The occurrence of vanadium in nature: its biogeochemical cycling and relationship with organic matter—a case study of the Early Cambrian black rocks of the Niutitang Formation, western Hunan, China

• Published in: Acta geochimica Vol. 40; no. 6; pp. 973 - 997
• Main Authors: Awan, Rizwan Sarwar, Liu, Chenglin, Yang, Shangfeng, Wu, Yuping, Zang, Qibiao, Khan, Ashar, Li, Guoxiong
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.12.2021; Springer Nature B.V; State Key Laboratory of Petroleum Resource and Prospecting,China University of Petroleum,Beijing 102249,China%Water and Power Development Authority,Lahore Pakistan; College of Geosciences,China University of Petroleum,Beijing 102249,China
• Subjects: Biogeochemical cycles; Cambrian; Carbon; Carbon content; Chlorophyll; Chlorophylls; Clay; Clay minerals; Diagenesis; Earth and Environmental Science; Earth Sciences; Economics; Enrichment; Environmental impact; Geochemistry; Heavy metals; Hydrogen sulfide; Isomorphism; Minerals; Molybdenum; Nickel; Nutrient cycles; Nutrients; Organic carbon; Organic matter; Organisms; Original Article; Oxidoreductions; Petroleum; Pigments; Porphyrins; Pyrite; Rock; Rocks; Sea level; Seawater; Sediment; Sediments; Survival; Terrestrial environments; Total organic carbon; Vanadate; Vanadium; Vanadium oxides; Vanadyl ions; Chlorophyll; Organic matter; Porphyrin; Anthropogenic; Isomerization; Vanadium
• ISSN: 2096-0956; 2365-7499
• DOI: 10.1007/s11631-021-00482-2

Vanadium in the black rocks has economic and environmental impacts. In sediments, it is broadly disseminated as a multivalent metal element mainly sensitive to redox settings. Globally in petroleum, it is considered an abundant component. Vanadium is an essential tool to determine the relationship of the Earth with extra-terrestrial bodies. In the Yangtze region, the black rocks of the Early Cambrian Niutitang Formation are highly enriched in the concentration of V, Co, Ni and Mo. These sediments are comprised of a high total organic carbon content, and the average concentration of vanadium is over 240 ppm. Here we discuss the mechanisms and conditions that were responsible for the accumulation of vanadium in these black sediments in the Yangtze region. The oxygenated ocean water is favorable for the dissolved vanadate species V(V). Therefore, in oxic ocean-water, it can be reduced by organic matters or by H 2 S to vanadyl ions V(IV), which can facilely be adsorbed to the tiny particles and finally deposit into the sediments with the settling of the particles. The presence of V 2 O 3 in the Niutitang Formation indicates the isomorphism state of vanadium existence in the clay minerals. Clays and pyrite are the most favorable mineral for vanadium enrichment. However, it is suggested the quartz of non-biogenic origin might be unfavorable for vanadium enrichment. Vanadium is mainly derived from the diagenetic transformation of its precursor (porphyrin pigments and chlorophyll) from the organism. During the Early Cambrian period, the massive transgression in the sea level created a favorable environment for organisms to survive. Additionally, the hydrothermal activities brought massive nutrient supply in the form of vanadium and other metal elements from the deep Earth. These creatures consumed the vanadium-rich nutrients, which became a part of their bodies in the form of hard and soft parts. Later on, when these organisms died and were submerged in the sediments. After the diagenetic actions, this vanadium became a part of these black sediments along with organic carbon. Therefore, these black rocks in the Yangtze region are enriched in vanadium and organic carbon. It is suggested the various processes such as adsorption, complexation, and reductions are the main factors responsible for the precipitation of dissolved vanadium into the organically rich sediments.