Microstructures in xenoliths of postplateau basalts. Meseta de somún Curá. Río Negro Province

CERREDO, M.E. ; REMESAL, M B,

Buenos Aires

Conferencia; X Reunión sobre Microtectónica; 2000

FCEN - UBA

The Somún Curá basaltic plateau occurs in the northern extrandean Patagonia. The Tertiary volcanism of Somún Curá consists of extensive Oligocene olivine plateau basalts, the major part of the plateau is covered by younger alkali basalts, typically rich in xenoliths and xenocrystals. These post-plateau basalts enclose small (cm-scale) generally rounded xenoliths which may be grouped in two main suites: 1) a supracrustal or acid group, composed of quartz-feldspar assemblages, which display brittle-ductile deformation features and 2) a basic group of fairly uniform gabbroic composition. These show a span of microstructures which vary from mainly brittle to ductile in character. The xenoliths of supracrustal lithologies invariably show microstructures related to the brittle-ductile regime, with microcracking/frictional sliding and minor evidences of incipient recovery.