Petrogenesis and tectonic implications of Early Cretaceous granite porphyry in the Taipingtun area, central Great Xing'an Range, NE China. Issue 7 (16th April 2022)

• Record Type: Journal Article
• Authors: Tai, Baoqiang; Mi, Wentian; Wang, Genhou; Kong, Xu; Li, Yingjie; Cheng, Jianbo
• Is Part Of: Geological journal. Volume 57:Issue 7(2022)
• Page Start: 2914
• Page End: 2935
• Publication Date: 2022-04-16
• Subjects: Early Cretaceous -- geochemistry -- granite porphyry -- Great Xing'an Range -- zircon U–Pb geochronology; Geology -- Periodicals; 551
• DOI: 10.1002/gj.4447
• Languages: English
• ISSNs: 0072-1050

Abstract

Abstract : New LA‐ICP‐MS zircon U–Pb geochronology, whole‐rock geochemistry and Hf isotopic data have been studied on the Taipingtun granite porphyry to determine its petrogenesis and constrain the tectonic setting of the central Great Xing'an Range, northeastern China, during the Early Cretaceous. The results of zircon U–Pb dating suggest that the Taipingtun granite porphyry was emplaced during the Early Cretaceous (122–123 Ma). Geochemically, the granite porphyries have high contents of SiO2 (75.76–78.66 wt%) and (K2 O + Na2 O) (7.14–8.29 wt%), and low Al2 O3 (11.09–12.81 wt%) and CaO (0.15–0.29 wt%), indicating peraluminous and high‐K calc‐alkaline features. Additionally, these rocks are characterized by strong Th, U, K, and Rb enrichment; Ba, Sr, P and Ti depletion; high Ga/Al ratios (10, 000*Ga/Al = 2.60–4.92) and negative Eu anomalies (δEu = 0.02–0.13). According to the zircon saturation thermometer results, zircon saturation temperatures range from 756 to 959°C with an average of 823°C, displaying high magmatic temperature for the parental magma. Based on these geochemical characteristics, it can be reasonably inferred that the initial composition of the Taipingtun granite porphyry melts exhibited an A‐type magmatic affinity. Furthermore, zircon grains within the Taipingtun granite porphyry have εHf (t) values of 7.12 to 10.99 and TDM2 model ages of 476–726 Ma. The Ba/La (average 3.89), Nd/Th (average 2.25), Zr/Hf (average 22.55), Ti/Zr (average 2.96) and Rb/Sr (average 4.21) values display the characteristics of crust‐derived magmas. Moreover, these rocks have obviously negative Eu anomalies (average 0.13) and relatively high Y (average 37.83 ppm) and Yb (average 4.15 ppm) contents, suggesting the magmas are generated in a low‐pressure environment. Thus, we consider the primary magmas of the Taipingtun granite porphyry may have been predominantly derived from the partial melting of juvenile crustal rocks at low pressure. Combined with the regional geological data, we suggest that the Taipingtun granite porphyry was formed in an extensional tectonic environment, and possibly related to the subducted Palaeo‐Pacific Ocean Plate in the Early Cretaceous. Abstract : The Taipingtun granite porphyry in the central Great Xing'an Range was emplaced during the Early Cretaceous (ca. 122–123 Ma). Their geochemical signatures indicated that they exhibited A‐type affinity, and were probably derived from the partial melting of juvenile crustal rocks, suggesting that they were formed in an extensional tectonic setting related to the retreat of the subducted Palaeo‐Pacific Ocean (PPO) Plate.