湖南五峰仙岩体岩石地球化学、SHRIMP U-Pb年龄及Hf同位素特征

发布时间：2018-06-02 09:17

本文选题：湖南 + 五峰仙岩体　；参考：《地质科技情报》2017年06期

【摘要】：对湖南中生代的五峰仙岩体进行了锆石SHRIMP U-Pb定年和岩石学、岩石地球化学分析。该岩体主要由印支期的中粒斑状黑云母二长花岗岩、细粒二云母二长花岗岩组成。本次获得黑云母二长花岗岩的锆石U-Pb年龄(233.5±2.5)Ma,表明形成于晚三叠世;结合已发表的岩体年龄资料,五峰仙岩体侵位于236~233.5 Ma和221.6 Ma,具有多阶段岩浆活动特点。五峰仙花岗岩具有高的w(SiO2)、w(P2O5),含过铝质的白云母,表现为弱铝质、强铝质岩石;微量元素方面,大离子元素Rb、Th、U富集,Nb、Ba、Sr、Ti亏损明显,稀土元素配分模式右倾,轻稀土元素富集,Eu亏损相对明显以及高的Rb/Sr比值,为高成熟度陆壳物质重熔的S型花岗岩。黑云母花岗岩中发育暗色微粒包体,具淬冷结构、含长石捕获晶及呈塑形变等特征的包体为岩浆混合成因,该类花岗岩中锆石Hf同位素εHf(t)值较高,为-4.4~0.7,Hf同位素的两阶段模式年龄TDM2值为1 534~1 216Ma,变化范围较大,可能是受幔源岩浆作用所致。五峰仙岩体是在印支板块向华南板块俯冲碰撞期后(变质基底年龄258~243Ma)及华南板块与华北板块的碰撞期间(超高压变质峰期在238~218Ma)华南内陆由挤压向伸展转换的背景下形成的。
[Abstract]:Zircon SHRIMP U-Pb dating, petrology and petrogeochemical analysis of the Wufeng Xianshan rock mass during the Mesozoic in Hunan Province were carried out. The rock body is mainly composed of medium grain porphyritic biotite monzogranite and fine-grained dimica monzogranite in the Indosinian period. The zircon U-Pb age of biotite binomorphic granites was obtained at 233.5 卤2.5 Ma, indicating that it was formed in the late Triassic. According to the published age data, the Wufeng Xianshan intrusion was located at 236U 233.5 Ma and 221.6 Ma, which was characterized by multi-stage magmatic activity. The Wufengxian granite is characterized by a high level of W / SiO _ 2 / P _ 2O _ 5 and peraluminous Muscovite, which is characterized by weak aluminum and strong aluminous rocks, and in trace elements, the large ion element RbSU is enriched with significant depletion of NbSU, and the distribution pattern of rare earth elements is right tilted to the right. The enrichment of LREE is characterized by a relatively obvious depletion of EU and a high Rb/Sr ratio, which is a S-type granite with high maturity and remelting of continental crust material. In biotite granites, there are dark grained inclusions with quenched structure. The inclusions with feldspar capture crystal and plastic deformation are of magmatic mixing origin. The zircon HF isotopic 蔚 Hftt values of these granites are relatively high. The two-stage model age (TDM2) of -4.4 ~ 0.7H _ f isotope is 1 534 ~ 1 216 Ma, which may be caused by mantle-derived magmatism. The Wufeng Xianxian rock mass was formed after the collision period of the Indosinian plate subducting to the South China plate (the metamorphic basement age was 258- 243Ma) and the collision between the South China plate and the North China plate (the UHP metamorphic peak was 238U 218Ma).
【作者单位】：湖南省地质调查院;
【基金】：中国地质调查局项目“南岭成矿带中西段地质矿产调查”(121201009000150002);“湖南1∶5万铁丝塘、草市、冠市街、樟树脚幅区域地质矿产调查”(12120114024101)
【分类号】：P588.12;P59

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