Abstract
Investigations of peridotite xenolith suites have identified a compositional trend from lherzolite to magnesian wehrlite in which clinopyroxene increases at the expense of orthopyroxene and aluminous spinel, and in which apatite may be a minor phase. Previous studies have shown that this trend in mineralogy and chemical composition may result from reaction between sodic dolomitic carbonatite melt and lherzolite at pressures around 1.7 to 2 GPa. This reaction results in decarbonation of the carbonatite melt, releasing CO2-rich fluid. In this study, we have experimentally reversed the decarbonation reaction by taking two natural wehrlite compositions and reacting them with CO2 at a pressure of 2.2 GPa and temperatures from 900 to 1150° C. Starting materials were pargasite-bearing wehrlites, one with minor apatite (composition 71001*) and one without apatite (composition 70965*). At lower temperatures (900° C) the products were apatite+pargasite+magnesite harzburgite for runs using composition 71001*, and pargasite+dolomite lherzolite for runs using composition 70965*. At and above 1000° C, carbonatite melt with harzburgite residue (olivine+orthopyroxene+spinel) and with lherzolite residue (olivine+orthopyroxene+clinopyroxene+ spinel) were produced respectively. Phase compositions in reactants and products are consistent with the documented carbonatite/lherzolite reactions, and also permit estimation of the carbonatite melt compositions. In both cases the melts are sodic dolomitic carbonatites. The study supports the hypothesis of a significant role for ephemeral, sodic dolomitic melts in causing metasomatic changes in the lithosphere at P≤2 GPa. The compositions of wehrlites imply fluxes of CO2, released by metasomatic reactions, which are locally very large at around 5 wt% CO2.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Author information
Authors and Affiliations
Additional information
Received: 15 December 1995/Accepted: 14 February 1996
Rights and permissions
About this article
Cite this article
Yaxley, G., Green, D. Experimental reconstruction of sodic dolomitic carbonatite melts from metasomatised lithosphere. Contrib Mineral Petrol 124, 359–369 (1996). https://doi.org/10.1007/s004100050196
Issue Date:
DOI: https://doi.org/10.1007/s004100050196