Untold story of Deccan Traps: Role of silicate Liquid Immiscibility by Jyotisankar Ray in MAOPS- Lupine Publishers
Role of liquid immiscibility has immense importance in petro
genesis of basaltic magmas. Roedder, Weiblen postulated that
high silica and high iron glasses of the lunar basaltic rocks have
widespread petro genetic significance. In lunar basalts, generally,
the globules of dark brown glass appear to have composition
equivalent to Pyroxene + Iron ore. On the contrary, it is significant
that Washington initially recognized that the residual glass in
the Deccan Trap basalts should be composition corresponding to
a mixture of augite and magnetite. The role of liquid immiscibility
in basaltic magmas had been graphically depicted by Roedder in terms of SiO2-(FeO+MgO+CaO)-(K2O+Na2O+Al2O3) diagram;
characteristically the liquid immiscibility field in Roedder’s ternary
plot assumes an elongated elliptical geometry relatively away
from SiO2-rich corner. The compositions of terrestrial basalts
like Deccan Trap Palisade diabase sill etc. fall close to the
demarcated liquid immiscibility field of Roedder . The samples
of lunar basalt obtained from Apollo 11 and 12 expeditions were
also plotted in the ternary plot proposed by Roedder .
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