较小年龄段的最高年龄段定义为〜107 Ma。少数年龄较大的碎屑颗粒年龄范围为〜1109〜〜173 Ma。大多数晶粒的U浓度和U / Th值较低，表明存在火成岩结晶，尽管有些范围较高，表明存在变质结晶。对于局部15KN69（图5（e）和5（f）），火成样品（15KN69B ）仅产生一个主要年龄组，其峰值年龄为〜149 Ma，加上两个较早的核心年龄〜215和〜365 Ma（DR表3）。沉积沉积的样品15KN69A产生的亚种比例的老粒和幼粒（峰值在〜149和〜92 Ma）。从火成岩和沉积沉积样品中进行的大多数分析均显示出低的U浓度和U / Th值，表明存在火成岩结晶。在大多数其他沉积物样品中也发现了170 Ma年龄（图4）。对这些晶粒的分析得出的年龄，U浓度和U / Th值如图5（g）和5（h）所示。这些样品产生年龄在167至125 Ma（峰值在〜150和〜142 Ma之间）和115至84 Ma（峰值在〜101 Ma）之间的亚等比例的晶粒。大多数U / Th值很低，并且可能是火成岩，但是相当大的U / Th值与变质成因一致。为了进一步限制这些样品中<170 Ma晶粒的成因，我们进行了年龄-对来自五个样品（一个火成岩和四个次沉积岩）的16个锆石晶体进行作图分析。DR表2和3中提供了这些分析的详细信息。图6总结了我们的发现结果，其中一个来自白垩纪基岩的晶粒记录了〜101 Ma的火成岩结晶，两个沉积岩样品的记录了〜151和〜104 Ma的火成岩结晶，以及两个沉积岩样品的解释了记录了〜155 Ma的变质结晶。图6（a）和6（b）所示的谷物来自侵入白云沉积岩（15KN63A和B）的白垩阶基岩（15KN63C）。在CL图像中看到的振荡和扇形区划（参见Corfu等人，2013）以及较低的U / Th值表明该谷物起源于火成岩，年龄约为101 Ma。图6（c）和6（d）显示了来自主体准沉积岩的晶粒（样品15KN63A），具有相似的振荡带，年龄为〜104 Ma，典型的火成U / Th平均值为〜3.0。这两种谷物在特性上的相似性表明，沉积沉积样品15KN63A包含来自一个或多个白垩基块的无法识别的火成物质。图6（e）和6（f）所示的颗粒来自沉积沉积样品15KS51。该谷粒的核心高度分解，年龄为236-198 Ma（平均〜212 Ma），周围是平均年龄为〜103 Ma的轮辋。外缘的回旋纹理（参见[24]），结合U / Th值为46-14（平均〜24.2），表明该晶粒记录了白垩纪中期变质锆​​石的生长。图6（g）和6（h）中的“二元”也来自沉积沉淀样品15KN63A。它具有回旋区带和低U / Th值，类似于图6（c）和6（d）所示的晶粒，但其年龄约为151 Ma。这种谷物的出现，以及其他具有类似特性的矿床（DR表2和3）表明，一些侏罗纪火成岩样品中也存在晚侏罗世的火成岩成分，而图6所示的谷粒则暗示了其他晚侏罗世晶粒的变质起源。 i）和6（j），其来自沉积沉积样品15KN73。该谷物包含平均年龄为〜559 Ma的核心和平均年龄为〜155 Ma的轮辋。U / Th值表明核心起源是火成岩，而边缘在区域变质过程中生长。两者之间是一个中间区域，其年龄范围从457到230 Ma，大概是由于分析了来自较旧和较年轻区域的物质混合物所致。这种谷物显示的关系表明，某些侏罗纪晚期锆石的起源是变质的。图8（a）和8（b）给出了样品位点附近的沉积沉积样品，白垩纪基岩和p的锆石的年龄，U / Th值和U浓度的比较[Cecil等人的。数据。[11]。白蚁基岩和邻近的plutons的年龄，U / Th值和U浓度的重叠表明该基石与邻近的plutonic体在遗传上相关。准沉积样品和白垩纪基岩中锆石的年龄，U / Th值，U浓度和CL质地相似，表明我们的准沉积样品中的许多谷物都是火成岩，尽管仔细地选择了它们，但仍无意中将其掺入了样品中。露头和样品处理过程中的材料。在随后的检查中，在样品15KN73的手部样品中发现了一条5毫米宽的lite骨静脉-在该样品和其他样品中类似的静脉可能是火成物质的来源。