GEO1115_2021_Activity10.4S

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Dec 6, 2023

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THEME 10 – METAMORPHIC ROCKS [ 51/57 : A ] A CTIVITY 10.4S – V ISUAL IDENTIFICATION AND ASSOCIATED QUESTIONS ( /57) Reference material: - Lecture of associated theme (Brightspace) - Glossary ( https://mysite.science.uottawa.ca/dumas/ ) - Reference document “Section of the lab manual” in Brightspace Activity: Answer the questions associated to each of the following pictures. N.B. The rocks shown in the pictures below can be any of the rocks highlighted in yellow in the reference material “Section of the lab manual” (see Table 1). Also, the same rock (rock name, texture) can be tested more than once with different pictures. Metamorphic rock 1 ( /8) a) Indicate whether this rock is foliated or not, and briefly justify your answer. ( /2) No as there are no distinct layers within the rock b) Name the type of metamorphism this rock has most likely undergone, and briefly justify your answer by linking it to the answer given in “a)”. ( /2) Contact metamorphism as it does not produce foliation. c) Briefly explain what this type of metamorphism is (i.e. why, how, and where it occurs). ( /2) Contact metamorphism is mostly influenced by high temperatures and, occurring near to directly against magmatic igneous rocks and usually in relatively low pressure.
d) Knowing that this rock reacts with HCl only when powdered, give the name of the dominant mineral forming this rock. ( /1) Calcite e) Name this rock. ( /1) Marble
Metamorphic rock 2 ( /6) a) Based on the picture, indicate whether this rock has very fine (microscopic) or rather coarse (macroscopic) crystals. ( /1) Fine/microscopic b) Name the type of metamorphism this rock has most likely undergone, and briefly justify your answer. ( /2) Dynamothermal metamorphism as there is clear foliation in the rock therefore it must have experienced some degree of differential pressure. c) Name this rock. ( /1) Slate d) Name a potential protolith of this rock, and specify whether this protolith is an igneous, sedimentary, or metamorphic rock. ( /2) Shale, sedimentary
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Metamorphic rock 3 ( /7) a) Knowing that this rock is practically monomineralic (i.e. composed of a single mineral) and that the dominant mineral easily scratches a glass plate, give the name of the dominant mineral forming this rock as well as its chemical formula. ( /2) Quartz, SiO 2 b) Name this rock. ( /1) Quartzite c) Name the type of metamorphism this rock has most likely undergone, and briefly justify your answer. ( /2) Contact metamorphism as it is a non-foliated rock d) Name a potential protolith of this rock, and give the grain size of the particles of this protolith. ( /2) Sandstone, coarse grains(sand)
Metamorphic rock 4 ( /6) a) Name the type of metamorphism this rock has most likely undergone, and briefly justify your answer. ( /2) Dynamothermal as there is foliation throughout the rock b) Name this rock. ( /1) Schist c) Give an example of a tectonic context where you would expect this rock to form. ( /1) Convergent zones of tectonic plates d) Name a potential sedimentary protolith of this rock, and give the grain size of the particles of this protolith. ( /2) Mudstone, very fine(mud)
Metamorphic rock 5 ( /7) a) Name the type of metamorphism this rock has most likely undergone, and briefly justify your answer. ( /2) Dynamothermal as there is foliation throughout the rock b) Name this rock. ( /1) Gneiss c) Based on the minerals identified in Table 1 of the reference material “Section of the Lab Manual”, give the name of a likely dominant dark mineral in the dark layers of this sample and the name of a likely dominant light mineral in the pale layers of this sample. ( /2) Dark mineral: amphibole Light mineral: quartz d) Give an example of a tectonic context where you would expect this rock to form. ( /1) Convergent zones of tectonic plates e) Name the rock studied (i.e. that is in your Rocks and Minerals kit and highlighted in yellow in the reference material “Section of the Lab Manual”) that shows a similar metamorphic texture and that immediately precedes this sample in terms of metamorphic grade/intensity. ( /1) Schist
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Metamorphic rock 6 ( /8) a) Name the type of metamorphism this rock has most likely undergone, and briefly justify your answer. ( /2) Contact as this is a non-foliated rock b) Knowing that this rock strongly reacts with HCl, give the name of the dominant mineral forming this rock, as well as the chemical formula of this mineral. ( /2) Calcite, CaCO 3 c) Name this rock. ( /1) Marble d) Give an example of a tectonic context where you would expect this rock to form. ( /1) Subduction zone e) Name a potential protolith of this rock and specify whether this protolith is an igneous, sedimentary, or metamorphic rock. ( /2) Limestone, sedimentary
Metamorphic rock 7 ( /9) a) Name the metamorphic texture that is specific to this rock (the texture that defines this rock), define (describe) this texture, and indicate whether it reflects a low or a high metamorphic grade. ( /3) Gneissosity - Medium to coarse crystalline texture with alternating bands of light and dark minerals. - High metamorphic grade b) Name this rock. ( /1) Gneiss c) Based on the minerals identified in Table 1 of the reference material “Section of the Lab Manual”, give the name of the minerals identified by the following arrows in the picture: i. Red arrow, pointing to a hard pinkish mineral: ( /1) Potassium feldspar ii. White arrow, pointing to a hard translucent mineral: ( /1) Quartz iii. Black arrow, pointing to a soft and platy black mineral: ( /1) Biotite d) Based on the dominant mineralogy of this metamorphic rock (i.e. the minerals identified in “c)”), name a potential igneous protolith of this rock (give a precise rock name), and specify whether this protolith rock is of felsic or mafic composition. ( /2) Rhyolite, felsic
Metamorphic rock 8 ( /6) a) Name the metamorphic texture that is specific to this rock (the texture that defines this rock), and indicate whether it reflects a low or a high metamorphic grade. ( /2) Slaty cleavage, low metamorphic grade b) Name this rock. ( /1) Slate c) Name the two rocks studied (i.e. which are in your Rocks and Minerals kit and highlighted in yellow in the reference material “Section of the Lab Manual”) which show a similar metamorphic texture and immediately follow this sample in terms metamorphic grade/intensity. ( /2) Schist and Gneiss d) What could be a protolith common to these three rocks? ( /1) Mudstone and Shale
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