Amphibole-Bearing Peridotite Xenoliths from Nushan,Anhui Province:Evidence for Melt Percolation Process in the Upper Mantle and Lithospheric Uplift

The spinel peridotite xenoliths of Group I in Quaternary basanites from Nushan, Anhui Province, can be classified as two suites: 8 hydrous suite characterized by the ubiquitous oc-currence of (Ti-) pargasite and an anhydrous suite. The mineral chemistry reveals that the an-hydrous suite and one associated phlogopite-bearing lherzolite are equilibrated under temperatureconditi0ns of 1000 - 1110℃, whereas amphibole-bearing peridotites display distinct disequilibrium features, indicating partial reequilibration from 1050 to 850℃ and locally down to 750℃.This amphibole-bearing peridotites were probably the uppermost part of the high temperatureanhydrous suite which was modally modified by fractionating H2O-rich metasomatic agent during regional upwelling. This relatively recent lithospheric uplift event foll0wed an older upliftevent recognized from pyroxene unmixing of domains in local equilibrium, as well as the dominant deformation texture in the anhydrous suite. The first thermal disturbance can be linkedwith the regional extension and widespread basaltic volcanism in Jiangsu-Anhui provinces sinceEarly Tertiary and the formation of the nearby Subei (North Jiangsu) fault-depression basinduring the Eocene, while the second event in association with the formation of amphibolesprobably indicates the continuation but diminution of upward mantle flux since Neogene in response to the change in tectonic regime for eastern China.