金顶铅锌矿黄铁矿Re-Os定年及其地质意义

Re-Os Isotopic Dating of Pyrite from Jinding Zn-Pb Ore Deposit and Its Geological Significance

关于金顶铅锌矿的成矿时代至今未获得精确的同位素测年数据,这严重制约了我们准确厘定该矿的成矿动力学背景。鉴于此,本文根据黄铁矿的产状特征,将其区分为沉积成岩期和热液期黄铁矿,并开展了Re-Os同位素测年的研究(ICP-MS方法)。虽然黄铁矿的R(e0.4069×10-9～375.2620×10-9)和O(s 0.0008×10-9～0.4131×10-9)含量变化很大,部分样品含量很低,但它们仍然揭示出两组等时线年龄:分别为114±13 Ma和65±10 Ma。笔者认为114 Ma等时线年龄可能代表了沉积成岩过程当中的一期矿化年龄,而65 Ma可能记录了铅锌主矿化之前热液作用开始活动的时间。结合其他方面的地质证据推断金顶铅锌矿主矿化时代可能在28～37 Ma之间。

In this study,Re-Os isotopes of pyrite from the Jinding Pb-Zn deposit were carried out by ICP-MS method.According to occurrences of pyrite,they were identified as sedimentary diagenetic pyrite and hydrothermal pyrite,and showed large variation in contents of Re（0.4069×10-9-375.2620×10-9） and Os（0.0008×10-9-0.4131×10-9）,with low contents of Re and Os in some samples,they display two isochron ages of 114±13 Ma and 65±10 Ma,respectively.Combined with other geological evidences,it is concluded that the two ages could not represent the epoch of the main mineralization which are assessed at 37-28 Ma based on other geological constraints.However,114 Ma is likely related to a mineralization event during diagenesis,while 65 Ma might indicate the beginning of hydrothermal mineralization of Jinding Zn-Pb deposit.