Middle Neoproterozoic (ca. 700 Ma) tectonothermal events in the Lhasa terrane, Tibet: Implications for paleogeography

Pei yuan Hu, Qing guo Zhai, Peter A. Cawood, Guo chun Zhao, Jun Wang, Yue Tang, Zhi cai Zhu, Wei Wang, Hao Wu

Research output: Contribution to journalArticleResearchpeer-review

2 Citations (Scopus)

Abstract

The evolution of the Mozambique Ocean spans the Rodinia and Gondwana supercontinent cycles playing a key role in Earth history. Integrated petrological, geochronological, geochemical, and isotopic data on the Neoproterozoic units from the Lhasa terrane, Tibet, constrain the magmatic and metamorphic evolution of the ocean. Our results reveal two magmatic (ca. 695 Ma and ca. 671 Ma) and two metamorphic (ca. 700 Ma and ca. 650 Ma) pulses. Gabbros define the first magmatic suite. They have within-plate affinities and experienced crustal contamination. Their positive zircon εHf(t) (+1.6 to +9.6) and whole-rock εNd(t) (+2.7 to +6.1) values are indicative of a depleted mantle source. Gabbros from the second magmatic event belong to the tholeiitic series, lack evidence for crustal contamination, and are geochemically similar to E-MORB. They have negative to positive zircon εHf(t) (−3.2 to +1.5) and low positive whole-rock εNd(t) (+1.4 to +2.0) values, and were probably derived from an E-MORB-type enriched mantle source, slightly modified by subduction components. Evidence for the metamorphic events (ca. 700 and ca. 650 Ma) was obtained from U–Pb dating of zircon rims of marbles and gabbros, which are characterized by low Th/U ratios (0.01–0.07) indicative of a metamorphic origin. Integrating previous studies with the data presented in this contribution, we suggest that the history of the Lhasa terrane was linked to the evolution of the Mozambique Ocean. The older mafic magmatism (ca. 695 Ma) and metamorphism (ca. 700 Ma) formed during terrane accretion processes along an active continental margin to the ocean. The relatively younger mafic magmatism (ca. 671 Ma) provides a record from an oceanic fragment that was metamorphosed (ca. 650 Ma) during closure of the Mozambique Ocean.

Original languageEnglish
Number of pages13
JournalGondwana Research
DOIs
Publication statusAccepted/In press - 20 Feb 2021

Keywords

  • Lhasa terrane
  • Mafic magmatism
  • Metamorphism
  • Mozambique Ocean
  • Tibet

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