Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

Hf-Nd isotope variation in Mariana Trough basalts: the importance of "ambient mantle" in the interpretation of subduction zone magmas

Woodhead, Jon, Stern, Robert J., Pearce, Julian A., Hergt, Janet and Vervoort, Jeff 2012. Hf-Nd isotope variation in Mariana Trough basalts: the importance of "ambient mantle" in the interpretation of subduction zone magmas. Geology 40 (6) , pp. 539-542. 10.1130/G32963.1

Full text not available from this repository.

Abstract

In the study of geochemical mass balances at subduction zones, the composition of the mantle wedge prior to additions from the slab is a critically important yet poorly constrained parameter. Deconvolving the influence of ancient versus modern enrichments is particularly difficult, especially when considering elements that are highly mobile. Here we provide an alternative approach, using less mobile elements, and a filter to remove the effects of recent slab additions. We provide new Hf isotope data for 30 Mariana Trough (MT) backarc basin lavas. Once filtered, Hf and Nd isotope ratios are highly correlated, of Indian mid-oceanic ridge basalt character, and display variations similar to ocean ridges of comparable lengths. The isotopic variability observed in this “ambient mantle” provides a new paradigm for the interpretation of the varied volcanic products of the arc. Thus, shoshonites associated with the northern termination of the backarc basin rift axis reflect the interaction of a subducted sediment melt with an isotopically enriched mantle source. In contrast, the large volcanoes of the Central Island province have a consistent offset in Nd isotope compositions from the MT array resulting from fluid addition. Existing data for smaller edifices in the submarine portion of the arc have larger variations resulting from fluid addition on a more local scale. We suggest that the similar characterization of ambient mantle elsewhere may help to resolve many conflicting geochemical observations in arc lavas worldwide.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Publisher: Geological Society of America
ISSN: 0091-7613
Last Modified: 04 Jun 2017 04:04
URI: http://orca-mwe.cf.ac.uk/id/eprint/31981

Citation Data

Cited 9 times in Google Scholar. View in Google Scholar

Cited 29 times in Scopus. View in Scopus. Powered By Scopus® Data

Actions (repository staff only)

Edit Item Edit Item