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Serravallian–Tortonian (Miocene) folding in the Amakusa region, northern Ryukyu arc: Possible subduction resumption of the Philippine Sea Plate 琉球弧北部天草地区的塞拉瓦利-托尔屯纪(中新世)褶皱:菲律宾海板块可能的俯冲恢复
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-06-18 DOI: 10.1111/iar.12528
Kentaro Ushimaru, Atsushi Yamaji, Naoto Ishikawa
{"title":"Serravallian–Tortonian (Miocene) folding in the Amakusa region, northern Ryukyu arc: Possible subduction resumption of the Philippine Sea Plate","authors":"Kentaro Ushimaru,&nbsp;Atsushi Yamaji,&nbsp;Naoto Ishikawa","doi":"10.1111/iar.12528","DOIUrl":"https://doi.org/10.1111/iar.12528","url":null,"abstract":"<p>Eocene to Lower Miocene coal-bearing formations in northern and western Kyushu, northern Ryukyu arc, are folded, and the horizontal compression has been attributed to the opening of the Japan Sea or to the significant movement along the Median Tectonic Line and its southwestern extension. However, the timing and implication of the folding are not well understood. To deal with these issues, we studied the Amakusa region where the folded Eocene strata with a total thickness of a few kilometers. Paleomagnetic directions of Middle Miocene intrusions and of Late Miocene lavas were measured in this study to apply the fold test to judge the relative timing of the folding and magmatism. As a result, the concentration of the directions was improved by the tilt-correction, indicating the folding younger than the magmatism. Our detailed geological mapping revealed that the folding is older than a horizontally-lying basaltic lava which yielded a K–Ar age of 6.8 Ma, because folded Eocene formations were truncated and unconformably blanketed by the lava. In addition, we found that some of the normal faults trending perpendicular to the folds were reactivated as transfer faults after the normal faulting which also postdated the magmatism. This reactivation is concordant with the above-mentioned relative timing. Synthesizing geological data from surrounding regions, we conclude that the folding was probably contemporaneous with the Taiwan-Shinji fold belt which grew in the Ryukyu and southwest Japan backarcs. Since the simultaneous compression affected not only these regions but also northeast Japan, the compression possibly resulted from the resumed subduction of the Philippine Sea Plate in the Serravallian–Tortonian time.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141424930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Geochronology and geochemistry of granitoids from northern Alxa, northwest China: Petrogenesis and tectonic implications 中国西北阿拉善北部花岗岩的地质年代和地球化学:岩石成因和构造影响
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-05-20 DOI: 10.1111/iar.12525
Chunjiao Wu, Zhenyi Wang, Jin Zhang, Jianfeng Liu, Beihang Zhang, Rongguo Zheng, Jun Ma, Jie Hui, Heng Zhao
{"title":"Geochronology and geochemistry of granitoids from northern Alxa, northwest China: Petrogenesis and tectonic implications","authors":"Chunjiao Wu,&nbsp;Zhenyi Wang,&nbsp;Jin Zhang,&nbsp;Jianfeng Liu,&nbsp;Beihang Zhang,&nbsp;Rongguo Zheng,&nbsp;Jun Ma,&nbsp;Jie Hui,&nbsp;Heng Zhao","doi":"10.1111/iar.12525","DOIUrl":"https://doi.org/10.1111/iar.12525","url":null,"abstract":"<p>Multiple branch oceans existed in the Paleo-Asian Ocean (PAO), but their closure times are in dispute and unclear, which constrains our understanding of the final closure time of the PAO and the tectonic evolution of the Central Asian Orogenic Belt (CAOB). This study focuses on the Permian plutons of the northern Alxa, which is located in the middle segment of the southern CAOB that recorded the final subduction history of the PAO. We performed the 1:50000 mapping, whole-rock geochemistry, geochronology, and Sr-Nd-Hf isotopic analysis and compiled the Sr-Nd-Hf isotopic compositions and whole-rock geochemical data of igneous rocks from the northern Alxa. LA-ICP-MS zircon U–Pb dating reveals the study plutons emplaced in the Early Permian (285–296 Ma). Whole-rock geochemical data show the intrusion belongs to medium-K calc-alkaline peraluminous highly fractionated I-type granite, enriched in Rb, K, Th, Pb, and depleted in Nb, Ta, Ti, Sr, and P elements, which suggest a subduction arc-related setting and metaluminous to weak peraluminous parental magma. The weak negative ε<sub>Nd</sub>(t) (from −2.3 to −1.2), relatively high I<sub>Sr</sub> (0.704772–0.708037) and depleted mantle