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湘南王仙岭花岗岩体的特征及成因研究

The Characteristics and the Genesis of the Wangxianling Granitic Intrusive,South Hunan Province

【作者】 郑佳浩

【导师】 毛景文; 郭春丽;

【作者基本信息】 中国地质大学(北京) , 矿物学、岩石学、矿床学, 2012, 硕士

【摘要】 王仙岭花岗岩体位于湖南省郴州市东南约10km处,地处华南腹地的南岭钨锡多金属成矿区中段。本文在对前人资料和研究成果进行全面总结的基础上,对王仙岭岩体进行详细的野外地质调查,结合年代学、矿物学、岩石地球化学、同位素地球化学的研究,讨论了王仙岭岩体的形成时代和成岩期次、矿物学特征、岩浆的源区和演化特征。并对比了华南同时代相似花岗岩类,探讨了该时期花岗岩类的源区、构造背景和地球动力学演化过程。主要取得了以下认识:(1)王仙岭花岗岩体由印支期电气石黑云母花岗岩、云英岩化电气石花岗岩和侵入岩体内部的燕山期黑云母二长花岗岩株组成,其中电气石黑云母花岗岩和云英岩化电气石花岗岩为同期同源花岗岩。(2) LA-MC-ICP-MS锆石U-Pb测年结果显示王仙岭岩体主体的电气石黑云母花岗岩的形成时代为235.0±1.3Ma,而黑云母二长花岗岩株的年龄为155.9±1.0Ma,说明王仙岭岩体至少经历了两次岩浆活动,是一个印支-燕山期的复式岩体。(3)电气石黑云母花岗岩和黑云母二长花岗岩中的白云母主要为次生白云母,电气石黑云母花岗与云英岩化电气石花岗岩中电气石均属黑电气石。(4)印支期电气石黑云母花岗岩为强过铝质花岗岩,具S型花岗岩的特点,可能主要源自古中元古代地壳物质重熔,并在上升侵位过程中混染了部分继承锆石。燕山期黑云母二长花岗岩具有过铝质的特点,主要源于古中元古代地壳物质重熔。印支期电气石黑云母花岗岩和燕山期黑云母二长花岗岩形成过程中都经历了结晶分异作用。(5)燕山期花岗岩主要源于下地壳物质部分熔融,并有部分幔源物质参与;印支期花岗岩相对燕山期花岗岩有更多地幔物质的参与。(6)推测印支期电气石黑云母花岗岩形成于碰撞挤压作用间歇期岩石圈伸展的动力学背景下,而燕山期黑云母二长花岗岩形成于大陆边缘弧后伸展背景下。

【Abstract】 Located about10km at the southeast of Chenzhou City in Hunan Province,Wangxianling granite intrusion is in the middle of the Nanling tungsten-tinpolymetallic metallogenic area of South China Block. On the basis of field geologicalsurvey, combined with mineralogy, petrology, geochemistry and isotope research, thispaper discussed the age and diagenetic stages, the mineralogical characteristics,magma source and the evolution characteristics of Wangxianling granite intrusion.And by comparing the characteristics of contemporary similar granitoids in SouthChina, we discussed the source region, tectonic setting and geodynamic evolution ofthe same period granitoids in South China Block. Achieving the understanding asfollows:(1)The Wangxianling intrusion in south Hunan province consists of twogranitoids, the main intrusion body tourmaline biotite granites, greisenizationtourmaline granites and the interior stock biotite monzonite granites, in which theourmaline biotite granites and greisenization tourmaline granites are homologousgranites in the same period.(2)The LA-MC-ICP-MS zircon U-Pb dating shows that the tourmaline biotitegranites formed in the Indosinian (235.0±1.3Ma) while the biotite monzonite granitesformed in Yanshanian(155.9±1.0Ma), indicating that Wangxianling intrusion is theproduct of two times magmatic activities.(3) Both the muscovite in tourmaline biotite granites and biotite monzonitegranites are mainly secondary muscovite, and both the tourmaline in tourmalinebiotite granites and greisen tourmaline granites are schorl.(4) The Indosinian tourmaline biotite granites are strongly peraluminous graniteswith S-type granite characteristics and are originated from the Paleo-andMesoproterozoic crustal remelting while the Yanshanian biotite monzonite granitesare peraluminous granites and are originated from the Paleo-and Mesoproterozoiccrustal remelting. Both the Indosinian tourmaline biotite granites and Yanshanianbiotite monzonite granites have experienced fractional crystallization during theformation.(5) The Yanshanian granites are mainly derived from partial melting of lowercrustal material with some of the mantle materials involved while the Indosiniangranites involving more mantle materials than theYanshanian granites.(6)We infer that the Indosinian period granitic magma formed in intermittentlithosphere extensional environment during the collision compression while theYanshanian period granitic magma formed in the extensional environment of the backarc continental margin.

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