云南思茅盆地大平掌铜金多金属矿床金的赋存状态

大平掌矿床是西南三江地区重要的铜金多金属矿床，为系统地对比研究矿区16号勘探线新发现两类金矿体，即V₁块状硫化物矿体中顺层产出的层状金矿体、穿层断裂带中的网脉状金矿体中金的赋存状态、载金矿物类型，探讨金的沉淀机制。文章基于详实的野外地质调查，运用光学显微镜、扫描电镜(SEM)观察，结合电子探针(EPMA)分析和激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)原位微量元素分析。结果表明，两类金矿体矿石中可见金为金的独立矿物(银金矿、碲金矿、碲金银矿)，以裂隙金形式赋存，层状金矿体矿石中还可见晶隙金；热液型黄铁矿是两类金矿体矿石的主要载金矿物，其中“不可见金”均以固溶体金(Au⁺)为主，存在极少数的纳米金(Au⁰)。两类金矿体金的成矿均受后期东西向断裂带影响，为后期具有较高碲逸度的成矿热液充填成矿提供有利空间，金的独立矿物颗粒细小且分布不均，是由流体的沸腾和混合作用以及不平衡、不稳定的流体体系造成；两类金矿体中固溶体金(Au⁺)均由Au⁺占据黄铁矿晶格空位或缺陷等畸变形成。

Occurrence of gold in Dapingzhang copper-gold polymetallic deposit, Simao basin, Yunnan

The Dapingzhang deposit is an important copper-gold polymetallic deposit in the Sanjiang area region of southwestern China. In order to systematically and contrastively research the occurrence state of gold, the types of gold bearing minerals and the gold precipitation mechanism of two kinds of newly discovered gold orebodies in No. 16 exploration line of the mining area, namely, the layered gold orebody produced in bedding in V₁ massive sulfide orebody and the stockwork gold orebody in the transbedding fault zone.In this paper, based on detailed field geological survey, optical microscope, scanning electron microscope (SEM) observation, combined with electron probe micro-analysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in situ trace element analysis are used. The research results show that the independent gold minerals (electrum, calaverite, petzite) can be seen in the form of fissure-gold in the two types of gold orebodies, and there is also interstitial-gold in the layered gold orebody. Hydrothermal pyrite is the main gold bearing mineral of the two gold orebodies, among which the "invisible gold" is mainly solid solution gold (Au⁺) and rare nano-gold (Au⁰). The gold mineralization of the two kinds of gold orebodies is affected by the late east-west fault zone, which provides favorable space for the filling and mineralization of hydrothermal fluid with high tellurium fugacity. The individual mineral particles of gold are fine and unevenly distributed, which is caused by the boiling and mixing of fluids and the unbalanced and unstable fluid system. The solid solution gold (Au⁺) in the two kinds of gold orebodies is formed by Au⁺ occupying the pyrite lattice vacancies or defects.