安徽天井山金矿区韩家岩体成因与成矿意义

韩家岩体与天井山金矿空间上密切相关.对韩家岩体的成因存在不同看法：依据“斑状”外貌,有人主张是燕山期花岗斑岩;依据隐约可见的片麻状构造,有人认为是晋宁期灵山岩体.鉴于其具有重要的找矿指示意义,本文通过岩石学、岩石地球化学、同位素年代学等方面的研究,认为韩家岩体是由灵山岩体蚀变而成的绢英岩.天井山金矿中的金多以自然金形式产于石英大脉的晚期裂隙中,并与石英-绢云母-含铁碳酸盐-硫化物细脉共生.研究表明,这些裂隙与绢英岩体顶部的石英网脉带贯通,两者具有相同蚀变矿物组合和流体来源.据此,本文认为与绢英岩化有关的岩浆-构造-蚀变作用是天井山金矿的核心成矿事件.由于韩家绢英岩体具有区域尺度的找矿标志,这对天井山矿区及其外围进一步找矿具有重要的指导意义.

Genesis and merallogenic significance of the Hanjia rock body in the Tianjingshan gold field,Anhui Province

The Hanjia rock body in Xiuning County, Anhui Province, shows a close spatial relationship with the Tianjingshan gold field. There are existed different interpretations about the genesis of the Hanjia rock body. Some researchers support that the rock body is a granite porphyry body formed during the Yanshanian tectonic stage according to the porphyritic texture of the rock body, while the others argue that the granite body is the Lingshan gneissic granite body formed during the Jinningian period considering the indistinct gneissic texture of the rock body. In view of the important ore-hunting indicative significance of the Hanjia rock body, basing on the petrological, petrogeochemical and isotopic geochronological studies of the rock body, this paper suggests that the Hanjia rock body is formed of sericitic quartzites altered from the Lingshan granite body. The golds in the Tianjingshan gold field occur within the late-stage fractures in thicker quartz veins, showing the form of native golds, and having association with quartz-sericite-Fe-car- bonate-sulphide veinlets. The present studies indicate that these fractures link up the quartz developed on the top of the Hanjia sericitic quartzites, and both of them have the same assemblages of altered minerals and sources of fluids. Therefore, the simultaneous magmatism, tectonism and alteration associated with the sericitization are the crucial metallogenic event in the Tianjingshan gold field. As the Hanjia sericitic quartzite body is possessed of a regional ore-hunting indicator, it has an important indicative significance for the further ore-hunting in the Tianjingshan gold field and its peripheral areas.