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High-pressure aragonite phenocrysts in carbonatite and carbonated syenite xenoliths within an alkali basalt

Vratislav Hurai, Monika Huraiova, Rastislav Milovsky, Jarmila Luptakova and Patrik Konecny
High-pressure aragonite phenocrysts in carbonatite and carbonated syenite xenoliths within an alkali basalt
American Mineralogist (May 2013) 98 (5-6): 1074-1077

Abstract

We describe the first observation of primary magmatic aragonite in carbonatite and carbonated syenite, occurring as xenoliths in a Pliocene basaltic diatreme located near the Hungary-Slovakia border. The aragonite-hosting matrix consists of disordered P-rich calcite, occasionally associated with trachyte glass. We interpret the aragonite growth as evidence of supra-lithostatic overpressure in the magmatic plumbing system that connected the crustal basaltic reservoir with the partial melting zone of the lithospheric mantle, and the disordered calcite+ or -trachyte as quenched residual, immiscible melts, generated close to the solidus of the carbonated alkali basalt differentiated in the crustal reservoir. The quenching event was a phreato-magmatic eruption within the stability field of the low-pressure calcite; this was triggered by advective overpressure, caused by expanding gas bubbles in a quasi-incompressible silicate melt system. The high-pressure, pre-eruption origin of aragonite is indicated by enrichment in (super 13) C compared to the associated calcite interpreted as a record of CO (sub 2) degassing at T>500 degrees C. The oxygen (delta (super 18) O ranges of 22.1-24.5 per mil V-SMOW in aragonite, 21.6-22.7 per mil in calcite) and carbon (delta (super 13) C ranges of -4.4 to -5.9 per mil V-PDB in aragonite, -11.9 to -12.7 per mil in calcite) isotope signatures are consistent with a degassed carbonatite melt primarily derived from a subduction zone.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 98
Serial Issue: 5-6
Title: High-pressure aragonite phenocrysts in carbonatite and carbonated syenite xenoliths within an alkali basalt
Affiliation: Slovak Academy of Sciences, Geological Institute, Bratislava, Slovakia
Pages: 1074-1077
Published: 201305
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 28
Accession Number: 2013-046161
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N48°13'00" - N48°13'10", E19°57'30" - E19°58'00"
Secondary Affiliation: Comenius University, SVK, SlovakiaState Geological Institute D. Stur, SVK, Slovakia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201329
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