安徽省金寨县沙坪沟钼矿辉钼矿Re-Os年龄——兼论东秦岭-大别山中生代钼成矿作用期次划分

摘要

安徽省金寨县沙坪沟钼矿是新发现的超大型斑岩型钼矿床.文章介绍了该矿床的基本地质特征,并对其进行了精确的辉钼矿Re-Os同位素年代学测定.结果表明,沙坪沟钼矿辉钼矿模式年龄为(112.2±1.7)～(113.9±1.7) Ma,加权平均年龄为(113.18±0.54) Ma,MSWD - 0.39；等时线年龄为(113.21±0.53) Ma,MSWD=0.64,表明沙坪沟钼矿形成于早白垩世晚期.结合区域上已有的岩体高精度年代学数据、矿床辉钼矿Re-Os年代学数据和钼矿产出的大地构造位置,将东秦岭-大别山中生代钼成矿作用划分为2期4个阶段:印支期(260～205Ma)和燕山期的晚侏罗世—早白垩世早期(148～138Ma),早白垩世中期(135～119Ma)和早白垩世晚期(116～105Ma),其中,以燕山期钼成矿作用最为强烈.%The Shapinggou Mo deposit, located in Jinzhai Country of Anhui Province, is a giant ore deposit discovered in recent years in the Dabie Mountain. This paper describes geological characteristics of the ore deposit. The authors chose nine molybdenite-bearing samples for Re-Os isotopic dating, and the dating results show that the Re-Osmodel ages of the ore deposit are between (112.2 ± 1.7) Ma and (113.9 + 1.7)Ma, and the calculated isochron age is (113.21 ±0.53) Ma, suggesting that molybdenum mineralization occurred in the late period of early Cretaceous. High-precision chronologic data of regional intrusions, Re-Os dating data of molybdenites and geotectonic location of Mo deposits indicate that there occurred 2 epochs comprising 4 stages of Mo mineralization during the Mesozoic period in East Qinling-Dabie Mountain region. These Mo ore-forming stages include 205~260 Ma of Indosinian period, and 148-138 Ma, 135-119 Ma and 116~105 Ma of Yanshanian period. The Mo mineralization during the late Yanshanian period is the strongest one and is also the major ore-forming period of Mo polymetallic ore deposits in East Qinling-Dabie Mountain region.