What is Buchan metamorphism?
Buchan metamorphic zones Areas in which a series of mineral assemblages occur, with a biotite zone surrounded by zones of cordierite, andalusite, and sillimanite, in increasing order of metamorphic grade. The zones are named after the region of north-east Scotland (north of Aberdeen) in which they occur.
What is correct sequence of Buchan zone of metamorphism?
Barrovian zones are especially easy to recognize in pelitic rocks. The prograde sequence of Barrovian zones is: chlorite – biotite – garnet – staurolite – kyanite – sillimanite.
What are the 4 metamorphic rocks?
Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite.
When rocks are metamorphosed the mineral components of the rock are generally?
The principal agents of metamorphism are: temperature, pressure and fluids. When rocks are metamorphosed, the mineral components of the rock are: changed in the solid state.
How many zones are identified in Buchan series?
In pelitic rocks, Barrow recognized 6 zones of distinctive mineral assemblages, which he recognized as representing increasing grade of metamorphism. The boundaries for his zones were based on the first appearance of a particular mineral, called an index mineral, which is characteristic of the zone.
What type of rock is obsidian?
Rondi: Everyone, meet Obsidian , an igneous rock that from melted rock, or magma. Obsidian is an “extrusive” rock, which means it is made from magma that erupted out of a volcano. If it was an igneous rock that formed from magma underground and did not erupt, it would have been called an “intrusive” rock.
Is gneiss a metamorphic rock?
gneiss, metamorphic rock that has a distinct banding, which is apparent in hand specimen or on a microscopic scale. Gneiss usually is distinguished from schist by its foliation and schistosity; gneiss displays a well-developed foliation and a poorly developed schistosity and cleavage.
Is sillimanite metamorphic?
Sillimanite is a metamorphic mineral found in high grade aluminous schists and gneisses. It is a polymorph of andalusite and kyanite, all having formula Al2SiO5.
What type of metamorphism produces sillimanite?
7.5.2.3 Disten or sillimanite, cordierite, and staurolite schists. Disten or sillimanite, cordierite, and staurolite schists occur in conditions of high-degree metamorphism from pelite sediment, that is, shale, mudstone, and marl.
What kind of metamorphic rocks are Buchan facies?
The Buchan Facies Series of regional metamorphism is characterized by the presence of andalusite, and sometimes cordierite, in intermediate grade mineral assemblages indicating that the conditions of metamorphism were at lower pressure and along a higher metamorphic field gradient than that recorded in Barrovian Facies Series metamorphic rocks .
Where does Buchan metamorphism occur in an extensional setting?
Buchan metamorphism occurs often in extensional settings, for example at rift basins. In contact metamorphism (metamorphism caused by high temperatures at low pressure in the vicinity of an igneous intrusion) a local contact aureole of zones is formed around a heat source.
Is the Buchan facies series related to plate tectonics?
However, Buchan facies series plot along line 3 and Barrovian at somewhat higher pressure and with the appearance of kyanite. The facies series have connections to plate tectonics. Facies series 1 is typical of contact metamorphism, but also found in regional metamorphosed rocks.
Who is the founder of the metamorphic series?
Metamorphic series include the Barrovian and Buchan series of metamorphic rocks. George Barrow was a geologist in Scotland who discovered the Barrovian series.. These are also called metamorphic facies series.