在某些全谷物和许多谷物的边缘发现较高的U / Th值，U浓度和回旋的CL织构表明还存在变质锆石。考虑到东北坠子中存在石榴石，这些样品中存在变质锆石并不令人惊讶。鉴于高U / Th和高U浓度的锆石（或锆石边缘）起源是变质的解释，如图所示解释图8（a）和8（b）以提供研究区域中变质作用的时空分布记录。假设U / Th值8是火成锆石与变质锆石生长的合理截止值（图8（a）），1074个分析中的425个（〜40％）是起源变质的。尽管我们不能假设新的锆石生长与所有变质事件有关，但这些数据表明，变质发生在〜111和〜90 Ma之间，峰值出现在106、101和92 Ma之间，以及〜171和〜127 Ma之间，在153和136 Ma达到峰值。假设1100 ppm的U浓度对于火成锆石和变质锆石生长是一个合理的临界值（图8（b）），那么1074次分析中的572个（〜53％）是起源变质的。变质似乎发生在〜115 ~~ 86 Ma之间，峰值出现在107、101和93 Ma之间，〜168 ~~ 131 Ma之间，峰值出现在152和136 Ma之间。我们的沉积沉积和火成岩样品的εHft值是如图7所示。分别显示> 170 Ma分析，这些分析被认为是有害的，而< 170 Ma的白细胞基岩与沉积物样本的分析。后者又分为U / Th> 8（被认为是变质成因）与U / Th <8（被认为是火成岩）的分析。从超沉积样品的分析得出，从更多演化到随着时间的流逝变得更加年轻。如图7所示，εHft值的滑动窗口平均值从590-528 Ma晶粒的约3增加到485-432 Ma晶粒的约8到356-286 Ma晶粒的约12。这被解释为记录了随着时间的推移，少年材料的比例逐渐增加。在228-185 Ma的晶粒中，εHft值会随着时间的推移保持少年状态。170 Ma晶粒显示165-128 Ma晶粒的平均值稍低，然后返回114-88 Ma晶粒的较幼稚的值。对于165-128 Ma的分析，被认为是火成岩的谷粒（基岩和低U / Th的沉积样品中的谷物）的εHft值比被认为是变质成因的谷物的εHft值更负（图7）。 ）。这表明，与火成岩起源的晶粒相比，变质起源的晶粒（或边缘）的来源不同。假设变质锆石生长在目前暴露的地壳水平，而火成锆石主要生长在更深的地壳水平（产生岩浆），火成锆石的负εHft值的出现可能反映了在165-128 Ma岩浆作用下较低地壳水平上存在更多地演化的地壳物质。一种可能是这些演化程度更高的地壳物质包括从我们的样品中衍生出600-400 Ma晶粒的岩石（图7）。由于与其他矿物的相互作用，变质锆石比火成锆石产生更高的εHft值（ （例如磷灰石或闪石）。〜165-128 Ma和〜114-88 Ma年龄的火成岩和变质晶粒产生相似的范围和平均值176Lu / 177Hf（DR表5）的观察结果不支持这种解释（DR表5）。图9-11和以下各节中的相关地形。考虑到之前的解释，Bute，Loughborough和Knight Inlets中的垂线是属于这些地层的变质等价物，因此最适合比较的是Wrangellia和Stikine地层。我们还将与（1）亚历山大地层（发生在研究区域以北的海岸山脉外侧）和（2）Taku和Yukon-Tanana地层（发生在海岸山脉的西部侧面以及沿海岸的侧面）进行比较。如Yorath等人所述，Wrangellia的温哥华岛部分位于研究区域的北部（图1）。[15]和Ruks [14]包含数个古生界岩石，包括Sicker集团的上泥盆统-下密西西比（366-336 Ma）双峰火山岩，密西西比-宾夕法尼亚州的泥质，页岩，石，石灰石，第四湖和赛尔伍德组的砂岩，宾夕法尼亚州的上至下二叠纪（312-292 Ma）大部分为长英质火山岩，而巴特尔湖组的下中二叠统碳酸盐岩。这些岩石覆盖着区域广泛的覆盖层，覆盖范围从中到旧，由中三叠纪玄武岩和上三叠纪玄武岩（Karmutsen组），厚层到大块的石灰岩（Quatsino组），薄层粉砂岩，页岩和石灰岩（帕森湾地层）。这些岩石上覆有Bonanza组的下侏罗纪（〜200-170 Ma）玄武质至流纹岩火山岩和下级富火山沉积岩[15，33]。