Experimental melts from crustal rocks: A lithochemical constraint on granite petrogenesis

Gao, Peng; Zheng, Yong‐Fei; Zhao, Zi‐Fu

doi:10.1016/j.lithos.2016.10.005

Cited by 207 publications

(72 citation statements)

References 141 publications

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“…The evolution of melt compositions from upper amphibolite to granulite facies is consistent with experimental studies which suggest that temperature controls the FeO + MgO and CaO of the melts (Gao, Zheng, & Zhao, 2016;Johannes & Holtz, 1996;Montel & Vielzeuf, 1997). A marked decrease in K 2 O is expected in melts produced at P-T conditions approaching those of the biotite-out curves, where the last remnants of biotite participate in melting reactions to form K-feldspar, and the amount of melt rapidly increases (Figure 11b; see also figure 4 in Bartoli, 2018).…”

Section: New Clues On Anatexis Of the Ivrea Zonesupporting

confidence: 87%

Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)

Carvalho

Bartoli

Ferri

et al. 2018

Journal Metamorphic Geology

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We investigate the inclusions hosted in peritectic garnet from metapelitic migmatites of the Kinzigite Formation (Ivrea Zone, NW Italy) to evaluate the starting composition of the anatectic melt and fluid regime during anatexis throughout the upper amphibolite facies, transition, and granulite facies zones. Inclusions have negative crystal shapes, sizes from 2 to 10 μm and are regularly distributed in the core of the garnet. Microstructural and micro‐Raman investigations indicate the presence of two types of inclusions: crystallized silicate melt inclusions (i.e., nanogranitoids, NI), and fluid inclusions (FI). Microstructural evidence suggests that FI and NI coexist in the same cluster and are primary (i.e., were trapped simultaneously during garnet growth). FI have similar compositions in the three zones and comprise variable proportions of CO2, CH4, and N2, commonly with siderite, pyrophyllite, and kaolinite, suggesting a COHN composition of the trapped fluid. The mineral assemblage in the NI contains K‐feldspar, plagioclase, quartz, biotite, muscovite, chlorite, graphite and, rarely, calcite. Polymorphs such as kumdykolite, cristobalite, tridymite, and less commonly kokchetavite, were also found. Rehomogenized NI from the different zones show that all the melts are leucogranitic but have slightly different compositions. In samples from the upper amphibolite facies, melts are less mafic (FeO + MgO = 2.0–3.4 wt%), contain 860–1700 ppm CO2 and reach the highest H2O contents (6.5–10 wt%). In the transition zone melts have intermediate H2O (4.8–8.5 wt%), CO2 (457–1534 ppm) and maficity (FeO + MgO = 2.3–3.9 wt%). In contrast, melts at granulite facies reach highest CaO, FeO + MgO (3.2–4.7 wt%), and CO2 (up to 2,400 ppm), with H2O contents comparable (5.4–8.3 wt%) to the other two zones. Our results represent the first clear evidence for carbonic fluid‐present melting in the Ivrea Zone. Anatexis of metapelites occurred through muscovite and biotite breakdown melting in the presence of a COH fluid, in a situation of fluid–melt immiscibility. The fluid is assumed to have been internally derived, produced initially by devolatilization of hydrous silicates in the graphitic protolith, then as a result of oxidation of carbon by consumption of Fe3+‐bearing biotite during melting. Variations in the compositions of the melts are interpreted to result from higher T of melting. The H2O contents of the melts throughout the three zones are higher than usually assumed for initial H2O contents of anatectic melts. The CO2 contents are highest at granulite facies, and show that carbon‐contents of crustal magmas are not negligible at high T. The activity of H2O of the fluid dissolved in granitic melts decreases with increasing metamorphic grade. Carbonic fluid‐present melting of the deep continental crust represents, together with hydrate‐breakdown melting reactions, an important process in the origin of crustal anatectic granitoids.

