The backarc Patagonia mantle underwent pervasive regional re-crystallisation that left only remnants of the pre-existing mantle. Anhydrous xenoliths (dominantly lherzolites and harzburgites, few dunites) are predominant. Xenoliths containing hydrous phases (Iherzolites and harzburgites, rare wehrlites) abundantly occur only at G. Gregores. Bulk-rock and clinopyroxene trace element patterns range from predominant LREE-depleted, LILE-enriched and variably Nb-depleted, to LREE-enriched patterns, with negative Zr, Hf and Ti spikes when amphibole is present. V-shaped trace element patterns are found only in rare non-recrystallised xenoliths. Trace element abundances in potential melts calculated from clinopyroxene are similar to arc magmas, but in southern Patagonia fade eastwards to EMORB-like compositions. Trace element characteristics of bulk-rock and pyroxenes are interpreted as the consequence of two processes: (1) melting in the region of thermal inversion of the wedge, triggered by infiltration of hydrous components; (2) reactive porous flow of the melts into the overlaying mantle. The component triggering melting is inferred to be slab-derived in the western occurrences and a garnet-facies, asthenosphere-derived melt in the eastern occurrences as a consequence of wedge thickening. Differences between northern and southern Patagonia are interpreted to be due to variable contribution of slab components to the wedge. Compared to the southern region, slab-derived melts are tentatively attributed to the subduction of older and colder segments of the Nazca plate in the North.

The backarc mantle lithosphere in Patagonia, South America / Rivalenti, Giorgio; Mazzucchelli, Maurizio; Laurora, Angela; Ciuffi, Sia; Zanetti, A; Vannucci, R; Cingolani, Ca. - In: JOURNAL OF SOUTH AMERICAN EARTH SCIENCES. - ISSN 0895-9811. - STAMPA. - 17:(2004), pp. 121-152.

The backarc mantle lithosphere in Patagonia, South America

RIVALENTI, Giorgio;MAZZUCCHELLI, Maurizio;LAURORA, Angela;
2004

Abstract

The backarc Patagonia mantle underwent pervasive regional re-crystallisation that left only remnants of the pre-existing mantle. Anhydrous xenoliths (dominantly lherzolites and harzburgites, few dunites) are predominant. Xenoliths containing hydrous phases (Iherzolites and harzburgites, rare wehrlites) abundantly occur only at G. Gregores. Bulk-rock and clinopyroxene trace element patterns range from predominant LREE-depleted, LILE-enriched and variably Nb-depleted, to LREE-enriched patterns, with negative Zr, Hf and Ti spikes when amphibole is present. V-shaped trace element patterns are found only in rare non-recrystallised xenoliths. Trace element abundances in potential melts calculated from clinopyroxene are similar to arc magmas, but in southern Patagonia fade eastwards to EMORB-like compositions. Trace element characteristics of bulk-rock and pyroxenes are interpreted as the consequence of two processes: (1) melting in the region of thermal inversion of the wedge, triggered by infiltration of hydrous components; (2) reactive porous flow of the melts into the overlaying mantle. The component triggering melting is inferred to be slab-derived in the western occurrences and a garnet-facies, asthenosphere-derived melt in the eastern occurrences as a consequence of wedge thickening. Differences between northern and southern Patagonia are interpreted to be due to variable contribution of slab components to the wedge. Compared to the southern region, slab-derived melts are tentatively attributed to the subduction of older and colder segments of the Nazca plate in the North.
17
121
152
The backarc mantle lithosphere in Patagonia, South America / Rivalenti, Giorgio; Mazzucchelli, Maurizio; Laurora, Angela; Ciuffi, Sia; Zanetti, A; Vannucci, R; Cingolani, Ca. - In: JOURNAL OF SOUTH AMERICAN EARTH SCIENCES. - ISSN 0895-9811. - STAMPA. - 17:(2004), pp. 121-152.
Rivalenti, Giorgio; Mazzucchelli, Maurizio; Laurora, Angela; Ciuffi, Sia; Zanetti, A; Vannucci, R; Cingolani, Ca
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/306811
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