川西南构造复杂区龙马溪组泥页岩地球化学特征及古环境

发布时间：2018-05-12 18:15

本文选题：川西南 + 构造复杂区　；参考：《新疆石油地质》2017年04期

【摘要】：深入研究川西南构造复杂区下志留统龙马溪组泥岩沉积环境,指导区域页岩气的勘探开发,对该地区荥经县泥巴山剖面龙马溪组泥岩进行系统采样,开展了元素地球化学研究。结果表明,研究区平均化学蚀变指数为68,略低于世界页岩的平均化学蚀变指数70,Th/U为3.73,与大陆地壳Th/U平均值3.80接近,表明物源区曾遭受低—中度风化;较高含量的易水解元素、铁族元素及较低含量的亲硫元素,表明沉积水体为滨浅海环境。氧化还原指标δU,U/Th,V/Cr及Ni/Co均说明沉积水体为弱氧化环境,且越到龙马溪组沉积晚期氧化性越强。古气候指标Sr/Cu说明源区沉积期气候干旱,古盐度指标Sr/Ba,B/Ga说明研究区龙马溪组为半咸水海相沉积。研究区总有机碳含量较低,且与风化指标、氧化还原指标、古盐度古气候指标均有较好的相关性,说明总有机碳含量受沉积环境的控制。研究区龙马溪组为一套深水—浅水陆棚相烃源岩,受沉积环境及构造隆升的影响,其下段有机质品质相对较好,上段品质较差。
[Abstract]:The sedimentary environment of the Lower Silurian long MXI formation in the Lower Silurian strata in the southwestern Sichuan Province is deeply studied, and the exploration and development of the shale gas in the region is guided. The systematic sampling of the mudstone of the long Ma Xi formation in the mud mountain section of the Xing Jing County in this area has been systematically sampled and the geochemical study of the element is carried out. The results show that the average chemical alteration index of the study area is 68, slightly lower than that of the world shale. The average chemical alteration index is 70, Th/U is 3.73, which is close to the average value of the continental crust Th/U 3.80, indicating that the source area has suffered from low to moderate weathering, the high content of easily hydrolyzed elements, the iron element and the lower content of sulphur elements, indicating that the sedimentary water is the coastal shallow sea environment. The original index of delta U, U/Th, V/Cr and Ni/Co all indicate that the sedimentary water body is weak. The higher the oxidation environment is, the more advanced the late oxidation of the long Ma Creek formation is stronger. The paleoclimate index Sr/Cu shows that the climatic drought in the sedimentary period of the source area, the paleosalinity index of Sr/Ba, and the B/Ga of the long Ma Xi formation in the study area are half salty water marine sediments. The total organic carbon content of the study area is low, and the index of weathering, redox index and paleoclimate paleoclimate index are all compared. The good correlation shows that the total organic carbon content is controlled by the sedimentary environment. The Longma Creek formation in the study area is a set of deep-water shallow water shelf facies hydrocarbon source rocks, which are affected by the sedimentary environment and tectonic uplift, and the lower quality of the upper part of the organic matter is relatively good.

【作者单位】：中国地质调查局成都地质调查中心;成都理工大学地球科学学院;国土资源部沉积盆地与油气资源重点实验室;中国地质大学地球科学学院;
【基金】：国家科技重大专项(2016ZX05034004)
【分类号】：P618.13

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