TY - JOUR

T1 - Age, petrogenesis, and tectonic implications of the late Permian magmatic rocks in the Middle Gobi volcanoplutonic Belt, Mongolia

AU - Ganbat, Ariuntsetseg

AU - Tsujimori, Tatsuki

AU - Miao, Laicheng

AU - Safonova, Inna

AU - Pastor-Galán, Daniel

AU - Anaad, Chimedtseren

AU - Aoki, Shogo

AU - Aoki, Kazumasa

AU - Chimedsuren, Munkhnasan

N1 - Funding Information: This research was supported by CNEAS and FRIS of Tohoku University and in part by grants from the MEXT/JSPS KAKENHI JP18H01299 and JP21H01174 to Tatsuki Tsujimori and JP19K04043 to Kazumasa Aoki, by the National Natural Science Foundation of China (grant number 41772230) to Laicheng Miao, and by the Russian Science Foundation (project #21-77-20022; Nd isotope studies) to Inna Safonova. Ari Ganbat gratefully acknowledges the Japanese Government MEXT Scholarship. We also thank Isamu Morita and Otgon-bayar Dandar for their assistance in the laboratory and for providing geological material. Contribution to IGCP#662. Funding Information: Japan Society for the Promotion of Science, Grant/Award Numbers: JP18H01299, JP19K04043, JP21H01174; National Natural Science Foundation of China, Grant/Award Number: 41772230; Russian Science Foundation, Grant/Award Number: 21-77-20022 Publisher Copyright: © 2022 John Wiley & Sons Australia, Ltd.

PY - 2022/1/1

Y1 - 2022/1/1

N2 - 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 bio-tite-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 εNd (t) and zircon εHf (t) 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. Consid-ering 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 rela-tively simultaneous manner.

AB - 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 bio-tite-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 εNd (t) and zircon εHf (t) 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. Consid-ering 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 rela-tively simultaneous manner.

KW - CAOB

KW - Mongol–Okhotsk Belt

KW - peraluminous granite

KW - U–Pb geochronology

KW - Zircon Hf isotope

UR - http://www.scopus.com/inward/record.url?scp=85144133386&partnerID=8YFLogxK

U2 - 10.1111/iar.12457

DO - 10.1111/iar.12457

M3 - Article

AN - SCOPUS:85144133386

VL - 31

JO - Island Arc

JF - Island Arc

SN - 1038-4871

IS - 1

M1 - e12457

ER -