East Scotia Ridge unsecured

Comparison of the h2o concentrations of two basalt

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Unformatted text preview: rations were calculated using the Beer–Lambert law (e.g. Stolper, 1982) with assumed densities of 2·7 g/cm3. Replicate analyses of different glass fragments from the same specimen were typically reproducible to ±10%. Comparison of the H2O concentrations of two basalt glasses (EN112 4D-10; P15051) analysed by FTIR spectroscopy at the University of Tulsa (USA) (Michael, 1995) with the FTIR analyses at University of Kiel show reproducibility better than ±5%. Trace element concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) with a VG PlasmaQuad PQ1 system at the University of Kiel, using preparation and measurement methods described by Garbe-Schonberg (1993). Analytical ac¨ curacy and reproducibility are estimated from measurements of international rock standards BHVO-1 and BIR, and duplicate analyses of samples (Table 1). The accuracy of the standards is within ±10% of the suggested working values (Jenner et al., 1990; Govindaraju, 1994), but generally better than ±5% for rare earth elements (REE). Duplicate analyses show reproducibility to be better than 3%, except for the transition metals (e.g. Cr, Ni, Cu, Zn, Ga) and elements with very low concentrations (e.g. Cs), which show deviations of up to 20% (Table 1). Sr, Nd and Pb isotope ratios of volcanic glasses were measured on a MAT262-RPQ2+ thermal ionization mass spectrometer at GEOMAR in static mode. Glass chips were leached for 1 h in 6N HCl before sample dissolution, and analytical procedures followed those described by Hoernle & Tilton (1991). 87Sr/86Sr ratios were normalized to 86Sr/88Sr = 0·1194 within-run and 143Nd/ 144 Nd ratios to 146Nd/144Nd = 0·7219. The long-term reproducibility of NBS 987 in this laboratory is 87Sr/ 86 Sr = 0·710254 ± 17 (n = 83) and of La Jolla 143Nd/ 144 Nd = 0·511845 ± 11 (n = 123). The in-house SPEX monitor, calibrated against La Jolla with 143Nd/144Nd = 0·511706 ± 12 (n = 9), yielded 143Nd/144Nd = 0·511705 1439 JOURNAL OF PETROLOGY VOLUME 43 NUMBER 8 AUGUST 2002 Table 1: Location, water depth and geochemical analyses of the East Scotia Ridge volcanic glasses Segment: E2 E2 E2 E3 E3 E3 E3 E3 E3 E3 Sample: wx44 wx42 wx43 96DS-1 96DS-2 96DS-3 96DS-4 wx45 97DS-1 97DS-2 97DS-4 Lat. (S): 56°02·01′ 56°06·03′ 56°09·40′ 56°32·3′ 56°32·3′ 56°32·3′ 56°32·3′ 56°40·00′ 56°46·6′ 56°46·6′ 56°46·6′ Long. (W): 30°19·51′ Depth (m): 2840 30°19·51′ 2758 30°18·51′ 2885 30°43·7′ 3880 30°43·7′ 3880 30°43·7′ 3880 30°43·7′ 3880 30°43·00′ 3730 30°44·0′ 3949 30°44·0′ 3949 30°44·0′ 3949 18/8 49·65 1·32 15·33 8·31 0·17 8·25 11·80 3·09 0·11 0·26 0·12 98·41 67·58 10 51·55 1·71 15·95 8·23 0·16 6·94 10·38 3·39 0·21 0·35 n.d. 98·88 63·89 9/2 51·58 1·69 15·94 8·13 0·16 6·95 10·40 3·38 0·21 0·33 0·45 99·24 64·20 10 51·87 1·71 15·88 8·05 0·18 6·97 10·36 3·39 0·23 0·37 n.d. 99·01 64·50 35·7 324 36·3 124 59·4 56·7 14·7 1·02 104 24·4 70·8 1·58 0·014 12·3 2·35 7·40 1·40 7·89 2·86 1·07 3·89 0·693 4·62 0·986 2·93 0·403 2·63 0·385 2·17 0·105 0·007 0·376 0·11...
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This document was uploaded on 02/01/2014.

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