云南省大关地区泥盆系地层序列特征及其工业砂资源潜力分析

Devonian stratigraphic sequence in the Daguan area of Yunnan Province and its resource potentials of industrial quartz sand

云南省大关县泥盆系蕴藏着丰富的石英砂资源,地层序列的研究不仅有助于深入分析石英砂形成的古地理环境及其变化特征,而且结合构造背景的研究,可研究石英砂形成分布规律,为硅产业的开发提供理论依据。为此,本文以野外地层剖面测量及页岩气调查井岩心编录为基础,结合古构造背景,研究了在直线距离50 km的滇东北大关县、盐津县泥盆系剖面特征,认为该区泥盆系具以下特点:(1)研究区位于晚古生代滇黔桂裂谷北部边缘地带,受边缘相带控制,沉积了坡松冲组、缩头山组两套高成熟度石英砂岩,是滇东北硅产业园的资源基础;(2)大关、盐津地区泥盆系总体上由下向上发育了坡松冲组、坡脚组、箐门组、缩头山组、红崖坡组、曲靖组、在结山组七个组,但受裂谷盆地隆、凹相间格局及同生断裂控制,七个组常发育不全,不同的地点,沉积序列常不一致,变化极其频繁;(4)泥盆系总体经历了两次海退→海进沉积过程,反映由陆架建设到碳酸盐台地的形成过程,同时,受裂谷盆地的影响,各组与建组剖面只是相似,具一定的变化特征;(4)总体上,缩头山组资源潜力优于坡松冲组。坡松冲组以盐津中和镇最具开发前景,缩头山组以大关县木杆镇及大关县黄荆坝最具前景。这些对泥盆系石英砂的开发具指导意义。

The Devonian System in Daguan County of Yunnan Province is rich in quartz sand resources.The study of stratigraphic sequence in this area can not only contribute to the in-depth analysis of the paleogeographic environment and its variation characteristics of quartz sand formation,but also can reveal the formation and distribution rules of quartz sand with the help of tectonic background,and finally provide theoretical basis for the development of silicon industry.Therefore,based on the field stratigraphic profiling and core logging of shale gas wells,and combined with the paleotectonic background,this paper studied the Devonian profile characteristics in Daguan and Yanjin counties in northeast Yunnan Province with a straight-line distance of less than 50 kilometers.This area is located in the northern margin of Dianqiangui rift in Late Paleozonic,where controlled by the edge facies zone,two sets of high maturity quartz sandstone were deposited in Posongchong Formation and Suotoushan Formation.In general,seven Devonian formations were deposited,including Posongchong,Pojiao,Qingmen,Suotoushan,Hongyapo,Qujing,Zaijieshan from bottom to top in order,but these seven formations are often incomplete and vary very frequently at different locations.Controlled by the pattern of uplift and depression in the rift basin and syngenetic fractures,the sedimentary sequence is often inconsistent in different locations.The Devonian strata witnessed two regressive and transgressive depositional processes,reflecting the formation process from continental shelf construction to carbonate platform,and the strata of each formation are similar to those of stratotype section with certain variety characteristics.On the whole,the resource potential of Suotoushan Formation is better than that of Posongchong Formation.Zhonghe Town of Yanjin County is the most promising development prospect of industrial quartz sand for the Posongchong Formation,and Mugan Town and Huangjingba Town of Daguan County are the most promising prospects for the Suotoushan Formation,which are of guiding significance to the exploration of Devonian quartz sand.