Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Earth Systems 3209 Unit: 3 Earth’s Materials Reference: Chapters 2, 3, 6, 7; Appendix A & B

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Metamorphic Textures Unit 3: Topic 5.2 Focus on...  identifying and describing how different metamorphic textures form.  identifying various metamorphic rocks that exemplify each texture.  describing the result metamorphism has on selected parent rocks including; limestone, sandstone, shale and granite.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Metamorphic Textures  Metamorphism literally means to “change form.”  The degree of metamorphism is reflected in the rocks texture and mineralogy. METAMORPHISM CHANGES TEXTURE  Two textures are formed as a result of metamorphism; 1)Foliated Texture 2)Non-Foliated Texture Text Reference: Pages

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 1)Alignment of minerals  Directional stress causes minerals to align when recrystallizing. The orientation of these minerals is usually perpendicular to the compressional forces (direction of stress).  This gives the resulting metamorphic rock a layered appearance.  This is common during high-grade metamorphism and often produces a foliated texture. Example: Gneiss Gneiss Metamorphic Textures Depends On;

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 2) Recrystallization of minerals  Pressure causes minerals to recrystallize which generally forms larger, more dense crystals.  The recrystallization process causes some metamorphic rocks to display visible crystals with no visible evidence of the original mineral grains. For example, quartz sandstone changes to form quartzite.  This is common during low-grade metamorphism and often produces a non-foliated texture. Quartz Sandstone Quartzite Recrystallizes Metamorphic Textures Depends On;

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  Two types of textures: 1)Foliated (i.e. layered or banded) 2)Non-foliated.  Note that the texture of a metamorphic rock is usually coarser than the parent rock (i.e. previous rock).  Note that volume is often reduced as increased pressure is often the result of metamorphism. Foliated Non-foliated Metamorphic Textures

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  Two textures are formed as a result of metamorphism: 1) Foliated Texture  Results when the minerals of a rock are brought into parallel alignment during recrystallization.  Produces a banded or layered appearance.  Examples: Slate, Phyllite, Schist & Gniess  Granite when metamorphosed forms Gneiss. Metamorphic Textures

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  Two textures are formed as a result of metamorphism: 2) Non-Foliated Texture  Results when the minerals of a rock are recrystallized creating uniform sized crystals with no visible foliation.  This occurs when limestone (consist of pure calcite) undergoes metamorphism and the smaller calcite crystals combine to form larger interlocking crystals. This process of recrystallization of calcite forms Marble.  Examples: Quartzite & Marble Marble Metamorphic Textures

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Metamorphism of Parent Rocks:  Note that some parent rocks include 1)limestone, sandstone, and shale which are all sedimentary rocks. 2)granite is an igneous rock.  Examples of foliated and non-foliated metamorphic rocks include: 1)Foliated – slate, phyllite, schist, and gneiss 2)Non-foliated – quartzite and marble.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Parent RockMetamorphic Rock Limestone (Sedimentary)Marble Sandstone (Sedimentary)Quartzite Shale (Sedimentary) Slate (Phyllite – Schist - Gniess) Granite (Igneous)Gniess Changes to Metamorphism of Parent Rocks: Changes to

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 1: Which feature identifies the metamorphic rock below? (A) bedding(B) foliation (C) striation(D) varves Which rock type forms from the recrystalization and reorganizing of minerals? (A) Igneous(B) Metamorphic (C) Sedimentary(D) Volcanic

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 2: Which is the correct sequence in the metamorphism of shale? (A) phyllite - gneiss - slate - schist (B) phyllite - slate - gneiss - schist (C) slate - phyllite - schist - gneiss (D) slate - schist - phyllite - gneiss

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Your Turn... Take the time and complete the following questions... (Solutions to follow) Question: Using examples, distinguish between foliated and non-foliated metamorphic rocks.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Solutions... Question: Using examples, distinguish between foliated and non-foliated metamorphic rocks. Answer: Foliated: show layering or banding of different minerals created by the alignment of minerals during directional stress and recrystallization (Ex: schist, gneiss). Non foliated: a mass or network of interlocking crystals consisting of one mineral with no visible layering or banding (Ex: marble, quartzite).

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Summary... Overview of Points covered:  Two Metamorphic Textures: 1)Foliated 2)Non-Foliated  Metamorphism Depends on: 1)Alignment of minerals 2)Recrystallization of minerals  Parent – Metamorphic rock pairs: Limestone – Marble Sandstone – Quartzite Shale – Slate (Phyllite – Schist – Gneiss) Granite – Gneiss