1. Granites: classification, systematics, genesis, and some problems of the geodynamic typification.
Andrei Vl. Grebennikov
Far East Geological Institute, Far Eastern Branch of the Russian Academy of Sciences,
“There are granites and granites” H.H. Read (1957)

2. «GRANITES – THE VISITING CARD OF THE EARTH»
Granite is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. The word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a holocrystalline rock. By definition, granite is an igneous rock with at least 20% quartz and up to 65% alkali feldspar by volume.
Granite is classified according to the QAPF diagram for coarse grained plutonic rocks and is named according to the percentage of quartz, alkali feldspar and plagioclase feldspar on the A-Q-P half of the diagram. True granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite. When a granitoid contains less than 10% orthoclase, it is called tonalite; pyroxene and amphibole are common in tonalite. A granite containing both muscovite and biotite micas is called a binary or two-mica granite.
The most common rocks of the Earths upper continental crust;
Almost lack on other terrestrial planets;
Their intrusion is conditioned by tectonic and geodynamic processes;;
Interrelation with industrial concentrations of mineral…

3. INTRUSIVES migmatite Subvolcanic – few hundred meters;
Hypabyssal – up to кm;
Abbysal …
Concordant) and discordant granites.
Allochthonous granite, as opposed to autochthonous granite. 
Granitization states that granite is formed in place by extreme metasomatism by fluids bringing in elements, e.g. potassium, and removing others, e.g. calcium, to transform the metamorphic rock into a granite.
migmatite

4. in the Stillwater Complex in Montana.
Origin of granites
Norman Levi Bowen
He published “The Evolution of the Igneous Rocks” in This book set the stage for a geochemical and geophysical foundation for the study of rocks and minerals. This book became the petrology handbook.
As a melt cools minerals crystallize that are in thermodynamic equilibrium with the melt;
As the melt keeps cooling and minerals keep crystallizing, the melt will change its composition;
The earlier formed crystals will not be in equilibrium with this melt any more and will be dissolved again to form new minerals;
The common minerals of igneous rocks can be arranged into two series, a continuous reaction series of the feldspars, and a discontinuous reaction series of the ferromagnesian minerals (olivine, pyroxene, hornblende, biotite);
This reaction series implies that from a single "parental magma" all the various kinds of igneous rocks can be derived by Magmatic Differentiation .
This relationship
can be seen
in the Stillwater Complex in Montana.

5. “Lithogenesic" model of granite FORMATION
(V.I. Vernadsky, N.V. Frolova et al.).
Granites are very abundant on the Earth, but they are not present on other Earth-type planets. This may happen because the basaltic substance of a primary crust on the Earth (contrary to the Moon and the Venus) was changed by weathering and sedimentary sorting that prepared this material to subsequent melting and transformation into granite.

6. Granitization (D.S. KORZHINSKII, L.L. Perchuk et al.).
Granitization, formation of granite or closely related rocks by metamorphic processes, as opposed to igneous processes in which such rocks form from a melt, or magma, of granitic composition. In granitization, sediments are transformed in their solid state or in a partially molten state. The solid-state process requires the addition and removal of various chemical components by solid-state diffusion, vapour transport, or the movement of certain fluids such as aqueous solutions.
The deeper is the magma source, the higher can the watered magma rise.
Allochthonous granites are related to the deeper core sources. They have relatively high initial temperature and are more undersaturated with water that enables distant melt migration. If the depth of the source is less, the melt gets saturated and hardens not so far from the place of origin to become migmatite (autochthonous granites).

