Volatiles in vitreous basaltic rims, HSDP 2, big island, Hawaii

Temperature resolved analysis of volatiles from vitreous basaltic rims (HSDP 2 core, Hawaii) and from experimental melts was carried out to investigate the total volatile content of basaltic melts and the influence of magma contamination on the degassing behaviour of volcanic rocks. The degassing of H2O, CO2, and SO2 from vitreous specimens shows characteristic differences associated with depth. Secondary minerals, generated by alteration of basaltic rocks, can be characterized by gas release profiles due to their decomposition in the temperature range below 800 °C. Processes of degassing at temperatures higher than 800 °C are correlated to volatiles in the melt and to fluid inclusions of phenocrysts as olivine. Obviously there are no correlations in the degassing characteristics between H2O, CO2 and SO2. The different maxima of the degassing velocity, especially of CO2 and SO2, are indications of the different bonding forces of the volatiles in the melt. First laboratory tests show that these differences may be caused by remelting of sedimentary rocks in the basaltic magma.