First of all, my compliments for a very nice summary.

I do not see a problem with the use of the term adakite since, as you say, these rocks have some distinct chemical characteristics when compared with "classical" arc-related granitic plutons. Whether these chemical signatures are related to higher degree of melting, fractional crystallization or source composition is a separate issue.

But I agree that the term should not be linked with genesis of hydrothermal mineral deposits. There are examples of "barren" adakitic rocks.

Hi Daniel. this is a subject I've been chasing for a while and I think I can contribute to the discussion.

The term "adakite" has been problematic since it was first proposed, not least because it was intended to denote rocks of a very particular origin, namely from melting of the subducted slab. As we all know, interpretations are subject to change. The very same Adak Island magmas are not currently interpreted as salb melts!

As far as we know, magmas formed by melting of the slab do exhibit certain chemical characterisitics, such as elevated Sr/ and La/Yb, among others. But, and this is a big caveat, there are several other ways to obtain the same chemical signature! There is no one-to-one relation. So the tendency has been to abandon the use of the term "adakite" because of its genetic implications, and use the adjective "adakitic" instead in a more descriptive way.

Having said that, it is robust observation that ALL giant porphyry Cu deposits, at least in the Andes, are related to adakitic magmas. They are not only loosely related, instead most of the time adakitic magmas can be identified as "causative" of the mineralization. We should keep in mind that adakitic composition is a characterisitic of magmas and not of hydrothermal systems. The first-order lesson that I draw from these observations is that not all magmas are equally productive, some have more potential to generate mineral concentrations than others. This, of course, doesn't preclude the existence of barren adakitic plutons since magma composition is but one of several contributing factors.

There have been many different mechanisms proposed to explain the origin of these adakitic magmas related to Cu mineralization, and it wouldn't be too surprising that some of those mechanisms apply to shoshonites as well. I think we need to advance into the petrogenetic interpretation of the chemical characteristics of rocks related to mineralization rather than use a simple label.

Wow!

I am squashed between two adakite guys.

Greetings to all of you, I am also chasing this problem and I think despite the numerous controversy this geochemical feature must be of prime importance when dealing with 'Porphyry Cu deposit' and their origin other than 'slab-melting' is very defined now. It is now emperically established fact that most of porphyry Cu deposit have 'Adakitic' nature of host granite and now the question is how the fertile hydrothermal system can be geneated by the 'Adakitic' host? Moreover, the source of Cu is also highly debatable. Let me add in the end that infact some of precambrian Cu deposite also have 'Adakitic' nature of host and therefore high Sr/Y, La/Yb must have some genetic link with 'Porphyry Cu deposit'.

Regards.

Daniel Müller Sir, I have some doubt that all the high k and shoshonitic igneous rocks are not necessarily high in Sr/Y and La/Yb and if some of them have, then simply we should called them 'Adakites'.

Regards.

Dear all,

I agree with Saurabh,

not all high-K and/or shoshonitic rocks have the “adakitic” signature (e.g. high Sr/Y and La/Y),

Cheers,

Felipe

Dear Saurabh, many thanks for your thoughtful comments! My main concern with the term "adakitic" is the fact that it does not reflect the high volatile contents (e.g. chlorine) of fertile melts that are capable of forming porphyry Cu mineralization. By contrast, high-K magmas are defined by, among other criteria such as high LILE and LREE, their high volatile contents. Modern analytical methods increasingly confirm the importance of high chlorine contents in the formation of porphyry Cu deposits.

Hi Felipe, many thanks for joining the debate! Would you mind to please send me some examples? Please kindly have a look at the following list of references on high-K intrusions that have been labelled as "adakites" in the respective paper, but in fact they have very similar compositions:

1) Wang J et al. (2017) Shoshonitic and adakitic magmatism of the early Paleozoic age in the western Kunlun orogenic belt, NW China: implications for the early evolution of the northwestern Tibetan plateau. Lithos 287: 345-362

2) Xie J et al. (2018) Petrogenesis and metallogenic implications of Late Mesozoic intrusive rocks in the Tongling region, eastern China: a case study and perspective review. International Geology Review (in press)

3) Sun X et al. (2018) Miocene ultrapotassic, high-Mg dioritic and adakite-like rocks from Zhunuo in southern Tibet: implications for mantle metasomatism and porphyry copper mineralization in collisional orogens. Journal of Petrology (in press)

Please send me your email that I can send you more examples! Kind regards Daniel

Hi Daniel, congrats for your fruitful adakite discussion.

