INCLUSIONES FLUIDAS Y DE FUNDIDOS EN XENOLITOS ULTRAMÁFICOS DEL NORTE DE LA PATAGONIA EXTRAANDINA

REMESAL MARCELA; SALANI FLAVIA; MONTENEGRO TERESITA

Acta Geologica Lilloana

Fundación Miguel Lillo

Lugar: San Miguel de Tucuman; Año: 2016 vol. 28 p. 219 - 223

0567-7513

Ultramafic xenoliths hosted in a basanitefrom Cerro Pilquiniyeu Chico, Río Negro, Extra-andean Patagonia, are studied. Textural andmineralogical relationships, fluid and solid inclusionsin pyroxene and olivine studied allowed us to obtaininformation (PT) of the xenoliths source, and itssubsequent evolution during ascent to the surface.Enclaves are lherzolites with varying grades ofmetasomatism. They are composed of different proportionsof pyroxene with exsolutions, olivine withdeformation and Fe-Ti-Cr spinel (Al poor), clinopyroxene-spinel simplectic intergrowths and spinelwith plagioclase rims. Mineralogical studies reveal aminimum P for the xenoliths source between 16and 18 kbar, estimated depth of depth 55- 60 kmand 1000 °C. Olivine and clinopyroxene are hostsfor different types of inclusions (glass, glass+CO2and CO2), which are unevenly distributed. Accordingto the CO2 density of pyroxene inclusions (forthe estimated T) the capture depth would be 36km. The CO2 density of inclusions in olivine indicatesthat the carbon fluid in olivine was trapped ata depth of 11 km. These CO2 density variations areattributed to modification and re-equilibration of theprimary composition during the ascent.