INVESTIGADORES
BERTOTTO Gustavo Walter
congresos y reuniones científicas
Título:
Oxygen isotopic signature of mantle xenoliths from the Patagonia region, Argentina.
Autor/es:
KOESTER EDINEI; MALLMANN GUILHERME; CONCEIÇÃO ROMMULO VIEIRA; MARIGA JEFFREY; BERTOTTO GUSTAVO WALTER; SCHILLING MANUEL; CHEMALE JR. FARID; CINGOLANI CARLOS ALBERTO
Lugar:
San Francisco (CA) EEUU
Reunión:
Congreso; AGU Fall Meeting 2003; 2003
Institución organizadora:
American Geophysical Union
Resumen:
In order to provide petrological information about the continental lithospheric mantle in the Patagonian region, a series of oxygen isotopic analyses were performed in mantle xenoliths. Hosted by Miocene-Pleistocene alkaline basalts erupted in the Andean back-arc setting, the studied mantle xenoliths are represented by anhydrous spinel-bearing lherzolites to harzburgites, and subordinately websterites and olivine websterites. Using a conventional vacuum extraction line employing BrF5, oxygen isotopic analyses were conducted in whole rock, olivine, clinopyroxene and orthopyroxene at the Department of Geological Sciences, Indiana University, Bloomington - USA. Isotopic ratios were measured on a Finnigan MAT 252 stable isotope mass spectrometer. Values of NBS-28 quartz are d 18O =  +9.6 ± 0.2 ‰. Errors obtained were better than ± 0.1 ‰ (2SD). Whole-rock data suggests a wide range of d18O from +5.5 to +10.1‰, whereas mantle rocks, in general, presented values ranging around 5.5 ± 0.2 ‰. Olivines showed two distinct isotopic ranges, with values of +5.0 to +5.9 ‰, similar to values for upper mantle olivines, but also low d18O values, around 3.2 ‰. Pyroxenes demonstrated a wide range of values, between +4.5 and +6.3 ‰ similar to upper mantle pyroxenes. The discrepancy of some whole-rock and olivine values in relation to mantle compositions could be interpreted as an inter-mineral disequilibrium, mineral zonation reflecting or not, metasomatic interaction, or even crust participation during subduction.