| 湘中涟源凹陷上泥盆统佘田桥组页岩地球化学特征及有机质富集机理 |
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| 引用本文： | 田巍,王传尚,白云山,李培军.湘中涟源凹陷上泥盆统佘田桥组页岩地球化学特征及有机质富集机理[J].地球科学,2019,44(11):3794-3811. |
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| 作者姓名： | 田巍 王传尚 白云山 李培军 |
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| 作者单位： | 中国地质调查局武汉地质调查中心, 湖北武汉 430205 |
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| 基金项目： | 国家科技重大专项2016ZX05034001-002中国地质调查局地质调查项目DD20160179中国地质调查局地质调查项目DD20190781 |
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| 摘 要： | 上泥盆统佘田桥组是湘中地区页岩气勘探的重要层系之一.为了探讨湘中地区涟源凹陷上泥盆统佘田桥组黑色泥页岩有机质富集机理，系统采集了区内湘新地3井佘田桥组20个泥页岩岩心样品，开展有机碳含量、主量元素、微量元素以及稀土元素等地球化学特征测试，分析佘田桥组页岩的古盐度、古气候、古氧化还原条件和古生产力等古沉积环境.结果表明:佘田桥组底部层段有机碳含量较高（1.28%~2.68%），平均值为1.69%.页岩主要成分为SiO2（50.27%）、Al2O3（13.66%）、CaO（11.55%）.微量元素Rb、Sr和Zr富集而Co、Mo、Sc和Hf亏损.Sr/Ba、化学蚀变指数（CIA）、Th/U、V/Sc、V/Cr、δU比值表明佘田桥组富有机质页岩段沉积环境为淡水-半咸水、干旱的贫氧-次富氧环境，贫有机质页岩段为咸水、干旱-半干旱的富氧环境.结合区域层序地层特征，综合对比佘田桥组有机碳含量（TOC）与古氧化还原条件、古生产力条件的相关性，揭示出涟源凹陷佘田桥组富有机质页岩段有机质富集的主控因素为古氧化还原环境，而贫有机质页岩段有机质主要来源于陆源供给.
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| 关 键 词： | 佘田桥组泥页岩 沉积环境 有机质富集 涟源凹陷 油气地质 地球化学 |
| 收稿时间： | 2019-06-28 |
Shale Geochemical Characteristics and Enrichment Mechanism of Organic Matter of the Upper Devonian Shetianqiao Formation Shale in Lianyuan Sag,Central Hunan |
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| Abstract: | The Upper Devonian Shetianqiao Formation shale is one of the most important shale gas exploration beds in Lianyuan sag of Xiangzhong depression. In order to discuss the organic matter enrichment mechanism of the Shetianqiao Formation shale, 20 shale core samples collected systematically from Well XXD-3 were chosen.The organic carbon content, major, trace and rare earth elements were analyzed to investigate the paleo-salinity, paleo-climate, paleo-redox and paleo-productivity characteristics of the Upper Devonian sedimentary environment in Lianyuan sag of Xiangzhong depression. Research illustrates that the organic carbon content is higher (1.28%-2.68%) at the bottom of Shetianqiao Formation, with an average of 1.69%. Major components of shale include SiO2(50.27%), Al2O3(13.66%), CaO (11.55%). Trace elements Rb, Sr and Zr are enriched while Co, Mo, Sc and Hf are depleted. The ratio of Sr/Ba, CIA, Th/U, V/Sc, V/Cr, and δU suggest that Shetianqiao Formation organic-rich shales should be deposited in fresh-brackish water, arid climate and suboxic to anoxic environment, while organic-poor shales were mostly deposited in salt water, arid to semi-arid climate and oxygen-enriched environment. Combining with the regional sequence stratigraphic characteristics, comprehensive comparison of the correlation among organic carbon content (TOC), paleo-redox and paleo-productivity conditions, it is revealed that the main controlling factors of organic matter enrichment of Shetianqiao Formation organic-rich shales are redox environment. The changes in organic matter content of Shetianqiao Formation organic-poor shales are predominantly controlled by terrigenous supply. |
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