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Petroleum generation timing and source in the Northern Longmen Shan thrust belt, Southwest China : implications for multiple oil generation episodes and sources.

Ge, X. and Shen, C. and Selby, D. and Wang, J. and Ma, L. and Ruan, X. and Hu., S. and Mei, L. (2018) 'Petroleum generation timing and source in the Northern Longmen Shan thrust belt, Southwest China : implications for multiple oil generation episodes and sources.', AAPG bulletin., 102 (05). pp. 913-938.

Abstract

The temporal evolution of hydrocarbons (∼500 million bbl) and its relationship to the orogenic events of the Longmen Shan thrust belt have been extensively debated. The hydrocarbons occur as solid bitumen, as dykes and/or coatings within/along faults/fractures, and as present-day oil seeps. Here, utilizing organic geochemistry, we demonstrate that all of the bitumen exhibit similar organo-geochemical characteristics, and were sourced from the upper Neoproterozoic–lower Cambrian Doushantuo and Qiongzhusi Formations. In contrast, the organic geochemistry of the present-day oil seeps are distinct from that of the bitumen, and suggest that the source is the Permian Dalong Formation. Bitumen Re-Os data indicate that the upper Neoproterozoic–lower Cambrian Doushantuo and Qiongzhusi Formations underwent two temporally distinct oil-generation events; initial oil generation occurred during the Late Cambrian/Early Ordovician prior to the Caledonian orogeny, and secondly during the Jurassic (∼165 Ma) coinciding with the Indosinian-Yanshan orogenies. In contrast, the Re-Os data of the present-day oil seeps are too similar to yield a meaningful age, although the source is considered to have undergone hydrocarbon maturation between the Triassic and Jurassic. The temporal hydrocarbon evolution in the Longmen Shan thrust belt also provides an understanding of the hydrocarbon evolution and future exploration of the adjacent petroliferous Sichuan Basin.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1306/0711171623017125
Date accepted:11 July 2017
Date deposited:07 June 2017
Date of first online publication:May 2018
Date first made open access:01 May 2019

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