Download TEXTURES IN IGNEOUS ROCKS (see Kennett and Ross p

TEXTURES IN IGNEOUS ROCKS (see Kennett and Ross p.17)
A
B
C
D
E
F
G
H
I
J
K
Match these textures with the appropriate interpretation
Glassy texture
Coarse grain size
Medium grain size
Fine grain size
Euhedral crystal shape
Subhedral crystal shape
Anhedral crystal shape
Zoned crystal
Corona structure
Ophitic structure
Porphyritic structure
Phenocrysts crystallised slowly at depth then the magma rose to a higher level
and the rest crystallised quickly to form a fine-grained matrix
Crystals had plenty of time to grow around a limited number of nucleii
Reaction took place between crystal and liquid in a continuous solid solution
series and there was not time for the whole of the crystal to react with the melt
The crystals were the first to form and their growth was not restricted
The crystals formed around many nucleii
The feldspars started to crystallise first around widely separated nucleii before
they were joined by pyroxene which crystallised slowly forming large plates
The crystal reacted with the melt and there was not time for the whole of the
crystal to react with the melt. This occurs in minerals forming a discontinuous
reaction series
Crystals formed fairly quickly around a number of nucleii. Usually typical of
minor intrusions
The crystals show no regular crystal form because they were the last to form,
filling in gaps
The magma was supercooled and cooling was too rapid for crystallisation
The crystals formed at a time between the early and the late stages of
crystallisation so the grains have imperfect crystal form
CLASSIFICATION OF IGNEOUS ROCKS
Complete this table
Grain size
Fine or glassy
Medium
Coarse
Ultrabasic
Gabbro
Basic
Intermediate
Andesite
Acid
Rhyolite/
obsidian