Chapter 8 Metamorphism and Metamorphic Rocks

Chapter 8 Metamorphism and Metamorphic Rocks Earth: An Introduction to Physical Geology, 9e (Tarbuck/Lutgens)

1 Mul 1)

2 Which of the following forms at the highest grade of regional metamorphism? A)

3 hornfels B)

4 schist C)

5 slate D)

6 phyllite Answer:

7 B Diff: 1

8 What platy, parallel, mineral grains are the most visual aspect of foliated metamorphic rocks? A)

9 micas B)

10 feldspars C)

11 carbonates D)

12 quartz Answer:

13 A Diff: 1

14 What major change occurs during metamorphism of limestone to marble? A)

15 calcite grains grow larger and increase in size B)

16 clays crystallize to micas, forming a highly foliated, mica-rich rock C)

17 limestone grains react to form quartz and feldspars D)

18 calcite grains are dissolved away leaving only marble crystals Answer:

19 A Diff: 1

20 Which grade metamorphic rock, composed of extremely fine-sized mica and other mineral grains, low- typically exhibits well-developed rock cleavage? A)

21 schist B)

22 hornfels C)

23 quartzite D)

24 slate Answer:

25 D Diff: 1

26 Match the rock with the appropriate description.

A. hornfels B. marble C. gneiss D. phyllite

27 ______forms by contact metamorphism of mudstones and shales Answer:

28 A Diff: 1

29 ______foliated, fine-grained metamorphic rock formed from mudstone and shale Answer:

30 D Diff: 1

31 ______nonfoliated metamorphic rock consisting mostly of calcite Answer:

32 B Diff: 1

33 ______grained, metamorphic rock with alternating bands or stringers of light and dark minerals coarse- Answer:

34 C Diff: 1

35 ______is thought to form by partial melting and in situ crystallization of the melted portion. A)

36 Magmatite B)

37 Magnetite C)

38 Migmatite D)

39 Megatite Answer:

40 C Diff: 1

41 Tektites originate in what metamorphic environment? A)

42 low pressure and high temperature associated with volcanism B)

43 high temperatures associated with meteorite impacts C)

44 very high pressures and temperatures associated with deep subduction D)

45 high temperatures and shearing stresses in an oceanic-crust transform fault Answer:

46 B Diff: 1

47 Which the following is not likely to be genetically associated with impact of an asteroid or large one of meteorite? A)

48 tektites B)

49 blueschists C)

50 coesite D)

51 impact crater Answer:

52 B Diff: 1

53 12)

54 Which of the following statements concerning slate is not true? A)

55 forms from shales and mudstones B)

56 has abundant, coarse-grained mica C)

57 rock cleavage is common D)

58 sedimentary features may be visible Answer:

59 B Diff: 1

60 ______strong, parallel alignment of coarse mica flakes and/or of different mineral bands in a is a metamorphic rock. A)

61 Rock cleavage B)

62 Foliation C)

63 Stress streaking D)

64 Marbleizing Answer:

65 B Diff: 1

66 ______is a nonfoliated rock formed by contact metamorphism of a shale or mudstone. A)

67 Schist B)

68 Marble C)

69 Gneiss D)

70 Hornfels Answer:

71 D Diff: 1

72 Which of the following would exhibit sheared and mechanically fragmented rocks? A)

73 fault movements at shallow depths B)

74 intense compression in a deep-seated, regional metamorphic zone C)

75 heating of shales and mudstones near a pluton D)

76 regional metamorphism of pyroclastic volcanic rocks Answer:

77 A Diff: 1

78 Which of the following best describes the conditions of contact metamorphism? A)

79 Pressures are rock is deeply buried, and temperatures are raised by the Earth's internal heat. very high, the B)

80 Pressures are rock is in the upper part of the crust, and heat is supplied from a nearby magma body. fairly low, the C)

81 Heat is generated by shearing and mechanical movements along faults. D)

82 Depths are but temperatures and pressures are so high that the rocks begin to partially melt. fairly shallow, Answer:

83 B Diff: 1

84 17)

85 ______forms from the metamorphism of limestone or dolostone. A)

86 Migmatite B)

87 Amphibolite C)

88 Marble D)

89 Quartzite Answer:

90 C Diff: 1

91 What foliated, metamorphic rock is texturally intermediate between slate and schist? A)

92 fault breccia B)

93 phyllite C)

94 quartzite D)

95 gneiss Answer:

96 B Diff: 1

97 ______characterized by the segregation of light- and dark-colored minerals into thin layers or bands. is A)

98 Garnet hornfels B)

99 Granitic gneiss C)

100 Slate D)

102 B Diff: 1

103 What foliation results from the parallel alignment of abundant, coarse-grained, mica flakes in a type of metamorphic rock? A)

104 schistosity B)