7. Earth’s internal, layered structure
Granites are final stage in the enveloping crust of the Earth;
the composition of the protoplanetary substance is close to chondrite;
differentiation led to the formation of upper mantle (peridotite=mgOl+Px);
partial mantle melting produced the formation of protocrust (Ol+Px+Pl and Grt+Px);
Px was replaced by Amf in the process of further alterations;
dehydration of Amf caused the transition of Q+Pl into the melt and formation of low-K primary crustal granites (P-type granite);
these granites and products of their decomposition after magma recycling are parental for I-, S- and A-type granites.
Попов В.С., Новая геохимическая модель формирования континентальной литосферы Земли. Известия вузов. Геология и разведка 1, 3–19.
Пущаровский Ю.М., Сейсмотомография и структура мантии: Тектонический ракурс. ДАН 351 (6),

8. Classification of granites
Mineralogical classification (IUGS, BGS, et al.);
Chemical classification (e.g., ASI, S-A-I-M);
Tectonic classification (based on plate tectonic setting).
IUGS – the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks
BGS – British Geological Survey
Classification is a general process related to categorization, the process in which ideas and objects are recognized, differentiated, and understood. A classification system is an approach to accomplishing classification.
A diagram is a symbolic representation of information according to some visualization technique. Diagrams have been used since ancient times, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three-dimensional visualization which is then projected onto a two-dimensional surface. The word graph is sometimes used as a synonym for diagram.
Discriminant analysis is a method used in statistics, pattern recognition and machine learning to find a linear combination of features that characterizes or separates two or more classes of objects or events. The resulting combination may be used as a linear classifier, or, more commonly, for dimensionality reduction before later classification.

9. Mineralogical classifications
Classification is based on descriptive attributes, such as composition and grain size, not interpreted attributes. The classification is non-genetic as theories on genesis can change with time and fashion but observed or measured parameters should stay the same.

10. QAPF classification
Granite is classified according to the QAPF diagram for coarse grained plutonic rocks and is named according to the percentage of quartz, alkali feldspar (orthoclase, sanidine, or microcline) and plagioclase feldspar on the A-Q-P half of the diagram. True granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite. When a granitoid contains less than 10% orthoclase, it is called tonalite; pyroxene and amphibole are common in tonalite. A granite containing both muscovite and biotite micas is called a binary or two-micagranite. Two-mica granites are typically high in potassium and low in plagioclase
Q, A, P and F comprise the felsic minerals; minerals included under M are considered to be mafic in the context of the modal classifications. The sum of Q + A + P + F + M must be 100%. Minerals in Q and F are mutually exclusive. For each rock, the modal volumes for each group of minerals must be known and QAP or APF recalculated so that their sum is 100%. For example, a rock with Q = 10%, A = 30%, P = 20% and M = 40% would give recalculated values of Q, A and P as follows:
Q= 100*3*10/60 = 16.7
A= 100*3*30/60 = 50.0
P = 100*3*20/60 = 33.3
Streckeisen, A Classification and nomenclature of volcanic rocks, lamprophyres, carbonatites and melilitic rocks:
recommendations and suggestions of the IUGS Subcommission on the Systematics of Igneous Rocks. Geology 7, 331–335.

11. TAS diagram for intrusive rocks (?)
Green fields – intrusive rocks;
Red fields – volcanic rocks.
Le Bas, M.J. et al., A chemical classification of volcanic rocks based on the total alkali-silica diagram. Journal of Petrology 27, 745–750.
Шарпенок, Л.Н. и др., TAS-диаграмма сумма щелочей–кремнезем для химической классификации и диагностики плутонических пород. Региональная геология и металлогения 56, 40–50.

12. Aluminum saturation index (ASI)
This ratio has been referred to as A/CNK by Clarke,1981
and the Aluminium Saturation Index ASI by Zen, 1986.
Shand, S. J. (1943). The Eruptive Rocks, 2nd edn. New York: John Wiley, 444 pp.
This is defined as the molecular ratio Al/(Ca – 1.67P + Na +K). Rocks that have ASI >1.0 are corundum-normative and are termed peraluminous. This means that they have more Al than can be accommodated in feldspars and that they must have another aluminous phase present.
If ASI <1.0 but if molecular Na + K < molecular Al, then the rock is metaluminous. In such rocks there is likely to be excess Ca after aluminum has been accommodated in the feldspars.
If ASI <1.0 and Na + K > Al, the rock is peralkaline. In these rocks there are more alkalis than are necessary to produce feldspar, which means that some alkali, particularly Na, must be accommodated in the ferromagnesian silicates.

