Contrasting fertility of metapelite vs diorite gneiss to produce leucogranite melts: Example from the Mahalapye Complex, eastern Botswana

Rajesh, H.M.; Safonov, O.G.; Belyanin, G.A.; Vorster, C.

Авторы: Rajesh H.M., Safonov O.G., Belyanin G.A., Vorster C.
Журнал: Journal of African Earth Sciences
Том: 187
Год издания: 2022
Издательство: Pergamon Press Ltd.
Местоположение издательства: United Kingdom
Номер статьи: 104454
DOI: 10.1016/j.jafrearsci.2022.104454
Аннотация: High-grade terranes showing multiple episodes of leucogranite magmatism are ideal to assess the fertility ofcrustal protoliths. Two episodes of Paleoproterozoic leucogranite magmatism occur in the Mahalapye Complexhigh-grade terrane, at the northern edge of the Kaapvaal Craton. The older one (leucogranite 1) at ~2.05 Garepresented by leucosomes, thin veins and dykes is related to the melting of ~2.06 Ga biotite-bearing dioritegneiss. In comparison, the younger episode (leucogranite 2) at ~2.03 Ga forms massive bodies. Leucogranite 1 isassociated with the migmatitic diorite gneiss and crosscut by the ~2.04 Ga granodiorite. Leucogranite 2 containsxenoliths of diorite gneiss and granodiorite, as well as inclusions of quartz-poor and quartz-rich metapelites (Bt+ Crd + Pl + Kfs + Spl ± Sil ± Grt + Ilm + Qz). Phase equilibria modelling of a representative quartz-poormetapelite indicate that its partial melting occurred at ~810 ◦C and ~4.8 kbar in the presence of aqueousfluid. The peraluminous, ferroan and alkalic composition of the predicted melt is comparable to the chemistry ofleucogranite 2. The larger volume of anatectic melt for the estimated P-T condition corresponds to the occurrenceof leucogranite 2 as massive bodies. The lower temperature of in-situ anatexis (<750 ◦C) at a deeper level (~7.3kbar) and lack of additional fluid, likely did not generate significant melt fraction during the formation ofleucogranite 1. The contrast in the fertility of the two protoliths with respect to production of leucogranite meltswas also related to different setting of melting. Melting of diorite gneiss is related to the local influence of maficdykes and sills, whereas melting of metapelite is related to regional collision. It follows that high pressures,water-deficient regimes and localized heat sources produce limited volumes of partial melt, whereas hightemperatures, fluid-present regimes and a large-scale heat source produces higher volumes of melts.
Добавил в систему: Сафонов Олег Геннадьевич

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

ИСТИНА

ИСТИНА ИНХС РАН

Contrasting fertility of metapelite vs diorite gneiss to produce leucogranite melts: Example from the Mahalapye Complex, eastern Botswanaстатья

Прикрепленные файлы