Table of Contents
What two things determine the texture of a metamorphic rock?
Classification of Metamorphic Rocks. As with igneous and sedimentary rocks, metamorphic rocks are classified on the basis of texture (grain size, shape, orientation) and mineral composition.
What determines texture of a rock?
The texture of a rock is the size, shape, and arrangement of the grains (for sedimentary rocks) or crystals (for igneous and metamorphic rocks). Also of importance are the rock’s extent of homogeneity (i.e., uniformity of composition throughout) and the degree of isotropy.
What causes the metamorphic texture?
Metamorphic textures Foliation is caused by the re-alignment of minerals when they are subjected to high pressure and temperature. Individual minerals align themselves perpendicular to the stress field such that their long axes are in the direction of these planes (which may look like the cleavage planes of minerals).
Does the texture of a metamorphic rock change what about the composition?
Metamorphism is the alteration of a preexisting rock (the parent rock) due to heat and pressure caused by burial in the earth. The parent rock must adapt to the new conditions and it does so by changing mineral composition and texture. These rocks with new texture and composition are metamorphic rocks.
What is the texture of a metamorphic rock?
The banded, foliated texture is referred to as GNEISSOSE. The corresponding rock type is GNEISS. Gneiss is normally phaneritic, but in some cases the layers are aphanitic….
| Metamorphic Rocks | N O T F O L I A T E D |
|---|---|
| APHANITIC OR PHANERITIC | |
| Fine- to coarse-grained, GRANOBLASTIC texture | |
| ROCK NAME | QUARTZITE |
What are characteristics of metamorphic rocks?
Metamorphic rocks were once igneous or sedimentary rocks, but have been changed (metamorphosed) as a result of intense heat and/or pressure within the Earth’s crust. They are crystalline and often have a “squashed” (foliated or banded) texture.
What is metamorphic rocks texture?
Metamorphic texture is the description of the shape and orientation of mineral grains in a metamorphic rock. Metamorphic rock textures are foliated, non-foliated, or lineated are described below. Metamorphic rock identification table. (
What is the composition of a metamorphic rock?
Metamorphic rocks started out as some other type of rock, but have been substantially changed from their original igneous, sedimentary, or earlier metamorphic form. Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineral-rich fluids or, more commonly, some combination of these factors.
What are characteristics of metamorphic rock?
What makes up the texture of a metamorphic rock?
The term texture refers to the size, shape, and boundary relationships of the minerals, particles, and other substances that make up a rock. There are two major textural groups in metamorphic rocks: Foliated and Non-Foliated. In this texture, the mineral crystals in the rock are aligned with each other.
When does metamorphism occur in the process of mountain building?
Metamorphism (meta = change, morph = form) happens when molten rock intrudes other rocks and bakes the contact zone where the molten rock touches the preexisting rock. Metamorphism also happens when rocks are buried deeply during the process of mountain building.
How are metamorphic rocks used to determine protolith?
As the grade of metamorphism increases, original textures are replaced with metamorphic textures and other clues, such as bulk chemical composition of the rock, are used to determine the protolith. The bulk chemical composition of the rock.
How is the composition of a rock determined?
The mineral composition of the rock can be determined based on observations with a hand lens and if needed, physical or chemical tests. Start by identifying and list all visible minerals present in the rock.