Geochemistry Geophysics Geosystems最新文献

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Nd Isotopic Equilibration During Channelized Melt Transport Through the Lithosphere: A Feasibility Study Using Idealized Numerical Models 通过岩石圈的通道化熔融迁移过程中的钕同位素平衡:使用理想化数值模型的可行性研究
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-30 DOI: 10.1029/2024GC011593
Mousumi Roy, G. Lang Farmer, Kellen Malone
{"title":"Nd Isotopic Equilibration During Channelized Melt Transport Through the Lithosphere: A Feasibility Study Using Idealized Numerical Models","authors":"Mousumi Roy, G. Lang Farmer, Kellen Malone","doi":"10.1029/2024GC011593","DOIUrl":"https://doi.org/10.1029/2024GC011593","url":null,"abstract":"<p>This study is motivated by the observed variability in trace element isotopic and chemical compositions of primitive (Si<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>O</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 <mo><</mo>\u0000 </mrow>\u0000 <annotation> ${mathrm{O}}_{2}< $</annotation>\u0000 </semantics></math>52 wt %) basalts in southwest North America (SWNA) during the Cenozoic transition from subduction to extension. Specifically, we focus on processes that may explain the enigmatic observation that in some localities, basalts with low Ta/Th, consistent with parental melts in a subduction setting, have <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>ε</mi>\u0000 <mrow>\u0000 <mi>N</mi>\u0000 <mi>d</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${varepsilon }_{Nd}$</annotation>\u0000 </semantics></math> signatures consistent with continental lithospheric mantle (CLM). In locations with the oldest CLM (Proterozoic and Archean), Cenozoic basalts with low Ta/Th have <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>ε</mi>\u0000 <mrow>\u0000 <mi>N</mi>\u0000 <mi>d</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${varepsilon }_{Nd}$</annotation>\u0000 </semantics></math> well below zero. We model channelized magma transport through the CLM using simple 1D transport models to explore the extent to which diffusive and reactive mass exchange can modify Nd isotopic compositions via open system melt-wallrock interactions. For geologically reasonable channel spacings and volume fractions, we quantify the reactive assimilation rates required for incoming melt with a different <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>ε</mi>\u0000 <mrow>\u0000 <mi>N</mi>\u0000 <mi>d</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${varepsilon }_{Nd}$</annotation>\u0000 </semantics></math> than the wall-rock to undergo a substantial isotopic shift during <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>≈</mo>\u0000 </mrow>\u0000 <annotation> ${approx} $</annotation>\u0000 </semantics></math>10 km channelized melt transport. In the presence of grain boundaries, e","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011593","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359900","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
Paleomagnetic Constraints on the Rapid Plate Shift of North China Block During the Jurassic From ∼155 Ma Dykes and Sills 从∼155 Ma岩体和岩屑看侏罗纪时期华北地块快速板块移动的古地磁制约因素
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-28 DOI: 10.1029/2024GC011671
Pengfei Wang, Zhiyu Yi, Joseph G. Meert, Yu-Shu Liu, Silin Yang, Fei Wang, Zaijun Li, Baochun Huang
{"title":"Paleomagnetic Constraints on the Rapid Plate Shift of North China Block During the Jurassic From ∼155 Ma Dykes and Sills","authors":"Pengfei Wang,&nbsp;Zhiyu Yi,&nbsp;Joseph G. Meert,&nbsp;Yu-Shu Liu,&nbsp;Silin Yang,&nbsp;Fei Wang,&nbsp;Zaijun Li,&nbsp;Baochun Huang","doi":"10.1029/2024GC011671","DOIUrl":"https://doi.org/10.1029/2024GC011671","url":null,"abstract":"<p>A large-scale apparent polar wander occurred during the Jurassic interval, which is interpreted as true polar wander (TPW). As the motion is nearly orthogonal to the TPW axis, the North China Block (NCB) experienced the largest latitudinal and environmental changes and provides unique constraints on Jurassic TPW. However, due to the lack and uneven quality of paleomagnetic data, TPW records in North China are controversial. Here, we report a new paleomagnetic pole (80.8°N, 13.0°E, A<sub>95</sub> = 7.4°) from the late Jurassic sills and dykes that intrude the Nandaling and Xiahuayuan formations in the NCB. The new pole places the NCB at 36.8° ± 7.4°N at 155 ± 3.4 Ma, using Beijing as the reference site. Combined with the reliable Jurassic poles, our study reveals a large, steady southward shift of 37.3° ± 7.2° for the NCB during the Middle and Late Jurassic, and reflects a component of TPW. The position of ∼155 Ma pole also supports significant TPW prior to ∼160 Ma and agrees with proposals attributing the diachronous 165–155 Ma aridification across the Eastern Asian blocks.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011671","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359927","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
