Depleted lithospheric mantle beneath Tres Lagos, Patagonia.

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

Florencia

Congreso; 32nd International Geological Congress; 2004

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;} --> Mantle xenoliths were found in the post-plateau lavas from Tres Lagos in southern Patagonia. These lavas, belonging to the Meseta de la Muerta, 49.5 °S, are believed to be linked with asthenospheric slab window processes associated with the collision of a Chile Ridge segment with the Chile Trench (Gorring and Kay 2001). The collected mantle xenoliths are anhydrous spinel harzburgites with subordinate spinel lherzolites and dunites. The whole-rock Al2O3 (2.82-0.30 wt%) and CaO (2.91-0.38 wt%) contents are negative correlated with mg# suggesting different degrees of partial melting of a primitive mantle source. Similar, decreasing Al and Ti contents with increasing mg# in clinopyroxenes suggest also a control by partial melting.