IgrockIDClass(1)

IgrockIDClass(1) - GEOS444 Petrology, Spring 2011 Dr....

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GEOS444 Petrology, Spring 2011 Name Dr. Matthew L. Gorring IGNEOUS ROCK IDENTIFICATION AND CLASSIFICATION FOR EVERY SAMPLE: Estimate the hand sample’s overall color and classify the rock as ultramafic, mafic, intermediate , or felsic . Compare your interpretation with the SiO 2 wt% values in Table 1. Your interpretation should be more or less consistent. Describe the texture with the basic terms ( aphanitic, phaneritic, porphyritic ) and determine whether the rock is volcanic (extrusive) or plutonic (intrusive). IF VOLCANIC, then do the following: 1. If the rock is porphyritic, identify the phenocryst mineralogy (usually only one mineral) ONLY . Use both hand sample and thin section to do this. You do not have to identify the “matrix” minerals. 2. Use the major element data in Table 1 and the Total Alkali (Na 2 O + K 2 O) vs. Silica (SiO 2 ) classification diagram (Fig. 2.4 in textbook or handout) to name the rock. Show your work by plotting the Box # on the Na 2 O + K 2 O vs. SiO
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IgrockIDClass(1) - GEOS444 Petrology, Spring 2011 Dr....

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