The lack of preserved basement results in uncertain placements of many terranes in Southeast Asia.Here,we flag the first evidence of the oldest basement in Indonesian Borneo,which can help locate terranes in Borneo on...The lack of preserved basement results in uncertain placements of many terranes in Southeast Asia.Here,we flag the first evidence of the oldest basement in Indonesian Borneo,which can help locate terranes in Borneo on the northern margin of Gondwana in the early Paleozoic and explain the regional tectonic setting of the island.Two schist samples from the Embuoi Complex in the Semitau Block,Northwest Kalimantan yielded zircon U-Pb dates of 453.3±1.9 Ma and 462.4±2.6 Ma,respectively,representing the formation time of the protolith.Petrographic,internal structural and high Th/U ratios of zircons indicate that the protolith of schists is of magmatic origin.The zircons haveεHf(t)values of−4.1 to+1.1 and Hf model ages of 1.37–1.69 Ga,indicating they were derived from a mixed source of juvenile crust with old components.By comparison of zircon age distribution,two-stage Hf model ages andεHf(t)variations of the early Paleozoic igneous rocks from Semitau with those of South China,Tengchong–Baoshan,and Indochina,the Semitau Block was most likely a part of or placed next to the Indochina Block of northern Gondwana during the early Paleozoic.Such a similar tectono-magmatic pattern on northern Gondwana formed a prolonged early Paleozoic arc-related belt associated with subduction of the Proto-Tethyan Ocean.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41802243,41772232 and 42161144007)the fund from the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources(Grant No.J1901-27)+1 种基金the Outlay Research Fund of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J2008)the China Geological Survey Program(Grant Nos.DD20190358,DD20221646 and DD20190001).This study is a contribution to International Geoscience Programme(IGCP)project 662“Orogenic architecture and crustal growth from accretion to collision.”We thank two anonymous reviewers for their helpful suggestions and constructive comments that helped us to improve this manuscript.
文摘The lack of preserved basement results in uncertain placements of many terranes in Southeast Asia.Here,we flag the first evidence of the oldest basement in Indonesian Borneo,which can help locate terranes in Borneo on the northern margin of Gondwana in the early Paleozoic and explain the regional tectonic setting of the island.Two schist samples from the Embuoi Complex in the Semitau Block,Northwest Kalimantan yielded zircon U-Pb dates of 453.3±1.9 Ma and 462.4±2.6 Ma,respectively,representing the formation time of the protolith.Petrographic,internal structural and high Th/U ratios of zircons indicate that the protolith of schists is of magmatic origin.The zircons haveεHf(t)values of−4.1 to+1.1 and Hf model ages of 1.37–1.69 Ga,indicating they were derived from a mixed source of juvenile crust with old components.By comparison of zircon age distribution,two-stage Hf model ages andεHf(t)variations of the early Paleozoic igneous rocks from Semitau with those of South China,Tengchong–Baoshan,and Indochina,the Semitau Block was most likely a part of or placed next to the Indochina Block of northern Gondwana during the early Paleozoic.Such a similar tectono-magmatic pattern on northern Gondwana formed a prolonged early Paleozoic arc-related belt associated with subduction of the Proto-Tethyan Ocean.
