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side-scan sonar and bathymetric data (Livermore et al.,
1995; Fig. 2). In 1997–1998, sampling of segments E3–E7
was carried out using a drum-shaped dredge during R.V.
Polarstern cruise PS47 (ANT XV/II), with general dredge
direction along the spreading axis. Fresh volcanic material, e.g. pillow lavas, sheet ﬂows and lava tubes, most
of which preserved fresh glassy margins, were recovered
during the 10 dredge deployments during cruise PS47
(Fig. 2). During R.R.S. James Clark Ross cruise JR39b in
1999, fresh volcanic glass fragments were obtained at 28
sites from segments E2 to E9 using a wax corer (Livermore
et al., 1999). These fresh volcanic samples, when combined
with previous high-density sampling of segment E2 (Leat
et al., 2000) during cruise JR12, provide complete coverage of the East Scotia Ridge neo-volcanic zone (Fig.
2, coordinates listed in Table 1). ANALYTICAL METHODS
Macroscopic criteria (vesicularity; size, abundance and
variety of minerals) were used to select diﬀerent rock
types from each dredge haul, from which glassy pillow
rims were separated under a binocular microscope and
washed several times in ultra-pure water. Glass fragments
in wax cups from the wax corer were removed from the
wax with tweezers. The fragments were then placed into
a beaker with water in a microwave oven for 2 min to
melt the wax. The beaker was cooled and the wax
removed. The sample was then washed several times in
Analyses of minerals were made at the University of
Kiel (Institut fur Geowissenschaften) with a Cameca
CAMEBAX electron microprobe running at a beam
current of 12·5 nA and acceleration voltage of 14–15 kV.
Usually, the beam width was about 1–2 m, and was
defocused for plagioclase analyses. Synthetic and natural
standards were used to calibrate the microprobe. Repeat
measurements show that the relative standard deviations
are smaller than ±0·5%, indicating a good reproducibility for all major elements. The major element
concentrations of the volcanic glass samples were determined with a Cameca SX50 electron microprobe at
GEOMAR (Kiel) (Table 1). A beam current of 10 nA with an accelerating voltage of 15kV was used. The beam
was defocused to 5 m to minimize Na loss during
measurements. Glass analyses reported are the averages
of more than ﬁve individual spot analyses (Table 1)
with relative standard deviations smaller than ±0·5%.
International glass standards ( JDF-D2, CFA47 2) were
measured after every 20 analyses to check precision,
which is better than ±0·7%.
H2O analyses were obtained by Fourier transform
infrared (FTIR) spectroscopy at the University of Kiel
using the methods and calibration described by Stolper
(1982). Double-polished glass thin sections, 100–250 m
thick, were analysed with a Bruker IFS 66v/S FTIR
spectrometer equipped with a Bruker A 590 Infrared
Microscope with a mercury–cadmium–telluride detector.
Optically clear areas of known thickness (±5 m) were
measured with aperture size of 120 m diameter with
256 scans per spot. Concent...
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This document was uploaded on 02/01/2014.
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