No abstract

The interest in microscale distributions of elements and isotopes in calcium carbonate has increased in recent decades due to problems emerging from diverse disciplines such as paleoclimatology, paleoceanography, biomineralization, and geochemical cycling at the Earth's surface. Naturally occuring and synthetic calcium carbonates are, in many cases, heterogeneous in trace or minor elements and stable isotopes. Often these variations cannot be explained by temperature variability or composition of the growth medium thus suggesting nonequlibrium crystal growth. Such disequilibrium is especially significant during growth of carbonate minerals under ambient conditions.An experimental approach was employed to study the effects of mineral growth rate on the fractionation of 7 Li/ 6 Li, Li/Ca, Mg/Ca, Sr/Ca, and U/Ca between Ca carbonates and fluid at 25°C. This work is unique because it evaluates linear mineral growth rates (V=distance/time), rather than bulk mass precipitation rates, through introducing chemical spikes as time markers during the experiment, and analyzing experimental carbonates in situ by sencondary ion mass spectrometry (SIMS) and electron microprobe (EMP).EMP data from this work show that partition coefficients of Sr between calcite and fluid (K d Sr =[Sr/Ca] mineral /[Sr/Ca] fluid ) increase with V, extending the existed K d Sr -V trend to the faster growth region [1, 2, 3]. K d Mg and K d U in aragonite increase with increasing of the growth rate of spherulite (hemispherical bundles of thin aragonite crystals) [4]. In contrast to calcite, K d Sr in aragonite does not show significant correlation with V. The recent SIMS data on Li/Ca suggest that Li behaves similarly to Mg during aragonite growth. 7 Li/ 6 Li yielded single sample variability that exceed those between two aragonite samples precipitated at different rates. Additional 7 Li/ 6 Li, Li/Ca, and Li/Mg data will be presented.New productivity measurements using the 15 N tracer technique were conducted in the north-eastern (NE) Arabian Sea during five expeditions from 2003 to 2007 in winter. Entrainment of NO 3 which supports the observed nitrogen uptake has been quantified. Deepening of mixed layer below 100 m (from its inter-monsoon value between 30-40 m) transferred often more than 100 mmol N-NO 3 m -2 into the surface layers from below. The observed winter blooms in the region are supported by such input and are sustained for more than a month, as is also observed in satellite imagery. Higher new production and f-ratios have been found in late winter, whereas transport of NO 3 is maximum in early winter. In general, new production and f-ratios vary progressively during winter.The largest gap in volcanism in the Hawaiian Islands is between the islands of Kaua'i and O'ahu, where the volume of the islands is the smallest. Volcanic cones west of Ka'ena Ridge are samples of the Hawaiian plume at a time of low magma productivity along axis of the Hawaiian chain. Ka'ena Ridge is an elongate, relatively flat-topped submerged terrace 35-55 km wide ...