Petrology,mineral chemistry,and exploration significance of Fe-sulfides from the metal dispersion halo surrounding the Cadjebut ZnPb MVT deposit,Western Australia |
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| Affiliation: | 1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Institutions of Earth Science, Chinese Academic of Sciences, Guangzhou 510640, China;2. University of Chinese Academic of Sciences, Beijing 100049, China;3. School of Earth Sciences, University of Western Australia, Crawley, WA 6009, Australia;4. Western Australia Organic and Isotope Geochemistry Centre, School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;5. Petro Bio Oil Consulting, Tallahassee, FL 32312, United States;6. Department of Chemical and Biomedical Engineering, Florida A & M University/Florida State University, Tallahassee, FL 32310, United States;7. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China;1. Department of Applied Geology, Institute of Geosciences and Exact Sciences, São Paulo State University (Unesp), Rio Claro, SP, Brazil;2. Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA;3. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada;1. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, Anhui 230009, China;2. Anhui Province Engineering Research Center for Mineral Resources and Mine Environments, Hefei University of Technology, Hefei, Anhui 230009, China;3. Ore Deposit and Exploration Centre, Hefei University of Technology, Hefei, Anhui 230009, China;4. Department of Geoscience, University of Nevada Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154-4010, USA;5. EGRU (Economic Geology Research Centre) and Academic Group of Geosciences, College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia;6. Unit for Environmental Sciences and Management, North West University, Private Bag X6001, Potchefstroom 2520, South Africa |
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| Abstract: | ![]()
The Cadjebut MVT mineralization is hosted by carbonate-evaporite units in the Givetian lower dolomite sequence of the Pillara platform, northern Western Australia, and occurs as 2 ore types: (1) An early Zn-rich, stratiform and rhythmically banded ore and its laterally equivalent halo of banded marcasite, barite ± calcite; and (2) a later cross-cutting, breccia-fill, Pb-rich ore. The 2 ore types are exploited through 2 mining lenses; an upper lens 1 and lower lens 2. The orebody is sited N of the normal, basin-side down, Cadjebut Fault. Rhythmically banded marcasite completely envelopes the orebody in both lenses, whereas banded barite occurs N of the lower lens 2 only where the barite is partially to completely replaced by late cloudy calcite + marcasite. Barite replacement by marcasite and cloudy calcite increases northwards. Petrographic and trace element data indicate 3 types of Fe-sulfides: (1) low-Pb Fe-sulfides with Pb contents <5300 ppm; high-Pb Fe-sulfides with Pb contents <30 000 ppm and, extremely high-Pb Fe-sulfides with > 30 000 ppm Pb. Only the ‘colloform’ pyrites exhibit Pb contents above 30 000 ppm, and SEM images show these elevated Pb contents are due to micron-scale galena inclusions. Mineral chemical data from sulfides in the stratiform Fe-sulfide and barite halos indicate that main ore-stage fluids of the rhythmically banded ore event were enriched in Zn, Pb, Cd, As and, to a minor extent Ni and Cu. Late-stage fluids of the rhythmically banded ore event were not saturated with respect to galena, precipitating low-Pb marcasites along the very outer fringes of the orebody, and replacing rhythmically banded barite in lens 2. Only the low-Pb marcasites show various stages of pyrite inversion. Petrographic and trace element mineral chemistry of the 2 stratiform halos are best explained by a model in which main ore stage fluids of the early rhythmically banded ore event emanated from below the Cadjebut orebody along an inferred antithetic reverse fault. The presence of a laterally zoned alteration halo with a pattern of proximal higher Pb and trace element-bearing Fe-sulfides provides a vector towards the ore zone, and has important exploration significance for this style of base-metal mineralization. |
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