Mantle eclogites: evidence of igneous fractionation in the mantle

UHP metamorphism recorded by kyanite-bearing eclogite in the Seve Nappe Complex of northern Jämtland, Swedish Caledonides

“…Exsolution of kyanite from pyroxene is indicative of a Ca-Eskola component in addition to Ca-Ts component in the primary pyroxene (e.g. Smyth et al, 1989). Experimental studies show that Ca-Eskola component is stable at (ultra) high-pressure and high-temperature conditions (Wood and Henderson, 1978;Gasparik, 1986;Hermann, 2002;Konzett et al, 2008;Zhao et al, 2011).…”

Type I eclogites from Roberts Victor kimberlites: Products of extensive mantle metasomatism

“…Petrography was an important component of the early studies and a key element in the original suggestions of a magmatic origin (Macgregor and Carter, 1970;Harte and Gurney, 1975;Lappin and Dawson, 1975;Hatton and Gurney, 1977;Smyth et al, 1989;Sautter and Harte, 1990). However, with the development of geochemical techniques, more attention has been focused on the chemical aspects of these rocks and less on petrographic observations.…”

“…The distinction between Type I and Type II eclogites, originally developed at Roberts Victor, can be recognised in the few Kaapvaal kimberlites in which eclogites are abundant enough to have been studied in detail, including Bellsbank and Bobbejahn (Smyth et al, 1989) and Kaalvallei (Viljoen et al, 2005). However, in most kimberlites of this craton, as in other cratons worldwide, eclogites make up 0-15% of the total xenolith population, and typically are small in size (Schulze, 1989).…”

Subduction-related origin of eclogite xenoliths from the Wajrakarur kimberlite field, Eastern Dharwar craton, Southern India: Constraints from petrology and geochemistry

“…their discovery by Hauy (1822). Eclogite xenoliths are usually interpreted either as fragments of subducted oceanic crust representing gabbroic or basaltic protoliths or oceanic crustal cumulates emplaced tectonically into the lithospheric mantle (Shervais et al, 1988;Taylor and Neal, 1989;Neal et al, 1990;Jerde et al, 1993;Jacob et al, 1994;Viljoen et al, 1996;Snyder et al, 1997;Jacob and Foley, 1999;Barth et al, 2001;Shirey et al, 2001;Jacob, 2004;Usui et al, 2006;Nikitina et al, 2014), or as high-pressure, magmatic cumulates (MacGregor and Carter, 1970;Hatton, 1978;Smyth et al, 1989;Viljoen et al, 1996;Snyder et al, 1997;Barth et al, 2002;Taylor et al, 2003;Heaman et al, 2006;Appleyard et al, 2009;Jacob et al, 2009). Some eclogites have been linked to partial melting and melt-mantle reaction processes associated with subduction, representing residues of tonalite melt extraction from basaltic crust (Ireland et al, 1994;Rollinson, 1997;Jacob and Foley, 1999;Barth et al, 2002;Rapp et al, 2003;Smart et al, 2009;Tappe et al, 2011;Pernet-Fisher et al, 2014;Smit et al, 2014).…”