fig08.htm

Figure 8. Positions of the Elbrus volcanics in the I. V. Nosyrev's diagram.
Note. N=Na2O/[(Al2O3 +Fe2O3)- (K2O+CaO)], K=K2O/[(Al2O3 +Fe2O3)- (Na2O=CaO)]. The line of equal N and K values corresponds to the acid rocks whose Al2O3, CaO, Na2O, and K2O components have eutectic relations, the point with the coordinates of N=K=1 marking a hundred percent eutectic mixture. (1) precaldera and early caldera rhyodacite; (2-4) dacite: (2) dacite of late caldera formation time; (3) dacite of early caldera formation time; (4) dacite of late (Holocene) post-caldera formation cycle.


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