Hostname: page-component-78c5997874-dh8gc Total loading time: 0 Render date: 2024-11-02T21:27:20.587Z Has data issue: false hasContentIssue false
  • English
  • Français

Some aspects of the genesis of heavy mineral assemblages in Lower Proterozoic uranium-gold conglomerates

Published online by Cambridge University Press:  05 July 2018

H. Clemmey
H. Clemmey*
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds, LS2 9JT
Get access Rights & Permissions [Opens in a new window]

Abstract

Some genetic models for Lower Proterozoic gold- and uranium-bearing pyritic conglomerates favour a modified placer origin in which low levels of atmospheric oxygen are used to account for the survival of uraninite and pyrite. There are many difficulties with such models—for example magnetite is absent in the ore-bearing horizons although it is stable in anoxic conditions, while it is abundant in over- and under-lying strata. Compact and porous pyrite grains are not in hydraulic equivalence and the deposits lack a normal detrital heavy-mineral assemblage. Moreover uranium and gold show evidence of diagenetic remobilization, the uranium becoming associated with secondary titaniferous phases and uranium and gold being enriched in reduzate facies sediments.

New evidence concerning the genesis of the deposits is derived from a clast of ferric iron clay thought to represent a precursor sediment of the Witwatersrand Basin. Reworking of such clays and transport of a magnetite and ferric clay assemblage with subsequent sulphidation, could account for the porous pyrites, the absence of magnetite and the lack of hydraulic equivalence of the mineral grains in the conglomerates. The presence of oxygen, as indicated by the ferric iron clasts, would account for the evidence of mobility of uranium and of gold and would enhance their extraction from source rocks; particularly the release of gold from a precursor auriferous iron formation source. It is suggested that some aspects of the genesis of uranium deposits of the Witswatersrand and Elliot Lake may be similar to those of the Phanerozoic ‘Roll Front’ ores involving interaction between oxidizing uraniferous groundwaters and previously sulphidized and reduzate facies sediments.

Type
Research Article
Information
Mineralogical Magazine , Volume 44 , Issue 336 , December 1981 , pp. 399 - 408
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1981

