Recognition of Early Paleozoic Magmatisms in the Supposed Proterozoic Basements of Zhalantun, Great Xing’an Range, NE China

查看全文 作　　者：QIN [1,2]Tao;GUO [3]Rongrong;ZANG [2]Yanqing;QIAN [2]Cheng;WANG [2]Yan;SI [2]Qiuliang;SUN [2]Wei;MA [2]Yongfei

机构地区：[1]College of Earth Sciences,Jilin University,Changchun 130061,China;[2]Shenyang Institute of Geology and Mineral Resources,Shenyang 110034,Liaoning,China;[3]Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,Department of Geology,Northeastern University,Shenyang 110819,China

出　　处：《Acta Geologica Sinica(English Edition)》索引2019年第93卷第5期,共22页

基　　金：financially supported by China Geological Survey Project (Grant Number: DD20190039-01, DD20160048-01);the Fundamental Research Funds for the Central Universities (Grant Number: N160104003) 摘　　要：The Zhalantun terrane from the Xing’an massif, northeast China, was used to be considered as Proterozoic basements. However, amounts of detrital zircon ages from the meta-sedimentary rocks deny the existence of Precambrian basements recently. Notably, magmatic rocks were barely reported to limit the exact ages of the Zhalantun basements. In this study, we collected rhyolite, gabbro and quartz diorite for zircon in-situ U-Pb isotopic dating, which yield crystallization ages of ~505 Ma, ~447 Ma and ~125 Ma, respectively. Muscovite schist and siltstone define maximum depositional ages of ~499 Ma and ~489 Ma, respectively. Additionally, these dated supracrustal rocks and plutons also yield ancient detrital/xenocryst zircon ages of ~600-1000 Ma, ~1600-2220 Ma, ~2400 Ma, ~2600-2860 Ma. Based on the whole-rock major and trace element compositions, the ~505 Ma rhyolites display high SiO2 and alkaline contents, low Fe2O3T, TiO2 and Al2O3, and relatively high Mg O and Mg#, which exhibit calc-alkaline characteristics. These rhyolites yield fractionated REE patterns and negative Nb, Ta, Ti, Sr, P and Eu anomalies and positive Zr anomalies. The geochemistry, petrology and Lu-Hf isotopes imply that rhyolites were derived from the partial melting of continental basalt induced by upwelling of sub-arc mantle magmas, and then experienced fractional crystallization of plagioclase, which points to a continental arc regime. The ~447 Ma gabbros exhibit low Si O2 and alkaline contents, high Fe2 O3 T, Ti O2, Mg O and Mg#. They show minor depletions of La and Ce, flat MREE and HREE patterns, and negative Nb, Ta, Zr and Hf anomalies. Both sub-arc mantle and N-MORB-like mantle were involved in the formation of the gabbros, indicative of a probable back-arc basin tectonic setting. Given that, the previously believed Proterozoic supracrustal rocks and several plutons from the Zhalantun Precambrian basements were proved to be Paleozoic to Mesozoic rocks, among which these Paleozoic magmatic rocks were generally related to subduction regime. So far, none Proterozoic rocks have been identified from the Zhalantun Precambrian basement, though some ~600-3210 Ma ancient detrital/xenocryst zircons were reported. Combined with ancient zircon ages and newly reported ~2.5 Ga and ~1.8 Ga granites from the south of the Zhalantun, therefore, the Precambrian rocks probably once exposed in the Zhalantun while they were re-worked and consumed during later long tectonic evolutionary history, resulting in absence of Precambrian rocks in the Zhalantun. 关键词：early Paleozoic magmatism Xinghuadukou Group Jiageda Formation Zhalantun TERRANE GREAT Xing’an RANGE Central Asian OROGENIC Belt

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Recognition of Early Paleozoic Magmatisms in the Supposed Proterozoic Basements of Zhalantun, Great Xing’an Range, NE China

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