Miocene Alkaline Basaltic Magmatism in Northeastern Tibetan Plateau: Implications for Mantle Evolution and Plateau Outward Growth 青藏高原东北部中新世碱性玄武岩岩浆活动:对地幔演化和高原向外生长的影响
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-27 DOI: 10.1029/2024GC011601
Yue Che, Dong Liu, Zhidan Zhao, Yaoling Niu, Fang-Zhen Teng, Donald J. DePaolo, Xuehui Yu, Di-Cheng Zhu, Ningyuan Qi, Xuanxue Mo
{"title":"Miocene Alkaline Basaltic Magmatism in Northeastern Tibetan Plateau: Implications for Mantle Evolution and Plateau Outward Growth","authors":"Yue Che,&nbsp;Dong Liu,&nbsp;Zhidan Zhao,&nbsp;Yaoling Niu,&nbsp;Fang-Zhen Teng,&nbsp;Donald J. DePaolo,&nbsp;Xuehui Yu,&nbsp;Di-Cheng Zhu,&nbsp;Ningyuan Qi,&nbsp;Xuanxue Mo","doi":"10.1029/2024GC011601","DOIUrl":"https://doi.org/10.1029/2024GC011601","url":null,"abstract":"<p>The widespread Cenozoic alkaline magmatism within and around the Tibetan Plateau offers a prime opportunity to probe the nature of the mantle at the depths where basalt magmas originate. The close temporal and spatial relationship between volcanism and regional strike-slip fault systems also helps better understand the geodynamics of outward growth of the plateau in response to the continued India-Asia convergence. We present a comprehensive study of the deeply sourced alkaline basalts formed along the Kunlun strike-slip fault with the aim of understanding their petrogenesis and the composition of mantle sources beneath the northeastern Tibetan Plateau. High Nb/U and Ce/Pb ratios and relatively depleted bulk-rock Sr-Nd-Pb isotope compositions corroborate the mantle origin of these alkaline basalts. Homogeneous and low <sup>87</sup>Sr/<sup>86</sup>Sr of clinopyroxene indicates negligible crustal contamination during magmatic evolution. Low δ<sup>26</sup>Mg in the alkaline basalts and positive correlations with Hf/Sm and Ti/Ti* indicate that the basalts were derived from mantle that was metasomatized by melts derived from sedimentary carbonates during the Paleo-Tethyan seafloor subduction. Based on <sup>40</sup>Ar/<sup>39</sup>Ar dating results, it appears that the alkaline basaltic magmatism in the northeastern Tibetan Plateau occurred simultaneously with Kunlun strike-slip faulting. These observations suggest that the India-Asia convergence must have reactivated ancient subduction plate boundaries and resulted in strike-slip faulting along these suture zones within and around the Tibetan Plateau. The eruption of low-volume and deeply rooted alkaline basalts may have been controlled by fractures associated with the strike-slip fault systems.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011601","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359909","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
Dependence of Simulated Fault Gouge Frictional Behavior on Mineral Surface Chemistry Quantified by Cation Exchange Capacity 通过阳离子交换容量量化模拟断层冲沟摩擦行为与矿物表面化学性质的关系
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-21 DOI: 10.1029/2024GC011678
Matt J. Ikari, Marianne Conin
{"title":"Dependence of Simulated Fault Gouge Frictional Behavior on Mineral Surface Chemistry Quantified by Cation Exchange Capacity","authors":"Matt J. Ikari,&nbsp;Marianne Conin","doi":"10.1029/2024GC011678","DOIUrl":"https://doi.org/10.1029/2024GC011678","url":null,"abstract":"<p>The slip behavior of crustal faults is known to be controlled by the composition of the fault gouge, but the exact mechanisms, especially considering the role of water-rock interactions, are still under investigation. Here, we use a geochemical approach measuring the cation exchange capacity (CEC) of several phyllosilicate minerals and non-clays, using CEC as a proxy for the ability to bind water to the mineral surfaces and/or develop electrostatic forces between particles. Laboratory shearing experiments show that low CEC materials (&lt;3 