Petrogenesis and Tectonic Setting of Volcanic Rocks of Dashizhai Formation in Dashizhai Area, Eastern Inner Mongolia

被引：1

作者：

Na F. ^{[1
]}

Song W. ^{[1
]}

Yang Y. ^{[1
]}

Fu J. ^{[1
]}

Wang Y. ^{[1
]}

Liu Y. ^{[1
]}

Sun W. ^{[1
]}

Qian C. ^{[1
]}

Qin T. ^{[1
]}

Ma Y. ^{[1
]}

Wu Y. ^{[1
]}

Zhong H. ^{[1
]}

机构：

[1] Shenyang Geological Survey Center, China Geological Survey, Shenyang

来源：

Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2021年 / 46卷 / 07期

关键词：

Dashizhai Formation; Eastern Inner Mongolia; Geochemistry; LA⁃ICP⁃MS U⁃Pb dating; Tectonic setting;

D O I：

10.3799/dqkx.2020.272

中图分类号：

学科分类号：

摘要：

The petrogenesis and geodynamic setting of Early Permian volcanic rocks in eastern Inner Mongolia, hold a key to understanding the amalgamation of Xing'an block and Songnen block. This study carry out LA⁃ICP⁃MS zircon U⁃Pb dating, whole rock major trace and zircon in situ Lu⁃Hf isotopic analysis of basic⁃intermediate volcanic rocks of Dashizhai formation in Dashizhai area with the aim of investigating their petrogenesis and unraveling the geodynamic setting of their emplacement, so as to provide more information for constraining the amalgamation process of Xing'an block and Songnen block, and for exploring the tectonic evolution of the eastern part of the Xing'an⁃Inner Mongolia Orogenic Belt (XMOB). The basic⁃intermediate volcanic rocks of Dashizhai Formation include metaspilite, metabasalt, clastic basaltic andesite, basaltic andesite, chloritized andesite, amygdaloid andesite, andesitic crystalline tuff, etc. LA⁃ICP⁃MS zircon U⁃Pb ages of 286.0±4.3 Ma (MSWD=0.14) and 286.0±3.3 Ma (MSWD=0.14) from the metaspilite and chloritized andesite uniformly indicate that these basic⁃intermediate rocks of Dashizhai Formation erupted in the Early Permian, representing a violent tectono⁃magmatism event. Geochemically, these volcanic rocks are a set of Na rich subalkaline basalt⁃basaltic andesite⁃ andesite association, most of them are dominated by tholeiitic series, and some of them have both tholeiitic and calc alkaline characteristics. These rocks are characterized by an enrichment in large ion lithophile elements (LILEs, such as Ba, U, K) and light rare earth elements ( LREE, La, Ce), and a depletion in high field strength elements (HFSEs, such as Nb and Ta). Most magmatic zircons of the metaspilite and chloritized andesite show positive εHf(t) values (6.68-12.94 and 8.41-12.31 resectively ) and similar single⁃stage model ages (TDM1=438-589 Ma and 413-668 Ma resectively ). In summary, the basic⁃intermediate volcanic rocks of Dashizhai Formation in Dashizhai area are derived from depleted mantle, and experienced fractional crystallization of clinopyroxene, olivine and iron magnesium oxide in the process of magma evolution, and suffered from strong crustal contamination.Combined with the regional geological data, the volcanic rocks of Dashizhai formation in Dashizhai area were formed in the tectonic setting of intracontinental extension rather than subduction background, which indicates that the amalgamation of Xing'an block and Songnen block occurred before the Early Permian. At the same time, by comparing the geochemical characteristics and other geological data of the Early⁃Middle Permian volcanic rocks in the region, this paper considers that the Early⁃Middle Permian volcanic rocks in the mid⁃eastern Inner Mongolia are the products of intracontinental extension, and the regional extension may have originated from the Early Carboniferous. © 2021, Editorial Department of Earth Science. All right reserved.

引用

页码：2403 / 2422

页数：19

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