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Ultra-Low Velocity Zone Beneath the Atlantic Near St. Helena 圣赫勒拿附近大西洋海底的超低流速区
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-07-06 DOI: 10.1029/2024GC011559
Felix Davison, Carl Martin, Rita Parai, Sanne Cottaar
{"title":"Ultra-Low Velocity Zone Beneath the Atlantic Near St. Helena","authors":"Felix Davison,&nbsp;Carl Martin,&nbsp;Rita Parai,&nbsp;Sanne Cottaar","doi":"10.1029/2024GC011559","DOIUrl":"https://doi.org/10.1029/2024GC011559","url":null,"abstract":"<p>There are various hotspots in the Atlantic Ocean, which are underlain by mantle plumes that likely cross the mantle and originate at the core-mantle boundary. We use teleseismic core-diffracted shear waves to look for an Ultra-Low Velocity Zone (ULVZ) at the potential base of central Atlantic mantle plumes. Our data set shows delayed postcursory phases after the core-diffracted shear waves. The observed patterns are consistent in frequency dependence, delay time, and scatter pattern with those caused by mega-ULVZs previously modeled elsewhere. Synthetic modeling of a cylindrical structure on the core-mantle boundary below St. Helena provides a good fit to the data. The preferred model is 600 km across and 20 km high, centered at approximately 15° South, 15° West, and with a 30% S-wave velocity reduction. Significant uncertainties and trade-offs do remain to these parameters, but a large ULVZ is needed to explain the data. The location is west of St. Helena and south of Ascension. Helium and neon isotopic systematics observed in samples from this region could point to a less-outgassed mantle component mixed in with the dominant signature of recycled material. These observations could be explained by a contribution from the Large Low Shear Velocity Province (LLSVP). Tungsten isotopic measurements would be needed to understand whether a contribution from the mega-ULVZ is also required at St. Helena or Ascension.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011559","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141556646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Quartz Dissolution Effects on Flow Channelization and Transport Behavior in Three-Dimensional Fracture Networks 石英溶解对三维断裂网络中的流道化和传输行为的影响
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-07-05 DOI: 10.1029/2024GC011550
Jeffrey D. Hyman, Alexis Navarre-Sitchler, Matthew R. Sweeney, Aleksandra Pachalieva, James W. Carey, Hari S. Viswanathan
{"title":"Quartz Dissolution Effects on Flow Channelization and Transport Behavior in Three-Dimensional Fracture Networks","authors":"Jeffrey D. Hyman,&nbsp;Alexis Navarre-Sitchler,&nbsp;Matthew R. Sweeney,&nbsp;Aleksandra Pachalieva,&nbsp;James W. Carey,&nbsp;Hari S. Viswanathan","doi":"10.1029/2024GC011550","DOIUrl":"https://doi.org/10.1029/2024GC011550","url":null,"abstract":"<p>We perform a set of reactive transport simulations in three-dimensional fracture networks to characterize the impact of geochemical reactions on flow channelization. Flow channelization, a frequently observed phenomenon in porous and fractured subsurface rock formations, results from the spatially variable hydraulic resistance offered by a geological structure. In addition to geo-structural features such as network connectivity, geometry, and hydraulic resistance, geochemical reactions, for example, dissolution and precipitation, can dynamically inhibit or enhance flow channelization. These geochemical processes can change the fracture permeability leading to increased flow channelization, which are localized connected regions of high volumetric flow rates that are seemingly ubiquitous in the subsurface. In our simulations, fractures partially filled with quartz are gradually dissolved until quasi-steady state conditions are obtained. We compare the flow field's initial unreacted and final dissolved states in terms of flow and transport observations. We observe that the dissolved fracture networks provide less resistance to flow and exhibit increased flow channelization when compared to their unreacted counterparts. However, there is substantial variability in the magnitude of these changes which implies that the channelization strongly depends on the network structure. In turn, we identify the interplay between the particular network structure and the impact of geochemical dissolution on flow channelization. The presented results indicate that geological systems that have been weathering or reactive for longer times in older landscapes are likely to have increased flow channelization compared to their equivalent but younger counterparts, which implies a time dependence on flow channelization in fractured media.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011550","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141556554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The Impact of Velocity Update Frequency on Time Accuracy for Mantle Convection Particle Methods 速度更新频率对地幔对流粒子法时间精度的影响
