Xenoliths kimberlites

The Lu-Hf isotope composition of cratonic lithosphere disequilibrium between garnet and clinopyroxene in kimberlite xenoliths. Geochim. Cosmochim. Acta 6651, Ain. 

Tsai H. M., Shieh Y. N., and Meyer H. O. A. (1979) Mineralogy and 34S/32S ratios of sulfides associated with kimberlites, xenoliths and diamonds. In The Mantle Sample Inclusions in Kimberlites and other Volcanics (eds. F. R. Boyd and H. O. A. Meyer). American Geophysical Union, Washington, DC, pp. 87-103. 

FIGURE 3.4 Mantle pressure and temperature conditions, calculated from kimberlite xenoliths from the Nikos and Jericho kimberlites in the Slave Province of the Canadian shield, indicate that the xenoliths last equilibrated at depths between 60 ... 

Skelton, D., Clements, B., McCandless, T.E., Hood, C. Aulbach, S., Daview, R,. Boyer, L.P. 2003. The Buffalo Head Hills kimberlite province, Alberta. In Kjarsgaard, B.A. (ed.). Slave Province and Northern Alberta Field Trip Guidebook. Geological Survey of Canada, Miscellaneous Publication G-293. Skinner, E.M.W. Marsh, J.S. 2004. Distinct kimberlite pipe classes with contrasting eruption processes. Lithos, 76, 183-200. Sweet, A.R., Boyce, K,. Eccles, D.R. In prep. Palynological constraints on kimberlite emplacement models chronostratigraphy of host rock and clastic xenoliths, Buffalo Head Hills, Alberta. 

While all spinel-lherzolite facies suites show remarkably similar compositional trends as a function of depletion, some garnet peridotite xenoliths in kimberlites and lamproites from ancient cratonic lithospheric keels show signih-cantly different trends (e.g., see Boyd, 1989 Chapters 2.05 and 2.08). Most of these xenoliths are extremely depleted extrapolation of the trends back to the PM MgO of 36.7% gives similar concentrations of Si02, EeO AI2O3, and CaO to the spinel Iherzolites (O Neill and Palme, 1998) the difference in their chemistry is due to a different style of melt extraction, and not a difference in original mantle composition. 

Nickel K. G. and Green D. H. (1984) The nature of the uppermost mantle beneath Victoria, Australia as deduced from Ultramahc Xenoliths. In Kimberlites, Proc. 3rd Inter. Kimberlite Conf. (ed. J. Kornprobst). Elsevier, Amsterdam, pp. 161-178. 

Harte B. (1983) Mantle peridotites and processes— the Kimberlite sample. In Continental Basalts and Mantle Xenoliths (eds. C. J. Hawkesworth and M. J. Norry). Shiva Publishing, Nantwich, UK, pp. 46-91. 

Despite peridotite xenoliths in basalts being recognized for several centuries and comparisons being made to Iherzolite massifs (Lacroix, 1893), it was not until work on garnet peridotites and diamonds in kimberlites by Fermor (1913) and Wagner (1914) that such xenoliths were conceptually associated with a peridotite zone in... 

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... 

An unusual variety of ultrahigh pressure xenoliths has been described from the Jagersfon-tein kimberlite (Haggerty and Sautter, 1990 Sautter et ai, 1991). These xenoliths (type XIII, Table 1) comprise four-phase Iherzolite, discrete garnets, or iron-rich Iherzolites with eclogitic affinities (Sautter et ai, 1991). Their key... 

Figure 1 Common petrographic textures in peridotite xenoliths. Other textural details given in Table 1. (a) Coarse texture in cross-polarized light of garnet peridotite containing olivine (ol), orthopyroxene (opx), and garnet (gt). (b) Mosaic porphyroclastic texture in plane polarized light of garnet peridotite. Both samples are from the Torrie kimberlite. Slave Province (scale bar is 1 mm).

The Mg of orthopyroxene is similar or slightly greater than that of olivine, due to a relative Fe-Mg partition coefficient (Kd) of 1 that is independent of P and T (von Seckendorff and O Neill, 1993). The calcium content of orthopyroxene also varies depending on the temperature of equilibration of the sample and its bulk composition. In both the spinel- and garnet-facies, the CaO content increases with T and varies between 0.2 wt.% and 2.0 wt.%. Orthopyroxenes with very low CaO occur in harzburgites and/or in low-T samples in many kimberlite-borne xenolith suites. 

Figure 4 Covariation of Cr/(Cr + Al) and Fe/(Fe -t-Mg) in spinels from mantle xenoliths in kimberlites and other volcanic rocks. The data points are representative of the extremities of fields for a database of 2.5 X 10 analyses (source Barnes and Roeder, 2001).

Figure 18 Primitive mantle normalized trace-element abundance patterns for whole-rock MARID xenoliths from kimberlites. Primitive mantle values used for normalisation in this plot and subsequent plots are those of McDonough and Sun (1995) (sources Pearson and Nowell, 2002 Gregoire et al, 2002).

Cratonic peridotite xenoliths from Lesotho, S. Africa, the Jericho kimberlite, Slave craton, and Somerset Island, Churchill Province, northern Canada, along with selected samples from... 

Figure 20 Primitive mantle normalized extended PGE patterns (including rhenium) for cratonic whole-rock garnet peridotite xenoliths from the Letseng kimberlite (Lesotho) (sources Irvine, 2002 and Pearson et al., 2004).

Zircons from glimmerites have higher UATh than zircons from MARID/PKP xenoliths. Recent studies link both the geochemistry and geochronology of MARID xenoliths to the crystallization products of group II kimberlites in the lithospheric mantle (Hamilton et al, 1998 Konzett et al, 2000 Gregoire et al, 2002). Monazite has been reported from metasomatized... 

Titanates are another group of oxide phases occurring in metasomatized peridotites and MARID assemblages (Jones et al, 1982 Haggerty et al, 1983 Haggerty, 1987). So far, these phases have not been recognized in noncratonic continental or oceanic xenoliths and hence are characteristic of kimberlite-related xenolith sampling. LIMA minerals are members... 

Figure 31 Whole-rock versus mineral separate Nd-Sr isotopic compositions for kimberlite derived xenoliths from Bultfontein (Richardson et al, 1985) and one sample from Jagersfontein (Walker et al., 1989a). Lines connect coexisting phases/whole-rocks. Initial isotopic composition of the Bultfontein kimberlite is also plotted. Jagersfontein...

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