青海哆嗦公马矿区中侏罗统沉积环境及聚煤规律
Sedimentary environments and coal accumulation aw of middle Jurassic in Duosuogongma Mining Area of Qinghai
-
摘要: 基于沉积环境与聚煤规律存在着密切的关系,为得出哆嗦公马矿区的聚煤规律,通过实测野外地层剖面及钻孔岩心观察,运用沉积学、煤田地质学的基本理论及方法,研究了哆嗦公马矿区中侏罗世含煤岩系的岩相类型、沉积环境及煤层展布规律。结果表明,该区含煤岩系发育辫状河、辫状河三角洲和湖泊三种沉积环境类型,区域上的厚煤层主要形成于辫状河三角洲沉积环境中。聚煤作用明显受古构造及沉积环境的控制,印支运动控制了侏罗系沉积基底的演化,燕山运动则影响了整个湖盆的发育,此时沿湖泊边缘发育的辫状河三角洲聚煤环境较为发育,从而形成了该区主采煤层下2煤及下1煤。富煤带呈北西-南东向的条带状展布,聚煤中心位于研究区东南部的ZK0-3及ZK11-3钻孔附近。Abstract: Based on close relationship existed between sedimentary environment and coal accumulation of coal-bearing strata in Duosuogongma Mining Area,in or der to have coal accumulation law in the region,in combination with the data of the field outcrop section and borehole core section,the theory and method of sedimentol ogy and coal geology were applied to analyze the lithofacies,depositional environments,and coal distribution of the Jurassic coal-bearing strata.The results showed that the coal-bearing strata were mainly deposited in the braided river, braided river delta and lake environments,and the thick coal seams were formed in the braided river d elta environment.Coal accumulation were controlled by palaeo-tectonics and sedimentary environments.The Indochina Orogeny controlled the evolution of the basemen t of the Jurassic sedimentary basin,and the Yanshanian Orogeny controlled the development of the coal-forming basins.The braid river delta environments were develop ed during this stage, which favored the accumulation of two thick coal seams in the middle Jurassic Muli Formation. The coal-rich belt was distributed along the NW- SE direction,where the coal accumulating center was located in the southeastern part,around the Borehole ZK0-3 and ZK 11-3.