Field Relations, Origins, and Resource Implications for Platiniferous Molybdenum-Nickel Ores in Black Shales of South China
Exploration & Mining Geology, Vol. 1, No. 1, 1992
RAYMOND M. COVENEY, JR. JAMES B. MUROWCHICK, Department of Geosciences, University of Missouri-Kansas City, Kansas City, Missouri, R.I. GRAUCH, U.S. Geological Survey, Denver, Colorado, CHEN NANSHENG Institute of Geochemistry, Academia Sinica, Guiyang, Guizhou, and MICHAEL D. GLASCOCK, University of Missouri Research Reactor, Columbia, Missouri
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 to high Mo values (4% to 7%), ore samples contain up to 7% Ni, 2% Zn, 2.5% As, and several hundred ppb Au and Pt-group elements, but the precious metals have never been recovered from the ores. Sporadic occurrences of Mo-Ni sulfide ore beds are found in at least five provinces stretching approximately 1600 km from Yunnan to Zhejiang. None of the Mo-Ni ore-bed occurrences has any obvious connection with mafic or ultramafic source rocks. Similar occurrences containing elevated values for Ni, Mo, and PGE exist in Devonian black shale in the Yukon. Future exploration for Pt, Au, Mo, and Ni deposits should consider this previously unknown type of sediment-hosted mineral deposit.