Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Comparison of the Rainy Ridge analcime phonolite sill and the Crowsnest volcanics, Alberta, Canada

Publication Type:Journal Article
Year of Publication:1993
Authors:R. J. Goble, Treves, S. B., Ghazi, A. M.
Date Published:Aug-01-1993
ISSN:0008-4077, 1480-3313

A 5–7 m thick analcime phonolite sill occurs in the middle of the Proterozoic Gateway Formation in southwest Alberta. The sill consists of sanidine, aegirine–augite, magnesian hastingsite, melanite with hydrogrossular rims, titanite, and minor biotite, apatite, and opaque minerals. Mineralogical and chemical similarities to the analcime-rich phases of the Cretaceous Crowsnest Formation found some 20 km to the north suggest a genetic relationship. Major differences are the presence of amphibole and hydrogrossular, minerals not reported in the Crowsnest Formation. The presence of amphibole as a primary hydrous phase in the Rainy Ridge sill indicates crystallization from a hydrous magma. Microprobe studies indicate a progressive enrichment of sodium in amphiboles and pyroxenes. An apparent difference in chemical composition and alteration behavior of primary analcime phenocrysts and groundmass analcime is interpreted to reflect crystallization of analcime from a hydrous melt at depth, followed by rapid transport to a shallow depth, and crystallization of the groundmass analcime and hydrogrossular rims.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith