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The complex response of continental silicate rock weathering to the colonization of the continents by vascular plants in the Devonian Am. J. Sci. (IF 2.9) Pub Date : 2022-03-01 Pierre Maffre,Yves Godderis,Alexandre Pohl,Yannick Donnadieu,Sebastien Carretier,Guillaume Le Hir
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On carbon burial and net primary production through Earth's history Am. J. Sci. (IF 2.9) Pub Date : 2022-03-01 Noah J. Planavsky,Mojtaba Fakhraee,Edward W. Bolton,Christopher T. Reinhard,Terry T. Isson,Shuang Zhang,Benjamin J. W. Mills
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The petrogenesis and tectonic setting of the New Hampshire Plutonic Suite: Towards a more comprehensive model for the magmatism of the Acadian Orogeny Am. J. Sci. (IF 2.9) Pub Date : 2022-03-01 Michael J. Dorais
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Temperatures of canonical condensation: Constraints from CAIs Am. J. Sci. (IF 2.9) Pub Date : 2022-01-01 Richard O. Sack
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Understanding the isotopic composition of sedimentary sulfide: A multiple sulfur isotope diagenetic model for Aarhus Bay Am. J. Sci. (IF 2.9) Pub Date : 2022-01-01 Andrew L. Masterson,Marc J. Alperin,Gail L. Arnold,William M. Berelson,Bo B. Jørgensen,Hans Røy,David T. Johnston
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Clumped isotope constraints on warming and precipitation seasonality in Mongolia following Altai uplift Am. J. Sci. (IF 2.9) Pub Date : 2022-01-01 Jeremy K. Caves Rugenstein,Katharina Methner,Tyler Kukla,Andreas Mulch,Tina Lüdecke,Jens Fiebig,Anne Meltzer,Karl W. Wegmann,Peter Zeitler,C. Page Chamberlain
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The kabr El-Bonaya peridotites, Southeastern Sinai, Egypt: petrology, geochemistry, and metamorphism of Neoproterozoic arc ultramafic cumulates Am. J. Sci. (IF 2.9) Pub Date : 2021-12-01 Ayman E. Maurice,Mokhles K. Azer,Paul D. Asimow,Fawzy F. Basta,Hassan M. Helmy,Tomoyuki Shibata
Two small, isolated ultramafic masses in the northeastern part of the Wadi Kid area, southeast Sinai, are composed of variably serpentinized harzburgite and lherzolite with minor talc-anthophyllite rock. The primary phases are dominantly olivine, orthopyroxene and Cr-spinel; clinopyroxene, amphibole, and phlogopite are also found in lherzolite samples. The whole-rock Mg# of harzburgite samples (89–91)
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The role of the solid earth in regulating atmospheric O2 levels Am. J. Sci. (IF 2.9) Pub Date : 2021-12-01 Daniel A. Stolper,John A. Higgins,Louis A. Derry
Solid-earth processes act as both sources and sinks for atmospheric O2. They act as sinks by introducing reduced minerals and gases to the earth's surface that can remove O2 from the atmosphere and ocean. They act as sources by exporting organic carbon and sedimentary pyrite to the mantle via subduction. Here we examine the relative sizes of igneous source and sinks of O2 for the modern earth to determine
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Coexisting arc and MORB signatures in the Sonakhan greenstone belt, India: late Neoarchean – early Proterozoic subduction rollback and back-arc formation Am. J. Sci. (IF 2.9) Pub Date : 2021-11-01 Gautam Kumar Deb,Dilip Saha,Sarbani Patranabis-Deb,Amlan Banerjee
Differentiation of rock suites related to mid-ocean ridge and subduction zone in Archean greenstone belts is important in tracing back tectonic processes related to evolution of these belts. The late Neoarchean – early Paleoproterozoic Sonakhan greenstone belt (SGB) lying between Mesoarchean gneisses of the Bastar craton and the Mesoproterozoic Chattisgarh Supergroup in central India was earlier interpreted
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Neoarchean basement, mantle enrichment and crustal extraction in central Asia: petrogenesis of 2.5 Ga amphibolite and metadiorite in NE China Am. J. Sci. (IF 2.9) Pub Date : 2021-11-01 Huichuan Liu,Jun Shao,Guangyou Zhu,Yinglei Li
Archean basement in the Central Asian Orogenic Belt (CAOB) is relatively rare, but it has the potential to provide additional information on the processes of lithospheric mantle enrichment and crust extraction processes during the early history of the Earth. We identified Neoarchean amphibolite (2537−2565 Ma) and metadiorite (2481−2539 Ma) in the Biliya area of the Erguna Terrane in the southeast CAOB
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Early Cretaceous solar cycles recorded in lacustrine laminations in North China Am. J. Sci. (IF 2.9) Pub Date : 2021-11-01 Xing Tian,Yuan Gao,Tyler Kukla,Olaf Lenz,He Huang,Daniel E. Ibarra,Shouliang Sun,Chengshan Wang
