今天是2018年12月11日

琼东南晚二叠世I型花岗岩成因及其构造指示

DOI:10.3799/dqkx.2018.723

作者:赵国锋,刘汇川,钱鑫,张爱梅,何景文,何慧莹,王岳军

联系地址:广东省地球动力作用与地质灾害重点实验室,中山大学地球科学与工程学院,广东广州 510275

摘要:海南岛地处东古特提斯构造域东缘,是研究古特提斯东缘演化的重要地区.对海南岛东南部长征和陵水花岗闪长岩的LA-ICP-MS锆石U-Pb定年结果显示两者的结晶年龄分别为251±2 Ma和256±1 Ma,指示其形成于晚二叠世.样品的K2O/Na2O比值较低(0.2~0.9),铝饱和指数(A/CNK)为0.74~0.96,FeOT/MgO约为0.90,CIPW计算结果中标准矿物刚玉分子含量0.00~0.18%,小于1%,岩石薄片镜下可见大量角闪石,而未见白云母、堇青石和石榴子石,并具有相对负的ε Nd( t )值(-6.0~-3.2)和锆石原位ε Hf( t )值(-4.4~+0.2),属于准铝质钙碱性I型花岗岩.长征和陵水花岗闪长岩源岩为亚碱性变基性岩,其形成与金沙江-哀牢山-松马-邦溪-晨星古特提斯弧后盆地的闭合有关.

关键字:海南岛;古特提斯演化;I型花岗岩;晚二叠世;印支运动;岩石学

Petrogenesis of Late Permian I-Type Granites in SE Hainan Island and Its Tectonic Implication for Paleotethyan Evolution

Author:Zhao Guofeng, Liu Huichuan, Qian Xin, Zhang Aimei, He Jingwen, He Huiying, Wang Yuejun

Author Address:Guangdong Provincial Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China

Abstract:Hainan Island is located in the convergence zone of the Pacific and Tethys tectonic domains and is a key area for investigating the Pacific and Tethyan evolution of the Indochina and South China blocks. In this paper, a set of new zircon U-Pb and Lu-Hf isotopic data, along with whole-rock elemental and Sr-Nd isotopic analytical results for the Changzheng and Lingshui granitoid plutons in Southeast Hainan Island are presented. The Changzheng and Lingshui granodiorites yield Late Permian LA-ICP-MS zircon U-Pb ages of 251± 2 Ma and 256±1 Ma, respectively. They show K2O/Na2O=0.2-0.9, FeOT/MgO ratios of 0.90, A/CNK=0.74-0.96 with 0.00-0.18 vol.% corundum. Their ε Nd( t ) values range from -6.0 to -3.2 and in-situ zircon ε Hf( t ) values from -4.4 to +0.2. Such signatures, in combination with the absence of muscovite, cordierite and garnet, suggest that these Late Permian granodiorites are I-type granites. The Changzheng and Lingshui granites were derived from the subalkaline metabasites in response to the closure of the Jinshajiang-Ailaoshan-Songma-Bangxi-Chenxing branch/back-arc basin during Paleotethyan evolution.

Keyword:Hainan Island; Paleotethyan evolution; I-type granite; Late Permian; Indosinian orogeny; petrology

 

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作者简介:赵国锋(1992-),男,硕士研究生,主要从事岩石大地构造研究.ORCID: 0000-0002-5720-9310. E-mail: zhaogf@mail2.sysu.edu.cn

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