江南古陆及邻区世界级斑岩钨矿带成矿作用与成矿背景

Porphyry tungsten deposit used to be less economic ore deposit type. Therefore, a few researches have been carried out update. However, a large group of porphyry tungsten deposits represented by the Dahutang and Zhuxi super-large ones have been explored, forming a world - class porphyry tungsten deposit belt. The basic characteristics and ore-forming process are important scientific concerns which need to understand. Particularly, the tungsten ore belt shares same ages in time with and parellel spatially to the Middle - Lower Yangtze River Valley porphyry - skarn copper ore belt. Their metallogenic geodynamic process and genetic relationship are the other important scientific point concerned in the field of geology..This application form submmited focuses on those two scientific points to perform research in detail at two levels. We are going to choose six representative porphyry - skarn tungsten deposits for key study, comprising the exsolution from the melt at the latest magmatic fractionation to fluids, fluid evolution and ore download, sources of ore substances, basic ore and alteration zoning,and simulation experiement for leaching the copper, a major by-product element of the porphyry tungsten ores, in the basic rocks intercalated in the country rocks to join ore fluid system.Based on those studies we try to understand the ore-system and ore-forming processes of porphyry tungsten deposits so as to set up a new model which can be used for further prospecting and exploration. Based on the precise mapping for the ores and related magmatic rocks in the porphyry tungsten ore belt, Sr-Nd-Hf isotopic measurements for the related granitoids, study of ore-control structures and regional tectonic, and compairison of the tunsten ore belt with the Middle - Lower Yangtze River Valley porphyry copper ore belt we try to set up a regional metallogenic geodynamic model so as to contribute some new content to the subject of economic geology over the world.

斑岩钨矿曾是一种经济价值很小的矿床类型，研究程度颇低。但过去几年在我国长江中下游南侧发现和探明了以大湖塘和朱溪为代表的一批超大型-大型斑岩钨矿，构成了一个世界级斑岩钨矿带。这些斑岩钨矿的成矿特点和形成过程是一个有待于查明的重要科学问题，尤其是该矿带与长江中下游斑岩-矽卡岩铜矿带同时形成，空间上平行分布，两者之间关系及其成矿动力学背景是一个重要的科学之谜。本项申请针对这两个科学问题，从两个层面进行研究。选择6个典型矿床实施解剖研究，开展从熔体到流体转变过程，流体演化与成矿，成矿物质来源，矿化蚀变分带特点以及伴生铜元素来自基性围岩的实验研究，深入探讨斑岩钨矿成矿系统和成矿过程，建立普适性斑岩钨矿床模型。以矿床和有关岩石精细测年为基础，结合与成矿岩石组合的Sr-Nd-Hf同位素测定，控矿构造-矿田构造-区域构造的调查与配置，对比长江中下游铜矿带，建立成矿地球动力学模型，为矿床学发展增添新内容。

在我国长江中下游南侧新发现和探明了一批超大型-大型斑岩-矽卡岩W矿，如大湖塘和朱溪矿床，构成了一个世界级斑岩W矿带。本项目针对世界级大型斑岩W矿成矿系统和成矿机制和江南古陆W矿带与长江中下游Cu矿带近乎同时平行产出动力学机制开展研究。本次研究获得了江南W矿带时空分布特征，指出存在两个成矿时间段，即150~135 Ma W-Mo-Cu矿和130~125 Ma W-Sn矿。查明与W成矿有关花岗岩类的性质，包括高分异还原性S型黑云母二长花岗岩和氧化性I型花岗闪长岩，超大型W矿床常常与前者相关。提出江南古陆W矿带与长江中下游Cu成矿带板块尺度范围内近于平行、同时代共生产出与俯冲板片在此发生撕裂，出现板片窗有关。分别建立了斑岩W矿床中矿体在围岩中和矿体在成矿相关岩体内部矿床模型，包括一类在岩体内部的多旋回矿脉生长新模型，其受控于岩浆结晶速率和出熔流体时间。修正了矽卡岩W矿床中矽卡岩-云英岩阶段和硫化物的成因次序，其与岩浆中H2O和硫化物的饱和次序相关。初步探讨了超大型W矿床—朱溪矿床中出现含白钨矿的钙长岩和钠长岩的成因机制。江南古陆W矿带中WO3储量超过500万吨，是全球范围下一个W资源储备基地。本研究提出的江南古陆W矿带的成矿规律、巨量W多金属聚集机理、W多金属矿床成矿–蚀变模型，无论为其它地区勘查W矿，还是对该地区继续开发和勘查W矿床，都提供了高效有力的理论保证和实践思路。同时本项目研究工作也丰富了矿床学。