13. советский геохимик, академик АН СССР
Chemical classification
Lev Vladimirovich
Tauson
советский геохимик, академик АН СССР
Палингенез (pálin — снова, и génesis — происхождение, рождение), образование магм за счет частичного или полного плавления осадочных, метаморфических или магматических горных пород в условиях земной коры.

14. or S-I-M-A (e.g., Sial et al., 1987).
The “genetic alphabet soup”, referred to as S-I-A-M (e.g., Clarke, 1992),
or S-I-M-A (e.g., Sial et al., 1987).
1. S- and I-types are the oldest defined granite types (Chappell and White, 1974).
2. M-type is akin to Archean TTGs and modern adakites (for an overview, see Martin et al., 2005).
3. The type with no letter attributed corresponds to A-type.
Chappell, B.W., White, A.J.R., Two contrasting granite types. Pacific Geology 8, 173–174.

15. M-, C-type and others
There is no need of a specific letter, C-type, for a charnockite type, and for M-type, for mantle-derived source (Bonin, 2007).
At the GSA Annual Meeting held at San Diego in November 1979, White offered a summary of the genetic alphabet scheme, he introduced the M-type, inferred to be formed by partial melting of subducted oceanic crust. Though White stated: “these (granites) are the only mantle or M-types”, M-refers actually to mantle-derived sources and mantle conditions, not to mantle sources (Clemens,
written communication, 2005);
C-type, proposed in the 2nd Hutton Symposium on Granites held in Australia (Kilpatrick and Ellis, 1992). C-type was not successful in gaining wide acceptance.
Compared with A-type magmas, C-type rocks (Elliott, 2003) yield higher contents of Zr and HFSE, Ba and Sr, with no to weak Eu negative anomalies. Zircon and feldspar accumulation features suggest that C-type rocks represent a solid, not liquid, line of descent and that no C-type magmas can be defined.
Bonin, B., A-type granites and related rocks: Evolution of a concept, problems and prospects. Lithos 97, 1–29.
Xiao, L., Clemens, J.D., Origin of potassic (C-type) adakite magmas: Experimental and field constraints. Lithos 95, 399–414.
Martin, H., Smithies, R.H., Rapp, R., Moyen, J.F., Champion, D., An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos 79, 1–24.

16. I – igneous source; S – (meta-) sedimentary source
I-types
S-types
Relatively high sodium, Na2O normally >3.2% in felsic varieties, decreasing to >2.2% in more mafic types
Relatively low sodium, Na2O normally <3.2% in rocks with ~ 5% K2O, decreasing to <2.2% in rocks with ~ 2% K2O
Mol. Al2O3/(Na2O + K2O + CaO) <1.1
Mol. Al2O3/(Na2O + K2O + CaO) >1.1
CIPW normative diopside or < 1% normative corundum
>1% CIPW normative corundum
Broad spectrum of compositions from felsic to mafic
Relatively restricted in composition to high SiO2 types
Hornblende is common in the more mafic I-types and generally present in felsic varieties;
Sphene is a common accessory in the I-type;
Apatite inclusions are common in biotite and hornblende of I-type granites;
hornblende-bearing xenoliths;
Initial Sr87/Sr86 ratios in the range 0.704–0.706
Hornblende is absent, but muscovite is common, in the more felsic S-types, biotite may be very abundant, up to 35%, in more mafic S-types;
Monazite may be found in S-types;
Aluminosilicates (garnet and cordierite) may occur in S-type xenoliths or in the granites themselves;
Apatite occurs in larger discrete crystals in S-types;
metasedimentary xenoliths;
Initial Sr87/Sr86 >0.708
Volcanic rocks typically contain Qz, Pl, Opx and Cpx
Volcanic rocks typically contain Qz, Pl, Opx and Crd
low-temperature I-type contains abundant inherited zircon, formed in a tectonic setting other than simple subduction (cf. Collins 1998).
high-temperature I-type lacks inherited zircon.
two-mica leucogranite representing pure crustal melts of thermal minimum composition,
cordierite- or garnet-bearing granitoids explained as retaining a strong Al-rich restitic component.
U–Pb (zircon) and Zr (bulk-rock) studies of low temperature I-type granites reveal that they crystallized from zircon-undersaturated magmas and inherited zircon crystals reflect melting and assimilation of a meta-sedimentary source (Kemp et al., 2005).
Sr–Nd isotopic data show that two-mica leucogranite could result exclusively from the melting of metagranites (Turpin et al., 1990) and experimental studies (Patino Douce, 1991, 1999) show that incorporation of at least 50% basalt into 50% metapelite is required to generate liquids of S-type composition
CHAPPELL B. W. & WHITE A. J. R Two contrasting granite types. Pacific Geology 8, 173–174.
CHAPPELL B. W. & WHITE A. J. R Two contrasting granite types: 25 years later. Australian Journal of Earth Sciences (2001) 48, 489–499.

