摘要:基于钻井岩心资料，对贵州岑巩区块下寒武统变马冲组黑色页岩取心段进行系统采样、主微量元素测试及沉积地球化学分析。研究结果表明：1）古盐度判别指标Sr/Ba及Rb/K分布显示，下寒武统变马冲组黑色页岩沉积时期属局限海背景下的半（微）咸水—淡水相沉积，变马冲组一段—三段古盐度垂向变化不大；Sr丰度与碳酸盐矿物含量之间具明显的响应关系；2）古氧相指标V/Cr、Ni/Co、U/Th比值及δU值分布表明变马冲组黑色页岩沉积为氧化为主、间或贫氧的环境，V/（V+Ni）比值判别偏于还原环境；3）古气候判别参数“C”、Sr/Cu及SiO2/Al2O3比值表明该套页岩沉积期主体属温湿气候，利于有机质形成；4）古水深及离岸远近判别参数Rb/Zr、Sr/Ba比值分布显示水体较浅、离岸较近的沉积特征，结合物源及沉积构造背景指征参数分析，变马冲组黑色页岩属大陆边缘离岸较近、水体较浅的陆源碎屑沉积。此研究认识揭示了岑巩区块下寒武统沉积环境的演化，进而为该套黑色页岩的有机质富集机理及页岩气选区评价提供一定的地质依据。
关键词: 地球化学/
沉积环境/
黑色页岩/
变马冲组/
贵州岑巩
Abstract:Based on the systematic core sampling, major and trace elements testing and sedimentarygeochemical analysis have been carried out to analyze the sedimentary environment characteristicsof the Bianmachong Formation of Lower Cambrian in the Cen′gong block, Guizhou Province. Theresults show that the black shale of the Bianmachong Formation was deposited in a semi.（micro） brackish water.fresh water environment under the background of restricted sea indicated by thepaleosalinity discriminant indicators of Sr/Ba and Rb/K ratio. There is little change in the verticalsalinity of the first and third segment of the Bianmachong Formation, and an obvious respondingrelationship between the Sr content and carbonate minerals content. The distribution of V/Cr,Ni/Co, U/Th ratio and δU value of the paleo.redox indicators indicates that the black shale wasdeposited in an environmentdominated by oxidation and sometimesdysoxic condition.The V/（V+Ni） ratio indicates an reduction environment. The climatic index“C”, Sr/Cu and SiO2/Al2O3 ratio of paleoclimatological distinguishing parameters indicate that the climate is in a warm and humidcondition which is conducive to the formation of organic matter. The Rb/Zr and Sr/Ba ratio of thepalaeobathymetric and offshore distance indicators show that the shale is deposited in a shallowwater and offshore environment. Combining with the analysis of provenance and tectonicbackground, the black shale of the Bianmachong Formation was mainly deposited in relativelyshallow water shelf in the continental margin setting. This research has revealed the dynamicsedimentary environment evolution of the Lower Cambrian in the Cen′gong block, and can providea certain geological basis for the analysis of organic matter enrichment mechanism and theevaluation of shale gas block.
Key words:Geochemistry/
Sedimentary environment/
Black shale/
Bianmachong Formation/
Guizhou Cen′gong
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