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

Ma, Zhixin; Liu, Xiting; Yu, Wenchao; Du, Yu; Du, Qizhen

doi:10.1016/j.palaeo.2019.05.031

Cited by 38 publications

(6 citation statements)

References 119 publications

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“…Covariance between U and Mo is observed and speculated to be related to an Mn-oxide particulate shuttle mechanism. However, U is unaffected in this process, remaining within concentrations close to the crustal average (Algeo and Tribovillard, 2009;Wu et al, 2016;Ma et al, 2019). Interestingly, the U enrichment factor detected in our Mn-bearing rocks is only slightly above crustal levels (EF up to 3), supporting the statement above.…”

Section: Origin and Paleoredox Depositional Conditions Of The Mn-bear...supporting

confidence: 87%

Paleoproterozoic manganese oxide precipitation in oxic seawater surface and reductive enrichment in anoxic seafloor

et al. 2022

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Section: Origin and Paleoredox Depositional Conditions Of The Mn-bear...supporting

confidence: 87%

Paleoproterozoic manganese oxide precipitation in oxic seawater surface and reductive enrichment in anoxic seafloor

et al. 2022

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“…Dolomite mounds are scattered in clastic rocks and are considered as one of the typical signs of ancient methane leakage structures [36,37]. Cap carbonates are widely associated with manganese-rich deposits [38,39]. Some scholars believe that the manganese-rich carbonate layer at the bottom of the Datangpo formation (Nh 2 d) is equivalent to the carbonate cap layer [20,40,41].…”

Section: Discussionmentioning

confidence: 99%

Sedimentary Setting and Ore-Forming Model in the Songtao Manganese Deposit, Southwestern China: Evidence from Audio-Frequency Magnetotelluric and Gravity Data

Gao

et al. 2021

Minerals

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The break-up of the supercontinent Rodinia in the late Neoproterozoic led to the formation of the Nanhua rift basin within the South China Block. The Datangpo-type manganese deposit, which developed in the Nanhua rift basin, is one of the most important types of manganese deposits in South China. Although it is widely accepted that deep sedimentary structures significantly affect the manganese ore system, the relationship between the manganese deposits in South China and the Nanhua rifting process is still unclear. The origin of the manganese ore layer remains controversial. In this paper, we integrated the audio-frequency magnetotelluric (AMT) data, gravity data, and comprehensive geological and borehole data analysis to characterize the structure of the Datangpo-type manganese deposit in Songtao, Guizhou Province. The resistivity and density models produced an inclined layered structure, which correlated well with the coeval sediment strata of the Nanhua rift basin. A high-resistivity cap was observed from the surface to a depth of 800 m, corresponding to the Cambrian Loushanguan (ϵ3−4ls) and Palang dolomite formation (ϵ2p), which has helped the storage of the manganese ore. The most significant low-resistivity anomaly (25–40 Ω·m) resides at a depth of 1400 m in the Nantuo (Nh3n) gravel sandstone and Datangpo (Nh2d) silty and carbonaceous shale, corresponding to the ore-forming layer. This distinct low-resistivity layer was possibly produced by aqueous fluids and pyrite in the syn-sedimentary fault and alteration zone. The accumulations of sulfide minerals in the rock samples suggest a possible anoxic-euxinic deposition environment during the manganese mineralization and precipitation. The fault revealed in the resistivity models is perhaps a previous fault zone produced by extension in the Nanhua rifting process, which provided migration and upwelling channels for ore-forming minerals. Based on our resistivity models, density models, and geological survey, the manganese ore-forming model was derived, which can help to provide geophysical evidence for the origin of the Datangpo-type manganese deposit.

