An evolving tectonic environment of Late Carboniferous to Early Permian granitic plutons in the Chinese Altai and Eastern Junggar terranes, Central Asian Orogenic Belt, NW China. (15th June 2018)

• Record Type: Journal Article
• Authors: Zhang, Chen; Liu, Dongdong; Luo, Qun; Liu, Luofu; Zhang, Yunzhao; Zhu, Deyu; Wang, Pengfei; Dai, Quanqi
• Is Part Of: Journal of Asian earth sciences. Volume 159(2018)
• Page Start: 185
• Page End: 208
• Publication Date: 2018-06-15
• Subjects: Central Asian Orogenic Belt -- Zircon geochronology -- Sr-Nd-Hf isotopes -- Syn-collisional -- Strike-slip -- Granitic magmatism; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2017.08.008
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: The youngest arc-related granitic pluton in Eastern Junggar terrane has an age of ∼308 Ma. The final collision between the Siberian and Kazakhstan plates occurred at ∼305 Ma. The 305–280 Ma granitic plutons formed under syn-collisional and post-orogenic strike-slip-related settings. Abstract: The Central Asian Orogenic Belt (CAOB) represents one of the most important sites of juvenile crustal growth during the Phanerozoic. Located in the central part of the CAOB, the Chinese Altai and Eastern Junggar terranes record the collisional processes between the peri-Siberian and Kazakhstan orogenic systems. However, the precise timing of collision between the two terranes remains controversial. The Wukuli and Kadelat plutons in the Chinese Altai belt are dated at ∼305 and ∼280 Ma respectively, whereas the Aketas pluton in the Eastern Junggar terrane is dated at ∼308 Ma. Granites from the Wukuli and Kadelat plutons are strongly peraluminous (A/CNK > 1.1), and are characterized by low Al2 O3, Na2 O, MnO, MgO, CaO and heavy rare earth element (HREE) contents, but with high SiO2, K2 O and Rb contents as well as high Rb/Sr ratios. Granites from the Wukuli pluton have low εNd ( t ) and εHf ( t ) values of −3.7 to −3.4 and −9.7 to +4.9, whereas those from the Kadelat pluton have values of −3.6 to −3.4 and −8.0 to +2.6. These features suggest S-type affinity for the Wukuli and Kadelat plutons with magma derivation through partial melting of Mesoproterozoic metasediments. The Aketas pluton is composed of weakly peraluminous quartz monzonites that have A/CNK values ranging from 0.92 to 1.08, with high Na2 O, Sr, and Sr/Y, and low Y, Yb, Nb, and Ta. These rocks display positive εNd ( t ) (+4.8 to +6.4) and εHf ( t ) (+9.7 to +14.6) values, and low initial 87 Sr/ 86 Sr ratios (0.703357–0.703868), similar to modern adakites, suggesting that the quartz monzonites were derived from the partial melting of lower crustal material. The geochemical characteristics suggest that the Aketas pluton was formed in a subduction-related setting, the Wukuli pluton in a syn-collisional setting, and the Kadelat pluton in the subsequent post-orogenic strike-slip-related setting. In combination with data from other granitoids in these two terranes, the Aketas pluton represents the youngest record of subduction-related environments, suggesting that the final collision between the Chinese Altai and Eastern Junggar terranes might have occurred between 308 and 304 Ma.