Cretaceous Tethyan subduction in SE Borneo: Geochronological and geochemical constraints from the igneous rocks in the Meratus Complex

Yuejun Wang, Xin Qian, Peter A. Cawood, Azman Ghani, Chengshi Gan, Sainan Wu, Yuzhi Zhang, Yang Wang, Peizhen Zhang

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Abstract

SE Borneo lies at the junction of the Pacific and Tethyan realms. The Mesozoic geological record of the region is dominated by convergent plate margin activity, although the geological details and its broader role in the SE Asia evolution are poorly documented. This paper presents geochronological, whole-rock elemental and Sr-Nd-Pb isotopic data on the igneous rocks from the Meratus Complex in SE Borneo. The Meratus ophiolite might form at the Late Jurassic-Early Cretaceous (∼150–115 Ma), and the spatially-associated Haruyan Volcanics, Belawayan granitoids and their equivalents generated in the Early Cretaceous (∼140–107 Ma). The Haruyan and Pitap formations and their equivalents are dominated by Early Cretaceous (∼140–115 Ma) volcanic rocks and late Early Cretaceous (∼115–100 Ma) siliciclastic rocks, respectively. The mafic-intermediate igneous rocks in the Meratus Complex are characterized by MgO = 2.04–13.20 wt%, TiO2 = 0.48–1.51 wt%, Nb/La = 0.09–0.42, εNd(t) = +4.6–+7.7, (206Pb/204Pb)i = 18.15–18.61, (207Pb/204Pb)i = 15.41–15.63 and (208Pb/204Pb)i = 38.03–38.63, and originated from the slab-related mantle wedge. The granitoids share similar elemental ratios and Sr-Nd-Pb isotopic compositions with the coeval mafic rocks, with Nb/La = 0.20–0.30, εNd(t) = +4.8–+6.0, Δ8/4 = 26.2–38.8 and Δ 7/4 = 5.0–7.7, representing the products of the wedge-originated juvenile crust. Synthesis of all data reveals a NW-Australian affinity for SE Borneo. The Early Cretaceous fore-arc tectonic setting extends southerly into the Bantimala (SW Sulawesi) and Luk Ulo (Central Java), constituting a united Early Cretaceous Central Indonesian accretionary zone. The Meratus Ocean subducted beneath the Argo fragment since ∼140 Ma and likely assembled with the Sundaland margin at ∼100 Ma in response to the Neotethyan consumption.

Original languageEnglish
Article number105084
Number of pages15
JournalJournal of Asian Earth Sciences
Volume226
DOIs
Publication statusPublished - 1 Apr 2022

Keywords

  • Australian affinity
  • Elemental and isotopic compositions
  • Igneous rocks
  • Meratus complex
  • Neotethyan subduction
  • SE Borneo
  • Zircon U-Pb dating

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