Monzogranite
Encyclopedia
Monzogranites are biotite
granite
rocks that are considered to be the final fractionation
product of magma
. Monzogranites are characteristically felsic
(SiO2 > 73%, and FeO + MgO + TiO2 < 2.4), weakly peraluminous
(Al2O3/ (CaO + Na2O + K2O) = 0.98 - 1.11), and contain ilmenite
, sphene, apatite
and zircon
as accessory mineral
s. Although the compositional range of the monzogranites is small, it defines a differentiation trend that is essentially controlled by biotite
and plagioclase
fractionation
. (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.
MGr type II: Muscovite-metagranite. medium grained, porphyric, pink K-fsp, with "schollen", whitish-pink (with "Schollen").
MGr type III: Schollen-metagranite. medium & equal grained, large and many "schollen", whitish-grey, only biotite (Tuaní, S. Chepes &S. Ulapes south).
MGr type IV: Biotite-metagranit. medium to large, porphyric or equal grained pink K-fsp, reddish quartz (Chimenea, S.Chepes).
MGr type V: Metagranite. medium & equal grained reddish K-fsp whitish (El Abra, S.Ulapes).
MGr type V aplite: Metagranite, aplite dikes and layers. pink small & equal grained, whitish K-fdsp, grey qz, pink-white (S. Ulapes north).
Granite
–Greenstone
Terrane
ca. 3.315 Ga monzogranites are typically highly fractionated
, 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 (<5 cm), holocrystalline and composed of plagioclase
(30-40%), quartz
(30-40%), microcline
(25-30%), mafic
mineral
s (<5%), and muscovite
(<5%). In general, the texture
is similar to granodiorite
s, with zoned subhedral plagioclase, and anhedral microcline and quartz. However, microcline is commonly poikilitic
, with abundant fine-grained plagioclase and quartz. Monzogranites contain medium-grained subhedral muscovite and sometimes trace amounts of embayed, corroded fine-grained garnet
." (Green, 2001).
's Near North, early monzogranites are moderately fractionated (Rb
/Sr
= 0.15-3.9) and show moderate to high La
/Yb
CN (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 [La/Yb]CN (0.2-45) ratios. (Boiley and Gosselin, 2003)
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 due to crustal thinning associated with extension in the late stage of the Neoproterozoic crustal evolution of north-eastern Egypt." (Moghazi, 1999).
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
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...
rocks that are considered to be the final fractionation
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...
product of 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...
. Monzogranites are characteristically felsic
Felsic
The word "felsic" is a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium....
(SiO2 > 73%, and FeO + MgO + TiO2 < 2.4), weakly peraluminous
Peraluminous
Peraluminous rocks are igneous rocks that have a molar proportion of aluminium oxide greater than that of sodium oxide, potassium oxide and calcium oxide combined. Compare with peralkaline, metaluminous, and subaluminous. Examples of peraluminous minerals include biotite, muscovite, cordierite,...
(Al2O3/ (CaO + Na2O + K2O) = 0.98 - 1.11), and contain ilmenite
Ilmenite
Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....
, sphene, apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
and zircon
Zircon
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...
as accessory mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s. Although the compositional range of the monzogranites is small, it defines a differentiation trend that is essentially controlled by biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
and plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
fractionation
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...
. (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
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
data, and the locality in which they are found.
monzogranite rock types
MGr type I: Muscovite-biotite-metagranite. small & 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 & equal grained, large and many "schollen", whitish-grey, only biotite (Tuaní, S. Chepes &S. Ulapes south).
MGr type IV: Biotite-metagranit. medium to large, porphyric or equal grained pink K-fsp, reddish quartz (Chimenea, S.Chepes).
MGr type V: Metagranite. medium & equal grained reddish K-fsp whitish (El Abra, S.Ulapes).
MGr type V aplite: Metagranite, aplite dikes and layers. pink small & equal grained, whitish K-fdsp, grey qz, pink-white (S. Ulapes north).
Pilgangoora Belt, Pilbara craton monzogranites
PilbaraPilbara craton
The Pilbara craton , along with the Kaapvaal craton are the only remaining areas of pristine Archaean 3.6-2.7 Ga crust on Earth...
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...
–Greenstone
Greenstone belt
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies....
Terrane
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
ca. 3.315 Ga monzogranites are typically highly fractionated
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...
, K rich, Al poor, and have trace element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
compositions consistent with remelting of an older tonalitic
Tonalite
Tonalite is an igneous, plutonic rock, of felsic composition, with phaneritic texture. Feldspar is present as plagioclase with 10% or less alkali feldspar. Quartz is present as more than 20% of the rock. Amphiboles and pyroxenes are common accessory minerals.In older references tonalite is...
–trondhjemitic
Trondhjemite
Trondhjemite is a leucocratic intrusive igneous rock. It is a variety of tonalite in which the plagioclase is mostly in the form of oligoclase. Trondhjemites are sometimes known as plagiogranites....
