Mineralogía y trayectoria textural de anfibolitas de la Sierra de Bachicha, Sistema de Tandilia (Buenos Aires).

GONZÁLEZ, PABLO D.; CÁBANA, MARÍA CECILIA

Buenos Aires

Congreso; 8º Congreso de Mineralogía y Metalogenia (8º MINMET); 2006

Asociación Argentina de Mineralogía

In the Sierra de Bachicha (Tandilla System), at Punta Tota (37°49’S, 58°12’W), relics of medium pressure mafic granulites have been described as inclusions within amphibolites of the Buenos Aires Complex. At least four regional metamorphic events have been recognized: (1) Relict M1 medium pressure granulite facies metamorphism characterized by granoblastic opx-cpx1-pl1 assemblage (2) Peak metamorphic conditions at M2 high amphibolite facies, with nematoblastic am1-cpx2-pl2 and coronitic reaction textures of am1 around M1 assemblage. (3) Retrograde M3 low amphibolite facies metamorphism characterized by am2 + brown mica. (4) M4 prhenite-pumpellite facies metamorphism, with pmp-prh-ab-ep-chl-cal overprinting pl1-2 + am1-2. Mineral and textural analyses suggest that the mafic metamorphic rocks follow a general retrogressive P-T-time path from M1, with decompression contemporaneous with cooling and hydration, up to M4.