Elemental characteristics and paleoenvironment reconstruction： a case study of the Triassic lacustrine Zhangjiatan oil shale, southern Ordos Basin, China

作     者：Delu Li Rongxi Li Zengwu Zhu Xiaoli Wu Futian Liu Bangsheng Zhao Jinghua Cheng Baoping Wang 

作者机构：School of Earth Sciences and Resources Chang'an University Xi'an 710054 China Shaanxi Center of Geological Survey Xi'an 710068 China Yanchang Oilfiled Co.Ltd Yah'an 716000 China 

出 版 物：《Acta Geochimica》 (地球化学学报（英文）)

年 卷 期：2018年第37卷第1期

页      面：134-150页

核心收录：

学科分类：07[理学] 

基　　金：supported by funding from the National Natural Science Foundation of China (No.41173055) the Fundamental Research Funds for the Central Universities (No.310827172101) 

主　　题：Trace elements Occurrence mode Paleoenvironment Zhangjiatan oil shale Yanchang Formation Ordos Basin 

摘      要：Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray diffraction, the quality, mineral content, occurrence mode of elements, and paleoenvironment of the Zhangjiatan oil shale of the Triassic Yanchang Formation in the southern Ordos Basin were studied. The analyses revealed relatively high oil yield(average 6.63%) and medium quality. The mineral content in the oil shale was mainly clay minerals,quartz, feldspar, and pyrite; an illite–smectite mixed layer comprised the major proportion of clay minerals. Compared with marine oil shale in China, the Zhangjiatan oil shale had higher contents of quartz, feldspar, and clay minerals, and lower calcite content. Silica was mainly in quartz and Fe was associated with organic matter, which is different from marine oil shale. The form of calcium varied. Cluster analyses indicated that Fe, Cu, U, V, Zn, As,Cs, Cd, Mo, Ga, Pb, Co, Ni, Cr, Sc, P, and Mn are associated with organic matter while Ca, Na, Sr, Ba, Si, Zr, K,Al, B, Mg, and Ti are mostly terrigenous. Sr/Cu, Ba/Al, V/(V+ Ni), U/Th, AU, and δU of oil shale samples suggest the paleoclimate was warm and humid, paleoproductivity of the lake was relatively high during deposition of the shale—which mainly occurred in fresh water—and the paleo-redox condition was dominated by reducing conditions. Fe/Ti ratios of the oil shale samples suggest clear hydrothermal influence in the eastern portion of the study area and less conspicuous hydrothermal influence in the western portion.