Island Arc最新文献

{"title":"Zircon trace-element compositions in Miocene granitoids in Japan: Discrimination diagrams for zircons in M-, I-, S-, and A-type granites","authors":"Yusuke Sawaki,&nbsp;Hisashi Asanuma,&nbsp;Shuhei Sakata,&nbsp;Mariko Abe,&nbsp;Takeshi Ohno","doi":"10.1111/iar.12466","DOIUrl":"10.1111/iar.12466","url":null,"abstract":"<p>Detrital zircons demonstrate high resistance to alteration and, as such retain information about their formation ages and parental magmas for a long period of time. Geochemical researchers have proposed a wide variety of discrimination diagrams applicable to detrital zircons. In our research, we focused on the conventional classification scheme for granites (Mantle, M; Igneous, I; Sedimentary, S; and Alkaline, A types) and sought to characterize zircon trace-element compositions that are sensitive to differences among these granite types. To accomplish this, we examined trace-element compositions of zircons extracted from granitoids in the Ohmine granitic rocks and the Ashizuri plutonic complex in southwestern Japan. The zircons showed systematic differences in Nb/P, Ta/P, Ce/P, Ce/Nd, Y/P, Th/U, and Sc/Yb ratios and the Eu anomaly. Zircons in A-type granite are rich in Nb, Ta, Ce, and Y, and their signatures clearly reflect those elements in their parental bodies. Sc/Yb ratios of zircons in A-type granites are &lt;0.1, which is similar to those of ocean-island-type zircons. Despite their high abundance at the whole-rock level, zircons in S-type granite are characterized by low Nb/P, Ta/P, and Th/U ratios. This is attributable to the depletion of Nb, Ta, and Th in the magma by ilmenite and monazite prior to zircon crystallization. In general, S-type granitic magmas exhibit reducing environments, which decrease the proportions of Ce⁴⁺ and Eu³⁺. These effects lead to a low Ce/Nd ratio and a large negative Eu anomaly in S-type zircons. On the basis of these findings, we recommend the combined use of Nb/P–Ce/P or Ta/P–Ce/P crossplots and of Sc/Yb ratios to discriminate zircons in M-, I-, S-, and A-type granites. Although the crossplots are created using data from Miocene granitoids in Japan, the discrimination diagrams are based on the general features of each type of granite.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41450936","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":"The nature of the Moho beneath fast-spreading centers: Evidence from the Pacific plate and Oman ophiolite","authors":"Yoshihiko Tamura,&nbsp;Mathieu Rospabé,&nbsp;Gou Fujie,&nbsp;Akane Ohira,&nbsp;Kentaro Kaneda,&nbsp;Alexander R. L. Nichols,&nbsp;Georges Ceuleneer,&nbsp;Tomoki Sato,&nbsp;Shuichi Kodaira,&nbsp;Seiichi Miura,&nbsp;Eiichi Takazawa","doi":"10.1111/iar.12460","DOIUrl":"10.1111/iar.12460","url":null,"abstract":"<p>It is common knowledge that the Moho is the boundary between the crust and the Earth's mantle. Here we show along several seismic profiles through the Pacific Plate that a correlation exists between the strength of Moho reflections, crustal thickness, and water depth. Where the Moho can be detected clearly, the overlying oceanic crust is systematically thicker and the water depths are shallower. We suggest that two end-members of oceanic crust exist in fast spreading environments: one thick, underlain by a clear Moho; the other thinner, without a Moho; with all intermediate situations. In the Oman ophiolite, the best-preserved on-land analogue of fossil oceanic lithosphere created by fast-spreading, the boundary between the mantle peridotites and the lower crustal gabbros mainly consists of a dunitic transition zone (DTZ) ranging from a few meters to a few hundred meters in thickness. A sudden influx of seawater down to the base of the crust at the mid-ocean ridge (MOR) results in the hydrous (re-)melting of mantle peridotites, producing a dunitic residue at the crust–mantle boundary that represents the most reflective Moho. At the same time, the hydrous melting, in addition to the normal decompression melting, beneath the MOR, increases the thickness of the oceanic crust by enhancing magma production. In the absence of hydrous melting, the DTZ is thin or absent at the crust–mantle boundary, and instead the uppermost mantle harzburgite is intruded by gabbros, and/or the overlying crustal gabbro is intruded by numerous wehrlite bodies, which will be seismically gradational.