Solar cycles are important moderators of the Earth’s global climate system. Although modern-day solar cycles are well known, they have been less studied over geological time. High-resolution records such as varves have been previously used for reconstructing solar cycles from the Paleoproterozoic through Quaternary. In this paper, very fine (<1 mm) sedimentary laminations of the Early Cretaceous Yixian
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Rock weathering and nutrient cycling along an erodosequence Am. J. Sci. (IF 2.9) Pub Date : 2021-10-01 Friedhelm von Blanckenburg,Jan A. Schuessler,Julien Bouchez,Patrick J. Frings,David Uhlig,Marcus Oelze,Daniel A. Frick,Tilak Hewawasam,Jeannie Dixon,Kevin Norton
How flowing water and organisms can shape Earth's surface, the Critical Zone, depends on how fast this layer is turned over by erosion. To quantify the dependence of rock weathering and the cycling of elements through ecosystems on erosion we have used existing and new metrics that quantify the partitioning and cycling of elements between rock, saprolite, soil, plants, and river dissolved and solid
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The role of vegetation in setting strontium stable isotope ratios in the Critical Zone Am. J. Sci. (IF 2.9) Pub Date : 2021-10-01 Julien Bouchez,Friedhelm von Blanckenburg
At Earth's surface the stable isotope ratio of strontium (88Sr/86Sr) is predominantly set by biological uptake of Sr and its storage in plant litter. This conclusion was reached from a stable isotope mass balance that was independently validated by direct determination of elemental fluxes between the Critical Zone compartments (rock, soil, vegetation, and stream water) of three field sites located
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Metal isotopes as markers of biogeochemical processes and fluxes in the eroding Critical Zone Am. J. Sci. (IF 2.9) Pub Date : 2021-10-01 C. Page Chamberlain
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Interpreting silicon isotopes in the Critical Zone Am. J. Sci. (IF 2.9) Pub Date : 2021-10-01 Patrick J. Frings,Marcus Oelze,Franziska Schubring,Daniel A. Frick,Friedhelm von Blanckenburg
Metal and metalloid stable isotope ratios have emerged as potentially powerful proxies for weathering, element cycling and export in the Critical Zone. The simplest possible interpretative framework for these isotope ratios has three parameters: (i) the isotope ratio of the parent minerals undergoing weathering, (ii) the partitioning of the element between solute and the new secondary phases, and (iii)
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Quantifying biotic and abiotic Si fluxes in the Critical Zone with Ge/Si ratios along a gradient of erosion rates Am. J. Sci. (IF 2.9) Pub Date : 2021-10-01 Patrick J. Frings,Franziska Schubring,Marcus Oelze,Friedhelm von Blanckenburg
Silicon (Si) is an important nutrient for many plant and algae species, and the ultimate source of Si is silicate mineral weathering reactions. These topics have inspired the application of Si isotope geochemistry to quantifying Si cycling in the Critical Zone, though the interpretations are often equivocal. Because germanium (Ge) geochemistry is similar to that of Si, the Ge/Si ratio is considered
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A Laurentian cratonic reference from the distal Proterozoic basement of Western Newfoundland using tandem in situ and isotope dilution U-pb zircon and titanite geochronology Am. J. Sci. (IF 2.9) Pub Date : 2021-09-01 Eben B. Hodgin,Francis A. Macdonald,James L. Crowley,Mark D. Schmitz
The Humber Margin of Newfoundland preserves the most distal exposures of Proterozoic basement in northeastern Laurentia. Age uncertainty has permitted a range of hypotheses for its origin and links to subsequent tectonic events. One hypothesis has proposed large-scale orogen-parallel displacement between basement blocks in western Newfoundland. The apparent absence of Grenville- (∼1250–950 Ma sensu
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A comparative study of clay mineral authigenesis in terrestrial and martian lakes; an Australian example Am. J. Sci. (IF 2.9) Pub Date : 2021-09-01 Thomas F. Bristow,Arkadiusz Derkowski,David F. Blake,Genesis Berlanga,Patrick De Deckker
Clay mineral-bearing mudstones are a prominent component of ancient fluvial-lacustrine deposits, 100s of meters thick, documented by the Mars Science Laboratory (MSL) rover, in Gale crater, Mars. Most of the clay minerals documented by MSL are hypothesized to have formed in situ, at or close to the time of deposition ∼3.5 Ga ago, by aqueous alteration of basaltic detritus. Here we study the mechanisms
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Exploring multiple steady states in Earth's long-term carbon cycle Am. J. Sci. (IF 2.9) Pub Date : 2021-09-01 Benjamin J. W. Mills,Stephen Tennenbaum,David Schwartzman