mEq/100 g) tend to exhibit high friction, low cohesion, and velocity-weakening frictional behavior. Phyllosilicate minerals exhibit CEC values up to 78 mEq/100 g and correspondingly lower friction coefficients, higher cohesion, and a tendency for velocity-strengthening friction. Zeolite behavior is atypical, exhibiting a high CEC value typical of phyllosilicates but the strength and frictional characteristics of a non-clay with low CEC. This suggests that the structure of the mineral is important for non-phyllosilicates. For phyllosilicates, our results can be explained by water bound to mineral surfaces, creating bridges of hydrogen or van der Waals bonds between particles. The enhanced particle bonding for high CEC materials is consistent with high cohesion under zero effective stress conditions, and lowered friction by trapping bound water between the mineral surfaces under normal load. Bound water may explain the tendency for velocity-strengthening friction in high CEC materials by hindering a Dieterich-type time-dependent frictional strengthening mechanism.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011678","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142276554","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
Paleomagnetism-Based Chronology of Holocene Lava Flows at Mt Ruapehu, Aotearoa New Zealand 基于古地磁学的新西兰奥特亚罗瓦鲁佩胡山全新世熔岩流年表
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-19 DOI: 10.1029/2024GC011745
Pedro Doll, Gillian M. Turner, Ben M. Kennedy, Alexander R. L. Nichols, Annika Greve, Jim W. Cole, Shaun R. Eaves, Dougal B. Townsend, Graham S. Leonard, Chris E. Conway
{"title":"Paleomagnetism-Based Chronology of Holocene Lava Flows at Mt Ruapehu, Aotearoa New Zealand","authors":"Pedro Doll,&nbsp;Gillian M. Turner,&nbsp;Ben M. Kennedy,&nbsp;Alexander R. L. Nichols,&nbsp;Annika Greve,&nbsp;Jim W. Cole,&nbsp;Shaun R. Eaves,&nbsp;Dougal B. Townsend,&nbsp;Graham S. Leonard,&nbsp;Chris E. Conway","doi":"10.1029/2024GC011745","DOIUrl":"https://doi.org/10.1029/2024GC011745","url":null,"abstract":"<p>Dating young lava flows is essential for understanding volcano's eruption frequency, yet challenging due to methodological limitations of commonly used dating techniques. Ruapehu (Aotearoa New Zealand) produced many lava flows during the Holocene, but constraints on the timing of these eruptions are scarce. Here, we use paleomagnetic dating to deliver new eruption ages of 18 lava flows with uncertainties ranging between 500 and 2,700 years (at the 95% confidence level). Comparison between lava flows' paleomagnetic directions and a local paleosecular variation record indicates that the large lava flow field located on the Whakapapa area was emplaced during at least three distinct eruptive episodes between 10600 and 7400 BP. Two of these episodes closely followed a large collapse event that affected Ruapehu's northern area and generated large volumes of lava between 10600 and 8800 BP, with the third episode producing less voluminous lava flows between 8100 and 7400 BP. Following a smaller collapse of the southeastern sector of the edifice at ca. 5300 BP, several low-volume lava flows were emplaced during at least two distinct eruptive episodes prior to ca. 1000 BP, which supplied the Whangaehu valley with lava. The youngest age inferred from our data represents the youngest eruption age provided for a lava flow outside Ruapehu's summit region. This research provides greater detail to the Holocene effusive chronology at Ruapehu, shedding light on partial cone reconstructions after edifice collapses during the Holocene, and the time relationships between trends observed in its effusive and explosive activity.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011745","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142275091","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
Core-Top Calibrations for Element-To-Calcium Proxies of Seawater Properties in Bamboo Corals (Keratoisididae) From the South China Sea 南中国海竹珊瑚(Keratoisididae)海水性质的元素-钙代用指标的核顶校准
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-18 DOI: 10.1029/2024GC011677
Xiaoli Zhou, Haozhuang Wang, Yuhan Zhu, Yue Wang, Les Watling, Zhimin Jian, Peijun Qiao