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/iar.12460","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"62641163","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 two types of gabbro from Neoproterozoic Fuchuan ophiolite complex, Jiangnan Orogen: Implication for a Japan Sea-like back-arc basin","authors":"Wentao Hong,&nbsp;Minggang Yu,&nbsp;Zhentao Song,&nbsp;Pingli Chu,&nbsp;Kai Liu,&nbsp;Xiaohua Zhou","doi":"10.1111/iar.12465","DOIUrl":"10.1111/iar.12465","url":null,"abstract":"<p>The Neoproterozoic Fuchuan ophiolite complex (FCO) represents the lithospheric remnant of the back-arc basin in the southeastern margin of the Yangtze Craton. However, the nature and development of this back-arc system are still confusing. This study focuses on the tholeiitic gabbros in the FCO, which can be divided into enriched and depleted types according to their geochemical characteristics. Enriched gabbros (843 ± 5 Ma) in the FCO are characterized by left-sloping rare earth element (REE) patterns and relatively low ε_Hf(t) (mostly in the range of 4.6–7.8). In contrast, depleted gabbros are slightly younger (838 ± 5 Ma) and isotopically more depleted (ε_Hf(t) mostly in 7.7–11.8) than enriched gabbros, exhibiting flat REE patterns. Based on geochemical variations and numerical modeling, the primary magmas of enriched gabbros were generated by a low degree (~14 %) partial melting of the melt-modified depleted mantle. In contrast, the more depleted isotopic composition and variable Ba/Th and V/Yb ratios of depleted gabbros suggest that their magmas have originated from a higher degree (~14–26 %) partial melting of the fluid-modified residual depleted mantle. Considering that the most ~860–830 Ma magmatism in the eastern Jiangnan Orogen is calc-alkaline, the Neoproterozoic back-arc basin where the FCO formed could be sialic and built on the thinning continental crust, resembling the Japan Sea. The occurrences of tholeiitic gabbros in the FCO thus provide crucial insights into the opening of the back-arc basin in the southeastern margin of the Yangtze Craton. The changes of mantle source nature and metasomatic agent reflect the upwelling of the depleted asthenosphere and oceanward retreading of the continental arc during the back-arc opening. Consequently, the early continental arc in the southeastern Yangtze Craton may have been transformed into a new island arc, resembling the formation of the northeast Honshu arc during the Miocene.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46870717","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":"Overprint of secondary Du folding in the Sambagawa metamorphic belt, SW Japan: Implications for strain ellipsoids and Paleogene tectonics of the east-Eurasian margin","authors":"Mutsuki Aoya","doi":"10.1111/iar.12463","DOIUrl":"10.1111/iar.12463","url":null,"abstract":"<p>Two contrasting results of strain analyses, constriction and flattening, are recognized in the Sambagawa high-pressure/temperature metamorphic belt, SW Japan. An unverified proposal to account for this situation is that the constrictional strain ellipsoids develop only in areas where there is strong overprinting by a secondary Du-phase folding after a penetrative Ds-phase deformation. Field studies in the Hibihara district, central Shikoku, which is located between a southern constrictional region and a northern flattening region, reveal there is a map-scale contrast in the effect of Du: outcrop-scale Du upright folds are common in the southern region while they are rare in the northern region. Field measurements show that overall orientation of Ds strain is characterized by E–W stretching and vertical shortening, while that of Du strain is characterized by N–S shortening and vertical extension. The shortening caused by Du in the southern high-Du-strain regions estimated by the fold-curve tracing method are down to about 70%–56% and by removing this Du shortening most of the constrictional strain ellipsoids are restored back to the flattening field with only a few exceptions, suggesting that pre-Du strain states of the Sambagawa metamorphic rocks were dominantly of the flattening type. These results support the previous ideas that invoke differences in the strength of Du overprinting for the two different types of strain ellipsoids observed in the Sambagawa belt. From a tectonic point of view, the semi-penetrative occurrence of Du folds throughout the Sambagawa belt, which stretches about 800 km in SW Japan, suggests that the Du phase can be related to some ancient plate movement. The significant shortening subnormal to the orogen that characterizes Du may reflect a shift to orogen-subnormal subduction of the Pacific plate beneath the Eurasian plate at around 60 Ma.