Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Pe-Piper, G. Search for Related Content GeoRef GeoRef Citation

Relationship of amphibole composition to host-rock geochemistry: the A-type gabbro-granite Wentworth pluton, Cobequid shear zone, eastern Canada

Department of Geology, Saint Mary’s University, Halifax, N.S., B3H 3C3, Canada. e-mail: gpiper{at}smu.ca

The Wentworth pluton is the most alkaline of a series of Late Devonian metaluminous to mildly peralkaline plutons in the Cobequid shear zone. It includes numerous granitoid bodies of slightly differing composition, which may contain sodic, sodic-calcic or calcic amphiboles. This study examines the relative importance of host rock composition including volatiles, fO₂, and temperature in controlling the type of amphibole present. Electron microprobe analyses and back-scattered electron images were used to characterize the amphiboles and whole-rock geochemical analyses were made from the host granites. Magmatic sodic amphiboles are arfvedsonite, ferrorichterite and katophorite. Ferrowinchite and riebeckite developed by subsolidus oxidation reactions with loss of fluorine. Sub-solidus changes in Fe-Ti oxides make reliable estimation of fO₂ difficult. Regionally, sodic amphiboles are found only in the Wentworth pluton, suggesting the importance of peralkaline geochemistry and perhaps higher temperature as a result of voluminous gabbro in the pluton. However, the presence of sodic or calcic amphibole in granite with >73% SiO₂ in the Wentworth pluton shows no systematic difference with either host-rock geochemistry or distance from the gabbroic heat source, except that rocks with sodic amphibole have high Li, suggesting abundance of free water.

Key-words: amphibole, granite, Nova Scotia, Cobequid shear zone, lithium, alkalis.

This article has been cited by other articles:

				R. F. Martin Amphiboles in the Igneous Environment Reviews in Mineralogy and Geochemistry, October 1, 2007; 67(1): 323 - 358. [Full Text] [PDF]