滇东南文山市天生桥-者五舍铝土矿床地球化学特征研究

Geochemical Characteristics of Tianshengqiao-Zhewushe Bauxite Deposit,Southeastern Yunnan Province

天生桥一者五舍铝土矿床近年来在滇东南地区新发现的一个大型铝土矿床，以A120，含量和MS比值高为特征，是滇东南地区少有高品质沉积型铝土矿床。本文以天生桥一者五舍铝土矿床沉积型铝土矿为研究对象，研究了其地球化学特征，对其成矿物质来源进行了讨论。结果表明，矿石中富含稀土元素、分散元素镓、黑色金属钛和稀有金属元素铌，且均已达到工业开采要求。含铝岩系的稀土总量总体较高，但样品之间稀土总量变化较大；具中等程度的铕负异常；铈异常较为复杂，具铈正异常和铈负异常；稀土配分曲线均为向右倾斜的弱“V”字型曲线，斜率不等，反映稀土元素分馏程度不等。下伏咸宁组灰岩以稀土总量低，具铈负异常和铕负异常为特征，其稀土配分曲线为向右缓倾的弱“V”字型曲线。含铝岩系明显富集大离子亲石元素U、高场强元素Nb、Ta、Zr、Hf、Th，其余元素则明显亏损。含铝岩系灰岩标准化曲线为向右缓倾的平滑曲线或“U”字型曲线，表明含铝岩系与下伏的威宁组灰岩关系密切。野外观察发现含铝岩系铝质直接在风化壳上沉积，含铝岩系具复杂的铈异常和中等的Th／U（3～7），这些特征均说明铝土矿的成矿物质主要来源于下伏威宁组灰岩风化形成的风化壳，沉积作用起到了对风化壳上成矿物质的一个改造作用。

Tianshengqiao-Zhewushe deposit is a large bauxite deposit that newly discovered in the southeast Yurman in recent years. This deposit is characterized by high A1203 content and A/S ratio, and is high-quality sedimentary bauxite deposite in Southeast Yunnan. This paper studies the geochemical characteristics of the sedimentary bauxite and discusses its ore sources. The REE, dispersed element Ga, ferrous metal element Ti and rare metal element Nb are rich in the ore, reached the industrial exploitation requirements. In aluminum-containing rock series, total REE contents are higher, with some differences and moderate Eu anomaly; Ce anomaly is more complex, with both positive anomalies and negative anomaly; the weak ＂V＂ shaped curve reflects varying degrees of REE fractionation. Total REE contents of underlying Xianning limestone are low, with Ce negative anomalies and Eu negative anomaly, showing the weak ＂V＂ shaped curve. Aluminum-containing rock is significantly enriched in LILE elements U, with significant loss of high field strength elements Nb, Ta, Zr, Hf, Th, and the remaining elements. Aluminiferous rock series and Weining Formation underlying limestone are closely related. Aluminum of aluminum-containing rock series deposited directly on the weathering crust. Aluminum- containing rock series have complex Ce anomaly and moderate the Th/U （3-7）. These characteristics indicate that ore-forming materials of bauxite mainly come from underlying Weining limestone weathering crust. Deposition plays a transform role in minerals of the weathering crust.