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43758351","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 U–Pb geochronology and geochemistry of the Late Jurassic granite porphyries from central-eastern Jilin Province, NE China: Petrogenesis and tectonic implications","authors":"Xiqing Ye,&nbsp;Zhitao Xu,&nbsp;Mengmeng Li,&nbsp;Liying Sun,&nbsp;Zhongwei Li,&nbsp;Donghan Yan,&nbsp;Jingqiao Feng","doi":"10.1111/iar.12464","DOIUrl":"10.1111/iar.12464","url":null,"abstract":"<p>The recently discovered Yizuoying Mo deposit is located in central-eastern Jilin Province, NE China. The molybdenum (Mo) mineralization, mainly hosted in granite porphyry, is considered to be granite-related. Zircon U–Pb dating of the granite porphyry yielded concordant ages of 160.81 ± 0.62 Ma, which is consistent with the weighted mean U–Pb age of 160.53 ± 0.65 Ma, indicating that the emplacement of granitic plutons occurred in the Late Jurassic. The granite porphyry samples are peraluminous, high-K calc-alkaline and show an A-type geochemical signature with high Na₂O + K₂O and Zr + Nb + Ce + Y content, K₂O/MgO, Fe₂O₃^T/(Fe₂O₃^T + MgO), REEs (rare earth elements) and 10 000 Ga/Al ratios. Based on the trace element content of zircons, they have high Th, U, Zr, Hf, and Pb abundance and obvious La and Eu anomalies, and their distribution pattern is similar to that of A-type granites. The zircon εHf(<i>t</i>) values range from 4.5 to 10.5 with Neoproterozoic <i>T</i>_DM2 ages (536–922 Ma) for Hf isotopes, and they have relatively high values of εNd(<i>t</i>) (3.14 to 3.49; <i>T</i>_DM2 = 665–693 Ma) and initial ⁸⁷Sr/⁸⁶Sr (0.723260–0.734669). Detailed elemental and isotopic data suggest that the Yizuoying granite porphyry belongs to the A₂-subtype and was formed by partial melting of a crustal source with a neoproterozoic overall residence age. Integrating new data on the oxygen fugacity of zircons and published data on the tectonic evolution, we suggest that the granite porphyry and associated Mo mineralization in the Yizuoying deposit formed in an extensional environment at ~160 Ma, related to the subduction of the Paleo-Pacific plate. The evolution of granitic magma in this period contributed to Mo mineralization.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45479695","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":"Solidification pressures and ages recorded in mafic microgranular enclaves and their host granite: An example of the world's youngest Kurobegawa granite","authors":"Kota Suzuki,&nbsp;Tetsuo Kawakami,&nbsp;Shigeru Sueoka,&nbsp;Ayu Yamazaki,&nbsp;Saya Kagami,&nbsp;Tatsunori Yokoyama,&nbsp;Takahiro Tagami","doi":"10.1111/iar.12462","DOIUrl":"10.1111/iar.12462","url":null,"abstract":"<p>Solidification pressures and ages of mafic microgranular enclaves (MMEs) and their host granite were determined and compared based on Al-in-hornblende geobarometry and U–Pb zircon dating in two sample localities in the Kurobegawa Granite. In sample KRG19-A03 from the middle unit of the pluton, the MME and the host granite yielded 0.18 ± 0.03 to 0.24 ± 0.04 GPa and 0.16 ± 0.03 to 0.23 ± 0.04 GPa, respectively. The MME and the host granite of sample KRG19-B08b from the lower unit, respectively, yielded 0.12 ± 0.02 to 0.21 ± 0.03 GPa and 0.13 ± 0.02 to 0.18 ± 0.03 GPa. In each sample locality, the estimated solidification pressures of the MME and its host granite overlap. The weighted mean ages were calculated as 0.775 ± 0.045 Ma and 0.831 ± 0.055 Ma for the MME and the host granite of KRG19-A03, respectively. The MME and the host granite of KRG19-B08b, respectively, yielded 0.672 ± 0.033 Ma and 0.735 ± 0.042 Ma. The ages for MMEs tend to be younger than the host granites, although they overlap within uncertainty. Zircon commonly occurs as the matrix minerals in both lithologies, meanwhile, zircon also occurs as early phases in