{"title":"Core-Top Calibrations for Element-To-Calcium Proxies of Seawater Properties in Bamboo Corals (Keratoisididae) From the South China Sea","authors":"Xiaoli Zhou,&nbsp;Haozhuang Wang,&nbsp;Yuhan Zhu,&nbsp;Yue Wang,&nbsp;Les Watling,&nbsp;Zhimin Jian,&nbsp;Peijun Qiao","doi":"10.1029/2024GC011677","DOIUrl":"https://doi.org/10.1029/2024GC011677","url":null,"abstract":"<p>Bamboo corals are promising archives of paleoceanographic conditions. Existing calibrations for element-to-calcium ratio (El/Ca) proxies of bamboo corals, however, are not necessarily calibrated to contemporaneous environmental parameters, thus weakening the reliability of the proxies. Here, we aim at calibrating the proxies by comparing El/Ca in the outermost surface of the calcareous skeletons of live-collected bamboo corals from the South China Sea (SCS) with modern environmental records. Statistical analysis suggests that Mg/Ca and Ba/Ca can be expressed as a function of in situ seawater temperature and silicate concentration, respectively, that is, Mg/Ca (mmol/mol) = 2.17 ± 0.51 * <i>T</i> (°C) + 74.90 ± 2.66 and Ba/Ca (μmol/mol) = 0.070 ± 0.020 * Silicate (μmol/kg) + 7.27 ± 2.42. The slope of the Mg/Ca-<i>T</i> equation from this study is slightly different from that in a previous study on bamboo corals, likely due to taxonomic and/or geographic differences of the corals and/or differences in sampling strategy and pre-treatment method. Intra- and inter-coral variations have small effects on Mg/Ca, yielding an uncertainty of 2.04 mmol/mol in Mg/Ca (95% confidence interval), equivalent to 0.94°C in estimated temperature. The slope of the Ba/Ca-silicate equation is the same as that in a previous study, suggesting little effect of geographic difference on Ba/Ca. Intra- and inter-coral variations in Ba/Ca are larger than those in Mg/Ca, possibly reflecting incorporation of multiple Ba-rich particulate phases and/or highly variable nutrient concentrations in the micro-environment near corals. These new calibrations allow reconstructions of paleo-temperature and nutrient concentration in the SCS on decadal and longer timescales.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011677","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142244879","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
Dynamic Recrystallization of Olivine During Simple Shear: Evolution of Microstructure and Crystallographic Preferred Orientation From Full-Field Numerical Simulations 简单剪切过程中橄榄石的动态再结晶:从全场数值模拟看显微结构和晶体学优先取向的演变
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-18 DOI: 10.1029/2023GC011212
Y. Yu, A. Griera, E. Gomez-Rivas, P. D. Bons, D. García-Castellanos, B. Hao, R. A. Lebensohn, M.-G. Llorens
{"title":"Dynamic Recrystallization of Olivine During Simple Shear: Evolution of Microstructure and Crystallographic Preferred Orientation From Full-Field Numerical Simulations","authors":"Y. Yu,&nbsp;A. Griera,&nbsp;E. Gomez-Rivas,&nbsp;P. D. Bons,&nbsp;D. García-Castellanos,&nbsp;B. Hao,&nbsp;R. A. Lebensohn,&nbsp;M.-G. Llorens","doi":"10.1029/2023GC011212","DOIUrl":"https://doi.org/10.1029/2023GC011212","url":null,"abstract":"<p>Upper mantle deformation is mainly controlled by the mechanical behavior of olivine. Crystallographic preferred orientations (CPOs) develop in olivine due to crystal-plastic deformation during mantle flow, where the a-axes of olivine polycrystalline aggregates are aligned with the flow direction. Therefore, the observed CPO in olivine-rich rocks is used as an indicator of the mantle flow direction. Experimental data show that olivine rheology is strongly controlled by the microstructure. While the influence of plastic deformation is in general well characterized, the role of dynamic recrystallization during deformation is not totally understood, limiting our ability to interpret the deformation history of naturally deformed rocks. This contribution presents microdynamic numerical simulations of olivine polycrystalline aggregates with different iron content (i.e., fayalite content) with the aim of exploring the CPO and grain size response to dynamic recrystallization. We use a full-field approach with an explicit simulation of viscoplastic deformation and dynamic recrystallization processes under simple shear boundary conditions up to high strain. The simulations show that the CPOs are similar and practically reach the same maximum regardless of the iron content. CPOs are characterized by a single cluster of a-axis and two-clusters of b-axis, reveling a joint activity of the easy glide [100](010) and the moderate strength [100](010) slip systems. High-strain domains of our models are consistent with experimental results, showing an A-type fabric with double maxima, and where the CPO is aligned with the shear direction. The model provides a deeper understanding of the dynamic recrystallization influence on olivine CPOs resulting from plastic deformation.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011212","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142244880","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
