Anthraxolite Evolution and Vanadium Enrichment Mechanism in the Tanjianshan Group, Upper Ordovician in the Northern Qaid
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Original Paper
Anthraxolite Evolution and Vanadium Enrichment Mechanism in the Tanjianshan Group, Upper Ordovician in the Northern Qaidam Basin Chenglin Liu ,1,2,5 Hongwei Gong,1,2 Chao Dun,1,2 Xiaohu Wang,3 Yuanyuan Yang,3 Chao Tong,4 and Zhihui Zhang1,2 Received 14 March 2019; accepted 13 August 2019
Earlier researchers have examined the interaction between organic matter (OM) and metals, but the paragenesis of anthraxolite and mechanism enrichment of vanadium (V) need further study. Our recent geological field survey discovered that anthraxolite contains a substantial amount of V in the Member ‘‘a’’ of the Tanjianshan Group, Upper Ordovician in the northern margin of the Qaidam Basin. Different organic geochemical studies (fluid inclusions, zircon U–Pb dating, and petrochemistry) were conducted to examine the origin and evolution of anthraxolite, as well as the enrichment of V. The extractable organic matter (EOM) content of anthraxolite is low, while it contains a high amount of non-hydrocarbon and asphaltene. Anthraxolite is over-mature with its equivalent vitrinite reflectance being up to 4.9%. Anthraxolite is sourced from mudstone of Member ‘‘a’’ of the Tanjianshan Group. There were two hydrocarbon charging phases: (i) Late Devonian; and (ii) Carboniferous. Multiple magmatic thermal events took place after the Late Devonian period, resulting in hydrocarbon fluid cracking, metamorphism, and finally the formation of anthraxolite. Marine hot water deposition was irrelevant to enrichment of V. It is inferred that V originated during biological and biochemical processes, then migrated and accumulated with hydrocarbon formation and evolution, and finally enriched in anthraxolite. KEY WORDS: Anthraxolite, Biogeochemical mineralization process, Vanadium, Organic matter, Qaidam Basin.
INTRODUCTION
1
College of Geosciences, China University of Petroleum, Beijing 102249, China. 2 State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China. 3 Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China. 4 China National Offshore Oil Corp, Gas & Power Group, Beijing 100028, China. 5 To whom correspondence should be addressed; e-mail: [email protected]
Researchers have been investigating the original relationship between organic matter (OM) and metallic elements for a long time (Anderson 1991; Spirakis and Heyl 1993; Zhou et al. 2006; Chen et al. 2008; Gu et al. 2010; Li et al. 2013; Fang et al. 2016; Sun 2016; Yi and Yi 2017). During our geological field survey in the northern margin of the Qaidam Basin, we found that anthraxolite in the Tanjianshan Group of the Upper Ordovician contains more vanadium (V) than that in the crust. What roles does V play in the process of petroleum generation from
Ó 2019 International Association for Mathematical Geosciences
C. Liu et al. hydrocarbon source rocks? And, how does it enrich during the evolution of light oil to heavy oil, bitumen, and anthraxolite, a highly thermal evolution product of OM? Bo
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