What is eclogite made of?
What is eclogite made of?
Eclogites consist primarily of green pyroxene (omphacite) and red garnet (pyrope), with small amounts of various other stable minerals—e.g., rutile. They are formed when volcanic or metamorphic rocks rich in such mafic minerals are subjected to extremely high pressures and moderate to relatively high temperatures.
What type of rock is glaucophane?
METAMORPHIC ROCKS
METAMORPHIC ROCKS | Facies and Zones Glaucophane is an alkali-amphibole that is dark or blue in hand specimen and colourless to blue under the microscope. Plagioclase is not normally present, but can occur as albite.
What is Blueschist made of?
Abstract. The blueschist metamorphic facies are characterized by the minerals jadeite, glaucophane, epidote, lawsonite, and garnet. They record metamorphism in the cool high-pressure/low-temperature thermal gradients at less than 7°C/km in subduction zones in the last 1 billion years.
How do you identify hornblende in a thin section?
In PPL a thin section of Hornblende ranges from yellow -green to dark brown. Green varieties usually have X= light yellow green, Y=green or grey-green and Z=dark green. Brownish varieties have X=greenish-yelow/brown, Y=yellowish to reddish brown and Z=grey to dark brown.
What type of rock is granodiorite?
Granite and granodiorite are intrusive igneous rocks that slowly cool deep underground in magma chambers called plutons.
What type of rock is the Kirkjugolf made of?
“Kirkjugolf is a 80 m² coastal eroded and shaped columnar basalt outcrop, where the (answer A) of vertical basalt columns can be seen.”
What is glaucophane stone?
Glaucophane is a sodium magnesium iron aluminium silicate hydroxide mineral, found in blueschist facies subduction zones. Glaucophane crystals are named from the Greek ‘to appear blue’, and fine translucent blue crystals are highly collectable.
How is glaucophane formed?
Glaucophane is formed typically in a highly metamorphic zone known by the geologic term blueschist facies. This facies forms from material caught under subduction zones in mountain belt regions. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle.
Is glaucophane hydrated?
Although glaucophane is an index hydrous mineral for the blueschist facies, its stability at mantle depths in diverse subduction regimes of contemporary and early Earth has not been experimentally determined. 40 km depth under warm subduction geotherm or the Proterozoic tectonic setting.
What is glaucophane made of?
Glaucophane occurs in schists formed by high-pressure metamorphism of sodium-rich sediments at low temperatures (up to 400°F/200°C) or by the introduction of sodium into the process. Glaucophane is often accompanied by jadeite, epidote, almandine, and chlorite. It is one of the minerals that are referred to as asbestos.
What is glaucophane metamorphic facies?
Glaucophane and its associated minerals are known as the glaucophane metamorphic facies. The presence of these minerals indicates the range of temperatures and pressures under which metamorphism occurs. Name: From the Greek for bluish green and to appear.
Is there twinning in glaucophane?
There is no twinning in glaucophane. Glaucophane also has a parallel extinction when viewed under cross polars. Lavender blue, blue, dark blue, gray or black.
What type of fold is the metagabbro Dyke?
The granite gneisses and metagabbro dykes form a fold package with a gently plunging hinge and inclined axial surfaces. At the southern end of the cape, the metagabbro dyke (D17) for over 30 m along strike preserves normal crosscutting relations with the host gneisses.