When you say “high-K calc-alkaline rocks”, I understand that it may include crustal-derived granites (sensu stricto) and associated effusive rocks. If it is true (and you are not assuming just mantle-related high-K igneous rocks), there are many granites without the adakitic signature in the literature.

Best regards,

Felipe

Hi Felipe, thank you very much for the good discussion! Regarding your last comment, the answer is yes. The term "high-K calc-alkaline rocks" also includes monzogranites or alkaligranites. Best wishes Daniel

Ok Daniel,

Many “high–K calc–alkaline granites” (monzogranite/sienogranite) are interpreted as the melting product of low–pressure (plagioclase stable) (± garnet) crustal source of intermediate composition, such as a TTG gneisses and/or metagraywackes (e.g. Liégeois et al., 1998; Jayananda et al., 2006; Shang et al., 2010; Laurent et al., 2014; Manya and Maboko, 2016; Tulibonywa et al., 2017; Costa et al., 2018). This is also consistent with experimental melting of tonalite and/or metagraywacke that generate melt with high SiO2 (70–75 wt.%) and K2O (2–6 wt.%), and low Fe2O3+MgO (< 5 wt.%) contents (e.g. Patiño Douce, 1999; Watkins et al., 2007).

Considering Daniel’s first statement that: “Adakites are geochemically defined by high whole-rock Sr/Y and La/Yb ratios and Eu/Eu*≥1”, the above mentioned “high–K calc–alkaline granites” cannot be termed “Adakites”. They have generally low Sr/Y and La/Yb ratios, and pronounced Eu negative anomaly (Eu/Eu*3.0 Ga) depleted lower crust of intermediate composition.

Therefore, I would say that many “high–K calc–alkaline granites”, interpreted as partial melting of crustal source of intermediate composition, do not have the “Adakite” signature.

However, I do agree that “most” of mantle-derived high-K igneous rocks have the high Sr/Y and La/Yb ratios and Eu/Eu*≥1, such as the “high Ba-Sr granites and associated appinites” (e.g. Tarney and Jones, 1994; Ye et al., 2008; Perpétuo et al. 2016) and “sanukitoid suites” (e.g. Stern et al., 1991; Smithies and Champion, 1999; Halla et al., 2009).

Best regards,

Felipe

REFERENCES

Costa, F.G., Klein, E.L., Lafon, J.M., Milhoman, J.M., Galarza, M.A., Rodrigues, J.B., Naleto, J.L.C., Corrêa-Lima, R.G., 2018. Geochemistry and U-Pb-Hf zircon data for plutonic rocks at the Troia Massif, Borborema Province, NE Brazil: Evidence for reworking of Archean and juvenile Paleoproterozoic crust during Rhyacian accretionary and collisional tectonics. Precambrian Research, 311, 167–194.

Halla, J., can Hunen, J., Heilmo, E., Hottla, P., 2009. Geochemical and numerical constraints on Neoarchean plate tectonics. Precambrian Research, 175, 155–162.

Jayananda, M. Chardon, D., Peucat, J.J., Capdevila, R., 2006. 2.61 Ga potassic granites and crustal reworking in the western Dharwar craton, southern India: Tectonic, geochronologic and geochemical constraints. Precambrian Research, 150, 1–26.

Laurent, O., Martin, H., Moyen, J.F., Doucelance, R., 2014. The diversity and evolution of late–Archean granitoids: Evidence for the onset of “modern–style” plate tectonics between 3.0 and 2.5 Ga. Lithos, 205, 208–235.