model ages T<sub>DM</sub> (1.14–1.49 Ga), combining with weak negative to slightly positive ε<sub>Hf</sub>(t) (from −2.0 to +4.1) and crustal model ages T<sub>DM</sub><sup>C</sup> (1.18–1.43 Ga), indicate that the parental magma might originate from remelting of the Mesoproterozoic lower crust and mixing with mantle-derived materials. The field occurrence, deformation, and geochemical features, integrating with the compiled data and regional geology, show that the igneous rocks formed before or after the late Early Permian show different features in terms of deformation, zircon saturation temperatures, crustal thickness, potassium contents, and ε<sub>Hf</sub>(t) values. This might relate to the closure of the Yagan branch ocean of the PAO in northern Alxa.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141073689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A zone of columnar joints beneath the roof of a granitic pluton: The Okueyama granite, southwestern Japan 花岗岩岩体顶板下的柱状节理带:日本西南部的奥越山花岗岩
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-05-06 DOI: 10.1111/iar.12524
Masahiro Chigira, Hironori Kato
{"title":"A zone of columnar joints beneath the roof of a granitic pluton: The Okueyama granite, southwestern Japan","authors":"Masahiro Chigira,&nbsp;Hironori Kato","doi":"10.1111/iar.12524","DOIUrl":"https://doi.org/10.1111/iar.12524","url":null,"abstract":"<p>Igneous rocks are fractured during cooling from magma to form cooling joints, which are typically columnar joints in volcanic rocks, while orthogonal joints are considered typical for plutonic rocks. We performed a 3D study of joint systems in a granitic batholith of the Okueyama granite in western Japan, which has its roof and its internal structures from the roof to 1000 m downward exposed. We used an unmanned aerial vehicle (UAV) to observe the joints in outcrops from various angles. Based on our study, we propose a schematic model for joint systems in a granitic pluton. A granitic pluton has zones of rock columns below the roof and next to the wall. The rock column zone below the roof is as thick as 300 m, and its higher portions form steep cliffs, probably because of increased resistance to weathering. The axes of the rock columns are nearly vertical below the roof and gently plunge next to the walls, with high intersection angles with the wall. The distribution of columnar joints near only the roof and walls suggests that the granite cooled more rapidly near the roof and walls than in the core of the pluton. When the granite was jointed by parallel joints during cooling, the rock slabs between the parallel joints near the roof and the walls are subdivided into columns with polygonal cross-sections. This suggests that the granite was fractured by parallel joints at a temperature immediately below the solidus, after which the rock slabs were subdivided into rock columns during further cooling.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12524","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140844701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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
Arc volcanism initiated on the eastern margin of Eurasia during the Early Cretaceous: Geochemistry of the Takanokura volcanic rocks in the Abukuma Mountains, Northeast Japan 早白垩世欧亚大陆东缘的弧形火山活动:日本东北部阿武隈山脉高野仓火山岩的地球化学特征
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-04-29 DOI: 10.1111/iar.12523
Takahiro Yamamoto
{"title":"Arc volcanism initiated on the eastern margin of Eurasia during the Early Cretaceous: Geochemistry of the Takanokura volcanic rocks in the Abukuma Mountains, Northeast Japan","authors":"Takahiro Yamamoto","doi":"10.1111/iar.12523","DOIUrl":"https://doi.org/10.1111/iar.12523","url":null,"abstract":"<p>The Early Cretaceous Takanokura Formation in the eastern part of the Abukuma Mountains consists of a lower felsic ignimbrite and upper intermediate lavas and volcaniclastic rocks, representing the initial arc-type in northeast Japan. In this study, I analyzed the major and trace element contents and Sr-Nd-Pb isotopic ratios of these eruptive products; then, I discussed their magma genesis based on their geochemical properties. Although igneous rocks of the same period in other localities of northeast Japan are characterized by the occurrence of adakites, these volcanism are composed of non-adakitic high- to medium-K andesite to rhyolite that are rich in large-ion lithophile elements and