What type of metamorphic rock is Granoblastic?
Granoblastic is an adjective describing an anhedral phaneritic equi-granular metamorphic rock texture. Granoblastic texture is typical of quartzite, marble, charnockites and other non-foliated metamorphic rocks without porphyroblasts.
What are the texture of metamorphic rocks?
TEXTURES Textures of metamorphic rocks fall into two broad groups, FOLIATED and NON-FOLIATED. Foliation is produced in a rock by the parallel alignment of platy minerals (e.g., muscovite, biotite, chlorite), needle-like minerals (e.g., hornblende), or tabular minerals (e.g., feldspars).
What is an example of a metamorphic rock with a foliated texture?
Slate is a fine-grained metamorphic rock that exhibits a foliation called slaty cleavage that is the flat orientation of the small platy crystals of mica and chlorite forming perpendicular to the direction of stress.
What does Granoblastic texture mean?
of a rock. : having a texture in which the fragments are irregular and angular and appear like a mosaic under the microscope.
Why do metamorphic rocks often have a Granoblastic texture?
Granoblastic texture is the typical equigranular texture formed in metamorphic rocks when grains mutually adjust their boundaries in the solid state in an attempt to achieve textural equilibrium.
What are the five basic textures of metamorphic rocks?
The five basic metamorphic textures with typical rock types are:
- Slaty: slate and phyllite; the foliation is called ‘slaty cleavage’
- Schistose: schist; the foliation is called ‘schistocity’
- Gneissose: gneiss; the foliation is called ‘gneisocity’
- Granoblastic: granulite, some marbles and quartzite.
What are the textures of metamorphic rocks quizlet?
The two major types of texture in metamorphic rocks are foliated rocks, which indicate an alignment of platy minerals; and nonfoliated (granular) rocks, which have no preferred alignment of minerals (may indicate a lack of platy minerals).
What is Aphanitic texture?
Aphanitic – This texture describes very fine grained rock where individual crystals can be seen only with the aid of a microscope, i.e. the rock is mostly groundmass. An aphanitic texture is developed when magma is erupted at the Earth’s surface and cools too quickly for large crystals to grow.
How is Granoblastic texture formed?
Granoblastic texture is the typical equigranular texture formed in metamorphic rocks when grains mutually adjust their boundaries in the solid state in an attempt to achieve textural equilibrium. A rock that has a granoblastic texture can be termed a granofels.
How is Granulite formed?
Formation. Granulites form at crustal depths, typically during regional metamorphism at high thermal gradients of greater than 30 °C/km. In continental crustal rocks, biotite may break down at high temperatures to form orthopyroxene + potassium feldspar + water, producing a granulite.
What metamorphic looks like?
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.
How is granoblastic texture formed in metamorphic rocks?
Granoblastic texture is the typical equigranular texture formed in metamorphic rocks when grains mutually adjust their boundaries in the solid state in an attempt to achieve textural equilibrium.
What are the characteristics of a granoblastic grain?
Characteristics defining granoblastic texture include: grains visible to the unaided eye, sutured boundaries and approximately equidimensional grains. The grain boundaries intersect at 120° triple junctions under ideal conditions.
What are the different types of granoblastic crystals?
2- Granoblastic interlobate: where the grain boundaries are somewhat irregular. 3- Granoblastic amoeboid: where all the grains have irregular outlines, and all the minerals are anhedral. 4- Granoblastic decussate: where the interlocking randomly oriented crystals are somewhat elongate, prismatic or subidioblastic.
What kind of texture is a granoblastic interlobate?
2 Granoblastic interlobate: where the grain boundaries are somewhat irregular. 3 Granoblastic amoeboid: where all the grains have irregular outlines, and all the minerals are anhedral.