不整合地覆盖上白垩统砾岩，砂岩，泥岩，以及纳奈莫群的页岩[15]，其基础单元包含丰富的〜400-170 Ma碎屑锆石颗粒，这些颗粒被解释为源自兰格利亚的岩石[34]。侵入性组件包括泥盆纪最晚的密西西比盐泉侵入套件[359-356 Ma; Ruks [14]和侏罗纪早期-中期入侵[190-165 Ma; DeBari等。[33]。在研究区（图2）中，沿着兰格利亚东部边缘的地层[12，13]包括以下，从最老到最年轻：（i）〜6 km的巨大熔岩流，枕形玄武岩和Karmutsen组（上三叠纪）的碎裂角砾岩（ii）Quatsino组（上三叠纪）的厚层至块状灰色石灰岩为0-800 m（iii）高达600 m的上覆钙质粉砂岩，页岩，graywacke，（上三叠纪）的帕森斯湾组的石灰岩和石灰岩（iv）高达500 m的Harbledown组（侏罗纪下层）的黑色泥质和次细粒度的灰色古怪〜6 km的巨大熔岩流，枕形玄武岩和碎裂角砾岩Karmutsen组（上三叠统）0-800 m的Quatsino组（上三叠统）厚层至块状灰色石灰岩高达600 m的帕森斯湾组（上组）钙质粉砂岩，页岩，灰瓦克和石灰岩的上覆层惠勒和麦克费利[6]，惠勒等人，哈里斯唐组（下侏罗统）最多有500 m的黑泥质和次要细粒灰泥。[7]，和Journeay等。[8]提出，垂体中的准沉积和准火山岩是属于兰格利亚的地层的变质等价物，我们的实地研究不支持这些相关性。主要区别在于（1）先前在温哥华岛（或兰吉利亚州的任何其他部分）的研究中未描述石英岩-大理石组合的原生岩，并且在我们对该研究中属于兰吉利亚州的下中生界地层的详细制图过程中未发现区; （2）在研究区，温哥华岛或兰吉利亚州其他任何地方，也没有发现用于胶状片岩片岩-石英岩组合的原生石；（3）镁铁质至中层组成的火山岩在温哥华岛（以及Wrangellia的大多数其他地区）分布广泛，但在研究区的垂线中仅占很小的比例。与这些地质差异相反，我们的U-Pb年龄和H同位素的结果与温哥华岛的结果非常相似，其中包括古生代火成岩上的U-Pb年龄[14]和来自第四湖的密西西比-宾西尔瓦尼亚砂岩层和Thelwood组的碎屑锆石中的碎屑锆石和U-Pb / Lu-Hf数据Nanaimo集团的成员[34]。作为该项目的一部分，我们试图通过分析Karmutsen，Quatsino，Parsons湾和Harbledown地层中的碎屑锆石来补充这些结果（图2），但无法确定任何这些单元中富含石英的碎屑岩层。Harbledown组最粗糙的灰色瓦克层位的两个样本未能产生足够大小的锆石用于分析。来自Ruks [14]和Alberts等的数据。[34]总结在图9中，下部面板的火成岩和碎屑锆石的年龄分布和上部面板的碎屑锆石的εHft值.Bute和Knight Inlet的准沉积岩的U-Pb（锆石）年龄与该地区火成岩和沉积岩的年龄有很大的重叠。紫兰（图9（b））。两组均显示两个主要年龄组，在Bute-Knight垂饰上的年龄高峰分别为307、215、198和179 Ma，碎屑的年龄高峰为341、195和171 Ma，年龄高峰为357、308， 199和176 Ma（来自Wrangellia的火成岩）。最令人印象深刻的是Bute-Knight吊坠和温哥华岛火成岩的几乎相同的年龄高峰307-308 Ma和198-199 Ma。两种碎屑锆石数据集还包含散布的> 400 Ma晶粒，来自Bute-Knight垂饰的年龄高峰分别为560和452 Ma，但温哥华岛则没有明显的群体。两个区域中<400 Ma晶粒的εHft值也相似，两者的少年值都很高（图9（a））。基于这些比较，我们得出结论，研究区的准沉积和准火山岩可能具有温哥华岛上古生界-下中生界地层的主要连接。这种连接需要地层发生明显的横向变化，包括向东增加富含石英的碎屑岩层，并减少火山岩的比例和范围.Stikine地层由泥盆纪石灰岩和海相碎屑岩层组成，上泥盆统-下层密西西比火山岩及相关的380-345 Ma岩体，密西西比州镁铁质火山岩和海相地层，宾夕法尼亚州双峰火山岩（319-312 Ma），二叠纪碳酸盐岩，中上三叠世火山岩及其伴生岩体（226-200 Ma）和侏罗纪中下火山岩及其伴生岩体（195 -176 Ma）[35-40]。