Clay mineral of different lithofacies in a continental shallow water delta: Insights from paleoclimate and diagenesis

IF 2.7 2区 地球科学 Q1 GEOLOGY
Shaoyun Chen , Yongqiang Yang , Zaixing Jiang , Xiaojuan Wang , Longwei Qiu , Yerejiepu Habulashenmu
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引用次数: 0

Abstract

Clay minerals in clastic sediments carry important geological information, with their composition and variations reflecting key geological processes. This study investigates the differential clay mineral assemblages among lithofacies within the Middle Jurassic continental shallow-water delta system of the Sichuan Basin, China. Integrated geochemical and XRD analyses demonstrate the significant influence of paleoclimate-driven weathering and diagenetic alteration on clay mineral assemblages. The invariant geochemical characteristics (such as Ti/Al) across different mudstone confirm a uniform provenance, establishing paleoclimate-controlled weathering processes as the principal determinant of clay mineral composition, with negligible provenance influence. Chemical weathering intensity, controlled by the depositional paleoclimate, is a primary factor influencing clay mineral composition in mudstones. In warm, humid climates, abundant rainfall and strong chemical weathering lead to kaolinite enrichment and smectite depletion in black shale facies. Conversely, in cooler, drier climates, physical weathering dominates, resulting in significant illite formation in red mudstone and paleosol facies. In sandstone facies, clay minerals are controlled by diagenetic fluid composition and flux. Chlorite content is related to the primary permeability of the sandstone, while illite content is influenced by K+ concentration in diagenetic fluids, with stronger illite enrichment in areas of intense feldspar dissolution. The smectite-to-illite transformation is common in both sandstone and mudstone facies, with its extent influenced by the openness of the diagenetic system and K+ availability. In humid conditions, feldspar dissolution in an open system leads to K+ advection into sandstone, reducing smectite-to-illite transformation in mudstones. In semi-arid conditions, feldspar dissolution occurs in closed systems during burial, with K+ diffusing into mudstones, promoting greater illitization in mudstones than in sandstones. This study provides insights into how paleoclimate and diagenesis control clay mineral transformations in sedimentary rocks.
大陆浅水三角洲不同岩性的粘土矿物:从古气候和成岩作用中获得的启示
碎屑沉积物中的粘土矿物携带着重要的地质信息,其组成和变化反映了关键的地质过程。研究了四川盆地中侏罗统陆相浅水三角洲体系中不同岩相粘土矿物组合的差异性。综合地球化学和XRD分析表明,古气候驱动的风化和成岩蚀变对粘土矿物组合有显著影响。不同泥岩的地球化学特征(如Ti/Al)的不变证实了一个统一的物源,建立了古气候控制的风化过程作为粘土矿物组成的主要决定因素,而物源的影响可以忽略不计。化学风化强度是影响泥岩粘土矿物组成的主要因素,受沉积古气候控制。在温暖湿润的气候条件下,丰富的降雨和强烈的化学风化作用导致黑色页岩相高岭石富集和蒙脱石亏缺。相反,在较凉爽、干燥的气候条件下,物理风化作用占主导地位,导致红泥岩和古土壤相中形成大量伊利石。在砂岩相中,粘土矿物受成岩流体组成和通量的控制。绿泥石含量与砂岩的原生渗透率有关,伊利石含量受成岩流体中K+浓度的影响,在长石溶蚀强烈的地区伊利石富集程度较强。蒙脱石向伊利石转化在砂岩相和泥岩相中都很常见,其程度受成岩系统的开放性和K+有效性的影响。在潮湿条件下,开放体系中的长石溶蚀导致K+平流进入砂岩,减少泥岩中蒙脱石向伊利石的转化。在半干旱条件下,长石在埋藏过程中以封闭体系溶解,K+扩散到泥岩中,泥岩的钝化作用大于砂岩。该研究对古气候和成岩作用如何控制沉积岩中粘土矿物的转化提供了新的认识。
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来源期刊
Sedimentary Geology
Sedimentary Geology 地学-地质学
CiteScore
5.10
自引率
7.10%
发文量
133
审稿时长
32 days
期刊介绍: Sedimentary Geology is a journal that rapidly publishes high quality, original research and review papers that cover all aspects of sediments and sedimentary rocks at all spatial and temporal scales. Submitted papers must make a significant contribution to the field of study and must place the research in a broad context, so that it is of interest to the diverse, international readership of the journal. Papers that are largely descriptive in nature, of limited scope or local geographical significance, or based on limited data will not be considered for publication.
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