Controls on organic matter accumulation in the Triassic Chang 7 lacustrine shale of the Ordos Basin, central China
Controls on organic matter accumulation in the Triassic Chang 7 lacustrine shale of the Ordos Basin, central China
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鄂尔多斯盆地三叠系长7湖相页岩有机质富集控制
DOI：
10.1016/j.coal.2017.09.015
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发表时间：
2017-10
影响因子：
5.6
通讯作者：
Wenzheng ZhangWeiwei YangLiqin Xie
中科院分区：
文献类型：
--
作者：
Wenzheng ZhangWeiwei YangLiqin Xie
鄂尔多斯盆地三叠系长7组是一种丰富的湖相烃源岩。为研究长7页岩有机质富集机理，进行了岩石学和地球化学分析。大量地球化学数据表明，富om页岩形成于淡水和半咸淡水中，而高TOC（总有机碳含量）沉积物通常不会出现这种情况。因此，长7页岩中一定存在有利于有机质富集的特殊条件。岩石学和元素地球化学表明，长7富有机质页岩富含富有机质纹层、树状黄铁矿、胶磷矿以及铁（Fe）、五氧化二磷（P2O5）、铜（Cu）、钒(V)、钼（Mo）、铀(U)等元素。高生物生产力（藻类开花）和缺氧沉积环境是OM富集的关键。随着有机碳含量的增加，Fe、P2O5、Cu、V、Mo、U元素含量增加，U/Th和V / (V + Ni)比值增大。许多地球化学数据表明，水是含氧的，而沉积物-水界面下的环境是缺氧的，因为高有机供应足以消耗氧气。综合上述地质环境和前人研究成果，认为华北陆块与扬子陆块碰撞及由此形成的青岭构造导致频繁的火山活动和热液活动对咸淡湖相页岩有机质富集具有重要作用。火山灰沉积在水环境中可能导致一些关键营养物质的增加，如铁和P2O5，这可能会提高初级生物生产力。该研究证实了热液活动的新证据——红榴石。热液活动不仅可以提供生命所需的元素，而且有利于缺氧环境的形成。长7湖相富有机质页岩的沉积可以用高生物生产力驱动模型来解释，该模型与区域构造运动导致的火山事件和热液活动有关。缺氧沉积环境有利于有机质的保存，深湖环境的缓慢沉积速率有利于有机质的富集。
The Triassic Chang 7 Formation is a rich lacustrine source rock in the Ordos Basin, central China. Petrographic and geochemical analyses were performed in order to research the mechanism of organic matter (OM) enrichment in the Chang 7 shales. Bulk geochemical data indicate that the OM-rich shales were formed in a fresh and brackish water, which is not usually the case for high TOC (Total Organic Carbon Content) sediments. Therefore, there must be some special conditions favorable for OM enrichment in Chang 7 shales...Petrography and element geochemistry show that the Chang 7 OM-rich shales are abundant in OM-enriched laminae, framboidal pyrites, collophanes, and some elements including iron (Fe), diphosphorus pentoxide (P2O5), copper (Cu), vanadium (V), molybdenum (Mo), and uranium (U). High bio-productivity (algae blooming) and anoxic depositional environments are critical for OM enrichment. As the organic carbon contents increase, the Fe, P2O5, Cu, V, Mo, and U element contents increase as well and the ratios of U/Th and V / (V + Ni) are growing. Many geochemical data demonstrate that the water was oxic, while the environment under the sediment-water interface was anoxic as a result of a high organic supply that sufficiently consumed oxygen...Taking into account the geological settings and our previous studies, we propose that the frequent volcanic events and hydrothermal activity caused by the collision of the North China landmass with the Yangtze landmass and consequential formation of the Qingling Mountains had a significant role in the OM enrichment in the fresh and brackish lacustrine shales. Deposition of volcanic ash into aqueous environments might lead to the increase of some key nutrients, such as Fe and P2O5, which might enhance primary bio-productivity. New evidence for hydrothermal activity, the reddingite, was demonstrated in this study. Not only can the hydrothermal activity provide elements necessary for life, but is also favorable for formation of anoxic settings...The deposition of the Chang 7 lacustrine OM-rich shales can be explained using the High-Bio-Productivity-Driven Model, which is related to volcanic events and hydrothermal activity as a consequence of regional tectonic movements. An anoxic depositional setting is beneficial for OM preservation and slow sedimentation rates in the deep lacustrine environments are favorable for OM enrichment.
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DOI：
10.1007/978-3-319-78527-1
发表时间：
1973
期刊：
Stable Isotope Geochemistry
影响因子：
--
作者：
J. Hoefs
通讯作者：
J. Hoefs
影响因子：
5.6
作者：
Ketris, M. P.;Yudovich, Ya. E.
通讯作者：
Yudovich, Ya. E.
影响因子：
3.5
作者：
G. Demaison;G. T. Moore
通讯作者：
G. Demaison;G. T. Moore
影响因子：
3
作者：
J. Curiale;M. Gibling
通讯作者：
J. Curiale;M. Gibling
DOI：
10.1016/j.palaeo.2004.10.009
发表时间：
2005-02
期刊：
Palaeogeography, Palaeoclimatology, Palaeoecology
影响因子：
--
作者：
P. Wignall;R. Newton;M. Brookfield
通讯作者：
P. Wignall;R. Newton;M. Brookfield