Petrology and structure of the Cóndor Huasi Pluton, Sierra del Tigre, Province of Córdoba: a syntectonic leucomonzogranite with garnet and tourmaline

Abstract

The Cóndor Huasi pluton outcrops to the west of the Sierras Pampeanas of Córdoba, with a tabular-curved shape (major axis N 330º) and concordant with the S₂ foliation of the banded schists country-rocks. It is composed of two facies, coarse and fine, of muscovitic leucomonzogranites with biotite, apatite, garnet and tourmaline. The garnet (Sps_36-43Grs_32-36Alm_21-28Py_0-1) is xenolithic, with a deep metamorphic core and a reequilibrated rim in the magmatic setting of the granite. Considering the primary biotite, the crystallization temperature would be ~ 631 ºC. The internal structure of the pluton shows two foliations. Si₁ is a primary magmatic flow foliation, materialized by the planar orientation of xenoliths and enclaves, and by the network of feldspars in the granite. Si₂ is a secondary foliation, produced by subsolid deformation, between ~ 650-700 °C and ~ 400-250 °C. The emplacement was syntectonic on the eastern flank of a major type 1C fold, with an axial plane of S₃ cleavage, expressed as fan-shaped fractures in the pluton. Si₂, parallel to S₃, was a shear flattening plane during folding. Geochemically, the granite is moderately peraluminous and calc-alkaline, rich in K, with high SiO₂ contents, strongly differentiated and sincollisional. By comparison with similar minor plutons of the Sierras Pampeanas Orientales, such as the nearby La Yeya Norte pluton and the Los Alanices pluton of the low-temperature Ordovician Series of Granites and Granodiorites of the Sierra de San Luis, it would be related to the Famatinian Orogenic Cycle. However, the emplacement on the eastern flank of a major fold formed by Neoproterozoic banded schists suggests an older age.