川西北马脑壳金矿床控矿因素及其成因意义

马脑壳金矿床位于中国重要的"川、甘、陕"成矿远景区的川西北地区,是川西北地区与构造蚀变带有关的微细浸染型金矿的典型代表。近年来深部勘查、外围找矿和矿山开采发现了许多与原有认识不一致的地质现象,特别是越往深部,构造控矿和热液流体活动的迹象明显增强。根据对矿床地质特征的进一步研究,分析了矿床控矿因素,总结了成矿规律,探讨了矿床成因,指出了进一步找矿的方向。认为马脑壳金矿床以构造控矿为主,构造破碎岩带是主要矿体赋存部位,构造变形程度控制着矿体的空间分布、产出形态和矿化富集程度。多组构造复合部位是重要的赋矿部位,虽然矿(化)体总体呈北西向展布,但北北东向构造、北西向以及南北向构造复合部位是寻找富大矿体的主要方向。矿床表现出的层控性特点,主要与不同物理化学性质岩层的岩石组合有关,能干性(渗透障)与非能干性(不渗透障)岩层的交互叠置和有序排列,导致所有金矿体都产于能干性和非能干性的转换部位,即砂岩、板岩的接触部位。马脑壳矿床的成矿与传统的卡林型金矿有较大的差异,构造—岩浆活动对成矿起了重要的控制作用,有深部流体参与成矿的迹象,属多因复式成矿特征的大型中低温热液金矿床。

Ore-Controlling Factors and Genetic Significances of Manaoke Gold Deposit in Northwest of Sichuan Province

As a typical representative of the fine disseminated gold deposits related with the tectonic alteration zone, Manaoke Gold Deposit is located in the northwestern Sichuan province. Recently, research has found that the deposit of this type is close in space with the tectonic magmatic activities and the deep fluid. With a systematical study of geological characteristics of the deposits, the ore controlling factors and the mineralization are identified on the basis of the study of the geological feature of deposit, the metallogenic regularities of the deposit are summarized, and prospecting orientation is outlined. Manaoke Gold Deposit is primarily controlled by the structure. The location of ore bodies is controlled by the multi stage fractures, cracks and joints of different directions in the Manaoke brittle ductile shear zone, and the tectonic alteration zone is the mainly favorable part for bonanza ores. Although the occurrence of the ore bodies is mainly NW, the compound positions of the NNE, NW and NS structures are the favorable position to find the rich and large ore bodies. Outside the abundance and the occurrence state of the metallogenic elements, stratums combination of different physicochemical properties should assume more responsibility for this. In profile, the lithology association is rhythm of sandstone and slate, which help to form superimposed relationship and ordered arrangement of competent (permeable barrier) and incompetent (impermeable barrier). Almost all of the gold ore bodies occur in transfer sites between competent and incompetent, that is the contact belt of sandstone and slate. The Manaoke Gold Deposit shows obvious difference with the traditional "Carlin type Au deposit". The tectonic magmatic activities play an important role in controlling ore bodies, as well as obvious signs of deep source fluid involved in metallogenesis. The Manaoke Gold Deposit belongs to a large scale medium low temperature hydrothermal gold deposit of polygenetic compound characteristics.