DOI:10.19762/j.cnki.dizhixuebao.2021102
 
The relationship between environment and geochemical characteristics of black rock series of Lower Cambrian in northern Guizhou
Author NameAffiliationE-mail
FU Yong 1) College of Resources and Environmental Engineering, Guizhou University, Guiyang, 550025 byez1225@126.com 
ZHOU Wenxi 1) College of Resources and Environmental Engineering, Guizhou University, Guiyang, 5500252) Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, Beijing, 100083  
WANG Huajian 4) 102 Geological Brigade of Guizhou Bureau of Geology and Mineral, Zunyi,Guizhou, 563003  
QIAO Wenlang 2) Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, Beijing, 100083  
YE Yuntao 2) Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, Beijing, 1000833) Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing, 100871  
JIANG Ran 1) College of Resources and Environmental Engineering, Guizhou University, Guiyang, 550025  
WANG Xiaomei 2) Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, Beijing, 100083  
SU Jin 2) Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, Beijing, 100083  
LI Di 1) College of Resources and Environmental Engineering, Guizhou University, Guiyang, 5500252) Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, Beijing, 100083  
XIA Peng 1) College of Resources and Environmental Engineering, Guizhou University, Guiyang, 550025  
Abstract:The lower Cambrian black rock series are widely distributed in North China, South China, and Tarim basin, but the controlling factors and distribution characteristics of organic- rich mudstone and shale are still being debated. In this study, we collected samples of the Niutitang Formation (or its time- equivalent) from eight typical profiles of different sedimentary environments and carried out integrated geochemical analyses. The results suggest that different sedimentary environments are characterized by different redox conditions during the early Cambrian. Sediment lithologies of the inner platform are mainly black shales with some thinly bedded phosphatic rocks and cherts or phosphate/chert nodules. The black shales are thick and have high abundance of organic matter. Trace elements (V, Ni, Mo and U) of black shale from the inner platform facies are significantly enriched, which indicate sulfidic environment. Mo/TOC reflects a restricted water column. The upper slope settings may have developed under sulfidic- suboxic dynamic water masses. The thickness of black shales is small, but organic matter abundance is the most high. Trace elements (V, Ni, Mo and U) enrichments are low and Mo/TOC data suggest a moderately restricted water column. Basin facies strata are composed of interbedded black chert and black siliceous shale, which are thin and have low organic matter abundance. The enrichment factors of V and U are higher than those in the inner platform, but for Ni and Mo, their EF values are relatively lower. The majority of the basinal strata were deposited in anoxic conditions; however, the fluctuation of Mo/TOC may reflect ephemeral upwelling activities. In conclusion, the thickness, organic matter abundance and enrichment of trace elements of the lower Cambrian black rock series in northern Guizhou are mainly controlled by the belts of different sedimentary environment and different redox states.
keywords:Lower Cambrian  Niutitang Formation  black rock series  sedimentary environment  geochemical characteristics  northern Guizhou
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