Organic geochemistry and petrology of barren and Mo–Ni–PGE mineralized marine black shales of the Lower Cambrian Niutitang Formation (South China)

Křı́bek, Bohdan; Sýkorová, Ivana; Pašava, Jan; Machovič, Vladimı́r

doi:10.1016/j.coal.2007.02.002

Cited by 76 publications

(12 citation statements)

References 26 publications

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“…Thus, the negative Ce anomalies measured in this study (0.30-0.74; Table 3) are indicative of an oxic marine environment during black shale deposition. The oxic conditions are consistent with the concept that a large amount of organic matter was derived from organisms in the euphotic zone (Kříbek et al, 2007;Pi et al, 2013), as determined from the results of biomarker geochemistry (see Section 5.3.2). Under oxic conditions, the Ce 3+ dissolves in sea water is oxidized to Ce 4+ , forming Ce(OH) 4 or CeO 2 , which is adsorbs onto the surface of Fe-or Mn-oxides, precipitates, and falls to the seabed.…”

Section: Insights From Rare Earth Element Geochemistrysupporting

confidence: 67%

“…For instance, a study of the Ni-Mo deposits in the Zunyi and Zhangjiajie areas of South China by Kříbek et al (2007) revealed that the mineralized ore horizon contains three different types of organic matter, whereas the surrounding barren black shales contain only one type. This suggests that a certain type of organic matter is necessary for the formation of the Ni-Mo deposits in this area (Cao et al, 2013), demonstrating the utility of this research approach (Greenwood et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Origin of early Cambrian black-shale-hosted barite deposits in South China: Mineralogical and geochemical studies

Han

Cao

et al. 2015

Journal of Asian Earth Sciences

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Section: Insights From Rare Earth Element Geochemistrysupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Origin of early Cambrian black-shale-hosted barite deposits in South China: Mineralogical and geochemical studies

Han

Cao

et al. 2015

Journal of Asian Earth Sciences

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“…The location of the polymetallic sulfi de bed in the Niutitang Formation is controlled by the transition from a shallow shelf oxidic into a deep shelf anoxic water environment ( Li, 1986 ). Numerous remnants of bacteria in ore shale matrix resembling phototrophic coccoid cyanobacteria ( Steiner et al , 2001;K ř íbek et al , 2007 ) suggest that the mineralized layer must have been located at moderate depth, most likely close to the limit of light penetration (dysphotic zone 50 -200 m), close to the oxic -anoxic and sulfi desaturated water interface. In contrast to phosphatic hardground, in the sense of Southage (1986a, b) and Cook et al (1990) , the sulfi de ore bed contains up to 85% clastic particles (concentric sulfi de and phosphate nodules) that show ample evidence of at least short-distance transport.…”

Section: Depositional Environment At the Huangjiawan Minementioning

confidence: 99%

Multiple Sources of Metals of Mineralization in Lower Cambrian Black Shales of South China: Evidence from Geochemical and Petrographic Study

et al. 2008

Self Cite

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Black shales of the Lower Cambrian Niutitang Formation in southern China (Huangjiawan mine, Zunyi region, northern part of the Guizhou Province) host regionally distributed stratiform polymetallic Ni-Mo-platinum group elements (PGE)-Au phosphate-and sulfi de-rich ores. These are confi ned to a £ 0.2-m thick ore horizon composed of mineralized bodies of algal onkolites, phosphate nodules, and sulfi de and shale clasts in a mineralized phosphate-and organic matter-rich matrix. Compared to footwall and hanging wall shales, the ore bed is strongly enriched in Ni (up to 100-fold), As (up to 97-fold), Mo (up to 95-fold), Sb (up to 67-fold), Rh (up to 49-fold), Cu (up to 37-fold), Pd (up to 33-fold), Ru (up to 24-fold), Zn (up to 23-fold), Pt (up to 21-fold), Ir (up to 15-fold), Co (up to 14-fold), and Pb (up to 13-fold). Even footwall and hanging wall black shales are signifi cantly enriched by Mo (21-fold) and Ni (12-fold) but depleted in Cr in comparison to average Cambrian black shale. Organic matter is represented by separate accumulations dispersed in the rock matrix or as biotic bitumen droplets and veinlets in ore clasts. Similar organic carbon (C org ) values in an ore bed and enclosing footwall and hanging wall shales of little mineralization indicate that metal accumulation was not controlled only by biogenic productivity and organic matter accumulation rate. Evaporitic conditions during sedimentation of the basal part of the Niutitang Formation were documented by an occurrence of preserved Ni-, V-, Cr-, and Cu-enriched phosphate-rich hardground with halite and anhydrite pseudomorphs on the paleosurface of the underlying Neoproterozoic carbonates. Neoproterozoic black shales of the Doushantuo Formation are characterized by increased metal concentrations. Comparison of metal abundances in both hardground and Doushantuo black shales indicate that black shales could have become a source of metal-rich hardground during weathering. The polymetallic Ni-Mo-PGE sulfi de-rich ore bed is interpreted to represent a remnant of shallow-water hardground horizon rich in metals, which originated in a sediment-starved, semi-restricted, seawater environment. During the Early Cambrian transgression an infl ux of fresh seawater and intensive evaporation, together with the hydrothermal enrichment of seawater in a semi-restricted basin, resulted in the formation of dense metalliferous brines; co-precipitation of metals together with phosphates and sulfi des occurred at or above the oxic -anoxic sediment interface. Metal-enriched hardground was disintegrated by the action of waves or bottom currents and deposited in a deeper part of the anoxic basin. Contemporaneously with the formation of a polymetallic Ni-Mo-PGE-Au sulfi de ore bed, economic sedimentary exhalative

