南秦岭龙王洞地区中生代云峰寨单元花岗岩地球化学特征及其地质意义

Geochemical Characteristics and Geological Significance of Granites in Yunfengzhai Unit of Mesozoic Era in Longwangdong Area of Southern Qinling Mountains

摘要:

该文对南秦岭龙王洞地区中生代云峰寨单元花岗岩的主量元素特征、微量元素特征及稀土元素特征进行分析研究，对该岩体进行较为全面的地球化学特征总结。研究表明：云峰寨单元花岗岩属于碱性过铝质A型花岗岩，形成于高温、贫水、高压的相对还原环境。花岗岩成因以地壳作用为主，花岗岩中稀土元素总体富集且分馏程度较高，轻稀土元素较重稀土元素富集且分馏明显。花岗岩为主动就位机制，是在早燕山期造山垮塌阶段的张性构造环境时期产生，与陆壳增厚、地幔物质减压隆升密切相关。

Abstract:

Characteristics of main elements, microelement and rare earth elements of Yunfengzhai unit granite of Mesozoic era in Longwangdong area of southern Qinling Mountains have been studied, and geochemical characteristics have been summarized. It is showed that granites of Yunfengzhai unit belong to alkaline peraluminous A type. It is formed in relative reduction environment with high temperature, poor water and high pressure. Crustal action is principle in the origin of granite magma. The rare earth elements in granites are enriched and the degree of fractionation is high. Light rare earth elements are enriched and fractionated more obviously than heavy rare earth elements. The granites formed during the period of orogenic collapse in early Yanshan stage is active emplacement mechanism. It is closely related to the thickening of continental crust and decompression uplift of mantle materials.