胶东寺庄金矿热液蚀变作用与元素迁移规律

Hydrothermal Alteration and Element Migration in the Sizhuang Gold Deposit,Jiaodong Province,China

为探讨胶东寺庄金矿热液蚀变相关的元素活动规律、蚀变机理及其与矿化的关系,对其花岗质围岩的蚀变带进行了研究。结果显示,伴随着金的矿化,在主断裂的上下盘及矿体附近发育比较典型的钾长石化、绢英岩化、硅化、黄铁绢英岩化蚀变带;伴随强烈的矿物交代反应,各蚀变岩的主微量元素发生了较为明显的改变,大离子亲石元素Rb和轻稀土元素La和Ce表现出了一定的活动性,过渡族元素Cr、Co、Ni、Cu等的地球化学行为在蚀变过程中可被强烈改变,重稀土及高场强元素（Ta、Ti、Nb等）,在钾长石化过程中也表现出了很强的活动性。寺庄金矿中金最可能以Au（HS）2^-络合物形式被搬运,流体温度下降及水/岩反应导致含矿热液化学性质的不断变化造成金-硫络合物稳定性的下降,可能是金沉淀的原因。

The Sizhuang gold deposit,located at the Zhaoyuan-Laizhou metallogenic belt in the northwestern border of the Jiaodong Peninsula,is a typical fracture-alteration type gold deposit. The gold mineralization is associated with typical diffusive K-feldspar alteration,sericitization,silicification and pyrite-sericite-quartz alteration at the hanging wall or the footwall of the main fault and near the ore bodies. During the fluid-rock interaction processes,the major and trace elements of altered rock were largely changed. LILE（ Rb） and LREE（ La and Ce） show variable degrees of mobility; TRTE（ Cr,Co,Ni,and Cu） are strongly mobile; HREE and HFSE（ Ta,Ti,Nb） can also be highly modified during the Kfeldspar alteration. The gold in the Sizhuang gold deposit was most likely transported as Au（ HS）^2-complex. When the temperatures of ore-bearing fluid drops or the chemical properties of fluids continuously changed due to water-rock reactions,the stability of Au（ HS）2-complex will be reduced,triggering gold precipitation.