摘要
以电子探针分析为主要研究方法,结合白云岩岩石学特征对四川盆地东南地区林1井上震旦统灯影组热液白云岩进行了研究。其特征表现为基质白云岩晶体较小,中-巨晶鞍形白云石充填溶蚀孔洞和裂缝。鞍形白云石晶体上常发育数条由内到外铁元素含量依次降低的明亮条带,表明其受到多期次的深部热液侵入的影响。通过对电子探针样品的分析,发现在热液白云石形成过程中,Mg^(2+)取代Ca^(2+)的同时伴随Fe^(2+)、Mn^(2+)、Sr^(2+)参与结晶。热液白云岩刚开始沉淀时,热液中的Fe^(2+)与Mn^(2+)进入原岩,随着Mg离子大量取代Ca^(2+),使Fe^(2+)与Mn^(2+)进入率下降;或是前期热液白云石的沉淀大量消耗了热液中的金属Fe^(2+)和Mn^(2+),导致金属离子供应不足,造成沉淀过程中Fe^(2+)与Mn^(2+)含量随着Mg^(2+)含量增加而减少,反映着热液白云岩化过程的流体改造进程。
Taking the electronic microprobe analysis as the main research method, comprehensive petrological characteris- tics of hydrothermal dolomite are studied in detail on the Permian Sinian Dengying Formation of the Well Lin-1 in the southeastern Sichuan Basin. The Dengying Formation dolomite is characterized by crystallitic matrix with medium-coarse grain sized saddle dolomite filled within pores, cavities and cracks. The saddle dolomite crystals contain several to more than ten growth strips with iron content decrease from the inner outside, which indicates that the growth of the saddle dolo- mite was influenced by multiple inputs of deep hydrothermal fluids. The results of the electron probe analysis suggest that Mg^2＋ could replace Ca^2＋, accompanying with the participation of Fe^2＋ , Mn^2＋ and Sr^2＋ in the formation of hydrothermal dolomite. At the beginning of the hydrothermal dolomite formation, Fe^2＋ and Mn〉 in the hydrothermal fluids could replace Ca^2＋ in the original rock. When a large amount of Mg^2＋ replaced Ca^2＋, resulting in the declining rate of Fe^2＋and Mn〉 into the dulomite. Thus, the early hydrothermal dolomite consumed a large number of Fe^2＋ and Mn^2＋ from the fluids, resulting in an inadequate supply of metal ions, e.g., Fe^2＋, Mn^2＋, etc., and in turn decrease Fe^2＋ and Mn^2＋ content with increasing Mg^2＋.
出处
《矿物岩石地球化学通报》
CSCD
北大核心
2017年第2期289-298,共10页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家自然科学基金资助项目(41572085
41272131)
关键词
四川盆地
热液白云岩
电子探针分析
震旦系
灯影组
Sichuan Basin
hydrothermal dolomite
electron microprobe analysis
Sinian
Dengying Formation
