江西铅山晚石炭世硅质岩地球化学特征与沉积环境  

Geochemistry and Sedimentary Environment of the Late Carboniferous Siliceous Cherts from Yanshan County, Jiangxi Province

作　　者：李二恒[1] 刘家润[1] 倪培[1] 蔡逸涛[1] 赵葵东[1] 叶春林[2] 朱筱婷[3] 

机构地区：[1]内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,南京210093 [2]四川省地质调查院,成都610081 [3]南京地质矿产研究所,南京210016

出　　处：《高校地质学报》2012年第4期735-744,共10页Geological Journal of China Universities

基　　金：中国地质调查局全国危机矿山接替资源找矿项目<闽浙赣相邻区铜多金属矿床成矿规律总结研究>(20089935)

摘　　要：江西铅山晚石炭世硅质岩大多呈条带状、少量呈层状和结核状产出，赋存于灰岩层内或层间；主要由微晶石英组成，含有少量蛋白石或玉髓，未见硅质生物及硅化特点。地球化学分析结果显示，晚石炭世硅质岩的SiO2含量为74．51％～98．48％，Al2O3，TiO2，MgO及∑REE含量低，分别为0．10％～3．42％（平均为0．45％），〈0．01％～0．12％（平均〈0．02％），0．07％～1．46％（平均为0．20％）和〈1．52X10。24．66×10“（平均不足4．84×10“）；δCe值为0．15～0．70（平均为0．42），呈负异常。A12O3与TiO2具有明显的相关性，而两者与SiO2相关性极低。在双变量SiO2-A12O3，SiO2-MgO和三变量Al—Fe—Mn，Fe—Mn一（Ni＋Co＋Cu）判别图上，硅质岩几乎都落入热液成因及生物沉积成因区；在双变量Fe2O3/TiO2-A12O3／（A12O3＋Fe2O3）判别图上，落入大陆边缘沉积区范围。综合地球化学特征及岩石薄片观察结果，可以认为研究区硅质岩形庸千女陆沩绥苴甫I夭『丰尊与海戽执蝻活云fI右羊．Late Carboniferous cherts interbedded with limestone occur extensively in of the county of Yanshan, Jiangxi Province. In this study, 22 chert samples were analyzed for major and rare earth elements. The results show the cherts have low amount of A1203 （0.45%）, TiO2 （〈0.02%）, MgO （0.20%） and ∑REE （〈4.84 × 10^-6） in average. Their δCe values vary from 0.15 to 0.70 with an average of 0.42, indicating negative Ce anomaly. Ai203 shows positive correlation with TiO2. SlOE shows correlation neither with A1203 nor with TiO2. In the SIO2-A1203, SiO2-MgO binary, and A1-Fe-Mn, Fe-Mn-（Ni＋Co＋Cu） ternary discriminant diagrams, the chert samples fall mainly within the hydrothermally and biologically deposited areas. Moreover, the chert samples fall in the area of continental margin in the Fe203/TiO2-A1203/（A1203＋Fe203） binary discriminant diagram. All these geochemical and petrographic characteristics of cherts suggest that the origin of Late Carboniferous siliceous cherts in Yanshan county was chiefly related with submarine hydrothermal solution, and that the cherts were deposited in a continental margin setting with a little terrestrial matter. This study shows that Yanshan area was an marine environment with the activity of hydrothermal solution rich in silica during the deposition of the Late Carboniferous siliceous cherts.

关 键 词：硅质岩 地球化学 沉积环境 晚石炭世 江西铅山 

分 类 号：P539[天文地球—古生物学与地层学] P595[天文地球—地质学]