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Badham, N. P. (1978). The origins of ore deposits in sedimentary rocks. In Economic Geology and Geotectonics. Tarling, D. H. (ed.). Blackwell Scientifc, 149-91.Google Scholar
Borchors, R. (1964). Exploration of the Witwatersrand System and its extensions. In Haughton, S. H. (ed.) The Geology of some Ore deposits in Southern Africa. Geol. Soc. S. Africa, 123.Google Scholar
Bottrill, T. J. (1971). Uranifer0us Conglomerates of the Canadian Shield. Geol. Surv. Can. Rept. of Activities, pap. 71-1, Part A. 77-83.Google Scholar
Button, A. and Tyler, N. (1979). Precambrian Palaeoweathering and erosion surfaces in Southern Africa: Review of their character and economic significance. Inf. Circ. Econ. Geol. Res. Unit., Univ. 14∼twatersrand, Johannesburg 135, 37 pp.Google Scholar
Clemmey, H. and Badham, N. (1981). Critial review of the geological evidence relating to atmospheric evolution. Geology (in press).Google Scholar
Davidson, C. F. (1957). On the occurrence of Uranium in Ancient Conglomerates. Econ. Geol. 52, 52-93.CrossRefGoogle Scholar
Davidson, C. F. and Bowie, S. H. U. (1951). On thucolite and related hydrocarbon uraninite complexes with a note on the Origin of the Witwatersrand Gold Ores. Bull. Geol. Surv. Gt. Britain, No. 3. 1-18.Google Scholar
de Kock, W. (1964). The geology and economic significance of the West Wits line. I. Some Ore Deposits in Southern Africa. Geol. Soc. S. Africa, vol. 1, 1-86.Google Scholar
Dimroth, E. (1979). Significance of diagenesis for the Origin of Witwatersrand-type Uraniferous Conglomerates. Phil. Trans. R. Soc. Lond. A. 291, 277-87.Google Scholar
Dimroth, E. and Kimberley, M. M. (1976). Precambrian atmospheric oxygen: Evidence in the sedimentary distribution of carbon, sulfur, uranium and iron. Can. J. Earth Set 13, 13-85.Google Scholar
Fripp, R. E. P. (1976). Stratabound gold deposits in Archean banded iron-formation, Rhodesia. Econ. Geol. 71, 71-75.CrossRefGoogle Scholar
Hallbauer, D. K. and Utter, T. (1977). Geochemical and morphological characteristics of gold particles from recent river deposits and the fossil placer of the Witwatersrand. Mineral. Deposita, 12, 293-306.CrossRefGoogle Scholar
Hester, B. W. (1970). Geology and evaluation of placer Gold deposits in the Klondyke Area, Yukon territory. Trans. lnst. Min. Met. 79, 79-7.Google Scholar
Kimberley, M. M. (1978). Origin of Stratiform uranium Deposits in Sandstone Conglomerate and pyroclastic rock. In Kimberley, M. M. (ed.) Short course in Uranium Deposits: Their Mineralogy and Origin. Min. Assoc. Canada, 339-81.Google Scholar
Krauskopf, K. B. (1967). Introduction to Geochemistry. McGraw-Hill International Series in the Earth and Planetary Sciences, 721 pp.Google Scholar
Liebenberg, W. R. (1955). The occurrence of and origin of Gold and radioactive minerals in the Witwatersrand System, the Dominion Reef System, the Ventersdorp Contact Reef and the Black Reef. Geol. Soc. S. Africa Trans. 58, 58-23.Google Scholar
Mcllveen, G. R. and Stevens, B. P. J. (1979). Supergene enrichment—an important process in the development of economic grades in gold-quartz veins. Geol. Soc. Australia. Econ. Geol. Spec. Group Meeting, Sydney (abs.).Google Scholar
Minter, W. E. L. (1976). Detrital gold uranium and pyrite concentrations relating to sedimentology in the Precambrian Vaal Reef placer, Witwatersrand, South Africa. Econ. Geol. 71, 71-76.Google Scholar
Pienaar, P. J. (1963). Petrology Stratigraphy and genesis of the Elliot Lake Group. Blind River, Ontario, including the Uraniferous Conglomerate. Geol. Surv. Can. Bull. 83, 140 pp.Google Scholar
Pretorius, D. A. (1975). The depositional environment of the Witwatersrand goldfields-—a chronological review of speculations and observations. Minerals Sci. Eng. 7, 7-47.Google Scholar
Ramdohr, P. (1958). New observations on the ores of the Witwatersrand and their genetic significance. Geol. Soc. S. Africa. Trans. 61 (annexe) 50 pp.Google Scholar
Reynolds, R. L. and Goldhaber, M. B. (1978). Origin of a South Texas Roll-Type Uranium Deposit: (1) Alteration of Iron and Titanium Oxide Minerals. Econ. Geol. 73, 167-789.CrossRefGoogle Scholar
Robertson, J. A. (1976). The Blind River Uranium Deposits: The Ores and their setting. Ontario Div. Mines MP65.Google Scholar
Roscoe, S. M. (1969). Huronian Rocks and uraniferous Conglomerates in the Canadian Shield. Geol. Surv. Can. Pap. 68-40.CrossRefGoogle Scholar
Roscoe, S. M. (1973). The Huronian Supergroup. A Paleoaphebian succession showing evidence of atmospheric evolution. In Huronian Stratigraphy and Sedimentation. Geol. Assoc. Can. Spec. Pap. 12, 31–47.Google Scholar
Saager, R. (1970). Structures in pyrite from the Basal Reef in the Orange Free State Goldfield. Geol. Soc. S. African Trans. 72, 72-46.Google Scholar
Saager, R. and Mihalik, P. (1967). Two varieties of pyrite from the Basal reef of the Witwatersrand System. Econ. Geol. 62, 62-31.CrossRefGoogle Scholar
Saager, R., Muff, R., and Hirdes, S. (1978). Investigations on pyritic conglomerates and banded iron formations from Archean Greenstone Belts and their bearing on the formation of the Witwatersrand Ores, South Africa. Gesellschaft Deutsch. Metallhutten und Bergleute, 33, 33-46.Google Scholar
Schumm, S. A. (1978). The Fluvial System. J. Wiley and Sons, 338 pp.Google Scholar
Simpson, P. R. and Bowles, J. F. W. (1977). Uranium mineralisation of the Witwatersrand and Dominion Reef Systems. Phil. Trans. R. Soc. Lond. A. 286, 527-48.Google Scholar
Simpson, P. R. and Bowles, J. F. W. (1981). Detrital uraninite and pyrite; are they evidence for a reducing atmosphere? In Genesis of Uranium and Gold-Bearing Precambrian Quartz-Pebble Conglomerates. USG Surv. Prof. Paper 1161.Google Scholar
Solomon, M. (1967). Fossil Gossans(?) at Mt. Lyell, Tasmania. Econ. Geol. 62, 62-72.CrossRefGoogle Scholar
Spurr, J. E. (1898). Geology of the Yukon gold district. 18th Ann. Rept. USGS, part III, 873-92.Google Scholar
Theis, N. J. (1978). Mineralogy and setting of the Elliot Lake Deposits. In Kimberley, M. M. (ed.) Short course in Uranium Deposits: Their mineralogy and Origin. Min. Assoc. Canada, 331-8.Google Scholar
Utter, T. (1977). Morphology and geochemistry of pyrites from the Upper Witwatersrand System of the Klerks-dorp Goldfield. Chamber of Mines of South Africa Research Rep. 8/77 48 pp.Google Scholar
Utter, T. (1980). Rounding of ore particles from the Witwatersrand gold and uranium deposit (South Africa) as an indicator of their Detrital Origin. J. Sed. Petrol. 50, 50-6.Google Scholar
Warren, H. V. (1979). Supergene gold crystals at Stirrup Lake, BC. West Miner. 52, 52-7.Google Scholar