贺兰山中南部香山群地球化学特征及构造沉积背景

Study on Geochemical Characteristics and Tectonic Sedimentary Background of Xiangshan Group in the Central and Southern Helan Mountain

为了明确贺兰山中南部地区早古生代的构造沉积背景,对香山群硅质岩和碎屑岩区域系统采样,并进行地化特征对比分析,探讨构造背景及沉积环境。研究表明,香山群硅质岩w(A1)/(w(A1)+w(Fe)+w(Mn))均值0.42,w(Fe)/w(Ti)均值33.10,受热液和生物成因的共同作用,北部偏生物成因,南部多热液成因。碎屑岩样品w(Al 2O 3)/w(MnO)均值309,w(Al 2O 3)/w(CaO)均值50.41,w(V)/(w(V)+w(Ni))均值0.74,指示处于陆源碎屑供应充足的厌氧环境。综合w(Fe 2O 3)/w(TiO 2)-w(Al 2O 3)/(w(Al 2O 3)+w(Fe 2O 3))、w(K 2O)/w(Na 2O)-w(SiO 2)/w(Al 2O 3)图解及典型沉积构造分析,认为研究区早古生代为被动大陆边缘斜坡-半深海平原环境,以中卫-青铜峡断裂为界,由北向南水体逐渐变深。

In order to clarify the tectonic and sedimentary background of Early Paleozoic in the central and southern Helan Mountain,systematic sampling was carried out in the siliceous rock and clastic rock area of Xiangshan Group,and the geochemical characteristics of the samples were comparatively analyzed to discuss the tectonic background and sedimentary environment of Paleozoic in this area.It is shown that the average of w(A1)/(w(A1)+w(Fe)+w(Mn))of the siliceous rock samples is 0.42,and the average of w(Fe)/w(Ti)is 33.10.Due to the joint action of heating fluid and biogenesis,the northern part of the study area is more biogenic and the southern part is more hydrothermal.The average value of w(Al 2O 3)/w(MnO)of the clastic rock samples is 309,the average value of w(Al 2O 3)/w(CaO)is 50.41,and the average value of w(V)/(w(V)+w(Ni))is 0.74,indicating that the samples are in an anaerobic environment with sufficient supply of terrigenous debris.Based on w(Fe 2O 3)/w(TiO 2)-w(Al 2O 3)/(w(Al 2O 3)+w(Fe 2O 3)),w(K 2O)/w(Na 2O)-w(SiO 2)/w(Al 2O 3)diagrams and the analysis of typical sedimentary structure,it is held that the early Paleozoic in the study area was in a passive continental margin slope-bathyal plain environment,divided by the Zhongwei-Qingtongxia fault,and the water gradually deepens from north to south.