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 ?
Geology Type granite-gneiss and retrograde granulite gneiss with minor amounts of granite and granodiorite.
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.
The soils are formed from charnokite and granite-gneiss rocks.
80 m, underlain by hard partially weathered granite-gneiss.
The formation of Ultisols on granite-gneiss under humid tropical weathering conditions appears to be a common occurrence in Indian subcontinent as evidenced in the present study and elsewhere (Bhattacharyya et al.
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).
The inlet is fed by a relatively small (10 km2) drainage basin where dwarf birch was found and which seemed to be representative of low arctic terrain in the granite-gneiss bedrock area.
2) Low shrub heath in areas of granite-gneiss bedrock, with Salix arctica, Cassiope tetragona, Betula glandulosa, Vaccinium vitis-ideae, Ledum palustre, and other heath plants, and numerous herbs, grasses, and mosses;
A number of important shears have been recognised along meta-sedimentary / granite-gneiss contacts, as well as inflections on major shears which may be important in localising mineralization.