Subduction polarity of the Ailaoshan Ocean (eastern Paleotethys): Constraints from detrital zircon U-Pb and Hf-O isotopes for the Longtan Formation

• DOI: 10.1130/b35294.1
• Publication Date: 2019-10-07T19:21:25Z
• Authors: Xiao-Ping Xia; Jian Xu; Chao Huang; Xiaoping Long; Meiling Zhou
• Keywords: Forearc; Volcanic arc; Andesites

Abstract The Paleotethys Ailaoshan Ocean separated the South China and Indochina blocks during late Paleozoic. Uncertainty remains regarding subduction of this ocean—whether it was subducted eastward beneath block or westward block. In study, we present new detrital zircon U-Pb age, Hf O isotope data from Longtan Formation, which recognized to be deposited before ocean closed. Our results show that formation can divided into three units: Unit 1 is distributed west suture dominates area; contains major age peaks at 290–250 Ma minor multiple old peaks. 2 consists a distribution suture, shows dominant 250 peak; zircons are very few not present. Their isotopic signatures similar those unit 1. 3 east characterized by single distinct ca. 240 peak with almost no Precambrian zircons. We interpret units were likely in back-arc forearc basin, respectively, volcanic arc developed on eastern margin block, present-day northeastern Japan arc. Meanwhile, basin western Therefore, may undergone bipolar both blocks, respectively.