Geological characteristics of the schist unit of the Arquía Complex, west of Manizales in the La Manuela and Lisboa sector, Colombia

Abstract

On the western flank of the Colombian Cordillera Central, west of the city of Manizales, outcrop the Lisboa - Palestina Schists belonging to the Arquia Complex. This unit consists of centimetric to metric intercalations of green and graphitic schists. This paper seeks to determine the deformational phases of the schist’s unit, its protolith, and its associated geological environment. Petrography establishes mineral associations of actinolite + chlorite + epidote + epidote + clinozoisite + plagioclase ± titanite for the green schists and chlorite + titanite + clinozoisite + muscovite + quartz + graphite for the graphitic schists. There are two metamorphic surface phases and two deformation phases, the first one corresponds to the event (S_n), followed by the main foliation (S_n+1). The deformation phase (D_n+2) corresponds to the folding of the main foliation and the last phase to a superimposed ductile deformation. The protolith of the green schists are basalts and andesites of toleitic affinity, with a geochemical signature of N-MORB type. Based on geochronological data and geo-tectonic analysis, it is estimated that the Lisboa - Palestina Schists were metamorphosed in the Lower Cretaceous during a subduction process under an island arc, with subsequent accretion onto the northwestern Colombian paleomargin and the beginning of the Romeral Fault System.