Granite-Gneiss

granite-gneiss

[′gran·ət ¦nīs]
(petrology)
A banded metamorphic rock derived from igneous or sedimentary rocks mineralogically equivalent to granite.

Granite-Gneiss

 

a holocrystalline shale rock consisting, like granite, of quartz, potash feldspar, acid plagioclase, and mica (predominantly biotite).

A majority of researchers believe granite-gneisses to be granites that have crystallized deep in the earth’s crust either during the cooling of the magmatic melt under directed pressure or during the process of the magma’s movement, as a result of which there is parallel arrangement of the mica (more rarely, of the other minerals). It is extremely difficult to distinguish the magmatic granite-gneisses from the meta-morphic gneisses. For this reason, the name granite-gneiss is sometimes used to denote macrocrystalline gneisses that are rich in granitic material.

References in periodicals archive ?
granite-gneiss metamorphic rock, formed by intense heat, has a striped
The black soils of Raichur district are said to have formed from granite-gneiss (Dasog and Hadimani, 1980), but there are no studies confirming this.
Geology Type granite-gneiss and retrograde granulite gneiss with minor amounts of granite and granodiorite.
Figure.1a illustrates the rising trend of L-D curves, which defines the linear behaviour of the rock, this declines as the rock's physical properties change from very hard (norite) to hard (granite-gneiss, dark-grey granite) and medium hard rocks such as MtSorrel and BHP granites.
The L-D curves of the granite-gneiss rock samples showed regular elongated trend-lines with smooth trails and slight path deviations changing between 155kN-0.25mm and 195kN-0.75mm.
The soils are formed from charnokite and granite-gneiss rocks.
Kinalur series (represented by pedon 3) is moderately deep soil with a solum thickness of 0.80 m, underlain by hard partially weathered granite-gneiss. They are developed on 15-20% slopes of mounds and hills.
Large-scale advection of granitic melts into the upper crust is thought to have contributed to the crustal-scale amplitude (10-15 km) of composite granite-gneiss domes, many of which are cored by young granites (Bleeker, 2002).
It is a large central-type intrusion emplaced in pre-existing biotite-plagioclase gneiss and granite-gneiss about 380 million years ago.
The interior and coastal lowlands of southern Baffin Island comprise the Foxe Lowland physiographic province, which is bisected by a major contact between Ordovician sedimentary rocks and Precambrian granite-gneiss, overlain with extensive glacial, glaciofluvial, and marine sediments (Blake, 1966; Blackadar, 1967).
Most of the quartz-feldspar- and granite-gneisses, such as dacites, rhyolites, porphyries, etc., are considered to belong to acid metavolcanites (Niin 1997).