Monzogranites are biotite

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

rocks that are considered to be the final

fractionation Fractionation is a separation process in which a certain quantity of a mixture (of gases, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities (fractions) in which the ...

product of

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

. Monzogranites are characteristically felsic (SiO₂ > 73%, and FeO + MgO + TiO₂ < 2.4), weakly

peraluminous Peraluminous rocks are igneous rocks that have a molecular proportion of aluminium oxide higher than the combination of sodium oxide, potassium oxide and calcium oxide.Blatt, Harvey and Robert J. Tracy, ''Petrology,'' Freeman, 2nd ed., 1995, p. ...

(Al₂O₃/ (CaO + Na₂O + K₂O) = 0.98–1.11), and contain

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

sphene Titanite, or sphene (from the Greek ''sphenos'' (σφηνώ), meaning wedge), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals in ...

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...

and

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...

as accessory

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

s. Although the compositional range of the monzogranites is small, it defines a differentiation trend that is essentially controlled by biotite and

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...

. (Fagiono, 2002). Monzogranites can be divided into two groups (magnesio-potassic monzogranite and ferro-potassic monzogranite) and are further categorized into rock types based on their macroscopic characteristics, melt characteristics, specific features, available isotopic data, and the locality in which they are found.

Monzogranite rock types

MGr type I: Muscovite-biotite-metagranite. Small and equal grained, greyish-brown, yellow altered K-fsp (Saladillo, S. Chepes). MGr type II: Muscovite-metagranite. Medium grained, porphyric, pink K-fsp, with "schollen", whitish-pink (with "Schollen"). MGr type III: Schollen-metagranite. Medium and equal grained, large and many "schollen", whitish-grey, only biotite (Tuaní, S. Chepes and S. Ulapes south). MGr type IV: Biotite-metagranite. Medium to large, porphyric or equal grained pink K-fsp, reddish quartz (Chimenea, S. Chepes). MGr type V: Metagranite. Medium and equal grained reddish K-fsp whitish (El Abra, S. Ulapes). MGr type V aplite: Metagranite, aplite dikes and layers. Pink small and equal grained, whitish K-fdsp, grey quartz, pink-white (S. Ulapes north).

Examples

Pilgangoora belt, Pilbara craton

Pilbara The Pilbara () is a large, dry, thinly populated region in the north of Western Australia. It is known for its Aboriginal peoples; its ancient landscapes; the red earth; and its vast mineral deposits, in particular iron ore. It is also a g ...

Granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

– Greenstone

Terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust (geology), crust fragment formed on a tectonic plate (or broken off from it) and Accretion (geology), accreted or "Suture (geology), sutured" to crust lying on another pla ...

c. 3.315 Ga monzogranites are typically highly

fractionated Fractionation is a separation process in which a certain quantity of a mixture (of gases, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities ( fractions) in which t ...

, K rich, Al poor, and have trace element compositions consistent with remelting of an older tonalitic– trondhjemitic– granodioritic (TTG) crust. Carlindi monzogranites in the greenstone belt are light greyish-pink coloured, "massive,

coarse-grained Granularity (also called graininess), the condition of existing in granules or grains, refers to the extent to which a material or system is composed of distinguishable pieces. It can either refer to the extent to which a larger entity is sub ...

(<5 cm),

holocrystalline Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion ...

and composed of

(30–40%),

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

(30–40%),

microcline Microcline (KAlSi3O8) is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slo ...

(25–30%),

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...

s (<5%), and

muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate mineral of aluminium and potassium with formula K Al2(Al Si3 O10)( F,O H)2, or ( KF)2( Al2O3)3( SiO2)6( H2O). It has a highly perfect basal cleavag ...

(<5%). In general, the

texture Texture may refer to: Science and technology * Surface texture, the texture means smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface characteristics with waves shorter than road roughness * Texture ...

is similar to

granodiorite Granodiorite () is a coarse-grained ( phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from gr ...

s, with zoned subhedral plagioclase, and anhedral microcline and quartz. However, microcline is commonly

poikilitic Poikilitic texture refers to igneous rocks where large later-formed less perfect crystals ('oikocrysts') surround smaller early-formed idiomorphic crystals ('chadacrysts') of other minerals. A poikilitic texture is most easily observed in petrog ...

, with abundant fine-grained plagioclase and quartz. Monzogranites contain medium-grained subhedral muscovite and sometimes trace amounts of embayed,

corrode Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engin ...

d fine-grained

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...

." (Green, 2001).

Quebec's near north

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...

