The article describes mineral composition of laterite weathering mantle overlapping the Amamuri and Kontakt gold deposits in the greenstone rocks, located 20 km southeast of the Aurora deposit (reserves of 185 tons Au, Republic of Guyana). The major minerals of the weathering mantle include disordered kaolinite (35–90 wt. %), relict quartz and hydromica (up to 20 wt. % illite). The heavy concentrate is represented by limonite (up to 8 wt. % goethite), magnetite, hematite, ilmenite, anatase, ferrous rutile, psilomelane, pyrite, chalcopyrite, galena, sphalerite, covellite, zircon, tourmaline, epidote and amphibole. Native gold composes significant amount of heavy concentrates (up to 9 wt. %) and includes the following types: 1) lode gold in relict quartz veins and stockwork,  2) relict gold in laterite and 3) supergene gold. According to mineralogical studies, moderate lateritization and monosialitization processes are probably due to erosion of ancient areal weathering mantle and the presence of immature laterites over the Amamuri and Kontakt deposits. Most amount of gold is relic. The processes of its redeposition and supergene alterations are weak. The dominant size of gold grains of <100 µm makes gravitational concentration of laterites more difficult, whereas weakly ordered kaolinite prevents agglomeration during cyanidation and heap leaching. Alluvial placers are probably more promising for exploration, since they provide natural fractionation of gold particles by size favorable for gravity extraction.

Figures 8. Table 3. References 23.

Key words: lateritic weathering mantle, supergene gold, Guyana

E.E. Palenova, Institute of Mineralogy SU FRC MG UB RAS, Miass, Chelyabinsk oblast, 456317 Russia; palenova@mineralogy.ru

K.A. Novoselov, Institute of Mineralogy SU FRC MG UB RAS, Miass, Chelyabinsk oblast, 456317 Russia;

E.V. Belogub, Institute of Mineralogy SU FRC MG UB RAS, Miass, Chelyabinsk oblast, 456317 Russia;

1. Beyer S.R., Hiatt E.E., Kyser K., Drever G.L., Marlatt J. (2015) Stratigraphy, diagenesis and geological evolution of the Paleoproterozoic Roraima Basin, Guyana: Links to tectonic events on the Amazon Craton and assessment for uranium mineralization potential. Precambrian Research, 267, 227–249.
2. Béziat D., Siebenaller L., Salvi S., Chevalier P. (2016) A weathered skarn-type mineralization in Ivory Coast: The Ity gold deposit. Ore Geology Reviews, 78, 724–730.
3. Bowell R.J., Gise A.P., Foster R.P. (1993) The role of fulvic acid in the supergene migration of gold in tropical rain forest. Geochimica et Cosmochimica Acta, 57, 4179–4190.
4. Butt C.R.M. (1998) Supergene gold deposits. AGSO Journal of Australian Geology & Geophysics, 17(4), 89–96.
5. Frimmel H.E. (2014) Chapter 10. A giant Mesoarchean crustal gold-enrichment episode: possible causes and consequences for exploration. Society of Economic Geologists Special Publication, 18, 209–234.
6. Gill E.D. (1961) The climates of Gondwanaland in Kainozoic times. In: A.E.M. Nairn, Ed., Descriptive Palaeoclimatology, Interscience Publishers, New York, 332–353.
7. http://www.transglobalgoldcorp.com/Guyana_Geology___Mining_Report.pdf
8. https://www.guygold.com/Operations/Aurora-GoldMine/default.aspx
9. Kalinin Yu.A., Kovalev K.R., Naumov E.A., Kirillov M.V. (2009) Gold in the weathering crust at the Suzdal’ deposit (Kazakhstan). Russian Geology and Geophysics, 50(3), 174–187.
10. Kalinin Yu.A., Roslyakov N.A., Prudnikov S.G. (2006) Gold-bearing weathering crust in the south of Siberia. Novosibirsk: Geo, 339 p. (in Russian)
11. Mann A.W. (1984) Redistribution of gold in the oxidised zone of some Western Australian deposits. Goldmining, Metallurgy and Geology. Proceedings of the Regional Conference on Mining and Metallurgy. Perth and Kalgoorlie, October 1984, Australasian Institute of Mining and Metallurgy, Melbourne, 1–12.
12. [Native gold of lode and placer deposits in Russia: Atlas] (2015). Moscow, Akvarel, 200 p. (in Russian)
13. Raleigh W. (1596) The discovery of the large, rich, and beautiful Empire of Guiana, with a relation of the great and golden city of Manoa (which the Spaniards call El Dorado) and the Provinces of Emeria, Aromaia, Amapaia, and other Countries, with their rivers, adjoining. By Robert Robinson, 112 p.
14. [Report on field work of OJSC VNIIZARUBEZHGEOLOGIYA in the Cooperative Republic of Guyana at the G-120, G-121 concessions in JanuaryJuly 2010] (2010) Georgetown Gold, Metals & Minerals Inc. (GGMM), OJSC VNIIZARUBEZHGEOLOGIYA. Moscow, 51 p. (in Russian)
15. [Report on searching and prospecting at the site Amamuri, Cooperative Republic of Guyana, as of 07/20/2016] (2016) LLC «Zolotoy Rudnik», LLC «Zolotoy Priisk». Moscow, 102 p. (in Russian)
16. Samama J.-C. (1986) Ore fields and continental weathering. New York, Van Nostrand Reinhold Company Inc., 326 p.
17. Santos-Francés F., García-Sánchez A., Alonso-Rojo P., Contreras F., Adams M. (2011) Distribution and mobility of mercury in soils of a gold mining region, Cuyuni river basin, Venezuela. Journal of Environmental Management, 92, 1268–1276.
18. Tedeschi M., Hagemann S.G., Davis J. (2018a) The Karouni gold deposit, Guyana, South America: Part I. Stratigraphic setting and structural controls on mineralization. Economic Geology, 113(8), 1679–1704.
19. Tedeschi M., Hagemann S.G., Roberts M.P., Evans N.J. (2018б) The Karouni gold deposit, Guyana, South America: Part II. Hydrothermal alteration and mineralization. Economic Geology, 113(8), 1705–1732.
20. Teixeira J.B.G., Misi A., Silva M.G. (2007) Supercontinent evolution and the Proterozoic metallogeny of South America. Gondwana Research, 11, 346–361.
21. Voicu G., Bardoux M., Jebrak M. (1999) Tellurides from the paleoproterozoic Omai gold deposit, Guyana shild. Canadian Mineralogist, 37, 559–573.
22. Voicu G., Bardoux M., Stevenson R. (2001) Lithostratigraphy, geochronology and gold metallogeny in the northern Guiana Shield, South America: a review. Ore Geology Reviews, 18, 211–236.
23. Webster I.G., Mann A.W. (1984) The influence of climate, geomorphology and primary geology on the supergene migration of gold and silver. Journal of Geochemical Exploration, 22, 21–42.