Oceanic island basalts

Figure 8. ° Pb7 Pb vs. Th/Us (derived using Eqn. 5 in the text) diagram for mid-ocean ridge and ocean island basalt based on a recent data set with mostly mass spectrometry measurements (Turner et al. 1997 Bourdon et al. 1996 Dosso et al. 1999 Claude-lvanaj et al. 1998, 2001 Sims et al. 2002). The data show a relatively well defined array that intersect a closed-system hne for the bulk Earth starting with an initial lead isotope composition equal to Canyon Diablo (T = 4.55 Ga). This intersect was used by Allegre et al. (1986) to define the Th/U ratio of the Earth.

Figure 12. Compilation of and activity ratios for ocean island basalts and mid-...

Turner S, Hawkesworth C, Rodgers N, King P (1997) U-Th disequilibria and ocean island basalt generation in the Azores. Chem Geol 139 145-164... 

Mantle reservoirs. The only quasi-systematic studies of igneous materials have centered on the mantle in particular mid-ocean ridge basalts (MORE), ocean island basalts, and mantle peridotites. After reporting one MORE analysis in Chan and Edmond (1988), the first full study of MORE (Chan et al. 1992) reported three apparently imaltered Atlantic basalts and one from the East Pacific Rise, with a range in 8 Li of +3.4 to +4.7 (Fig. 5). Subsequent studies have increased the global range of samples, the diversity of bulk compositions analyzed. 

Kent AJR, Stolper EM (1997) Contamination of ocean-island basalt magmas by a seawater-derived component at Loihi Seamount, Hawaii. EOS Trans AGU 78 F806... 

Weaver BL (1991) The origin of ocean island basalt end-member compositions trace element and isotopic constraints. Earth Planet Sci Lett 104 381-397... 

Since boron concentrations in mantle minerals are exceedingly low, boron isotope analysis of mantle minerals are very restricted. On the basis of a boron budget between mantle and crust, Chaussidon and Marty (1995) conclnded that the primitive mantle had a 5 B-value of-10 2%c.ForMORB Spivack and Edmond (1987) and Chaussidon and Marty (1995) reported a 5 B-value of aronnd -4%c. Higher and lower 5 B-values observed in some ocean island basalts shonld be due to crustal assimilation (Tanaka and Nakamura 2005). 

Year One Refinement of sample preparation and analytical techniques for trace element analysis in ocean island basalts using existing samples from the Galapagos. Compilation of existing geochemical data for Pinta and Marchena Islands. Training of students in analytical techniques, preparation for fieldwork. 

Rocks akin to the Ocean Island Basalts have been found at the Vavilov and Managhi seamounts, off the eastern Sardinian coast (Quirra and Etruschi seamounts and rocks drilled at ODP Site 654), and north and northwest of the western Sicily coast (Aceste seamount, Promoteo lava field and Ustica island Fig. 9.1). Ustica has been described in Chap. 8. 

Fisher, D. E. (1985a) Noble gas data from oceanic island basalts do not require an undepleted mantle source. Nature, 316, 716-18. 

Bohrson W. A. and Reid M. R. (1995) Petrogenesis of alkaline basalts from Socorro Island, Mexico trace element evidence for contamination of ocean island basalt in the shallow ocean crust. J. Geophys. Res. 100(B12), 24555-24576. 

McKenzie D. and O Nions R. K. (1983) Mantle reservoirs and ocean island basalts. Nature 301, 229-231. 

Saal A. E., Hart S. R., ShimizuN., Hauri E. H., and Layne G. D. (1998) Pb isotopic variability in melt inclusions from oceanic island basalts, Polynesia. Science 282, 1481-1484. 

Figure 37 Frequency distribution plots for Os, Nd, and Sr isotope compositions of cratonic and noncratonic peridotite xenoliths. Upper right plots give the range for ocean island basalts (OIB) and arrows show the direction of isotopic evolution for melt depletion and enrichment events. Data compiled from sources cited in Menzies (1990b), Pearson (1999a,b), and those given in Figure 21 (after Pearson and Nowell, 2002).

Hauri E. and Hart S. R. (1993) Re-Os isotope systematics in HIMU and EMU Ocean island basalts. Earth Planet. Sci. Lett. 114, 253-271. 

Figure 3 Compilation of helium isotope data from MORBs, continental hotspots, ocean island basalts, and HIMU sources (reproduced by permission of Mineralogical Society of America from Rev. Mineral. Geochem., 2002,...

Farley K. A. and Craig H. (1994) Atmospheric argon contamination of ocean island basalt ohvine phenocrysts. Geochim. Cosmochim. Acta 58, 2509—2517. 

Graham D. W. (2002) Noble gas isotope geochemistry of midocean ridge and ocean island basalts characterization of mantle source reservoirs. Rev. Mineral. Geochem. 47, 247-317. 

The mantle is the Earth s largest chemical reservoir comprising 82% of its total volume and 65% of its mass. The mantle constitutes almost all of the silicate Earth, extending from the base of the crust (which comprises only 0.6% of the silicate mass) to the top of the metallic core at 2,900 km depth. The chemical compositions of direct mantle samples such as abyssal perido-tites (Chapter 2.04) and peridotite xenoliths (Chapter 2.05), and of indirect probes of the mantle such as basalts from mid-ocean ridge basalts (MORBs) and ocean island basalts (OIBs) (Chapter 2.03), and some types of primitive... 

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