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-07-04 DOI: 10.1029/2023GC011192
S. J. Trim, S. L. Butler, R. J. Spiteri
{"title":"The Impact of Velocity Update Frequency on Time Accuracy for Mantle Convection Particle Methods","authors":"S. J. Trim,&nbsp;S. L. Butler,&nbsp;R. J. Spiteri","doi":"10.1029/2023GC011192","DOIUrl":"https://doi.org/10.1029/2023GC011192","url":null,"abstract":"<p>Computing the velocity field is an expensive process for mantle convection codes. This has implications for particle methods used to model the advection of quantities such as temperature or composition. A common choice for the numerical treatment of particle trajectories is classical fourth-order explicit Runge–Kutta (ERK4) integration, which involves a velocity computation at each of its four stages. To reduce the cost per time step, it is possible to evaluate the velocity for a subset of the four time integration stages. We explore two such alternative schemes, in which velocities are only computed for: (a) stage 1 on odd-numbered time steps and stages 2–4 for even-numbered time steps, and (b) stage 1 for all time steps. A theoretical analysis of stability and accuracy is presented for all schemes. It was found that the alternative schemes are first-order accurate with stability regions different from that of ERK4. The efficiency and accuracy of the alternate schemes were compared against ERK4 in four test problems covering isothermal, thermal, and thermochemical flows. Exact solutions were used as reference solutions when available. In agreement with theory, the alternate schemes were observed to be first-order accurate for all test problems. Accordingly, they may be used to efficiently compute solutions to within modest error tolerances. For small error tolerances, however, ERK4 was the most efficient.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011192","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141536732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Evidence for Low-Pressure Crustal Anatexis During the Northeast Atlantic Break-Up 东北大西洋断裂期间低压地壳钝化的证据
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-07-04 DOI: 10.1029/2023GC011413
A. M. Morris, S. Lambart, M. A. Stearns, J. R. Bowman, M. T. Jones, G. Mohn, G. Andrews, J. Millett, C. Tegner, S. Chatterjee, J. Frieling, P. Guo, D. W. Jolley, E. H. Cunningham, C. Berndt, S. Planke, C. A. Alvarez Zarikian, P. Betlem, H. Brinkhuis, M. Christopoulou, E. Ferré, I. Y. Filina, D. T. Harper, J. Longman, R. P. Scherer, N. Varela, W. Xu, S. L. Yager, A. Agarwal, V. J. Clementi
{"title":"Evidence for Low-Pressure Crustal Anatexis During the Northeast Atlantic Break-Up","authors":"A. M. Morris,&nbsp;S. Lambart,&nbsp;M. A. Stearns,&nbsp;J. R. Bowman,&nbsp;M. T. Jones,&nbsp;G. Mohn,&nbsp;G. Andrews,&nbsp;J. Millett,&nbsp;C. Tegner,&nbsp;S. Chatterjee,&nbsp;J. Frieling,&nbsp;P. Guo,&nbsp;D. W. Jolley,&nbsp;E. H. Cunningham,&nbsp;C. Berndt,&nbsp;S. Planke,&nbsp;C. A. Alvarez Zarikian,&nbsp;P. Betlem,&nbsp;H. Brinkhuis,&nbsp;M. Christopoulou,&nbsp;E. Ferré,&nbsp;I. Y. Filina,&nbsp;D. T. Harper,&nbsp;J. Longman,&nbsp;R. P. Scherer,&nbsp;N. Varela,&nbsp;W. Xu,&nbsp;S. L. Yager,&nbsp;A. Agarwal,&nbsp;V. J. Clementi","doi":"10.1029/2023GC011413","DOIUrl":"https://doi.org/10.1029/2023GC011413","url":null,"abstract":"<p>While basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite-garnet-cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma-rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper-crustal depths (&lt;5 kbar, 18 km depth) and high temperature (750–800°C) with up to 3 wt% water content. In situ U-Pb analyses on zircon inclusions give a magmatic crystallization age of 54.6 ± 1.1 Ma, consistent with emplacement that post-dates the Paleocene-Eocene Thermal Maximum. Our results suggest that the opening of the Northeast Atlantic was associated with a phase of low-pressure, high-temperature crustal anatexis preceding the main phase of magmatism.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011413","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141536900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Primary Controlling Factors of Apatite Trace Element Composition and Implications for Exploration in Orogenic Gold Deposits 磷灰石微量元素组成的主要控制因素及其对成岩金矿床勘探的影响