Formation of a Large Cold Groundwater Mantle Helium Anomaly and High Temperature Geothermal Resources in Response to Bimodal Magmatism Near Roosevelt Hot Springs and Utah FORGE, Milford Valley, Southwest Utah 犹他州西南部米尔福德山谷罗斯福温泉和犹他州 FORGE 附近双峰岩浆作用形成的大型冷地下水地幔氦异常和高温地热资源
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-17 DOI: 10.1029/2024GC011539
Stuart F. Simmons, Stefan Kirby
{"title":"Formation of a Large Cold Groundwater Mantle Helium Anomaly and High Temperature Geothermal Resources in Response to Bimodal Magmatism Near Roosevelt Hot Springs and Utah FORGE, Milford Valley, Southwest Utah","authors":"Stuart F. Simmons,&nbsp;Stefan Kirby","doi":"10.1029/2024GC011539","DOIUrl":"https://doi.org/10.1029/2024GC011539","url":null,"abstract":"<p>A large mantle helium anomaly and separate domains of high heat flow are the predominant manifestations of bimodal magmatic activity in the Milford valley. The mantle helium anomaly (1.9–2.6 R/Ra) covers 270 km<sup>2</sup> and is subdivided into two separated domains: a cold shallow groundwater regime and high temperature hydrothermal activity. The zone of anomalous heat flow covers &gt;100 km<sup>2</sup> and is also subdivided into two adjacent domains, comprising hydrothermal activity at Roosevelt Hot Springs (RHS) (3–7 W/m<sup>2</sup>) and conductive heat flow (100–180 mW/m<sup>2</sup>). While the transfer of heat and mantle helium at RHS are coupled, heat and helium transfer are decoupled in the adjacent cold groundwater regime to the west. Both the mantle helium and geothermal anomalies are attributed to recent mafic-felsic magmatic intrusions of &gt;400 km<sup>3</sup>, however, the absence of volcanic eruptions &lt;500,000 years indicates magmas stall before rising to shallow crustal level &lt;10 km depth. Deep level magmatism produces a felsic composition melt, which is inferred to be responsible for the widespread and near uniform range of diluted mantle helium values. A thick and impermeable mass of crystalline granitic basement rock at the mid-crustal level divides the ascent of mantle helium into separate flow paths. It may also impede the rise of buoyant magma trapping thermal energy that facilitates partial melting, slow cooling, and development of a thick thermal aureole. Partitioning of convective and conductive thermal regimes and independent flow paths supplying deeply derived helium characterize the development of a large long-lived magma-related geothermal system.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011539","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142245053","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 REE Inverse Model From Bulk Distribution Coefficients and Boundary Conditions: Results for Shield and Rejuvenated Stage Hawaiian Volcanoes 根据块体分布系数和边界条件建立的 REE 反演模型:盾状火山和年轻化阶段夏威夷火山的研究结果
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-16 DOI: 10.1029/2024GC011651
M. J. Carr, M. D. Feigenson, E. Gazel
{"title":"A REE Inverse Model From Bulk Distribution Coefficients and Boundary Conditions: Results for Shield and Rejuvenated Stage Hawaiian Volcanoes","authors":"M. J. Carr,&nbsp;M. D. Feigenson,&nbsp;E. Gazel","doi":"10.1029/2024GC011651","DOIUrl":"https://doi.org/10.1029/2024GC011651","url":null,"abstract":"&lt;p&gt;A major challenge in mantle geochemistry is determining the source composition and melt fraction involved in melting. We provide a new Rare-Earth Element (REE) inverse model that provides source concentration, source and melt mineral modes, and melt fraction based on the difference between separate determinations of bulk distribution coefficients and constrained by boundary conditions. An analytical inverse of the batch melting equation provides expressions for source, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;mi&gt;o&lt;/mi&gt;\u0000 &lt;mi&gt;i&lt;/mi&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${C}_{o}^{i}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and bulk distribution