Late Cretaceous Nature of SW Borneo and Paleo-Pacific Subduction: New Insights from the Granitoids in the Schwaner Mountains

Abstract Cretaceous igneous rocks in SW Borneo are significant for investigating the Paleo-Pacific subduction and regional correlation. This paper presents new zircon ages Sr–Nd–Pb–Hf–O isotopic whole-rock geochemical data granitoids Schwaner Mountains. These granitoid samples yield formation of 92–80 Ma can be geochemically subdivided into Group 1 biotite granite granodiorite 2 monzogranite. has higher εHf t values +1.2–+14.5 lower δ18O 5.2–6.6‰ than with −1.5–+5.9 6.1–6.6‰, respectively. show variable εNd −1.9–+1.7, (206Pb/204Pb)i ratios 18.63–19.29, (207Pb/204Pb)i 15.62–15.69, (208Pb/204Pb)i 38.67–39.49 products partial melting newly underplated mafic a component crustal rocks. slightly negative −1.1–−1.5 was originated from metasedimentary juvenile component. were formed continental arc setting related to during Late compare those contemporaneous I-type granites along Kuching zone NW Borneo. Those A-type affinities easternmost Peninsular Malaysia Singapore east Sundaland might back-arc extensional after subduction.