Liégeois, J.P., Navez, J., Hertogen, J., Black, R., 1998. Contrasting origin of post–collisional high–K calc–alkaline and shoshonitic versus alkaline and peralkaline granitoids. The use of sliding normalization. Lithos, 45, 1–28.

Manya, S., Maboko, M.A.H., 2016. Generation of Palaeoproterozoic tonalites and associated high–K granites in southwestern Tanzania by partial melting of underplated mafic crust in an intracontinental setting: Constraints from geochemical and isotopic data. Lithos, 260, 120–133.

Patiño Douce, A.E., 1999. What do experiments tell us about the relative contributions of crust and mantle to the origin of granitic magmas? Geological Society London Special Publications, 168 (1), 55–75.

Perpétuo, M.P., Amaral, W.S., Costa, F.G., Filho, E.C.U., Sousa, D.F.M., 2016. Geochemistry of the Serra das Melancias Pluton in the Serra da Aldeia Suite: a classic post-collisional high Ba-Sr granite in The Riacho do Pontal Fold Belt, NE Brazil. Brazilian Journal of Geology, 46(2), 221-237.

Shang, C.K., Liégeois, L.P., Satir, M., Frisch, W., Nsifa, E.N., 2010. Late Archaean high-K granite geochronology of the northern metacratonic margin of the Archaean Congo craton, Southern Cameroon: Evidence for Pb-loss due to non-metamorphic causes. Gondwana Research, 18, 337-355.

Smithies, R.H., Champion, D.C., 1999. High-Mg diorite from the Archean Pilbara Craton; anorogenic magmas derived from a subduction–modified mantle. Geological Survey of Western Australia, Annual Review, 1998–1999, 45–59.

Stern, R.A., Hanson, G.N., Shirey, S.B., 1989. Petrogenesis of mantle-derived, LILE-enriched Archean monzodiorites and trachyandesites (sanukitoids) in southwestern Superior Province. Canadian Journal of Earth Sciences, 26, 1688–1712.

Tarney, J., Jones, C.E., 1994. Trace element geochemistry of orogenic igneous rocks and crustal growth models. Journal of the Geological Society, 151(5), 855-868.

Tulibonywa, T., Manya, S., Torssander, P., Maboko, M.A.H., 2017. Geochemistry of the Palaeoproterozoic volcanic and associated potassic granitic rocks of the Ngualla area of the Ubendian Belt, SW Tanzania. Journal of African Earth Sciences, 129, 291–306.

Watkins, J.M., Clemens, J.D., Treloar, P.J., 2007. Archean TTGs as sources of younger granitic magmas: melting of sodic metatonalites at c. 0.6–1.2 GPa. Contributions to Mineralogy and Petrology, 154, 91–110.

Ye, H.M., Li, X.H., Li, Z.X., Zhang, C.L., 2008. Age and origin of high Ba–Sr appinite–granites at the northwestern margin of the Tibet Plateau: Implications for early Paleozoic tectonic evolution of the Western Kunlun orogenic belt. Gondwana Research, 13, 126–138.

Here goes the attached file:

Adakites vs. Crustal Granites,

cheers,

Felipe

Sorry,

The references of Martin (1994) and Martin et al. (2005) are missing from my last replies. In addition, these are some of the most important references for the Adakite discussion.

Martin, H., 1994. The Archean grey gneiss and the genesis of continental crust. In: Condie, K.C. (ed.) The Archean Crustal Evolution, Amsterdam: Elsevier, pp. 205-259.

Martin, H., Smithies, R.H., Rapp, R., Moyen, J.–F., Champion, D., 2005. An overview of adakite, TTG and sanukitoid: relationships and some implications for crustal evolution. Lithos 79, 1–24.

Dear Felipe, many thanks for the big list of references! I must admit that I did not know all of them. However, please kindly have a look at the papers listed below which document the geochemical similarities between high-K igneous rocks and "adakites". Here they are! Enjoy!