105 gneissic banding C)

106 slaty cleavage D)

107 phyllitic structure Answer:

108 A Diff: 1

109 Which of the following metamorphic rocks could be used to neutralize acidic mine waters? A)

110 granite gneiss B)

111 quartzite C)

112 slate D)

113 marble Answer:

114 D Diff: 1

115 22)

116 Which of following lists the rocks in the order of increasing grain size and increasing grade of the metamorphism? A)

117 phyllite, slate, schist B)

118 schist, slate, phyllite C)

119 slate, phyllite, schist D)

120 slate, schist, phyllite Answer:

121 C Diff: 1

122 ______is typically formed by metamorphism of a sandstone. A)

123 Marble B)

124 Slate C)

125 Amphibolite D)

127 D Diff: 1

128 Which of following rocks would exhibit visible, textural evidence of having undergone some partial the melting? A)

129 fault breccia B)

130 migmatite C)

131 slate D)

132 foliated hornfels Answer:

133 B Diff: 1

134 What is the major source of heat for contact metamorphism? A)

135 deep burial and heat from the Earth's interior B)

136 heat from grinding and shearing on faults C)

137 heat from the spontaneous decomposition of micas and feldspars D)

138 heat from a nearby magma body Answer:

139 D Diff: 1

140 In which setting would regional metamorphism be most likely? A)

141 at shallow depths below an oceanic ridge or rift zone B)

142 at shallow depths along major transform faults in the continental crust C)

143 at great depths in the crust where two continents are colliding D)

144 at shallow depths beneath the seafloor where water pressures are immense Answer:

145 C Diff: 2

146 27)

147 Graphite is identified in a particular schist. Which one of the following conclusions is justified? A)

148 The rock also contains diamonds; both are crystalline forms of the element carbon. B)

149 The schist formed from a quartz-rich, sedimentary limestone. C)

150 The graphite lubricated shearing movements along a fault, causing a schist to form. D)

151 The pre- metamorphic rock was a shale or mudstone containing organic matter. Answer:

152 D Diff: 2

153 Amphib foliated metamorphic rock composed principally of hornblende and plagioclase. How does it olite is a form? A)

154 by contact metamorphism of sandstone along the contact with a granitic batholith B)

155 by regional metamorphism of volcanic rocks such as andesite and basalt C)

156 by gouging and crushing of limestone along a fault D)

157 by the impact of an asteroid on interbedded sandstone and shale Answer:

158 B Diff: 1

159 What term describes the zone of contact metamorphism surrounding an intrusive magma body? A)

160 aura B)

161 auricle C)

162 oracle D)

163 aureole Answer:

164 D Diff: 1

165 During metamorphism, what is the major effect of chemically active fluids? A)

166 increase the pressures in deeply buried, regional-metamorphic zones B)

167 aid in the movement of dissolved silicate constituents and facilitate growth of the mineral grains C)

168 prevent partial melting so solid rocks can undergo very high temperature regional metamorphism D)

169 facilitate the formation of schistosity and gneissic banding in hornfels and slates Answer:

170 B Diff: 1

171 What two, metamorphic rocks are composed predominantly of single minerals? A)

172 mica schist and granitic gneiss B)

173 fault breccia and graphitic schist C)

174 garnet schist and hornfels D)

175 marble and quartzite Answer:

176 D Diff: 1

177 32)

178 A forms at very high pressures but moderately low temperatures associated with subduction of ______oceanic crust and sediments. A)

179 mylonite B)

180 migmatite C)

181 biotite marble D)

182 blueschist Answer:

183 D Diff: 1

184 Wo Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern. 1)

185 A) pressure B) recrystallization C) melting D) chemical fluids Answer:

186 melting Diff: 1

187 A) porphyroblastic B) slaty cleavage C) schistosity D) gneissic texture Answer:

188 porphyroblastic Diff: 1

189 A) aureole B) hornfels C) skarn D) schist Answer:

190 schist Diff: 2

191 A) phyllite B) quartzite C) slate D) schist Answer:

192 quartzite Diff: 1

193 Tru 1)

194 Partial melting is an important process in the formation of migmatites. Answer:

195 TRUE Diff: 1

196 Slate and schist are both derived by metamorphism of shales and mudstones. Answer:

197 TRUE Diff: 1

198 Hornfels metamorphic rocks produced at great depths and high temperatures associated with regional are metamorphism. Answer:

199 FALSE Diff: 1

200 Calcite is mineral constituent of the sedimentary rock limestone and of the metamorphic rock marble. the main Answer:

201 TRUE Diff: 1

202 5)

203 Metamor rocks formed during episodes of mountain building typically show textural characteristics phic indicative of shearing stress and deformation. Answer:

