Metallogeny of Culampajá Gold District, Argentina (Extended Abstract)

AVILA, JULIO CESAR; LAZARTE, JOSÉ ENRIQUE

Trondheim

Congreso; 10th International Congress for Applied Mineralogy (ICAM); 2011

International Council for Applied Mineralogy

In Northwestern territories of Argentina there are mining districts that have contrasted styles of gold mineralization, one of the most irnportant is the Culampajá district located in the northern sector of the eastern edge of the homonymous hill, Catamarca Province, Argentina. The geographical coordinates of the midfield are 26° 68'S and 66° 58' W at an approximate height of 3600m a.s.l.The gold mining district belongs to Sierras Pampeanas Occidentales morphostructural province. The basement is conformed by metasedimentary and granitic rocks inferred to be Precambrian - Early Palaeozoic age. In the southern sector of the Altohuasi hill granitic stock crops out (Papachara granite) that intruded metamorphic rocks and orthogneiss. The Papachacra granite is inferred to have Carboniferous age.In the Culampajá district more than 15 auriferous lodes outcrops have been recognized in an área of approximate 70 km2. From the north to the south the following ones are mentioned: La Chiruza, La Rosario,Moradito group (Gutiérrez, Tajo Largo, Moradito, el Ingenio), La Anciana, La Sarna group (Sarna I, Sarna II,Sarna III), Paredez, Viento Blanco and La Alumbrera group (Cabra Caja, Cástulo, Fabio, Alumbrera). Most of them have been discontinuously mined underground and opencast during the last Century.Their gold grades ranges from 1 to 34 g/t. At the current level of knowledge, the veins of the Moradito group are the most irnportant.In the district site outcrop are mainly of orthogneiss rocks which host severa! deposits. There are also small outcrops of rocks similar to Papachacra granite that intruded the orthogneiss with sharp contacts. Mineralisation is in the form of quartz veins located in tensión fractures of Chango Real rocks.Generally vein strike is 90° N with subvertical dip. Some of them are up to hundreds of metres long and their thickness ranges from 0.90 to 1 m. Veins have tabular shapes with scarce variations in its strike and dip. The ore assemblage is native gold, pyrite and chalcopynte. Sphalerite and arsenopyrite are also observed, The wall rock of the quartz veins shows two types of hydrothermal alteration: a weak selective pervasive alteration and a pervasive potassic alteration. Fluid inclusions of La Chiruza and Tajo Largo lodes have been studied. The pressure, temperature and salinity of fluids in the polyphase inclusions suggest an early fluid of high density and high salinity.On the basis of the alteration pattern and rnineralogy together with the high temperature, high salinity characteristics of fluids inclusions, it is suggested that the auriferous mineralization of Culampajá district ís a product of post-magmatic hydrothermal fluids linked with granitic bodies inferred to have Carboniferous age comparable with the intrusion-related gold system.