Nitrogen mantle sources

The reaction is performed in a dry nitrogen atmosphere, but no precautions need be taken during the purification steps. A 1-1., three-necked flask is equipped with a magnetic stirrer and a Glass Col heating mantle. One neck of the flask is fitted with a gas inlet tube which will protrude beneath the surface of the 300 ml. of solvent to be used and is attached to a source of carbon monoxide. The second neck of the flask is fitted with an efficient reflux condenser topped with a T tube, one side of... 

Using an approach analogous to that for carbon, Sano et al. (1998, 2001) have attempted to understand the nitrogen cycle at subduction zones. Again, the problem is to identify and quantify the various contributory sources to the volcanic output. At subduction zones, there are three major sources of nitrogen the mantle (M), atmosphere (A), and subducted sediments (S), and each has a diagnostic value and N2/ Ar... 

This would indicate that a significant proportion (up to 70%) of the N2 could be derived from a subducted sedimentary or crustal source. The situation is reversed in the case of back-arc basin glasses, which have significantly lower values (—2.7%c to - -1.9%c) this implies that up to 70% of the nitrogen could be mantle-derived (Sano et ai, 2001). A first-order conclusion from these observations is that N2 is efficiently recycled from the subducting slab to the atmosphere and hydrosphere through arc (and back-arc volcanism) (see also Fischer et al, 2002). 

Many of the important characteristics of the atmosphere are related to the concentrations of particular molecular species, such as O2. Here the absolute abundances of carbon, nitrogen, and hydrogen (as H2O) as supplied from the mantle are considered in the context of models of noble gas degassing from the solid Earth. A convenient reference for comparing surface volatile inventories to mantle reservoirs is obtained by dividing the surface volatiles into the mass of the upper mantle, the minimum size of the source reservoir. However, this should not be taken to imply a particular model of degassing. 

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