Osmium isotope systematics of historical lavas from Piton de la Fournaise (Réunion Island, Indian Ocean)
- 457 Downloads
Re–Os isotope and elemental data have been obtained for 20 historical picrites and basalts (1931–2006) from the Piton de la Fournaise volcano on Réunion Island and two old (>0.78 Ma) cumulates from a drill hole in the eastern part of the volcano. The 187Os/188Os ratios of the historical lava samples, selected to cover the MgO concentration and Pb isotopic ranges of Piton de la Fournaise lavas, range from 0.1311 to 0.1374. This result, together with previous results on 66-Ma-old lavas from the Deccan Traps (Allègre et al. in. Earth Planet Sci Lett, 170:197–204, 1999), supports the idea that the Os isotopic signature of the Réunion plume is relatively uniform and is at the less radiogenic end of the ocean island basalt spectrum. In detail, lavas erupted before 1992 seem to have higher 187Os/188Os than the lavas erupted after the 1992–1998 period of quiescence. Comparison of 187Os/188Os ratios with Pb, Sr and Nd isotopic data on the same set of samples shows no correlation between Os and Sr–Nd isotopes, whereas a broad positive relationship with Pb isotopes is observed, which is interpreted to reflect coupled fractionation of Re/Os and U–Th/Pb in the mantle due to the partitioning of Pb and Os into sulphides. Lavas inferred to be recording the Os isotopic signature of the Réunion plume source have higher 187Os/188Os ratios than the primitive mantle values. While this might be ascribed to melting of a lithologically heterogeneous source comprising recycled oceanic crust and/or continental sediment, the expected coupled Os–Sr–Nd–Pb isotopic variations are not observed. It is thus proposed that the mantle source for Piton de la Fournaise has inherently slightly radiogenic 187Os/188Os values that could reflect a mantle domain almost isolated from recycling processes.
KeywordsGeochemistry Réunion Piton de la Fournaise Os isotopes Plume composition
We would like to acknowledge the Thermo Electron Corp. and D. Auclair for their assistance with the Triton mass spectrometer, and J.L. Birck and A. Poirier for the mixed spike 185Re-190Os preparation. We are also grateful to Chantal Bosq for Sr and Nd analyses. Samples were provided by F. Albarède, P. Boivin, P. Bachèlery, T. Staudacher, and the volcanological observatory of Piton de la Fournaise. Constructive reviews by H. Becker and three anonymous reviewers led to an improved manuscript. J. Lassiter and L. Reisberg are also thanked for helpful comments on an earlier version of the manuscript. This is laboratory of excellence ClerVolc contribution n°23.
- Albarède F, Tamagnan V (1988) Modelling the recent geochemical evolution of the Piton de la Fournaise volcano, Réunion Island, 1931–1986. J Petrol 29:997–1030Google Scholar
- Birck J-L, Roy-Barman M, Capmas F (1997) Re-Os isotopic measurements at the femtomole level in natural samples. Geostand Newsl 20:9–27Google Scholar
- Bryce JG, DePaolo DJ, Lassiter JC (2005) Geochemical structure of the Hawaiian plume: Sr, Nd and Os isotopes in the 2.8 km HSDP-2 section of Mauna Kea volcano. Geochem Geophys Geosystem. doi: 10.1029/2004GC000809
- Gillot PY, Nativel P, Condomines M (1990) Evolution volcano-structurale du Piton de la Fournaise depuis 0.53 Ma. In: Lenat J-F (ed) Le volcanisme de la Réunion. Centre de Recherches Volcanologiques, Clermont Ferrand, pp 243–256Google Scholar
- Hanyu T, Tatsumi Y, Senda R, Miyazaki T, Chang Q, Hirahara Y, Takahashi T, Kawabata H, Suzuki K, Kimura J-I, Nakai S (2011) Geochemical characteristics and origin of the HIMU reservoir: a possible mantle plume source in the lower mantle. Geochem Geophys Geosyst. doi: 10.1029/2010GC003252 Google Scholar
- Lassiter JC, Blichert-Toft J, Hauri EH, Barsczus HG (2003) Isotope and trace element variations in lavas from Raivavae and Rapa, Cook-Austral islands: constraints on the nature of HIMU- and EM-mantle and the origin of mid-plate volcanism in French Polynesia. Chem Geol 202:115–138CrossRefGoogle Scholar
- Pearson NJ, Alard O, Griffin WL, Jackson SE, O’Reilly SY (2002) In situ measurement of Re-Os isotopes in mantle sulfides by laser ablation multicollector-inductively coupled plasma mass spectrometry: analytical methods and preliminary results. Geochim Cosmochim Acta 66:1037–1050CrossRefGoogle Scholar
- Roy-Barman M (1993) Mesure du rapport 187Os/186Os dans les basaltes et péridotites: contribution à la systématique 187Re–187Os dans le manteau. University Paris, Thesis 7Google Scholar
- White WM, Cheatham MM, Duncan RA (1990) Isotope geochemistry of Leg 115 basalts and inferences on the history of the Reunion mantle plume. Proc ODP Sci Results 115:53–62Google Scholar