The extremely high viscosities of high-silica liquids mean that intermediate and high-silica magmas exist deep within the laminar range of fluid behavior. Many common interpretations of layering in plutonic rocks rely on analogies with sedimentation in water, but for such high-viscosity liquids (including interstitial liquid in partially crystallized intermediate magmas), these analogies cannot be correct. Particle Reynolds numbers for high-silica liquids are exceedingly small, on the order of 10−6 or less. In such a regime, inertia is negligible, and everyday experience is inapplicable. Layering and other pseudo-sedimentary structures in granodiorites and granites likely arise from processes such as chemical diffusion, self-organization, and crystal ripening.

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