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A new method using microwave digestion combined with inductively coupled plasma-mass spectrometry (ICP-MS) was studied to analyze the elemental composition of a variety of komatiites samples. Microwave digestion consisted in two-stage heating and pressurizing acid treatments for maximum dissolution of the samples. We report here different quality control measurements (external and internal calibration, monitoring of reference materials) which involve standard deviation calculations and recovery examinations in order to test the precision and accuracy of the analytical procedure. Data for 17 elements (Na, P, K, T, V Cr, Mn, Co, Ni, Cu, Zn, Zr, Pb, Al, F, Ca and Mg) in eight komatiite samples and two USGS basalt reference samples (BCR-2 and BHVO-2) are presented. We evaluate our new digestion and instrumental procedure. The element concentration obtained for BCR-2 and BHVO-2 agreed well with the certified values, the relative standard deviations were lower than 5% and recoveries were good. Our analytical results demonstrate that it reproduces accurately the concentrations of minor and trace elements in komatiites. The ease of digestion of the samples and the speed (less than 12 h) to digest the komatiite material makes this technique an efficient method to be used easily and routinely for preparing and analyzing komatiites samples for multiple elements determination.

We present measurements for the production of nitrogen oxides (NO and N2O) in CO2-N2 mixtures that simulate different stages of the evolution of the atmospheres of the Earth, Venus and Mars. The nitrogen fixation rates by two different types of electrical discharges, namely lightning and coronae, were studied over a wide range in CO2 and N2 mixing ratios. Nitric oxide (NO) is formed with a maximum energy yield estimated to be ~1.3 x 10(16) molecule J-1 at 80% CO2 and ~1.3 x 10(14) molecule J-1 at 50% CO2 for lightning and coronae discharges, respectively. Nitrous oxide (N2O) is only formed by coronae discharge with a maximum energy yield estimated to be ~1.2 x 10(13) molecule J-1 at 50% CO2. The pronounced difference in NO production in lightning and coronae discharges and the lack of formation of N2O in lightning indicate that the physics and chemistry involved in nitrogen fixation differs substantially in these two forms of electric energy., (c2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.)