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Fluid-assisted interaction of peraluminous metapelites withtrondhjemitic magma within the Petronella shear-zone, Limpopo Complex, South Africaстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 24 декабря 2014 г.
- Авторы: Safonov Oleg G., Tatarinova Daria S., van Reenen Dirk D., Golunova Maria A., Yapaskurt Vasily O.
- Журнал: Precambrian Research
- Том: 253
- Год издания: 2014
- Издательство: Elsevier BV
- Местоположение издательства: Netherlands
- Первая страница: 114
- Последняя страница: 145
- Аннотация: The principal problem concerning the evolution of Precambrian granulite complexes located betweengranite-greenstone cratons is their interaction with the underthrusted greenstone belts during exhuma-tion from the lower crust. Besides evidence for pervasive and localized fluid fluxes arising fromdevolatilization of the greenschist and amphibolite-facies rocks in the course of their burial under-neath the granulites, this interaction might also be expressed in formation of diverse magmas ofgranitic, trondhjemitic and granodioritic composition. We present results of a petrological, fluid inclusionand thermobarometric study of interaction between fluidized trondhjemitic magma and peraluminousmetapelitic granulites associated with the regional high-grade Petronella shear zone located in theSouthern Marginal Zone (SMZ) of the Limpopo Granulite Complex (South Africa). The hot (T ∼ 1000◦C)trondhjemitic magma, which, presumably, originated from partial melting of a basaltic (amphibolite)material at the base of the granulite complex or at the top of the underthrusted greenstone blocks,intruded granulites at P ∼ 8.0–9.5 kbar (24–28 km depth) at 2.667 ± 0.9 Ga during the exhumation of theSMZ. The magma heated and assimilated orthopyroxene-cordierite metapelites and dragged them toa depth of 18–20 km (6.3–6.5 kbar). The magma was heterogeneously saturated with MgO, FeO, Al2O3by the dissolved metapelites. This process provoked crystallization of several garnet generations fromthe trondhjemitic melt. Various mineral assemblages included in the different generations of garnetallowed application of TWQ method combined with PERPLE X pseudo sections to trace sub-isobariccooling of the magma from T ∼ 900–600◦C at 5.5–6.5 kbar. The isobaric cooling also affected the asso-ciated metapelites. Fluid inclusions trapped in garnet and quartz in the trondhjemite show that themagma transported carbonic fluid with densities corresponding to the late stages of magma cooling(600–650◦C and 5.5–6.5 kbar). Carbonic fluids coexisted with aqueous-salt fluids (preserved as inclusionswith salinity up to 20.58 wt.% NaCl eq.). These low water activity fluids (aH2O< 0.3) bearing Na, K andCa salts, being exsolved from the magma on cooling and solidification, provoked formation of complexNa-gedrite + biotite + sillimanite + quartz ± staurolite ± plagioclase-bearing assemblages after cordieritein metapelites at temperatures 630–570◦C and pressures 5.5–6.5 kbar. These data provide evidence thathot trondhjemitic melts played a critical role in the exhumation of granulites onto the adjacent granite-greenstone craton. The trondhjemite transferred heat from the lower to the middle crust and transportedlarge volumes of external aqueous-carbonic-salt fluids that participated in the rehydration of a significantportion of the SMZ.
- Добавил в систему: Япаскурт Василий Олегович