滇东南丘北县大铁铝土矿床微量元素特征与成矿环境

Research on Trace element geochemical characteristics and ore-forming environment of the Datie bauxite deposit in Qiubei county,the southeast Yunnan province

大铁铝土矿床是近年来在滇东南地区新发现的大型铝土矿床,普遍伴生Fe,Ti,Ga,为低铝高铁高钛铝土矿床。文章通过ICP-MS分析测试,研究了大铁铝土矿含铝岩系微量元素的特征及成矿作用。大铁铝土矿含铝岩系Be含量(2.66×10-6)较低、Th/U值(4.83)中等、Ti含量(33 702×10^(-6))高、LREE/HREE(10.52)中等、δ(Ce)(1.55)高,说明其成矿物质来源于风化壳,后又经历了沉积作用的改造;Ga含量(29.63×10-6)高、Sr/Ba值(11.51)高、Sr含量(70×10-6)低、Ba含量(518×10^(-6))高、V/Zr值(0.97)较高、Li含量(163×10^(-6))高,总体上显示出海相沉积特征,部分样品显示出陆相沉积特征,这也预示着其成矿物来源于风化壳,局部沉积作用改造不明显,亦显示出近源沉积的特征。研究结果表明,大铁铝土矿床含铝岩系成矿物质来源于风化壳,残积作用明显,沉积作用起到对铝土矿改造和再沉积作用;大铁铝土矿床形成于海相环境,海水对成矿物质的改造不充分,部分微量元素显示出陆相沉积的特征。

Datie bauxite deposit is a large bauxite deposit newly discovered in the southeast Yunnan in re- cent years. It is low in A1, high in Fe and Ti with Fe, Ti and Ga as by-products. ICP-MS test were car- ried out to study characteristics of trace elements and metallogeny of the Al-bearing rock series. The re- sults show lower Be（2.66× 10^-6）, medium Th/U（4.83）, high Ti（33 702× 10^-6） , medium LREE/HREE （10.52）, high δ（Ce）（1.55） indicating that the ore materials come from weathering crust and is reworked after deposition. High Ga （29.63×10^-6）, high Sr / Ba （11.51）, low Sr （70×10^-6） , high Ba （518× 10^-6）, higher V/Zr （0.97） , and high Li （163×10^-6） reflect a general sea facies feature. Some samples show terrestrial facies and indicates source of the ore materials from weathering crust. Locally, no obvi- ous reworking occurs in the sedimentation thus proximal sedimentation took place. In summary the ore materials of the Al-bearing series come from the weathering crust with obvious residual sedimentation and the bauxite is reworked and re-deposited during sedimentation~ the bauxite deposit is formed under sea fa- cies with incomplete reworking of the ore materials and terrestrial facies sedimentary feature.