coefficient of the mantle, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;D&lt;/mi&gt;\u0000 &lt;mi&gt;o&lt;/mi&gt;\u0000 &lt;mi&gt;i&lt;/mi&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${D}_{o}^{i}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, with two unknowns, the initial concentration of La in the mantle, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;mi&gt;o&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${C}_{o}^{La}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and &lt;i&gt;P&lt;/i&gt;&lt;sup&gt;&lt;i&gt;i&lt;/i&gt;&lt;/sup&gt;, the bulk distribution coefficient of the melt. We traverse through a range of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;mi&gt;o&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${C}_{o}^{La}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; steps and examine thousands of melt modes, &lt;i&gt;P&lt;/i&gt;&lt;sup&gt;&lt;i&gt;i&lt;/i&gt;&lt;/sup&gt;, at each step. Thousands of trial melt modes fail by generating &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;D&lt;/mi&gt;\u0000 &lt;mi&gt;o&lt;/mi&gt;\u0000 &lt;mi&gt;i&lt;/mi&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${D}_{o}^{i}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; that are inconsistent with partition coefficients. Many surviving trials cannot be inverted to estimate a mantle mode. Other boundary conditions eliminate","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011651","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142234913","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
3D Shear Velocity Structure of the Caribbean—Northwestern South America Subduction Zone From Ambient Noise and Ballistic Rayleigh Wave Tomography 从环境噪声和弹道瑞雷波断层扫描看加勒比海-南美洲西北部俯冲带的三维剪切速度结构
IF 2.9 2区 地球科学
Geochemistry Geophysics Geosystems Pub Date : 2024-09-12 DOI: 10.1029/2024GC011612
Wenpei Miao, John Cornthwaite, Alan Levander, Fenglin Niu, Michael Schmitz, Guoliang Li, Viviana Dionicio, German Prieto
{"title":"3D Shear Velocity Structure of the Caribbean—Northwestern South America Subduction Zone From Ambient Noise and Ballistic Rayleigh Wave Tomography","authors":"Wenpei Miao,&nbsp;John Cornthwaite,&nbsp;Alan Levander,&nbsp;Fenglin Niu,&nbsp;Michael Schmitz,&nbsp;Guoliang Li,&nbsp;Viviana Dionicio,&nbsp;German Prieto","doi":"10.1029/2024GC011612","DOIUrl":"https://doi.org/10.1029/2024GC011612","url":null,"abstract":"<p>The Caribbean-South America subduction zone is a flat subduction zone, with Laramide-style thick-skinned uplifts occurring in the Merida Andes, Sierra de Perija Range, and Santa Marta Massif. Geodetic measurements and historical seismicity show this region is storing strain energy and is capable of a mega-thrust earthquake (<i>M</i> ≥ 8.0). Previous seismic investigations of the lithosphere and upper mantle in this area are either very large scale, very local, or only peripheral to this area; therefore, details of the Caribbean plate subduction geometry beneath the Maracaibo block remain unclear. In this study, we used a new data set acquired by the Caribbean-Merida Andes seismic experiment (CARMA), which comprised 65 temporary broadband stations and 44 permanent stations from the Colombian and Venezuelan national seismic networks. We jointly inverted ambient noise Rayleigh wave <i>Z</i>/<i>H</i> ratios, phase velocities in the 8–30 s band and ballistic Rayleigh wave phase velocities in 30–80 s band to construct a 3-D S-wave velocity model in the area between 75°–65°W and 5°–12°N. The 3-D model reveals a general increase in crust thickness from the trench to the southeast. An anomalous area is the Lake Maracaibo, which is underlaid by the thinnest crystalline crust in the region. This observation may indicate that the Maracaibo block is experiencing a contortion deformation within the crust. We also identified a high velocity anomaly above the subducting Caribbean slab, likely representing a detached piece of eclogitized Caribbean large igneous province from the base of the Maracaibo block. Additionally, our <i>V</i><sub><i>s</i></sub> model clearly indicates a slab tear within the subducted Caribbean slab, approximately beneath the Oca-Ancon Fault.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011612","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174167","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
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