Via_ Chapter5_Exercises-Meta_20200108

Chapter 5: Metamorphic Rocks Adapted by Lyndsay R. Hauber & Joyce M. McBeth (2018) University of Saskatchewan from Deline B, Harris R & Tefend K. (2015) "Laboratory Manual for Introductory Geology". First Edition. Chapter 11 "Metamorphic Rocks" by Karen Tefend, CC BY-SA 4.0. Last edited: 8 Jan 2020 Note: much of the overview material for this chapter is replicated in this exercise section for your reference as you complete the lab. You wull NOT have access to your lab book or notes for the rock and maneral exam! Your name: NSID and Student number: Date and lab section time: TAs' names: Your TAs will check that you have completed the questions at the end of the lab. Please hold on to your lab notes to help you prepare for the rock and mineral quiz and your lab final exam. 5.3 METAMORPHIC ROCK NAMES 5.3.1 Foliated Metamorphic Rocks Differential pressures can cause a metamorphic pattern known as foliation to develop in metamorphosed rocks. There are a few types of foliations that are commonly seen in metamorphic rocks, each foliation type is dependent on the minerals that define the foliation. Gneissic banding (e.g. Figure 5.3) is defined as alternating dark and light mineral bands A R p v & - P Ve, - Lo P i »i*f'-h'v’fi':_-— ;3;,‘,.'-__,;: ‘-J:".'vyy,,,’;.flc' PR ..'., R R R | = 3 o s =% A RIRESE T L e e A 5 _A'_*__:-‘,--. e gt Wm’fifj j e AR S e~ - 2 T e = ;‘.,_', e -'._.4_-.-5"'"_"'.‘!‘:' R AN e .«m&} TR L SR R T e B = TR ¥ o% s NN i Figure 5.3 | Two examples of the metamorphic rock, gneiss. Each rock exhibits the alternating dark and light mineral bands throughout the rock. Source: Karen Tefend (2015) CCBY-SA 3.0 Chapter 5: Metamorphic Rocks 5-E1 |1 dJ

throughout the rock; the metamorphic rock with this type of foliation is called gneiss (pronounced “nice”). The typical minerals seen in the dark coloured bands are biotite and/or amphiboles, whereas the light-colored bands are typically quartz or light-coloured feldspars. The protoliths for gneiss can be any rock that contains more than one mineral, such as shale with its clay minerals and clay-sized quartz and feldspar, or an igneous rock with both dark-coloured ferromagnesian minerals and light-coloured non-ferromagnesian minerals (see Chapter 3 for review). In order for gneissic foliation to develop, temperatures and pressures need to be quite high; for this reason, gneiss rocks represent a high grade of metamorphism. Another type of foliation is defined by the presence of flat or platy minerals, such as muscovite or biotite micas. Metamorphic rocks with a foliation pattern defined by the layering of platy minerals are called schist; the rock name is commonly modified to indicate what mica is present. For example, Figure 5.4 is a photo of a muscovite schist, with garnet present, so the correct name for this rock is a garnet muscovite schist. By convention, when naming a metamorphic rock the mineral in the lowest quantity is mentioned first. The muscovite micas define a very wavy foliation in the rock; this textural pattern of wavy micas is called a schistose foliation (e.g. Figure 5.4B). Shale is usually the protolith for schist; during metamorphism, the very tiny clay minerals in shale recrystallize into micas that are large enough to see unaided. Temperatures and pressures necessary for schistose foliation are not as high as those for gneiss; therefore, schists represent an intermediate grade of metamorphism. A Another metamorphic rock is called phyllite, which is made up of fine crystals that give the rock a shiny appearance. This rock displays phyllitic foliation, which has good, sometimes wrinkled or folded, cleavage. Phyllites are generally formed from a shale protolith, with the Figure 5.4 | Photo of a garnet muscovite . A ’ schist. A) The muscovite micas are large clay minerals in the shale enough to be seen as very shiny minerals . . 3 in the top photograph. B) Side view of the allgnlng and recWStaIIIZIHg as schist shows the distinctive wavy foliation small mica minerals. This made by the platy micas. This st metamorphic rock also contains the index foliation was formed under mineral, garnet. Source: Karen Tefend temperatures and pressures less (2015) CC BY-SA 3.0 Chapter 5: Metamorphic Rocks 5-E1 ]| 2

The calcite mineral in limestone and the quartz sands in sandstone are neither platy minerals, nor are there different coloured minerals in these rocks. The calcite and quartz minerals recrystallize into equigranular, coarse crystals (e.g. Figure 5.2B), and the metamorphic rocks that they make are named by their I composition, not by foliation type. For example, Figure 5.6 is quartzite, a metamorphosed quartz-rich sandstone, while Figure 5.7 shows two examples of marble; note that colour can vary for both marble and quartzite. Quartzite and marble may be hard to identify based on appearance, therefore, you must rely on the properties of the minerals that comprise these I‘OCkS; you may recall that Figure 5.6 | An example of quartzite; a non- : foliated metamorphic rock. Quartzite can appear qllf:.lI'tZ .lS harder Fhan glass, in a variety of colours, but most are fairly light in while limestone is softer than colour. Source: Karen Tefend (2015) CC BY-SA 3.0 Figure 5.7 | Examples of the non-foliated rock, marble. The pink and white colours are common, however some marbles are darker in colour, and others may be white with dark gray markings (like the famous Carrara marble from Italy). Source: Karen Tefend (20135) CC BY-SA 3.0 glass. If you zoom in for a close view of the marble in Figure 5.7, you will see the calcite crystals are fairly large compared to the quartz crystals in the quartzite in Figure 5.6; this can be attributed to the temperature of metamorphism, as higher temperatures result in larger crystals. In order to identify and name metamorphic rocks, a logical first step would be to examine the rock for evidence of any pattern or foliation, and if present, identify which minerals are making the foliation pattern. Non- foliated metamorphic rocks can be identified by the properties defined by their mineral composition. Below is a table summarizing the metamorphic rock types, foliation names, and protolith rock types. Chapter 5: Metamorphic Rocks 5-E1] 4

