Sr, Nd, Pb and Hf isotopic constraints on mantle sources and crustal contaminants in the Payenia volcanic province, Argentina.

Soager, Nina, Holm, Paul Martin and Thirlwall, Matthew F. (2015) Sr, Nd, Pb and Hf isotopic constraints on mantle sources and crustal contaminants in the Payenia volcanic province, Argentina. Lithos, 212-215 . pp. 368-378. DOI 10.1016/j.lithos.2014.11.026.

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Abstract

The presented Sr, Nd, Hf and double-spike Pb-isotopic analyses of Quaternary basalts from the Payenia volcanic province in southern Mendoza, Argentina, confirm the presence of two distinct mantle types feeding the Payenia volcanism. The southern Payenia mantle source feeding the intraplate-type Rio Colorado and Payun Matru volcanism is isotopically distinct from the northern Payenia and arc mantle source with less radiogenic Pb and lower Sr-87/Sr-86 and Hf-176/Hf-177 for a given Nd-143/Nd-144 than the northern Payenia and arc rocks. The basalts from the northern Payenia province (Nevado volcanic field) and the retroarc zone have isotopic compositions overlapping the Andean southern volcanic zone (SVZ) arc rocks and they are probably derived from the same metasomatized South Atlantic N-MORB-like mantle source. A high field strength element melting model suggests addition of similar to 1-2% upper continental crustal material to the mantle source of the Nevado basalts and the transitional SVZ arc and retroarc rocks and similar degrees of melting throughout this arc segment. A gradual depletion of the pre-metasomatic mantle source going from the backarc over the retroarc to the arc is indicated. The depletion is suggested to be caused by step-wise melt extraction due to repeated injections of subduction zone fluids and melts.

The lower crustal contamination trends found in the trace element variations of basalt groups from all parts of the Payenia province are also recognized in isotopic space and the dominant isotope assimilation trends indicate lower crustal contaminants with more unradiogenic Pb, lower Nd-143/Nd-144 and Hf-176/Hf-177 and higher or similar 87Sr/86Sr as the mantle melts. These characteristics are similar to those found in lower crustal xenoliths from the northern Proterozoic Cuyania terrane, and the Payenia basalts may have been contaminated by this type of crust during passage through the lithosphere or by more recently underplated or intruded material.

Document Type: Article
Additional Information: WOS:000348879200025
Keywords: Isotopes; Backarc basalts; Intraplate basalts; Crustal contamination; Sub-arc enrichment
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Date Deposited: 06 Mar 2015 10:02
Last Modified: 13 Sep 2017 08:10
URI: https://oceanrep.geomar.de/id/eprint/27888

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