plagioclase cores only in the host granites. Such differences in mode of occurrence of zircon suggest that the age variation reflects the differences in timing of zircon crystallization between the lithologies. Therefore, the MMEs record the same solidification pressures as the host granites and better represent the final solidification timing of the pluton. From these data of the MMEs, an average exhumation rate of each sample locality was estimated as 7.1–14.5 mm/year (KRG19-A03) and 5.5–14.4 mm/year (KRG19-B08b). These exhumation rates are much larger than that of the ca. 5.6–5.2 Ma Shiaidani Granodiorite (0.93–2.5 mm/year), implying that drastic change of the exhumation rate took place between ca. 5.2 Ma and ca. 0.83 Ma.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42082670","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":"Autogenic and allogenic controls on the temporal palaeographic evolution of the Himalayan foreland basin: Insights from facies analysis of the lower Siwalik succession, Kumaun Himalaya, India","authors":"Pradeep K. Goswami,&nbsp;Karuna Singh","doi":"10.1111/iar.12461","DOIUrl":"10.1111/iar.12461","url":null,"abstract":"<p>The lower Siwalik succession in the south-central Kumaun Himalaya records Middle Miocene fluvial sedimentation in the Himalayan foreland basin, the largest foreland basin of the world. Detailed facies analysis reveals three distinct facies associations, one of which is sand dominated channel deposits, and the other two are mudstone-sandstone, and mudstone dominated overbank deposits. The initial sedimentation in the region was in channels and frequently/extensively flooded overbank areas of a meandering/anastomosing river system. Activities along basement structures sometimes caused upheaval of the basin so that the streams got incised, and overbank areas rose up beyond the reach of flood waters. As a result, the fluvial sedimentation in these upland areas ceased, the sediments that had already deposited there were subjected to extensive pedogenesis, and occasionally reworked and redistributed by sheet flows and shallow channels. The channel pattern in the region gradually changed to braided type due to channel adjustments in response to rejuvenated tectonic activities and monsoon intensification in the hinterland. These factors caused increased influx of coarser sediments in the channels, which led to gradual steepening of the channel, and once the steepening crossed the threshold, the channel changed from meandering to braided type. Interpretation of our results is contrary to the general belief that Siwalik fluvial system changed from meandering streams to braided streams during the Middle Siwalik times, and the fluvial system in the studied part of the Siwalik basin underwent this change much earlier, during the sedimentation of Lower Siwalik.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44024482","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":"Origin and evolution of the Paleo-Kuril arc inferred from detrital zircon U–Pb chronology in eastern Hokkaido, NE Asia","authors":"Futoshi Nanayama,&nbsp;Toru Yamasaki,&nbsp;Toshiya Kanamatsu,&nbsp;Hideki Iwano,&nbsp;Tohru Danhara,&nbsp;Takafumi Hirata","doi":"10.1111/iar.12458","DOIUrl":"10.1111/iar.12458","url":null,"abstract":"<p>The Nemuro and Saroma Groups and Yusenkyo Formation occur in eastern Hokkaido and are considered to be forearc or intra-arc basin sediments of the Paleo-Kuril arc (PKA) deposited during the Late Cretaceous to middle Eocene. To further clarify the origin of the PKA, we examined the U–Pb ages of detrital zircons within these sandstones and acidic tuff beds; based on our results, we drew the following conclusions. (1) The PKA originated from an oceanic island arc on the oceanic Izanagi Plate around 85 Ma, to which the Nikoro Group greenstone complex was accreted between 81–80 Ma; the Lowest Unit of the Saroma Group covered the surface of the Nikoro accretional greenstone complex. (2) The PKA then first collided with NE Asia around the beginning of the deposition of the Hamanaka Formation (~70 Ma) and transitioned to a continental arc adjacent to NE Asia. This collision generated giant slump beds during deposition of the Akkeshi Formation. During deposition of the Kiritappu Formation, the entire Nemuro Peninsula was uplifted, supplying