Earth Science


Principals of Earth Science


Lab 4


8) Basalt is a mafic rock and aphanitic, it is mosaic of microscopic crystals, has dull luster and smoother surfaces. Created from rapid crystallization of magma, at or near the surface or in chilled margins.


9) Gabbro is also a mafic rock and phaneritic, consist of mosaic of large, macroscopic crystals, shiny luster and rough surfaces. It is formed by slow crystallization of magma at considerable depth below the surface.


10) Felsite (rhyolite) is felsic and aphanitic, is made of mosaic of microscopic crystals, dull luster and smoother surfaces. Formed from rapid crystallization of magma, at or near the surface or in chilled margins.


11) Granite is a felsic rock which is phaneritic, it is mosaic of large, macroscopic crystals, shiny luster, and rough surfaces. It is formed by slow crystallization of magma, at a considerable depth below the surface.


12) Felsite Porphyry is a felsic/intermediate rock which is aphanitic porphyritic, it has large crystals embedded in aphanitic matrix. It is formed by two-stage crystallization, first slow crystallization, then rapied crystallization near the surface.


13) Basalt Porphyry is a mafic rock and is aphanitic porphyritic, it has large crystals embedded in aphanitic matrix and is formed in two-stage crystallization, first slow crystallization, then rapid crystallization near the surface.


III.


The oldest intrusion on the diagram is granite. Granite is a felsic rock which is phaneritic, it is mosaic of large, macroscopic crystals, shiny luster, and rough surfaces. It is formed by slow crystallization of magma, at a considerable depth below the surface. The type of intrusion here is a batholith which is a large mass of igneous rock that formed when magma was emplaced at depth, crystallized, and subsequently exposed by erosion.


The second oldest rock type is basalt. Basalt is a mafic rock and aphanitic, it is mosaic of microscopic crystals, has dull luster and smoother surfaces. Created from rapid crystallization of magma, at or near the surface or in chilled margins. The type of intrusion represented here is a sill. It was formed when magma was injected along sedimentary bedding surfaces.


The third oldest is gabbro. ) Gabbro is also a mafic rock and phaneritic, it consist of mosaic of large, macroscopic crystals, shiny luster and rough surfaces. It is formed by slow crystallization of magma at considerable depth below the surface. The type of intrusion represented here is a laccolith, which is a massive ingneous body intruded between preexisting strata.


The youngest is felsite porphyry. Felsite Porphyry is a felsic/intermediate rock which is aphanitic porphyritic, it has large crystals embedded in aphanitic matrix. It is formed by two-stage crystallization, first slow crystallization, then rapid crystallization near the surface. This type of intrusion is called a dike. It was produced when magma was injected into fractures that cut across rock layers