Komatiites

OTHER 5 GABBRO RELATED KOMATIITIC DEPOSITS SULFIDE DEPOSITS (N 0)... 

Table 5.16. Major-element composition (weight percent) of a komatiitic liquid and normative minerals.

Arndt, N. T. (1977). Partitioning of nickel between olivine and ultrabasic and basic komatiitic liquids. Carnegie. Inst. Washington Year Book, 76, 553-57. 

The trace element patterns in Figure 4 are similar to komatiites of the Kidd-Munro assemblage, whose negative HFSE were interpreted by %man (1999) to be a result of contamination by other HFSE-depleted rock. If Big Lake volcanic rocks are plume-derived, their negative HFSE depletions could similarly be explained by country arc rock contamination in lavas or parent magma chambers. 

Barrie, C., Erendi, A., Cathles, L. 2001. Paleosea-floor volcanic-associated massive sulfide mineralization related to a cooling komatiite flow, Abitibi Subprovince, Canada. Economic Geology, 96, 1695-1700. 

Wyman, D. 1999. A 2.7 Ga komatiite, low Ti tholeiite, arc tholeiite transition, and inferred proto-arc geodynamic setting of the Kidd Creek deposit evidence from precise trace element data. Economic Geology Monograph, 10, 511-528. 

Puchtel I. and Humayun M. (2000) Platinum group elements in Kostomuksha komatiites and basalts implications for oceanic crust recycling and core-mantle interaction. Geochim. Cosmochim. Acta 64, 4227-4242. 

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. 

Crocket J. H. and MacRae W. E. (1986) Platinum-group element distribution in komatiitic and tholeiitic volcanic rocks from Munro Township, Ontario. Econ. Geol. 81, 1242-1251. 

Ringwood A. E., Seifert S., and Wanke H. (1987) A komatiite component in Apollo 16 highland breccias imphcations for the nickel-cobalt systematics and bulk composition of the Moon. Earth Planet. Sci. Lett. 81, 105—117. 

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. 

Figure 49 Bulk analyses of eclogite and alkremite (alkremite-corgaspinite-corganite Table 1) xenoliths from kimberlites compared with massif eclogites and Archean basalts and komatiites (open field). Data sources Kushiro and Aoki (1968), Sobolev (1974), Mazonne and Haggerty (1989), Hills and Haggerty (1989), Taylor and Neal (1989), Ireland et al. (1994), Pyle and Haggerty (1994), Snyder et al. (1993), Jacob et al. (1994), and Jacob and Foley (1999). Outlined field is for Archean basalts and Komatiites taken from Ireland et al. (1994).

Figure 54 Comparison of present-day osmium isotopic compositions of eclogite xenoliths from Udachnaya, Yakutia (Pearson et ah, 1995c) and S. Africa (Pearson et al, 1992 Menzies et al, 1999 Shirey et ah, 2001) with continental crust, oceanic basalts (Shirey and Walker, 1998), and Archean komatiites and basalts (Walker et al, 1989b). Udachnaya peridotite data from Pearson et al (1995a).

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

Walter M. J. (1998) Melting of garnet peridotite and the origin of komatiite and depleted lithosphere. J. Petrol. 39, 29-60. 

Richard D., Marty B., Chaussidon M., and Arndt N. (1996) Hehum isotopic evidence for a lower mantle component in depleted Archean komatiite. Science 273, 93-95. 

Asahara Y. and Ohtani E. (2001) Melting relations of the hydrous primitive mantle in the CMAS-H2O system at high pressures and temperatures, and imphcations for generation of komatiites. Pkys. Earth Planet. Inter. 125, 31-44. 

Ohtani E., Mibe K., and Kato T. (1996) Origin of cratonic peridotite and komatiite evidence for melting in the wet Archean mantle. Proc. Japan Acad. 72(B), 113-117. 

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