GEOL107 Lecture Notes - Lecture 3: Feldspar, Gabbro, Peridotite
18 Sep 2017
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Document Summary
Rock - naturally occurring aggregate (combination) of minerals. Igneous - origin from cooling and subsequent crystallization (solidification) of magma. Magma - hot (>1100c), liquid, melt of elements. Major elements present are o,si,al, fe, ca, na, k and mg. Magmas have range of varying compositions, two general end member type of. Composed of ~50% silica (sio2), have higher amounts (up to 30%) iron, magnesium and calcium, and lower amounts (about 3%) potassium, sodium, and dissolved gases. Silicic (felsic) magmas composed of ~65-77% sio2, have lower amounts (5-6%) iron, magnesium and calcium, and higher amounts (up to 10%) of potassium, sodium and dissolved gases. Macroscopic in size (can see individual crystals of minerals. Minerals are microscopic, cannot see individual crystals of minerals. Texture indicates fast cooling of magma without magnification. Composition of igneous rocks determined by minerals - three major types. Mafic - igneous rocks that contain lots of magnesium and iron rich minerals with plagioclase feldspar.
