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Ca-rich carbonates associated with ultrabasic-ultramafic melts: Carbonatite or limestone xenoliths? A case study from the late Miocene Morron de Villamayor volcano (Calatrava Volcanic Field, central Spain).

Authors :
Lustrino, Michele
Prelević, Dejan
Agostini, Samuele
Gaeta, Mario
Di Rocco, Tommaso
Stagno, Vincenzo
Capizzi, Luca Samuele
Source :
Geochimica et Cosmochimica Acta. Jul2016, Vol. 185, p477-497. 21p.
Publication Year :
2016

Abstract

The volcanic products of the late Miocene Morron de Villamayor volcano (Calatrava Volcanic Field, central Spain) are known for being one of the few outcrops of leucitites in the entire circum-Mediterranean area. These rocks are important because aragonite of mantle origin has been reported as inclusion in olivine macrocrysts. We use petrographic observations, mineral compositions, as well as oxygen and carbon isotope ratios coupled with experimental petrology to understand the origin of carbonate phase in these olivine-phyric rocks. Groundmass and macrocryst olivines range from δ 18 O VSMOW of +4.8‰, typical of mantle olivine values, to +7.4‰, indicating contamination by sedimentary carbonate. Carbonates are characterized by heavy oxygen isotope compositions (δ 18 O VSMOW >+24‰), and relatively light carbon isotopes (δ 13 C PDB <−11‰), resembling skarn values, and distinct from typical mantle carbonatite compositions. Petrography, mineral compositions such as low Mg# of clinopyroxene and biotite, low Ca# and low incompatible element abundance of the carbonate, and isotopic ratios of O and C, do not support a mantle origin for the carbonate. Rather, the carbonate inclusions found in the olivine macrocrysts are interpreted as basement limestone fragments entrapped by the rising crystallizing magma. Comparison with experimental carbonatitic and silicate-carbonatitic melts indicates that low-degree partial melts of a carbonated peridotite must have a dolomitic rather than the aragonitic/calcitic composition as those found trapped in the Morron de Villamayor olivine macrocrysts. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00167037
Volume :
185
Database :
Academic Search Index
Journal :
Geochimica et Cosmochimica Acta
Publication Type :
Academic Journal
Accession number :
116002322
Full Text :
https://doi.org/10.1016/j.gca.2016.02.026