poor in high-field-strength elements and have low Sr/Y values and flat heavy rare earth element patterns. Furthermore, these rocks have high radiogenic Pb isotopic ratios. The rhyolite and dacite have been thought to derive from crustal melting, whereas the andesite formed by the mixing of crustal felsic melts and mafic magmas generated by melting of the lithospheric mantle. Although previous studies attributed the formation of the Early Cretaceous adakites to the hot subduction of a mid-ocean ridge, recent global plate motion reconstructions reject this model. To generate magma from a cold slab and lithospheric mantle that does not spontaneously melt, the mantle wedge under northeast Japan must have experienced heating. During this period, the volcanic province along the eastern margin of Eurasia expanded rapidly toward the trench, forming grabens. Therefore, I concluded that the advance of the hot asthenosphere into the forearc region that led to this expansion, which caused the retreat of the subduction boundary of the paleo-Pacific plate to retreat and ultimately converted northeast Japan from an accretionary complex into a volcanically active region.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12523","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140814301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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
Deciphering the multistage magmatic processes in the Nuqara caldera, the northern Egyptian Nubian-Shield: Insights from zircon morphology and geochemistry 解密埃及北部努比亚地盾努卡拉火山口的多级岩浆过程:锆石形态学和地球化学的启示
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-04-27 DOI: 10.1111/iar.12522
Osama K. Dessouky
{"title":"Deciphering the multistage magmatic processes in the Nuqara caldera, the northern Egyptian Nubian-Shield: Insights from zircon morphology and geochemistry","authors":"Osama K. Dessouky","doi":"10.1111/iar.12522","DOIUrl":"https://doi.org/10.1111/iar.12522","url":null,"abstract":"<p>Trace elements in igneous zircon crystals exhibit variability within single crystals or among populations of crystals, demonstrating heightened sensitivity to changes in melt composition. The three distinct types of zircons in the Nuqara caldera complex (659 ± 16 Ma andesites, 602.3 ± 4.4 Ma rhyolites, and 589.4 ± 6.1 Ma rhyolite porphyry; A, B, and C, respectively) signify a collective geological history influencing the multistage magmatic evolution. Significantly, the studied zircons demonstrate growth rate and variable length-to-width ratios that progressively increase from A to C. Ti-in-zircon geothermometer (T<sub>Ti-in-zrc</sub> = 924°C) along with the internal structure and geochemistry of type A zircons, such as very weak cathodoluminescence (CL) brightness, zoning, and higher concentrations of some trace elements content, suggest their formation during the early, hotter, and less-evolved melt stage of volcanic activity. Type B zircons exhibit T<sub>Ti-in-zrc</sub> (833°C) and commonly display resorption with an absence of singular dark CL, indicating substantial reheating of the magma reservoir. The interaction between the incoming evolved magma and the resident magma results in the formation of zircon rims during the magma cooling, featuring significant overlaps in zircon trace elements. This final phase in the Nuqara caldera complex marks the complete hybridization of the initially distinct magmas, culminating in a gradual cooling process. The newly formed zircons (type C) are characterized by light CL features with weak zoning occurring either as the rim of the oscillatory zoned zircon or as an individual zircon grain. Their less evolved chemical signature and T<sub>Ti-in-zrc</sub> (708°C) highlight the significance of this final stage in shaping the overall geochemical and thermal evolution. The obtained zircon data, spanning from the initial crystallization to the subsequent recharge, mixing, and hybridization stages, delineate the discernible phases in the formation of the Nuqara caldera, providing insights into the transitions from subduction to collision-related geological processes.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140649522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Petrogenesis of S-type Ladakh granite and mafic microgranular enclaves in the southern margin of Ladakh batholith: An evidence of crust–mantle interaction during the collision between Indian and Eurasian plates 拉达克岩床南缘 S 型拉达克花岗岩和黑云母微晶飞地的岩石成因:印度板块与欧亚板块碰撞期间地壳与地幔相互作用的证据
