Lherzolites mantle

Mantle contamination by addition of variable amounts of upper crustal material (e.g. metapelites) to peridotite, possibly represented by both harzburgite and lherzolite. 

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. 

Lorand J. P. (1991) Sulphide petrology and sulphur geochemistry of orogenic Iherzolites A comparative study between Pyrenean bodies (France) and the Lanzo massif (Italy). In Orogenic Lherzolites and Mantle Processes (ed. M. A. Menzies) J. Petrol. 32, pp. 77-95. 

Most of the orogenic spinel Lherzolites also contain small amounts of amphibole ( 1 %) textu-rally equilibrated with the peridotite minerals. These amphiboles have been ascribed to the infiltration of melts/fluids in mantle conditions (Fabries et al., 1991), but their presence is not associated with noticeable chemical enrichments (Vannucci et al., 1995). A possible explanation is that the liquid/rock ratio was so low that the fluid composition was buffered by the LREE-depleted composition of the peridotites. Alternatively, these amphiboles might represent the products of a late crystallization stage during fertilization of the peridotites by LREE-depleted basaltic melts. 

Gmau G., Lecuyer C., Bernard-Griffiths J., and Morin N. (1991) Origin and petrogenesis of the Trinity ophiohte complex (California) new constraints from REE and Nd isotope data. In Orogenic Lherzolites and Mantle Processes, Spec. Vol. J. Petrol, (eds. M A. Menzies, C. Dupuy, and A. Nicolas). Oxford University Press, Oxford, UK, pp. 229-242. 

Obata M. (1980) The Ronda peridotite Garnet-, Spinel-, and Plagioclase-lherzolite facies and the P—T trajectories of a high-temperature mantle intrusion. J. Petrol. 21, 533—572. Obata M. and Morten L. (1987) Transformation of spinel Iherzolite to garnet Iherzolite in ultramafic lenses of the Austridic crystalhne complex, Northern Italy. J. Petrol. 28, 599-623. 

Obata M. and Niida K. (2002) Summary and Synthesis. In Fourth International Workshop on Orogenic Lherzolites and Mantle Processes Field Guide. Samani, Hokkaido, pp. 63—64. 

Ionov D. A., and Weis D. (2002) Hf isotope composition of mantle peridotites first results and inferences for the age and evolution of the hthospheric mantle. Abstract, 4th Int. Workshop on Orogenic Lherzolites and Mantle Processes, Samani, Japan, pp. 56—57. 

Kovalenko V. 1., Solovova I. P., Ryabchikov 1. D., Ionov D. A., and Bogatikov O. A. (1987) Fluidized C02-sulphide-silicate media as agents of mantle metasomatism and megacrysts formation evidence from a large druse in a spinel-lherzolite xenolith. Phys. Earth Planet. Int. 45, 280-293. 

Burton, K. W., Schiano, P., Birk, J.-L. Allegre, C. J. 1999. Osmium isotope disequilibrium between mantle minerals in a spinel-lherzolite. Earth and Planetary Science Letters, 172, 311-322. 

Mitchell R. H. and Keays R. R. (1981) Abundance and distribution of gold, palladium and iridium in some spinel and garnet lherzolites implications for the nature and origin of precious metal rich intergranular components in the upper mantle. Geochim. Cosmochim. Acta 45, 2425-2445. 

Nicolas (1989) divided ophiolite complexes into two main types - the harzburgite type (e.g. Oman Bay of Islands, Newfoundland Zambales, Philippines) and the lherzolite type (e.g. Trinity, California Lanzo, Italy). He proposed that the harzburgite-type of ophiolite represents oceanic crust created at a fast spreading ridge and a mantle sequence which... 

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