安徽铜陵矿集区中生代侵入岩体年代学研究及其成矿指示意义

Chronology study of the Mesozoic intrusive rocks in the Tongling ore-cluster region,Anhui,and its metallogenic significance

基于前人在铜陵矿集区获得的大量高精度同位素定年数据,本文补充测定了研究程度相对较低的棋子坑、瑶山、荷花塘等11个小型侵入体的LA-ICP-MS锆石U-Pb年龄,年龄分布在147～131 Ma之间。通过对区内成岩-成矿时代进行系统分析,提出了该区为一燕山期陆内"瞬时大规模成矿作用"形成的大型矿集区。区内燕山期成矿岩体主要包括花岗闪长岩类、石英(二长)闪长岩类和辉石(二长)闪长岩类等3类中酸性侵入岩,其成岩时代主要集中在152～130Ma之间,其中,花岗闪长岩集中在148～137 Ma、石英(二长)闪长岩在152～130 Ma、辉石(二长)闪长岩在150～134 Ma,区内主要矿床中获得的辉钼矿Re-Os成矿年龄分布在141～137Ma,成岩与成矿时代相差约10Ma以内,且成矿年龄具有自东向西逐渐变新的特征,区内相邻矿田成矿时代相差2Ma左右。铜陵矿集区在141～137 Ma的短时限内三次幕式大规模成矿作用为全球陆内岩浆成矿作用中所罕见。

Based on a large number of highly-precise dating data obtained for the Tongling district, this study carried out the supplementary LA-ICP-MS zircon U-Pb dating for 11 samples from small intrusive rocks in Qiziken, Yaoshan and Hehuatang, etc. which are poorly studied. The ages obtained in this study are distributed mainly between 147 Ma and 131 Ma. Systematic study of rock-and ore-forming ages suggests that this district is a large ore cluster area resulted from the Yanshanian intracontinental instantaneous large scale mineralization. The ore-forming intrusive rocks in the study area are mainly composed of granodiorite, quartz diorite(monzobiorite), and pyroxene diorite(monzobiorite), and rock-forming ages range from 148 Ma to 137 Ma, from 152 Ma to 130 Ma, and from 150 Ma to 134 Ma, respectively, with the rock-forming age mainly from 152 Ma to 130 Ma. The Re-Os isotopic ages of molybdenite from the important deposits in the Tongling area mainly range from 141 Ma to 137 Ma. The difference between the rock-and ore-forming ages was less than 10 Ma, and the difference of ore-forming ages of adjacent ore-field was less than 20 Ma, with ore-forming ages gradually becoming young from east to west. The three episodic large scale mineralization in the Tongling ore cluster area occurring within the short interval of ages(141~137 Ma) is rare in the global intracontinental magmatic mineralization.