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-04-10 DOI: 10.1111/iar.12520
C. Perumalsamy, S. Vijay Anand, R. Nagarajan, Bappa Mukherjee
{"title":"Petrogenesis of S-type Ladakh granite and mafic microgranular enclaves in the southern margin of Ladakh batholith: An evidence of crust–mantle interaction during the collision between Indian and Eurasian plates","authors":"C. Perumalsamy,&nbsp;S. Vijay Anand,&nbsp;R. Nagarajan,&nbsp;Bappa Mukherjee","doi":"10.1111/iar.12520","DOIUrl":"https://doi.org/10.1111/iar.12520","url":null,"abstract":"<p>The previous studies revealed the I-type Ladakh magmatism in the Andean-type southern margin of the Ladakh batholith (LB) was related to the subduction of the Neotethyan Ocean and India-Eurasia collision. However, LB's S-type granitic magmatism and associated mafic microgranular enclaves (MMEs) are poorly constrained. Here, we present the new data for S-type Ladakh granite (LG) and associated monzodiorite MMEs in the Andean-type orogeny in the southern margin of the Eurasian plate. The low SiO<sub>2</sub> (47.4–53.9 wt%), high K<sub>2</sub>O (1.56–3.21 wt%), Mg<sup>#</sup> (52–65), continental-arc tracer patterns, and slightly depleted to evolved Sr-Nd isotopic composition ((<sup>87</sup>Sr/<sup>86</sup>Sr)i = 0.7047–0.7166; ℇ<sub>Nd</sub> (<i>t</i> = 50 Ma) = (+1.40 to −8.92)) for MME suggest that they were derived from the phlogopite-bearing deep lithospheric mantle-source at a depth of 5.4–10.5 km depth with 810–870°C, 1.4–2.8 kbar, and enriched by sediment-melts addition into the mantle-wedge from subducting Neotethyan Oceanic slab. The mantle-derived ascending hot mafic magma mixing with felsic magma of the ancient northern Indian margin-derived, generates monzodiorite MME by assimilation and magma mixing processes. Plagioclase, amphibole, and biotite chemistry support the magma mixing processes. LG are characterized by high SiO<sub>2</sub> (63.4–75.0 wt%), K<sub>2</sub>O (3.93–5.67 wt%), CaO/Na<sub>2</sub>O ratio of &gt;0.3, differentiation index (90.27–97.46), normative corundum (1.0–2.8), A/CNK values (1.00–1.18), hypersthene (0.7–5.7), and low Al<sub>2</sub>O<sub>3</sub>, MgO, TiO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>. They also exhibit peraluminous, variable tracer elemental abundances, variable (<sup>87</sup>Sr/<sup>86</sup>Sr)i ratios (0.6967–0.7191), and high whole rock ℇ<sub>Nd</sub> (<i>t</i> = 50 Ma) values of −4.15 to −11.92) and ancient two-stage Nd model age of 1160 and 1858 Ma. These features suggest that S-type Ladakh granites were derived from the melting of ancient metagreywacke-dominated metasedimentary rocks of the northern Indian margin by a large amount of mafic magma underplating after subducted Neotethyan slab-rollback. The formation of LG and MMEs related to the Andean-type orogeny in the southern margin of the Eurasian plate.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140544463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Zircon U–Pb ages of granitic and mafic dikes associated with granitoids and metamorphic rocks of the Ryoke Belt in the eastern Kii Peninsula, southwest Japan 与日本西南部纪伊半岛东部良玉带花岗岩和变质岩相关的花岗岩和黑云母岩脉的锆石U-Pb年龄
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-04-05 DOI: 10.1111/iar.12521
Kazunori Zushida, Makoto Takeuchi, Takashi Nakajima, Sae Taniguchi, Yuxiao Li, Yoshihiro Asahara, Koshi Yamamoto
{"title":"Zircon U–Pb ages of granitic and mafic dikes associated with granitoids and metamorphic rocks of the Ryoke Belt in the eastern Kii Peninsula, southwest Japan","authors":"Kazunori Zushida,&nbsp;Makoto Takeuchi,&nbsp;Takashi Nakajima,&nbsp;Sae Taniguchi,&nbsp;Yuxiao Li,&nbsp;Yoshihiro Asahara,&nbsp;Koshi Yamamoto","doi":"10.1111/iar.12521","DOIUrl":"https://doi.org/10.1111/iar.12521","url":null,"abstract":"<p>Zircon U–Pb dates for felsic and intermediate to mafic dikes intruding into the Ryoke granitoids and metamorphic rocks at selected outcrops in the Takamiyama area of the eastern Kii Peninsula, southwest Japan, were determined along with their geology and petrography to reveal the history of Cretaceous magmatism. At each outcrop, the felsic and intermediate to mafic dikes exhibit specific structures that are indicative of magma intermingling and have coeval intrusion ages of ca. 81–77 Ma. Our zircon U–Pb data complement previously published data, suggesting that the mafic magmatism continued intermittently from 83 to 76 Ma in the Takamiyama area and that magmatism migrated eastward within the Ryoke Belt. A comparison of intrusion ages between a dike and a host Ryoke granitoid at one outcrop indicates that the host rock experienced ductile deformation at ~88 to ~83 Ma. Judging from the small number of zircons and the concordant date distributions, we didn't recognize the evidence suggesting the partial melting of the host rocks, as Nakajima et al. (Journal of the Geological Society of Japan, 2021, 127, 69–78) reported.