粤东金坑Sn-Cu共生成矿机制研究

It is generally known that granitic rocks associated with Sn deposits are mainly derived from the crust, whilst granitic rocks associated with Cu deposits are predominantly derived from the subducted slab or metasomatized lithospheric mantle. However, several coexisting Sn-Cu deposits have been recently discovered in the eastern Guangdong Province, Southeastern Coast of China. Thus, what is the reason that these two different metallic ores coexist? The Jinkeng is a typical example of coexisting Sn-Cu deposits in the region, and can be an ideal object to address the scientific point. In this project, based on a detailed investigation of ore-forming stages and mineral assemblages of the Jinkeng Sn-Cu deposit, we will carry out analyses of fluid inclusions in quartz and cassiterite, in-situ trace element of cassiterite and chalcopyrite, and Sn isotope of cassiterite and Fe isotope of chalcopyrite from each ore-forming stage, in order to determine the P-T-X-ƒo2 evolution of the ore hydrothermal system, the record and process of the coexisting Sn-Cu mineralization, the mineralization mechanism, and the genetic model of the Jinkeng Sn-Cu deposit, as well as the coexisting Sn-Cu mineralization mechanism. This project provides not only significant clues to understand the genesis of the coexisting Sn-Cu mineralization but also brings some implications for future exploration in the region.

通常认为与锡矿有关的花岗质岩石主要来自于地壳，与铜矿有关的花岗质岩石主要来自于俯冲板片或交代的富集岩石圈地幔。然而，最近在东南沿海粤东地区发现了多个锡铜共生的矿床，那么，是什么原因造成这两种具有不同来源金属矿产共生在一起？金坑Sn-Cu矿床是粤东地区锡铜共生成矿的典型代表，是回答上述科学问题的理想研究对象。本项目以金坑Sn-Cu矿床为研究对象，在详细查明成矿阶段和矿物组合的基础上，开展各成矿阶段石英和锡石流体包裹体、锡石和黄铜矿矿物微区、锡石Sn同位素和黄铜矿Fe同位素研究，旨在确定成矿热液体系P-T-X-ƒo2演化轨迹，厘定锡铜共生成矿记录和过程，查明成矿机制，并建立矿床模型，深刻揭示锡铜共生成矿机理。本研究的开展不仅为深入理解这类Sn-Cu共生成矿作用提供重要的科学依据，而且为区内找矿勘查工作提供重要的启示。

锡和铜具有不同地球化学特征和成矿专属性，但自然界却发育多个锡铜共生的矿床，如全球第一大锡矿云南个旧锡矿和南美的San Rafael锡铜矿床。本项目以粤东沿海地区金坑锡铜矿为研究对象，采用矿物学、成岩成矿年代学、原位微区分析及Sn-Cu同位素等测试方法，对金坑锡铜共生成矿机制开展了系统研究，取得如下主要成果：（1）精确厘定了金坑锡铜矿成岩成矿年代，利用黄铜矿原位Cu同位素，查明了锡铜共生成矿机制；（2）开展了区内锡成矿作用对比研究，系统总结了区内锡矿成矿规律，明确了区内锡矿与侏罗纪火山岩无关，而与早白垩世花岗岩有关，建立了火山岩覆盖区锡矿成矿新模型，为找矿突破提供了重要依据；（3）首次将原位锡同位素应用到成矿作用研究中，发现了单颗粒锡石晶体内部锡同位素的不均一性，建立了锡石精细矿物学与原位锡同位素联合示踪成矿过程的新方法。本项研究共发表SCI论文8篇，一人获得陕西省青年科技新星。