9 metamorphicrocks

47 134 0
9 metamorphicrocks

Đang tải... (xem toàn văn)

Tài liệu hạn chế xem trước, để xem đầy đủ mời bạn chọn Tải xuống

Thông tin tài liệu

Metamorphism • The transformation of rock by temperature and pressure • Metamorphic rocks are produced by transformation of: • Igneous, sedimentary and igneous rxs Thanks to CU Boulder Geology Dept for use of some of these slides Metamorphism • Metamorphism progresses from low to high grades • Rocks remain solid during metamorphism W hat causes metamorphism? • Heat • Most important agent • Heat drives recrystallization - creates new, stable minerals • Pressure (stress) • Increases with depth • Pressure can be applied equally in all directions or differentially Origin of pressure in metamorphism Confining or hydrostatic pressure: equal in all directions Directed pressure: largely in one direction or along a particular axis Main factor affecting metamorphism • Parent rock • Metamorphic rocks typically have the same chemical composition as the rock they were formed from • Different minerals, but made of the same stuff • Exception: gases (carbon dioxide, CO2) and water (H2O) may be released Progressive metamorphism of a shale Shale Progressive metamorphism of a shale Slate Progressive metamorphism of a shale Phyllite Progressive metamorphism of a shale Schist Example of slate Slate roof Common metamorphic rocks • Foliated rocks • Phyllite – Grade of metamorphism between slate and schist – Made of small platy minerals – Glossy sheen with rock cleavage – Composed mainly of muscovite and/or chlorite Phy llite (left) and Slate (right) lack v isible mineral grains Common metamorphic rocks • Foliated rocks • Schist – Medium- to coarse-grained – Comprised of platy minerals (micas) – The term schist describes the texture – To indicate composition, mineral names are used (such as mica schist) Mica Schist - note well developed foliation A mica garnet schist Common metamorphic rocks • Foliated rocks • Gneiss – Medium- to coarse-grained – Banded appearance – High-grade metamorphism – Composed of light-colored feldspar layers with bands of dark mafic minerals Gneiss display s bands of light and dark minerals Diorite to Gneiss Morph (orthogneiss - from igneous protolith) W hat are metamorphic textures? • Texture refers to the size, shape, and arrangement of mineral grains within a rock • Foliation – planar arrangement of mineral grains within a rock Outcrop of foliated gneiss Metamorphic textures • Foliation • Foliation can form in various ways: – Rotation of platy or elongated minerals – Recrystallization of minerals in a preferred orientation – Changing the shape of equidimensional grains into elongated and aligned shapes Flattened Pebble Conglomerate = flattening Dev elopment of foliation due to directed pressure

Ngày đăng: 30/11/2016, 16:34

Mục lục

  • Metamorphism

  • Slide 2

  • Slide 3

  • Slide 4

  • Slide 5

  • Main factor affecting metamorphism

  • Slide 7

  • Slide 8

  • Slide 9

  • Slide 10

  • Slide 11

  • Slide 12

  • Contact metamorphism

  • Slide 14

  • Slide 15

  • Metamorphism and plate tectonics

  • Slide 17

  • Slide 18

  • Metamorphic Environments

  • Slide 20

  • Slide 21

  • Slide 22

  • Slide 23

  • Slide 24

  • Slide 25

  • Common metamorphic rocks

  • Slide 27

  • Slide 28

  • Slide 29

  • Slide 30

  • Slide 31

  • Slide 32

  • Slide 33

  • Slide 34

  • Slide 35

  • Phyllite (left) and Slate (right) lack visible mineral grains

  • Slide 37

  • Slide 38

  • A mica garnet schist

  • Slide 40

  • Gneiss displays bands of light and dark minerals

  • Slide 42

  • What are metamorphic textures?

  • Slide 44

  • Metamorphic textures

  • Slide 46

  • Development of foliation due to directed pressure

Tài liệu cùng người dùng

  • Đang cập nhật ...

Tài liệu liên quan