| Инд. авторы: | Tran T.-H., Polyakov G.V., Tran T.-A., Borisenko A.S., Izokh A.E., Balykin P.A., Ngo T.-P., Pham T.-D. |
| Библ. ссылка: | Tran T.-H., Polyakov G.V., Tran T.-A., Borisenko A.S., Izokh A.E., Balykin P.A., Ngo T.-P., Pham T.-D. Permian - Triassic magmatic activity in the song Da structure // Modern Approaches in Solid Earth Sciences. - 2016. - Vol.11. - P.17-58. |
| Реферат: | eng: Late Permian mafic-ultramafic volcanic and sub-volcanic rocks in the Song Ða Rift include four different associations in terms of low-Ti and high-Ti types. Low-Ti, high-Mg volcanic and sub-volcanic rocks are composed of komatiite, komatiitic basalt and basalt and are divided into three groups according to their petrological and geochemical features. Chemical composition of rocks of the komatiite-basalt association is alkali-low (but rather Na-high), very Ti-low, varying from Al-high komatiite to Al-low basalt. They are characterized by high content of Mg, Al, Ni, Co, Cu and Cr, and low of Ti, Fe, Na, K, P, Rb, Ba, Sr, Nb, Ta, Nd, Hf, Zr and REE. In general, based on geochemical and isotopic characteristics the Song Ða mafic-ultramafic rocks of the komatiite-basalt association may be products of a melt derived from depleted mantle suffering the impact of mantle plume. Digital modeling showed that the initial melt composition was correspondent to komatiitic basalt. Eruption ages of the magmas are 257 ± 24 Ma (by Rb/Sr age dating), and 270 ± 21 Ma (by Re/Os age dating). High-Ti basalts (and picrite) and gabbro-dolerites are widely distributed in marginal areas as well as in the center of the Song Ða Rift and belong to three associations: andesite-basalt, andesite-picrite-basalt and trachybasalt-trachyandesitetrachydacite. The chemical compositions of high-Ti basalts are characterized by having high Ti content, moderately low Al, medium to low Mg, relatively low alkalinity, but high K, high Rb, Sr, Zr and LREE, but Nb and Ta varies from low- to hight. The high-Ti basalts have relatively restricted ranges of (87Sr/86Sr)i(0.7048- 0.7079) and ƐNd(t) values (−5.7 to +3.1) indicating weak lithospheric signature that may be related to their trace element-rich nature and this is consistent with abundant earlier studies suggesting that the high-Ti basalts at Song Da or elsewhere in the ELIP formed from low degrees of partial melting. © Springer International Publishing Switzerland 2016.
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