Island Arc最新文献

{"title":"Age, geochemistry, mineralization, and tectonic significance of felsic-intermediate dikes in Shuangqishan Au deposit, Cathaysia block, South China","authors":"Feipeng Fan,&nbsp;Fan Xiao,&nbsp;Yan Zhou,&nbsp;Shizhong Chen","doi":"10.1111/iar.12482","DOIUrl":"10.1111/iar.12482","url":null,"abstract":"<p>The Shuangqishan Au deposit (&gt;15 t) is located in the Dehua-Youxi-Yongtai goldfield of the southeastern Cathaysia Block, South China. There are three stages of granites in the Shuangqishan Au deposit, the pre-mineralization granite porphyry formed in the Middle Jurassic (~166.0 ± 0.8 Ma), the metallogenic granite porphyry and monzonite porphyry formed in the late stage of the Late Jurassic (153–151 Ma), the post-mineralization granites (granite porphyry, the masanophyre, the dioritic porphyrite) formed in the Early Cretaceous (129.0–120.0 Ma). All rocks are characterized by high-K calc-alkaline and shoshonities series, the per-mineralization granites are enriched in Rb, Th, K, Zr, and Hf, depleted in Ba, P, and Ti, significant negative Eu anomaly and distinctly tetrad effect with highly fractionated I-type granitoids characteristics. The metallogenic granites and the post-mineralization granite porphyry are enriched in K, Rb, Th, Ce, Zr, Hf, and Y, enriched in LREE, strongly depleted in Sr, Ba Ta, P, Ti, have moderate negative Eu anomalies with I-type granites characteristics. However, the post-mineralization dioritic porphyrite displays strong depletions Sr, Ta, P, and Ti whereas Rb, Th, Ce, and Sm are enriched, enriched in LREE with weakly negative Eu anomalies. The metallogenic granite porphyry is significantly enriched in Au, As, Sb, W, Mo, and Bi, especially enriched in Au. The Lu-Hf isotopic data indicate that the magma source comes from the partial melting of the Paleoproterozoic crust, the minor part from the mantle in the Early Cretaceous. Therefore, we propose that the granitoids formed in the subducted plate environment from the Middle Jurassic to the Early Cretaceous, the Late Jurassic I-type granites (~153–146 Ma), The Shuangqishan Au deposit was formed in the stage from compression to extension, the Early Cretaceous granites (~129–114 Ma) mainly formed in the extensional environment and destroyed gold ore bodies.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43141702","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}

{"title":"Apatite U–Pb dating of dinosaur teeth from the Upper Cretaceous Nemegt Formation in the Gobi Desert, Mongolia: Contribution to depositional age constraints","authors":"Myu Tanabe,&nbsp;Kazumasa Aoki,&nbsp;Kentaro Chiba,&nbsp;Mototaka Saneyoshi,&nbsp;Shota Kodaira,&nbsp;Hirotsugu Nishido,&nbsp;Buuvei Mainbayar,&nbsp;Khishigjav Tsogtbaatar,&nbsp;Shinobu Ishigaki","doi":"10.1111/iar.12488","DOIUrl":"10.1111/iar.12488","url":null,"abstract":"<p>The Nemegt Formation in the Gobi Desert, Mongolia, hosts abundant dinosaur and other vertebrate remains, the ages of which are uncertain due to a lack of radioactive dating. In order to more strictly constrain the depositional age of Nemegt Formation, we conducted U–Pb isotope, trace elements, and Y-screening analyses using laser-ablation inductively-coupled plasma-mass spectrometry (LA-ICP-MS) on apatites of five <i>Tarbosaurus bataar</i> teeth collected from the middle Nemegt Formation. As a result, the age of 66.7 ± 2.5 Ma was obtained from one of the samples which is suggested to be least affected by secondary alteration of the U distribution, and this can be interpreted as a lower limit for fossilization of the tooth samples. Combined with the previously suggested relative age of the Nemegt Formation based on faunal occurrences, our data supports the deposition of the middle–upper Nemegt Formation during the Maastrichtian stage. Given that the depositional age of the Nemegt Formation has not been examined by isotope dating directly using fossils and minerals from the formation, this study is the first to report that the depositional ages of the vertebrate-bearing strata in the Gobi can be discussed by fossil apatite U–Pb dating in combination with the Y-screening method.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44992700","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}

