Textures of Igneous Rocks | Part-2 | Igneous Petrology | Geology | GATE | NET | IIT JAM | UPSC

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This Video is Part-2 of Igneous petrology and contains discussion on Important Igneous rock Textures:
1. Epitaxis
2. Rapakivi
3.Spherulitic
4. Variolitic
5. Cumulate
6.Compositional Zoning
7.Intergrowth texture: Graphic, Myrmekitic, Granophyre
8. Perthitic , anti-perthitic
9. Ophitic texture
10. Magmatic Reaction and Seive texture
The formation and growth of crystals, Involves three Processes:
(1) initial nucleation of the crystal, the rate at which enough of the chemical constituents of a crystal can come together in one place without dissolving.
(2) subsequent crystal growth, the rate at which new constituents can arrive at the surface of the growing crystal. This depends largely on the diffusion rate of the molecules of concern.
(3) diffusion of chemical species (and heat) through the surrounding medium to and from the surface of a growing crystal, Or the rate at which atoms or molecules can move (diffuse) through the liquid.

But the main Factor which determines the texture of Igneous rock is
1. Rate of Cooling. (dT/dt)
Other Factors Include:
1.1 Viscosity: inhibits diffusion rates
1.2 Volatile Content: H20 increases diffusion, CO2 decreases diffusion
1.3 Molecular Concentration
1.4 Complexity of Magma

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