Source of parental melts to carbonatites–critical

Authors: Keith Bell Antonio Simonetti

Publish Date: 2009/06/09

Volume: 98, Issue: 1-4, Pages: 77-89

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Abstract

The restriction of most carbonatites to continental areas raises questions as to whether the parental liquids to carbonatites are generated within the continental lithosphere or whether they are derived from deeper parts of the mantle with the lithosphere playing a subsidiary but important role in trapping volatilerich melts/fluids The constraints imposed by both radiogenic and stable isotopic data from carbonatites worldwide are consistent with a sublithospheric source for the parental melts associated with either asthenospheric ‘upwellings’ or more deepseated plumerelated activity Crucial evidences that support the generation of carbonated melts from sublithospheric mantle are the petrogenetic and temporal association of carbonatites with large igneous provinces LIPs eg Deccan Parana carbonatites with primitive noble gas isotopic signatures radiogenic isotope ratios similar to OIBs ie involving HIMU EM1 and FOZO mantle components and the uniform timeintegrated Rb/Sr and Sm/Nd development lines for Sr and Nd isotopic data for carbonatites from the Superior Province Canada and the Kola Peninsula Russia Such findings are difficult to reconcile with a lithospheric origin Even if a metasomatized lithospheric mantle is considered to be the sole source of carbonated melts an unknown mantle process is required large enough to generate widespread synchronous metasomatism spanning regions in excess of 1 × 106 km2We sincerely thank Drs M Hirschmann WL Griffin and an anonymous reviewer for providing constructive comments on an earlier version of the manuscript We are extremely appreciative for all of the stimulating discussions and interactions over the years with former graduate students postdoctoral fellows and colleagues at Carleton University as well as those with other carbonatite researchers

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