TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

Jagoutz, Oliver; Schmidt, Max W.; Enggist, Andreas; Burg, Jean‐Pierre; Dawood, Hamid; Hussain, Shahid

doi:10.1007/s00410-013-0911-4

Cited by 62 publications

(16 citation statements)

References 74 publications

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“…It is now widely accepted that the early continental crust (mostly TTG series) was formed by melting of basaltic lithologies, leaving behind amphibolite, garnet‐amphibolite, or eclogite residues (Foley et al, ; Hastie et al, ; Johnson et al, ; Moyen, ; Nagel et al, ; Polat et al, ; Qian & Hermann, ; Rapp et al, ). It is also argued that Archean TTG gneisses can be formed by extensive fractional crystallization from a mafic precursor (Dessimoz et al, ; Jagoutz et al, ; Kamber et al, ; Kleinhanns et al, ). Such a process, however, has not seriously been considered in the past studies simply because the corresponding mafic‐ultramafic residue cumulates left during the fractional process are not evident in nature.…”

Section: Discussionmentioning

confidence: 99%

“…On the basis of the experimental results of Müntener et al (), Kleinhanns et al () concluded that hydrous melts, which underwent extensive fractional crystallization of garnet/amphibole, pyroxenes, and minor plagioclase, could evolve to TTG‐like melts. Field observation and geochemical analyses of Jagoutz et al () indicate that some TTG‐like granitoids in the Kohistan arc can form by hydrous high‐pressure differentiation of primitive arc magmas in subduction zones. Similar conclusions were also reached from the exposed lower crust in the Chelan Complex.…”

Section: Discussionmentioning

confidence: 99%

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Generation of Archaean TTG Gneisses Through Amphibole‐Dominated Fractionation

Liou

Guo

2019

JGR Solid Earth

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The early continental crust is characterized by the tonalite-trondhjemite-granodiorite gneisses (TTG) of Archaean terrains. There is a consensus that TTGs were formed by partial melting of hydrated mafic rocks. High-pressure melts tend to be more trondhjemitic with higher Sr/Y ratios due to the presence of garnet and absence of plagioclase, whereas low-pressure melts are more tonalitic with relatively lower Sr/Y ratios. Here we present a geochemical study of diorites, TTGs, and hornblendites from Eastern Hebei, North China Craton. Geochemical analyses show that dioritic parental magmas may evolve to tonalites and trondhjemites through a maximum of 27% fractional crystallization of amphibole and apatite. We also identified the cumulate apatite-bearing hornblendite, a predicted solid fractionate and chemical complement to the TTGs. Mixing of the trondhjemite and the hornblendite can generate similar chemical compositions to the diorites in this region. The mixing trends are consistent with those predicted for fractional crystallization. Based on these analyses, we conclude that these trondhjemites and tonalites can be formed by fractional crystallization of amphiboles and accessory minerals from the calc-alkaline diorites. Partial melting is not a unique solution to the problem of how to form the Archean TTG gneisses and how to make an Archean continent. Thick crust or lithosphere (in the garnet stability field) is also not a unique requirement. Amphibole fractionation may also cause an abrupt increase of Eu/Eu* of Archean granitoids at 3.2-3.0 Ga, which may be linked to a transition period in tectonic style at~3 Ga in Earth's evolution.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Generation of Archaean TTG Gneisses Through Amphibole‐Dominated Fractionation

Liou

Guo

2019

JGR Solid Earth

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“…For example, it is the standard model for granitic magmatism in the Andes (e.g., Hildreth and Moorbath, 1988;Kay and Mahlburg-Kay, 1991;Petford et al, 2000;Otamendi et al, 2009;Goss et al, 2011), as well as for ancient island arcs such as those exposed in crustal sections in Pakistan (Jagoutz, 2010;Jagoutz et al, 2011Jagoutz et al, , 2013. There is also growing support for the generation of Archean TTG in such a setting (e.g., Polat et al, 2002;Nagel et al, 2012;Polat, 2012).…”

Section: Generation Of Granitic Magmas In Subduction Zonesmentioning

confidence: 99%

“…Atherton and Petford (1993) identified such granitoids in the Andes some twenty years ago and Jagoutz et al (2013) recently did the same in the Kohistan island arc.…”

Section: Generation Of Granitic Magmas In Subduction Zonesmentioning

confidence: 99%

“…(1) in oceanic crust within subducting slabs which, when young and hot, may melt directly to form adaktic magmas (Martin, 1987;Defant and Drummond, 1990) (2) at the bases of piles of basalt in settings that range from thick Archean oceanic crust (de Wit and Hart, 1993;Rollinson, 2010), oceanic plateaus (Bédard, 2006) to the lower parts of island arcs or convergent margins (Kay and Mahlburg-Kay, 1991;Thompson et al, 2002;Jagoutz et al, 2013).…”

Section: Historical Background-development Of Ideas On the Generationmentioning

confidence: 99%

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Formation and Evolution of the Continental Crust

Arndt¹

2013

GeochemPersp

233

117

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Formation and composition of the Late Cretaceous Gangdese arc lower crust in southern Tibet

Guo

Jagoutz

Shinevar

et al. 2020

Contrib Mineral Petrol

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Arc lower crust plays a critical role in processing mantle-derived basaltic melts into the intermediate continental crust, yet can only be studied indirectly or in exposed arc sections. Compared with the relatively well-studied oceanic arc sections (e.g., Kohistan and Talkeetna), the composition and formation mechanisms of continental arc lower crust remain less clear. Here we present a geochronological and geochemical study on the Lilong Complex and the Wolong granitoids from the Gangdese arc deep crustal section in southern Tibet. The Lilong Complex is composed of the early (85-95 Ma) mafic-intermediate sequence and late (85-86 Ma) ultramafic sequence. The Lilong crustal section exposed crustal depth extending from ~42-17 km based on the geobarometry. The maficintermediate sequence is a damp (low H2O) igneous differentiation sequence characterized by the subsequent appearance of pyroxene → plagioclase → amphibole → biotite. The ultramafic sequence represents a wet igneous differentiation sequence composed of olivine → pyroxene → amphibole → plagioclase. The 74-84 Ma Wolong granitoids were formed by fractional crystallization of wet magma and intra-crustal assimilation. Calculated seismic properties of the Gangdese deep arc crust are comparable to the average continental crust at similar depth.The average composition of the Gangdese arc lower crust is basaltic andesite with SiO2 of ~54 wt%. The highly incompatible elements in the Gangdese arc lower crust are systematically higher than those of the oceanic arc and are comparable with the estimates of lower continental crust, suggesting continental arc magmatism significantly contributes to the formation of continental crust.

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TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

Cited by 62 publications

References 74 publications

Generation of Archaean TTG Gneisses Through Amphibole‐Dominated Fractionation

Generation of Archaean TTG Gneisses Through Amphibole‐Dominated Fractionation

Formation and Evolution of the Continental Crust

Formation and composition of the Late Cretaceous Gangdese arc lower crust in southern Tibet

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