's near north, early monzogranites are moderately fractionated ( Rb/ Sr = 0.15–3.9) and show moderate to high La/ YbCN (14–106) and Zr/ Y (4-52) ratios. On a Rb vs Sr diagram, these rocks plot at the edge of the "fertile" granite field, although rare metal contents are low ( Li = 6–55 ppm, Be = 1–3 ppm and Ta = 0.1–0.5). However, late granites and pegmatitic granites are more fractionated (Rb/Sr = 0–48) and fertile. They show variable but commonly high Li (2–157 ppm), Be (1–6 ppm) and Ta (0.1–5.8 ppm) contents. These granites exhibit strong Eu anomalies, low REE contents and low to moderate a/YbN (0.2–45) ratios. (Boiley and Gosselin, 2003)

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 present a porphyritic texture (potassium feldspar megacrysts) and mafic microgranular enclaves that decrease in frequency from south to north. The granites are composed of quartz + potassium feldspar + plagioclase (andesine/oligoclase) + biotite + zircon + monazite + apatite + ilmenite ± muscovite. The studied granodiorites-monzogranites are moderately peraluminous, A/KNC)m:1.19–1.39 with SiO₂ contents between 62 and 70%. (Simoes, 2000).

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 (72–77% SiO₂) are metaluminous to mildly peraluminous, highly fractionated and depleted in Al₂O₃, MgO, CaO, TiO₂, Sr and Ba with corresponding enrichment in Rb, Nb, Zr, and Y. They can be correlated with the undeformed post-orogenic granites in the Arabian–Nubian Shield that chemically resemble A-type granites emplaced in extensional settings. The mineralogical and chemical variations within the granodiorites and monzogranites are consistent with their evolution by fractional crystallization. The granodiorites have a low initial ⁸⁷Sr/⁸⁶Sr ratio (0.7024) and high et membershipd values (+6.9–+7.3) and are significantly different from those (initial ⁸⁷Sr/⁸⁶Sr ratio=0.7029, et membershipd values=+5.2–+5.8) of the monzogranites. These data suggest a predominant mantle derivation for both granite types and demonstrate that they originated from different source materials. In the Wadi El-Sahu Area, Southwestern Sinai, the radioactivity of the studied gneisses is very low, but the younger granites are moderately radioactive. The monzogranite is relatively higher on radioactivity than the syenogranite. Both of them are characterized by variable eTh/eU ratios and disequilibrium state referring to mobility of uranium. The radioelements of these granites are incorporated in their accessory minerals such as zircon, xenotime and allanite.http://doi.org/10.15580/ The granodiorite melt was most probably generated through vapour-saturated partial melting of an early Neoproterozoic depleted mafic lower-crust reservoir due to crustal thickening associated with orogenic compression and/or arc magma underplating. The mineralogical and geochemical data of the A-type monzogranites are consistent with their derivation as a residual granitic liquid from a LILE-enriched mafic magma through crystal-liquid fractionation of plagioclase, amphibole, Fe–Ti oxides and apatite. The parental mafic magma was originated in the

upper mantle The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust (at about under the oceans and about under the continents) and ends at the top of the lower mantle at . Temperatures range from appr ...

due to crustal thinning associated with extension in the late stage of the Neoproterozoic crustal evolution of north-eastern Egypt." (Moghazi, 1999).

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 "vary from slightly peraluminous granodiorites to highly peraluminous monzogranites (SiO₂ = 60–72%; A/CNK = 1.0–1.37) and are characterized by low Al₂O₃/TiO₂ and high CaO/Na₂O ratios. CaO/Na₂O ratio in peraluminous melts is predominantly controlled by the plagioclase/clay ratio of the source being therefore unlikely that granite melts with high CaO/Na₂O ratios could be produced by simple partial melting of mature sedimentary protoliths (plagioclase-poor metapelites). A more immature quartzofeldsphatic-rich (greywackes) and/or metaigneous (tonalites-granodiorites) crustal source may therefore be proposed. However, high CaO/Na₂O ratios can also result from mixing of strongly peraluminous crustal melts with basaltic magmas." (Aguado, 2005).

References

{{Reflist * Aguado, Beatriz Valle, M. Rosário Azevedo, John Nolan, and M. Estela Martins. (2005) "Origin and emplacement of syn-orogenic Variscan granitoids in Iberia the Beiras massif." ''Journal of the Virtual Explorer'', 2005 issues, Vol. 1

* Boiley, Miche, and Charles Gosselin. (2003) "Rare metal potential in the Near North, Québec." Geoscience Exhibi

* Fagiono, M. R., F. E. Nullo, J. E. Otamendi, et al. (2002) "Geología, petrología y mineralogía del granito Inti Huasi, sur de la sierra de Comechingones, Córdoba." ''Rev. Asoc. Geol. Argent.'', oct./dic. 2002, vol. 57, no. 4, p. 389–403. ISSN 0004-4822. Online Summar

* Green, Michael Godfrey. (2001) "Early Archaean Crustal Evolution: Evidence from ~3.5 Billion Year Old Greenstone Successions in the Pilgangoora Belt, Pilbara Craton, Australia." dissertation, School of Geosciences, Division of Geology and Geophysics, University of Sydne

* 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'' (1999), 136, pp. 285–300. Online Abstrac

* 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)." PhD thesis presented at University of Minho and University of Nancy (France). Online Abstract

Granite