INGEOSUR   20376
INSTITUTO GEOLOGICO DEL SUR
Unidad Ejecutora - UE
capítulos de libros
Título:
The Tajo Largo Gold Deposit, Argentina – Mineralogy and Fluid Inclusions Study.
Autor/es:
AVILA, J.C.; BENGOCHEA, L.; FOGLIATA, A.; MAS, G ;LAZARTE, J.E
Libro:
ICAM 2008
Editorial:
Australasian Institute of Mining and Metallurgy
Referencias:
Lugar: Brisbane, Australia; Año: 2008; p. 588 - 593
Resumen:
The Culampajá auriferous district is located in the northern sector of the eastern edge of the homonymous hill, Catamarca Province, Argentina. Tajo Largo mine is situated in the southern flank of Las Minas gulch at an approximate height of 3.600 m a. s. l. In the studied area main outcrops are orthogneiss rocks of Chango Real Formation. The ore mineral is native gold with a lesser amount of pyrite, chalcopyrite, hematite, limonite, malachite, azurite and covellite. These ore mineral assemblages are disseminated in quartz veins filling tension fractures in the host orthogneiss. Several types of inclusions have been recognized, including three phase H2O–CO2liq.-CO2vap. inclusions, polyphase inclusions with H2O-CO2 and one or more solid phases, and two phase aqueous inclusions. In the three phase H2O–CO2liq.-CO2vap inclusions the Tmclath is about 1ºC and the CO2 liquid-vapour homogenization occurs at about 26-28ºC, to liquid phase. The homogenization temperature of H2O-CO2 occur at about 365-380ºC, in the aqueous phase. This set of data defined a solution with a salinity of 14, 4 wt % NaCl equiv and a density of 0.84 g/cm3. In the two phase aqueous inclusions the melting temperature (Tm) of -5.4ºC and the eutectic point (Te) in -38ºC indicates a salinity of about 7.5 wt. % NaCl equiv., with the probable presence of Ca2+. Density of fluid is about 0.83g/cm3. Homogenization temperature ranges between 260º and 280ºC. The pressure, temperature and salinity of fluids in the polyphase inclusions suggest an early fluid of high density and high salinity. The three-phase fluid inclusions may be the result of an unmixing-phase separation of post magmatic hydrothermal fluid due to pressure decrease along fractures. It is suggested that the deposit was formed during the late magmatic hydrothermal stage genetically liked to granitic rocks and can be comparable with intrusion-related gold system of Baker (2003).