Combined dikes (mingling dikes) of Western Sangilen (southeastern Tuva) are believed to indicate a shift from the tectonic contraction mode related to the mountain fold system formation, to a postcollisional extension that ended in the disintegration of the collisional orogen. However, the combined dikes position in the general sequence of magmatic events was based only on their geological location and hasn't been confirmed with U/Pb isotope-geochronological determinations. The proposed study is concerned with the geological structure, the composition and defining the isotopic age of the Western Sangilen combined dikes, which lies in the range of 485-490 Ma. The isotopic age of host granites from the Matut pluton is 509 Ma; moreover, the thermal events of Riphean (679-934 Ma) and early Paleozoic age (484 Ma) were detected in zircons from the gneiss-granites of the Erzin metamorphic complex. The obtained data are consistent with earlier determined sequences of Western Sangilen tectonic-metamorphic events. Basites from the examined combined dikes are drastically different by the composition of the indicator elements (Rb, Nb, Ta, Zr, Hf), and the ratios of Nb/Y, Zr/Y, Th/Ta, Zr/Nb, Nb/Th, which are the indicatives of diversified mantle sources probably from various depths. The protolith of the salic part of these combined dikes might have been rocks with a composition similar to the autochthonous/parautochthonous gneiss-granites of the Erzin metamorphic complex.
|Журнал||Russian Geology and Geophysics|
|Состояние||Опубликовано - 1 янв 2019|