Key words Flashcards
Isochemical
No elements are added or removed
cataclasis
the brittle fracturing and grinding down of existing rock, usually in fault zones
Metamorphic grade
A measure of the intensity or metamorphism
Country rock
The rock into which an igneous rock has been intruded
Metamorphic aureole
A region surrounding an igneous intrusion in which the country rocks have been recrystallized and been changed by heat from the intrusion
Spotted rock
Formed by low grade metamorphism in the outer part of the metamorphic aureole
Index mineral
Metamorphic minerals, which are stable under specific temperature and pressure conditions. They indicate the metamorphic grade.
Relict structure
e.g. bedding, present in parent rock, which is partially preserved in a metamorphic rock
Dalradian
A regionally metamorphosed group of rocks originally deposited in the Precambrian. They are found in Scotland and Ireland.
Inclusion
The term used to mean an early formed mineral enclosed by one that grew later
Unfoliated
Describes the random orientation of minerals in a metamorphic rock
Hornfels
A fine grained, hard, splintery, granoblastic metamorphic rock formed when shale is completely recrystallized close to the contact with an igneous intrusion
Polymorphs
Minerals that have the same composition but occur in different crystal forms
Isograd
The name given to a line on a map joining points of equal metamorphic grade. They join places where the first appearance of index mineral occurs
Metamorphic zone
The name given to an area between two isograds.