Ahmadian J, Sarjoughian F, Lentz D, Esna-Ashari A, Murata M, Ozawa H (2016) Eocene K-rich adakitic rocks in the Central Iran: implications for evaluating its Cu–Au–Mo metallogenic potential. Ore Geology Reviews 72: 323–342

He WY, Mo X, Yang LQ, Xing YL, Dong GC, Yang Z, Gao X, Bao XS (2016) Origin of the Eocene porphyries and mafic microgranular enclaves from the Beiya porphyry Au polymetallic deposit, western Yunnan, China: implications for magma mixing/mingling and mineralization. Gondwana Research 40: 230-248

Liu D, Zhao Z, DePaolo DJ, Zhu DC, Meng FY, Shi Q, Wang Q (2017a) Potassic volcanic rocks and adakitic intrusions in southern Tibet: insights into mantle–crust interaction and mass transfer from the Indian plate. Lithos 271: 48-64

Motuza G, Šliaupa S (2017) Paleogene volcanism in central Afghanistan: possible far-field effect of the India-Eurasia collision. Journal of Asian Earth Sciences 147: 502-515

Rezeau H, Moritz R, Leuthold J, Hovakimyan S, Tayan R, Chiaradia M (2017) 30 Myr of Cenozoic magmatism along the Tethyan margin during Arabia–Eurasia accretionary orogenesis (Meghri–Ordubad pluton, southernmost Lesser Caucasus). Lithos 289: 108-124

Tang Y, Li X, Xie Y, Liu L, Lan T, Meffre S, Huang C (2017) Geochronology and geochemistry of late Jurassic adakitic intrusions and associated porphyry Mo–Cu deposit in the Tongcun area, east China: implications for metallogenesis and tectonic setting. Ore Geology Reviews 80: 289–308

Wang J, Hattori K, Liu J, Gao Y, Zhang H (2017) Shoshonitic and adakitic magmatism of the early Paleozoic age in the western Kunlun orogenic belt, NW China: implications for the early evolution of the northwestern Tibetan plateau. Lithos 287: 345-362

Chen L, Yan Z, Wang Z, Wang K (2018) Petrogenesis of early Cretaceous dioritic dykes in the Shanyang-Zhashui area, south Qinling, central China: evidence for partial melting of thickened lower continental crust. J Asian Earth Sci 158:324–335

Gao J, Klemd R, Zhu M, Wang X, Li J, Wan B, Xiao W, Zeng Q, Shen P, Sun J, Qin K, Campos E (2018) Large-scale porphyry-type mineralization in the Central Asian metallogenic domain: a review. J Asian Earth Sci (in press)

He C, Gong S, Wang L, Chen N, Santosh M, Wang Q (2018) Protracted post-collisional magmatism during plate subduction shutdown in the early Paleoproterozoic: insights from postcollisional granitoid suite in NW China. Gondwana Res 55:92–111

Richards JP, Razavi A, Spell T, Locock A, Sholeh A, Aghazadeh M (2018) Magmatic evolution and porphyry-epithermal mineralization in the Taftan volcanic complex, southeastern Iran. Ore Geol Rev 95:258–279

Sun X, Lu YJ, McCuaig TC, Zheng YY, Chang HF, Guo F, Xu LJ (2018) Miocene ultrapotassic, high-Mg dioritic and adakite-like rocks from Zhunuo in southern Tibet: implications for mantle metasomatism and porphyry copper mineralization in collisional orogens. J Petrol (in press)

Let me raise an additional point here. What do really Sr/Y and La/Yb tell us about the petrogenesis of magmas?

Elevated Sr/Y and La/Yb tell us, basically, that garnet was involved at some point during magma evolution. It doesn’t tell us whether garnet was in the source (and which source was this) or in a crustal contaminant or in the fractionating assemblage. Additionally, elevated Sr and Eu/Eu* suggest that plagioclase was not significant in the mineral residue (source or fractionated). So basically, what we call the adakitic signature is really only telling us that the main magmatic processes occurred at high pressure, that’s it.

But of course there are many different processes taking place at high pressure.

