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微生物白云石模式评述

作    者:杨华,王宝清
单    位:中国石油长庆油田分公司
基金项目:“十一五”国家重大专项(编号:2008ZX05004-002)资助
摘    要:
Vasconcelos等在实验室模拟巴西Lagoa Vermelha 潟湖条件,成功地沉淀出白云石,由此提出了微生物白云 石模式。该模式在南澳大利亚、阿拉伯海湾、西印度外陆棚边缘以及意大利南部等地区得到了不同研究者的肯定,我国鄂尔多斯盆地奥陶系马家沟组五段白云岩也可以解释为微生物成因。此模式对白云石形成机理的研究具有突破性的意义。当硫酸盐还原细菌利用SO42-时,也吸收了Mg2+,因为Mg2+与SO42-形成了很强的离子对。微生物由于其新陈代谢作用利用SO42-而克服了动力障碍,同时从离子对中释放出Mg2+ 。在白云石形成的化学反应中,微生物因素把硫酸根离子从反应的抑制剂变成了催化剂。白云石一旦成核,就会在埋藏过程中长大。尽管不是所有的白云石都可以用微生物白云石模式来解释,但野外研究和模拟实验都证明这一模式是有说服力和生命力的。
关键词:白云石化作用;白云岩;成岩机理;微生物作用;成因模式;巴西;鄂尔多斯盆地

Microbial Dolomite Models: An Overview

Author's Name: Yang Hua, Wang Baoqing
Institution: PetroChina Changqing Oilfield Company
Abstract:
Since discovery of dolomite in modern environments in 1960s, many dolomite models have been proposed but some long perplexed problems for the origin of dolomite formation has not been resolved. One of them is the inability to precipitate dolomite in the laboratory under conditions to replicate it that are found in modern natural environments. At the end of 20th century, Vasconcelos et al. simulated environmental conditions found in Lagoa Vermelha lagoon, Brazil, and successfully precipitated dolomite in the laboratory, which led to the formulation of the microbial model for dolomite formation. Many researchers have affirmed this model through researches on dolomite in South Australia, Arabian Gulf, outer shelf margin off western India, southern Italy and other places. The dolomite from Ordovician Majiagou Formation 5 Member in Ordos basin can be also considered as microbial origin. This microbial dolomite model may be significant in the research on mechanism of dolomite formation. As sulfate-reducing bacteria use the SO4 2- ion, they will utilize the accompanying Mg2+ ions inside their cells, because they form strong ion pairs. Uusing SO4 2- ions and release Mg2+ ions, microbes overcome the kinetic problems for their metabolism. The microbial factor converts sulfate ions from an inhibitor to a catalyst in chemical reactions of dolomite formation. Once dolomite is nucleated, the crystals continue to grow in the burial processes. Although the microbial dolomite model can not be used to explain every type of dolomite, both researches on modern dolomite environments and simulated experiments demonstrate that the model is convictive and viable.
Keywords: Dolomitization; Dolostone; Diagenesis mechanism; Microbiogenesis; Model; Brazil; Ordos Basin
投稿时间:2012-03-06  
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