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12521","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140351698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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
Characterization of serpentinization in olivine-orthopyroxene-H2O system revealed by thermogravimetric and multivariate statistical analyses 通过热重分析和多元统计分析揭示橄榄石-正辉石-H2O 体系中蛇纹石化的特征
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-04-02 DOI: 10.1111/iar.12519
Atsushi Okamoto, Shuhei Tanaka, Masaoki Uno, Otgonbayar Dandar, Kazuki Yoshida
{"title":"Characterization of serpentinization in olivine-orthopyroxene-H2O system revealed by thermogravimetric and multivariate statistical analyses","authors":"Atsushi Okamoto,&nbsp;Shuhei Tanaka,&nbsp;Masaoki Uno,&nbsp;Otgonbayar Dandar,&nbsp;Kazuki Yoshida","doi":"10.1111/iar.12519","DOIUrl":"https://doi.org/10.1111/iar.12519","url":null,"abstract":"<p>Thermogravimetric (TG) analyses were used to characterize the products and quantify the extent of serpentinization as a stepwise weight loss during heating (TG loss) or its derivative (DTG). Multivariate analyses are powerful tools for extracting information from complicated spectrum data; however, no studies have applied them to characterize serpentinites. In this study, hydrothermal experiments of olivine-H<sub>2</sub>O, olivine–orthopyroxene-H<sub>2</sub>O and orthopyroxene-H<sub>2</sub>O were conducted at 250–400°C and under vapor-saturated pressure. The product minerals observed were serpentine+brucite+magnetite in the olivine-H<sub>2</sub>O experiments and serpentine±talc in the orthoyroxene-H<sub>2</sub>O and olivine-orthopyroxene-H<sub>2</sub>O experiments. These results are consistent with those of previous studies; however, the positions and width of DTG peaks for individual minerals were varied depending on the experimental conditions. To extract systematics from the TG spectra, non-negative matrix factorization (NMF), an unsupervised machine learning technique, was applied to the DTG spectra of the experimental products. NMF revealed that the DTG profiles were explained by a linear combination of six basis spectra, which corresponded to the characteristic products, including three types of serpentine minerals (low-, medium-, and high-T), two types of brucite (low-and high-T), two type of talc (talc+serpentine mixture, well-crystallized talc) with different crystallinity, and noise during the TG measurement. Systematic changes in the factor loading revealed that, in the olivine-H<sub>2</sub>O systems, the products changed from medium-T serpentine+low-T brucite to high-T serpentine+high-T brucite as serpentinization progressed. In the olivine-orthopyroxene system, low-T serpentine or poorly crystallized talc+serpentine mixture was initially formed, followed by the formation of well-crystallized talc, resulting in dehydration. Applying NMF to DTG showed the mineralogical differences between olivine and orthopyroxene systems and increases of the crystallinity during the progress of serpentinization, suggesting its potential for characterizing various serpentinites within oceanic lithospheres that suffer from several stages of alteration and weathering at different temperatures.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140342991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Intermittent hydrothermal alteration and silicification of black mudstones found in the Middle to Upper Miocene Yagen Formation, Shimokita Peninsula, Northeast Japan 日本东北部下北半岛中上新世八根地层中发现的黑色泥岩的间歇热液蚀变和硅化作用
IF 1.5 4区 地球科学
Island Arc Pub Date : 2024-03-10 DOI: 10.1111/iar.12518
Hirokazu Ueda, Yoshikazu Sampei
