西昆仑地区古生代沉积型铁锰矿床成矿规律及其与原—古特提斯洋演化的关系

Metallogenic regularity of Paleozoic sedimentary iron-manganese deposits in the northern segment of West Kunlun and its relationship with the evolution of the Proto-Paleo-Tethys Ocean

西昆仑地区位于我国著名秦祁昆造山带的西段,经历了长期复杂的地质构造演化。该地区可进一步划分为北昆仑地体、南昆仑地体和喀喇昆仑—羌塘地体,在其构造演化过程中,形成了丰富的矿产资源,以寒武纪沉积变质铁矿、志留纪菱铁矿和石炭纪沉积锰矿最具代表性。本文在剖析典型沉积铁锰矿床地质特征的基础上,结合区域构造演化,重点分析了西昆仑地区铁锰矿成矿规律及地球动力学背景,为总结区域成矿规律及进一步找矿预测工作提供地质依据。西昆仑地区新元古代—早古生代及晚古生代的演化受同时代原特提斯洋和古特提斯洋“开合”构造旋回作用的制约;受区域构造性质的影响,金属矿产以形成于弧后盆地的沉积型铁、锰矿为特色;新元古代晚期—寒武纪为与原特提斯洋南向俯冲有关的弧后伸展盆地发育的大规模沉积变质铁矿床形成阶段,奥陶纪—志留纪为与原特提斯洋闭合有关的残留洋盆环境发育的海相沉积菱铁矿形成阶段,泥盆纪—二叠纪为与古特提斯洋北向俯冲有关的弧后盆地环境沉积锰矿形成阶段。

The West Kunlun area is located in the western section of the famous Qin-Qi-Kun orogenic belt in China,and has experienced long-term complex geological tectonic evolution.The northern section of West Kunlun can be divided into North Kunlun terrane,South Kunlun terrane and Karakoram-Qiangtang terrane.During its tectonic evolution,numerous mineral resources have been formed,among which the Early Cambrian meta-sedimentary iron ores,Silurian siderite ore deposits and the Carboniferous sedimentary manganese ore deposits are the most representative.On the basis of integrating the tectonic evolution of the West Kunlun orogen and in combination with the geological characteristics of typical sedimentary iron-manganese deposits,this paper focuses on the metallogenic regularity and geodynamic background,which provides a basis for summarizing the regional metallogenic belt and further prospecting work.It is suggested that the evolution of the northern segment of West Kunlun orogen during Neoproterozoic-Early Paleozoic and Late Paleozoic was restricted by the"opening and closing"tectonic cycle of the Proto-Tethys Ocean and the Paleo-Tethys Ocean,respectively.Under these regional tectonic settings,metallic minerals are characterized by sedimentary iron and manganese deposits formed in back-arc basins.During the Late Neoproterozoic-Cambrian period,large-scale meta-sedimentary iron deposits developed in back-arc extensional basins related to the southward subduction of the Proto-Tethys Ocean.The formation of sedimentary siderite deposits during Ordovician-Silurian period were developed in residual ocean basin environments related to the closure of the Proto-Tethys Ocean.While the origin of the sedimentary manganese deposits in back-arc basins were related to northward subduction of the Paleo-Tethys Ocean.