17. S-Type granitoids – syn-collisional granitoids (Pearce et al
S-Type granitoids – syn-collisional granitoids (Pearce et al., 1984), continental collision
granitoids (Maniar & Piccoli, 1989), and muscovite–peraluminous granites (Barbarin, 1999)
These rocks are muscovite-bearing, high-silica granites that occur as isolated plutons in the cores of
overthickened metamorphic belts (see Le Fort, 1981).
they are distinctive in that they typically are not associated with more mafic rocks;
these leucogranites are thought to be generated by partial melting of metasedimentary rocks.
I-Type (Andean) granitoids – volcanic arc granites (Pearce et al., 1984), island arc and continental arc granitoids (Maniar & Piccoli, 1989), or amphibole-bearing calc-alkalic granites (Barbarin, 1999)
I-type = Igneous or Infracrustal;
granitoids are dominantly magnesian and are mostly calcic
and calc-alkalic(Frost et al., 2001);
the opaque mineral in the I-type
granites is generally magnetite
rather than the ilmenite that is
typical of the S-type granites
(Whalen & Chappell 1988);
e.g. Cordillieran granites.

18. Peraluminous I-type granites !?
«I-type igneous rocks are commonly, wrongly, conceptualised as being metaluminous, but more than half of the low-temperatures I-types analysed from the LFB in SE Australia are peraluminous».
During the dehydrational melting of I-type granite source rocks at pressures below the garnet stability field, biotite and amphibole melt incongruently to yield pyroxenes. The excess Al is incorporated into the felsic liquid, resulting in the generation of peraluminous melts. In this instance, the excess Al in felsic I-type granites is a function of the melting process, and unrelated to the bulk composition of the source.
Chappell, B.W., Bryant, C.J., Wyborn, D., Peraluminous I-type granites. Lithos 153, 142–153
The origin of the low-temperature I-type granites of the Lachlan Fold Belt formed in a tectonic setting other than simple subduction (cf. Collins 1998);
the I-type melt is more peraluminous than the source (commonlymetaluminous). This contrasts with the scenario for S-types were the melt is less peraluminous than the source rock (initially peraluminous).
A/NK (Al2O3/Na2O+K2O) vs. A/CNK (Al2O3/CaO+Na2O+K2O, all in molar quantities) diagram of Shand's index (Maniar and Piccoli, 1989)

