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When plotted in multi-isotope space, ocean island basalts tend to form arrays trending from a central composition out to an endmember with an extreme composition. The depleted mantle, or DM, is one endmember, and is defined by low 87 Sr/ 86 Sr, 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, 208 Pb/ 204 Pb, and high 143 Nd/ 144 Nd and 176 Hf/ 177 Hf.
Blueschist on Île de Groix, France Photomicrograph of a thin section of blueschist facies metamorphosed basalt, from Sivrihisar, Turkey. Blueschist (/ ˈ b l uː ʃ ɪ s t /), also called glaucophane schist, is a metavolcanic rock [1] that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures (200–500 °C (392–932 °F ...
Plutonism is the geologic theory that the igneous rocks forming the Earth originated from intrusive magmatic activity, with a continuing gradual process of weathering and erosion wearing away rocks, which were then deposited on the sea bed, re-formed into layers of sedimentary rock by heat and pressure, and raised again.
Flood basalts on Vancouver Island form a geologic formation called the Karmutsen Formation, which is perhaps the thickest accreted section of an oceanic plateau worldwide, exposing up to 6,000 m (20,000 ft) of basal sediment-sill complexes, basaltic to picritic pillow lavas, pillow breccia, and thick, massive basalt flows.
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
The island Lítla Dímun in the Faroes. The Faroe Islands lie on the Eurasian Plate between Scotland, Norway and Iceland. The islands are of volcanic origin and are made up of three layers of basalt, with the top and bottom layers resembling each other. The age of this rock is between 54 and 58 million years, with the oldest material at the ...
The crystallized magma forms a new crust of basalt known as MORB for mid-ocean ridge basalt, and gabbro below it in the lower oceanic crust. [16] Mid-ocean ridge basalt is a tholeiitic basalt and is low in incompatible elements. [17] [18] Hydrothermal vents fueled by magmatic and volcanic heat are a common feature at oceanic spreading centers.
Isostatic rebound would adjust the depth of the craters making them relatively shallow in comparison to their diameter; [10] some reaching 4 km deep and 1000 km in diameter. [8] Topographic division between the low-lying impact basins and the now elevated surface. [9] Release in pressure at the surface from the removal of overburden. This ...