Island Arc最新文献_第2页

Bringing the Submarine Mariana Arc and Backarc Basin to Life for Undergraduates and the Public 让本科生和公众了解马里亚纳海底弧和后弧盆地

IF 1 4区地球科学

Island Arc Pub Date : 2024-09-18 DOI: 10.1111/iar.12533

Robert J. Stern

{"title":"Bringing the Submarine Mariana Arc and Backarc Basin to Life for Undergraduates and the Public","authors":"Robert J. Stern","doi":"10.1111/iar.12533","DOIUrl":"https://doi.org/10.1111/iar.12533","url":null,"abstract":"<div>\u0000 \u0000 This paper aims to better teach about submarine arc and backarc basin volcanic and hydrothermal activity using the ~1400 km long Mariana convergent margin as an example. Four US National Oceanographic and Atmospheric Administration (NOAA) expeditions (2004–2016) equipped with a remotely operated vehicle (ROV) have discovered and explored many of submarine volcanoes and associated hydrothermal fields and generated many short (~1 min long) videos about them. Some of these videos would be very useful for teaching about these processes if they were organized and context provided, which is done here. Eighteen short videos about nine sites generated by NOAA are presented and discussed here. These are organized into three categories: volcanic eruptions, magmatic degassing, and hydrothermal activity. Volcanic eruption videos include two about glassy pillow lavas erupted in 2013–2015 and a rare example of a submarine eruption. Four videos about magmatic degassing include an example of sulfur produced by disproportionation of magmatic sulfur dioxide associated with a submarine eruption, two rare examples of molten sulfur lakes, and liquid carbon dioxide venting. Four videos about hydrothermal activity are provided. Suggestions for how this material might be used in the classroom are also given.\u0000 </div>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12533","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142244959","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

Cretaceous Fore-Arc Basin and Its Provenance in Sakhalin, Far East Russia: U-Pb Ages of Detrital Zircons From the Yezo Group 俄罗斯远东萨哈林白垩纪前弧盆地及其成因：叶佐群碎屑锆石的 U-Pb 年龄

IF 1 4区地球科学

Island Arc Pub Date : 2024-09-17 DOI: 10.1111/iar.12534

Tomohiko Sato, Yukio Isozaki, Yukiyasu Tsutsumi, Yasunari Shigeta, Kazuto Kodama, Takashi Hasegawa

{"title":"Cretaceous Fore-Arc Basin and Its Provenance in Sakhalin, Far East Russia: U-Pb Ages of Detrital Zircons From the Yezo Group","authors":"Tomohiko Sato, Yukio Isozaki, Yukiyasu Tsutsumi, Yasunari Shigeta, Kazuto Kodama, Takashi Hasegawa","doi":"10.1111/iar.12534","DOIUrl":"https://doi.org/10.1111/iar.12534","url":null,"abstract":"<div>\u0000 \u0000 In order to reconstruct the pre-Japan Sea configuration of the Cretaceous arc-trench system, we measured U-Pb ages of detrital zircons in the five sandstone samples from the Yezo Group in Sakhalin using LA-ICP-MS. A sandstone sample from the lowermost horizon (Ai Formation) contains abundant Early Cretaceous (110–100 Ma) zircons with minor amounts of pre-Jurassic ones. Four sandstones from the uppermost (Krasnoyarka Formation) are enriched dominantly in Late Cretaceous (100–66 Ma) grains. The YC1σ ages of these samples are generally consistent with the previous fossil ages; nonetheless, a possible age extension of the Ai Fm up possibly into the Cenomanian was newly suggested. The stepwise younging in peak age of zircons according to the stratigraphy suggests the continuous replacement of arc granitoid exposures in the Cretaceous magmatic arc in the provenance likely developed on the continent side. This secular trend in zircon age spectra of the Yezo Group in Sakhalin is properly correlated with that in Hokkaido and also with that of coeval sandstones in southwest Japan, suggesting a monotonous sedimentation in the fore-arc basin of the Late Cretaceous arc-trench system developed along the Pacific margin, from Sakhalin to southwest Japan for ca. 2500 km in length. Its spatial dimension corresponds to that of the modern representative fore-arc basin in the Java-Sumatra region.\u0000 </div>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142244968","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

Geochemical signatures of metapelites in the Highland Complex, Sri Lanka and Trivandrum Block, India: Implications for provenance, nature and tectonic setting of their source protoliths 斯里兰卡高地复合体和印度特里凡得琅区块元青石的地球化学特征：对其来源原岩的出处、性质和构造环境的影响

