Mineral chemistry and geochemical behavior of hydrothermal alterations associated with mafic intrusive-related Au deposits at the Atud area, Central Eastern Desert, Egypt


Khalıl A. A. A., Kumral M.

ORE GEOLOGY REVIEWS, vol.77, pp.1-24, 2016 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 77
  • Publication Date: 2016
  • Doi Number: 10.1016/j.oregeorev.2016.01.011
  • Journal Name: ORE GEOLOGY REVIEWS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1-24
  • Keywords: Hydrothermal alteration geochemistry, Mineral chemistry, Atud gold deposit, Egypt, VOLCANIC-ROCKS, GRANITIC-ROCKS, GOLD, SERIES, MICAS, PLOT, AGES
  • Istanbul Technical University Affiliated: Yes

Abstract

Vein-type gold deposits in the Atud area are related to the metagabbro-diorite complex that occurred in Gabal Atud in the Central Eastern Desert of Egypt. This gold mineralization is located within quartz veins and intense hydrothermal alteration haloes along the NW-SE brittle-ductile shear zone, as well as along the contacts between them. By using the mass balance calculations, this work is to determine the mass/volume gains and losses of the chemical components during the hydrothermal alteration processes in the studied deposits. In addition, we report new data on the mineral chemistry of the alteration minerals to define the condition of the gold deposition and the mineralizing fluid based on the convenient geothermometers. Two generations of quartz veins include the mineralized grayish-to-white old vein (trending NW-SE), and the younger, non-mineralized milky white vein (trending NE-SW). The ore minerals associated with gold are essentially arsenopyrite and pyrite, with chalcopyrite, sphalerite, enargite, and goethite forming during three phases of mineralization; first, second (main ore), and third (supergene) phases. Three main hydrothermal alteration zones of mineral assemblages were identified (zones 1-3), placed around mineralized and non-mineralized quartz veins in the underground levels. The concentrations of Au, Ag, and Cu are different from zone to zone having 25-790 ppb, 0.7-69.6 ppm, and 6-93.8 ppm; 48.6-176.1 ppb, 0.9-12.3 ppm, and 39.6-118.2 ppm; and 53.9-155.4 ppb, 0.7-3.4 ppm, and 0.2-79 ppm for zones 1, 2, and 3, respectively.