广东南亩稀土矿床地球化学特征及成矿条件浅析

Geochemical characteristics and metallogenic conditions of Nanmu rare earth ore deposit,Guangdong Province

南亩稀土矿床位于南岭成矿带中段南侧,属离子吸附型稀土矿床,产于中三叠世坪田岩体的花岗岩风化壳中,其产状和形态特征受地形地貌控制。区域上发育多个同类型矿床,成矿条件研究还存在争议。本文针对南亩矿床地球化学特征及成矿标志进行研究,可为区域同类型稀土矿床的勘查找矿提供重要的依据。矿石矿物成分主要为风化后的黏土类矿物,稀土元素以离子状态赋存于黏土矿物上,95.96%离子型稀土赋存于粒径≥0.154 mm的矿物中,稀土组分分布均匀,品位变化稳定。未风化花岗岩包括黑云母花岗岩和碱长花岗岩,与稀土矿石稀土元素球粒陨石标准化配分曲线均为右倾平滑型,轻、重稀土分馏明显,均表现出轻稀土富集特征。通过对成矿条件的初步分析,中三叠世碱长花岗岩和黑云母花岗岩基岩发育区、亚热带温润气候条件、断层、节理发育的浅切割低缓丘陵地形及硅化蚀变带是南亩离子吸附型稀土矿的主要找矿标志。

Nanmu rare earth ore deposit is located in the south of the middle section of the Nanling metallogenic belt,and is an ion adsorption rare earth deposit,produced in the granite weathering crust of the Middle Triassic Pintian pluton,and its production and morphological characteristics are controlled by the topography and geomorphology.Many deposits of the same type have been developed in the region,and the study of mineralization conditions is still controversial.The geochemical characteristics and metallogenic signatures of the Nammu deposit can provide an important basis for the exploration of the same type of rare-earth deposits in the region.The mineral composition of the ore is mainly weathered clay minerals,and the rare earth elements are assigned to the clay minerals in ionic state.95.96%of ionic rare earths are assigned to minerals with particle size≥0.154 mm,and the rare earth components are evenly distributed with stable grade changes.The unweathered granite includes biotite granite and monzogranite,and the standardized distribution curve of rare earth elements spheroidal meteorite of rare earth ore are both right-sloping and smooth,with obvious fractionation of light and heavy rare earths,both showing light rare earth enrichment characteristics.Through the preliminary analysis of mineralization conditions,the Middle Triassic biotite granite and monzogranite batholith,subtropical temperate climate conditions,shallow cut low and gentle hilly terrain developed by faults and joints and silicified alteration zone are the main signs for prospecting ion-adsorbed rare earth ore in Nanmu.