IF 1 4区地球科学

Island Arc Pub Date : 2024-07-31 DOI: 10.1111/iar.12529

A. M. M. G. I. U. B. Athauda, P. L. Dharmapriya, S. P. K. Malaviarachchi, K. Sajeev

{"title":"Geochemical signatures of metapelites in the Highland Complex, Sri Lanka and Trivandrum Block, India: Implications for provenance, nature and tectonic setting of their source protoliths","authors":"A. M. M. G. I. U. B. Athauda, P. L. Dharmapriya, S. P. K. Malaviarachchi, K. Sajeev","doi":"10.1111/iar.12529","DOIUrl":"10.1111/iar.12529","url":null,"abstract":"The investigation of whole-rock major and trace element geochemical data from metapelites, incorporating analyses from both previous studies and new localities within the Highland Complex (HC) of Sri Lanka and the Trivandrum Block of India (TB), aimed to discern the nature and tectonic setting of their provenance. Examination of chondritic REE distribution and K versus K/Rb diagrams suggests that the geochemistry of the studied metapelites closely resembles typical Post Archaean Australian Shale (PAAS), North American Shale Composite (NASC), and Upper Continental Crust (UCC), indicating minimal modification during high-grade metamorphism. Predominantly, the protoliths of the metasediments appear to be shales and greywackes derived from Proterozoic felsic to intermediate sources. Tectonic discrimination diagrams reveal that most metapelites correspond to active continental margins and continental island arcs. These geochemical characteristics suggest that the majority of studied metapelites in the HC and TB originate from felsic to intermediate sources, likely deposited within a continental arc setting. Subsequently, these sediments likely accreted in an accretionary prism and underwent metamorphism during continental-continental collision. The congruence in geochemical signatures between metapelites in the HC and TB, along with established tectonic, geochronological, petrological, mineralogical, and geophysical correlations, implies that precursor sediments of metasedimentary rocks were likely deposited within a laterally extensive Neoproterozoic sedimentary basin.","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882510","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

Estimating the amount of uplift from the current elevation of strata at the Middle Miocene Climatic Optimum: A case study of Kibi Plateau in Southwest Japan 根据中新世气候最适宜期地层的当前高程估算隆升量：日本西南部木部高原案例研究

IF 1 4区地球科学

Island Arc Pub Date : 2024-07-22 DOI: 10.1111/iar.12531

Yo-ichiro Otofuji

{"title":"Estimating the amount of uplift from the current elevation of strata at the Middle Miocene Climatic Optimum: A case study of Kibi Plateau in Southwest Japan","authors":"Yo-ichiro Otofuji","doi":"10.1111/iar.12531","DOIUrl":"10.1111/iar.12531","url":null,"abstract":"The Middle Miocene Climatic Optimum (MMCO) formed shallow marine strata on continents and island arcs at ~15 Ma, and some of the MMCO strata later experienced uplift. The amount of uplift corresponded to sea level rise after the MMCO period, but ancient sea level could not be observed. This study uses a deductive approach to estimate the amount of uplift. The elevation of the youngest marine sedimentary layer of the MMCO strata approximates the sea level at the MMCO. The current elevation was reconstructed by adding the amount of denudation from the MMCO to the current elevation of the denuded MMCO strata at the outcrops, considering isostatic compensation. The amount of denudation since the MMCO period was estimated to be 180 m based on the global average denudation rate (Willenbring et al., 2013), and the estimated isostatic rebound was 153 m. By comparing the current, albeit virtual, elevation of the youngest marine sedimentary layer in the MMCO strata with sea level at the MMCO, the amount of uplift was estimated. For the MMCO sea level, a 66 m ice-free line was adopted. This method was applied to the Kibi Plateau in Southwest Japan, where the MMCO strata are distributed. The reliability of the denudation amount of 180 m for the MMCO strata was confirmed by paleo-water depths estimated using benthic foraminifera and mollusk fossils. The largest uplift of 504 ± 27 m occurred at the Jinseki-Kogen since 15 Ma. A positive correlation was observed between the amount of uplift and the current altitude of the Kibi Plateau. The Kibi Plateau's topography most likely evolved after the MMCO. It is concluded that a new perspective on estimating the uplift was obtained by taking denudation into account.","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141777071","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

Subduction of the Paleo Pacific Plate at the southeast edge of the South China Block during the Early to Middle Jurassic: Sedimentary records from Fujian Province 侏罗纪早、中期华南地块东南边缘古太平洋板块的俯冲作用：福建省的沉积记录

IF 1 4区地球科学

Island Arc Pub Date : 2024-07-08 DOI: 10.1111/iar.12530

Long Leng, Zhongjie Xu, Kunning Cui, Shiyao Gao, Ningchen Sun

{"title":"Subduction of the Paleo Pacific Plate at the southeast edge of the South China Block during the Early to Middle Jurassic: Sedimentary records from Fujian Province","authors":"Long Leng, Zhongjie Xu, Kunning Cui, Shiyao Gao, Ningchen Sun","doi":"10.1111/iar.12530","DOIUrl":"https://doi.org/10.1111/iar.12530","url":null,"abstract":"During the Mesozoic, the tectonic evolution of the southeastern margin of the South China Block was mainly influenced by the subduction of the Palaeo-Pacific Plate. The sedimentary basins along the southeastern margin of the South China Block have preserved the sedimentary record of this process. In this paper, the sedimentary rocks of the Lishan Formation and Zhangping Formation in the Zhangping area of the southeastern margin of the South China Block are studied in terms of sedimentology, petrography, lithogeochemistry, U–Pb chronology of detrital zircon, and zircon trace elements. The study shows that the detrital zircon U–Pb age of the Lishan Formation is 2965–202 Ma, with two major age groups: 253–220 Ma and 1925–1799 Ma; the detrital zircon U–Pb age of the Zhangping Formation is 2587–190 Ma, with two major age groups: 246–234 Ma and 1929–1861 Ma; the ancient sediments in the samples are affected by recycle, and the Early Jurassic source area in the study area is an acidic magma zone, while the Middle Jurassic source area is located in a moderately acidic magma zone and recycle body; the Early Jurassic Lishan Formation and Middle Jurassic Zhangping Formation are mainly derived from the Wuyi Massif. In the upper section of the Lishan Formation, the secondary age groups of ca.448 and ca.773 Ma occur, and the detrital zircons in this section are mainly from the Jiangnan orogenic belt. The ongoing subduction of the Paleo-Pacific Plate led to the formation of diverse back-arc basins within the region; during the Early Jurassic, it was a back-arc compressional basin, transitioning into a back-arc extensional basin during the Middle Jurassic.","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141584005","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

Significance of serpentinite-hosted exhumation channels in a palaeo-subduction complex, Nishisonogi unit, Nagasaki Metamorphic Complex: P–T trajectories of mélange blocks and coherent schists 长崎变质岩群西野木单元古俯冲复合体中蛇纹石寄生掘进通道的意义：混杂岩块和相干片岩的P-T轨迹

IF 1.5 4区地球科学

Island Arc Pub Date : 2024-06-19 DOI: 10.1111/iar.12527

Tadao Nishiyama, Yosuke Moribe, Yasushi Mori, Miki Shigeno

{"title":"Significance of serpentinite-hosted exhumation channels in a palaeo-subduction complex, Nishisonogi unit, Nagasaki Metamorphic Complex: P–T trajectories of mélange blocks and coherent schists","authors":"Tadao Nishiyama, Yosuke Moribe, Yasushi Mori, Miki Shigeno","doi":"10.1111/iar.12527","DOIUrl":"https://doi.org/10.1111/iar.12527","url":null,"abstract":"Serpentinite mélanges occur as thin horizons up to 350 m thick within coherent schists of the Nishisonogi unit of the Nagasaki Metamorphic Complex located in western Kyushu, which represent serpentinite-hosted exhumation channels within a Cretaceous subduction complex. This study gives the petrography of coherent schists and various tectonic block types embedded in serpentinite or chlorite-actinolite schist of the mélange. The P–T conditions recorded in these rocks were compared, to clarify a possible exhumation process and style of the Nishisonogi unit. In the mélange, two types of tectonic blocks were recognized based on peak temperature conditions: a lower temperature type (400–590°C) and a higher temperature type (780–830°C), the latter of which shows temperatures higher than those of the coherent schists (370–450°C). The garnet glaucophanite in the coherent schists shows a prograde pressure increment from 0.9 to 2.3 GPa. The serpentinite mélange comprises tectonic blocks with peak temperatures higher than those of the coherent schists, indicating that blocks from the deep structural levels of the lower-plate underwent tectonic mixing into the mélange during exhumation. Ultrahigh-pressure (UHP) conditions have not been recorded either in the coherent schists or in the serpentinite mélanges, although microdiamonds have been reported from the Yukinoura mélange located at the western margin of the Nishisonogi unit (Nishiyama et al., Scientific Reports, 2020, 10, 11645). A possible correlation between the Nishisonogi unit and other HP metamorphic rocks or belts (Renge rocks, Suo Belt and Sanbagawa Belt) was examined to conclude that the Nishisonogi unit is a unique paleo-subduction complex in terms of the coexistence of HP subduction complex with intercalated serpentinite mélanges and a UHP mélange derived from the slab-mantle interface.","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"33 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141430316","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

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, Atsushi Yamaji, Naoto Ishikawa","doi":"10.1111/iar.12528","DOIUrl":"https://doi.org/10.1111/iar.12528","url":null,"abstract":"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.","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, Zhenyi Wang, Jin Zhang, Jianfeng Liu, Beihang Zhang, Rongguo Zheng, Jun Ma, Jie Hui, Heng Zhao","doi":"10.1111/iar.12525","DOIUrl":"https://doi.org/10.1111/iar.12525","url":null,"abstract":"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 εNd(t) (from −2.3 to −1.2), relatively high ISr (0.704772–0.708037) and depleted mantle model ages TDM (1.14–1.49 Ga), combining with weak negative to slightly positive εHf(t) (from −2.0 to +4.1) and crustal model ages TDMC (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 εHf(t) values. This might relate to the closure of the Yagan branch ocean of the PAO in northern Alxa.","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, Hironori Kato","doi":"10.1111/iar.12524","DOIUrl":"https://doi.org/10.1111/iar.12524","url":null,"abstract":"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.","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":"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.","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}

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