204 TRUE Diff: 1

205 Amphib olites have gneissic textures and form by regional metamorphism of granites and rhyolites. Answer:

206 FALSE Diff: 1

207 At high s and elevated temperatures of regional metamorphism, silicate rocks are more resistant to pressure flowage and deformation than at low temperatures and pressures. Answer:

208 FALSE Diff: 1

209 Foliated phic rocks are composed largely of equidimensional grains of minerals such as quartz and metamor calcite. Answer:

210 FALSE Diff: 1

211 Rock or slaty cleavage in slates is largely a consequence of abundant, parallel-aligned, very fine- cleavage grained mica flakes in the rock. Answer:

212 TRUE Diff: 1

213 Muscovit e, biotite, and chlorite are common minerals found in phyllites and schists. Answer:

214 TRUE Diff: 1

215 The distinctive layers or bands of different minerals in gneisses may be complexly folded. Answer:

216 TRUE Diff: 1

217 Quartzit metaconglomerates are formed along faults by intensive fracturing and fragmentation of es and conglomerate beds and quartz veins. Answer:

218 FALSE Diff: 1

219 High- regional metamorphism produces significant and recognizable changes in the textures and grade, mineral compositions of rocks. Answer:

220 TRUE Diff: 1

221 Talc and graphite are very soft minerals found in some schists. Answer:

222 TRUE Diff: 1

223 15)

224 Three factors involved in metamorphism are elevated temperature, elevated pressure, and the major chemical action of hot fluids. Answer:

225 TRUE Diff: 1

226 During phism, most rock is composed of solid mineral grains, but small amounts of hot fluids or metamor partial melting may facilitate the metamorphic process. Answer:

227 TRUE Diff: 1

228 Sho 1)

229 Give the name of a rock formed by regional metamorphism of a conglomerate. Answer:

230 metaconglomerate Diff: 1

231 Which metamorphism occurs specifically in the heated zone around a pluton or other body of magma? type of Answer:

232 contact Diff: 1

233 List the three most important agents of metamorphism. Answer:

234 heat, pressure, chemically active fluids

235 Diff: 1

236 What type of sedimentary rock is typically metamorphosed to form slates or phyllites? Answer:

237 shale or mudstone Diff: 1

238 Foliation metamorphic rocks is mainly evident in the parallel alignment of certain mineral grains. What in are they? Answer:

239 micas Diff: 1

240 Which phic rock or rocks exhibit alternating layers or bands of different light- and dark-colored metamor minerals? Answer:

241 gneiss Diff: 1

242 Which phic rock, widely used for monuments and buildings, would deteriorate significantly in contact metamor with acid rain? Answer:

243 marble Diff: 1

244 What banded, metamorphic rocks show good evidence for having formed by partial melting? strongly Answer:

245 migmatite Diff: 1

246 9)

247 What phic rock forms by intense ductile deformation along fault zones at depth in the Earth? metamor Answer:

248 mylonite Diff: 1

249 Crit Use complete sentences, correct spelling, and the information presented in Chapter 8 to answer the questions below 1)

250 Is it possible to determine the original parent rock (called a protolith) prior to metamorphism? Why always or why not? List three protoliths and give a possible metamorphic equivalent for each one. Diff: 3

251 Briefly regional metamorphism is related to plate boundaries. Are certain types of metamorphic rocks outline indicative of particular plate boundaries or tectonic settings? Give two or three examples of how such rocks and indicate the tectonic environment they represent. Diff: 3

252 Is the metamorphic rock always indicative of the conditions (degree of metamorphism) under which texture it formed? (Hint: Think about the protolith and how it may influence the resulting of a metamorphic rock.) Diff: 2

253 Vis 1)

254 What type of stress (pressure ) is illustrate d in the diagram below?

Answer:

255 confining pressure Diff: 1

256 What type of stress (pressure ) is illustrate d in the diagram below?

Answer:

257 differential stress Diff: 1

258 Carefully examine the photogra ph below of a metamor phic rock sample. The sample is shown as its actual size.

Is this rock foliated or nonfoliated? a) ______What is the name of this metamorphic rock? b) ______Consider how this rock got its texture. Was is compressed from top to bottom or from side to side? c) ______Answer:

259 a) foliated b) gneiss c) side to side

260 Diff: 1

261 4)

262 Carefully examine the cross section below of a subducti on zone, and note the areas labeled A, B, or C.

At which location (A, B, or C) would a metamorphic regime occur that is characterized by high temperature and high pressure? a) ______At which location (A, B, or C) would a metamorphic regime occur that is characterized by high temperature and low pressure? b) ______At which location (A, B, or C) would a metamorphic regime occur that is characterized by low temperature and high pressure? c) ______At which location (A, B, and C) would blueschist form? d) ______Answer:

263 a) Box B b) Box C c) Box A d) Box A

264 Diff: 2