The long-term carbon cycle regulates Earth's climate and atmospheric CO2 levels over multimillion-year timescales, but it is not clear that this system has a single steady state for a given input rate of CO2. In this paper we explore the possibility for multiple steady states in the long-term climate system. Using a simple carbon cycle box model, we show that the location of precipitation bands around
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Reconstructing lost plates of the Panthalassa Ocean through paleomagnetic data from circum-Pacific accretionary orogens Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Lydian M. Boschman,Douwe J.J. van Hinsbergen,Cor G. Langereis,Kennet E. Flores,Peter J.J. Kamp,David L. Kimbrough,Hayato Ueda,Suzanna H.A. van de Lagemaat,Erik van der Wiel,Wim Spakman
The Panthalassa Ocean, which surrounded the late Paleozoic-early Mesozoic Pangea supercontinent, was underlain by multiple tectonic plates that have since been lost to subduction. In this study, we develop an approach to reconstruct plate motions of this subducted lithosphere utilizing paleomagnetic data from accreted Ocean Plate Stratigraphy (OPS). We first establish the boundaries of the Panthalassa
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Petrogenesis and tectonic implications of TTG granitoids from the Daqingshan Complex of the Khondalite Belt, North China Craton Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Xiao Wang,Jian Zhang,Changqing Yin,Hai Zhou,Jin Liu,Xiaoguang Liu,Chen Zhao
Located in the Western Block of the North China Craton, the Khondalite Belt is one of the three Paleoproterozoic tectonic belts that were linked to the final assembly of the craton. At present, a popular model is that the Khondalite Belt was formed by the collision between the Yinshan and Ordos blocks at ∼1.95 Ga. However, the initiation of oceanic subduction and its related arc magmatism and accretionary
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Composition and provenance analysis of beach sands in an almost isolated sedimentary system – A field study of the Galápagos Archipelago Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Klemens Seelos,Yamirka Rojas-Agramonte,Alfred Kröner,Theofilos Toulkeridis,Gillian Inderwies,Yvonne Buelow
The Galápagos Archipelago is the surface expression of an active hotspot or long-lived mantle plume. The Archipelago consists of a group of 13 main islands which are located in the eastern central Pacific Ocean about 1,000 km west of the northern edge of the South American continent, east of the East Pacific Rise and south of the Galápagos spreading center. Because of the large distance to the nearest
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Deciphering paleogeography from orogenic architecture: Constructing orogens in a future supercontinent as thought experiment Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Douwe J. J. van Hinsbergen,Thomas L. A. Schouten
Orogens that form at convergent plate boundaries typically consist of accreted rock units that form an incomplete archive of subducted oceanic and continental lithosphere, as well as of deformed lithosphere of the former upper plate. Reading the construction of orogenic architecture forms the key to decipher the pre-orogenic paleogeographic distribution of oceans and continents, as well as bathymetric
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Chronological and geochemical variations of the late Mesozoic granitoids in the Taihang Mountains and middle-southern Tan-Lu Fault: Implications for lithosphere destruction of the North China Craton Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Yue-Lan Kang,Yu-Ruo Shi,J. Lawford Anderson
In the Late Mesozoic, the North China Craton (NCC) underwent significant lithospheric thinning and destruction, especially in the eastern part, but the mechanism and timing related to this process are still contentious. The Taihang Mountains (TH) are located in the western part of the eastern NCC and the Tan-Lu Fault (TLF) is in the eastern part, which are two essential magmatic areas that reveal deep
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A highly dynamic hot hydrothermal system in the subduction environment: Geochemistry and geochronology of jadeitite and associated rocks of the Sierra del Convento mélange (eastern Cuba) Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Juan Cárdenas-Párraga,Antonio Garcia-Casco,Idael F. Blanco-Quintero,Yamirka Rojas-Agramonte,Kenya Nuñez Cambra,George E. Harlow
A U-Pb zircon date of ∼113 Ma revealed that a variety of jadeitites and related omphacitite, chloritite and albite-rich rocks from the subduction-related Sierra del Convento block-in-serpentinite-matrix mélange (eastern Cuba) formed nearly synchronously with MORB metabasite-derived anatectic trondhjemitic liquids at high-temperature and pressure in a hot subduction environment. Field, petrologic and
