A2 Metamorphic Processes Flashcards
Relict structures
such as bedding, present in the parent rock, which is partially preserved in a metamorphic rock.
Dalradian
a regionally metamorphosed group of rocks originally deposited in the late 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 recrystallised 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 an index mineral occurs.
Metamorphic zone
the name given to an area between two isograds. The zone is named after the lower grade isograd. All locations within a metamorphic zone experienced the same metamorphic grade.
Barrovian zones
are metamorphic zones mapped using index minerals identified by George Barrow.
Prograde metamorphism
is the recrystallisation of a rock in response to an increase in the intensity of metamorphism.
5 index minerals low grade to high grade
Chlorite, Biotite, Garnet, Kyanite, Sillimanite
Crenulation Cleavage
Pre-kinematic metamorphic minerals
Syn-kinematic metamorphic minerals
Post-kinematic metamorphic minerals
