甘肃党河南山地区美丽沟岩体地球化学特征、锆石年代学及地质意义

Geochemical characteristics and zircon geochronology of the Meiligou pluton in the Danghenanshan area,Gansu Province and their geological implications

为进一步研究党河南山地区构造运动和金成矿关系,对党河南山地区美丽沟岩体地质特征进行研究。结果表明,该岩体沿北西向断裂构造侵入,由石英闪长玢岩和闪长玢岩构成,以岩株状产出。地球化学特征显示,美丽沟岩体中岩浆岩属于富钠贫钾准铝质岩石,大离子亲石元素Rb、Ba、K、Sr相对富集,稀土元素配分曲线表现为明显的右倾型,Eu元素表现为弱的负异常。根据锆石LA-ICP-MS U-Pb同位素年龄测定结果,该岩体为中三叠世(235±5Ma)岩浆活动产物,表明该区于三叠纪期间岩浆活动较为频繁,构造运动强烈,其可能为该区金元素的再富集提供有利的物理化学条件。

In order to study the relationship between tectonic movements and gold mineralization in the Danghenanshan area,Gansu Province,the geochemical and chronological characteristics of the Meiligou pluton in the area have been studied in this paper.The Meiligou pluton,intruded along the NW-trending fractures,consists of quartz diorite porphyrite and diorite porphyrite,which occurred in the form of stock.The geochemical characteristics show that magmatic rocks in the Meiligou pluton belong to the sodium-rich potassium-poor meta-aluminum rock,with relatively enriched large ionic lithophile elements(LILE)including Rb,Ba,K and Sr,obviously right-declined REE patterns,and weak negative Eu anomalies.The LA-ICP-MS zircon U-Pb isotopic dating results indicate that this pluton is the product of magmatic activity in the middle Triassic(235±5 Ma).The frequent Triassic magmatic activities and strong tectonic movements in this area could have provided favorable physicochemical conditions for the gold re-enrichment.