Actually, most of the Central Andean Miocene to recent magmatism could be said to be “adakitic” since significant MASH processes take place at the base of a ~65 km thick crust. Why don’t we call the Central Andes an adakitic province, then? I think it is because there are additional constraints on adakites that are often overlooked.

In their original definition of adakites, Defant and Drummond listed other chemical characteristics that would be distinctive of adakites (at least the slab-melt origin adakites). These features included elevated #Mg and depleted isotopic ratios. They were pointing to depleted and mafic to ultramafic sources, and these parameters helped to filter-out crustal melting or assimilation as a significant process. #Mg can drop easily with some mafic mineral fractionation, but the depleted isotopic signature should remain throughout magma evolution. In other words, we don´t call adakite any rock with elevated Sr/Y and La/Yb, but only those of dominantly mantle origin.

So my suggestion would be that, if we want the term “adakite” to mean anything, we should use a more refined characterization that reflects high-pressure dominated processes WITHOUT significant involvement of crustal melting.

Hi Daniel, many thanks for your excellent comments! I completely agree that the term "adakite" needs to be more clearly defined before it can be used, especially when referring to fertile magmatism related to porphyry Cu mineralization.

سلام. موضوعی که طرح فرمودین بسیار کلی هستش و در واقع سوالتون مشخص نیست!!! یا حداقل ما متوجه سوالتون نشددیم

Hi Daniel, actually I want to express the differentiation in terms of adakites and non-adakite rocks. Adakites basically comprise higher Sr/Y and Eu/Eu* ratios relative to non-adakitic nature of rocks. These ratios can be significant to identify rocks of adakitic and non-adakitic character predominantly for those which experience hydrothermal alteration and do not sustain original Sr/Y ratios. However, in my view, this term is only used in context of magmatic deposits rather than hydrothermal. In my opinion, use of this term in hydrothermal system probably leads to wrong interpretation. For instance, in case of magmatic apatite, adakite term is commonly used (Pan et al., 2016; Chen et al., 2017) rather than hydrothermal apatite.

Due to the calc-alkaline and shoshonitic intrusions are also characterized by high whole-rock LILE such as K, high Sr/Y and La/Yb ratios, elevated LREE,

You are right and I like your definition

Thanks to Daniel Sellés and Felipe Grandjean Costa for their replies, and Daniel Müller for putting this topic into discussion.

I just want to add that I didn't know all the literature about the topic, specially those related to ore - deposit forming magmas. However, during my research I had investigated less-differentiated magmas that, pressumible should show "adakite-like signature" (formed >40 km depth), and has mid- to - upper crustal related signatures (associated to REE ratios). Thus, garnet involvement is not recognized in a thick continental crust (such as the Central Andean) which we are now investigating why).

Cheers

The Adakite has been used genetically to imply slab melting (Drummond and Defant). Unfortunately any rock with a garnet signature, resulting in high La/Yb and Sr/Y ratios and low HREE (an Y) have been termed as adakite or adakitic.

If the rocks have residual garnet signatures only (i.e., in the mantle wedge or subducting slab) then it should be termed as adakite, otherwise he term adakite should not be used.

In introduction of my thesis considering adakitic plutonic rocks in Finland (Ruotoistenmäki, 2019), I write (see references from my thesis*):

...

“...From the considerations above, it becomes clear that the genetic link of adakites and adakitic rocks, including TTGs and sanukitoids, to slab melting is ambiguous. Castillo (2006) noted that the adakite studies have generated confusion because the definition of adakite combines compositional criteria with genetic interpretation. Moyen (2011) emphasized the loose definition of the term TTG in the literature. Therefore, in this study, the terms ‘adakitic’ or ‘adakitoid’ are used to refer to plutonic rocks having adakitic characteristics and apparently lower crust/upper mantle fractionation depths.”...

And cover text:

...

