东海盆地丽水凹陷古气候和古环境对有机质富集的约束:来自古新统泥岩的元素地球化学证据

Constraints of Paleoclimate and Paleoenvironment on Organic Matter Enrichment in Lishui Sag,East China Sea Basin:Evidence from Element Geochemistry of Paleocene Mudstones

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中文摘要：为明晰东海盆地丽水凹陷古新统月桂峰组、灵峰组、明月峰组烃源岩的生烃潜力,基于24个泥岩样品主量和微量元素地球化学研究,剖析了古气候和古环境变化过程及其对有机质富集的影响.结果表明,丽水凹陷古新统沉积物相对贫碎屑组分、富自生组分,且主量和微量元素变化未受到成岩蚀变的影响.根据特征元素参数的垂向变化趋势,认为丽水凹陷古新世月桂峰组→灵峰组→明月峰组沉积时期,古气候经历了温湿→干旱→温湿、水体古盐度经历了半咸水→咸水→淡水、水体古深度经历了较深水→较浅水→浅水、水体还原程度经历了弱还原-还原→氧化→弱氧化-氧化的变化过程.古气候和古环境协同变化控制着沉积物有机质生产和保存/降解,是月桂峰组、灵峰组、明月峰组泥岩有机质富集程度存在差异性的主要原因.月桂峰组泥岩形成于温湿气候下的半深湖-深湖环境,水体生产力高,大量藻类和高等植物有机质在分层的贫氧水体介质中得以保存,导致有机质丰度较高.灵峰组泥岩形成于干旱气候下的滨浅海环境,水体生产力低,高盐度且富氧水体介质不利于藻类生存与保存,导致有机质丰度较低.明月峰组煤系泥岩形成于温湿气候下的海陆过渡环境,地表植被发育,地势平坦适宜大量高等植物有机质堆积,形成煤岩与泥岩互层分布.丽水凹陷油气勘探应围绕有机质丰度高且生烃能力强的月桂峰组生烃中心选择有效构造或岩性圈闭进行钻探.

外文摘要：In order to fully understand the hydrocarbon generation potential of the Paleocene Yueguifeng,Lingfeng and Mingyuefeng formations in the Lishui Sag,East China Sea Basin,variations in paleoclimate and paleoenvironment and their influence on organic matter enrichment are investigated through analyzing major and trace elements. Results show that the Paleocene sediments are low in terrigenous detrital components and rich in authigenic components,where major and trace elements did not experience diagenetic alteration. Multiple geochemical proxies suggest that paleoclimate during the Yueguifeng,Lingfeng and Mingyuefeng formations depositional periods was humidity,drought and humidity,respectively,while corresponding paleo-salinity was brackish water,saline water and fresh water,and paleowater depth was relatively deep water,relatively shallow water and shallow water,respectively. Water column evolved from reducing condition to oxidizing condition,and then to weak oxidizing-oxidizing condition,respectively. Organic matter productivity and preservation/degradation controlled by co-variations of paleoclimate and paleoenvironment accounted for the difference in organic matter enrichment of the Yueguifeng,Lingfeng and Mingyuefeng formations mudstones. The Yueguifeng Formation mudstone was deposited in semi-deep to deep lake environment with high productivity under warm-humid climate. Considerable planktonic algae were efficiently preserved at a stratified and dysoxic water column,resulting in high organic matter abundance. The Lingfeng Formation mudstone was developed at oxygen-enriched shallow marine environment under arid climate,which was not conducive to the reproduction and preservation of planktonic algae,giving rise to low organic matter abundance. The Mingyuefeng Formation coal-bearing mudstone was deposited in marine-continental transitional environment with low productivity under warm-humid climate,where flat terrain and considerable higher plants contributed to the development of alternated beds of coal and mudstone. The future oil and gas exploration in the Lishui Sag should focus on hydrocarbon generation center of the Yueguifeng Formation with high organic matter abundance and hydrocarbon generation capacity,and select effective structural or lithologic traps.

外文关键词：

major elementtrace elementpaleoclimatepaleoenvironmentorganic matter enrichmentLishui Sagpetroleum geology

作者：

雷闯、叶加仁、殷世艳、吴景富、静禹钱

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作者单位：

华北理工大学矿业工程学院,河北唐山 063210

中国地质大学构造与油气资源教育部重点实验室,湖北武汉 430074

中海油研究总院有限责任公司,北京 100028

中国科学院大学地球与行星科学学院,北京 100049

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关键词：

主量元素微量元素古气候古环境有机质富集丽水凹陷石油地质

基金：

国家科技重大专项子课题国家科技重大专项子课题构造与油气资源教育部重点实验室开放课题构造与油气资源教育部重点实验室开放课题唐山市科技计划项目

项目编号：

2016ZX05024-002-0032017ZX05032-001-004TPR-2022-11TPR-2022-2422130213H

出版年：

2024

DOI：

10.3799/dqkx.2023.011

地球科学

中国地质大学

地球科学

CSTPCD北大核心

影响因子：1.447

ISSN：1000-2383

年,卷(期)：2024.49(7)