INENCO   05446
INSTITUTO DE INVESTIGACIONES EN ENERGIA NO CONVENCIONAL
Unidad Ejecutora - UE
artículos
Título:
The Early Palaeozoic high-grade metamorphism at the active continental margin of West Gondwana in the Andes (NW Argentina/N Chile)
Autor/es:
LUCASSEN, F.,; BECCHIO, R.; FRANZ, G.
Revista:
INTERNATIONAL JOURNAL OF EARTH SCIENCES
Editorial:
SPRINGER
Referencias:
Lugar: Berlin, Alemania; Año: 2010 p. 137 - 156
ISSN:
1437-3254
Resumen:
The evolution of the Early
Palaeozoic orogen of West Gondwana in the Cambrian to Ordovician basement of
the Andes between *18_ and 32_ S is investigated for pressure and temperature
conditions and age of metamorphism. It is characterized by mid-crust
temperaturas commonly above the wet granite solidus (*650_C). Widespread felsic
migmatite and rare granulite formed at pressures of ca 0.50.7 GPa, locally 1.0
GPa. These rocks represent the deepest exhumed sections of the Early Palaeozoic
crust. High pressurelow temperature rocks are absent. The crystallization
ages, compiled from the literatura in combination with new data, for near peak
metamorphic conditions of these high-grade metamorphic rocks in NW Argentina
and N Chile are *530500 Ma and *470420 Ma. Both age groups are spatially
overlapping. Radiogenic isotope signatures (Sr, Nd, Pb) are used to
characterize the Early Palaeozoic basement. The Pb and Sr isotope compositions
of the Early Palaeozoic basement indicate mixing arrays between pre-Palaeozoic
unradiogenic and radiogenic crust. Crustal residence ages (SmNd TDM)
indicate a prominent event of crust formation around *2 Ga, which is known
continent-wide. This material was recycled during Midproterozoic and Early
Palaeozoic orogenies without prominent additions of new crust present in the
isotope record, i.e. accretion of compositional exotic material is absent.