Redox conditions and manganese metallogenesis in the Cryogenian Nanhua Basin: Insight from the basal Datangpo Formation of South China

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 529; pp. 39 - 52
• Main Authors: Ma, Zhixin, Liu, Xiting, Yu, Wenchao, Du, Yuansheng, Du, Qiuding
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2019
• Subjects: aluminum; basins; China; Cryogenian period; glaciation; iron; isotopes; manganese; Microbial activity; molybdenum; Paleoocean chemistry; Post-Sturtian; pyrite; Sea level; seawater; sulfur; Sulfur isotope; China; Microbial activity; Paleoocean chemistry; Sea level; Post-Sturtian; Sulfur isotope
• ISSN: 0031-0182
• DOI: 10.1016/j.palaeo.2019.05.031

In South China, the Datangpo Formation was deposited during the Cryogenian interglacial stage between the Sturtian and Marinoan glaciations. The variations in paleoocean chemistry recorded in the Datangpo Formation are important to understand the formation of Mn ore as well as the early evolution of animals, which are not well constrained. Based on lithological observation and multi-geochemical proxies (iron speciation, Mo, U, V, Mn, Al and pyrite sulfur isotope) from drill core ZK43-6 from southeastern Chongqing, South China, the results indicate an anoxic (mostly euxinic) water condition for the lower black shales of the Datangpo Formation, which can be further divided into four intervals (I, II, III, IV). Among of them, very high Mn content and manganese metallogenesis is related to the suboxic Interval II between two euxinic depositions (Interval I and Interval III). Thus, our new findings suggest that the general euxinic condition at the basal Datangpo Formation is interrupted by a suboxic deposition (Interval II) where the manganese deposits formed. An updated model is proposed to shed light on the evolution in redox conditions of the Datangpo Formation as a function of sea-level and terrigenous input, and the genesis of “Datangpo-type” manganese in light of the temporal seawater redox conditions and microbial activity. •Reconstruction of the redox conditions in the lower part of the Datangpo Formation•Rhodochrosite is formed in the suboxic interval between euxinic two intervals.•An updated stratified redox model is proposed for manganese metallogenesis.