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Multiphase ophiolite formation in the Northern Altyn Tagh Orogen, southeastern Tarim Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Qian Liu,Toshiaki Tsunogae,Guochun Zhao,Jianhua Li,Jinlong Yao,Yigui Han,Peng Wang
Early Paleozoic ophiolitic mélanges in the Altyn Tagh Orogen, southeastern Tarim, yield a large range of formation ages and geochemical affinities. This study focused on the Hongliugou ophiolitic mélange in the North Altyn Tagh subduction-accretion belt and involved mineral chemical, zircon geochronological, and whole-rock elemental and isotopic investigations of the ultramafic and mafic rocks. In
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Geodynamic environment of the ca. 3800 Ma Outer Arc Group, Isua (Greenland) Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Allen P. Nutman,Clark R.L. Friend,Vickie C. Bennett,Martin van Kranendonk,Allan R. Chivas
The arcuate, 35 km long Isua supracrustal belt (ISB, southern West Greenland) contains the world's largest remnants of Eoarchean volcanic and sedimentary sequences. The ISB is broadly divided into: (i) the northern Inner Arc Group of 3720 to 3690 Ma rocks, and (ii) the southern Outer Arc Group of ca. 3800 Ma rocks which is bounded on its northern side by the highly tectonized ca. 3750 Ma Dividing Sedimentary
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An Early Paleoproterozoic back-arc system along the southern margin of the Yinshan Block: Evidence from a newly-defined bimodal volcanic sequence in the Daqingshan Complex, Khondalite Belt Am. J. Sci. (IF 2.9) Pub Date : 2021-06-01 Xiao Wang,Jian Zhang,Changqing Yin,Hai Zhou,Jin Liu,Wenxia Zhang,Shuhui Zhang,Chen Zhao,Changquan Cheng
As one of the 2.1 to 1.9 Ga orogenic belts that welded the Columbia supercontinent, the Khondalite Belt in the North China Craton is a typical continent-continent collisional orogen that formed through the collision between the Yinshan and Ordos Blocks. Previous studies mostly focused on the collisional event in the Khondalite Belt but paid little attention to how the subduction system operated before
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Presentation and applications of mixing elements and dissolved isotopes in rivers (MEANDIR), a customizable MATLAB model for Monte Carlo inversion of dissolved river chemistry Am. J. Sci. (IF 2.9) Pub Date : 2021-05-01 Preston Cosslett Kemeny,Mark Albert Torres
The dissolved chemistry of rivers has been extensively studied to elucidate physical and climatic controls of chemical weathering at local to global spatial scales, as well as the impacts of chemical weathering on climate over short to geologic temporal scales. Within this effort, mixing models with Monte Carlo uncertainty propagation are a common tool for inverting measurements of dissolved river
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Paleoaltimetry of the Western Andes in Northern Chile (∼18.5–19.5°S) Am. J. Sci. (IF 2.9) Pub Date : 2021-05-01 Sebastian Jimenez-Rodriguez,Matthew Dettinger,Jay Quade,Kendra E. Murray
Establishing the timing of surface uplift in the Central Andes is essential for evaluating the geodynamic mechanisms responsible for mountain building and their role in the development of dry conditions along the western coasts of Peru and Chile. Here, we present new stable hydrogen isotopic values from stream waters and hydration water in volcanic glass from northern Chile (18.5–19.5°S) that show
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Origin and magmatic evolution of late Neoproterozoic post-accretion high-K calc-alkaline adakitic volcanics in the northern Arabian–Nubian Shield Am. J. Sci. (IF 2.9) Pub Date : 2021-05-01 Bassam A. Abuamarah,Mokhles K. Azer,Heba S. Mubarak
In the northernmost segment of the Arabian–Nubian Shield, a post-collisional high-K calc-alkaline volcanic sequence is exposed along Wadi Abu Ma’amel, Eastern Desert of the Nubian Shield. It comprises a series of intermediate to silicic volcanics and associated pyroclastics that include the Imperial Porphyry and calc-alkaline volcanics typical of the Dokhan Volcanics. The Imperial Porphyry occurs as
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Terrestrial biomarker isotope records of late Quaternary climate and source-to-sink sediment transport processes in southwestern Taiwan Am. J. Sci. (IF 2.9) Pub Date : 2021-04-01 Queenie Chang,Michael Hren,Andrew T. Lin,Clay Tabor,Shun-Wen Yu,Yvette Eley,Gregory Harris
