PETROGRAFÍA Y MINERALOGÍA DE LOS DIQUES MÁFICOS DEL RIO MALLÍN (VALLE DE PUNILLA, CÓRDOBA)

ASSADOUR TOROSSIAN; FERNANDO COLOMBO; ALANA MINA; EDGARDO G.A. BALDO

Tucuman

Congreso; XX Congreso Geológico Argentino; 2017

Asociación Geológica Argentina

Four mafic dikes were found intruded in equigranular to mildly porphyritic granite belonging to the Achala batholith (Córdoba, Argentina, coordinates 31°18´51´´ S - 64°30´41´´ W). These dikes, which have a combined length of 110 m, strike 15-20ºN and dip 85º W. They are intruded in a fracture system, defining an échelon pattern.The basaltoid (no whole rock chemical analyses are yet available for a more precise classification) is blackish grey with holocrystalline fluidal microlitic texture. The primary paragenesis comprises plagioclase laths (the most calcic core gives Ab48An48Or4), biotite [Mg/(Mg+Fetotal)molar  0.40], potassic feldspar, ilmenite, magnetite (with ilmenite and ulvöspinel exsolutions) and fluorapatite. There is a pervasive hydrothermal overprint that is reflected by sodic plagioclase (up to Ab98.5An0.5Or0.5) surrounding relic calcic cores, chlorite after biotite, epidote and calcite as vug fillings. Sulfides (sphalerite, pyrite, pyrrhotite, chalcopyrite and an Ag-Pb-Bi sulfide, probably ourayite), occur as m-sized crystals scattered in plagioclase or2quartz xenocrysts. The basaltoid also contains xenoliths of granitoid rocks and xenocrysts of plagioclase, quartz, ilmenite and amphibole.Field and petrographic features suggest that these dikes could belong to the same intrusive event as those from Cabalango, distant about 9.9 km in SSW direction, which have been interpreted as related to the Upper Carboniferous distension that affected this area of Gondwana