Geochemistry of the cenozoic basalts from Gregores area, Santa Cruz. Argentina.

LABUDIA, C; NTAFLOS, TH; BJERG, E A

Calafate

Congreso; XV Congreso Geológico Argentino; 2002

The hills of La Huerta and Valle Fertil, wich belong to the Western Pampean Ranges in the Province of San Juan, NW Argentina, mainly consist of metagabboic to metadioritic rocks that intruded the Proterozoic basement in the Early Middle Ordovician (Famat <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:21.0cm 842.0pt; margin:70.9pt 3.0cm 70.9pt 3.0cm; mso-header-margin:35.45pt; mso-footer-margin:35.45pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Several authors (Baker et aI., 1981, Stern et ai., 1990, 1996, Skewes and Stern, 1979, Ramos and Kay, 1992, Gorring et al. , 1997) have studied the Cenozoic volcanic rocks located in southern Patagonia, Argentina. Skewes and Stern (1979) attributed the origin of the alkali basalts to the mechanical and/or thermal perturbation of the subcontinental mantle due to the eastward subduction of the Pacific oceanic lithosphere and not to continental rifting or hot-spot traces. A model proposing that Patagonian basaltic magmatism was induced by an eastwards migrating "slab-window" was advanced by Ramos and Kay (1992), Gorring et al. (1997) and Gorring and Kay (2001). According to Cande et al. (1986, 1992) and Baker et al. (1981) large volumes of OIB-like lavas dating from 12-7 Ma, occurring between 46°S and 49°S are the result of the upwelling of sub-slab asthenosphere through a huge gap ("window") in the subducted plate in the area of the Chile Triple Junction. Stern et al. (1990) concluded that Pliocene and Pleistocene alkali basalts in the East of Patagonia are characterized by OIB-like geochemistry, whereas lavas in the West have been influenced by subduction.