塔里木盆地中央隆起区上寒武统—下奥陶统白云岩地球化学特征及白云石化流体演化规律

发布时间：2018-04-03 11:23

本文选题：塔里木盆地　切入点：上寒武统—下奥陶统　出处：《古地理学报》2016年04期

【摘要】：以详细的岩石学研究为基础,综合利用碳、氧、锶同位素等地球化学资料,深入分析了塔里木盆地中央隆起区上寒武统—下奥陶统白云石化流体演化规律以及白云岩成因机制。结果表明,上寒武统白云岩主要由泥晶—粉晶白云岩、微生物白云岩和(残余)颗粒白云岩等原始结构保留较好的白云岩构成,其C、Sr同位素与同期海水相近,O同位素值偏正,属于同生/准同生期与轻微蒸发海水有关的白云石化的产物;下奥陶统白云岩以细晶自形—半自形白云石为主,原始结构保留差,其C、Sr同位素与同期海水近似,但O同位素值略微偏负,主要为浅埋藏期白云石化的产物。部分早期白云岩在中—深埋藏过程中受埋藏重结晶和构造—热液白云石化的影响,形成细晶—粗晶他形白云岩和缝洞鞍形白云石充填物,该阶段白云石化流体主要来自于地层内封存的海源流体、深部热液以及蒸发岩层间热卤水,多期多源流体的共同作用导致该类白云岩具有较宽的Sr同位素组成和明显负偏的O同位素值。总体上,研究区白云岩具有早期形成(近地表到浅埋藏期大规模交代)、中期加强(中—深埋藏期部分重结晶)、晚期改造(热液局部调整)的整体演化趋势。
[Abstract]:On the basis of detailed petrological studies and using the geochemical data of carbon, oxygen and strontium isotopes, the evolution of dolomitization fluid and the genetic mechanism of dolomite in the central uplift area of the Tarim Basin are analyzed.The results show that the upper Cambrian dolomite is mainly composed of dolomite, microbe dolomite and (residual) granular dolomite, and their C ~ (+) Sr isotopes are slightly positive than those of seawater in the same period, and the results show that the upper Cambrian dolostone is mainly composed of mudstone, microorganism dolomite and (residual) granular dolomite.The lower Ordovician dolomite is dominated by fine-grained and semi-automorphic dolomite with poor original structure, and its C ~ (+) Sr isotopes are similar to those of the corresponding seawater, and belong to the dolomitization products of the syntectic / quasi-syntectic period, and the lower Ordovician dolomite is mainly fine-grained and semi-automorphic dolomite.But the value of O isotope is slightly negative, which is mainly the product of dolomitization in shallow burial period.Some of the early dolomites were affected by buried recrystallization and tectonic-hydrothermal dolomitization during the middle to deep burial, resulting in fine grained coarse allotropic dolomite and saddle-shaped dolomite fillings in fracture cavities.In this stage, dolomitization fluid mainly comes from sea source fluid, deep hydrothermal fluid and thermal brine between evaporating rock layers.The interaction of multi-period and multi-source fluids leads to a wide Sr isotopic composition and an obvious negative bias of O isotopic value in this kind of dolomite.In general, the dolomite in the study area has the overall evolution trend of early formation (from near surface to shallow burial period, large scale metasomatism from near surface to shallow burial period), intermediate strengthening (partial recrystallization in medium-deep burial period, late reformation (local adjustment of hydrothermal solution)).
【作者单位】：中国石油勘探开发研究院;中国石油塔里木油田公司勘探开发研究院;
【基金】：国家科技重大专项(编号:2011ZX05004) 中国石油天然气股份有限公司重大科技专项(编号:2014E-3201)共同资助~~
【分类号】：P618.13;P534

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