Fluvial sediments are important archives of paleoenvironments. However, variations in sediment production and transport processes greatly influence sediment geochemistry and resultant interpretations of ancient conditions. Tectonically-active tropical regions are particularly sensitive to climate feedbacks because these areas are often characterized by high precipitation rates, rapid erosion and short
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Silurian-Devonian tectonic evolution of mid-coastal Maine, U.S.A.: Details of polyphase orogenic processes Am. J. Sci. (IF 2.9) Pub Date : 2021-04-01 David P. West,Emily M. Peterman,Jessica Chen
Detailed bedrock mapping, structural geology, meta-igneous whole rock geochemistry, and U-Pb geochronology from rocks sampled along a portion of a complexly deformed tectonic boundary between the Ordovician peri-Gondwanan Liberty-Orrington belt and Silurian syn-orogenic strata of the Fredericton trough (a.k.a. the Dog Bay Line) in mid-coastal Maine aid in deciphering the Silurian-Devonian tectonic
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Thermochemistry of melilites I. Towards resolving an inconsistency in nebular condensation calculations Am. J. Sci. (IF 2.9) Pub Date : 2021-04-01 Richard O. Sack
A thermodynamic model is formulated for (Ca,Na)2(Mg,Fe2+,Al,Fe3+)T1 (Al,Fe3+,Si)2T2O7 melilites. It employs the compositional vertices: åkermanite (Ca2MgSi2O7, 1), gehlenite (Ca2Al2SiO7, 2), iron åkermanite (Ca2Fe2+Si2O7, 3), ferrigehlenite (Ca2Fe23 + SiO7, 4), sodium melilite (NaCaAlSi2O7, 5), and the convergent ordering variables: s = XAl3 + T2a – XAl3+T2b and t = XFe3 + T2a – XFe3 + T2b to describe
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Unmixing multiple metamorphic muscovite age populations with powder X-ray diffraction and 40Ar/39Ar analysis Am. J. Sci. (IF 2.9) Pub Date : 2021-03-01 Ryan J. Mcaleer,David L. Bish,Michael J. Kunk,Peter M. Valley,Gregory J. Walsh,Robert P. Wintsch
A combination of modal estimates from powder X-ray diffraction (XRD) experiments and argon isotopic data shows that muscovite 40Ar/39Ar total gas age correlates with muscovite composition near the retrograde Bald Mountain shear zone (BMSZ) in Claremont, New Hampshire, and that the shear zone was active at ∼245 Ma. Petrologic study demonstrates that chemical disequilibrium is preserved in muscovite
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40Ar/39Ar and LA-ICP-MS U–Pb geochronology for the New England portion of the Early Cretaceous New England-Quebec igneous province: Implications for the postrift evolution of the eastern North American Margin Am. J. Sci. (IF 2.9) Pub Date : 2021-03-01 Jennifer R. Cooper Boemmels,Jean M. Crespi,Laura E. Webb,Julie C. Fosdick
The Early Cretaceous New England-Quebec igneous province is a classic example of postrift magmatism along the eastern North American passive margin. Although a suite of 40Ar/39Ar ages has been available for the Monteregian Hills lobe in the Quebec portion of the New England-Quebec igneous province for many years, only a single high accuracy radiometric age has been published for the Burlington lobe
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Carbon cycle evolution before and after the Great Oxidation of the atmosphere Am. J. Sci. (IF 2.9) Pub Date : 2021-03-01 Don E. Canfield
The rock record of organic carbon abundance and its isotopic composition is consistent with the evolution of life more than 3800 million years ago (Ma). Despite this, there are very few insights as to the ecology of this ancient biosphere or to its level of activity. One possible insight, however, comes from the isotopic composition of inorganic and organic carbon in ancient rocks. This isotope record
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The complexities of Mesoarchean to late Paleoproterozoic magmatism and metamorphism in the Qixia area, eastern North China Craton: Geology, geochemistry and SHRIMP U-Pb zircon dating Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Yusheng Wan,Shoujie Liu,Zhiyong Song,Simon A. Wilde,Laiming Wang,Chunyan Dong,Hangqiang Xie,Shiwen Xie,Jianhua Hou,Wenqian Bai,Dunyi Liu
Qixia is a typical area of early Precambrian basement in eastern Shandong Province, eastern North China Craton. Many TTG (tonalite-trondhjemite-granodiorite) assemblages were once considered to be supracrustal rocks (the Jiaodong Group), and the formation ages of the rocks have only been determined in a few outcrops as shown on the early geological map of the area. We carried out geological mapping
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Unravelling the P-T-t history of three high-grade metamorphic events in the Epupa Complex, NW Namibia: Implications for the Paleoproterozoic to Mesoproterozoic evolution of the Congo Craton Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Sönke Brandt,Reiner Klemd,Hanqiang Xie,Patrick Bobek
