皖南地区谭山复式岩体的成因研究

谭山复式岩体位于江南过渡带北缘，是该区出露面积较大的复式岩体。本文对谭山复式岩体开展了地质调查、岩浆岩锆石U-Pb年代学和全岩地球化学分析。地质特征显示谭山复式岩体沿杨美桥背斜轴部侵入，根据岩性分析划分为碱长花岗岩、正长花岗岩和二长花岗岩。LA-ICP-MS锆石U-Pb定年结果显示，碱长花岗岩和正长花岗岩分别为128.9±1.6 Ma～128.8±2.5 Ma和129.8±2.6 Ma～129.2±1.8 Ma；结合前人已获得二长花岗岩成岩时代（128.5±1.7 Ma～126.7±1.7 Ma），谭山复式岩体形成于128.9±1.6 Ma～126.7±1.7 Ma之间，对应于皖南地区燕山期 3阶段岩浆活动（早阶段：153～146 Ma，中阶段：143～136 Ma，晚阶段：135～121 Ma）的最晚阶段（135～121 Ma）。该复式岩体碱长花岗岩、正长花岗岩和二长花岗岩的地球化学特征均表现为：富碱，高Ga/Al比值，强烈亏损Ba、Sr、P、Ti，富集 Rb、Th、Nd、Ce，显著的Eu负异常，均为碱性过铝质特征的A型花岗岩。谭山复式岩体起源于下地壳物质部分熔融，为陆内拉张环境背景下同源岩浆多期次上升侵位的产物。

Genesis of the Tanshan complex pluton in South Anhui district

The Tanshan complex pluton is located in the northern margin of Jiangnan transition belt,which is the large complex pluton in the district. In this study, the authors systematicallyinvestigate the geology, geochronology and geochemistry of Tanshan complex pluton. Thegeological characteristics show that Tanshan complex pluton intruded along the axis ofYangmeiqiao anticline, which can sub-divided into alkalifeldspar granite, syenogranite andmonzogranite from lithologically. The LA-ICP-MS U-Pb dating results of the alkalifeldspargranite and syenogranite intrusions are 128.9±1.6 Ma～128.8±2.5 Ma and 129.8±2.6 Ma～ 129.2±1.8 Ma respectively. Combined with the published age of the monzogranite intrusion （128.5±1.7 Ma～126.7±1.7 Ma）, the Tanshan complex pluton was intruded in between 128.9±1.6 Ma～126.7±1.7 Ma, which was corresponding to the last-stage magmatism of the 3 stageYanshannian granitoid activities（Early：153～146 Ma, Middle：143～136 Ma, and Late：135～121 Ma） in South Anhui district（135～121 Ma）. All the alkali feldspar granite,syenogranite and monzogranite samples from Tanshan complex pluton exhibit the similargeochemical characteristic with A-type granite, which including high Alkaline, Ga/Al enrichedratios, in Rb, Th, Nd, Ce, depleted in Ba, Sr, P and Ti, and distinctly negative Eu abnormality.The multistage magma formed the Tanshan complex pluton was consistently derived from thelower crust, in the intracontinental tension background.