赣南大埠复式花岗岩体两期成岩年龄及其地质意义

Two petrogenetic stages of Dabu composite granite pluton in South Jiangxi and their geological implications

大埠复式花岗岩体位于赣南腹地,是于都-赣县钨多金属矿集区的重要组成部分,其成岩期次及成岩成矿关系尚不十分清楚。文章采用LA-ICP-MS锆石U-Pb法测定了该岩体的成岩时代,结果表明:其东南体似斑状黑云母花岗岩年龄为(430.0±1.1)Ma,西北体斑状黑云母二长花岗岩年龄为(152.7±1.1)Ma。东南体虽对内外接触带铀矿的矿质来源有所贡献,但与西北体形成时代相差甚远,并非同一地质构造背景下的产物;西北体与内外接触带的钨矿床形成时代相近,成因联系密切。矿集区内岩浆活动具多旋回特征,以燕山早期尤其是158~153 Ma的花岗岩浆活动对钨多金属成矿作用最为有利。

The Dabu composite granitic pluton, located in the heartland of South Jiangxi Province, is an important part of the Yu-Ganxian W-polymetallic ore concentration area. It was dated in this paper by means of the Laser AblationMulticollector Inductively Coupled Plasma-Mass Spectrometry（ LA-ICP-MS） method, and the result shows that it has experienced two stages of magmatic activity. The emplacement of its southeastern unit（ porphyry-like biotite granite） and northwestern unit（ porphyry biotite granite monzogranite） occurred at（ 430. 0 ± 1. 1） Ma and（ 152. 7± 1. 1） Ma, respectively. The former was produced in the geological structural background different from its neighbouring uranium deposits, although it supplied them with a certain amount of mineral source. The latter formed in the same geological background as its endocontact and exocontact tungsten-polymetallic deposits, and is genetically associated with them. Three magmatic cycles have been recognized in Yudu-Ganxian area, with the granitic magmatism in the period of 158 ~ 153 Ma being the most favorable magmatism for tungsten-polymetallic mineralization.