贵州普定五指山地区铅锌矿床成矿模式

黔西北五指山铅锌矿集区是川滇黔接壤铅锌成矿域的重要组成部分之一,近年已探明多个大中型铅锌矿床,提交铅锌金属资源储量超250万t,实现了地质找矿的重大突破。文章对区内典型矿床的地质、地球化学等资料进行综合分析,并与邻区及MVT矿床进行比较。研究结果显示,本区矿体主要赋存于上震旦统灯影组和下寒武统清虚洞组白云岩中,呈层状、似层状和陡倾斜脉状产出,断控和层控特征明显。矿石自然类型为原生硫化矿型,主要金属矿物由闪锌矿和方铅矿组成。矿床形成受构造、层位及岩性、沉积岩相等因素的约束,构造是必要条件和主要控矿因素,灯影组和清虚洞组鲕状白云岩是有利赋矿层位和容矿岩性,局限-半局限的台地-泻湖相沉积为有利沉积岩相条件。成矿物质具有混合特征,其中成矿金属Pb、Zn等主要来源于基底岩石,而矿化剂C和S则分别来自赋矿海相碳酸盐岩及其内的蒸发膏岩。成矿流体属于与右江盆地演化有关的低温中低盐度盆地卤水,矿体是富金属流体在早燕山期区域挤压向伸展转换的动力学背景下卸载,与富硫流体混合的产物,成矿过程与MVT矿床相似。五指山地区铅锌矿床成矿模式的建立,有望推动区内找矿新突破,并为邻区铅锌成矿预测提供理论指导。

Metallogenic model of Pb-Zn deposits in Wuzhishan area, Puding City, Guizhou Province

The Wuzhishan Pb-Zn ore concentration area, located in northwestern Guizhou, is an important part of the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic domain. In recent years, numerous large and medium-sized Pb-Zn deposits have been discovered in this area, with more than 2.5 million tons of Pb+Zn metal reserves. Based on geological and geochemical studies and comparative analysis of the typical Pb-Zn deposits, the authors revealed that orebodies in this area are mainly hosted in dolostone of the late Sinian Dengying Formation and early Cambrian Qingxudong Formation. Orebodies occur dominantly in stratiform and steeply dipping veined forms along the faults. The fault control and layer control features are obvious. Ores are predominated by unaltered sulfides, and mainly consist of sphalerite and galena in the Wuzhishan area. Pb-Zn mineralization is controlled by tectonics, lithology and sedimentary facies, with the tectonics being the necessary and main ore-controlling factor. The ore-bearing Dengying and Qingxudong Formations are favorable lithologic units and the dolostone is favorable ore-hosting rock. The restricted to semi-restricted platform to lagoon facies are favorable sedimentary lithofacies. Ore-forming Pb, Zn metals were derived from basement rocks, whereas C and S were most likely sourced from the marine carbonate rocks and evaporation gypsum within ore-hosting strata, respectively. The ore-forming fluids belonged to low-temperature medium-to low-salinity basin brine that was related to evolution of Youjiang Basin. Pb-Zn deposits in this area were formed by metal-enriched fluids mixed with S-enriched fluids in the transition environment from collisional to extensional tectonics. The ore-forming process is similar to that of MVT deposits. The establishment of metallogenic model in Wuzhishan area is expected to promote new breakthrough in ore-prospecting in this area and provide theoretical guidance for the adjacent areas.