Tectono-metamorphic evolution of the Silgarل Formation metamorphic rocks in the southwestern Santander Massif, Colombian Andes

The Lower Paleozoic Silgará Formation in the southwestern Santander Massif was affected by Caledonian regional metamorphism, which created a sequence of metamorphic zones (sillimanite, staurolite, garnet, and biotite). The regional metamorphic grade of the Silgará Formation decreases southwestward from the sillimanite zone to the biotite zone. Metamorphism has occurred under low to high temperature and medium pressure conditions (Barrovian-type metamorphism) and reflects the high heat flow in this part of the Santander Massif. P–T conditions (495–518 °C and 4.4–5.5 kbar garnet zone; 590–612 °C and 6.6–7.5 kbar staurolite zone; 660–700 °C and 5.5–7.2 kbar sillimanite zone) were estimated by different thermometers and barometers. The Silgará Formation shows evidence of a complex metamorphic evolution characterized by crustal thickening during heating and a regional retrograde metamorphism after the peak metamorphic temperature.