–granodioritic
Granodiorite
Granodiorite is an intrusive igneous rock similar to granite, but containing more plagioclase than orthoclase-type feldspar. Officially, it is defined as a phaneritic igneous rock with greater than 20% quartz by volume where at least 65% of the feldspar is plagioclase. It usually contains abundant...
(TTG) crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
.
Carlindi monzogranites in the greenstone belt
Greenstone belt
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies....
are light greyish-pink coloured, "massive, coarse-grained (<5 cm), holocrystalline and composed of plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
(30-40%), 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,...
(30-40%), microcline
Microcline
Microcline 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 slow cooling of orthoclase; it is more stable at lower temperatures...
(25-30%), mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s (<5%), and muscovite
Muscovite
Muscovite is a phyllosilicate mineral of aluminium and potassium with formula KAl22, or 236. It has a highly-perfect basal cleavage yielding remarkably-thin laminæ which are often highly elastic...
(<5%). In general, the texture
Texture (geology)
Texture in geology refers to the physical appearance or character of a rock, such as grain size, shape, arrangement, and pattern at both the megascopic or microscopic surface feature level. This includes the geometric aspects and relations amongst the component particles or crystals which is called...
is similar to granodiorite
Granodiorite
Granodiorite is an intrusive igneous rock similar to granite, but containing more plagioclase than orthoclase-type feldspar. Officially, it is defined as a phaneritic igneous rock with greater than 20% quartz by volume where at least 65% of the feldspar is plagioclase. It usually contains abundant...
s, with zoned subhedral plagioclase, and anhedral microcline and quartz. However, microcline is commonly poikilitic
Poikilitic
Poikilitic texture refers to crystals, typically phenocrysts, in an igneous rock which contain small grains of other minerals. The texture is most easily observed in petrographic thin sections....
, with abundant fine-grained plagioclase and quartz. Monzogranites contain medium-grained subhedral muscovite and sometimes trace amounts of embayed, corroded fine-grained garnet
Garnet
The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...
." (Green, 2001).
Quebec's Near North monzogranites
In QuebecQuebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
's Near North, early monzogranites are moderately fractionated (Rb
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
/Sr
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
= 0.15-3.9) and show moderate to high La
Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
/Yb
Ytterbium
Ytterbium is a chemical element with the symbol Yb and atomic number 70. A soft silvery metallic element, ytterbium is a rare earth element of the lanthanide series and is found in the minerals gadolinite, monazite, and xenotime. The element is sometimes associated with yttrium or other related...
CN (14-106) and Zr
Zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name of zirconium is taken from the mineral zircon. Its atomic mass is 91.224. It is a lustrous, grey-white, strong transition metal that resembles titanium...
/Y
Yttrium
Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
(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
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
= 6-55 ppm, Be
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
= 1-3 ppm and Ta
Tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...
= 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
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
anomalies, low REE
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
contents and low to moderate [La/Yb]CN (0.2-45) ratios. (Boiley and Gosselin, 2003)
Vigo-Regua Shear Zone, Northern Portugal mozogranites
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 monzogranites
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 [set membership]Nd values (+6.9–+7.3) and are significantly different from those (initial 87Sr/86Sr ratio=0.7029, [set membership]Nd 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.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 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 monzogranites
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).See also
- biotiteBiotiteBiotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
- graniteGraniteGranite 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...
- List of rock types
- List of minerals
- Igneous rocks
- SkarnSkarnSkarn is an old Swedish mining term originally used to describe a type of silicate gangue, or waste rock, associated with iron-ore bearing sulfide deposits apparently replacing Archean age limestones in Sweden's Persberg mining district. In modern usage the term "skarn" has been expanded to refer...
- GreisenGreisenGreisen is a highly altered granitic rock or pegmatite. Greisen is formed by autogenic alteration of a granite and is a class of endoskarn.Greisens appear as highly altered rocks, partly coarse, crystalline granite, partly vuggy with miarolitic cavities, disseminated halide minerals such as...
- ApliteApliteAplite in petrology, the name given to intrusive rock in which quartz and feldspar are the dominant minerals. Aplites are usually very fine-grained, white, grey or pinkish, and their constituents are visible only with the help of a magnifying lens...
- BatholithBatholithA batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust...
- Pilbara cratonPilbara cratonThe Pilbara craton , along with the Kaapvaal craton are the only remaining areas of pristine Archaean 3.6-2.7 Ga crust on Earth...
- Gascoyne ComplexGascoyne ComplexThe Gascoyne Complex is a terrane of Proterozoic granite and metamorphic rock in the central-western part of Western Australia. The complex outcrops at the exposed western end of the Capricorn Orogen, a 1,000 km-long arcuate belt of folded, faulted and metamorphosed rocks between two Archean...
, Dalgaringa Supersuite