Hydrothermal evolution of granitoid-hosted gold mineralization in Gidami area: an example for orogenic-gold deposits in Egypt

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14310%2F18%3A00105838" target="_blank" >RIV/00216224:14310/18:00105838 - isvavai.cz</a>

Result on the web

<a href="https://www.sciencedirect.com/science/article/pii/S1464343X18301055?via%3Dihub" target="_blank" >https://www.sciencedirect.com/science/article/pii/S1464343X18301055?via%3Dihub</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.jafrearsci.2018.04.007" target="_blank" >10.1016/j.jafrearsci.2018.04.007</a>

Result language

angličtina

Original language name

Hydrothermal evolution of granitoid-hosted gold mineralization in Gidami area: an example for orogenic-gold deposits in Egypt

Original language description

The Gidami gold ore is a unique form for the orogenic-gold deposits in Egypt. The gold lode is found in the form of auriferous quartz veins and aplitic dikes, cut through hosting granitic rocks and probably extend into the neighbor metavolcanic rocks. The geochemical data revealed that the granitic rocks are of tonalite-granodiorite composition, show talc-alkaline nature and related to active continental margin (syn-orogenic). The ore body is controlled by NNW trending shear/fault zones, occupying fracture zones and fissures and dipping generally to East direction. Microscopic examination accompanied with Electron Microprobe Analyses revealed that, the existed sulfide minerals are (pyrite, sphalerite, chalcopyrite, molybdenite, pyrrhotite, covellite, Galena, and pentlandite). Ilmenite and goethite are the main oxide minerals. Native gold commonly occurs as small inclusions within pyrite and goethite, and also detected as tiny grains scattered within quartz vein (near the sulfides). Well-developed alteration zones occur associated with auriferous quartz veins; two types of wallrock alteration are distinguished: a) Inner (phyllic) alteration zone, and b) Outer (carbonatized) alteration zone. The outer alteration zone always exhibits higher gold content than the inner zone. Three types of fluid inclusions are recognized at the core and rim of the auriferous quartz vein as follows: 1) Two phases aqueous (H2O NaCl +/- KCl), 2) Two phases aqueous (H2ONaCl +/- MgCl2), and 3) Three phases aqueous-carbonic (H2O-NaCl-CO2 +/- CH4) fluid inclusions. Isochores intersection from fluid inclusions data outlines that, the Gidami gold deposits are of the mesothermal type formed at temperatures range between (270-300 degrees C), and pressure (750-850 bar) corresponds to a depth around 3 km (assuming pure lithostatic pressure): The-ore-bearing fluids are supposed to-be sourced mainly-by fluids of metamorphic and meteoric origin. However, criteria of partial mixing with water of magmatic signatures has been proposed during fluid evolution. The transportation of gold was in form of bisulphide compounds in moderately reduced, neutral to weakly alkaline environment and then the precipitation occurred as a result of changing in Eh and pH conditions.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

—

Continuities

S - Specificky vyzkum na vysokych skolach

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

JOURNAL OF AFRICAN EARTH SCIENCES

ISSN

1464-343X

e-ISSN

1879-1956

Volume of the periodical

146

Issue of the periodical within the volume

SI

Country of publishing house

GB - UNITED KINGDOM

Number of pages

18

Pages from-to

132-149

UT code for WoS article

000447568000010

EID of the result in the Scopus database

2-s2.0-85054608621