这些岩石被上侏罗统覆盖到Bowser湖群的白垩纪中期海相层[41]。Stikine地层岩石的数据与它们相关，因为它们发生在沿海山脉岩基的东部边缘（图1）。至少局部由上古生界—下中生界石英富集碎屑岩，大理石和变质岩组成[35-40]。此外，Rusmore等。[9]报告了年代学和古地磁数据，他们将其解释为研究区域的侵入性岩石被置于这些内侧组合中的证据。如图9（b）所示，Bute-Knight垂饰的380-170 Ma年龄与Stikine地层中火成岩活动的主要阶段显着重叠，如碎屑锆石年龄[41]和火成岩年龄[41]所记录。 35–38，40]。这些相似之处支持了Rusmore等人的结论。[9]研究区的前岩性岩石可能属于内侧地层（例如，Stikine地层或Intermontane上层地层）。尽管Stikine地层岩石中的Sr和Nd数据具有青少年特征，但从Stikine地层中无法获得可作为比较手段使用的εHft数据[37，[42]认为εHft值可能与后沉积沉积物的少年值重叠。根据地质，年代学和潜在的同位素相似性，我们得出的结论是，我们的数据也支持了与Stikine地层的岩石的可能相关性.Alexander地层由新元古代至上三叠纪岩石组成，可分为三个不同的组合。最靠近研究区域的是班克斯岛组合，它由石英岩，大理石和变质岩组成，其年龄范围从奥陶纪到二叠纪[3]。如Tochilin等人的图6（d）和6（e）所示。[3]，这种组合主要由夹层石英岩和大理石组成，与研究区域的石英岩-大理石组合非常相似。班克斯岛组合中最年轻的部分，被认为是古生代晚期，出现在温哥华岛以北最西端的沿海山脉岩基的垂体中（图1）。在阿拉斯加东南部，亚历山大大地带的特征是新元古代-寒武纪和奥陶纪-被解释为在青少年岩浆弧系统中形成的Si留系火山岩和深成岩[4，43]。这些岩石被各种中，上古生界海相地层和上三叠统双峰火山序列所覆盖。属于此部分的岩石在阿拉斯加东南部的大部分地区发现，并沿着不列颠哥伦比亚省中部海岸的班克斯岛组合内侧的海岸山脉岩基的西边缘向东南延伸（图1）。在圣伊莱亚斯山脉，地层由下古生界镁铁质火山岩覆盖，中上古生界海相碎屑岩和石灰岩以及上三叠统裂谷组合[44-46]。岩性类型，碎屑锆石的年龄和εHft同位素值的相似性表明，在早白垩世时期，班克斯岛组合向南（相对）运动约800 km之前，与圣埃利亚斯山组合相邻形成的班克斯岛组合[3]。 ，47]。已知亚历山大山脉在二叠纪[48]和最可能是泥盆纪晚期[49]位于兰格利亚附近。图10比较了来自Bute-Knight垂体的信息与U-Pb年龄和两岸的Hf同位素比。亚历山大山脉的岛屿[3]，圣伊莱亚斯山脉[44-46]和阿拉斯加东南[4、21]部分。我们的比较中强调了班克斯岛组合的岩石，因为它们包含丰富的石英岩和大理石，至少在古生代晚期是局部的，并且是亚历山大地层最靠近研究区域的部分（图1）。之所以包括圣伊莱亚斯山脉组合，是因为它在古生代-中生代早期就被认为与班克斯岛组合相邻[3]。包括该阿拉斯加东南部地区的年代学和同位素结果，因为这些岩石具有相似的年龄分布并向东南向研究区域追溯。如图10（b）所示，Bute-Knight沉积沉积岩的大多数年龄都比锆石年轻。历经亚历山大地带的岩石 考虑到从亚历山大山地带分析的大多数岩石年龄都在古生代的早期到中期，这并不奇怪，而本研究中的地层被解释为上古生界-下中生界。尽管年龄的比例差异很大，但某些年龄组重叠，例如，样本中的560、452和307 Ma年龄峰值；Banks Island Assemblage-Saint Elias山地层的630、468-441和304 Ma年龄峰；阿拉斯加东南部岩石中的574、446-431、363和288 Ma年龄峰值。如图10（a）所示，Bute-Knight沉积沉积岩中较老的锆石的εHft值介于亚历山大地层的更多演化和更多幼年成分之间。