广东圆珠顶斑岩型铜钼矿床蚀变及元素迁移特征分析

Characteristics of wall-rock alteration and element migration of the Yuanzhuding porphyry Cu-Mo deposit,Guangdong Province,China

圆珠顶铜钼矿床是近年来在钦杭结合带南段发现的大型斑岩型铜钼矿床。为查明成矿过程中的围岩蚀变作用及元素迁移特征和研究成矿物质的沉淀机制,对圆珠顶铜钼矿床蚀变与矿化进行了岩相学研究,采用X射线荧光光谱(XRF)和电感耦合等离子质谱法(ICP-MS)对围岩进行全岩主、微量元素分析。结果表明,圆珠顶矿床围岩蚀变以花岗斑岩为中心,向外依次划分为钾硅酸盐化带、绢英岩化带和黄铁绢英岩化带三个蚀变带,蚀变矿物组合分别为黑云母+钾长石+石英+辉钼矿+黄铜矿+黄铁矿+斑铜矿、石英+绢云母+黄铜矿+黄铁矿+辉钼矿和绢云母+石英+黄铁矿+磁铁矿+黄铜矿±辉钼矿±方解石。热液蚀变过程中,Al_(2)O_(3)、MgO、CaO、Na_(2)O、Th、U、Ta、Sr、Zr、Ni、Co等组分发生不同程度的迁出,K_(2)O、Cu、Mo等组分发生迁入,以黄铁绢英岩化带最为显著。热液蚀变作用与流体混合作用是Cu、Mo沉淀的主要机制,钼矿化与钾硅酸盐化蚀变关系密切,铜矿化与绢英岩化蚀变关系密切。

The Yuanzhuding copper-molybdenum deposit is a large-scale porphyry deposit discovered in the southern segment of the Qin-Hang belt in recent years.In order to find out characteristics of wall rock alteration and element migration in the mineralization process of this porphyry deposit,and to study its precipitation mechanism of ore-forming materials,in this paper,we have studied the petrography of the alteration and mineralization of the Yuanzhuding Cu-Mo deposit on the basis of analyses of major and trace elements of wall rocks by using the X-ray fluorescence spectroscopy(XRF)and inductively coupled plasma mass spectrometry(ICP-MS).The results show that the wall rock alteration of the Yuanzhuding deposit occurred with its the center in the granite porphyry and the whole alteration area can be classified into three alteration zones named the potassium silicate,phyllic,and pyrite-sericite-quartz alteration zones with their alteration mineral assemblages of biotite+K-feldspar+quartz+molybdenite+chalcopyrite+pyrite+bornite,quartz+sericite+chalcopyrite+pyrite+molybdenite,and sericite+quartz+pyrite+magnetite+chalcopyrite±molybdenite±calcite,respectively.In the process of hydrothermal alteration,Al_(2)O_(3),MgO,CaO,Na_(2)O,Th,U,Ta,Sr,Zr,Ni,Co were migrated out from the altered rocks in different degrees,while K_(2)O,Cu,Mo were migrated into the altered rocks.Especially,these migrations of elements occurred most significantly in the pyrite-sericite-quartz alteration zone.The hydrothermal alteration and fluid mixing are main mechanisms of the Cu and Mo precipitation.Molybdenum mineralization is closely related to the potassium silicate alteration,while copper mineralization is closely related to the phyllic alteration.