羌塘盆地南部古油藏带布曲组碳酸盐岩稀土元素特征及意义

发布时间：2018-06-17 01:56

本文选题：稀土元素 + 沉积环境　；参考：《石油实验地质》2017年05期

【摘要】：在羌塘盆地南部古油藏带布曲组碳酸盐岩的详细岩石学分析基础上,研究不同类型碳酸盐岩的稀土元素特征,结果表明:(1)研究区碳酸盐岩包括灰岩、泥—微晶白云岩、(残余)颗粒白云岩、晶粒白云岩及鞍形白云岩;(2)各类碳酸盐岩均具有较低的稀土元素总量,能够指示沉积或成岩流体的性质,部分鞍形白云岩样品稀土元素总量高于灰岩,预示着可能有外来流体的加入;(3)不同类型碳酸盐岩稀土总量具有差别,但经太平洋表层海水标准化后,具有相似的稀土元素配分模式,La_N/Yb_N平均值为2.86,轻微的轻稀土富集和重稀土亏损,随着白云石化程度的增加,轻稀土富集程度变弱,δCe正异常(平均值2.94)和δEu正异常(平均值1.43),这些特征说明布曲组碳酸盐岩沉积于氧化性质的水体中,白云石化流体主要为同期海源地层水,但在烃类充注以后成岩环境变为还原环境,受早白垩世末期拉萨地体与羌塘地块剪刀式碰撞,研究区布曲组地层中有大气淡水加入,再次受到新生代构造热事件影响,形成鞍形白云岩,构造热事件为Eu~(2+)富集提供温度条件。
[Abstract]:On the basis of detailed petrological analysis of carbonate rocks of Buqu formation in the paleoreservoir belt of southern Qiangtang Basin, the REE characteristics of different types of carbonate rocks are studied. The results show that the carbonate rocks in the study area include limestone. The total amount of rare earth elements in all carbonate rocks is low and can indicate the properties of sedimentary or diagenetic fluids, such as mud-microcrystalline dolomite (residual) granular dolomite, grain dolomite and saddle dolomite. The total amount of rare earth elements in some saddle dolomite samples is higher than that in limestone, indicating that the total amount of rare earth elements in different types of carbonate rocks may be different with the addition of foreign fluids. With a similar REE partition model, the average value of La / Yb\ + -\%\ +\%\ $\ {# * $}\%\ The enrichment degree of light rare earth is weakened, 未 ce positive anomaly (average value 2.94) and 未 EU positive anomaly (average value 1.43). These characteristics indicate that carbonate rock of Buqu formation is deposited in oxidized water body, and dolomitization fluid is mainly sea source formation water in the same period. However, after hydrocarbon filling, the diagenetic environment changed into a reductive environment and was subjected to scissors collision between Lhasa terrane and Qiangtang block at the end of early Cretaceous. The formation of Buqu formation in the study area was joined by atmospheric fresh water, which was again affected by Cenozoic tectonic heat events. The formation of saddle dolomite and tectonic thermal events provide the temperature conditions for EU ~ (2) ~ (2) enrichment.
【作者单位】：中国地质调查局成都地质调查中心国土资源部沉积盆地与油气资源重点实验室;中国地质调查局成都地质调查中心沉积与能源地质研究室;中国地质大学(武汉)地球科学学院;
【基金】：基础性公益性油气地质调查项目(121201010000161110) 国土资源调查项目(1212011221114) 国家“十二五”重大科技专项(2011ZX05004-001)联合资助
【分类号】：P618.13

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