相反，班克斯岛组合的垂饰和上古生界地层中〜330-280 Ma颗粒的εHft值几乎相同（图10（a）中的实心符号），这些比较增加了Bute-Knight准沉积岩可能具有初级与Alexander Terrane至少某些部分的连接。最强烈的相似之处是与班克斯岛组合南部的上古生界石英岩-大理石单元，该单元位于温哥华岛以北，向东南延伸至研究区（图1）。这些岩石的U-Pb年龄和εHft结果与Bute-Knight悬垂物的值非常相似（图10（a））。其他潜在的联系包括500-400 Ma年龄（εHft值有些相似）和600-550 Ma年龄（εHft值非常不同）的组合（图10（a））。Yukon-Tanana地层包括新元古代（？）-下古生界石英岩，大理石和变质岩被中古生代富火山岩层和石炭系石灰岩，砾岩，玄武岩和胶生岩层所覆盖[2，50]。塔库地层由相当于育空塔纳纳地层上部的石炭纪地层，上覆的二叠纪和三叠纪镁铁质火山岩，古生岩地层和石灰岩组成[1]。考虑到Taku和Yukon-Tanana地层中含有丰富的古生代和中生代石英岩和大理石[2]，并且这些地层沿研究区以北的海岸山脉西侧出现，因此比较合适。如图11（b）所示，塔库和育空-塔纳纳地块岩石的U-Pb年龄与Bute-Knight吊坠的较老年龄组有一定程度的重叠。然而，如图11（a）所示，Lu-Hf数据却大不相同，> 360 Ma晶粒的少年值更大，而<360 Ma晶粒的负值更大。因此，我们得出的结论是，Bute-Knight悬垂物的岩石与Taku和Yukon-Tanana地层的岩石没有主要联系。上述的Lu-Hf同位素关系表明，鉴于U-Pb年龄和Lu-HF同位素特征非常不同，与育空-塔纳纳地层的主要联系不太可能（图11）。与Wrangellia地层的联系得到了类似的U的支持。 -Pb年龄和εHft值（图9），但由于垂悬物中富含石英的准沉积岩的存在和偏玄武岩的稀缺以及温哥华岛上缺乏富含石英的碎屑岩层和镁铁质火山岩的存在，这是一个问题。初级连接将需要在Karmutsen，Quatsino，Parsons湾和Harbledown地层（在研究区域的西南角）和现在距东北数十公里的沉积沉积物垂线之间发生明显的侧向相变化（图2）。与Stikine地层的主要联系也是合理的，但由于缺乏Stikine地层的Lu-Hf数据，因此很难完全评估。这两个组合中相似的U-Pb年龄的发生以及上古生界Stikine地层中存在富含石英的碎屑岩层，与Rusmore等人报道的年代学和古磁性联系一致。[9]。以前的工作人员没有考虑的另一种可能性是，Bute-Knight变沉积岩与Alexander地层具有主要联系。尽管亚历山大大地带的大多数地层缺乏富含石英的碎屑层，并且主要产出> 400 Ma碎屑锆石，但该地带南部的沉积沉积岩主要由夹层石英岩，大理石，以及变质岩，主要生成400-270 Ma碎屑锆石颗粒，其εHft值为青少年（图10（a））。亚历山大山地的岩石中也含有〜550 Ma和〜450 Ma碎屑锆石，尽管在Bute-Knight垂饰中，大多数这些晶粒的εHft值与这些年龄的晶粒的εHft值不重叠。这些相似之处增加了Bute-Knight悬垂物可能是Alexander地形的东南延续的可能性。鉴于上面提到的地质，U-Pb地质学和Lu-Hf同位素差异，Bute-Knight悬垂物也有可能是与附近任何这些地形中的岩石无关。也许，当可以获得更多的U-Pb年代学和Lu-Hf同位素数据时，与遥远的Cordilleran地层的联系就会出现，或者这些垂线可能被认为是一个独特的地层。另一种可能性是，准沉积岩属于具有不同构造亲和力的几种不同构造地层单元。分隔各个组件的结构边界可能已被分隔悬垂物的广泛的光子所掩盖。这种可能性与石英岩-大理石样品产生令人惊讶的年龄分布范围的观察结果一致（图4）。如上所述，可用的地质，U-Pb年代学和Lu-Hf同位素数据没有建立或确定排除了与Wrangellia地层的主要联系[Wheeler和McFeely提出[6]，Wheeler等。