Charnockites and charnockites

Zircon U–Pb–Hf isotopes and geochemistry of two contrasting Neoarchean charnockitic rock series in Eastern Hebei, North China Craton: Implications for petrogenesis and tectonic setting

“…Combining petrographic features with in situ trace element analyses of the coarse grained subhedral orthopyroxenes from samples of the charnockite series, we suggest that these coarse grained subhedral orthopyroxenes were directly crystallized from magmatic precursors. These petrographic and chemical characteristics for the orthopyroxenes suggest that the charnockitic plagioclase gneiss series belong to the metamorphic type, whereas the charnockite series belong to the magmatic type according to the previous classification by Frost and Frost (2008) and Rajesh and Santosh (2012). This classification is only based on orthopyroxene origins, and in fact, the two contrasting charnockitic rock series both originated from plutonic igneous rock associations, and then they were metamorphosed in a granulite-facies condition.…”

“…These rocks can be classified into the following: (1) magmatic type, containing orthopyroxenes crystallized directly from anhydrous magmas, and (2) metamorphic type, the orthopyroxenes of which originate from CO 2 -rich fluids related granulite-facies metamorphic dehydration reactions, involving the breakdown of hornblende or biotite (Frost and Frost, 2008;Rajesh and Santosh, 2012). Metamorphic charnockitic rocks are usually distributed as strongly foliated units inside amphibolite-facies gneiss regions, and have been called "incipient charnockite" (Pichamuthu, 1960).…”

Rb–Sr and Sm–Nd study of granite–charnockite association in the Pudukkottai region and the link between metamorphism and magmatism in the Madurai Block

“…These are migmatized at several places within the Madurai Block. The western part of the Madurai Block, however, comprises several highlands which are generally charnockite massifs that are shown to be intrusions within the grey gneisses based on the presence of large inclusions of metapelites and calc-silicates (Rajesh et al 2011;Rajesh 2012). In the eastern part, though, the charnockites occur as enclaves within the biotite gneisses, and are also intimately associated with the intrusive K-feldspar rich granites which have plenty of coarse garnet grains.…”

High- to ultrahigh-temperature metasomatism related to brine infiltration in the Neoarchean Limpopo Complex: Petrology and phase equilibrium modeling

“…Fine-grained (0.1-0.2 mm) quartz, plagioclase, and K-feldspar are scattered along the grain boundaries of the coarsegrained quartz and meso/antiperthite, possibly formed by localized shear deformation. Thin (<0.1 mm) film of K-feldspar around antiperthite and garnet grains might suggest the presence of melt phase (e.g., Touret and Huizenga, 2012) or high-temperature metasomatism by infiltration of low aH 2 O fluid (e.g., Harlov et al, 1998;Rajesh and Santosh, 2012).…”

“…Although infiltration of aqueous fluid into quartzo-feldspathic rocks at such high-temperature conditions might give rise to significant partial melting, barium content of thin K-feldspar films around garnet and antiperthite is very low (<0.3 wt.% BaO), suggesting that the K-feldspar film could have been formed by high-temperature metasomatism by infiltration of low aH 2 O fluid (e.g., Harlov et al, 1998;Rajesh and Santosh, 2012). We have thus no evidence of extensive melting related to the metasomatic alteration possibly because of high salinity in the infiltrated fluid, which Please cite this article in press as: Tsunogae, T., van Reenen, D.D., High-to ultrahigh-temperature metasomatism related to brine infiltration in the Neoarchean Limpopo Complex: Petrology and phase equilibrium modeling.…”