The Epupa Complex of northern Namibia constitutes the south-western margin of the Archean Congo Craton of central Africa. We present new petrological and geochronological data for metasedimentary migmatites that decode the poorly-known Paleoproterozoic to Mesoproterozoic evolution of this remote part of the craton. Detrital magmatic zircons with concordant 207Pb/206Pb ages between 1898 and 1774 Ma
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Late Neoarchean magmatic – metamorphic event and crustal stabilization in the North China Craton Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Mingguo Zhai,Lei Zhao,Xiyan Zhu,Yanyan Zhou,Peng Peng,Jinghui Guo,Qiuli Li,Taiping Zhao,Junsheng Lu,Xianhua Li
The ca. 2.5 Ga as the time boundary between the Archean and the Proterozoic eons is a landmark, indicating the most important continental crust evolving stage of the Earth, that is, the global cratonization or the formation of supercraton(s) that was unseen before and is unrepeated in the following history of the Earth's formation and evolution. The North China Craton (NCC) is one of the best recorders
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Timing and Nd-Hf isotopic mapping of early Mesozoic granitoids in the Qinling Orogen, central China: Implication for architecture, nature and processes of the orogen Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Xiaoxia Wang,Tao Wang,Changhui Ke,Yang Yang,Yongfei Tian
The Qinling orogen, one of the most important orogens in Asia, belongs to the northeastern part of the Tethyan orogen. The architecture and processes of the Qinling orogen remain controversial. In this study, we present 15 new zircon U–Pb ages, 20 whole-rock geochemical and 46 Sm-Nd isotopic analyses, and 30 zircon Lu–Hf isotopic data for early Mesozoic granitoids in this orogen, combining with data
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Late Paleozoic tectonic transition from subduction to collision in the Chinese Altai and Tianshan (Central Asia): New geochronological constraints Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Pengfei Li,Min Sun,Chao Yuan,Fred Jourdan,Wanwan Hu,Yingde Jiang
The evolution of the largest accretionary orogen in the world, the Central Asian Orogenic Belt (CAOB), involved a prolonged accretion history since the Neoproterozoic, followed by a collisional phase in response to the closure of the Paleo-Asian Ocean in the latest Paleozoic. The exact process for the tectonic transition from subduction to collision is still poorly constrained. Here we address this
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SHRIMP U-Pb dating of detrital zircons from the Permian sandstones along the southern and northern margins of Xar Moron River, central inner Mogolia: Implications for provenance and the tectonic evolution of the eastern segment of the Central Asian Orogenic Belt Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Xiancan Wu,Yuruo Shi,J. Lawford Anderson
The Xar Moron River fault zone, located in the eastern segment of the Central Asian Orogenic Belt (CAOB), represents the intensely debated final collision zone of the Siberian Craton (SC) and North China Craton (NCC). To determine the tectonic evolution of the eastern segment of the CAOB, we undertook petrography and zircon U-Pb dating of the Huanggangliang and Linxi formations in the Wufendi and Xingfuzhilu
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This Issue Is Dedicated To The Memory Of Distinguished Scientist Alfred Kroner Who Sadly Passed Away On 22 May 2019 Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Simon A. Wilde,Shoujie Liu,Yamirka Rojas-Agramonte,Guochun Zhao
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India in the Nuna to Gondwana supercontinent cycles: Clues from the north Indian and Marwar Blocks Am. J. Sci. (IF 2.9) Pub Date : 2021-01-01 Wei Wang,Peter A. Cawood,Manoj K. Pandit
Evolution of the Indian Block can be traced through Earth's Phanerozoic and Precambrian supercontinent cycles. The Paleoproterozoic tectonostratigraphic record of the North Indian Block and the Aravalli Delhi Fold Belt in the Nuna supercontinent assembly shows a close link with the events in the Cathaysia Block of South China. Accretion of the two terranes is documented by 1.97 to 1.92 Ga continental
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Reconstruction of the original extent of the Tertiary pre-volcanic gravels in the northern Sierra Nevada (CA): Implications for the range's Paleotopography Am. J. Sci. (IF 2.9) Pub Date : 2020-12-01 Christina M. Tipp,Emmanuel J. Gabet
The ancient auriferous gravels that helped spawn the California Gold Rush have figured prominently in investigations of the Cenozoic history of the Sierra Nevada. These fluvial sediments, scattered throughout the northern half of the range, are the remnants of much larger deposits that accumulated throughout the Eocene and Early Oligocene. In this study, we present a reconstruction of the original