[7]，和Journeay等。[8]]或Stikine地形[如Rusmore等人所建议。[9]。现有的数据还增加了与亚历山大山脉的班克斯岛组合岩石之间可能存在联系的可能性。鉴于Wrangellia和Alexander山脉属于Insular上层地形而Stikine属于Intermontane上层地形，我们无法证明是否Intular-Intermontane边界线出现在Bute-Knight吊坠的内侧或外侧。在图1中用虚线显示了该边界的两个可能位置。考虑到该边界的构造意义，这是不幸的，如上所述，Pavlis等人最近对此进行了讨论。[51]。的解释是，约50％的< 从沉积沉积样品中进行的170 Ma分析记录了变质锆石的生长，这为利用年龄与U / Th和U浓度的关系图重建沿海岸山脉岩基岩的西侧变质的历史提供了机会。Rubatto [25]，Kirkland等人已经使用了这种方法。[26] Yakymchuk等。[27]以及其他许多人重建了其他造山带的变质历史。图8（a）和8（b）所示的模式表明，变质作用主要发生在〜170和〜130 Ma之间以及〜110和〜87 Ma之间，在〜153，〜136 Ma和〜101 Ma处有明显的峰值。较年轻的年龄范围与鲁珀特王子亲王附近的海岸山脉西侧（例如[52]）和北部（例如[53]）的变质主年龄是绝好匹配。相反，仅在研究区域西北部的外岛上才局部认识到变质的较早阶段的证据（图1），[3]报告说，班克斯岛组合的变质岩被年龄约156 Ma的未变形堤防侵入。研究区域中这种解释的变质记录与胶质化时间之间的相似性[图8；见图8。Cecil等。[11]表明，变质作用主要是由邻近小体的热量驱动的。165-128 Ma火成锆石的εHft值的明显下降表明，变质作用和岩浆作用可能与侏罗纪-早白垩世地壳增厚有关[例如，Girardi等。[54]，Tochilin等。[3]，Beranek等。[55]。对白细胞基岩和沉积沉淀样品的分析表明，约50％的< 从我们的沉积沉积样品中产生的170 Ma年龄（约占总年龄的28％）是火成岩。尽管在露头上仔细检查了样本材料并在加工过程中检查了样本材料，但在收集过程中，我们无意中将白细胞门槛或静脉中的物质掺入了我们的一些样本中。这表明在岩性岩性地层中沉积沉积样品时必须格外小心。我们的地质观察结果与U-Th-Pb年代学和Lu-Hf同位素结果相结合，得出了有关But中沉积沉积物垂向的构造亲和力的一阶结论。 -骑士区：（1）从Bute-Knight沉积沉积样品中的锆石生成的U-Th-Pb年龄的大约2/3小于170 Ma，主要分为两组：165-128 Ma（峰值年龄152 Ma）和114-88 Ma（峰值年龄102 Ma）。这些年龄与侵入变质垂体的岩体年龄和基岩[11]年龄相吻合，这表明<170 Ma年龄必须记录沉积后的火成和/或变质过程。相反，样品中> 170 Ma的年龄被解释为碎屑锆石的结晶年龄的可靠记录（2）我们的沉积沉积样品中大多数> 170 Ma的碎屑锆石都属于590-528 Ma（峰值）的四个主要组。年龄为560 Ma），485-432 Ma（峰值年龄452 Ma），356-286 Ma（峰值年龄307 Ma）和228-185 Ma（峰值年龄216和198 Ma）（图4）。从云母片岩-石英岩垂饰中采集的三个样品均以365至285 Ma之间的年龄为主，分别在349、310和302 Ma处出现个别年龄峰值（被解释为最大沉积年龄）。这些最大的沉积年龄，加上228-185 Ma组年龄的稀缺性（图4），表明这些地层在古生代晚期积累。从石英岩-大理石垂饰上采集的样品具有一定的年龄范围，主要年龄峰值为560、452、411、345、331、322、319、216、209和198 Ma。这些样品的最大沉积年龄包括一个年龄较大的年龄组，分别为345、341、333、331、322和319 Ma，以及一个年龄较小的年龄为246、216、209和198 Ma。几乎所有样品中至少存在228-185 Ma年龄，表明这些地层在中生代早期积累。