large volumes of clastic sediments. (3) Although we do not have data directly bearing on why the North American Plate was established in the edge of NE Asia, we speculate that it separated from the Eurasian continent around ~70 Ma when NE Asia first collided with the PKA. Subsequently, the PKA has behaved as part of the North American Plate. The Paleo-Japan arc (or East Sikhote–Alin arc) and the PKA became joined via the Hidaka Belt. Around 40 Ma, during the deposition of coarse conglomerate beds of the Urahoro Group, the PKA was uplifted and bent clockwise due to a second collision with NE Asia. (4) The modern Kuril arc was established around 36 Ma (late Eocene–early Oligocene), and the Kuril backarc basin opened into the present tectonic setting in the late Oligocene–early Miocene.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41767861","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":"Middle Devonian ostracods from the Naidaijin Formation, Kurosegawa belt, Kyushu, Japan: Paleoecological and paleogeographical significance","authors":"Gengo Tanaka","doi":"10.1111/iar.12459","DOIUrl":"10.1111/iar.12459","url":null,"abstract":"<p>This study reports five ostracod taxa from the Middle Devonian Naidaijin Formation, Kumamoto Prefecture, Kyushu, Japan comprising shelf-nearshore beyrichiid and bairdiocypridoid species, and two species of <i>Bairdia</i>. This is the first report of ostracod fossils from the Devonian strata in the Kurosegawa belt. Most analyzed fossils are the same species as those found in the Middle Devonian strata of Yunnan and Guangxi provinces in South China, indicating that the Kurosegawa belt of Kyushu shared biogeographical affinities with the palaeo-equatorial South China paleocontinent.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43398121","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":"Age, petrogenesis, and tectonic implications of the late Permian magmatic rocks in the Middle Gobi volcanoplutonic Belt, Mongolia","authors":"Ariuntsetseg Ganbat,&nbsp;Tatsuki Tsujimori,&nbsp;Laicheng Miao,&nbsp;Inna Safonova,&nbsp;Daniel Pastor-Galán,&nbsp;Chimedtseren Anaad,&nbsp;Shogo Aoki,&nbsp;Kazumasa Aoki,&nbsp;Munkhnasan Chimedsuren","doi":"10.1111/iar.12457","DOIUrl":"10.1111/iar.12457","url":null,"abstract":"<p>The Mongol–Okhotsk Belt, the youngest segment of Central Asian Orogenic Belt, was formed by the evolution and closure of the Mongol–Okhotsk Ocean. The oceanic closure formed two volcanoplutonic belts: Selenge Belt in the north and the Middle Gobi Belt in the south (in present day coordinates). However, the origin and tectonic evolution of the Mongol–Okhotsk Belt in general, and the origin and formation age of the Middle Gobi Belt in particular, remain enigmatic. To better understand the history of the magmatic activity in the Middle Gobi Belt, we conducted geochemical, U–Pb geochronological, zircon Hf, and whole-rock Nd isotopic analyses of samples from the Mandalgovi volcanoplutonic suite, the major component of the Middle Gobi Belt. Our results show that the plutonic rock consists of ~285 Ma gabbro, ~265 Ma biotite-granite and ~250 Ma hornblende-granodiorite. The volcanic counterpart is represented by a Permian Sahalyn gol rhyolite and ~247 Ma Ikh khad andesite. The geochemical compositions of biotite-granite and hornblende-granodiorite indicate that their precursors were metagraywacke and amphibolite, respectively. They are characterized by positive whole-rock ε_Nd(<i>t</i>) and zircon ε_Hf(<i>t</i>) values, indicating juvenile protoliths. The gabbro was derived by partial melting of a metasomatized lithospheric mantle source in a supra-subduction setting. The biotite-granite and Sahalyn gol rhyolite are formed by remelting of sediments in an inter-arc extension setting. Later the hornblende-granite and Ikh khad volcanic were emplaced at a volcanic arc formed by the subduction of the Mongol–Okhotsk Ocean. We conclude that the magmatic rocks of the Middle Gobi Belt formed in an active continental margin setting. Considering the consistent distribution of coeval arc-derived magmatic formations along the southern margin of the Mongol–Okhotsk Belt, the oceanic basin was closed in a relatively simultaneous manner.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45224460","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}