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General Geology: Magmatic rocks. Instructor: Prof. Dr. Boris Natalin. Rock types. Magmatic Sedimentary Metamorphic. Magmatic rocks in the rock cycle. Terminology. Magma – molten rock Lava – magma on the surface Volcanic (Extrusive ) rocks Plutonic (Intrusive ) rocks.
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General Geology: Magmatic rocks Instructor: Prof. Dr. Boris Natalin
Rock types • Magmatic • Sedimentary • Metamorphic
Terminology • Magma – molten rock • Lava – magma on the surface • Volcanic (Extrusive) rocks • Plutonic (Intrusive) rocks
Crystallization of magma • Melting of rocks • Crystallization of magma • Rate of cooling and crystal size • Volatiles
Granite Mackenzie et al. 1988
Crystallization of magma • cooling rate • crystallization order • vesicles Texture– A geologic structure
Magmatic texture Intrusive • Phaneritic - • Porphyrictic • Aphanitic - • Porphyritic (with fine-grained groundmass): • Glassy – • Existence of volatiles produces bubbles (vesicles) • Pyroclastic Extrusive
Aphanitic Phaneritic Porphyrictic Glassy
Voids are remnant of gas bubbles Vesicular texture
Pyroclastic texture Tuff
Pyroclastic rocks Silica-rich rocks (light color)
Magmatic differentiation Earlier and denser crystals settle on the bottom and walls of magmatic chamber Remaining melt crystallizes in different places and thus it has different composition
Andesitic rocks: andesite and diorite Andesite porphyry
Thin section of andesite porphyry groundmass phenocryst
The structures that result from the emplacement of igneous material at depth are calledplutons
Classification of plutons • Shape • Relationships with surrounding rocks