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Zn2+-Pb2+-doped calcite shrub fabrics: Abiotic morphogenesis of travertine-like dripstone encrustation at the Jersey Zinc Mine, southeastern British Columbia Am. J. Sci. (IF 2.9) Pub Date : 2020-12-01 Paul L. Broughton
A cm-thick calcite dripstone on the floor of the abandoned Jersey Zinc Mine in southeastern British Columbia, western Canada, consists of a mixture of shrub and radial fibrous elongated columnar crystal fabrics that resulted from Zn2+ and Pb2+ doping of the calcite crystallographic lattice structure. These heavy metal elements were sourced from sulfide mineralized veins in the overlying limestone beds
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Constraints on surface temperature 3.4 billion years ago based on triple oxygen isotopes of cherts from the Barberton Greenstone Belt, South Africa, and the problem of sample selection Am. J. Sci. (IF 2.9) Pub Date : 2020-11-01 Donald R. Lowe, Daniel E. Ibarra, Nadja Drabon, C. Page Chamberlain
ABSTRACT Studies of Earth's surface temperature before 3.0 Ga have focused heavily on the oxygen isotopic composition of silica-rich sedimentary rocks called cherts. Interpretation of the results have suggested early surface temperatures ranging from as high as 70 ± 15 °C down to those that differ little from modern values. A major controversy centers on whether differences in the oxygen isotopic compositions
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Determining the origin of inclusions in garnet: Challenges and new diagnostic criteria Am. J. Sci. (IF 2.9) Pub Date : 2020-11-01 Thomas A. Griffiths, Gerlinde Habler, Rainer Abart
ABSTRACT Permian metapegmatite garnets from the Koralpe region (Eastern Alps, Austria) contain abundant submicrometer- to micrometer-sized inclusions of rutile, corundum, Fe-Mn phosphate, ilmenite, xenotime, zircon, and apatite. Variations in inclusion abundance, phase assemblage, habit, and size define sector and concentric zones in the garnets, tracing low-indexed garnet facets. Zoning resulted from
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Redox constraints on a Cenozoic imbalance in the organic carbon cycle Am. J. Sci. (IF 2.9) Pub Date : 2020-10-01 Matthieu E. Galvez
Over geological timescales, variations in atmospheric O2 are typically attributed to the imbalance between the weathering of organic carbon (OC) and reduced sulfur on land, the major sink terms for atmospheric O2, and the burial of OC and reduced sulfur in marine sediments, the major source terms of O2 to the atmosphere. But the Fe cycle matters too. Using a compilation of C, Fe, S and H fluxes between
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Zircon U-Pb geochronology and Nd-Pb isotope geochemistry of Blue Ridge basement in the eastern Great Smoky Mountains, U.S.A.: Implications for the Proterozoic tectonic evolution of the southeastern Laurentian margin Am. J. Sci. (IF 2.9) Pub Date : 2020-10-01 D.P. Moecher, F.C. Harris, E.A. Larkin, R.J. Quinn, K.B. Walsh, D.F. Loughry, E.D. Anderson, S.D. Samson, A.M. Satkoski, E. Tohver
The Mesoproterozoic to Paleozoic history of the southeastern Laurentian margin involved repeated collisional and accretionary tectonomagmatic events that reworked and recycled older continental crust of preceding events. The Great Smoky Mountains Basement Complex (GSMBC) within the southern Appalachian Blue Ridge exposes complexly deformed orthogneiss and paragneiss that preserve a record of Laurentian
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Miocene to Pleistocene glacial history of West Antarctica inferred from Nunatak geomorphology and cosmogenic-nuclide measurements on bedrock surfaces Am. J. Sci. (IF 2.9) Pub Date : 2020-10-01 Perry Spector, John Stone, Greg Balco, Trevor Hillebrand, Mika Thompson, Taryn Black
We report geomorphic observations and cosmogenic-nuclide measurements on bedrock surfaces from three isolated nunatak groups in West Antarctica: the Pirrit Hills and Nash Hills, located in the Weddell Sea sector, and the Whitmore Mountains, located on the Ross-Weddell divide. The objectives of this paper are to (i) establish a chronology for landscape development at these sites and (ii) quantify the
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A process-based ecosystem model (Paleo-BGC) to simulate the dynamic response of Late Carboniferous plants to elevated O2 and aridification Am. J. Sci. (IF 2.9) Pub Date : 2020-09-01 Joseph D. White, Isabel P. Montañez, Jonathan P. Wilson, Christopher J. Poulsen, Jennifer C. McElwain, William A. DiMichele, Michael T. Hren, Sophia Macarewich, Jon D. Richey, William J. Matthaeus
