Liam Murphy - GEOL200 - Lab Assignment 02 [Marked]

a. Describe how the rock in Figure 5.3B could have formed (i.e., the process), starting with a high- temperature magma originating in the Asthenosphere. (due to it being a higher density than the silica-rich rocks above, known as magmatic underplating) and provides additional heat to the continental crust which will allow a partial melting of the crust producing a Felsic Magma. This Felsic Magma will collect ° Mafic Magma originating within the Asthenosphere rises to the base layer of the Continental Crust where it pools as a liquid 5 and form Diapirs an% ris{e to a higher level within the crust and begin solidifying and crystallizing as it rises closer to the earth's surface. o b. What is the lowest melting temperature of a magma formed by the melting of light-coloured sediments? Describe the chemistry. 3 -; ® The lowest temperature shown within the zone of partial melting is ~1100°C which would allow the rock to partially melt but not all the way (hence the zone of partial melting). Should enough water be present within the rock at such high temperatures the resulting effect is the rocks melting temperature has been lowered by at least a few hundred degrees (Celsiug)this iskno‘/n/a% Flux Melting. Theoretically the lowest melting temperature for this type of rock could range frgm 600°C - 800<C during the partial melting process the contents of the continental crust melté forming a Felsic Magma which collects and orms diapirs which rise closer to the surface as granitic plutons. 5 c. “Could é“granite ultimately form from a magma such as that described in b? Ho 6. Examine samples 25-32 of the Athabasca University Rock Samples Kit. Using the discussion of igneous rock textures provided on pages 55-59 and 80-89 of the Plummer, Carlson, and Hammersley textbook, answer the following questions. a. Which of the samples above have a phaneritic texture? What does this texture indicate about the conditions under which these rocks formed? "\\ ~1\Wo Phaneritic Texture ‘\//N;;-'Phaneritic Texture M ~Qfip Sample # Sample Name || Sample # Sample Name ] 5‘ 25 Diorite | 28 Andesite E 26 Gabbro | 29 Basalt 27 Granite 30 Obsidian k . \ ) p o 31 Pumice . g & ks e ; 32 Rhyolite -8 ¥ = T S ~ . ¥ e = = . A Phaneritic texture indicates that these rocks began the cooliA ation process whilst still within the magma chamber rather than a rapid cooling on the earth’s surface. This cooling process produced a larger crystal and grain size within the rock. b. Describe the texture of sample 29, and give a hame to this rock. How does such a texture originate? What is the origin of the voids/bubbles in sample 31? 5 . Sample #: 29 - Sample Name: Basalt l' Sample Texture: Aphanitic : M - An Aphanitic texture would originate from the rapid cooling of magma. ° The voids/bubbles formed within the Pumice rock (Sample 31) are from trapped pockets of gas within the lava/magma as it cools leaving a void/bubble. = c. List the minerals present in sample 27, and give approximate percentages of each. Use Figure 2.2 on the following page in your estimation of percentages. Describe the texture of the sample,.and name the Pt rogk. 5, U | X8 e i 008 3 i Sample Reference: Sample 27 Sample#: 27 Sample Name: Granite Minerals Present And % of each: Quartz (45%) Plagioclase (45%) Alkali Feldspar (10%) Texture: Phaneritic Texture ¥ $ TN i i ™ \\/\JU\(;QA\, ! 73 At g i s ) _ Visual Reference(s) s ; ol kR 1 b 2 F g J ¥ 4 R i v ey i e Liam Murphy y Unit 3: Igneous Rock GEOL 200 N Lab Assignment #2 Athabasca University Page 3 of 5 June 11%, 2021