赣南燕山期水头岩体的锆石铀-铅年代学研究及其含矿性评价

水头岩体是目前赣南地区缺少精确年龄数据的复式岩体之一。对赣南水头岩体中的锆石样品进行了U-Pb法年代学研究,测年结果显示该岩体主体年龄为(142.7±0.6)Ma,属于燕山期的产物,并不是前人认为的加里东期。但也存在前期(海西期和加里东期)的同位素年龄信息记录,说明该岩体是复式岩体,存在至少三期岩浆活动。对水头岩体进行了岩石学、地球化学研究,简要论述了岩石成因及含矿性。水头岩体主体为黑云母花岗岩,为过铝质钾玄岩系,轻稀土和重稀土中等分馏,负Eu异常明显。初步认为水头岩体是原地重熔交代作用形成的复式岩体。岩石化学资料数据显示,该岩体具备稀土成矿母岩的基本条件。

Zircon U-Pb Dating and Ore-bearing Properties Evaluation of Yanshanian Shuitou Pluton in Southern Jiangxi Province

The Shuitou pluton is one of the composite plutons without accurate dating age in Southern Jiangxi province. Zircon samples taken from the Shuitou pluton were selected for U-Pb dating. The obtained age of (142.7±0.6) Ma confirmed that this granitic pluton belongs to the Yanshanian era and not the Caledonian era as a previous study has reported. Other old ages were also obtained for this pluton (such as Hercynian and Caledonian), which indicates that there were at least three periods of magmatic activity. This study indicates that Shuitou pluton is a composite pluton. Combining the petrological and geochemical study on this pluton, petrogenesis and ore-bearing properties are illustrated briefly in this paper. The Shuitou pluton mainly consists of biotite granites, which can be attributed to the peraluminous shoshonitic series with a middle fractionation of light rare earth element (LREE) and heavy rare earth element (HREE), and obvious Eu anomalies. These data indicate that the Shuitou pluton is a composite pluton formed by the result of in-situ-melting of granite. The geochemical data from this study show that this pluton has major mineralization conditions of mother rock for REE deposits.