The interplay between crystallization, replenishment and hybridization in large felsic magma chambers

摘要: Abstract While hybridized granitoid magmas are readily identifiable, the mechanisms of hybridization in large crustal magma chambers so not clearly understood. Characteristic features hybrid granitoids (1) both and included enclaves commonly hybrids, as shown by mineralogy, geochemistry isotopes; (2) mixing seen zoned plutons synplutonic dykes occurred early; (3) plagioclase phenocrysts show very complex life histories growth dissolution; (4) mafic end-members hybrids fractionated (5) stratification subvolcanic is uncommon, has been identified some deeper level plutons. Hybridization must overcome tendency to form a stable dense underlying less felsic magma. Experimental work with analogues theoretical considerations reveal severe thermal, rheological dynamical limitations on mixing: only similar (composition, temperature) likely mix homogeneity, moderately silicic be produced. However, “impossibly” do exist. Synchronous, interactive fractional crystallization may provide mechanism for magmas, following manner. A intrudes into base stratified cooled against it. Crystallization upper boundary layer yields an eventually buoyant residual melt that overturns mixes adjacent stratum chamber. Subsequently, released pf this, now-hybrid zone adjacent, more zones. Thus, suite progressively formed. Density inhibitions generation relatively low density melts. As proceeds, later injections preserved composed In this process, physically dynamically-thermally directly interact, homogeneity. Finally, simply endmembers mix, but whole “intermediate” participate, ranging from through pairs magmas. Direct between primary occurs at beginning.