Abstract

GARCIA-RAMIREZ, Carlos Alberto; ARIZA-ARDILA, Valeria; MANTILLA-FIGUEROA, Luis Carlos  and  CABANZO-HERNANDEZ, Rafael. Thermal structure of metamorphic rocks sequence outcropping in the Mogotes-San Joaquín sector, southwestern of Santander Massif, Colombia. Bol. geol. [online]. 2024, vol.46, n.1, pp.33-45.  Epub Oct 04, 2024. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v46n1-2024002.

In the Mogotes-San Joaquín sector (SW of the Santander Massif) a succession of metamorphic rocks emerges, cut by igneous rocks and partially covered by sedimentary rocks, with ages from the pre-Cambrian to the Mesozoic. These lithological varieties are affected by families of faults, among which the Mogotes Fault with a NW-SE direction stands out. This fault defines the thermal structure of the present metamorphic succession, since it brings into contact two contrasting metamorphic sequences in degree of metamorphism and age. To the north of the Fault, a sequence of metamorphic rocks with a higher degree of metamorphism (phyllites, quartzites and graphitic schists) outcrops, pre-Cambrian age, with the presence of newly formed biotite. To the south of the Fault, lower grade metamorphic rocks emerge, with a phyllitic appearance, with a maximum depositional age of the Early Devonian and that are part of the metamorphosed Floresta Formation. Other rocks in the area correspond to impure metalimestone, metalimestone, metasandstone, and metagraywacke lithologies, with ages from Middle Devonian to Permo-Carboniferous. The lithologies both north and south of the Fault are cut by igneous rocks of Late Triassic-Early Jurassic age, which extend across the Santander Massif. Three metamorphic events affected the rocks north of the Mogotes Fault. Event M1 of regional character, with metamorphic peak in greenschist facies, biotite zone (458°C in graphite shale, temperatures obtained through the analysis of microraman spectra in graphite). Event M2 of contact metamorphism, in amphibolic corneal facies with cordierite and biotite as minerals of the metamorphic peak. Event M3, corresponding to a dislocation metamorphism. The metamorphic rocks south of the Mogotes Fault are characterized by the absence of biotite and metamorphism temperatures lower than 410°C.

Keywords : Metamorphic rocks; Microraman spectroscopy; Mogotes Fault; Mogotes-San Joaquín; Santander Massif.

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