Granophyre is a subvolcanic rock

Subvolcanic rock

A subvolcanic rock, also known as a hypabyssal rock, is an igneous rock that originates at medium to shallow depths within the crust and contain intermediate grain size and often porphyritic texture. They have textures between volcanic and plutonic rocks. Subvolcanic rocks include diabase and...

 that contains quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 and alkali feldspar

Feldspar

Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....

 in characteristic angular intergrowths such as those in the accompanying image.

The texture

Texture (crystalline)

In materials science, texture is the distribution of crystallographic orientations of a polycrystalline sample. A sample in which these orientations are fully random is said to have no texture. If the crystallographic orientations are not random, but have some preferred orientation, then the...

 is called granophyric. The texture can be similar to micrographic texture

Micrographic texture

In petrology, micrographic texture is a fine-grained intergrowth of quartz and alkali feldspar, interpreted as the last product of crystallization in some igneous rocks which contain high or moderately high percentages of silica...

 and to the coarser graphic intergrowths of quartz and alkali feldspar common in pegmatite

Pegmatite

A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....

. These textures document simultaneous crystallization of quartz and feldspar from a silicate melt at the eutectic point, perhaps in the presence of a water-rich phase.

Granophyres typically are intrusive rocks that crystallized at shallow depths, and many have compositions similar to those of granite

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

s. A common occurrence of granophyre is within layered igneous intrusions dominated by rocks with compositions like that of gabbro

Gabbro

Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....

. In such occurrences, the granophyre may form as an end product of fractional crystallization

Fractional crystallization (geology)

Fractional crystallization is one of the most important geochemical and physical processes operating within the Earth's crust and mantle. Fractional crystallization is the removal and segregation from a melt of mineral precipitates; except in special cases, removal of the crystals changes the...

 of a parent mafic magma

Magma

Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

, or by melting of rocks into which the mafic magma was emplaced, or by a combination of the two processes.

Granophyre may have formed as the upper most stratigraphic layer resulting from melting of bed rock by a meteorite

Meteorite

A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

 impact. For example, The Sudbury bolide impacted the Sudbury Basin

Sudbury Basin

The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geologic structure in Ontario, Canada. It is the second-largest known impact crater or astrobleme on Earth, as well as one of the oldest....

 1.8 Gya forming a layer of melted rocks known as the Sudbury impact bubble, with the top most layer being granophyre.

See also

• Micrographic texture
  Micrographic texture
  In petrology, micrographic texture is a fine-grained intergrowth of quartz and alkali feldspar, interpreted as the last product of crystallization in some igneous rocks which contain high or moderately high percentages of silica...
  
  
• Rock microstructure
  Rock microstructure
  Rock microstructure includes the texture of a rock and the small scale rock structures. The words "texture" and "microstructure" are interchangeable, with the latter preferred in modern geological literature...
  
  
• Granite
  Granite
  Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
  
  
• Eutectic
• Solidus
  Solidus (chemistry)
  In chemistry, materials science, and physics, the solidus is the locus of temperatures below which a given substance is completely solid...