19. A-type granites and related volcanic rocks
A-type spectrum (where A stands for anhydrous, alkaline, anorogenic as well as aluminous) to distinguish them from the well-known classification of S- and I-types.
The current classification schemes of A-type granites can be confusing and so complex as to be difficult to apply.
A-type rocks are associated with ultramafic rocks, alkali and tholeiitic basalts, and intermediate rocks (Richey et al., 1961);
A-type granites were originally defined for continental areas, but most, if not all, granitic rocks emplaced within oceanic contexts share A-type characteristics and are associated with alkaline, transitional, or tholeiitic mafic rocks (e.g., Giret, 1990).
On Moon, 4.4–3.9 Ga granite clasts display Qz + Or An Fa + Px+Ilm+accessory minerals + FeS + Fe–Ni metal assemblage, indicating fayalite–iron–quartz (FIQ) buffering conditions (Warren et al., 1983) striking affinities to WPG and A-type high-silica granites;
They were generated in environments that differed markedly from those prevailing currently
on Earth. Such occurrences afford strong evidence that, contrary to the conventional wisdom, the association of liquid water, continental crust and plate tectonics does not constitute a prerequisite for generation of A-type granitic liquids.(Bonin, 2007).

20. The A-type concept Loiselle and Wones abstract became rapidly one
of the most frequently cited abstracts in the granite literature – results from
the fact that Loiselle and Wones published no subsequent paper on A-type granite.
The first published paper using the term A-type (Collins et al., 1992) concerned Australian occurrences
and developed the residual source model.
Loiselle, M.C., Wones, D.R. Characteristics and origin of anorogenic granites. Abstracts of papers to be presented at the Annual Meetings of the Geological Society of America and Associated Societies. San Diego. California. November P. 468.
Collins, W.J., Beams, S.D., White, A.J.R., Chappell, B.W., Nature and origin of A-type granite with particular reference to southeastern Australia. Contributions to Mineralogy and Petrology 80,

21. Zr+Nb+Ce+Y vs FeO. /MgO and (K2O + Na2O)/CaO; 10000
Zr+Nb+Ce+Y vs FeO*/MgO and (K2O + Na2O)/CaO; 10000*Ga/Al vs Ce, Zr, Nb, Y plots of A-type granites and also fields for fractionated felsic granites (FG) and unfractionated M-, I- and S-type granites (OGT).
- A-type rocks
Whalen J.B., Currie K.L., Chappell B.W., A-type granites: geochemical characteristics, discrimination and petrogenesis. Contributions to Mineralogy and Petrology 95,

22. Note that post-collision granites can plot in all but the ORG fields,
Trace element discrimination diagrams for the tectonic interpretation of granitic rocks.
Note that post-collision granites can plot in all but the ORG fields,
and that supra-subduction zone ocean ridge granites plot in the VAG field.
- A-type rocks
Pearce J.A., Harris N.B.W., Tindle A.G. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks // Journal of Petrology P
Harris N.B.W., Pearse J.A., Tindle A.G. Geochemical characteristics of collision-zone magmatism / Cowards M.P., Ries A.C. (Eds.). Collisions tectonics. Geological Society, London, Special Publication P

23. Ternary petrogenetic diagram Nb–Y–Ce (ppm) for A-type granites
«These A1 and A2 discriminant diagrams should only be used for granitoids that plot both in the within-plate granite field of Pearce et al. (1984) and the A-type
granitoid field of the Ga/Al plots of Whalen et al. (1987)».
A1: Field of silicic rocks of oceanic islands, continental rifts, and hot spots (dark symbols), formed from within-plate or rift OIB;
A2: Field of postcollisinal, postorogenic, and anorogenic granitoids (light symbols) formed from IAB and continental-margin basalts, from crustal tonalites and granodiorites, or through the partial
melting of crust.
Eby, G.N., Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications. Geology 20,