“This study considers the adakitic plutonic rocks, or ‘adakitoids’, representing melts fractionated below plagioclase stability depths in the lower crust/upper mantle (greater or equal to ca. 50–80 km). They cover a substantial fraction of the Finnish Precambrian bedrock. Only some supracrustal sub-areas lack adakitic plutonic rock outcrops. The study provides a summary of Finnish adakitoids: their areal, chemical, isotopic (age) and physical variations and their tectonic and magmatic evolution. It is shown that adakitoids constitute a distinct chemically defined rock group that overlaps groups defined by ‘traditional’ mineralogical and chemical methods. The adakitic plutonic rocks vary from granodiorites to tonalites and gabbros. The Proterozoic adakitoids are generally connected with ‘modern type’ plate tectonic processes, while the majority of Archaean crust and adakitoids (TTGs) are primarily connected with collision, stacking and over-/underthrusting of inferred pre-existing microplates. The adakitoids form a continuity from 'true', subduction-related adakites to TTGs and sanukitoids, their chemical and mineralogical differences being obscure. As such, they give a very valuable and informative window into magmatic processes existing at upper mantle/lower crustal depths...”

*)Ruotoistenmäki, T. 2019. Adakitic plutonic rocks in the Finnish Precambrian: Evolution and areal, chemical, physical and age variations. Academic Dissertation. Geological Survey of Finland, Espoo. 146 pages, 97 figures and 15 tables. Available in:

https://www.researchgate.net/publication/329539286_Adakitic_plutonic_rocks_in_the_Finnish_Precambrian_Evolution_and_areal_chemical_physical_and_age_variation

See Moyen (2009). High Sr/Y and La/Yb ratios: The meaning of the “adakitic signature”

Dear Daniel,

Please, read this article: Article Trace element geochemistry of the 1991 Mt. Pinatubo silicic ...

where we suggest that intrusives having adakitic signatures are genetically associated with Au–Cu and Cu–Mo mineralization, auriferous porphyry copper deposits, and epithermal gold veins. The slab-derived fluids carrying mobile elements are likely responsible for the enrichment of adakite magmas in gold, associated metals and H2O, and may explain the exceptional ore-forming potential of adakite magmatism.

sincerely,

Anastassia

A Pakistani geologist described adakites as under:

Large porphyry Cu-Au deposits are associated with Early Miocene intrusive rocks in Tethyan belt, discovered along Chagai magmatic arc in Western Pakistan, adjacent to Southeast Iran. Two types of rocks were discriminated as granodiorite and monzodiorite from Saindak area. The granodiorites are associated with regional large Cu-Au ineralization,while themonzodiorites aremostly ore-barren. LAICP- MS U-Pb dating yielded weightedmean 206Pb/238U ages of 22.16–24.2 Ma for granodiorites and ca. 22.6 Ma for a monzodiorite. These intrusive rocks in the Saindak area are all calc-alkaline rocks, with enriched LILEs and depleted HFSEs, and without Eu negative anomalies. The felsic ranodiorites are characterized by high Sr contents and Sr/Y ratios, with intermediate to high (La/Yb)N ratios that identify themas typical high-silica adakites. In contrast, the basaltic-andesiticmonzodiorites are just normal arcrelated rocks, showing less actionated REE patterns than the granodiorites, with systematically lower LREE and higher MREE and HREE. Low K2O/Na2O ratios and decoupled Sr/Y-(La/Yb)N ratios indicate the characteristics of slab-derived adakites for the granodiorites, most likely originated through partial melting of the subducted Neotethys oceanic crust beneath Eurasian continent followed by subsequent mantle interaction. The almost imultaneously melting of subcontinental lithospheric mantle induced by dehydration of Neotethys plate gave rise to the formation of the barren monzodiorites. These intrusive rocks in the Saindak area are characterized by similar Sr-Nd-Pb isotopes with high 87Sr/86Sri ratios, slightly negative εNd(t) values and radiogenic Pb isotopes, plotting in the field between the MORB and EM-II mantle endmembers or the Average Cadomian Lower Crust, suggesting subducting sediments or old continental crustal materials have contributed into the compositions of these rocks by source enrichment or crustal contamination. The slab-melting derived adakite is favourable for regional massive Cu-Au mineralization in the Saindak area.

Regards

Ijaz