{"title":"Intermittent hydrothermal alteration and silicification of black mudstones found in the Middle to Upper Miocene Yagen Formation, Shimokita Peninsula, Northeast Japan","authors":"Hirokazu Ueda,&nbsp;Yoshikazu Sampei","doi":"10.1111/iar.12518","DOIUrl":"https://doi.org/10.1111/iar.12518","url":null,"abstract":"<p>Organic geochemical processes in hydrothermal alteration system in terrestrial areas were investigated in the Shimofuro geothermal field, Northeast Japan. This study describes a continuous long mudstone outcrop of the Middle to Late Miocene Yagen Formation on the Shimokita Peninsula, Aomori Prefecture. The outcrop located near Mt.Hiuchi-dake shows sequential alteration with a color change from black to white. Contents of total organic carbon (TOC) vary from 0.00% to 0.46% according to litho-color change and become higher for black and lower for gray to white. TOC contents show a negative correlation with SiO<sub>2</sub> concentration. These indicate that TOC contents in the outcrop strongly depend on silicification caused by hydrothermal alteration. The mineral assemblages are composed of alunite, kaolinite, illite and pyrite, and indicate distinct alteration zones with acidic to neutral hydrothermal activities. Composition of the minerals formed by the alteration suggests that the temperature of hydrothermal fluid ranged from 150 to 250°C in a high-sulfidation hydrothermal system. Regarding the extracted hydrocarbons, particularly <i>n-</i>alkane distributions are significant. Values of Carbon Preference Index (CPI) increase up to 2.8 with increasing alteration and with decreasing TOC contents. This can be explained by two processes, (1) at the site of highly hydrothermal alteration, thermal cracking of organic matter in black mudstone strongly occurred and produced low-molecular gaseous hydrocarbons, and (2) at the site of inner rock with a distance from the hydrothermal alteration, thermal cracking moderately occurred and produced medium to long chain <i>n</i>-alkanes which were overlapped with original <i>n</i>-alkanes. Very low <i>T</i><sub>max</sub> values were found at the hydrothermal zone. This implies that natural extraction, migration, and precipitation of bituminous organic matter were driven by hydrothermal fluid.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140096575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Upper limb functional testing in athletes: A Delphi study. 运动员上肢功能测试:德尔菲研究。
IF 1 4区 地球科学
Island Arc Pub Date : 2024-03-01 Epub Date: 2022-05-23 DOI: 10.1177/17585732221101880
Camille Tooth, Cédric Schwartz, Cools Ann, Jean-Louis Croisier, Amandine Gofflot, Bornheim Stephen, Bénédicte Forthomme
{"title":"Upper limb functional testing in athletes: A Delphi study.","authors":"Camille Tooth, Cédric Schwartz, Cools Ann, Jean-Louis Croisier, Amandine Gofflot, Bornheim Stephen, Bénédicte Forthomme","doi":"10.1177/17585732221101880","DOIUrl":"10.1177/17585732221101880","url":null,"abstract":"<p><strong>Background: </strong>Functional testing has recently become more and more popular to assess athletes, both for injury prevention, as well as in an objective of performance. However, the relationship between the results of these tests and performances (or injuries) or their interpretation remains unclear.</p><p><strong>Objective: </strong>The aim of this study is to explore the usefulness, the characteristics, and the interpretation of the most frequently used upper-limb functional test.</p><p><strong>Methods: </strong>Twenty-two experts with an excellent knowledge of upper limb functional tests and an expertise in sports medicine and/or sports training of at least 5 years were recruited. They answered to qualitative and quantitative questions about functional testing trough structured questionnaires (online).</p><p><strong>Results: </strong>Four rounds were needed to reach a consensus about the usefulness as well as the characteristics of each test. Different sports-specific batteries of tests were also suggested by the experts and reached consensus. However, concerning the interpretation of the test, a consensus was only found for half of the tests considered.</p><p><strong>Conclusion: </strong>The current study summarizes the characteristics and the usefulness of the most popular upper-limb functional tests. However, the interpretation of some tests will have to be further explored since no consensus was found for them.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"13 1","pages":"89-99"},"PeriodicalIF":1.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10901172/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85303834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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