24. Approximate ranges for the alkalic, alkali–calcic, calc-alkalic, calcic and magnesian, and ferroan rock series (Frost et al., 2001).
Frost et al. (2001) proposed a specific classification of felsic igneous rocks according to their petrochemical composition. He
took three chemical parameters as a basis: (1) index FeO*/(FeO* + MgO) > ×SiO2 wt.%, permitting separation of magnesian and ferroan (A-type) granitoids, (2) Peacock modified alkali–lime index (Na2O + K2O–CaO) (MALI), and (3) alumina saturation index (ASI) Al/(Ca–1.67×P + Na + K), permitting division of felsic igneous rocks into peraluminous (ASI > 1.0), metaluminous (ASI < 1.0, (Na + K) < Al), and peralkaline (ASI < 1.0, (Na + K) > Al) ones.
Scheme illustrating petrogenesis of ferroan granitoids of different types (Frost and Frost, 2011).
Frost B.R. et al., A geochemical classification for granitic rocks. Journal of Petrology 42,
Frost C.D., Frost B.R., On ferroan (A-type) granitoids: their compositional variability and modes of origin. Journal of Petrology 52,

25. Diagrams(Dall’Agnol and Olivera, 2007) with fields of
Calc-alkaline and А-type granites (”oxidized” and “reduced”)
Anderson J.L., Bender E.E. Nature and origin of Proterozoic A-type granitic magmatism in the southwestern United States of America // Lithos P
The refining term “oxidized A-type” introduces still more uncertainty in the definition of A-type granitoids, because most of the above-discussed classifications cannot distinguish be- tween such rocks and both A-type granites and orogenic calc-alkaline I-type granites.
Dall’Agnol R., Olivera D.C. Oxidized, magnetite-series, rapakivi-type granites of Carajas, Brasil: Implications for classification and petrogenesis of A-type granites // Lithos P

26. Major features of A-type granite igneous suites
A-granite associations
Their associations were mapped on all continents (including Antarctica), and the time of their formation varies
Time
Neoarchean (~2.7 Ga) to Cenozoic (10 Ma and younger)
Form
They are rather rare in the lower crust (like, e.g., some charnockite complexes) but are typical of subsurface subvolcanic levels, forming circular root feeders of calderas.
Classification
These granitoids are usually classified as quartz syenites and metaluminous and peralkaline granites, and their volcanic analogs are treated as vitrophyric rhyolites, comendites, and pantellerites
Geochemistry
They have an alkaline calcic to alkaline ferroan bulk composition, high contents of LILE, HFSE (first of all, Nb, Ga, and Y), and REE (except for Eu), and low contents of Sr, Sc, and V and are rich in halogens, especially F.
Mineralogy
The presence of ferroan silicates (ferrohedenbergite, ferrohastingsite, fayalite, and annite) or aegirine, arfvedsonite, and riebeckite (in agpatitic granites) as well as pertitic feldspar.
Genesis
Since A-type granites are observed in association with mafic igneous rocks both on the continents and on the ocean bottom, they are regarded as mantle products of alkaline melts. Their Rb/Sr and Sm/Nd isotope ratios testify to the presence of mantle melt traces.
Metallogenic significance
A-type granites are recognized as important carriers of Sn (±W, ±Ta, ±Nb, ±Be), as well as F, Zr, Y, and the REE. Rare porphyry-copper and base-metal occurrences are also related to A-type granites. A-type granites are spatially associated with important Fe–Cu and Cu–Au (REE-U) deposits, but whether there is a petrogenetic relationship involved is unclear.
Geodynamic
A-type granite associations are related to extensional regimes. These may develop both in domains of regional extension (divergent plate boundaries) and regional contraction (oblique collisions; slab breakoff, foundering) that demote mixing of mantle- and crust-derived magmas and allow them to develop along discrete liquid lines of descent.

27. an approach competing method;
«Popular opinion that the specific features of igneous rocks cannot be recognized because of the negligible difference in the composition of the major oxides in rocks with similar SiO2 contents» ???
an approach competing method;
dispersed elements in felsic melts (in contrast to basalts) are usually incompatible (Bea, 1996).
rare-earth elements, U, Th, and Zr are present mainly in accessory minerals: apatite, zircon, sphene, orthite, and monazite. Other elements, including Nb and Y, concentrate in oxides and amphiboles;
crustal contamination also exerts a stronger effect on the contents of dispersed elements in granitic melts as compared with more mafic melts…
The choice of rock-forming elements as a basis for classification of granites:
Fe, Mg, Ca, K and Na.

