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| 基金项目：国家自然科学基金项目“基于深度学习地震多属性预测碳酸盐岩沉积相展布”（42172175），四川省自然科学基金青年基金项目（2023NSFSC0759） |
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| 摘要： |
| 川东南地区志留系石牛栏组作为四川盆地油气勘探的重要层系，其沉积古环境特征、古构造背景解析及物源区的重建具有重要的地质意义。基于岩石学、矿物学与地球化学等分析方法，探讨四川盆地志留系石牛栏组的古风化特征、古气候特征、物源属性及构造背景。古风化指数(CIA)垂向演化结果表明，研究区沉积物源区经历了弱—中等化学风化作用，石牛栏组底部CIA值持续降低，向上至顶部逐渐恢复较高值，反映出气候逐渐变暖、冰川作用消退的过程，揭示了志留纪早期气候由冷到暖的变化，完整记录了早志留世冰期—间冰期的转换过程；A-CN-K三角图及TiO2-Al2O3、TiO2-Zr、La/Th-Hf二元图显示，川东南岩石的物源主要为长英质火成岩，来自黔中—雪峰隆起的混合源区，稀土元素的REE-La/Yb图解也表明物源区受雪峰隆起影响，源岩主要为沉积岩与碱性玄武岩和花岗岩的混合区；判别函数图、La-Th-Sc和Th-Sc-Zr/10三角图显示，石牛栏组碎屑沉积物形成于活动大陆边缘构造背景；古环境重建结果表明，早志留世赫兰特冰期冰川作用与区域构造活动协同控制了石牛栏组碳酸盐岩沉积体系。 |
| 关键词：地球化学特征 构造-沉积演化 石牛栏组 下志留统 川东南地区 |
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| Abstract: |
| The Silurian Shiniulan Formation in the southeastern Sichuan Basin is a significant stratigraphic unit for oil and gas exploration. Understanding its paleo-sedimentary environment, paleo-tectonic setting, and provenance reconstruction holds considerable geological importance. Based on analytical methods including petrology, mineralogy, and geochemistry, this study investigates the paleo weathering characteristics, paleo climatic features, provenance attributes, and tectonic setting of the Shiniulan Formation in the Sichuan Basin. The research indicates that the vertical evolution of the Chemical Index of Alteration (CIA) reveals that the source area sediments underwent weak to moderate chemical weathering. The CIA values continuously decreased at the base of the Shiniulan Formation and gradually recovered to higher values towards the top, reflecting a process of gradual warming and glacial retreat. This records the Early Silurian climatic transition from cold to warm, comprehensively documenting the shift from glacial to interglacial periods in the Early Silurian. The A-CN-K ternary diagram, along with TiO2-Al2O3, TiO2-Zr, and La/Th-Hf bivariate diagrams, suggests that the rocks in southeastern Sichuan were primarily derived from felsic igneous rocks, originating from a mixed source area within the Qianzhong-Xuefeng Uplift. The REE-La/Yb diagram for rare earth elements also indicates the provenance was influenced by the Xuefeng Uplift, with source rocks being a mixture of sedimentary rocks, alkaline basalts, and granites. Discriminant function diagrams and the La-Th-Sc and Th-Sc-Zr/10 ternary plots demonstrate that the clastic sediments of the Shiniulan Formation were formed in an active continental margin tectonic setting. The paleo-environmental reconstruction indicates that the Early Silurian Hirnantian glaciation, coupled with regional tectonic activity, jointly controlled the carbonate sedimentary system of the Shiniulan Formation. |
| Keywords:geochemical characteristic tectono sedimentary evolution Shiniulan Formation Lower Silurian southeastern Sichuan Basin |
| 袁龙， 田亚铭， 李文杰， 等.川东南地区下志留统石牛栏组元素地球化学特征及其古环境意义[J].地质学刊,2026,50(1):7-22 |
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