GEOL 1425 1st Edition Lecture 8 Outline of Last Lecture I. What are rocks?II. The rock cycleIII. Igneous rocksOutline of Current Lecture I. Magmatic differentiationII. Bowen’s reaction seriesIII. Magma chambersIV. What to know for test about Igneous rocks…Current Lecture—Igneous Rocks IIV. Magmatic differentiationA. Rocks of various composition arise form a uniform parent magma.VI. Bowen’s reaction seriesA. Bowen was the first to demonstrate that single magma body could create many varieties of igneous rocks.B. As magma temperature decreases, minerals crystalize in an ordered series. Minerals with higher melting points (ex- olivine) crystalize before minerals with lower melting points (ex- potassium feldspar and quartz).C. Compositions of igneous rocks: i. Ultramafic composition= describes rocks composed of the earliest minerals. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.ii. Mafic (or basaltic) composition= describes rocks composed of pyroxene and calcium-rich feldspariii. Andesitic (or intermediate) composition= rocks composed of amphibole and intermediate plagioclase feldspariv. Felsic (or granitic) composition= rocks formed from the last minerals to crystalizev.VII. Magma chambersA. Magma forms in 3 ways:i. Oceanic plates descent into asthenosphere and melt between the edge ofthe overriding tectonic plateii. Forms from the decompression melting of hot mantle rock at divergent plate boundariesiii. Extremely hot rock rising from the mantle can melt as it travels to the crust.B. Once magma is created, it is collected in a magma chamber, and magma differentiation occurs according to Bowen’s reaction series. The magma may alsomelt surrounding rock, incorporating those minerals. Magma bodies may also come together forming a composite magma with a hybrid composition. VIII. What you need to know for the test about Igneous rocks. (Answers will be posted on the Test 2 Review!)A. Details of Gabbros, porphyrys, and phenocrystsB. What is the effect of water on rock melting?C. Magmatic differentiationD. Igneous intrusive bodiesE. Decompression meltingF. Intermediate igneous
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