几个样本会产生大约1948、1845、1775、1701、1429、1119，和1109 Ma（3），许多<170 Ma的分析都产生了U浓度和U / Th值，并在CL图像中显示了与侵入白垩系基岩的白垩纪基岩中锆石的值和CL模式相似的分区模式。相反，许多年轻分析都产生较高的U浓度和U / Th值，并在CL图像中显示回旋区带，这表明晶粒（或在许多情况下仅是薄的缘）是起源变质的。比较来自Pluton，白细胞基岩和变质沉积样品中的锆石的U / Th值（图8（a））和U浓度（图8（b））提供了一种估算变质锆石与火成锆石比例的方法。如图8（a）所示，U / Th = 8的临界值表明60％的分析记录了火成锆石的生长，而40％的是变质的。代替，U浓度的临界值= 1,100 ppm意味着47％的分析是火成岩，而53％的是火成岩（4）鉴于锆石通常在中度到高级变质过程中生长[例如Rubatto [25]，Kirkland等。 。[26] Yakymchuk等。[27]，锆石晶粒（或轮辋）的年龄分布被认为是变质的，这为重建研究区域的变质历史提供了机会。如图8（a）和8（b）所示，似乎变质作用主要发生在〜170和〜130 Ma之间以及〜110和〜87 Ma之间，明显的峰出现在153、136 Ma和101 Ma。这表明我们在采集过程中检查火成岩露头并在加工过程中检查每个岩石碎片的程序不足以确保仅对次沉积物进行分析（6）ε来自次沉积物样品的锆石晶粒的Hft值记录了中间值的趋势（590至528 Ma谷物的（0至+5；平均+3），通过高度可变但通常较高的485-432 Ma谷物的少年值（+2至+13；平均+8），达到高青少年值（对于356-286 Ma和228-185 Ma晶粒，大多数为+4至+15;平均为+12）（图7）。来自沉积沉积样品的小于170 Ma晶粒的εHft值仍被认为是变质的（例如，U / Th> 8和U浓度> 1100ppm⁠）（图7），这表明锆石在周围（少年）变质沉积岩变质过程中生长。沉积沉积样品中的窗台和火成锆石中<170 Ma谷粒的εHft值在165-128 Ma年龄段较弱，而在114-88 Ma年龄段则返回较高的幼年值。165-128 MaεHft值的略微下降可能记录了侏罗纪-早白垩世时期在更深地壳水平上更多演化岩石的融化（7）我们的U-Th-Pb和Lu-Hf结果与现有数据的比较相邻的地球（图9-11）表明，Bute-Knight垂饰与Yukon-Tanana地球的岩石没有主要联系，但不足以证明或排除与Wrangellia，Stikine或Alexander地球的主要联系。鉴于Wrangellia和Alexander地属于Insular上地，而Stikine属于Intermontane上地，因此，我们无法为有关Insular-Intermontane地边界的位置，年龄和起源的长期争论提供新的见解。 （例如[51，56]）从Bute-Knight沉积沉积样品的锆石中生成的U-Th-Pb年龄的大约2/3 <170 Ma，两组主要年龄在165-128 Ma（峰值年龄为152 Ma）。 ）和114-88 Ma（峰值年龄102 Ma）。这些年龄与侵入变质垂体的岩体年龄和基岩[11]年龄相吻合，这表明<170 Ma年龄必须记录沉积后的火成和/或变质过程。相反，> 样品中的170 Ma年龄被解释为碎屑锆石的结晶年龄的可靠记录。我们沉积沉积样品中的> 170 Ma碎屑锆石中的大多数属于590-528 Ma（峰值年龄560 Ma）的四个主要组，485 -432 Ma（峰值年龄452 Ma），356-286 Ma（峰值年龄307 Ma）和228-185 Ma（峰值年龄216和198 Ma）（图4）。从云母片岩-石英岩悬垂物收集的三个样品均以365至285 Ma之间的年龄为主，个别年龄峰值（被解释为最大沉积年龄）分别为349、310和302 Ma。这些最大的沉积年龄，加上228-185 Ma组年龄的稀缺性（图4），表明这些地层在古生代晚期积累。