四川木里梭罗沟金矿床载金黄铁矿原位微量元素特征

The in-situ trace elements of gold-bearing pyrites from Suoluogou gold deposit, Muli, Sichuan

关键词:  造山型金矿床  黄铁矿  原位微量元素  甘孜–理塘缝合带  木里  梭罗沟

Key words:  orogenic gold deposits  pyrite  In-situ trace element  Garze-Litang suture zone  Muli  Suoluogou deposit

摘要:

甘孜–理塘缝合带是四川重要的金矿带之一。梭罗沟大型金矿床是该带上的典型矿床，但其矿床成因仍存在争议。为了准确厘定其矿床成因，本文对梭罗沟金矿床中的它形和自形（五角十二面体）的载金黄铁矿进行了LA-ICP-MS原位微量元素分析。结果显示梭罗沟它形黄铁矿元素含量变化较小，较为集中，而自形黄铁矿具有明显的核–幔–边结构，元素含量变化范围较大。总体上，两种黄铁矿中Au与As均具有明显的正相关性，但Au与FeS₂和Co/Ni值具有负相关性。它形黄铁矿和自形黄铁矿的Co/Ni值分别为0.2和57.1，两者都具有较高的Au和较低的Ag含量；这表明它形黄铁矿主体来源于沉积作用，受后期成矿热液改造，而自形黄铁矿属于热液成因。梭罗沟金矿床成矿过程为火山–沉积岩中的Au在变质热液作用下再活化富集的结果，属于典型的造山型金矿床。

Abstract:

The Soluogouis a large-scale gold deposit in Garze-Litang Suture, but its genesis is still controversial. In order to probe into the genesis of the Soluogou deposit, LA-ICP-MS in-situ trace element analyses of anhedral and euhedral pyritohedron gold-bearing pyrites from the Soluogou gold deposit have been carried out. The results show that the variation range of elements' contents of anhedral pyrite in Soluogou is narrow, while euhedral pyrite has obvious core-mantle-edge structure and its variation range of elements' contents is large. On the whole, Au in pyrite is positively correlated with As and negatively correlated with FeS₂ and Co/Ni values, existing in the form of lattice gold. The Co/Ni values of anhedral and euhedral pyrite are 0.2 and 57.1, respectively. Both anhedral and euhedral pyrites have a high Au content and a low Ag content. It is concluded that anhedral pyrite is derived from sedimentation while euhedral pyrite is formed in hydrothermal process. The Soluogou gold deposit is a typical orogenic gold deposit, which is characterized by the reactivation and enrichment of Au in volcanic-sedimentary rocks under the action of metamorphic hydrothermal.