{"title":"Chronological and geochemical characteristics of metavolcanic rocks in the Nanping-Ninghua tectonic belt: Constraints on the formation of the Cathaysia block","authors":"Huicheng Wen,&nbsp;Xilin Zhao,&nbsp;Guocan Wang,&nbsp;Huan Liu,&nbsp;Mincheng Xu,&nbsp;Yang Jiang","doi":"10.1111/iar.12486","DOIUrl":"10.1111/iar.12486","url":null,"abstract":"<p>The tectonic properties of the Nanping-Ninghua tectonic belt (NNTB) play a crucial role in understanding the tectonic evolution of the Wuyi orogenic belt, which is related to the Neoproterozoic-Paleozoic tectonic evolution of the Cathaysian Block. In this study, We present comprehensive petrological, geochronological, and geochemical data on the metavolcanic rocks from the Louqian Formation in Changting, Fujian Province. Our results show that volcanism in Changting occurred between 740.4 and 723.5 Ma, based on zircon U–Pb data for the metavolcanic rocks. The metavolcanic rocks have SiO₂ contents ranging from 68.22 to 71.56 wt %, high Al₂O₃ and Na₂O + K₂O contents (13.30–15.19 wt % and 7.56–8.25 wt %, respectively), and low CaO, MgO, and FeO_T contents (0.09–1.25 wt %, 0.72–0.96 wt %, and 1.57–3.16 wt %, respectively). These samples are enriched in large-ion lithophile elements (LILEs) such as Ba and Rb, and depleted in high-field-strength elements (HFSEs) including Nb, Ta, and Ti, with significant negative Eu anomalies, indicating an affinity for arc igneous rocks. Based on previous geological studies, we suggest that the NNTB formed in an active continental margin environment during the Nanhua Period. The subduction of oceanic crust led to the formation of the volcanic belt along the Nanping-Ninghua continental margin, which was active until 696 Ma. During the Neoproterozoic, the North and South Wuyi terranes did not merge to form a single Wuyi terrane, and the Cathaysia Block was composed of several terranes.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42196339","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}

{"title":"Elevated sedimentation of clastic matter in pelagic Panthalassa during the early Olenekian","authors":"Shun Muto,&nbsp;Satoshi Takahashi,&nbsp;Satoshi Yamakita","doi":"10.1111/iar.12485","DOIUrl":"10.1111/iar.12485","url":null,"abstract":"<p>The end-Permian mass extinction is thought to have greatly altered biogeochemical cycles. The absence of chert and dominance of claystone in low-latitude pelagic deep-sea sedimentary sequences of Early Triassic Panthalassa (the deep-sea chert gap) has been believed to record radiolarian die-off and consequent decline in biogenic silica production. However, recent studies showed that the upper portion of the deep-sea chert gap has sedimentation rates higher than bedded chert, meaning that increased clastic inputs, rather than decreased biogenic silica inputs, resulted in the anomalous lithology. In this study, we focus on the Akkamori-2 section, which preserves a rare sedimentary sequence spanning a large part of the lower portion of the claystone of the deep-sea chert gap. We obtained conodont fossils that allow correlation with sections in South China that have numerous dated tuffs. By projecting the dates of the tuffs to our measured sections, we show that sedimentation rates of the lower portion of the deep-sea chert gap is also higher than bedded chert. Hence, most of the deep-sea chert gap was formed under increased clastic inputs, which likely records disturbance in the terrestrial landscape, probably aridification and/or increased seasonality in arid areas, that lead to elevated dust flux to the pelagic ocean. On the other hand, the idea that the deep-sea chert gap records lingering effects of the mass extinction event on radiolarians cannot explain the high sedimentation rates of the deep-sea chert gap. This previously favored scenario needs to be reconsidered, taking into account the burial efficiency of biogenic silica in the Early Triassic ocean, and also effects of increased clay deposition on preservation of radiolarians.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42477966","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}

