Goldschmidt Conference Abstract 2006 Siphoning the lower mantle into southern Italy volcanoes A. CADOUX 1 , F. ALBAREDE 2 , J. BLICHERT-TOFT 2 , D.L. PINTI 3 1 UMR 8148 IDES, Bat. 504, Universite ´ Paris Sud XI, 91405 Orsay Cedex, France (cadoux@geol.u-psud.fr) 2 Laboratoire de Sciences de la Terre, CNRS UMR 5570, Ecole Normale Supe ´rieure, 46, Alle ´e d’Italie, 69364 Lyon Cedex 7, France (francis.albarede@ens-lyon.fr; pinti.daniele@uqam.ca) 3 GEOTOP-UQAM-McGILL, P.O. Box 8888, Succ. Centre Ville, Montre ´al, Que., Canada H3C 3P8 (pinti.daniele@uqam.ca) The presence in oceanic basalts of a common mantle compo- nent that is not the ubiquitous depleted upper mantle (astheno- sphere) of Mid-Ocean Ridge basalts (MORB) is probably one of the major findings of igneous isotope geochemistry. This common component may represent the lower mantle but does not bear the signature of primordial material Farley and Craig, 1992. How ubiquitous the common component (which we will hereafter refer as C, Farley and Craig, 1992) and therefore how widespread upw- ellings of lower mantle may be, is still unknown. One of the places where such an upwelling was suggested is Southern Italy. While locating in a subduction setting, the lavas erupted in this area, particularly around Mt Etna (Sicily), display a strong Ocean Island Basalt (OIB) ‘flavor’. This flavor is alterna- tively interpreted as a vertical mixing of DM and HIMU end-mem- bers, or due to a single common mantle component. The ambiguity between a typical C component (lower mantle) and an assemblage of two end-members is of high dynamic significance. To pursue this question, we ran a principal component analysis (PCA) of lead isotopic data on magmatic rocks from the peninsu- lar Italy and Sicily. The projection of the two first eigenvectors (or components) of the PCA in lead spaces reveals that the first com- ponent, responsible for almost all the variability (99.4%) of the ini- tial information, does not point toward HIMU but pass through the C component Farley and Craig, 1992. Thus, we graphically demonstrated that the component at the origin of the OIB flavor of southern Italy volcanoes is C rather than a DM-HIMU mixture; HIMU is absent in Italy and C is for the first time clearly identified in continental domain, while it was initially defined as the common source component of oceanic basalts Farley and Craig, 1992; Hart et al., 1992; Hanan and Graham, 1996. References Farley, K.A., Craig, H., 1992. Science 258, 821–822. Hart, S.R., Hauri, E.H., Oschmann, L.A., Whitehead, J.A., 1992. Science 256, 517–520. Hanan, B.B., Graham, D.W., 1996. Science 272, 991–995. doi:10.1016/j.gca.2006.06.070 Grazing incidence X-ray diffraction study of products formed on (100) crystal face of pyrite YUANFENG CAI 1,2 ,YUGUAN PAN 2 ,JIYUE XUE 1 1 Department of Earth Sciences, Nanjing University, Nanjing 210093, PR China (caiyf@nju.edu.cn) 2 State Key Laboratory of Mineral Deposits Research, Nanjing 210093, PR China Five pyrites with original crystal face of (100) in different tarnish color were selected from one pyrite-bearing ore sample from Ton- gling multi-metal deposit, Anhui, China. They are blue mottled with violet, yellow mottled with red, yellow, henna mottled with dark vio- let, and reddish brown in color. They may represent different oxidiz- ing degree of pyrites. The grazing incidence X-ray diffractometry (GIXD) were used to study substances formed or precipitated on the surface of pyrite (100) face during chemical weathering. It can tell us two aspect of information, one is mineral phase, and another is how mineral phase changes from the outermost to body. GIXD mea- surements were performed on a Bede D1 diffractometer with a micro- source X-ray generator whose beam size is 300 lm in diameter. The incident angle were fixed at 0.05°, 0.1°, 0.2°, 0.4°, 0.6° up to 2°. The qualitative phase analyses for substances on the outermost surface of pyrites show that the different minerals and/or amorphous sub- stance are present with respect to different tarnish color. Products formed or precipitated on the surface of pyrite (100) face could be put into sulphur-bearing or iron-bearing hydrated oxide mineral group. The gypsum, pyrrhotite, melkicovite, covellite and jalpaite are included in sulphur-bearing group. The goethite, goldichite and fibroferrite may be included into iron-bearing hydrated oxide group. The gypsum and pyrrhotite, etc., presented on the surface imply that sulphur were oxidized to sulphate and part of sulfur was brought into surrounded water, or reduced to sulphide and formed a sulphur-poor layer on the pyrite. According to analyzing a series of GIXD patterns obtained at different angle of incidence for a single pyrite, mineral assemblage may differ from surface to body. Taking the reddish brown one as the example, four diffraction profiles at 0.2575, 0.22105, 0.19118 and 0.1613 nm are present at the pattern of a 2° inci- dent angle whereas they can not be found at the GIXD angle smaller than 0.6° for the reddish brown pyrite. It may suggest that different mineral assemblages formed during different weathering layer from surface to the body. Acknowledgment This study was funded by the NSFC grants (40402007). doi:10.1016/j.gca.2006.06.071 www.elsevier.com/locate/gca Geochimica et Cosmochimica Acta 70 (2006) A79–A123