Eclogite xenoliths trace elements

Studies of mantle xenoliths have confirmed the view from seismology that peridotite is volumetrically the dominant component of the Earth s shallow mantle (<400 km) (see Chapter 2.02). This is because xenolith suites in almost all tectonic environments are dominated by peridotites. Even at localities where other lithologies such as eclogite dominate the intact xenolith suite, mineral concentrate studies show that peridotite dominates the inventory of entrained mantle material (Schulze, 1989). Major- and trace-element studies of mineral concentrates from mined kimberlites have also been used to illustrate... 

Arculus R. J., Ferguson J., Chappell B. W., Smith D., McCulloch M. T., Jackson I., Hensel H. D., Taylor S. R., Knutson J., and Gust D. A. (1988) Trace element and isotopic characteristics of eclogites and other xenoliths derived from the lower continental cmst of southeastern Australia and southwestern Colorado Plateau USA. In Eclogites and Eclogite-Facies Rocks (ed. D. C. Smith). Elsevier, Amsterdam, pp. 335-386. 

One particular class of Archaean mantle xenoliths has received special attention. These are eclogites recovered from the subcontinental lithosphere. Richardson et al. (2001) showed that some Archaean eclogite xenoliths have the trace element and Os-isotopic characteristics of a basaltic protolith and an isotopic history which shows a significant time gap between basalt generation and eclogite crystallization. These properties are typical of subducted ocean floor and indicate that the subcontinental lithosphere beneath the Kaapvaal Craton contains fragments of 2.9 Ga subducted ocean floor. 

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