淮北煤田宿州矿区山西组泥质岩地球化学特征及地质意义

Geochemical characteristics and geological significance of shaly rocks in Shanxi Formation of Suzhou Mining Area,Huaibei Coalfield

为研究淮北煤田宿州矿区山西组泥质岩地球化学特征及地质意义,通过X射线荧光光谱仪和电感耦合等离子质谱仪等分析测试手段,对研究区山西组泥质岩主微量元素进行了测试并进行分析。结果表明,研究区泥质岩中SiO_(2)、Al_(2)O_(3)质量分数较高,均值分别为62.67%、21.36%。山西组泥质岩中Sc、V、Cr、Ni、Zr、Th等元素相对后太古宙澳大利亚页岩富集,Ba、Ta、Rb、Sr、Nb等元素亏损。泥质岩中稀土元素富集,质量分数为242.4×10^(-6)~302.9×10^(-6),LREE/HREE为8.87~10.01,轻重稀土分异程度大,δEu为0.44~0.72,具有明显的负异常,δCe为0.96~1.14,显示为无异常;稀土元素配分曲线整体模式呈右倾型,相似于后太古宙澳大利亚页岩元素曲线,反映研究区泥质岩主要来源于上地壳。研究区泥质岩m(Al_(2)O_(3))/m(TiO_(2))为22.77~29.47,m(Cr)/m(Zr)为0.22~0.40,结合样品在Th/Sc-Zr/Sc、TiO_(2)-Ni、La/Th-Hf、La/Yb-REE等图解中的投影区域,表明研究区泥质岩物质组分主要来源于上地壳中的长英质岩石,具体为阴山古陆前寒武纪花岗岩。Th-Sc-Zr/10和La-Th-Sc构造环境判别图暗示研究区泥质岩源区为大陆岛弧构造环境。研究区泥质岩m(Sr)/m(Ba)为0.41~0.54,反映微咸水沉积环境;m(Sr)/m(Cu)为3.96~4.89,表明了温暖潮湿的气候条件,m(V)/m(V+Ni)为0.71~0.82,m(Ni)/m(Co)为1.94~3.55,m(Cu)/m(Zn)为0.34~0.71,暗示了沉积水体为厌氧环境、强还原环境,这些地球化学特征表明淮北煤田宿州矿区山西组地层形成于河控三角洲环境,气候条件为温暖湿润,水体为半咸水-咸水。

In order to study the geochemical characteristics and geological significance of shaly rock in Shanxi formation of Suzhou Mining Ar⁃ea,Huaibei Coalfield,the main and trace elements of shaly rock in the study area were tested and analyzed by X-ray fluorescence spectrum and ICP-MS.The results show that the content of SiO_(2) and Al_(2)O_(3)in the argillaceous rocks in the study area is relatively high,with the aver⁃age values of 62.67%and 21.36%,respectively.The elements of Sc,V,Cr,Ni,Zr,TH in shaly rocks of Shanxi Formation are relatively rich compared with those of Australia shale of post Archean,and the elements of Ba,Ta,Rb,Sr,Nb are deficient.The argillaceous rocks are rich in rare earth elements,the content is 242.4×10^(-6)~302.9×10^(-6),LREE/HREE value is 8.87-10.01,the degree of heavy and light rare earth dif⁃ferentiation is large,δEU value is 0.44-0.72,with obvious negative anomalies,δCE value is 0.96-1.14,indicating no abnormality.The overall pattern of REE distribution curve is right dipping,similar to the element curve of Australian shale in post Archean,reflecting that the argillaceous rocks in the study area are mainly from the upper crust.The Al_(2)O_(3)/TiO_(2) and Cr/Zr values of argillaceous rocks in the study area are 22.77—29.47 and 0.22—0.40,respectively.Combined with the projection areas of samples in Th/Sc-Zr/Sc,TiO_(2)-Ni,La/Th-Hf and La/Yb-REE diagrams,it shows that the material components of argillaceous rocks in the study area are mainly from felsic rocks in the upper crust.The discrimination maps of Th-Sc-Zr/10 and La-Th-Sc tectonic environments indicate that the source rocks of the argillaceous rocks in the study area are continental island arc tectonic environments.The Sr/Ba value of argillaceous rock in the study area is 0.41-0.54,reflec⁃ting the brackish water sedimentary environment.The Sr/Cu value is 3.96-4.89,indicating the warm and humid climate conditions,V/(V+Ni)value is 0.71-0.82,Ni/Co value is 1.94-3.55,and Cu/Zn value is 0.34-0.71,indicating that the sedimentary water is anaerobic and strongly restored to the original environment.These geochemical characteristics indicate that the Shanxi formation of Suzhou mining area in Huaibei coalfield formed in the river controlled delta environment,with warm and humid climate and brackish water body.