28. Fenitization-type
The mantle-derived fluid is alkali- and silica-bearing, and is able to transport a very wide array of elements, including the high field-strength elements, and a broad variety of anions are available to do the job. Fenitization-type reactions transform the refractory intermediate to mafic rocks of the lower crust to fertile assemblages that can melt (in cases completely) to give A-type granitic magmas of metaluminous or peralkaline character, or nepheline syenitic magmas, or carbonatitic magmas (Martin, 2006, 2012).
Granitic magmas are generated deep in the continental crust under the influence of heat or more exactly heat and fluid flows;
fluids are supercritical mixtures of mainly gaseous components (H2O, CO2, CH4, H2, Ar, He, etc.). Their deep-seated nature is confirmed by high content of heavy isotopes of carbon and hydrogen;
the granitization process comes to removal of Mg, Fe, Ca and Ti from the parent rocks by alkaline fluids, against the increasing concentrations of Na2O, K2O, SiO2 as well as trace elements so characteristic of granites.
MeO + H2 = Me + H2O;
FeO + H2 → Fe + H2O;
Fe2O3 + 3H2 →2Fe + 3H2O.
Grebennikov, A.V. et al., Silicate–Metallic Spherules and the Problem of the Ignimbrite Eruption Mechanism: The Yakutinskaya volcanic depression. Journal of Volcanology and Seismology 6 (4),

29. Comparison of (Na2O+K2O) – Fe2O3T ×5 – (CaO+MgO)×5 (mol. %)
and Nb – Y – Ce (ppt), for A-type granites.
130 analyses
A-1 representative of a rift environment: Naivasha, East African Rift system; Zomba-Malosa, Chilwa province, Malawi; Yemen rift ; and the Eastern Trans-Pecos magmatic province, Texas. As representative of a hotspot or plume environment the following have been selected: White Mountain batholith, New Hampshire; Kaerven complex, East Greenland; Ras ed Dom complex, Sudan; and Velasco, Bolivia.
A-2 representative of the postcollisional or postorogenic environments: Gabo and Mumbulla, Lachland fold belt, Australia; Topsails complex, Newfoundland; Habd-Aldyaheen, Arabian Peninsula; Malani suite, northern India; Narraburra granite, Lachland fold belt; and subalkalic-peralkalic rhyolites of the southern British Caledonides. The rapakivi granites are also members of this second chemical group, and a rapakivi suite (Suomenniemi complex) from Fennoscandia is included as an example.
Grebennikov, A.V., A-type granites and related rocks: petrogenesis and classification. Russian Geology and Geophysics 55 (11), 1353–1366

30. The advantage of the ternary (Na2O + K2O)–Fe2O3
The advantage of the ternary (Na2O + K2O)–Fe2O3*×5–(CaO + MgO)×5 for the reliable separation of A-type granitoids and felsic igneous rocks of other types
MORE THAN 2500
ANALYSES
CaO (mol.) = CaO (wt. %) × 1000/56.08;
MgO (mol.) = MgO (wt. %) × 1000/40.32;
Fe2O3 (mol.) = Fe2O3 (wt. %) × 1000/159.68;
Na2O (mol.) = Na2O (wt. %) × 1000/61.99;
K2O (mol.) = K2O (wt. %) × 1000/94.20.

