贵州务川大竹园铝土矿床伴生镓富集规律及沉积环境特征

通过对贵州务川大竹园铝土矿床的研究,发现矿床中伴生镓的含量普遍超过了工业综合利用的最低指标。Ga在含铝岩系中均有不同程度的分布,Ga与TiO₂、Cr、Zr、Sn呈中等正相关关系,说明Ga可能赋存于含TiO₂、Cr、Zr、Sn的矿物中; Ga与Al₂O₃呈弱正相关关系,说明Ga可能以类质同象的形式存在于Al的化合物中。Sr/Ba=1.09~19.69>1,表明铝土矿形成于海相沉积环境; Th/U=1.72~12.31,表明铝土矿可能风化作用不彻底; Ga/Al=0.45~1.84,表明成矿介质酸碱度的变化幅度较小。从含矿岩系矿物组合中含黄铁矿、高岭石等矿物可以推断介质为酸性的可能性较大; 稀土元素(rare earth element, REE)球粒陨石标准化分布曲线向右倾斜,轻稀土元素(LREE)富集,重稀土元素(HREE)亏损,δCe显示为弱正异常,Ce/Ce^*=1.17~10.17>1,表明铝土矿形成于富氧的沉积环境,δEu显示为负异常,进一步表明成矿是以氧化环境为主。综合分析认为大竹园铝土矿床形成于以海相沉积作用为主的富氧的沉积环境。

Enrichment rules and sedimentary environment characteristics of associated gallium in bauxite deposit in Dazhuyuan of Wuchuan in Guizhou Province

Through the study of Dazhuyuan bauxite deposit, we found that the content of associated gallium in bauxite deposit generally exceeds the minimum index of industrial utilization. Gallium has a different distribution in ore-bearing rock series and was moderately positively correlated with TiO₂, Cr, Zr, Sn, meaning that gallium may occur in minerals containing Cr, Zr, Sn. Gallium and Al₂O₃ has weakly positive correlation, indicating that gallium is possible to isomorphism exists in the form of aluminum. Also the Sr/Ba is 1.09-19.69, more than 1,showing that bauxite ore formed in marine environment. The Th/U is 1.72-12.31,showing the incomplete bauxite weathering. And Ga/Al is 0.45-1.84, showing that the pH of mineralization medium varies lightly, and mineral assemblages in acidic medium can be inferred by containing pyrite, kaolinite and other minerals in the ore-bearing rocks. The evidences that chondrite-normalized curve of rare earth element (REE) tilted to the right, light rare earth element (LREE) shows enrichment, heavy rare earth element (HREE) shows loss, δCe shows weak positive anomalies and Ce/Ce^* is 1.17-10.17, indicate that the ore-bearing rock series were formed in an oxygen-rich sedimentary environment. Besides δEu appear as negative anomalies, which further indicates that mineralization is in oxide-based environment. Dazhuyuan bauxite deposit is concluded to be formed in marine oxygen-rich sedimentary environment through comprehensive analysis.