The volcanic association of Las Lomadas area, Corona Chico Volcanites. Somún Curá Magmatism. Río Negro province, Argentina

Marcela Remesal,Maria Cerredo,Pablo Cordenons,Juan Albite

doi:10.22179/revmacn.21.635

Marcela Remesal, Maria Cerredo + Show 2 more

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https://doi.org/10.22179/revmacn.21.635

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Abstract

This contribution deals with the Corona Chico Vulcanites, within the Somun Cura Magmatic Province, northern Extra-Andean Patagonia. The studied area is located to the north of the Alta Sierra de Somun Cura Volcanic Complex and is made of several basaltic volcanic buildings of varied morphologies: spatter cones, tuff ring and long lava flows related to small shield volcanoes (of scutulum type). Petrographic characteristics as well as whole rock chemical composition suggest a time progressive increase in alkalis content and a shift from early transitional terms to basanitic rocks in the latest stages. A simulation of the source yielded for Las Lomadas rocks an astenospheric source in the garnet-spinel facies, with associated low partial melting percentages (< 7-8%). Within the studied rock set, the spatter cones sequence displays geochemical affinities with the basaltic component of Alta Sierra de Somun Cura Volcanic Complex.

Highlights

This paper deals with the petrography and geochemistry of the volcanic rocks of Las Lomadas area, which is included within the Corona Chico Vulcanites (CChV) in Río Negro Province
Group or the siliceous volcanic rocks of Marifil Complex (Remesal et al, 2018b; Franchi et al, 2001 and references therein). This contribution is devoted to a restricted sector of the CChV; we focus on Las Lomadas area, located to the north of the Alta Sierra de Somún Curá Volcanic Complex (ASSCVC) (Figure 1c) and mostly composed of basaltic lavas with subordinated pyroclastic component
Clastogenic basaltic lavas are porphyric with olivine microphenocrysts of around 0.3 mm showing high temperature iddingstite (HTI), accompanied by a set of crystals displaying variable degrees of disequilibrium: rounded crystals of clinopyroxene and plagioclase; plagioclase often show sieve-textured cores, in other cases subgrains; orthopyroxene rimmed by a thin ring either of olivine or olvine-clinopyroxene

Summary

Introduction

This paper deals with the petrography and geochemistry of the volcanic rocks of Las Lomadas area, which is included within the Corona Chico Vulcanites (CChV) in Río Negro Province. Clastogenic lavas are banded and brecciated (with eutaxitic texture, Figure 3a), porphyric with olivine microphenocrysts with Low Temperature Iddingsite (LTI), and larger light brown clinopyroxene, plagioclase and orthopyroxene crystals displaying variable degrees of disequilibrium.

Results

Conclusion