鄂西沉积型赤铁矿含矿沉积盆地与成矿作用分析

Analysis of Ore-Bearing Sedimentary Basins and Mineralization of Sedimentary Hematite in Western Hubei

鄂西是中国沉积型高磷赤铁矿的重要产区,含矿岩系为上泥盆统黄家蹬组和写经寺组,前者主体为近滨亚相沉积,后者为较平坦的远滨带。铁矿化受含矿沉积盆地和岩相古地理环境控制,矿化主要赋存于碎屑岩和碳酸盐岩中。含矿建造层序构成了沉积旋回,与海进-海退相呼应。中泥盆世盆地下陷接受沉积;晚泥盆世下陷加速,在晚泥盆世晚期海水最深。之后盆地抬升,海平面上升,盆地沉积结束。沉积期成矿作用表现为机械沉积作用、胶体沉积作用、化学沉积作用、生物沉积作用,主要形成赤铁矿。成岩期表现为固结作用、重结晶作用和新生矿物充填交代作用,磁铁矿在该期形成。

Western Hubei is an important producing area of high phosphorus sedimentary hematite in China.The ore-bearing rock series consist of the Upper Devonian Huangjiadeng Formation and the Xiejingsi Formation.The former is mainly near-shore subphase deposition,while the latter is a relatively flat far-shore zone.The Fe mineralization is controlled by ore-bearing sedimentary basins and petrographic paleogeographic environment.The mineralization occurred mainly in clastic rocks and carbonate rocks.A complete transgression-retrogression cycle is established in the inner sequence of the formation.The basin began to sink to accept deposition in the middle Devonian,then depression accelerated to the deepest in the late stage of Late Devonian.In the end the basin rose,also causing a rise in sea level,and the basin sedimentary ended.The mineralization in sedimentary period is characterized by mechanical deposition,colloid deposition,chemical deposition and bio-deposi tion,mainly forming hematite.The mineralization in the diagenetic period is characterized by consolidation,recrystallization and new mineral filling metasomatism,forming magnetite.