云南丘北县大铁地区铝土矿地质特征及找矿标志

Geological Features and Ore-searching Indicators of the Datie Bauxite Deposit in Qiubei County,Yunnan Province

大铁一水硬铝石沉积型铝土矿床是云南省丘北地区近年来新发现的中型铝土矿床,在滇东南地区具有代表性。本文系统地研究了该矿床的地质特征,总结了其成矿规律与找矿标志,探讨了成矿作用过程。研究表明,大铁铝土矿床含矿岩系为上二叠统吴家坪阶下段,其不整合于上石炭统威宁组或中-上二叠统峨眉山组之上,为一套海陆交互相以铝质、铁质和粘土质为主的碎屑岩系。矿体赋存于含矿岩系的中部,矿石类型主要以碎屑状铝土矿为主,其次为鲕状、致密状、半粗糙状铝土矿。铝土矿床形成于水动力条件相对微弱动荡的低能海岸环境中,潮下带为成矿有利相带,经历了古风化壳发育阶段、沉积-成岩阶段及表生阶段3个阶段。

The Datie diasporic sedimentary bauxite deposit is a medium-sized one discovered in recent years in Qiubei County,Yunnan Province. In this paper,we analyze its geological features and summarized the ore-forming regulat4ties, ore-searching indicators and its mineralization process. The re- sults show that： the ore-bearing rock series was developed in the Longtan Formation of Upper Permian, which is a set of marine-continental transitional fa- cies dominated by aluminous ,ferruginous and argillaceous elastic rock series unconformably overlaps the Weining formation of Upper Carboniferous or the Emeishan formation of Middle-Upper Permian. The ore bodies are hosted in the nfiddle of ore-bearing rock series,and the main ore type is elastic,then oolitic, compacted and half-rough textures. This deposit formed in a low-energy bay environment with the hydrodynamic conditions relatively weakly dis- turbed,where the subtidal zone was a favorable area for ore-formation. The ore-forming process sequentially underwent three metallogenic stages： development stage of palaeo-weathering crust,sedimentation-diagenesis stage and supergene stage.