从石英岩大理石垂饰上收集的样品具有一定的年龄范围，其主要年龄峰值为560、452、411、345、331、322、319、216、209和198 Ma。这些样品的最大沉积年龄包括一个年龄较大的年龄组，分别为345、341、333、331、322和319 Ma，以及一个年龄较小的年龄为246、216、209和198 Ma。几乎所有样品中至少存在228-185 Ma年龄，表明这些地层在中生代早期积累。几个样本产生的旧单粒年龄大约为1948、1845、1775、1701、1429、1119和1109 Ma。许多<170 Ma的分析产生了U浓度和U / Th值，并在CL图像中显示了与侵入准沉积岩的白垩纪基岩中的锆石的碳值和CL模式。相反，许多年轻分析都产生较高的U浓度和U / Th值，并在CL图像中显示回旋分区，这表明谷物（或在许多情况下只是薄的轮辋）在起源上是变质的。比较从Pluton，白土基岩和沉积沉积样品中的锆石的U / Th值（图8（a））和U浓度（图8（b））提供了一种估算变质锆石与火成锆石比例的方法。如图8（a）所示，U / Th = 8的临界值表明60％的分析记录了火成锆石的生长，而40％是变质的。取而代之的是，U浓度的临界值= 1,100 ppm，表明47％的分析是火成岩，而53％的是火成岩。鉴于锆石通常在中度到高级变质期生长[例如Rubatto [25]，Kirkland等。[26] Yakymchuk等。[27]，锆石（或轮辋）的年龄分布被认为是变质的，这为重建研究区域的变质历史提供了机会。如图8（a）和8（b）所示，似乎变质作用主要发生在〜170和〜130 Ma之间以及〜110和〜87 Ma之间，明显的峰出现在153、136 Ma和101 Ma。相似年龄的p和基岩的发生（图8）增加了以下可能性：变质可能主要是由与邻近的lut相关的热量引起的，和/或变质和岩浆都可能是由于地壳增厚而引起的。在我们的沉积沉积样品中被认为是火成岩的<170 Ma锆石中有70％的锆石表明，我们的大多数样品都包含火成岩物质（例如 样本收集过程中合并的“腓状静脉或窗台”。这表明，我们在收集过程中检查火成岩露头并在加工过程中检查每个岩石碎片的程序不足以确保仅对次沉积物进行分析。来自次沉积物样品的锆石晶粒的Hft值记录了中间值的趋势（0至+ 5； 590-528 Ma谷物的平均值为+3），这是通过高度可变但通常为485-432 Ma谷物的青少年值（+2至+13；平均值为+8）到高度青少年值（大部分为+4至3）得出。 +15; 356-286 Ma和228-185 Ma晶粒的平均值为+12）（图7）。来自沉积沉积样品的＜170 Ma晶粒的εHft值仍被认为是变质的（例如，U / Th> 8且U浓度> 1100ppm⁠），仍处于幼年状态（图7），这表明锆石在周围（少年）变质沉积岩变质过程中生长。沉积沉积样品中的窗台和火成锆石中<170 Ma谷粒的εHft值在165-128 Ma年龄段较弱，而在114-88 Ma年龄段则返回较高的幼年值。165-128 MaεHft值的略微下降可能记录了侏罗纪-早白垩世时期更深地壳水平上更多演化岩石的融化我们的U-Th-Pb和Lu-Hf结果与来自邻近地层的可用数据的比较（图9-11）表明，Bute-Knight垂饰与育空塔纳纳地貌的岩石没有主要联系，但不足以证明或排除与Wrangellia，Stikine或Alexander地貌的主要联系。鉴于Wrangellia和Alexander地属于Insular上地，而Stikine属于Intermontane上地，因此，我们无法为有关Insular-Intermontane地边界的位置，年龄和起源的长期争论提供新的见解。 （例如[51，56]）作者声明与本文的发表没有利益冲突。本文报道的分析主要由M. Dafov，A。Carrera和M. Pereira作为亚利桑那大学的本科研究项目。NSF EAR奖1347375支持了现场工作和实验室分析。ArizonaLaserChron中心还获得了NSF EAR奖1338583和1649254支持了实验室分析。