Early Mesozoic southward subduction history of the Mongol–Okhotsk oceanic plate: Evidence from geochronology and geochemistry of Early Mesozoic intrusive rocks in the Erguna Massif, NE China
Early Mesozoic southward subduction history of the Mongol–Okhotsk oceanic plate: Evidence from geochronology and geochemistry of Early Mesozoic intrusive rocks in the Erguna Massif, NE China
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蒙古—鄂霍茨克洋板块早中生代向南俯冲历史：来自额尔古纳地块早中生代侵入岩年代学和地球化学的证据
DOI：
10.1016/j.gr.2014.12.010
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发表时间：
2016-03
影响因子：
6.1
通讯作者：
Wang Wei
中科院分区：
文献类型：
--
作者：
Tang Jie;Xu Wenliang;Wang Feng;Zhao Shuo;Wang Wei
本文通过对额尔古纳地块早中生代侵入岩的锆石U-Pb年龄、Hf同位素和全岩常量、微量元素数据的研究，探讨了蒙古-鄂霍次克洋板块向南俯冲的历史及其对整个东北地区的影响。锆石U-Pb定年结果表明，额尔古纳地块早中生代岩浆活动可分为4个阶段，分别为~ 246 Ma、~ 225 Ma、~ 205 Ma和~ 185 Ma。~ 246 Ma侵入岩由一套高钾钙碱性闪长岩、石英闪长岩、花岗闪长岩、二长花岗岩和正长花岗岩组成，属I型。~ 225 Ma侵入岩由辉长闪长岩和花岗岩类组成，构成双峰式火成岩组合。~ 205 Ma侵入岩以钙碱性I型花岗岩为主，伴生中基性岩。~ 185 Ma侵入岩以I型花岗岩为主，少量A型花岗岩。这些早中生代花岗岩类主要起源于亏损和不均匀的下地壳的部分熔融，而同时代的镁铁质岩石可能来自于亏损地幔的部分熔融，俯冲相关的流体修改。岩石组合及其地球化学特征表明，~ 246 Ma、~ 205 Ma和~ 185 Ma侵入岩形成于与蒙古-鄂霍次克洋板块向南俯冲有关的活动大陆边缘环境。225 Ma双峰式火成岩组合形成于蒙古-鄂霍次克洋板块俯冲过程的间歇性伸展环境中。在蒙古-鄂霍次克缝合带的东南部，每一岩浆阶段都有其相应的斑岩矿床。综合上述研究结果，我们认为：（1）早中生代蒙古-鄂霍次克洋板块向南俯冲至额尔古纳地块之下，但在225 Ma左右出现了一次俯冲的停顿;（2）蒙古-鄂霍次克洋板块向南俯冲不仅引起了强烈的岩浆活动，而且有利于斑岩矿床的形成。
In this paper we present new zircon U–Pb ages, Hf isotope data, and whole-rock major and trace element data for Early Mesozoic intrusive rocks in the Erguna Massif of NE China, and we use these data to constrain the history of southward subduction of the Mongol–Okhotsk oceanic plate, and its influence on NE China as a whole. The zircon U–Pb dating indicates that Early Mesozoic magmatic activity in the Erguna Massif can be subdivided into four stages at ~ 246 Ma, ~ 225 Ma, ~ 205 Ma, and ~ 185 Ma. The ~ 246 Ma intrusive rocks comprise a suite of high-K calc-alkaline diorites, quartz diorites, granodiorites, monzogranites, and syenogranites, with I-type affinities. The ~ 225 Ma intrusive rocks consist of gabbro–diorites and granitoids, and they constitute a bimodal igneous association. The ~ 205 Ma intrusive rocks are dominated by calc-alkaline I-type granitoids that are accompanied by subordinate intermediate–mafic rocks. The ~ 185 Ma intrusive rocks are dominated by I-type granitoids, accompanied by minor amounts of A-types. These Early Mesozoic granitoids mainly originated by partial melting of a depleted and heterogeneous lower crust, whereas the coeval mafic rocks were probably derived from partial melting of a depleted mantle modified by subduction-related fluids. The rock associations and their geochemical features indicate that the ~ 246 Ma, ~ 205 Ma, and ~ 185 Ma intrusive rocks formed in an active continental margin setting related to the southward subduction of the Mongol–Okhotsk oceanic plate. The ~ 225 Ma bimodal igneous rock association formed within an extensional environment in a pause during the subduction process of the Mongol–Okhotsk oceanic plate. Every magmatic stage has its own corresponding set of porphyry deposits in the southeast of the Mongol–Okhotsk suture belt. Taking all this into account, we conclude the following: (1) during the Early Mesozoic, the Mongol–Okhotsk oceanic plate was subducted towards the south beneath the Erguna Massif, but with a pause in subduction at ~ 225 Ma; and (2) the southward subduction of the Mongol–Okhotsk oceanic plate not only caused the intense magmatic activity, but was also favorable to the formation of porphyry deposits.
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