藏南地区金和锑矿床(点)类型及其时空分布特征

Type and Temporal-Spatial Distribution of Gold and Antimony Deposits (prospects) in Southern Tibet, China

本文首次对藏南地区金和锑矿床(点)地质特征、成因类型和空间分布特点进行了总结,对金和锑成矿作用与中新生代构造-岩浆活动的关系进行了论证,对区域地壳演化过程中金和锑成矿动力学机制进行了讨论。该区的金和锑矿床(点)可按容矿围岩划分为:1变质岩为主要容矿围岩矿床(点),包括金和金-锑矿床(点);2沉积岩为主要容矿围岩矿床(点),包括金、锑、金-锑和锑多金属矿床(点);3火山岩为主要容矿围岩矿床(点),以金-银矿床为代表。根据金和锑矿床(点)空间分布特点和地质特点,将本区划分为4个矿化集中区:拉昂错—马攸木—帕羊金矿化集中区(A),然勒金和锑矿化集中区(B),洛扎—措美锑矿化集中区(C)和邛多江金-锑矿化集中区(D)。各矿化集中区内大多数金和锑矿床(点)与燕山晚期—喜马拉雅早期富碱火成岩具密切时空分布关系,它们是古板块对接碰撞期和碰撞期后大规模构造-岩浆活动的产物。近东西向挤压性和南北向张性断裂交汇部位以及富碱火成岩发育区是寻找金和锑矿床(点)的有利场所。

The southern Tibet region, located at the convergence belt of the Indian Plate and Eurasian continent, is one of the most important gold and antimony metallogenic provinces in southwestern China. High alkaline igneous rocks, gold and antimony deposits (prospects) are well developed in the region due to multiple orogenic events from the Early Paleozoic to Tertiary. All these gold and antimony deposits and prospects can be classified into three types in term of its host rocks and deposit geology: ① hosted by metamorphic rocks; ② hosted by sedimentary rocks; ③ hosted by volcanic rocks. Each of them can also be further divided into gold-only, antimony-only, gold-antimony and antimony polymetallic deposits or prospects. Based on the regional metallogenic studies of the gold and antimony deposits (prospects), four mineralization concentration camps have been outlined. They include La'nga Co-Mayum-Paryang (A), Ranba—Lejinkangsang (B), Lhozhag—Comai (C) and Gongduojiang (D). Among all these four camps, the La'nga Co-Mayum-Paryang (A) camp consists mainly of vein type gold deposits and prospects, while the Lhozhag—Comai camp (C) is dominated by a number of antimony-only deposits (prospects). In contrast, the other two camps comprise gold, antimony and gold-antimony deposits and prospects. The relationship between the regional crustal evolution and gold-antimony metallogeny can be summarized as follows: ① Paleozoic stage: tectonic-magmatism caused by the ancient plate tectonic movements resulted in the ground preparation of gold, antimony and other ore-forming materials, and formed a number of gold-antimony source beds and protore along a certain strata; ② Late Mesozoic to Early Cenozoic stage: a great number of gold, antimony and gold-antimony deposits and prospects were formed by late Yanshanian or Early Himalayan hydrothermal events related to the multiple collision of the Indian Plate and Eurasian continent. The extensional faulting and high alkaline magmatism may play the key role during the formation of the deposits or prospects; ③ Late Cenozoic to present stage: gold- and antimony-bearing un-solidified sediments and hot-springs are considered to be caused by the re-working of the early formed deep-seated faults. Systematic geological investigations on the gold, antimony and gold-antimony deposits (prospects) of the region indicate that the wall rocks of these deposits (prospects) vary from place to place, but most of them show an intimate relation with the Late Yanshanian and Early Himalayan tectonism and high alkaline magmatism. Geological and geochemical features of these deposits have attracted the domestic and international geologists' attentions. The integrated analyses of the geological setting, geological and geochemical features of these deposits and their related wall rocks will greatly upgrade the understanding of the ore-forming processes of the gold and antimony deposits (prospects). Meanwhile, the genetic model and mineral exploration criteria of these deposits (prospects) can also be used during the comprehensive evaluation of the concealed gold and antimony deposits in south Tibet and its neighboring area.