Ecosystem process models provide unique insight into terrestrial ecosystems by employing a modern understanding of ecophysiological processes within a dynamic environmental framework. We apply this framework to deep-time ecosystems made up of extinct plants by constructing plant functional types using fossil remains and simulating—as close as possible—the in vivo response of extinct taxa to their paleoclimatic
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Simulating meteoric and mixing zone carbonate diagenesis with a two-dimensional reactive transport model Am. J. Sci. (IF 2.9) Pub Date : 2020-09-01 Mingyu Zhao, Noah Planavsky, Amanda M. Oehlert, Guangyi Wei, Zheng Gong
Meteoric and mixing-zone diagenesis can dramatically alter the geochemical signatures of shallow marine carbonates. Most preserved pre-Cretaceous carbonates were deposited in shallow marine environments and thus may have been susceptible to meteoric and mixing-zone diagenesis. However, a quantitative understanding of how the geochemical composition of carbonates changes during diagenesis still requires
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Reconsidering the uplift history and peneplanation of the northern Lhasa terrane, Tibet Am. J. Sci. (IF 2.9) Pub Date : 2020-06-01 Miquela Ingalls, David B. Rowley, Brian S. Currie, Albert S. Colman
The elevation history of the Tibetan Plateau promises insight into the mechanisms and dynamics that develop and sustain high topography over tens of millions of years, as well as the contribution of uplift-related erosive flux to Cenozoic global cooling. The elevation history of the center and northern margin of the plateau have been historically less well-constrained than the southern margin. The
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The promise of optical NMR spectroscopy for experimental aqueous geochemistry Am. J. Sci. (IF 2.9) Pub Date : 2020-06-01 William H. Casey, Zhipan Wang, Nicholas Brandt, Nicholas Curro
New quantum technologies are being adapted to detect extraordinarily small magnetic fields. The signals are derived from the stimulated emission of light from single-atom defects in diamonds. The intensity of light reports the spin state of the electrons in the color center. The physics is relevant to geochemists because it points to a means of conducting NMR experiments on solutions in diamond-anvil
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Avalonian arc-to-platform transition in southeastern New England: U-Pb geochronology and stratigraphy of Ediacaran Cambridge “argillite,” Boston Basin, Massachusetts, USA Am. J. Sci. (IF 2.9) Pub Date : 2020-05-01 Margaret D. Thompson, James L. Crowley
High-precision CA-TIMS 206Pb/238U zircon dates clarify the age and tectonic significance of the Cambridge Formation which is poorly exposed in the Boston Basin, eastern Massachusetts, but transected by ∼50 km of tunnels beneath the mainland and Boston Harbor. The youngest detrital zircon in a sample from the northern Braintree Weymouth Tunnel establishes a maximum depositional age of 584.09 ± 1.98
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Tectonics and foreland basin development at the leading edge of the Humber Arm Allochthon, western Newfoundland, Canadian Appalachians Am. J. Sci. (IF 2.9) Pub Date : 2020-05-01 Ryan A. Lacombe, John W. F. Waldron, S. Henry Williams
The thrust front of the Northern Appalachians involves Ediacaran rift-related structures of the Laurentian margin that were re-worked in Taconic (Ordovician), Salinic (mainly Silurian) and Acadian (mainly Devonian) deformation events. Much of the thrust front is concealed under the Gulf of St. Lawrence, but Port au Port Peninsula, in western Newfoundland provides a cross-section through the Laurentian
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PALYNOLOGICAL DATING OF LOW-GRADE METAMORPHOSED ROCKS: APPLICATIONS TO EARLY PALEOZOIC ROCKS OF THE CENTRAL MAINE/AROOSTOOK-MATAPEDIA BASIN AND FREDERICTON TROUGH (NORTHERN APPALACHIANS) IN EASTERN AND EAST-CENTRAL MAINE, U.S.A. (AMERICAN JOURNAL OF SCIENCE, v. 320, n. 3, p. 280–312, https://doi.org/10.2475/03.2020.03) Am. J. Sci. (IF 2.9) Pub Date : 2020-04-01 Allan Ludman,Gil Machado,Paulo Fernandes
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Continuous continental growth as constrained by the sedimentary record Am. J. Sci. (IF 2.9) Pub Date : 2020-04-01 Christopher J. Spencer
Analysis of a database of ∼600,000 detrital zircon ages constrained by the depositional ages of the respective sedimentary units reveals a dynamic evolution of zircon age peaks through time. Analysis of a database of ∼600,000 detrital zircon ages constrained by the depositional ages of the respective sedimentary units reveals a dynamic evolution of zircon age peaks through time. This analysis demonstrates