Evolución estructural del complejo ígneo Huaco, Sierra de Velasco, La Rioja

MACCHIOLI GRANDE, MARCOS; ALASINO, PABLO H.; ROCHER, SEBASTIÁN; LARROVERE, MARIANO A.; DAHLQUIST, JUAN A.; REINOSO CARBONELL, VIRGINIA

San Miguel de Tucuman

Congreso; XX Congreso Geológico Argentino; 2017

Universidad Nacional de Tucumán

The Huaco Igneous Complex is one of several Early Carboniferous granitic massifs emplaced at shallow levels that outcrop in Sierras Pampenas (NW Argentina). It comprises three plutonic units, named Huaco, Sanagasta and La Chinchilla. Huaco and Sanagasta units are porphyritic biotite monzo to syenogranites emplaced in Ordovician-Silurian metamorphic rocks. La Chinchilla unit is a monzogranite that intrudes Huaco unit. The latter shows discordant relationships with the host rock fabrics in sharp contacts in the north, as medium to shallow-dipping shets, generating an interdigited pattern. Host rock fabrics near contact keep NW.SE regional foliation. Conversely, the Sanagasta unit exhibits vertical contacts with the mylonites in the SW region, which occur as concordant anastomesed sheets. Moreover, in the SE of this unit, the host rock nearby the contact is locally deflected. Numerous blocks of mylonites apper in both units. La Chinchilla units shows sharp discordant relations whith Huaco unit. The observed features allow us to propose a fragile emplacemet mechanism for both Huaco and La Chinchilla units, developing a tabular geometry. Sanagasta unit, in contrast, reveals a fragile-ductile emplacement style which leads to a cylindrical body. This switch in the emplacement style is due the Huaco unit intruding a relatively cold crust and Sanagasta unit emplacing in thermally mature system. Later, after 10 My of magmatic inactivity, the upper crust returns to normal thermal conditions and La Chinchilla unit intrudes in a fragile manner.