赣中紫云山岩体风化产物的元素地球化学特征及其指示意义

Element Geochemical Characteristics Of Weathering Products Of Ziyunshan Rock Body In Central Jiangxi And Its Indicative Significance

赣中紫云山岩体为过铝质花岗岩体,发育有较厚的风化壳,针对其风化产物开展元素地球化学研究,对了解风化过程中的元素迁移与富集规律具有重要意义。本文选取其风化产物开展元素地球化学分析,结果显示,与原岩相比,风化层样品中难迁移元素K、Fe及Al相对增加;Na、Ca、Ti、Mg与P等元素减少,可能是风化过程中斜长石、黑云母、金红石以及独居石等矿物的分解;微量元素U、Sr等相对减少,可能与原岩中晶质铀矿、斜长石以及磷灰石等矿物的分解有关;除Ce之外的所有稀土元素发生富集,其累积原因可能是风化成因的粘土矿物吸附了上部淋滤下来的稀土元素。总体而言,全风化层下部的稀土发生了明显富集,显示赣中地区花岗岩具有一定的离子吸附型稀土矿找矿前景。

Ziyunshan rock body in central Jiangxi is a peraluminous granite body with thick weathering crust.It is of great significance to study the element geochemistry of its weathering products to understand the law of element migration and enrichment in the weathering process.In this paper,the weathering products are selected for element geochemical analysis.The results show that,compared with the original rock,the refractory elements K,Fe and Al in the weathering layer sample are relatively increased;The reduction of Na,Ca,Ti,Mg and P may be due to the decomposition of plagioclase,biotite,rutile and monazite during weathering;The relative decrease of trace elements U and Sr may be related to the decomposition of uraninite,plagioclase,apatite and other minerals in the original rock;All rare earth elements except Ce are enriched,and the accumulation reason may be that the clay minerals of weathering origin absorb the upper leached rare earth elements.In general,the rare earth in the lower part of the completely weathered layer has obviously enriched,indicating that the granite in central Jiangxi has a certain prospect of ion adsorption type rare earth ore prospecting.