山东金翅岭金矿蚀变特征与元素迁移规律

The Alteration Characteristics and Element Migration Law of the Jinchiling Gold Deposit,Shandong Province

胶东地区是中国最重要的金矿集区,区内众多大型-超大型金矿床集中产出,已探明金矿资源量占全国近三分之一。其中石英脉型金矿是区内重要的矿床类型,山东金翅岭金矿就是这一类型的代表之一。通过详细的野外地质观测与室内研究,查明了该金矿床蚀变类型及矿物组合特征,系统采集不同蚀变类型的岩石样品,进行岩石元素地球化学分析,运用质量平衡计算法总结了热液蚀变过程中的元素迁移规律。该矿床原岩为二长花岗岩,含矿热液沿断裂上涌,与围岩发生了强烈的蚀变作用,蚀变类型主要为钾长石化、绢英岩化和黄铁绢英岩化;蚀变过程中的物质交换改变了流体的成分及酸碱度等,流体向蚀变岩提供了大量的Si O2;同时,绢英岩化阶段和黄铁绢英岩化阶段,围岩向流体提供了大量的K、Na,促使流体中的Au活化,引起热液中的Au H3Si O4稳定性降低,造成Au H3Si O4分解,流体中的Fe2+、Fe3+被消耗,形成黄铁矿,导致Au大量沉淀。

Jiaodong area,the most important gold province in China,is an area with concentration occurrence of large and super large gold deposits,the proved reserves in Jiaodong Peninsula account for nearly 1/3 of the country.Among them,the quartz vein type gold deposit is an important type of deposits in the area,and the Jinchiling gold deposit in Shandong is the representative of this type.Based on the detailed geologic observations in the field and indoor research,this paper found out the alteration type and mineral combination characteristics of the gold deposit,collected rock samples of different alteration types,conducted geochemical analysis of rock elements,and summarized the migration law of elements during hydrothermal alteration by using mass balance method.The surrounding rock of the deposit is granite,and the ore-bearing hydrothermal fluid surges along the fault,which has a strong alteration effect on the surrounding rock.This paper argues that the alteration types are mainly potash-alteration,silicification-sericitization and pyritization silicification-sericitization.The material exchange in the alteration process changes the composition of the fluid and so on.The fluid provides a large amount of Si O2 to the altered rock.At the same time,the surrounding rock of the alteration process provides a large amount of K and Na to the fluid,which promotes the activation of Au in the fluid,causing the stability of Au H3 Si O4 in the hydrothermal fluid to decrease,and causing the decomposition of AuH3 SiO4,and then the Fe2+and Fe3+are consumed to form pyrite,resulting in gold mineralization.