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GEOREF RECORD

Two-stage fractionation history of the alkali basalt-trachyte series of Sete Cidades Volcano (Sao Miguel Island, Azores)

Alberto Renzulli and Patrizia Santi
Two-stage fractionation history of the alkali basalt-trachyte series of Sete Cidades Volcano (Sao Miguel Island, Azores)
European Journal of Mineralogy (April 2000) 12 (2): 469-494

Abstract

A comprehensive data set of mineral and rock compositions of alkaline lavas and pumice erupted from the Sete Cidades volcano is presented, including EPMA results for olivines, clinopyroxenes, plagioclases, alkali feldspars, kaersutites, biotites, Cr-spinels, Ti-magnetites and ilmenites. A low-P fractional crystallization at relatively high f (sub O) (sub 2) was the main magmatic process generating this suite of rocks, which mostly consists of basaltic-hawaiitic and trachytic rocks; mugearites are scarce, indicating the possibility that the residual liquids were able to leave the hawaiitic crystal mush only when the density had been lowered by compositional change or volatile exsolution. The geochemical variations within each group of minerals are dependent on the sequence of crystallization and the corresponding magmatic environment (T, P, f (sub O) (sub 2) ). Relatively primitive, slightly ne-normative basalts with MgO < or = 14% were trapped through flank eruptions indicating they were not held at any crustal levels, with rapid ascent through the plumbing system. Some of the basalts were held close to the Moho where they evolved by wehrlite fractionation to produce slightly hy-normative hawaiites with < 7% MgO.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 12
Serial Issue: 2
Title: Two-stage fractionation history of the alkali basalt-trachyte series of Sete Cidades Volcano (Sao Miguel Island, Azores)
Affiliation: Universita di Urbino, Instituto di Vulcanologia e Geochimica, Urbino, Italy
Pages: 469-494
Published: 200004
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 86
Accession Number: 2000-041820
Categories: Igneous and metamorphic petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 13 tables, sketch maps
N37°42'00" - N37°53'60", W25°52'00" - W25°07'60"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
Update Code: 200014
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