{"title":"Granite rock towers shaped by mesh-like joint sets, which formed in the shallower portion of a granite body during cooling at depth","authors":"Masahiro Chigira,&nbsp;Hironori Kato","doi":"10.1111/iar.12484","DOIUrl":"10.1111/iar.12484","url":null,"abstract":"<p>Granite is fractured according to the stress state during the cooling stage, providing predispositions for later topographic evolution. This study clarified that triangular mesh-like joints can be made during granite cooling and that they can become the structural causes for the formation of rock towers and corestones on the ground. Tengu rock, which consists of rock towers and granite corestones in Hiroshima, was investigated using an unmanned air vehicle. The rock towers were shaped by high-angle mesh-like joints, which were likely made during the cooling of the granite and are dominated by three joint sets. All the joint sets have sharp planar surfaces, which suggests that they are brittle fractures. One joint set is cut by the other two joint sets, frequently accompanies aplite and quartz veins and is developed in the whole exposed granite; this set likely formed first during cooling and then was penetrated by aplite from depth. The other two joint sets are high-angle conjugate joint sets, are limited to the shallower portion of the granite pluton and do not extend deeper, which strongly suggests that they formed in a rapidly cooled shallower portion of the pluton, probably near its roof. These three joint sets form rock columns with parallelogram cross-sections, in which incipient corestones were made. Subsurface weathering along the joints and subsequent exhumation of the weathering products formed the present rock towers and corestones only in the shallower portion of the granite.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12484","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47431194","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}

{"title":"Petrogenesis of mafic rocks from northwest Iran (Piranshahr) and comparison with northeast Iraq ophiolites: Implications for slab window magmatism in an evolving Neotethys arc","authors":"Maryam Yazdani,&nbsp;Mohssen Moazzen,&nbsp;Roland Oberhänsli","doi":"10.1111/iar.12481","DOIUrl":"10.1111/iar.12481","url":null,"abstract":"<p>The Piranshahr ophiolite is located in northwest Iran. The Mawat ophiolite in northeast Iraq is the western continuation of the Piranshahr ophiolite. The whole rock geochemistry of mafic rocks from the Piranshahr ophiolite (in the Gerdikavalan regions) is studied and compared with mafic rocks from the Mawat ophiolite in northeast Iraq (in the Hasanbag, Walash and Naopurdan regions). Two groups can be identified among the ophiolitic basalts in northwest Iran and northeast Iraq. The first one is represented by Late Cretaceous calc-alkaline basalts, displaying typical active continental margin signatures and thought to have been derived from the melting of enriched mantle sources modified by continental crust and subduction fluids. The second group is characterized by Eocene–Oligocene tholeiitic basalts, displaying signatures intermediate between mid-ocean ridge basalt (MORB) and oceanic island basalt (OIB) and back-arc basin (BAB) like magmas and suggested to have been derived from the melting of mixed asthenospheric-lithospheric mantle sources in a slab window. We propose that the subduction signature is acquired by interaction of the mantle advected through the slab window in the upper part of the subducting plate.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49649882","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}

