Komatiites abundance

Briigmann G. E., Arndt N. T., Hofmann A. W., and Tobschall H. J. (1987) Noble metal abundances in komatiite suites from Alexo, Ontario and Gorgona Island, Columbia. Geochim. Cosmochim. Acta 51, 2159-2169. 

Copper. The abundance of copper in the depleted mantle raises a particular problem. Unlike other moderately compatible elements, there is a difference in the copper abundances of massive peridotites compared to many, but not all, of the xenolith suites from alkali basalts. The copper versus MgO correlations in massive peridotites consistently extrapolate to values of 30 ppm at 36% MgO, whereas those for the xenoliths usually extrapolate to <20 ppm, albeit with much scatter. A value of 30 ppm is a relatively high value when chondrite normalized ((Cu/Mg)N = 0.11), and would imply Cu/Ni and Cu/Co ratios greater than chondritic, difficult to explain, if true. However, the copper abundances in massive peridotites are correlated with sulfur, and may have been affected by the sulfur mobility postulated by Lorand (1991). Copper in xenoliths is not correlated with sulfur, and its abundance in the xenoliths and also inferred from correlations in basalts and komatiites points to a substantially lower abundance of 20 ppm (O Neill, 1991). We have adopted this latter value. 

Liang Y. and Elthon D. (1990) Evidence from chromium abundances in mantle rocks for extraction of picrite and komatiite melts. Nature 343, 551-553. 

The Archean clastic rocks are also often enriched in chromium, nickel, and cobalt (Danchin, 1967 Condie, 1993), but this feature may only be of regional significance, mostly for the Kaapval Craton and the Pilbara block, where it may reflect the ubiquity of komatiites in the source regions of the sediments. Nevertheless, considering the frequent discrepancies in the anticipated Ni/Cr ratios, in lower than expected MgO content and, at times, high abundance of incompatible... 

Kalgoorli Australia Yilgarn 2.7 Abundant komatiites/exploration driven by nickel mining interests... 

Xie, Q., and Kerrich, R. (1995). Application of isotope dilution for precise measurement of Zr and Hf in low-abundance samples and international reference materials by inductively coupled plasma mass spectrometry Implications for Zr (Hf)/REE fractionations in komatiites. hot. Geosci. 123(1/4), 17. 

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