Resolution of the effects of crustal assimilation, sediment subduction, and fluid transport in island arc magmas: PbSrNdO isotope geochemistry of Grenada, Lesser Antilles

Oxygen isotope systematics of the Banda Arc: low δ18O despite involvement of subducted continental material in magma genesis

“…The Banda Arc ␦ 18 O melt signatures are comparable with whole-rock and plagioclase values of 5.5-6.6‰ that were found in the Mariana-Izu-Volcano Arc (Ito and Stern, 1985;Woodhead et al, 1987) and the Aleutians (Singer et al, 1992), whereas they are generally lower than ␦ 18 O wr values reported for the Lesser Antilles Arc (5.5-14‰, Davidson, 1985;Davidson and Harmon, 1989;Smith et al, 1996;Thirlwall et al, 1996) and the Eolian Arc (6.1-8.5‰, Ellam and Harmon, 1990). Harmon and Hoefs (1995) reported a conventional ␦ 18 O wr range of 5.3-7.5 ‰ with an average of 6.1 Ϯ 1.1‰ for oceanic arc basalts, which they had filtered for secondary, post- .…”

“…1) (Magaritz et al, 1978; this study), the Eolian Arc (Ellam and Harmon, 1990), the Lesser Antilles Arc (wr: Davidson and Harmon, 1989;Thirlwall et al, 1996;LF: Smith et al, 1996;Thirlwall et al, 1996), the Mariana Arc (wr: Ito and Stern, 1985;Woodhead et al, 1987;LF: Eiler et al, 2000), Vanuatu (LF: Eiler et al, 2000), the Java sector of the Sunda Arc (wr: Gerbe, 1992, Edwards, 1991;1994, LF: Macpherson, 1994, the Flores sector of the Sunda Arc (Stolz et al, 1988;Edwards, 1991;Van Bergen et al, 1992), the Aleutian Arc (plag: Singer et al, 1992) and the Kermadec Arc (LF: (LF data) can also be observed in the Lesser Antilles and Java. Abbreviations: BS ϭ average bulk sediment; CFS ϭ average carbonate free sediment (Table 4).…”

Oxygen Isotope Variations of Basaltic Lavas and Upper Mantle Rocks

“…Studies of these systems revealed large ranges in δ 18 O whole rock (from values comparable to most terrestrial basalts up to +14 ‰ in several systems) that were correlated with increasing extents of magmatic differentiation and almost certainly reflect crustal assimilation and/or mixing with crustal melts. Recent laser-based studies of mafic lavas from the Andes (Feeley and Sharp 1995), Antilles (Thirlwall et al 1996) and the Kermadec-Hikurangi arc ) corroborate these interpretations (e.g. Fig.…”

Optimization techniques for improving the precision of isotopic analysis by thermal ionization mass spectrometry, taking strontium, neodymium, lead, and osmium as examples

“…The isotopes of strontium (Sr), neodymium (Nd), lead (Pb), and osmium (Os) are the primary indicators of trace element evolutionary processes and date important events during the formation of the Earth and other planetary bodies. [7][8][9][10][11][12][13][14] In this study, we analyzed the isotopes of Sr, Nd, Pb, and Os in reference standard materials using the TRITON TIMS in State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Science. Some experimental conditions, such as different filament materials [rhenium (Re), tungsten (W), and tantalum (Ta)], different cup configurations for the same isotopes, and different activators (using different proportions of H 3 PO 4 and silica-gel) with the same amount of sample, were tested to compare the precision of the analytical results.…”

“…To avoid the above problem, this paper suggests the following schemes: (1) the Faraday cup should be changed when it is seriously degraded, which will not be often because replacement of a Faraday cup is complex and expensive; (2) it is viable to use different Faraday cups in turn to monitor signal and optimize the parameters of isotopes; (3) another option is to avoid the degraded cup and reset a new cup configuration, as proposed for Sr analysis by this paper above. In addition, if there are too many isotopes to avoid the degraded cup, a possible option would be dynamic double or triple collector approaches, shifting isotopes between cup configurations within each measurement cycle (as Thirlwall [9] did). Os and 186 Os.…”