Caracterización petrográfica de las litologías de la unidad Plan del Oso.

Abstract

In this research the petrographic characterisation of the outcrops of the Plan del Oso Unit, located in southeastern Ecuador, in the province of Zamora Chinchipe, was conducted. For this purpose, field trips, samples descriptions, thin sections and X-ray diffraction were conducted. The results are presented by sectors, according to the data published in the 1: 100.000 geological maps of Zumba, Zamora, Las Aradas and Paquisha (IIGE, 2017). The main lithologies correspond to schists, phyllites and pelitic slates in the sectors of Ishimanchi, Chinapintza, San Francisco de Vergel, and the Quebradas de Chimbuza Wambuscaru; and migmatites and gneisses of quartz, muscovite, and biotite, in the Loma Plan de Oso sector and the Guaguayme creek. The schists with actinolite and quartzites with amphibole is also observed in the Guaguayme and Guambime sectors, respectively. The mineralogical analysis showed that the samples corresponds to the chlorite and biotite zones and belong to the green schist, amphibolite and transition facies between green schist and amphibolite. The protoliths corresponds mainly to pelitic rocks, however, there is also a volcanic contribution due to the presence of mafic minerals such as amphibole. By means of petrographic analysis, a continental environment can be interpreted for the rocks of the Plan del Oso Unit, which may correspond to the sub-Andean Units such as Ishimanchi, Chigüinda, and the protoliths of the Sabanilla unit.