Alteration patterns in the Umm Rus gold mine area, Eastern Desert, Egypt
Mineralogical studies reveal that the common alteration minerals in the Umm Rus gold mine are chlorite, epidote, sericite and carbonates. The carbonates are mainly calcite and ankerite. Sulphidization is a common process, while silicification is the most intensive alteration process in the study are...
Elmentve itt :
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| Dokumentumtípus: | Cikk |
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University of Szeged, Department of Mineralogy, Geochemistry and Petrology
Szeged
1996
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| Sorozat: | Acta mineralogica-petrographica
37 |
| Kulcsszavak: | Kőzettan, Ásványtan, Földtan |
| Tárgyszavak: | |
| Online Access: | http://acta.bibl.u-szeged.hu/24833 |
| Tartalmi kivonat: | Mineralogical studies reveal that the common alteration minerals in the Umm Rus gold mine are chlorite, epidote, sericite and carbonates. The carbonates are mainly calcite and ankerite. Sulphidization is a common process, while silicification is the most intensive alteration process in the study area. Four alteration zones are encountered; chlorite-epidote, sericite-chlorite, sericite-ankerite-chlorite-sulphides and quartz-carbonatessulphides zones. The textural relationship between the alteration minerals indicate that chlorite and epidote were formed firstly, followed by sericite and then by ankerite and sulphides. All the studied mineral phases were affected by silicification. The distribution of the studied alteration, phases indicates that the affecting hydrothermal solutions were enriched in H2O and CO2 in different proportions. Elements such as K, S, As, Zn, Pb, Cu and Au are added to the system during the alteration events. On the basis of the combined geological, mineralogical and geochemical data, four alteration stages are envisaged: a) The hydrothermal fluids invaded the rocks through N-S shear zones. At the beginning, these fluids were characterized by low CO1/H2O ratio which enhanced the alteration of the biotite to chlorite and epidote. The geothermometry of the studied chlorite proves a temperature of formation of about 225°C. b) The fluids then, became enriched in K after the breakdown of biotite. These fluids reacted with feldspars to form sericite. c) After the formation of chlorite, epidote and sericite, the CO1/H2O ratio in the fluids became high and consequently ankerite was originated during this stage. Also, sulphides were concomitant with conspicuous concentration of Fe, As, Cu and Au. d) The last stage is characterized by a severe silicification of the previously formed minerals and the formation of quartz veins. All the preceeding stages were affected by this silicification. The SiOi-rieh solution most probably remobilized the gold from sulphides (pyrrhotite) in the gabbroic rocks adjacent the granodiorite and then redistributed this gold in some other sulphide phases e. g. pyrite and pyrrhotite forming during stage c. |
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| Terjedelem/Fizikai jellemzők: | 51-74 |
| ISSN: | 0365-8066 |