鄂尔多斯盆地长9页岩烃源岩的元素组成及其古沉积环境

doi:10.19657/j.geoscience.1000-8527.2023.039

摘要/Abstract

摘要：

针对鄂尔多斯盆地长9页岩元素特征的研究相对薄弱,对其沉积环境缺乏全面揭示。本研究基于能量色散X射线荧光技术,采用优化的能量配置方法进行高精度的元素组成刻画,使得元素的有效识别数量达到29个。依据长9页岩的元素组成特征,对沉积时期的古气候、古盐度、古氧化还原状态、古生产力、古水体封闭性、物源输入等沉积环境条件进行了系统化剖析。研究结果表明,长9页岩的11个主量元素,其元素平均含量达到38341.54 μg/g;18个微量元素,其元素平均含量为160.12 μg/g。主量元素中,Si、Al、Fe、Ca和K的含量最高;微量元素中,Ba、Rb、Sr和Zr 4种元素的含量最高。长9页岩的微量元素中,V、Cu、Th、Rb、Zr、Nb表现为相对亏损,Co、Ni、Zn、Ga、Pb、U、Y、Cr表现为微弱富集,Ba、Sr、Mo表现为一般富集,As表现为非常富集。长9页岩的沉积环境为气候偏湿润,水体为相对贫氧-弱氧的淡水水体,水体封闭性为中等封闭-弱封闭,陆源物质供给稳定和单一,初级生产力较强。

关键词: 主要元素, 微量元素, 沉积环境, 长9页岩, 鄂尔多斯盆地

Abstract:

The research on the element characteristics of Chang 9 shale in Erdos Basin is inadequate, and the sedimentary environment is not fully revealed.Based on energy dispersive X-ray fluorescence technology, we used the optimized energy setting method to characterize the major and trace elements, which increases the number of measured effective elements to 29.Based on the element composition characteristics of the Chang 9 shale, the sedimentary environment (incl.paleo-climate, paleo-salinity, paleo-redox state, paleo-productivity, and provenance input) is systematically analyzed.The results show that the average content of 11 major elements in Chang 9 shale is 38,341.54 μg/g; the average content of 18 trace elements is 160.12 μg/g.Si, Al, Fe, Ca and K have the highest contents among the major elements; Ba, Rb, Sr and Zr have the highest contents among the trace elements.For the trace elements of the Chang 9 shale, elements including V, Cu, Th, Rb, Zr and Nb are relatively depleted; elements including Co, Ni, Zn, Ga, Pb, U, Y and Cr are weakly enriched; elements including Ba, Sr and Mo are moderately enriched; arsenic is highly enriched.The sedimentary environment of Chang 9 shale has the following characteristics: humid climate, freshwater water and weakly oxidized, medium to weak closing lake, stable terrigenous materials input, and strong primary productivity.

Key words: major element, trace element, sedimentary environment, Chang 9 shale, Ordos Basin

中图分类号:

师良, 范柏江, 王霞, 李亚婷, 黄飞飞, 戴欣洋. 鄂尔多斯盆地长9页岩烃源岩的元素组成及其古沉积环境[J]. 现代地质, 2023, 37(05): 1254-1263.

SHI Liang, FAN Bojiang, WANG Xia, LI Yating, HUANG Feifei, DAI Xinyang. Element Composition and Sedimentary Environment of Chang 9 Shale Source Rocks in the Ordos Basin[J]. Geoscience, 2023, 37(05): 1254-1263.

图/表 13

图1 研究区概况及取样位置

Fig.1 Structural units of the study area and the sampling locations

图2 长9页岩的岩心特征及显微组分特征 (a) C35井,1613.68 m,黑色页岩中含植物遗迹; (b) Y30井,1670.1 m,黑色页岩的断面光滑; (c) C35井,1612.6 m,黑色页岩中含植物遗迹; (d) Y54井,1612.6 m,灰黑色页岩中含砂质组分; (e)Y29井,1602.1 m,页岩中的镜质体; (f) Y30井,1663.39 m,页岩中的孢子体和藻类体; (g) Y26井,1604.42 m,页岩中的树脂体和藻类体; (h)Y25井,1533.21 m,页岩中的树脂体和沥青质; (i) Y29井,1602.1 m,页岩中充填黑色的沥青质

Fig.2 Core characteristics and microscopic characteristics of macerals from the Chang 9 shale

图3 长9页岩基本地化特征

Fig.3 Basic geochemical characteristics for the Chang 9 shale

图4 长9页岩的有机质类型

Fig.4 Organic matter types for the Chang 9 shale

图5 长9页岩不同元素的含量对比

Fig.5 Contents of various elements for the Chang 9 shale

图6 长9页岩微量元素的富集程度对比 1.严重亏损; 2.一般亏损; 3.微弱富集; 4.一般富集;5.富集; 6.非常富集

Fig.6 Enrichment factors of trace elements for the Chang 9 shale

图7 长9页岩的C数值与w(Sr)/w(Cu)的关系及w(SiO2)/w(Al2O3)与w(Rb)/w(Sr)的关系

Fig.7 Plots of C values vs. Sr/Cu, SiO2/Al2O3 vs. Rb/Sr for the Chang 9 shale

图8 长9页岩w(SiO2)与w(Al2O3+K2O+Na2O)的关系及w(Ga)/w(Rb)与w(K2O)/w(Al2O3)的关系

Fig.8 Plots of SiO2 vs.Al2O3+K2O+Na2O, Ga/Rb vs.K2O/Al2O3 for the Chang 9 shale

图9 长9页岩w(Sr)/w(Ba)-w(Ca)/(w(Ca)+w(Fe))分布

Fig.9 Sr/Ba vs.Ca/(Ca+Fe) plot for the Chang 9 shale

图10 长9页岩w(V)/(w(V)+w(Ni))分布及w(Th)/w(U)分布

Fig.10 V/(V+Ni) vs.Th/U plot for the Chang 9 shale

图11 长9页岩EF(U)-EF(Mo)的相关关系

Fig.11 Correlation plot of EF(U) vs.EF(Mo) for the Chang 9 shale

图12 长9页岩的w(Ti)/w(Al)-w(Sr)关系

Fig.12 Plot of Ti/Al vs.Sr of the Chang 9 shale

图13 长9页岩P与Ba及S的相关关系

Fig.13 Correlation plots among P, Ba and S for the Chang 9 shale

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