Geological,petrologic, isotopic,and geochemical constraints of geodynamic models simulating formation of the archean tonalite-trondhjemite-granodiorite associations in ancient cratons |
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Authors: | A B Vrevsky S B Lobach-Zhuchenko V P Chekulaev A V Kovalenko N A Arestova |
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Institution: | 1.Institute of Precambrian Geology and Geochronology,Russian Academy of Sciences,St. Petersburg,Russia |
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Abstract: | The geological setting, geochemistry, and Nd isotopic systematics of tonalite-trondhjemite-granodiortite (TTG) series in ancient
cratons are considered. It is shown that the TTG series were formed from ∼4.2 to 2.6 Ga ago in the oldest continental cores;
many TTG series do not reveal chronological links to greenstone belts. This follows from the evolution of the Slave Craton
in the Canadian Shield, the Vodlozero Craton in the Baltic Shield, and the Pilbara and Yilgarn cratons in the Australian Shield,
where greenstone associations postdated TTG series. As has been established at the Baltic Shield, the primary melts of the
Mesoarchean TTG associations were formed at a shallower depth (P < 15 kbar) compared to the Neoarchean TTG, likely, due to the increasing thickness of the continental crust beneath the Baltic
Shield over time. |
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