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Unformatted text preview: 1 Lab 3 Ultramafic and Mafic plutonic rocks In this lab, you will learn how distinguish between olivine, clinopyroxene and orthopyroxene in hand specimen, and how to identify them quickly and efficiently in thin section. For all samples with a hand specimen, be sure you match (or at least try) the minerals . The lab is also designed to familiarize you with the classification of mafic and ultramafic plutonic rocks and their most common textures. You will therefore be using the classification schemes that you learnt in lecture (see attached), as well as last week's handout on textures. Specific attention is paid to the textures that result from the process of fractional crystallization, and its impact on the evolution of the magma, and the rocks that form. Part A 2 Mantle rocks 920188: Lherzolite 1- List the minerals in sample 33 in order of abundance, estimating the modes of each. 2- From your lecture notes, what is the approximate depth (or depth range) at which this rock may have formed? What mineral (or minerals) led you to this conclusion? 94326 Harzburgite 1- List the minerals in this sample in order of abundance. 2- What are the differences between this sample and the lherzolite? 3- Why are harzburgites often called: "depleted mantle"? Explain in detail....
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- Fall '11