济宁市平原区地砂地质特征及成因分析

Geological Characteristics and Origin of Ground Sand Resources in Plain Area in Ji'ning City

本文结合岩心钻探和实验测试结果,分析了地砂的地质特征,进而探讨了地砂成因。结果表明:地砂粒度以中砂和粗砂为主,主要矿物为石英(60%~75%)和长石(15%~30%),主量元素以SiO 2和Al 2O 3为主,发育大中型交错层理和冲刷面。以南四湖—京杭运河一线为界,湖西区地砂分布零星、面积较小,资源潜力有限。湖东区临沂组一般发育1层地砂,埋深较浅、厚度较大,是目前开采利用的主要层位;平原组一般发育1~3层地砂,整体由东北向西南埋深变深、粒度变细、厚度变薄、层数减少,目前仅在局部地段开采。地砂的成因类型为河床和辫状河三角洲沉积砂,沉积时期气候寒冷干燥、化学风化程度低、水动力条件较强、古水流方向总体由东北至西南,主要发育于晚更新世的辫状河三角洲沉积和全新世的河床沉积。

Based on the results of core drilling and test,geological characteristics of ground sand has been analyzed,and the origin has been studied.It is showed that the grain size of ground sand is mainly medium and coarse sand.Its main minerals are quartz(60%~75%)and feldspar(15%~30%),major elements are SiO 2 and Al 2O 3.There are medium to large scale cross beddings and erosion surface.Taking Jinghang Canal—Nansi Lake as the boundary,the sand in the west part is scattered with small area and limited resource potential.Linyi formation in the eastern part generally develops one layer of ground sand with shallow buried depth and large thickness.It is the main layer for mining at present.Pingyuan formation generally develops one to three layers of ground sand with general characteristics of deeper buried depth,finer particle size,thinner thickness and fewer layers from northeast to southwest.At present,it is only mined in regional sections.The genetic types of ground sand are riverbed and braided river delta sedimentary sand.Due to cold and dry climate,low degree of chemical weathering,strong hydrodynamic conditions and general paleocurrent direction of northeast to southwest during the sedimentary period,groud sand mainly developes in late Pleistocene braided delta sedimentation and Holocene riverbed sedimentation.