The assembly of Rodinia: The correlation of early Neoproterozoic (ca. 900 Ma) high-grade metamorphism and continental arc formation in the southern Beishan Orogen, southern Central Asian Orogenic Belt (CAOB)

Zong K, Klemd R, Yuan Y, He Z, Guo J, Shi X, Liu Y, Hu Z, Zhang Z (2017)

Publication Language: English

Publication Type: Journal article

Publication year: 2017

Journal

Precambrian Research Elsevier

Book Volume: 290

Pages Range: 32-48

DOI: 10.1016/j.precamres.2016.12.010

Abstract

An early extensive Neoproterozoic (ca. 900 Ma) continental magmatic arc system covering hundreds of kilometers has been reported to occur in the South Beishan Orogenic Belt (SBOB) and the Central Tianshan (CTA) in the southern Central Asian Orogenic Belt (CAOB). However, evidence for coeval high-grade metamorphism and thus the formation of an accretionary orogen in the framework of Rodinia is ambiguous or absent. This study provides new petrological, geochemical and geochronological data for garnet-bearing schists (quartz + garnet + biotite + plagioclase ± muscovite) from the SBOB in order to constrain its Neoproterozoic metamorphic history. The metamorphic zircon rims are either unzoned or display sector zoning in CL-images and reveal REE patterns with flat HREE patterns and negative Eu anomalies, which are interpreted to be in chemical equilibrium with garnet and plagioclase. The zircon U-Pb dating yields concordant U-Pb ages of 900 ± 3 Ma, 897 ± 2 Ma and 898 ± 4 Ma for the metamorphic zircon rims. The inherited detrital zircon cores of one sample display a concordant U-Pb age of 1397 ± 5 Ma that is consistent with the timing of formation for the extensive Mesoproterozoic continental arc in the SBOB and CTA. Based on phase equilibrium geothermobarometry and average P-T thermobarometric calculations, minimum amphibolite-facies P-T conditions are estimated to be >600 °C at pressure >0.6 GPa, which is thought to have been overprinted by subsequent Paleozoic metamorphism. However, the Ti-in-zircon thermometer still reveals temperatures of up to 840 °C using the composition of metamorphic zircon rims, suggesting former ca. 900 Ma granulite-facies peak metamorphic temperatures. The combined petrological and geochronological evidence in conjunction with the continental affinity of the regional metamorphic rocks suggests that the SBOB and the eastern CTA experienced an early Neoproterozoic accretionary orogenesis during the final assembly stage of Rodinia.

Authors with CRIS profile

Reiner Klemd Professur für Geochemie von Lagerstätten

Involved external institutions

China University of Geosciences / 中国地质大学 CN China (CN) Chinese Academy of Geological Sciences (CAGS) / 中国地质科学院 CN China (CN)

How to cite

APA:

Zong, K., Klemd, R., Yuan, Y., He, Z., Guo, J., Shi, X.,... Zhang, Z. (2017). The assembly of Rodinia: The correlation of early Neoproterozoic (ca. 900 Ma) high-grade metamorphism and continental arc formation in the southern Beishan Orogen, southern Central Asian Orogenic Belt (CAOB). Precambrian Research, 290, 32-48. https://dx.doi.org/10.1016/j.precamres.2016.12.010

MLA:

Zong, Keqing, et al. "The assembly of Rodinia: The correlation of early Neoproterozoic (ca. 900 Ma) high-grade metamorphism and continental arc formation in the southern Beishan Orogen, southern Central Asian Orogenic Belt (CAOB)." Precambrian Research 290 (2017): 32-48.

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