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“…Extensive sedimentological and geochemical data have been obtained from shales of the Datangpo Fm. including iron speciation, trace metal, and rare earth and yttrium (REY) abundances as well as stable C, N, S, Fe, and Mo isotope compositions [10,11,[21][22][23][24][25][26]. The combined geochemical studies suggest that the interglacial Nanhua Basin environment is best described by a stratified water column with anoxic and limited euxinic deep waters.…”

Section: The Cryogenian Datangpo Formation and The Emergence Of Substmentioning

confidence: 99%

“…The combined geochemical studies suggest that the interglacial Nanhua Basin environment is best described by a stratified water column with anoxic and limited euxinic deep waters. However, deep waters temporarily changed to suboxic conditions associated with widespread dissolution of Mn-oxy/hydroxides (positive Ce anomalies [24]) being deposited on the basin floor which subsequently were transformed into diagenetic Mn carbonates under reducing pore water conditions [22,23]. Reducing pore waters further resulted in a near-quantitative Fe-oxy/hydroxide transformation into sulphides leading to relatively heavier Fe isotope compositions in the remaining seawater [11].…”

Section: The Cryogenian Datangpo Formation and The Emergence Of Substmentioning

confidence: 99%

“…The element distribution in Cryogenian seawater in the Nanhua Basin can be represented by leachates of OM-rich shale and Mn carbonates building up the basal Datangpo Fm. which most likely precipitated under manganous to slightly euxinic bottom water conditions and under the presence of a massive DOC pool [11,[20][21][22][23]. Under reducing conditions many vital trace elements (TE), although potentially abundant in Nanhua Basin seawater (given the overlap in elemental concentration of L5 with UCC), were adsorbed onto sinking OM or bound in sedimentary sulphides or thiomolybdates (Zn, Ba, Mo) and not recycled in the water column.…”

Section: The Redox State and (Bio)geochemical Metal Cycling In The Crmentioning

confidence: 99%

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Trace Metal and Cd Isotope Systematics of the Basal Datangpo Formation, Yangtze Platform (South China) Indicate Restrained (Bio)Geochemical Metal Cycling in Cryogenian Seawater

et al. 2020

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The behaviour of bioavailable trace metals and their stable isotopes in the modern oceans is controlled by uptake into phototrophic organisms and adsorption on and incorporation into marine authigenic minerals. Among other bioessential metals, Cd and its stable isotopes have recently been used in carbonate lithologies as novel tracer for changes in the paleo primary productivity and (bio)geochemical cycling. However, many marine sediments that were deposited during geologically highly relevant episodes and which, thus, urgently require study for a better understanding of the paleo environment are rather composed of a mixture of organic matter (OM), and detrital and authigenic minerals. In this study, we present Cd concentrations and their isotopic compositions as well as trace metal concentrations from sequential leachates of OM-rich shales of the Cryogenian basal Datangpo Formation, Yangtze Platform (South China). Our study shows variable distribution of conservative and bioavailable trace metals as well as Cd isotope compositions between sequential leachates of carbonate, OM, sulphide, and silicate phases. We show that the Cd isotope compositions obtained from OM leachates can be used to calculate the ambient Cryogenian surface seawater of the restricted Nanhua Basin by applying mass balance calculations. By contrast, early diagenetic Mn carbonates and sulphides incorporated the residual Cd from dissolved organic matter that was in isotopic equilibrium with deep/pore waters of the Nanhua Basin. Our model suggests that the Cd isotopic composition of surface seawater at that time reached values of modern oxygenated surface oceans. However, the deep water Cd isotope composition was substantially heavier than that of modern fully oxygenated oceans and rather resembles deep waters with abundant sulphide precipitation typical for modern oxygen minimum zones. This argues for incomplete recycling of Cd and other bioavailable metals shortly after the Sturtian glaciation in the redox stratified Cryogenian Nanhua Basin. Our study highlights the importance of sequential leaching procedures when dealing with impure authigenic sediments such as OM-rich carbonates, mudstones, or shales to achieve reliable trace metal concentrations and Cd isotope compositions as proxies for (bio)geochemical metal cycling in past aquatic systems.

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

Cited by 38 publications

References 119 publications

Paleoproterozoic manganese oxide precipitation in oxic seawater surface and reductive enrichment in anoxic seafloor

Paleoproterozoic manganese oxide precipitation in oxic seawater surface and reductive enrichment in anoxic seafloor

Sedimentary Setting and Ore-Forming Model in the Songtao Manganese Deposit, Southwestern China: Evidence from Audio-Frequency Magnetotelluric and Gravity Data

Trace Metal and Cd Isotope Systematics of the Basal Datangpo Formation, Yangtze Platform (South China) Indicate Restrained (Bio)Geochemical Metal Cycling in Cryogenian Seawater

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