Granophyre
Granophyre(/ˈɡrænəfaɪər/GRAN-ə-fire;[1][2]fromgraniteandporphyry) is asubvolcanic rockthat containsquartzand alkalifeldsparin characteristic angular intergrowths such as those in the accompanying image.
Thetextureis calledgranophyric.The texture can be similar tomicrographic textureand to the coarser graphic intergrowths of quartz and alkali feldspar common inpegmatite.These textures document simultaneous crystallization of quartz and feldspar from a silicate melt at theeutecticpoint, perhaps in the presence of a water-rich phase. They may also be formed by crystallization when the magma is significantlyundercooled,not necessarily under eutectic conditions.[3]
Granophyres typically are intrusive rocks that crystallized at shallow depths, and many have compositions similar to those ofgranites.[4]A common occurrence of granophyre is within layered igneous intrusions dominated by rocks with compositions like that ofgabbro.In such occurrences, the granophyre may form as an end product offractional crystallizationof a parent maficmagma,or by melting of rocks into which the mafic magma was emplaced, or by a combination of the two processes.
Granophyre may also form as the uppermost stratigraphic layer resulting from melting of upper-middle crustal rocks by ameteoriteimpact. For example, the upper layer of the Main Mass of the 1850 MaSudbury Structureis composed of fine-medium grained granitic rocks with abundant granophyric textures.
See also
[edit]- Micrographic texture
- Rock microstructure– size, shape and mutual relations of the particles of a rock
- Granite– Type of igneous rock
- Eutectic– Mixture with a lower melting point than its constituents
- Solidus
References
[edit]- ^"Granophyre".LexicoUK English Dictionary.Oxford University Press.Archived fromthe originalon 2020-03-22.
- ^"Granophyre".Merriam-Webster Dictionary.Merriam-Webster.
- ^Lowenstern, J.B.; Clynne M.A.; Bullen T.D. (1997)."Comagmatic A-Type Granophyre and Rhyolite from the Alid Volcanic Center, Eritrea, Northeast Africa".Journal of Petrology.38(12). Oxford University Press: 1707–1721.doi:10.1093/petroj/38.12.1707.
- ^McDonnell, S.; Troll, V. R.; Emeleus, C. H.; Meighan, I. G.; Brock, D.; Gould, R. J. (October 2004)."Intrusive history of the Slieve Gullion ring dyke, Ireland: implications for the internal structure of silicic sub-caldera magma chambers".Mineralogical Magazine.68(5): 725–738.doi:10.1180/0026461046850215.ISSN0026-461X.
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