Melt- to shear-controlled exhumation of granulites in granite-gneiss domes: Petrological perspectives from metapelite of the Neoarchean Ha-Tshanzi structure, Central Zone, Limpopo Complex, South Africa

Safonov, O.G.; Yapaskurt, V.O.; Elburg, M.A.; van Reenen, D.D.; Rajesh, H.M.; Smit, C.A.; Perchuk, A.L.; Butvina, V.G.

Авторы: Safonov O.G., Yapaskurt V.O., Elburg M.A., van Reenen D.D., Rajesh H.M., Smit C.A., Perchuk A.L., Butvina V.G.
Журнал: Journal of Petrology
Том: 62
Номер: 12
Год издания: 2021
Издательство: Oxford University Press
Местоположение издательства: United Kingdom
Первая страница: 1
Последняя страница: 26
DOI: 10.1093/petrology/egab097
Аннотация: Gneiss domes cored by migmatites and granites represent the principal role of anatectic meltsduring the exhumation of high-grade metamorphic complexes. This study explores the exhumationhistory of a metapelitic granulite within the Ha-Tshanzi structure from the Central Zone of theNeoarchean–Paleoproterozoic Limpopo high-grade Complex, South Africa. Quartzofeldspathicgarnet-bearing coarse-grained leucosomes in the rock alternate with attenuated shear bandsconsisting of biotite, cordierite, sillimanite and quartz that prominently modified the earlier garnetporphyroblasts. Cores of garnet porphyroblasts contain various polyphase inclusions that areinterpreted as crystallized inclusions of melt. The phase equilibria modeling and regular zoningof garnet with respect to major (Mg, Fe, Ca) and some trace (P, Cr, Sc) elements reveals thata garnet + biotite + plagioclase + quartz ± sillimanite assemblage in the rock coexisted withthe melt during the sub-isothermal (810–830 ◦C) exhumation from pressure of 10·0–10·2 kbar to7·5–7·0 kbar during the Neoarchean event (2·68–2·62 Ga). The exhumation mediated by anatecticmelt supports interpretation of the Ha-Tshanzi structure as a diapir-related granite–gneiss dome.During upwelling of the dome, the melt segregated into leucosome, while growth of cordieritesequestered water from the melt, assisting its crystallization at the end of the sub-isothermaldecompression stage. As the rheology of the rock changed, melt-dominated deformation wastransformed to solid-dominated ductile shear deformation. In contrast to the earlier sub-isothermaldecompression P–T path, the gentler slope of ∼75 ◦C kbar–1 of the decompression-cooling pathmarks the exhumation from pressures of ∼7 kbar to pressures of 5–4·5 kbar and cooling to 600–550 ◦C. Dating of zircon, monazite and rutile shows that the Neoarchean evolution of the metapelitewas strongly overprinted by the Paleoproterozoic event at c. 2·01 Ga. The results of the studyhighlight the significance of domed structures related to granitic diapirs in the exhumation of theCentral Zone of the Limpopo Complex.
Добавил в систему: Сафонов Олег Геннадьевич

	ИСТИНА	Войти в систему Регистрация
	ИПМех РАН
	Главная Поиск Статистика О проекте Помощь

ИСТИНА

ИПМех РАН

Melt- to shear-controlled exhumation of granulites in granite-gneiss domes: Petrological perspectives from metapelite of the Neoarchean Ha-Tshanzi structure, Central Zone, Limpopo Complex, South Africaстатья

Прикрепленные файлы