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-07-03 DOI: 10.1029/2024GC011574
Genshen Cao, Huayong Chen, Yu Zhang, Weipin Sun, Junfeng Zhao, Hongtao Zhao, Hao Wang
{"title":"Primary Controlling Factors of Apatite Trace Element Composition and Implications for Exploration in Orogenic Gold Deposits","authors":"Genshen Cao,&nbsp;Huayong Chen,&nbsp;Yu Zhang,&nbsp;Weipin Sun,&nbsp;Junfeng Zhao,&nbsp;Hongtao Zhao,&nbsp;Hao Wang","doi":"10.1029/2024GC011574","DOIUrl":"https://doi.org/10.1029/2024GC011574","url":null,"abstract":"<p>Significant and readily accessible orogenic gold deposits have been previously recognized, exploited, and progressively depleted. Innovative approaches are required to discover new and deeply buried deposits. Recently, trace element variations in apatite have been used to distinguish fertile and barren environments as reliable mineral exploration tools. In this study, machine learning models using Random Forest and Deep Neutral Network are utilized to assess the fertility of quartz veins and altered zones in the orogenic gold systems. The two models have been trained using trace element data of apatite, and the performance of both models yield good classification accuracy (∼90% on average) with low false positive rates. Feature importance analysis (Gini decrease and hidden layer weights) suggest that Pb, As, U, Sr, Eu, Mn, and Fe are the important parameters. Arsenic, U, Eu, Mn, and Fe are redox-sensitive elements, with their concentrations responding to changes in fluid redox conditions. Strontium primarily originates from the breakdown of plagioclase, which is more likely to occur under oxidizing fluid conditions. Therefore, we infer that the main controlling factor of the models is the redox conditions. The two distinct models consistently highlight the most significant contribution of Pb to this differentiation, even though Pb is not a redox-sensitive element and can only substitute for Ca<sup>2+</sup> in apatite as Pb<sup>2+</sup>. We infer that the high contribution of Pb may be attributed to the potential transportation of Au in the form of a Pb-(Bi)-Au melt, and the Pb content in apatite is influenced by the Pb content in the melt, fluid oxygen, and sulfur fugacity. We also propose a novel discriminant plot using Linear Discriminant Analysis (LDA) to assess the mineralization potential in quartz veins and alteration zones based on apatite trace element data. The machine learning and LDA results suggest that apatite trace elements could be used effectively in the future orogenic gold deposit exploration.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011574","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141536864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Snapshots of Coastal Ecology Using Multiproxy Analysis Reveals Insights Into the Preservation of Swamp and Marsh Environments Since the Late Pleistocene 利用多代理分析的沿海生态快照揭示了晚更新世以来沼泽和沼泽环境的保存情况
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-07-01 DOI: 10.1029/2024GC011489
Kendall Fontenot, Kristine L. DeLong, Brian A. Schubert, Sophie Warny, Davin J. Wallace, Carrie M. Miller, Erin Culver-Miller, Michael J. Polito, Carl A. Reese, Kathryn Garretson, Kehui Xu, Grant L. Harley, Jeffrey Obelcz, Kelli L. Moran, Julian Traphagan, Douglas Jones, Alicia Caporaso
