EVIDENCE FOR PLUME-LITHOSPHERE INTERACTION FROM Nd-Sr SYSTEMATICS OF CARBONATITES AND KIMBERLITE-HOSTED PERIDOTITE XENOLITHS, SOUTHWESTERN GREENLAND. Martin Bizzarro 1 , Antonio Simonetti 1 , R. K. Stevenson 1 , and Stephan Kurzslaukis 2 , 1 GOTOP Center, UniversitØ du QuØbec  MontrØal, Station Centre-ville, P. O. box 8888, MontrØal, QuØbec, Canada, H3C 3P8, 2 De Beers GeoScience Center, P.O. 82232, Southdale, 2135, South Africa. Results from melt experiments and Nd, Pb, and Sr isotopic data have clearly established that carbonatitic melts are of a deep-seated mantle origin. Numerous isotopic studies have already shown their effective use in monitoring the chemical evolution of the subconti- nental mantle (SCM). Moreover, their widespread oc- currence in most continental settings over a significant interval of geologic history (e.g. from 2.7 to 0.1 Ga ago in North America; [1]) permits to monitor the temporal evolution of SCM. The age distribution of carbonatite occurrences worldwide are also well correlated to ma- jor orogenic cycles for the past 3.0 Ga [2]. One inter- pretation is that carbonatite occurrences may result from the interaction between mantle perturbations or upwellings (i.e. plume component) and continental lithosphere, such as in the East African Rift [3] or Dec- can alkaline complexes of India [4]. The alkaline province of Greenland records re- peated magmatic activity for >2.5 Ga [5], and thus provides an opportunity to investigate the temporal variation of possible interaction between different mantle reservoirs. Moreover, recent experiments sug- gest a continuum exists in carbonatite-kimberlite melt compositions produced by variable amounts of melting at the source [6]. One such example is that of the car- bonatite-kimberlite-ultramafic lamprophyre association of the Sarfartoq region in west Greenland. Here we report on the Nd and Sr isotope systematics of the car- bonatite complexes of Tupertalik, Safartoq, and Qaqarssuk ranging in age from 2700, 600, and 175 Ma, respectively. Initial 143 Nd/ 144 Nd and 87 Sr/ 86 Sr ratios for the whole suite vary from 0.51259 and 0.70343 (Qaqarssuk), 0.51201 and 0.70275 (Safartoq), to 0.50908 and 0.70126 (Tupertalik). This data plots along the established Sr and Nd isotopic temporal evolutionary trends defined by North American car- bonatites [1], suggesting that the lithospheres beneath the North Atlantic and Superior cratons shared a simi- lar history. In addition, an isotopic investigation was conducted of least contaminated peridotite xenoliths hosted by kimberlites temporally related to the 175 Ma (Attawapiskat region Superior craton) and 600 Ma (Safartoq, North Atlantic craton) events. These yield systematically lower initial Sr and higher initial Nd isotopic compositions compared to the associated car- bonatites, indicative of derivation from a more de- pleted source. This feature also implies the involve- ment of a more "radiogenic" mantle component during carbonatite formation. Thus, the Sr and Nd evolution- ary defined by the North American and Greenland car- bonatites complexes may result from the mixing be- tween a depleted SCM end-member with a more radio- genic component. Depleted subcontinental lithosphere may represent the former, whereas the latter component may be related to asthenospheric upwellings (mantle plumes) also giving rise to the kimberlite occurrences. References: [1] Bell, K., Blenkinsop, J. (1987) Geochimica et Cosmochimica Acta 51:291-298. [2] Woolley A.R. (1989). In: Bell, K. (ed.) Carbonatites: Genesis and Evolution. London: Unwin Hyman pp. 15- 37. [3] Bell, K. and Simonetti, A. (1996) Journal of Petrology 37: 1321-1239 [4] Simonetti A., Goldstein S.L., Schmidberger S.S. and Viladkar S.G. (1998) Journal of Petrology 39: 1847-1864. [5] Larsen, L.M., Rex, D.C. and Secher, K. (1983) Lithos 16: 215-221. [6] Dalton J.A. and Presnall D.C. (1998) Journal of petrology 39: 1953-1964. Eleventh Annual V. M. Goldschmidt Conference (2001) 3557.pdf View publication stats View publication stats