江南造山带湖南段金矿成矿事件及其构造背景

江南造山带湖南段为一重要的金成矿带,目前关于带内金矿形成的时代背景存在较大争议.本文基于区域成岩成矿年代学、矿床(区)地质特征、矿床成因和流体来源、区域构造演化背景等多方面资料,对带内各主要金矿区的成矿时代逐一进行详细解析,以此为基础重新厘定了区域金矿成矿地质事件及其时代,并探讨了各成矿事件的构造背景,初步形成以下认识...

Gold mineralization events of the Jiangnan Orogen in Hunan and their tectonic settings

The Jiangnan Orogen in Hunan is an important gold metallogenic belt. There are debates about the gold ore-forming ages and geological settings of the belt. According to the ages of magmatic rocks and deposits, as well as geological charateristics of deposits, metallogeny and ore-forming fluids and regional tectonic evolutions, the authors analysed the metallogenic ages of every major ore concentration area in the Jiangnan Orogen in Hunan, and then defined the gold mineralization events and their ages, probed into the tectonic settings of the events. The following preliminary ideas are put forward. There occurred mainly three gold mineralization events in Jiangnan Orogen such as Caledonian, late Indosinian and Yanshanian. The Caledonian gold deposits with ore-forming age of 430~410 Ma (late Silurian) were located in the three areas, such as the middle-southwestern segment of Xuefeng thrust-fault zone, the eastern segment of Xuefeng thrust-fault zone, and northeastern Central-Southeastern Hunan tectonomagmatic belt in the same time, with ore-bearing strata Banxi Group, Lengjiaxi Group and Lengjiaxi Group respectively. Gold mineralization in the first two areas was related with metamorphism, deformations and structural activation caused by Caledonian Movement, while in the last area was related with the thermal energy and hydrotherm provided by late Silurian granitic magmatism. The late Indosinian gold deposits with ore-forming age of 227~202 Ma (Late Triassic) took place mainly in southeastern Xuefeng tectonomagmatic uplift zone in Indosinian, and were related with the thermal energy and hydrotherm caused by post-collisional granitic magmatism. The Yanshanian gold deposits with ore-forming age of 152~130 Ma (Late Jurassic-initial Early Cretaceous) were mainly took place in east part of southeastern Xuefeng tectonomagmatic uplift zone in the same time, and were related with the granitic magmatism in extensional environment.