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“…Locally, Mo sulfides reach 18.3 wt % (Fan, 1983). This layer is also rich in vanadium, uranium, selenium, and many other transition elements (Kríbek et al, 2007;Orberger et al, 2007). Uranium concentrations can reach 595 ppm (Xu et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Because of its ultrahigh metal concentrations and its location near the Precambrian-Cambrian transition, the polymetallic sulfide ore layer has attracted considerable research and exploitation interest. A variety of mechanisms, such as seabed exhalative sedimentation (e.g., Lott et al, 1999;Steiner et al, 2001;Jiang et al, 2009), seawater precipitation (e.g., Mao et al, 2002;Xu et al, 2012), and biogenic (bacterial) metal accumulation (e.g., Kríbek et al, 2007;Orberger et al, 2007), have been proposed to explain its unique formation.…”

Section: Introductionmentioning

confidence: 99%

Uranium Mineralization and Its Radioactive Decay-Induced Carbonization in a Black Shale-Hosted Polymetallic Sulfide Ore Layer, Southwest China

Zhu

Luo

et al. 2015

Economic Geology

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The black shale in the Lower Cambrian Niutitang Formation, southwest China, which has been dated to 532.3 ± 0.7 Ma by U-Pb radiometric measurements, hosts a sedimentary layer with abnormally high Ni-Mo-PGE-Au contents. This layer is enriched in Ni (up to 3.8 wt %), Mo (up to 7.7 wt %), and U (up to 595 ppm), but its genesis is still controversial. Here we report the first direct observation of uranium-bearing minerals and their radioactive effects on the surrounding matter in the polymetallic sulfide ore. X-ray absorption fine structure analyses confirmed the reduced valence state of uranium. In combination with high-resolution electron microscopy and electron probe microanalysis, the mineral was identified as coffinite (USiO4). A strong positive correlation between the sizes of the coffinite crystals and their surrounding carbonized rings reveals that the coffinite is authigenic, and its crystallization-produced radiation resulted in the radiolysis of surrounding organic matter. The association of various biogenic metal sulfides, phosphates, and abundant organic substances within the Ni-Mo sulfide-enriched ore suggests that biological adsorption may have participated in the enrichment of soluble U(VI), and that microbial sulfate reduction might have facilitated the uranium mineralization.

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Organic geochemistry and petrology of barren and Mo–Ni–PGE mineralized marine black shales of the Lower Cambrian Niutitang Formation (South China)

Cited by 76 publications

References 26 publications

Origin of early Cambrian black-shale-hosted barite deposits in South China: Mineralogical and geochemical studies

Origin of early Cambrian black-shale-hosted barite deposits in South China: Mineralogical and geochemical studies

Multiple Sources of Metals of Mineralization in Lower Cambrian Black Shales of South China: Evidence from Geochemical and Petrographic Study

Uranium Mineralization and Its Radioactive Decay-Induced Carbonization in a Black Shale-Hosted Polymetallic Sulfide Ore Layer, Southwest China

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