Search results
Results from the WOW.Com Content Network
There is also a change in the structure and relationship of greenstone belts to their basements between the Archaean where there is little clear relationship, if any, between basalt-peridotite sheets of a greenstone belt and the granites they abut, and the Proterozoic where greenstone belts sit upon granite-gneiss basements and / or other ...
A large number of geological and geochemical methods have been applied to the rocks of the Isua Greenstone Belt. These include subdivision of the various lithologies and units within the belt using a combination of geological mapping and U-Pb zircon dating, typically using sensitive high-resolution ion microprobe (SHRIMP), analyses; [3] major and trace element chemistry; [11] [12] structural ...
Shields can be very complex: they consist of vast areas of granitic or granodioritic gneisses, usually of tonalitic composition, and they also contain belts of sedimentary rocks, often surrounded by low-grade volcano-sedimentary sequences, or greenstone belts. These rocks are frequently metamorphosed greenschist, amphibolite, and granulite facies.
The rock exposed in the oldest regions of shields, which is of Archean age (over 2500 million years old), mostly belong to granite-greenstone belts. The greenstone belts contain metavolcanic and metasedimentary rock that has undergone a relatively mild grade of metamorphism, at temperatures of 350–500 °C (662–932 °F) and pressures of 200 ...
Hope Bay greenstone belt (Nunavut) Hunt River greenstone belt (Newfoundland and Labrador) Nuvvuagittuq Greenstone Belt (Quebec) Red Lake greenstone belt (Ontario) Rice Lake greenstone belt (Manitoba) Swayze greenstone belt (Ontario) Temagami Greenstone Belt (Ontario) Yellowknife greenstone belt (Northwest Territories)
The geology of Greenland is dominated by crystalline rocks of the Precambrian Shield. [1] The crystalline rocks of the Nuuk/Qeqertarsuatsiaat area comprise some of the oldest bedrock in Greenland which covers most of western Greenland. The surface has been altered several times and has an appearance as though it were shaped billions of years ago.
Greenstone (archaeology), various types of stone used by early cultures, covering jade and similar stones Greenstone belt , Archean and Proterozoic volcanic–sedimentary rock sequences Isle Royale greenstone Chlorastrolite, found in the Keweenaw Peninsula of Michigan and Isle Royale in the US
For example, a weakly metamorphosed basalt would be described as a metabasalt, or a weakly metamorphosed tuff as a metatuff. [ 3 ] Metavolcanic rock is commonly found in greenstone belts .