Geochronological constrains on the timing of magmatism, deformation and mineralization at the Karouni orogenic gold deposit: Guyana, South America

• Published in: Precambrian research 2020-02, Vol.337, p.105329, Article 105329
• Main Authors: Tedeschi, M.T., Hagemann, S.G., Kemp, A.I.S., Kirkland, C.L., Ireland, T.R.
• Format: Article
• Language: English
• Subjects: Geochronology; Guiana Shield; Guyana; Karouni; Ore deposits; Orogenic gold; Paleoproterozoic; Rhyacian; Trans-Amazonian Orogeny
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2019.04.015

•Magmatism occurred from 2147 ± 16 Ma to 1955 ± 15 Ma with inherited zircons as old as 2220 Ma.•Compression at ∼2120 Ma, sinistral strike-slip at ∼2095 Ma dextral strike slip at ∼2084 Ma.•Gold mineralization dated via hydrothermal titanite to 2084 ± 15 Ma.•Mineralization at Karouni coeval to a major pulse of gold mineralization in West Africa at 2090 Ma. The Karouni deposit is located in central Guyana 35 km to the W of the former producing 5 Moz Omai mine and is interpreted to be an orogenic gold deposit. It is hosted in Rhyacian aged (2.2 to 2.1 Ga) volcano-sedimentary and intrusive rocks metamorphosed to greenschist facies. Detailed structural and crosscutting relationships, coupled with robust, new U-Pb geochronology on intermediate to felsic intrusive rocks and hydrothermal minerals from the Karouni camp have constrained the structural evolution of the deposit and provided a new age for gold mineralization with important implications for the structural framework and timing of gold mineralization throughout the region. Magmatism within the 200 km2 of the Karouni camp progressed from early, synvolcanic intermediate composition dikes at ∼2147 Ma to a major voluminous pulse of felsic magmatism coeval with regional deformation during the Trans-Amazonian Orogeny between 2120 and 2088 Ma. A late pulse of granitic magmatism at ∼1950 Ma may be related to a post orogenic event. Inherited zircons within the felsic intrusive rocks indicate assimilation of crust as old as 2223 ± 32 Ma. Gold mineralization associated with camp scale D2 deformation has been dated to 2084 ± 15 Ma on the basis of U-Pb geochronology of hydrothermal titanite. These results show gold mineralization is coeval with felsic magmatism and contemporaneous with a major pulse of orogenic gold mineralization in the Birimian Province of West Africa.