{"title":"Early Paleozoic oceanic slab subduction in South China: Evidence from adakite-like granodiorite and high-Mg diorite from Puyang pluton in the Wuyi orogenic belt","authors":"Xiaodong Zhou,&nbsp;Tongchun Nie,&nbsp;Zhiding Han,&nbsp;Xilin Zhao","doi":"10.1111/iar.12483","DOIUrl":"10.1111/iar.12483","url":null,"abstract":"<p>The mechanism of Caledonian orogeny in South China is still controversial. The main argument focuses on the issue that whether there existed oceanic subduction. To answer this question, the complex Puyang pluton in the central part of Wuyi orogenic belt was selected for zircon U–Pb dating, in-situ Lu–Hf isotopic analysis and geochemical testing. The Puyang pluton is mainly composed of granodiorite and diorite. The results of geochronology indicate that the granodiorite and diorite emplaced at 450 ± 3.9 Ma and 443 ± 4.0 Ma. Their emplacement time were well corresponding to the subduction stage of the Yunkai orogeny in the southwestern part of Cathaysia block during the Early Paleozoic (460–440 Ma). The Puyang adakite-like granodiorite shows enrichments in Sr, but depletions in Y and Yb contents, high in Na₂O, K₂O and Al₂O₃, with <i>ε</i>_Hf(<i>t</i>) values range from −10.5 to −7.4 (mean of −9.0) and two-stage Hf model ages range from 1.91 to 2.10 Ga. These characteristics indicate that the magmas were generated by partial melting of subducted oceanic crust mixed with melts from the above wedgy mantle peridotite. The Puyang high-Mg diorite shows enrichments in Sr and Ba, depletions in Rb, Y and Yb contents, and strongly high in MgO and Al₂O₃ contents, with <i>ε</i>_Hf(<i>t</i>) values of −2.9 to 0 (mean of −1.4) and two-stage Hf model ages of 1.43 to 1.61 Ga. These indicate that the magmas were mainly generated by partial melting of the wedgy mantle peridotite, mixed by adakitic melts from subducted oceanic slab. Comprehensive analysis shows that Puyang adakite-like granodiorite and high-Mg diorite were formed in fore-arc setting, where the mantle and crustal magmas mixed during the oceanic subduction initiation period. By extension, this study offered important evidences to support the point that the Caledonian orogeny in South China was related to oceanic subduction which initiated prior to ~450 Ma.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41903621","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}

{"title":"Zircon geochronology of the deformed matrix in the NE Jiangxi ophiolitic mélange belt: Time constraints on the Neoproterozoic evolution of the Paleo–South China Ocean and assembly of the Yangtze and Cathaysia blocks","authors":"Zhu Qingbo,&nbsp;Wang Cunzhi,&nbsp;Zhao Xilin,&nbsp;Jin Guodong,&nbsp;Gao Tianshan","doi":"10.1111/iar.12480","DOIUrl":"10.1111/iar.12480","url":null,"abstract":"<p>The NE Jiangxi ophiolitic mélange belt is the key area for understanding the evolution of the Paleo-South China Ocean and the assembly of the Yangtze and Cathaysia blocks. The age of the deformed matrix is closer to the tectonic emplacement time of the ophiolitic mélange than that of the blocks. However, the rock types, ages and structural deformation of the matrix in the NE Jiangxi ophiolitic mélange belt lack comprehensive understanding. Based on the zircon U–Pb geochronology, Hf isotope and trace element analyses of the deformed matrix in the NE Jiangxi ophiolitic mélange belt, we report the ages of meta-rhyolite and tuffaceous phyllite to be 800–760 Ma, and the maximum depositional age of the clastic matrix is ~760 Ma. The youngest deformed matrix ages of 800–760 Ma constrain the tectonic emplacement age of the NE Jiangxi ophiolitic mélange belt to the late Qingbaikou period after 800–760 Ma and before the deposition of the Xiuning Formation (765–732 Ma). Zircon ages, trace element and Hf isotope compositions indicate that the 800–760 Ma matrix was formed in a back-arc basin environment with obvious addition of 1000–800 Ma arc materials and recycled Paleoproterozoic crustal materials. The detrital material source areas were the 800–760 Ma arc and earlier accretionary wedge as juvenile crust. The multi-stage arc magmatism, metamorphism and deformation in the NE Jiangxi ophiolitic mélange belt suggest that multi-stage subduction of the Paleo-South China Ocean and Neoproterozoic accretionary orogeny occurred during 1–0.76 Ga at the southeast margin of the Yangtze Block. Combined with the regional geological data, the Neoproterozoic back-arc basin or the foreland basin around the Yangtze Block closed after ~760 Ma. The collision and amalgamation of the Yangtze and Cathaysia blocks resulted in the final closure of the Paleo-South China Ocean, which have occurred in the early Paleozoic.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48565692","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}

