滇东南广南县砂子塘铝土矿床地球化学特征研究

砂子塘铝土矿床以Al2O3含量高、A/S值高为特征，是滇东南地区少有高品质铝土矿床。笔者以砂子塘铝土矿床沉积型铝土矿为研究对象，研究了该矿床沉积型铝土矿的地球化学特征，进而对其成矿物质来源、成矿环境进行了讨论。含铝岩系的稀土总量总体较高，具中等程度的Eu负异常，具Ce正异常和Ce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。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和亲铁元素Cr，其余元素则明显亏损。含铝岩系之中伴生有黑色金属Ti、稀土元素、分散元素Ga、稀有金属Nb和Li，可以与Al2O3一起综合利用。聚类分析显示，Al2O3与Nb、TiO2、REE呈正相关，而与Ga、Fe2O3、Li呈负相关。含铝岩系灰岩标准化曲线为近水平的"U"字型曲线，含铝岩系的钛率（16.89）与下伏威宁组灰岩的钛率（13.09）接近，说明含铝岩系与下伏的威宁组灰岩关系密切。含铝岩系的Be含量低（3.60×10-6），Th/U较高（6.07），多具Ce负异常，说明砂子塘铝土矿床来源于风化壳，后又经历了沉积作用的改造；Ga含量高（25.25×10-6），Sr含量低（77.7×10-6），Ba含量低（34.4×10-6），V/Zr值较低（0.22），Eu/Sm值较低（0.21），显示出陆相沉积的特征；Sr/Ba值高（3.28），显示出海相沉积的特征。这预示着砂子塘铝土矿床的成矿物质来源于古风化壳，沉积作用改造不明显。

Geochemical Characteristics of the Shazitang Bauxite Deposit in Guangnan County,Southeast Yunnan

Shazitang bauxite deposit is a rare high-quality bauxite deposit in Southeast Yunnan, which is characterized by high Al2O3 content and A/S ratio. In this paper, the sedimentary bauxite has been taken as the research object to study its geochemical characteristics, and then its ore-forming materials sources and metallogenetic environment have been discussed. Aluminum-containing rock series has higher REE contents, showing moderate negative Eu anomaly, positive Ce anomalies and negative Ce anomalies; REE distribution patterns are tilted to the right curve with weak "V"-shaped and various slope, reflecting the varying degree of REE fractionation. LILE (U), HFSE (Nb, Ta, Zr, Hf, Th) and siderophile element (Cr) are significantly enriched in aluminum-containing rock series, the other elements are significantly loss. Cluster analysis shows that Al2O3 is positively correlated with Nb, TiO2 and REE, but it has significantly negative correlation with Ga, Fe2O3 and Li. Aluminum-containing rock series is associated with black metal (Ti), rare earth elements, dispersed elements (Ga), rare metals (Nb and Li), and it can be comprehensively utilizated with Al2O3. REE distribution pattern for normalized aluminum-containing rock series are nearly horizontal "U"-shaped curve, the TiO2/Al2O3 ratio of aluminum-containing rock series (16.89) is close with the TiO2/Al2O3 ratio of limestone in Weining Formation (13.09), illustrating the close relationship between aluminiferous rock series and underlying limestone in Weining Formation. Among aluminum-containing rock series, Be content is low (3.60×10-6), Th/U ratio is high (6.07), and more samples have negative Ce anomalies. These geochemical characteristics indicate that the Shazitang bauxite deposit was sourced from weathering crust and experienced the sedimentation transformation. Ga content is high (25.25×10-6), Sr content is low (77.7×10-6), Ba content is low (34.4×10-6), and V/Zr ratio (0.22) is lower, Eu/Sm ratio is lower (0.21), which shows the continental sedimentary characteristics; Sr/Ba ratio is high (3.28), which indicates the sea facies characteristics; these characteristics indicate that the Shazitang bauxite deposit was derived from the weathering crust, without obvious sedimentation transformation.