Monzogranite

Monzogranite
Igneous rock
Monzogranite (Col des Croix, Haute-Saône, France)
QAPF diagram with the Monzogranite field highlighted

Monzogranite is a plutonic rock that occupies the middle of the QAPF diagram, consisting of between 20-60% quartz, and of the remainder, between 35-65% alkali feldspar and the remainder plagioclase.

Examples

Wave Rock, an outcrop of monzogranite in Western Australia

Pilgangoora belt, Pilbara craton, Western Australia

Monzogranite is associated with the Pilbara craton, a terrane that collided with Western Australia approximately 3.315 Ga, forming a greenstone belt. These monzogranites are typically highly fractionated, rich in potassium, poor in aluminum, and have trace element compositions consistent with remelting of an older tonalitic–trondhjemitic–granodioritic crust.

Carlindi monzogranites in the same greenstone belt are light greyish-pink coloured, with roughly equal parts plagioclase, quartz, and microcline, and small amounts of muscovite and mafic minerals. The texture of these monzogranites is similar to granodiorite.[1]

Quebec's near north

In Quebec's near north, early monzogranites are moderately to strongly fractionated, rich in lanthanum, zirconium, but low in ytterbium and yttrium. In general, these monzogranites are low in rare-earth elements.[2]

Vigo–Regua shear zone, northern Portugal

In northern Portugal, along the Vigo–Régua shear zone, the monzogranites belong to the syn-F3 biotite granitoid group. They include large crystals of potassium feldspar and have enclaves of mafic microgranules. The monzogranites are largely composed of quartz, potassium feldspar, plagioclase, and biotite; with small amounts of zircon, monazite, apatite, ilmenite, and muscovite.[3]

Gabal El-Urf area, eastern Egypt

Granitoids in the Gabal El-Urf area in eastern Egypt consist of a monzogranite pluton, belonging to the Younger Granite province, emplaced in granodioritic rocks. The monzogranites here are depleted in aluminum, magnesium, calcium, and titanium, while being enriched with rubidium, niobium, zirconium, and yttrium. They are similar to other granites that were emplaced by crustal extension, and are chemically consistent with fractional crystallization. The monozogranite is moderately radioactive, with much of the uranium and thorium incorporated into accessory minerals such as zircon, xenotime, and allanite.[4] The source of the monzogranite was likely partial melting in the Neoproterozoic, caused by either an orogeny, or magma from a volcanic arc.[5]

Southern Variscan belt in southern Europe

In the southern Variscan belt, Iberia, the Beiras massif Tamanhos, Maceira and Casal Vasco, of Southern Europe, biotite monzogranites are low in aluminum and sodium, while being high in titanium and calcium. The chemistry of these monzogranites could arise from melting of greywacke or tonalite, or could also result from mixing of basalt magma with crustal melts that are higher in aluminum.[6]

See also

References

  1. ^ Green, Michael Godfrey (2001). Early Archaean Crustal Evolution: Evidence from ~3.5 Billion Year Old Greenstone Successions in the Pilgangoora Belt, Pilbara Craton, Australia (PDF) (Thesis). School of Geosciences, Division of Geology and Geophysics, University of Sydney.
  2. ^ Boiley, Miche; Gosselin, Charles (2003). "Rare metal potential in the Near North, Québec". Geoscience Exhibit. Archived from the original on 25 August 2004.
  3. ^ Simoes, Pedro Pimenta (2000). Emplacement, geochronology and petrogenesis of the syntectonic biotite-granitoids associated with the Vigo-Régua shear zone (Hercynian Central Iberian Zone, Northern Portugal) (Thesis). University of Minho and University of Nancy (France).
  4. ^ El Mezayen, AM; Ali, HH; Abu, Bakr MA; Sherif, HMY; El Nahas, HA (2016). "Geology and Radioactivity of the Basement Rocks of Wadi El-Sahu Area, Southwestern Sinai, Egypt". Greener Journal of Geology and Earth Sciences. 4: 001–022. doi:10.15580/GJGES.2016.1.021716041.
  5. ^ Moghazi, Abdel-Kader M (1999). "Magma source and evolution of Late Neoproterozoic granitoids in the Gabal El-Urf area, Eastern Desert, Egypt: geochemical and Sr–Nd isotopic constraints". Geological Magazine. 136 (3): 285–300. Bibcode:1999GeoM..136..285M. doi:10.1017/S0016756899002563.
  6. ^ Aguado, Beatriz Valle; Azevedo, M. Rosário; Nolan, John; Martins, M. Estela (2005). "Origin and emplacement of syn-orogenic Variscan granitoids in Iberia the Beiras massif". Journal of the Virtual Explorer. 19. Archived from the original on 31 March 2018.