REE models for the discrim ination of fluids in the formation and evolution of dolom ite reservoirs

doi:10.11743/ogg20100614

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REE models for the discrim ination of fluids in the formation and evolution of dolom ite reservoirs
Vol. 31, Issue 6, Pages: 810-818(2010)
Online First：28 December 2010，

Published：2010
DOI： 10.11743/ogg20100614
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DOI：

REE models for the discrim ination of fluids in the formation and evolution of dolom ite reservoirs[J]. 2010, 31(6): 810-818. DOI： 10.11743/ogg20100614.

摘要

综合近年来应用稀土元素研究白云岩储层流体作用特征的结果，结合对四川盆地和塔里木盆地典型样品稀土元素特征的分析，提出了辨别不同流体来源及作用特点的主要模式:1）受成岩流体改造较弱的白云岩依然显示海水来源的稀土元素模式。全岩稀土元素总量低（一般小于20μg/g），显著的正Ce异常，轻稀土元素富集，重稀土元素配分曲线较为平坦。2）大气降水淋滤-渗滤模式。全岩稀土元素含量低于正常白云岩，Ce正异常显著降低，甚至出现负Ce异常，其中淡水淋滤成因的方解石脉具最低的稀土元素含量。3）成岩-成烃流体作用模式。全岩稀土元素含量稍微降低，但配分模式保持与海水类似，与之相关的白云石次生加大边具有较高的稀土元素含量和Ce SWN 值，成岩流体方解石脉的稀土元素和Ce SWN 值明显高于围岩，但两者都显示了海水来源特征。4）热液作用模式。稀土元素含量降低，出现正Eu异常，稀土元素配分曲线起伏不平。

Abstract

Based on studies of fluids in formation and evolution of dolom ite reservoirs with REE in recent years and in combination with REE analyses of typical samples from the Sichuan and Tarim basins，fourmajor REE models are presented to identify the sources and behavior characteristics of fluids.（1）REE modelwith dolomites weakly altered by diagenetic fluids still showing seawater origin.It is characterized by lowwhole-rock gross REE content（generally<20μg/g），significant positive Ce anomaly，LREE enrichment，and relatively flat HREE distribution patterns;（2）Meteoric water leaching-percolation REE model.It features in whole-rock REE content being lower than thatofnormal dolom ite，positive Ce anomaly significantly lowering and even turning into negative Ce anomaly，and calcite veins ofmeteoric water leaching origin being the lowest in REE content;（3）Diagenetic fluid-hydrocarbon fluids REE model.It is characterized by slightly lowering whole-rock REE content but sim ilar distribution patterns as seawater.The associated dolom ite overgrowth has relatively higherREE content and Ce SWN value.Calcite veins ofdiagenetic fluid origin have significanthigherREE content and Ce SWN value than thatofhost rock.However both of them show the characteristic of seawater origin;（4）Hydrothermal alteration model.It features in lowerREE content，positive Eu anomaly and undulating REE distribution patterns.