{"title":"Snapshots of Coastal Ecology Using Multiproxy Analysis Reveals Insights Into the Preservation of Swamp and Marsh Environments Since the Late Pleistocene","authors":"Kendall Fontenot,&nbsp;Kristine L. DeLong,&nbsp;Brian A. Schubert,&nbsp;Sophie Warny,&nbsp;Davin J. Wallace,&nbsp;Carrie M. Miller,&nbsp;Erin Culver-Miller,&nbsp;Michael J. Polito,&nbsp;Carl A. Reese,&nbsp;Kathryn Garretson,&nbsp;Kehui Xu,&nbsp;Grant L. Harley,&nbsp;Jeffrey Obelcz,&nbsp;Kelli L. Moran,&nbsp;Julian Traphagan,&nbsp;Douglas Jones,&nbsp;Alicia Caporaso","doi":"10.1029/2024GC011489","DOIUrl":"https://doi.org/10.1029/2024GC011489","url":null,"abstract":"<p>The southeastern United States Coastal Plain ecosystem contains baldcypress (<i>Taxodium distichum</i>) swamps and grass-dominated marshes. These ecosystems also occurred on the exposed continental shelf during lower sea levels but are rarely preserved due to the mechanically erosive nature of transgression and regression. Two presently marine sites on the northeastern Gulf of Mexico's continental shelf contain well-preserved woody terrestrial sediments that were the subject of previous studies. This study continues the investigation using geochemical (δ<sup>13</sup>C, δ<sup>15</sup>N, δ<sup>34</sup>S) and palynological characteristics of these formerly terrestrial sediments to determine if swamps and/or marshes existed at the time of deposition. The first site is located ∼20 km southeast of Horn Island, Mississippi (MS) and the core has terrestrial sediments radiocarbon dated to 11,066–10,228 (2<i>σ</i>) calibrated years BP (early Holocene). The second site is the “Alabama Underwater Forest” located ∼13 km south of Gulf Shores, Alabama (AL) and the cores have terrestrial sediments optically stimulated luminescence dated to 63 ka (±10 ka, 2σ) to 72 ka (±16 ka, 2<i>σ</i>) (late Pleistocene). Geochemical results for the MS sediments indicate a swamp-to-freshwater marsh transitional series, whereas the AL sediments indicate a swamp-to-saltwater marsh transitional series, both supported by palynological results. Further exploration of the geochemical results using linear discriminant analysis, trained with published geochemical data, supports the swamp and marsh interpretations. We conclude that the near-pristine preservation of these woody deposits is not solely due to physical mechanisms, such as rapid burial, but is also coupled with anoxia- and euxinia-driven biogeochemical reactions promoting wood and woody debris preservation in swamp and marsh environments.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011489","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141488034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Open Access GNSS Data for Studies of the Lithosphere 用于岩石圈研究的开放式全球导航卫星系统数据
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-07-01 DOI: 10.1029/2024GC011567
D. Sarah Stamps, Corné Kreemer
{"title":"Open Access GNSS Data for Studies of the Lithosphere","authors":"D. Sarah Stamps,&nbsp;Corné Kreemer","doi":"10.1029/2024GC011567","DOIUrl":"https://doi.org/10.1029/2024GC011567","url":null,"abstract":"<p>Various types of Global Navigation Satellite System (GNSS) data are used for a wide range of applications. When modeled correctly, millimeter precision daily GNSS position time-series yield velocities and other derived products that can be used for investigations of lithospheric processes and properties. In this review paper, we describe the specific types of GNSS data and data products that are valuable for studies of the lithosphere, such as coseismic offsets, post-seismic decay in time-series, seasonal signals, secular velocities, and strain rates, and how those data are derived. We also discuss the applications of several types of GNSS data and data products. We provide open access resources for precision GNSS daily position time-series, quality secular velocity solutions, and daily GNSS RINEX files for researchers interested in processing their own data.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011567","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141536807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Oxidized Sulfur Species in Slab Fluids as a Source of Enriched Sulfur Isotope Signatures in Arcs 作为弧中富集硫同位素特征来源的板岩流体中的氧化硫物种
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-06-29 DOI: 10.1029/2024GC011542
Patrick Beaudry, Dimitri A. Sverjensky
