Monzogranite

Monzogranite

Igneous rock

Monzogranite (Col des Croix, Haute-Saône, France)

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.

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]

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]

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]

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]

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]

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