Texture Characteristics Protolith Metamorphic Rock Name Very fine-grained rock, tends to split 1n parallel fragments (known as slaty cleavage) Shale Slate Fine-grained rock, with the grains only visible as a satin sheen. Similar to slate, but with a satin lustre and may have wrinkled cleavage Shale Foliated Increasing Temperature & Pressure Contains shiny muscovite (light) or biotite (dark) micas, may see other minerals, such as quartz, talc, gamet (note arrow), and amphibole. Has schistose pattern of foliation Shale Schist < Contains alternating bands of light- and dark-coloured munerals (usually biotite or amphibole), called gneissic banding Shale or Igneous Rock Gneiss Equigranular grains of quartz, which has a hardness of 7 Sandstone or Siltstone Quartzite Non-foliated Equigranular grains of calcite, which has a hardness of 4, reacts freely with dilute HCI Limestone Marble Table 5.1 | | Summary chart of metamorphic rocks discussed in this chapter, including the names of some of the possible sedimentary rock and igneous rock protoliths for each metamorphic rock. A metamorphic rock can also be a protolith (e.g. a slate can be a protolith for a schist). Source: Lyndsay Hauber & Joyce M. McBeth (2018) CC BY 4.0 after Karen Tefend (2015) CC BY-SA 3.0 Chapter 5: Metamorphic Rocks 5-E1| 5

10. 11. 12. 13. 14. Sample 53: What is a possible protolith for this rock? a. basalt b. granite c. sandstone d. limestone e. shale Sample 54: This rock has which texture? a. slaty cleavage b. schistose foliation c. gneissic banding d. phyllitic foliation e. non-foliated Sample 54: What is this rock called? marble quartzite schist slate gneiss phyllite Sample 54: What are the P e T dark minerals in this rock? a. flat biotite micas b. tabular amphiboles c. flat muscovite micas d. tabular feldspars Sample 54: What is a possible protolith for this rock? a. an ultramafic rock b. basalt c. limestone d. granite e. sandstone Sample 55: This rock has which texture? slaty cleavage schistose foliation gneissic banding phyllitic foliation non-foliated e TP 15. Sample 55: What is this rock called? marble quartzite schist slate gneiss phyllite 16. Sample 55: What mineral is this rock mainly composed of ? a. biotite b. amphibole c. muscovite d. calcite e. quartz 17. Sample 55: What is a possible protolith for this rock? a. basalt b. granite c. sandstone d. limestone e. shale 18. Sample 56: This rock has which texture? a. slaty cleavage b. schistose foliation c d e Ae o . gneissic banding . phyllitic foliation non-foliated 19. Sample 56: What is this rock called? marble quartzite schist slate gneiss phyllite 20. Sample 56: What is a possible protolith for this rock? o O A T basalt clay sandstone rhyolite shale e o Chapter 5: Metamorphic Rocks 5-E1|7

21. Sample 57: This rock has which texture? slaty cleavage schistose foliation gneissic banding phyllitic foliation e. non-foliated 22.Sample 57: What is this rock called? a. marble quartzite b. schist c. slate d. gneiss e. phyllite 23.Sample 58: This rock has which texture? a. slaty cleavage b. schistose foliation c d e o . gneissic banding . phyllitic foliation non-foliated 24. Sample 58: What is this rock called? marble quartzite schist slate gneiss phyllite 25. Sample 58: What is this rock an example of? a. high grade of @ e e T metamorphism b. intermediate grade of metamorphism c. low grade of metamorphism d. any of the above 26.Sample 59: This rock has which texture? slaty cleavage schistose foliation gneissic banding phyllitic foliation non-foliated e TP 27. Sample 59: What is this rock called? marble quartzite schist slate gneiss phyllite 28. Sample 59: What mineral is this rock mainly composed of? a. biotite b. amphibole c. muscovite d. calcite e. quartz 29.Sample 59: What is this rock an example of? a. high grade of e Ae o metamorphism b. intermediate grade of metamorphism c. low grade of metamorphism d. any of the above 30.Sample 60: This rock has which texture? a. slaty cleavage b. schistose foliation c. gneissic banding d. phyllitic foliation non-foliated 31. Sample 60: What is this rock called: marble quartzite schist slate gneiss phyllite @ O e T Chapter 5: Metamorphic Rocks 5-E1| 8

Table 5-E1 | Metamorphic Rock Notation Chart — Download and fill in this chart as you work through the lab, similar to the chart you completed in the previous labs. You do not have to fill out every column for every rock — just follow along in the lab and determine the properties you are asked about. Source: Lyndsay Hauber (2018) CC BY 4.0 Other properties (e.g., metamorphic grade, Name rotolith, hardness) Identifiable Sample # [Texture . minerals present 51 52 53 54 a5} 56 57 58 59 60 Chapter 5: Metamorphic Rocks 5-E1 ] 10