黑色页岩物源研究方法、存在问题及未来展望

Methodology for research on the provenance of black shales and its problems and prospects： A case study of the Wufeng-Longmaxi formations， southern Sichuan Basin

祁灵 施振生 王红岩 周天琪 李贵中 赵萌 程辉 程自豪

Ling QI Zhensheng SHI Hongyan WANG Tianqi ZHOU Guizhong LI Meng ZHAO Hui CHENG Zihao CHENG

黑色页岩物源研究有元素地球化学方法和矿物学方法等。元素地球化学方法利用主量元素、微量元素及稀土元素判别沉积物搬运-沉积过程、母岩性质和构造背景特征，矿物学方法则通过矿物组成及含量的变化识别源区位置及其搬运路径。目前，黑色页岩物源分析仅能指出潜在物源区性质，而源区具体位置、源区分布范围以及沉积物搬运路径尚未明确。以川南地区五峰组-龙马溪组黑色页岩为例，系统分析其物源特征：①通过主成分分析识别出活动性元素（Si， Al， Ca， Fe， Ba， Ta， Th和Zr）和不活动性元素（Ti， P， Na， Mn， Yb， Lu和Tm）。②源岩成分成熟度整体偏低，经历了低-中等程度的化学风化作用和温暖湿润的气候条件。沉积分选作用和再循环作用对源岩元素特征影响微弱。③母岩主要为长英质火成岩，源区构造背景以碰撞环境为主，部分来源裂谷环境。④沉积物物源以黔中-雪峰古隆起为主，乐山-龙女寺古隆起次之。其中宜203井区、长宁地区、泸州地区以及川南东北地区的沉积物主要来源于黔中-雪峰隆起，威远地区的威207井附近沉积物主要来源于乐山-龙女寺古隆起。物源分析中影响沉积岩主量元素、微量元素、矿物组分含量分布的因素多，需结合稳定同位素、高分辨率地球化学分析技术，多指标、多学科交叉研究，大数据分析手段才能全面了解黑色页岩的物源特征。

The provenance of black shales is primarily investigated using elemental geochemistry and mineralogy. Specifically， elemental geochemical approaches are employed to analyze the process of sediment transport and deposition， as well as ascertain the nature of parent rocks and tectonic setting through the analysis of major and trace elements， and rare earth elements （REEs）. Mineralogical techniques， on the other hand， serve to identify the locations of provenance areas and pathways of sediment transport by examining variations in mineral composition. The main limitation of this methodology is that it can only determine potential provenance areas， leaving their specific locations and extents， as well as sediment transport pathways unclear. This study focuses on the provenance of black shales in the Wufeng-Longmaxi formations in the southern Sichuan Basin. The results indicate that the active elements and compounds in the shales include Si， Al， Ca， Fe， Ba， Ta， Th， and Zr and that the inactive elements and compounds encompass Ti， P， Na， Mn， Yb， Lu， and Tm. The parent rocks exhibit low compositional maturity overall， having undergone low to moderate degrees of chemical weathering and transformation under warm and humid climatic conditions. In contrast， sedimentary sorting and recycling produce minimal impacts on variations in the elemental characteristics of the parent rocks. The parent rocks consist mainly of felsic igneous rocks， with tectonic setting dominated by a collision environment， followed by a rift environment locally. The sediment originates primarily from the Qianzhong-Xuefeng paleo-uplift， succeeded by the Leshan-Longnvsi paleo-uplift. Specifically， the sediment in well block Y203， the Changning and Luzhou areas， and the northeastern part of the southern Sichuan Basin is derived principally from the Qianzhong-Xuefeng paleo-uplift， while that near well W207 in the Weiyuan area originate primarily from the Leshan-Longnvsi paleo-uplift. Provenance analysis reveals multiple factors influencing the contents of major and trace elements， and mineral components in the sediment. Therefore， to accurately determine the provenance areas of shales and their distribution， it is necessary to integrate the stable isotope analysis， high-resolution geochemical techniques， multi-index， multidisciplinary study， and big data analytics.

10.11743/ogg20250105