Petrogenesis of the Devonian high-Mg rock association and its tectonic implication for the Chinese Altai orogenic belt, NW China

摘要: Abstract The Chinese Altai is a key region to decipher the accretionary history of gigantic CAOB, one largest orogenic belts on earth. However, tectonic implication widely distributed Paleozoic magmatic rocks remain debated. In this study, suite igneous rocks, including high Mg dacite Kangbutiebao Formation and associated gneissic granodiorites, have been studied for their petrogenesis implication. dated at 400 ± 2 Ma, which broadly resembles emplacement age granodiorites 406 ± 9 Ma, possibly suggesting that they were generated in same tectono-magmatic event. Both predominant zircon inheritances ∼500 Ma, consistent with population widespread Habahe sedimentary sequence, indicating precursor magmas probably mainly derived from sediments. high-Mg rock association has similar REE trace element patterns those sediments plot close field Th/Ta versus La/Ta diagram. Their A/CNK ratios (1.33–2.05) imply, magma source dominated by rocks. Similarly, La/Sm also suggest greater contribution rather than altered oceanic crust generation. Mg# values (∼51) argue against derivation purely remelting order explain these participation mantle-derived melt into considered. Zircons mostly yield e Hf ( t ) +0.85 +9.71, supporting involvement juvenile materials Samples fall as sanukitoids TiO 2 Sr/Y Y diagrams, fractional crystallization trend differentiated Harker diagram, petrogenetic process like typical sanukitoid elsewhere. This study shows Setouchi area, our involved melting subducted hot subduction regime. Combined previous work, ridge regime considered interpret early Devonian evolution Altai.