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DOI: 10.1007/s00410-007-0267-8

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Contributions to Mineralogy and Petrology 155, 6 (2008) 719-738

Limestone assimilation by basaltic magmas: an experimental re-assessment and application to Italian volcanoes

Giada Iacono Marziano 1, 2, Fabrice Gaillard (  Corresponding author ) 2, 3, Michel Pichavant 3

(2008)

The results of an experimental study of limestone assimilation by hydrated basaltic magmas in the range 1050-1150°C, 0.1–500 MPa are reported. Alkali basalts doped with up to 19 wt% of Ca,Mg-carbonates were equilibrated in internally heated pressure vessels and the resulting phase relationships are described. The major effects of carbonate incorporation are: 1) generation of CO2-rich fluid phases; 2) change in liquidus phase equilibria; the crystallization of Ca-rich clinopyroxene is favored and the other phases (e.g. olivine, plagioclase), present in the absence of carbonate assimilation, are consumed. As a consequence of the massive clinopyroxene crystallization, the residual melt is strongly silica-depleted and becomes nepheline-normative. Compositional and mineralogical evolutions observed in Mt.Vesuvius eruptive products match those documented in our experiments with added carbonates, suggesting the possibility that carbonate assimilation increased during the last 25ka of activity. In Central-Southern Italy, carbonate assimilation at shallow levels probably superimposes on deeper source heterogeneities.

1:	Dipartimento di Chimica e Fisica della Terra (DIPARTIMENTO DI CHIMICA E FISICA DELLA TERRA)
	Università degli studi di Palermo
2:	Bavarian Research Institute of Experimental Geochemistry and Geophysics (Bayerisches Geoinstitut)
	Universitat Bayreuth – University of Bayreuth
3:	Institut des Sciences de la Terre d'Orléans (ISTO)
	CNRS : UMR6113 – INSU – Université d'Orléans

subject

:

Sciences of the Universe/Earth Sciences/Volcanology Environmental Sciences/Global Changes

keyword(s): Limestone assimilation - Experimental petrology - Silica-undersaturation - Mt. Vesuvius

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From: Nathalie Pothier <>

Submitted on: Thursday, 6 December 2007 14:58:21

Updated on: Tuesday, 10 June 2008 17:30:03