31. The fields are separated by lines with coordinates:
«oxidized A-type

32. A-type classification diagram
1) The proposed ternary diagram (Na2O + K2O)–
Fe2O3*×5–(CaO + MgO)×5, based on the molecular quantities of rock-forming oxides, permits the reliable geochemical separation of A-type granitoids and felsic igneous rocks of other types.
2) The recognized fields of A-type rocks correspond to two petrogenetic types: resulted from the differentiation of alkali-basaltic magmas with minor assimilation (A1) and from the interaction of mantle melts with felsic continental crustal material accompanied by serious contamination (A2).
3) This diagram must be applied to interprete the geodynamic formation conditions with caution. It should be used as a tool for a comprehensive analysis of obtained geological, petrological, and geochemical information. Nevertheless, A1-type rocks form mostly in the
intraplate magmatism setting: in intraoceanic system (oceanic islands) or near the divergent boundaries of lithospheric plates in cold intracontinental rifts, whereas A2-type rocks are generated in the postcollisional (or late-collision) setting as well as during the lithospheric-plate sliding and at the late stages of evolution of hot rift structures.
The petrochemical data must be interpreted with regard to
the restrictions made by the author on the diagram testing:
One should use only felsic igneous rocks containing >67 wt.% SiO2; ignore rocks subjected to considerable secondary superposed alterations and volcanic glasses, fiammes, or their fragments as well as rocks with SiO2 > 80 wt.% and liquation products; make statistical processing of data in the 95% confidence interval for each complex of igneous rocks in order to achieve the maximum reliability of analytical results; and carefully interpret the compositions of oxidized (magnetite)
A-type granitoids (including postcollisional) because of the
expanding (up to 10%) zone of their overlapping with highly differentiated I- and S-type granitoids in the lowermost part of the field of A2-type granites.

33. The Sikhote-Alin area (Far East Russia)
Grebennikov, A.V., Khanchuk, A.I., Gonevchuk, V.G., Kovalenko, S.V. Cretaceous and Paleogene granitoid suites of the Sikhote–Alin area (Far East Russia): geochemistry and tectonic implications. Lithos (2016), doi: /j.lithos

34. Compiled by S.А. Kasatkin after Engebretson et al., 1985
The Mesozoic and Cenozoic geological history of NE Asia comprises alternating episodes of subduction or transform strike-slip movement of the oceanic plate along the continental margin of Eurasia.
The Hauterivian–Aptian orogenic stage of the Sikhote-Alin, associated with the strike-slip displacement of the early Paleozoic continental blocks, the successive deformation of the Jurassic and Early Cretaceous
terranes, and the injection of the earliest S-type granitoids.
During late Albian, the area underwent syn-strike-slip compression caused by collision with the Aptian island arc and resulted in the injection of voluminous magmas of calc-alkaline magnesian (S- and I-type) and alkali-calcic ferroan (A-type) granitoids into syn-faulting compressional and extensional basins, respectively.

35. Engebretson et al., 1985.
Northwestward to westward movement of the Izanagi Plate resulted in the initiation of frontal subduction of the Paleo-Pacific Plate during the Cenomanian–Maastrichtian. In turn, this resulted in the generation of plateau-forming ignimbrites and their intrusive analogs formed from metaluminous I-type felsic magmas.
Paleocene–Eocene magmatism in the Sikhote-Alin area commenced after the termination of subduction in a rifting regime related to strike-slip movement of the oceanic plate relative to the continent. The break-off of the subducted plate and the injection of oceanic asthenospheric material into the subcontinental lithosphere resulted in the eruption of lamproites and fayalite rhyolites, and coeval intrusions of gabbro and alkali feldspar granites (А-type).

36. Any diagram is just a tool structural position, and age.
Analysis of the data on any diagram permits us to relate, with some caution, igneous complexes to a particular geodynamic setting because the geochemical features of granitic magmas reflect mostly the composition of their source.
Moreover, volcanic facies (like intrusive ones) are complex products of intracrustal melts, basic magmas, and sedimentary substrate.
No one diagram is so informative for understanding the genesis and geodynamic setting of formation of igneous rocks as a comprehensive analysis of data on their composition, isotope properties,
structural position, and age.