Petrology and geochemistry of Tehuitzingo serpentinites, Mexico 419 BOLETÍN DE LA SOCIEDAD GEOLÓ G ICA MEXICANA VOLU M EN 61, NÚ M . 3, 2009, P. 419-435 D GEOL DA Ó E G I I C C O A S 1904 M 2004 . C EX . ICANA A C i e n A ñ o s Petrology and geochemistry of Tehuitzingo serpentinites (Acatlán Complex, SW Mexico) Guillermina González-Mancera*1, Fernando Ortega-Gutiérrez2, Joaquín A. Proenza3, Viorel Atudorei4 1Facultad de Química, Universidad Nacional Autónoma de México, 04510, México, D.F: 2Instituto de Geología, Universidad Nacional Autónoma de México, 04510, México, D.F. 3Departament de Cristallografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, C/Martí i Franquès s/n 08028 Barcelona, Spain 4Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, NM 87131, USA *
[email protected] Abstract Petrographic and geochemical studies of the serpentinites from the Tehuitzingo body, the main ophiolitic outcrop of the Paleozoic Acatlán Complex of southern Mexico, provide new petrogenetic evidence and preliminary data on the nature of the fluids that interacted with an original mantle peridotite. Textures of the studied serpentinites show the principal events of recrystallization and metasomatism, but the diagnostic phases associated with the high pressure events related to subduction were erased. Preliminary H and O isotope studies in serpentinite and chorite suggest the involvement of marine water, probably under oceanic conditions during the first serpentinization event. Accessory chromite in the serpentinites is characterized by #Cr ~0.6 and serpentinites display low abundances of Ti, Na, Nd, Sm, Lu and Hf, which suggest that Tehuitzingo serpentinites represent relicts of a depleted mantle formed in a suprasubduction zone, probably in a back-arc setting that experienced partial melting in excess of 18%.