Basalts magma degassing

Webster J. D., Kinzler R. J., and Mathez E. A. (1999) Chloride and water solubility in basalt and andesite melts and implications for magma degassing. Geochim. Cosmochim. Acta 63, 729-738. 

Gerlach T. M. (1989) Degassing of carbon dioxide from basaltic magma at spreading centers 2. Mid-ocean ridge basalts. J. Voleanol Geotherm. Res. 39, 221. 

Mathez, E.A., 1984. Influence of degassing on oxidation states of basaltic magmas. Nature, 310, 371-5. 

Model of Pb, Bi, and Po degassing. For a purpose of clarity, it is considered here that the degassing reservoir has reached a chemical steady-state (i.e., radionuclide activities in the degassing reservoir are constant, that is d(Ik)iydt = 0 in Eqn. 4). This assumption usually is valid for very active basaltic systems like Stromboli, where erupted products display an almost constant chemical composition as shown above, and where the degassing reservoir is quickly and continuously replenished with deep undegassed magma. 

Primary basaltic glass inclusions trapped in olivines and representative of magmas from active volcanoes have been studied by X-ray spectromicroscopy, in order to understand the excess degassing of sulfur dioxide (S02) [31]. The p-XANES experiments at the sulfur K edge were carried out on the x-ray microspectroscopy beamline ID21 (ESRF, France) with a spot size range from 0.5x0.5 pm2. 

The oceanic crust is a source of CO2 when magma upwelling at mid-ocean ridges degasses and later is a sink when circulating sea water reacts with the sea floor at low temperatures. For simplicity, we assume that at first the basalt degasses completely and later, when the basalt is cool, CO2 is added to it by reaction with sea... 

Alternatively, magma from the MORE source may mix either directly with that of a gas-rich source (with solar Ne and a high He/" He ratio) to produce Loihi compositions, or may be subject to preferential loss of Ne through degassing before mixing with the gas-rich source to produce Icelandic basalts (Moreira et al. 2001 Dixon 2002). 

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