新疆阿尔泰阿舍勒Cu-Zn矿床结构模型与成矿演化

阿舍勒火山成因块状硫化物(VMS)矿床是中国最大、最具代表性的VMS型Cu-Zn矿床, 但其结构模型仍缺乏系统的总结。在前人研究的基础上, 本次研究进行了野外调查、探槽剖面观察、岩芯采样, 基于观察到的大量钻孔剖面, 本文对阿舍勒矿床进行了解剖, 结果显示: (1)阿舍勒矿床矿石类型多样, 主要包括(致密)块状矿石、条带状矿石、层状矿石、角砾状矿石、浸染状矿石和网脉状矿石, 其中块状与层状矿石属于沉积相矿体, 而网脉状、角砾状矿石与部分浸染状矿石属于通道相矿体。(2) I号矿床包含3个喷流系统, 每个喷流系统都由沉积相与通道相组成。其中位于13线以北的矿体I-2主要为沉积相的块状矿体, 矿体上部的网脉状矿化蚀变带铜锌含量低、并被后期侵位的英安斑岩穿切; 主矿体I-1由2个较大的通道共同补给。(3)矿床喷流成矿具多阶段与叠置成矿特征, 晚期成矿作用交代早期矿体, 矿床顶部的铜锌矿层为后期富集交代而成。通道蚀变分带明显, 中心为硅化带与绿泥石化带, 两侧为绢云母化带; 通道相脉体也表现出垂向的变化特征, 从深部向层状矿体依次为稀疏浸染的微脉带、稀疏浸染的细脉带、中等浸染的粗脉带、稠密浸染的黄铁矿脉及块状黄铁矿。矿床侧向远端发育重晶石与含铁碧玉岩。在此基础上, 本文构建了阿舍勒Cu-Zn矿床结构模型, 探讨了阿舍勒矿床的成矿演化模型, 指出矿床的形成经历了漫长的演化历史, 包括(多期多阶段的)喷流沉积期、变质热液叠加期、剪切变形期和表生氧化期, 并在矿床形成后遭受了绿片岩相变质作用等后期的各种地质作用改造。

Structural model and metallogenic evolution of the Ashele Cu-Zn deposit,Altay, Xinjiang

The Ashele volcanogenic massive sulfide (VMS) deposit is the largest and most representative VMS Cu-Zn deposit in China, but its structural model is still lacking of systematic summary. In this paper, field investigations, excavation pits, drill-core sampling are carried out on the basis of previous studies. Based on a large number of boreholes and profiles observed, the Ashele deposit was dissected. The results show that: (1) There are various types of ore in Ashele deposit, mainly including massive ore, banded ore, stratiform ore, breccia ore, disseminated ore, and stockwork ore. Massive and stratiform ore belong to sedimentary facies orebodies, while stockwork, breccia ore and part of disseminated ore belong to channel facies orebodies. (2) The deposit I contains three exhalation systems, and each of them consists of sedimentary and channel facies. The orebody I-2 located to the north of No. 13 prospecting line is mainly a massive orebody of sedimentary facies, and the upper part of the orebody has low copper and zinc contents in the stockwork mineralized alteration zone, which is cut through by the later emplaced dacite porphyry. The main orebody I-1 is jointly supplied by two larger channels. (3) The Ashele deposit has multi-stage and superimposed ore-forming characteristics, with late mineralization metasomatism early orebody, and the copper-zinc ore bed at the top of the deposit is formed by enrichment and metasomatism in the late stage. The alteration zoning of the channel is obvious, with silicification zone and sericite chloritization zone in the center and sericite zone on both sides. The vein orebody of the channel phase also shows vertical variation characteristics, from the deep to the stratiform orebody, there are sparse disseminated micro-vein zone, sparse disseminated fine vein zone, medium disseminated coarse vein zone, dense disseminated pyrite vein, and massive pyrite. A barite orebody and hematitic jasper are developed in the lateral distal part of the deposit. On this basis, we construct the structural model of the Ashele Cu-Zn deposit, and discuss the metallogenic evolution model of the Ashele deposit. It is pointed out that the formation of the deposit has gone through a long evolutionary history, including (multi-period and multi-stage) exhalation sedimentation period, metamorphic and hydrothermal superposition period, shear deformation period and supergene oxidation period. After the formation of the deposit, it was also transformed by various geological processes such as greenschist facies metamorphism.