Black Shale Series-hosted Silver-Vanadium Deposits of the Upper Sudan Doushantuo Formation, Western Hubei Province, China

Abstract The lower and the upper parts of the Doushantuo Formation, Hubei Province, China, contain silicate-type K-rich beds (illite and feldspar), and intraclastic phosphorites, as well as Ag-V and V deposits in a "Black Shale Series". The K-rich beds formed in an anoxic basin whereas the phosphorites formed in a more oxic and higher energy depositional environment. The Black Shale Series occurs in the lower and upper parts of the Doushantuo Formation; that in the upper part consists of black illite shale and dark gray dolostone, and contains Se-rich Ag and V deposits. These deposits are of more industrial significance than the previously discovered Ni-Mo polyelement sul-fide deposits which occur in the Lower Cambrian Black Shales Series of South China. Studies of lithotype, sedimentary sequence, and geochemistry of the Doushantuo Formation have led to more attention being focused on the uppermost Black Shale Series and its Ag-V and V deposits. There are three ore types: black, Ag-V-rich, illite shale; black, V-rich, illite shale; and dark gray, Ag-V-rich, finely crystalline dolostone. The first two ore types contain 3% to 5% C^ and the last, 1.25%. The Ag-bearing minerals are naumannite, argyrodite, aguilarite, acanthite, and native silver that occur as inclusions in pyrite associated with barite. Vanadium substitutes for Al in illite and is also related to organic-matter contents. Because (1) the pre-Sinian Kongling Group contains one to three times greater than the Clark Ag value; (2) black, illite shale has a negative Ce anomaly; and (3) there are large occurrences of black, K-rich, tuffaceous, fine siltstone, the sources of Ag are thought to include subaerial and submarine volcanic materials. It is proposed that Ag, V, and Se were absorbed by clay particles and organic matter during syngenetic deposition in an anoxic environment; Ag subsequently was reconcentrated into sulfides and selenides, whereas V was incorporated structurally into illite during early and late diagenesis. These types of Black Shale Series-hosted Ag-V and V deposits are, therefore, considered to be sedimentary-diagenetic in origin.
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Summary: The three traditional types of Variscan vein Pb-Zn-(Ag) mineralization recognized in the Bohemian massif from historic paragenetic studies are confirmed by modern metallogenic studies. Stable C, S, and O isotope data, as well as Pb and Sr isotopic ratios of the deposits, indicate a 4 predominantly crustal origin of the constituents in all three types. Although the data also suggest differences in temperature and pressure of formation, and the oxidation conditions and nature of the hydrotherma...
Publication: Exploration & Mining Geology
Author(s): J.H. BERNARD, K. ZAK
Issue: 1
Volume: 1
Year: 1992
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Summary: Giant, sediment-hosted lead-zinc deposits in northern Australia formed during development of Mid-Proterozoic extensional basins that overlie Lower Proterozoic basement. The basement in the Mount Isa area, exposed by folding and faulting, contains fractionated, high-heat-producing granites. These granites generate heat at a rate of about 6/iWm-3, probably sufficient to form giant lead-zinc deposits either by (a) driving episodic convection of saline basement and basin fluids for periods of...
Publication: Exploration & Mining Geology
Author(s): M. SOLOMON, C.A. HEINRICH
Issue: 1
Volume: 1
Year: 1992
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Summary: Auriferous, bedding-parallel veins occur in zones of carbonaceous, argillaceous and sulfidic turbidites in the Lower to Middle Cambrian sandy flysch of the Goldenville Formation. The S^S values for vein and wall-rock arsenopyrite and pyrrhotite, and for regional pyrite and pyrrhotite, are highly positive. The values are similar to those from Cambro-Ordovician sediment-hosted deposits of other types, and display trends that increase upward in the stratigraphic sequence. The similarity in...
Publication: Exploration & Mining Geology
Author(s): ALAN L. SANGSTER
Issue: 1
Volume: 1
Year: 1992
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Summary: The Urkut rhodochrosite deposit and Branisko Mn showings (rancieite, manganiferous calcite), located in Lower Jurassic marine sedimentary rocks with black shale, were studied by organic-geochernical methods. Both depositional localities were affected by the Lower Jurassic Toarcian anoxic event. Urkiit shales are rich in organic matter (av. 2.94 wt^o total organic carbon), the composition of which indicates derivation mainly from marine sources, with some terrigenous component. The shales...
Publication: Exploration & Mining Geology
Author(s): MARTA POLGARI, BOHUMIL MOLAK, EVA SUROVA
Issue: 1
Volume: 1
Year: 1992
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Summary: Unusually rich molybdenum ores (cutoff grade = 4.1% Mo) hosted by Lower Cambrian black shales have been mined since 1985 near Zunyi in the province of Guizhou in China. Similar ores were once worked for Mo and Ni near Dayong in the province of Hunan. In both mining areas, mineralization occurs in Lower Cambrian black shale (Niutitang Formation and strati-graphic equivalents) as a single sulfide bed or lens with exposed thicknesses up to 15 cm and reported thicknesses up to 35 cm. In addition...
Publication: Exploration & Mining Geology
Author(s): RAYMOND M. COVENEY JR., JAMES B. MUROWCHICK, R.I. GRAUCH, CHEN NANSHENG
Issue: 1
Volume: 1
Year: 1992
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Summary: Thick westward prograding clastic wedges were deposited along the margin of ancestral North America from Mid-Proterozoic to Mid-Paleozoic time. Periodic rifting and tectonic subsidence resulted in the formation of starved sub-basins along this otherwise passive continental margin. These sub-basins host important sedimentary exhalative barite-zinc-lead-silver deposits. In northeastern British Columbia, a thick succession of Paleozoic basinal facies clastic rocks is preserved within the...
Publication: Exploration & Mining Geology
Author(s): D.G. MACINTYRE
Issue: 1
Volume: 1
Year: 1992
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Summary: A thin layer of stratiform Ni-Zn-PGE sulfide mineralization of sedimentary-diagenetic origin was deposited during the Middle to Upper Devonian in the euxinic "Nick basin". The mineralized unit (>3 cm thick), which seems to have been developed over the entire sedimentary basin of > 80 km2, consists of pyrite, vaesite (NiS^, and sphalerite. The average grade of the mineralization is about 5.3% Ni, 0.73% Zn, =770 ppb (PGE + Au), and up to 61 ppm Re. Anomalous Se, As, Mo, P, Ba and U are present....
Publication: Exploration & Mining Geology
Author(s): LARRY J. HULBERT, D. CONRAD GREGOIRE, DOGAN PAKTUNC, ROBERT C. CARNE
Issue: 1
Volume: 1
Year: 1992
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