{"title":"Oxidized Sulfur Species in Slab Fluids as a Source of Enriched Sulfur Isotope Signatures in Arcs","authors":"Patrick Beaudry,&nbsp;Dimitri A. Sverjensky","doi":"10.1029/2024GC011542","DOIUrl":"https://doi.org/10.1029/2024GC011542","url":null,"abstract":"<p>Recycling of oxidized sulfur from subducting slabs to the mantle wedge provides simultaneous explanations for the elevated oxygen fugacity (<i>f</i>O<sub>2</sub>) in subduction zones, their high hydrothermal and magmatic sulfur outputs, and the enriched sulfur isotopic signatures (i.e., δ<sup>34</sup>S &gt; 0‰) of these outputs. However, a quantitative understanding of the abundance and speciation of sulfur in slab fluids consistent with high pressure experiments is lacking. Here we analyze published experimental data for anhydrite solubility in H<sub>2</sub>O-NaCl solutions to calibrate a high-pressure aqueous speciation model of sulfur within the framework of the deep earth water model. We characterize aqueous complexes, required to account for the high experimental anhydrite solubilities. We then use this framework to predict the speciation and solubility of sulfur in chemically complex fluids in equilibrium with model subducting mafic and ultramafic lithologies, from 2 to 3 GPa and 400 to 800°C at log <i>f</i>O<sub>2</sub> from FMQ-2 to FMQ+4. We show that sulfate complexes of calcium and sodium markedly enhance the stability of sulfate in moderately oxidized fluids in equilibrium with pyrite at <i>f</i>O<sub>2</sub> conditions of FMQ+1 to +2, causing large sulfur isotope fractionations up to 10‰ in the fluid relative to the slab. Such fluids could impart oxidized, sulfur-rich and high δ<sup>34</sup>S signatures to the mantle wedge that are ultimately transferred to arc magmas, without the need to invoke <sup>34</sup>S-rich subducted lithologies.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011542","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141488967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Source-To-Sink Analysis in the Mesozoic SW Junggar Basin, Central Asia: Evidence From Detrital Garnet and Tourmaline Geochemistry 中亚中生代西南准噶尔盆地的源-汇分析:来自底质石榴石和电气石地球化学的证据
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-06-29 DOI: 10.1029/2024GC011455
X. Guan, C. Wu, Y. Xu, J. Saylor, C. Lin, W. Zhang
{"title":"Source-To-Sink Analysis in the Mesozoic SW Junggar Basin, Central Asia: Evidence From Detrital Garnet and Tourmaline Geochemistry","authors":"X. Guan,&nbsp;C. Wu,&nbsp;Y. Xu,&nbsp;J. Saylor,&nbsp;C. Lin,&nbsp;W. Zhang","doi":"10.1029/2024GC011455","DOIUrl":"https://doi.org/10.1029/2024GC011455","url":null,"abstract":"<p>Source-to-sink systems respond to and therefore potentially record topographic and tectonic changes. North of the Tian Shan Belt, the Sikeshu subbasin of the SW Junggar Basin transitioned from active extension in the Triassic to post-extensional subsidence in the Jurassic-Cretaceous. Sediment in the Sikeshu subbasin has been shown to be derived from the Tianshan. However, the details of the source-to-sink system remain unclear and discrepancies exist between proxy records. The heavy minerals in the Middle Triassic in the Sikeshu subbasin are dominated by garnets. To investigate the garnet sources and decipher the Mesozoic source-to-sink evolution, we conducted petrological and sedimentary analysis and detrital garnet and tourmaline geochemistry. We found that the geochemistry of garnets in the Middle Triassic sandstone is most consistent with that of the skarns in the Yili Block (YB) in Tianshan, while the geochemistry of 55%–84% of garnets in other Mesozoic sandstones is consistent with that of garnets in amphibolites in the YB. The geochemistry of the tourmalines since the Upper Triassic is consistent with that of the meta-sedimentary rocks in the YB and Central Tianshan Block. The dominance of garnets sourced from skarns in the Middle Triassic probably indicates a near-source point provenance and the broader range of garnet compositions from the Upper Triassic–Lower Cretaceous suggests multiple sources. We infer that the point source changed to multiple sources, which is consistent with the zircon spectra changing from unimodal to multimodal. This change reflects the expansion of the drainage that accompanies a change from active rifting to a post-rift stage.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011455","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141488984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A Detailed Reconstruction of the Woodlark Basin 详细重建云雀盆地
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-06-29 DOI: 10.1029/2023GC011410
E. K. Benyshek, B. Taylor, A. M. Goodliffe
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