Su, B.Zhang, H.Tang, Y.Chisonga, B.Qin, K.Ying, J.Sakyi, P.A.2019-05-072019-05-072011-06Su, B., Zhang, H., Tang, Y. et al. Int J Earth Sci (Geol Rundsch) (2011) 100: 695. https://doi.org/10.1007/s00531-010-0527-0Volume 100, Issue 4, pp 695–715https://doi.org/10.1007/s00531-010-0527-0http://ugspace.ug.edu.gh/handle/123456789/29840Garnet-bearing mantle peridotites, occurring as either xenoliths in volcanic rocks or lenses/massifs in high-pressure and ultrahigh-pressure terrenes within orogens, preserve a record of deep lithospheric mantle processes. The garnet peridotite xenoliths record chemical equilibrium conditions of garnet-bearing mineral assemblage at temperatures (T) ranging from ~700 to 1,400°C and pressures (P) > 1.6-8.9 GPa, corresponding to depths of ~52-270 km. A characteristic mineral paragenesis includes Cr-bearing pyropic garnet (64-86 mol% pyrope; 0-10 wt% Cr2O3), Cr-rich diopside (0.5-3.5 wt% Cr2O3), Al-poor orthopyroxene (0-5 wt% Al2O3), high-Cr spinel (Cr/(Cr + Al) × 100 atomic ratio = 2-86) and olivine (88-94 mol% forsterite). In some cases, partial melting, re-equilibration involving garnet-breakdown, deformation, and mantle metasomatism by kimberlitic and/or carbonatitic melt percolations are documented. Isotope model ages of Archean and Proterozoic are ubiquitous, but Phanerozoic model ages are less common. In contrast, the orogenic peridotites were subjected to ultrahigh-pressure (UHP) metamorphism at temperature ranging from ~700 to 950°C and pressure >3.5-5.0 GPa, corresponding to depths of >110-150 km. The petrologic comparisons between 231 garnet peridotite xenoliths and 198 orogenic garnet peridotites revealed that (1) bulk-rock REE (rare earth element) concentrations in xenoliths are relatively high, (2) clinopyroxene and garnet in orogenic garnet peridotites show a highly fractionated REE pattern and Ce-negative anomaly, respectively, (3) Fo contents of olivines for off-cratonic xenolith are in turn lower than those of orogenic garnet and cratonic xenolith but mg-number of garnet for orogenic is less than that of off-cratonic and on-cratonic xenolith, (4) Al2O3, Cr2O3, CaO and Cr# of pyroxenes and chemical compositions of whole rocks are very different between these garnet peridotites, (5) orogenic garnet peridotites are characterized by low T and high P, off-cratonic by high T and low P, and cratonic by medium T and high P and (6) garnet peridotite xenoliths are of Archean or Proterozoic origin, whereas most of orogenic garnet peridotites are of Phanerozoic origin. Taking account of tectonic settings, a new orogenic garnet peridotite exhumation model, crust-mantle material mixing process, is proposed. The composition of lithospheric mantle is additionally constrained by comparisons and compiling of the off-cratonic, on-cratonic and orogenic garnet peridotite. © 2010 Springer-Verlag.enCraton and off-cratonGarnet peridotite xenolithLithospheric mantleOrogenic garnet peridotiteArticle