Caracterización de las anfibolitas del Complejo Metamórfico El Oro : caracterización petrográfica de las anfibolitas del Complejo Metamórfico El Oro (Ecuador).

Abstract

The goal of this research was to address the petrographic and geochemical vagueness of the outcrops of the metabasites of the El Oro Metamorphic Complex that make up the Arenillas, Río Panupali and Quebrada Plata units. The analyzed lithologies were amphibolites with amphibolite facies for the Arenillas unit whose mineralogy is hornblende + plagioclase ± opaque ± titanite ± zircon and relictic pyroxenes; greenschists with green schists facies to the Rio Panupali unit, with a paragenesis of actinolite + quartz + zoisite + epidote ± zircon ± rutile and amphibolites in green schists facies with a mineralogy of actinolite + plagioclase + epidote ± chlorite ± rutile ± opacos ± quartz and amphibolites in amphibolite facies whose mineralogy is hornblende + plagioclase + actinolite ± epidote ± titanite ± opacos. Mineralogical, textural and chemical characteristics distinguish the Arenillas from Quebrada Plata and Arenillas from Río Panupali units. Geochemical data of all metabasites indicated MORB type affinity with influence of a subduction zone. Thermobarometric estimates based on modal composition propose that the metamorphic conditions of the Arenillas Unit metabasites are ∼840-940 °K and ∼ 1200-4500 bar, while for the Quebrada Plata Unit are ∼750-900°K and ∼1700-3800 bar, that is, in conditions of moderate-high temperature and low pressure.