石油与天然气地质 ›› 2009, Vol. 30 ›› Issue (3): 343-349,336,342.doi: 10.11743/ogg20090314

• 海相碳酸盐岩 • 上一篇    下一篇

碳酸盐岩地球化学特征与沉积环境判别意义——以冀北坳陷长城系高于庄组为例

汪凯明1,2, 罗顺社1,2   

  1. 1. 长江大学, 油气资源与勘探技术教育部重点实验室, 湖北, 荆州, 434023;
    2. 长江大学, 地球科学学院, 湖北, 荆州, 434023
  • 收稿日期:2008-11-26 出版日期:2009-06-25 发布日期:2012-01-16
  • 基金项目:

    中国石油化工股份有限公司海相油气勘探前瞻性项目(GO800-06-ZS-350).

Geochemical characters of carbonates and indicative significance of sedimentary environment——an example from the Gaoyuzhuang Formation of the Changcheng System in the northern Hebei Depression

Wang Kaiming1,2, Luo Shunshe1,2   

  1. 1. Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University, Jingzhou, Hubei 434023, China;
    2. College of Geosciences, Yangtze University, Jingzhou, Hubei 434023, China
  • Received:2008-11-26 Online:2009-06-25 Published:2012-01-16

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摘要：

冀北坳陷长城系高于庄组碳酸盐岩沉积发育,可分为浅水台地和深水台盆两大相区以及5种不同类型的相带。在对碳酸盐岩样品测试结果分析的基础上,利用相关性分析对其元素和组分的富集规律及环境意义进行了探讨。分析表明,该区地球化学特征与原始沉积环境有着极为密切的关系:Ca/Mg比值在以白云岩为主的潮上蒸发环境最低,从潮间带到斜坡相逐渐升高,在以灰质白云岩为主的深水盆地相最高;Na在潮上带含量最高,潮上带超盐环境有利于白云岩化作用的发生和Na的保存;Mn和Fe在潮间带含量最高,在台盆环境较低;Al,K,V,P和Ti的含量从浅水到深水环境总体呈增加趋势,可以指示古水深及海平面的变化;Sr主要赋存于方解石矿物中,从浅水台地到深水台盆,Sr的含量和1000Sr/Ca比值呈增加趋势,潮上带和潮间带较高的Sr和1000Sr/Ca比值主要是因为潮上带和潮间带叠层石白云岩较潮下带发育,而该类岩石的主要造岩生物蓝绿藻对Sr具有相当的浓缩作用,以致Sr含量出现高值。上述特征表明碳酸盐岩的地球化学特征可作为沉积环境判别的有效标志。

关键词: 沉积环境, 地球化学特征, 碳酸盐岩, 高于庄组, 长城系, 冀北坳陷

Abstract:

The Gaoyuzhuang Formation of the Changcheng System in northern Hebei Depression is dominated by carbonates and can be roughly divided into shallow water platform and deep water platform-basin facies zones and further divided into five different facies tracts.Based on the correlation analysis of carbonate rock sample testing results,the authors of the paper discuss the enrichment mechanisms of their elements and components and environmental significance.The analysis shows that geochemical characters are closely related to the initial sedimentary environment in the study area:the Ca/Mg ratio is the lowest in supralittoral zone where dolomite is predominant,gradually increases from intertidal zone to slope zone,and reaches its highest value in deep water basin where calcite dolomite is predominant.The average Na content is the highest in supralittoral zone where it is be-neficial to dolomitization and preservation of Na.The contents of Mn and Fe are the highest in intertidal zone but relatively low in the platform-basin.The contents of trace elements as Al,K,V,P and Ti tend to increase from shallow to deep water sedimentary environment,thus could be used to indicate relatively changes of ancient water depth and sea level.Sr is mainly hosted in calcite.The average Sr content and 1000 Sr/Ca ratio tend to increase from shallow water platform to deep water platform-basin.The blue green microalgae rich in Sr is the main rock-forming organism for stromatolite dolomite,and the stromatolite dolomite is more highly developed in the supralittoral zone and intertidal zone than in subtidal zone.Thus the average Sr content and 1000 Sr/Ca ratio are relatively high in the supralittoral zone and intertidal zone.All of these indicate that geochemical characters of carbonates can be regarded as an effective indicator of sedimentary facies.

Key words: sedimentary environment, geochemical character, carbonate rock, Gaoyuzhuang Formation, Changcheng System, northern Hebei Depression

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