湘东锡田钨锡多金属矿区成岩成矿时代的再厘定

Reconstraint from Zircon SHRIMP U-Pb Dating on the Age of Magma Intrusion and Mineralization in Xitian Tungsten-tin Polymetallic Orefield,Eastern Hunan Province

湘东锡田钨锡多金属矿床是地质大调查期间发现的一个大型矿床。矿体赋存在锡田复式花岗岩中及其与中泥盆统棋梓桥组的接触带上,主要矿床类型为矽卡岩型和破碎带蚀变岩型,其次为云英岩(或云英岩-石英脉)型。该复式花岗岩可划分为主体(中细粒斑状黑云母花岗岩)、补体(细粒含斑黑云母花岗岩)和晚期侵入体(细粒二云母花岗岩)。采用锆石SHRIMPU-Pb法,获得主体花岗岩的形成年龄为230.4±2.3Ma(MSWD=1.6)。本文通过对课题组及前人其它测年资料的对比分析,认为锡田复式花岗岩主体、补体和晚期侵入体分别属于印支期、燕山早期和燕山晚期;成矿作用与燕山早期花岗岩关系密切,是华南燕山早期大规模成岩成矿作用高峰期的产物。

Large -scale Xitian tungsten -tin polymetal deposit which is locating in eastern Hunan prov- ince was newly discovered in the national geological survey in recent years. Three types of ore - body are found in this deposit which are skam type, greisen -quartz vein type and fracture zone alteration rock type. Xitian granitic multiple intrusion dominately consist of medium - fine porphyritic biotite granite, with complementary fine biotite granite with much lesser phenocrysts and deuteric injections. In this paper, zircon SHRIMP U - Pb dating of dominated intrusion, yields an age of 230.4 ±2.3 Ma （ MSWD = 1.6）. Based on contrasting geochronology data from this program and precious works, it＇s indicated that the Xitian complex is intruded in indosinian, early yanshanian and late Yanshanian, respectively, and mineralization possibly closely relate to early Yanshanian intrusion, which therefore is product of enormous metallogenic magmatism explosion in early Yanshanian in south china.