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Section: New Clues On Anatexis Of the Ivrea Zonesupporting

confidence: 87%

Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)

Carvalho

Bartoli

Ferri

et al. 2018

Journal Metamorphic Geology

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“…Loiselle and Wones () introduced “A‐type (alkaline‐anhydrous‐anorogenic type) granites” as a new category of felsic melts. Various petrogenetic models including fractionation from transitional to alkaline mantle‐derived mafic and intermediate magmas (Bonin, ; Turner, Foden, & Morrison, ), mixing of OIB and crustal sources (Eby, ; Eby, ) and partial melting of crustal rocks (Collins, Beams, White, & Chappell, ; Creaser, Price, & Wormald, ; P. Gao, Zheng, & Zhao, ; R. F. Martin, ; Skjerlie & Johnston, ), have been proposed for the origin of A‐type granitoids.…”

Section: Discussionmentioning

confidence: 99%

Early Palaeozoic accretionary tectonics of West Kunlun Orogen: Insights from Datong granitoids, mafic–ultramafic complexes, and Silurian–Devonian sandstones, Xinjiang, NW China

Xiao

Tian

2018

Geological Journal

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The Datong area is located in the western part of the Western Kunlun Orogen (WKO), occupying a key area of the Tethyan domain. Our new SHRIMP U–Pb zircon ages from the Datong area provide new information about the Palaeozoic evolution of the Western Kunlun Orogen. A 473.0 ± 2.8 Ma granite with 493.6 ± 4.8 Ma inherited zircons from the Kusilafu extrusive rocks is interpretation as an A‐type granite formed in a fore‐arc tectonic setting. The 485.5 ± 1.9 Ma granitoid of the Datongdong pluton combined with the 452.7 ± 7 Ma granitoid of the Datong pluton indicate that the Datong pluton is an intra‐oceanic arc complex formed by the southern subduction of the Proto‐Tethyan ocean crust. Zircons from gabbros of the Datong mafic–ultramafic complex have a 499.2 ± 2.1 Ma U–Pb crystallization age. Combined with its complicated whole‐rock geochemistry, we propose that there may have existed a Datong seamount in the early Palaeozoic. The detrital zircon results of Silurian–Devonian sandstones reveal that the Late Silurian sandstones have the characteristic zircons both from the Tarim Block and Datong Arc, suggesting that the Datong arc collided with the Tarim Block in the Late Silurian. The tectonic history of the WKO was characterized by a southern subduction of Proto‐Tethys terminated in the Late Silurian.

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“…Plot of MgO vs. SiO 2 for mafic lower‐crustal xenoliths from early Mesozoic plutons in the northern part of the NCC. Data sources: lower‐crustal xenoliths are from Shao, Han and Li (), Shao, Zhang, She and Liu () and this study; experimental melts from crustal rocks are compiled from Gao, Zheng and Zhao ()…”

Section: Discussionmentioning

confidence: 99%

Phanerozoic magma underplating and crustal growth beneath the North China Craton

Zheng

et al. 2017

Terra Nova

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Evidence for post‐Archaean crustal growth via magma underplating is largely based on U–Pb dating of zircons from granulite‐facies xenoliths. However, whether the young zircons from such xenoliths are genetically related to magma underplating or to anatexis remains controversial. The lower‐crustal xenoliths carried by igneous rocks in the Chifeng and Ningcheng (North China Craton) have low SiO2 and high MgO, indicating that parental melts of their protoliths were of unambiguous mantle origin. The xenoliths contain abundant magmatic zircons with late‐Palaeozoic ages, and have more radiogenic zircon Hf‐isotope compositions and hence younger model ages than ancient crustal magmas and the “reworking array” of the basement rocks. Our data suggest that the granulites represent episodic magmatic underplating to the lower crust of this craton in Phanerozoic time. Considering the observation that regional lowermost crust (~5 km) is mafic and characterized by Phanerozoic zircons, this work reports an example of post‐Archaean crustal growth via magma underplating.

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Experimental melts from crustal rocks: A lithochemical constraint on granite petrogenesis

Cited by 207 publications

References 141 publications

Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)

Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)

Early Palaeozoic accretionary tectonics of West Kunlun Orogen: Insights from Datong granitoids, mafic–ultramafic complexes, and Silurian–Devonian sandstones, Xinjiang, NW China

Phanerozoic magma underplating and crustal growth beneath the North China Craton

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