Date of Award

1-11-2016

Degree Type

Thesis

Degree Name

M.Sc.

Department

Earth and Environmental Sciences

First Advisor

Polat, Ali

Keywords

Alkaline Basalt, Canadian Cordillera, Continental Lithospheric Mantle, Convergent Margin, Mantle Metasomatism, Mantle Xenolith

Rights

CC BY-NC-ND 4.0

Abstract

The Tasse basalts of southeastern British Columbia, Canada, are host to a variety of mantle xenoliths consisting predominantly of spinel lherzolite with minor dunite and pyroxenite. On the basis of REE patterns, the xenoliths are divided into three groups reflecting varying degrees of mantle metasomatism: (1) Group 1; concave-up LREE patterns; (2) Group 2; flat to moderately LREE-enriched patterns; and (3) Group 3; strongly LREE-enriched patterns. The majority of xenolith are enriched in LILE, LREE, U, Th, Pb, and Sr, and depleted in HFSE and HREE. These geochemical characteristics are consistent with a sub-arc mantle source. The Tasse lavas are compositionally alkaline basalts and display OIB-like trace element patterns. They have positive εNd (+3.8 to +5.5) values, with 338−426 Ma depleted mantle model ages, and display OIB-like Nd, Sr and Pb isotopic compositions. The Sr−Nd−Pb isotope and trace element characteristics suggesting that they originated from an upwelling asthenospheric mantle source.

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