||Chaigneau M., Hekinian Roger, Cheminee J.L.
||Bulletin of Volcanology (Springer), 1980 , Vol. 43 , N. 1 , P. 649-661
||Magmatic gases extracted and analysed from basaltic rocks collected in the FAMOUS area near 36° 50' N in the Atlantic ocean show that the total amount of gas included in the samples varies between about 500 pprn to 1600 ppm. The main gaseous phases included in the various types of basalts consist of CO2 (270-700 ppm), CO (150-800 ppm), HCI (100-1000 ppm), H2 (0-50 ppm), SO2 (up to 175 ppm), N2 (up to about 213 ppm) and traces of hydrocarbons (up to about 24 ppm). The relative amount of CO, CO2 and SO2 varies with both the degree of crystallinity of the rock and with fractional crystallization and/or fractional melting.The glassy margin of pillow lavas have a higher CO/C02 ratio than the more crystalline interior. The most fractionated rocks of the series rich in clinopyroxene are depleted in the CO/CO2 ratio and have a higher SO2 content than do the most mafic end members rich in olivine.Early-formed olivine was crystallized in a reducing environment rich in CO and H2 with respect to later formed mineral associations.It is likely that the carbon and sulfur oxidation is taking place at a relatively shallow depth during magmatic ascent or during volcanism.The ocean floor volcanics when compared to subaerial basalts are depleted in SO2 and have on the average ten times more H2. [NOT CONTROLLED OCR]