{"title":"Correction to Middle Holocene relative sea-level changes and vertical tectonic crustal movements on Shikoku Island near the Nankai Trough, Japan","authors":"","doi":"10.1111/iar.12477","DOIUrl":"10.1111/iar.12477","url":null,"abstract":"<p> <span>Yamaguchi, T.</span>, <span>Nanayama, F.</span>, <span>Nakanishi, T.</span>, <span>Tsuji, T.</span>, <span>Ikeda, M.</span>, <span>Kondo, Y.</span>, <span>Miwa, M.</span>, &amp; <span>Hamada, Y.</span> (<span>2022</span>). <span>Middle Holocene relative sea-level changes and vertical tectonic crustal movements on Shikoku Island near the Nankai Trough, Japan</span>. <i>Island Arc</i>, <span>31</span>(<span>1</span>), e12452. https://doi.org/10.1111/iar.12452</p><p>On page 9, third paragraph, the Dryad Digital Repository link (https://datadryad.org/stash/share/Caof8eH1lrqg2vUUvuH20N71TqbLAOHBt4g5ydr8W2g) is outdated and inaccessible. The link has been updated and can be accessed on https://datadryad.org/stash/dataset/doi:10.5061%2Fdryad.pc866t1kk.</p><p>We apologize for this error.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12477","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44224653","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}

{"title":"Magnetic susceptibility, mineral chemistry, and geothermobarometry of granitoids from Lohit Plutonic Complex, Arunachal Trans-Himalaya, Northeast India: Implications on emplacement and crystallization conditions of oxidized calc alkaline magmatic arc system","authors":"Diezeneino Meyase,&nbsp;Vikoleno Rino,&nbsp;Santosh Kumar,&nbsp;Rokozono Nagi","doi":"10.1111/iar.12479","DOIUrl":"10.1111/iar.12479","url":null,"abstract":"<p>The Lohit Plutonic Complex (LPC) of Arunachal Trans-Himalaya represents the northeast extension of Trans-Himalayan magmatic arc system located in the north of Indus Tsangpo Suture Zone (ITSZ). Field relation, magnetic susceptibility (MS), and phase petrology on the granitoids of LPC was conducted in order to assess the granite series (magnetite, oxidized vs. ilmenite, reduced types), and physico-chemical conditions of the LPC granitoid magmas. The studied granitoids are well-exposed in the Dibang and Lohit valleys, and their MS values indicate a bi-modal patterns corresponding to ilmenite (reduced) series (71%) and magnetite (oxidized) series (29%) granites. The variation of MS in the LPC granitoids is related to the alteration of ferromagnetic minerals, and later tectonic and deformational processes that acted upon them. The amphiboles from the LPC granitoids are calcic (Ca_B &gt;1.5, Si = 6.30–7.06 apfu) and exhibit tschermak substitutions typical to their evolution in a calc alkaline, metaluminous (I-type) felsic magmas. Al-in-hornblende rims estimate the emplacement of quartz diorite and granodiorite magmas at shallow (~5 km) and mid (~16 km) crustal depths. Geothermometric results point to a regime of magmatic crystallization (940–837°C for quartz diorite; 882–829°C for granodiorite) sufficiently above the solidus of respective melts. Biotites from LPC granitoids are primary to re-equilibrated, and transitional between magnesio- and ferri-biotites. Quartz diorite and granodiorite biotites evolved under oxidizing magmas (log ƒO₂⁻¹⁴ to log ƒO₂⁻¹³) in a temperature range of ~750–950°C, typical to their formation in a calc alkaline magma of subduction zone environment. However, the biotites from leucogranite appear to have evolved under a mildly reducing magma environment, most likely attained in a collisional setting. The obtained results suggest that the oxidized nature of calc alkaline, subduction-related magmatic arc rocks of the LPC is largely modified and reduced by post-magmatic, and later tectonothermal and deformational events that operated during Himalayan and Trans-Himalayan orogenesis.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":"32 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43424727","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}