Provenance of glacial marine conglomerates in the Permian Lagar Formation of southern Tibet: Evidence for affinity of the Lhasa Terrane with Australia

• Published in: Journal of Asian earth sciences Vol. 187; p. 104064
• Main Authors: Ma, Jianfei, An, Xianyin, Huang, Feng, Li, Youguo, Zhang, Yujie, Zhu, Tongxing
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2020
• Subjects: Geochemistry; Glacial–marine diamictites; Lhasa Terrane; Provenance; Tonalitic conglomerates; Lhasa Terrane; Tonalitic conglomerates; Geochemistry; Provenance; Glacial–marine diamictites
• DOI: 10.1016/j.jseaes.2019.104064
• ISSN: 1367-9120

[Display omitted] •Upper Paleozoic glacial conglomerates in the Lhasa Terrane contain tonalitic clasts.•Isotopic and geochemical data indicate an Australian provenance for these clasts.•The Lhasa Terrane was close to Australia during the Paleozoic. Paleogeographic reconstructions of the Lhasa Terrane of the southern Tibetan Plateau are uncertain in Paleozoic, and investigating the paleogeographic location of the terrane via the current geographical configuration is difficult. However, gravels contained within glacial sediments offer an opportunity to solve this problem. The Lagar Formation in the central Lhasa sub–Terrane contains glacial–marine deposits that incorporate gravel clasts composed of granitoids, sandstone, quartzite, limestone, and rhyolite. These diamictites were derived from continental glaciation and were deposited mainly near a grounding line or ice front in littoral–neritic to neritic environments. We present new zircon U–Pb isotopic and whole-rock geochemical data for the tonalitic conglomerates of the Lagar Formation. The results indicate that the tonalites crystallized during the Paleoproterozoic (~1.76 Ga) and show a geochemical affinity with I-type granite. The tonalites typically have negative Eu anomalies (δEu = 0.31–0.37), high concentrations of rare-earth elements, depletion in high-field-strength elements, enrichment in Th, marked positive zircon εHf(t) values (6.46–14.68), εNd(t) values of −1.24 to +1.76, and TDM2 ages of 2.37–2.13 Ga. All of these data indicate that the tonalites were produced by the partial melting of modified mafic crust or underplate in a subduction-related environment. On the basis of a comprehensive analysis of all 1.8–1.7 Ga magmatism in east Gondwana, we propose that the most likely provenance of the tonalitic conglomerates is southern Arunta and Mt. Isa in northern Australia. Therefore, the central Lhasa sub–Terrane may have been located near Australia during the Paleozoic.