Southwest Borneo, an autochthonous Pangea-Eurasia assembly proxy: Insights from detrital zircon record

The current tectonic model for Borneo in SE Asia suggests that the SW Borneo block rifted from NW Australia at ca. 190 Ma and drifted across the Tethyan Ocean to collide with Eurasia in the Early Cretaceous. But, the global zircon Hf trend after 200 Ma indicates that circum-Pacific-style accretionary orogens prevail. The SW Borneo detrital zircon data set, which combines our new data with previous data, shows consistent age peaks (ca. 250 Ma, 1.9-1.8 Ga, and 2.5-2.4 Ga) in late Permian to Early Cretaceous samples. The Banda terranes, a notable block derived from NW Australia, have distinct detrital zircon age peaks for pre-breakup and post-breakup. Available Borneo detrital zircon eHf(t) values for ca. 1.8 Ga and 2.4 Ga are indistinguishable from those of NW Australia sources, but eHf(t) values for 300-200 Ma are more negative than those from the Gondwanide orogen and are more similar to those from the Peninsular Malaysia Indosinian orogen. We suggest SW Borneo is a Triassic accretion zone at eastern Cimmeria that rifted from NW Australia in the Permian. The ca. 250 Ma negative eHf(t) values present in samples are characteristic of Tethyan-style collisional orogens and show participation in Pangea assembly. SW Borneo underwent further autochthonous accretion along its SE margin (ca. 186 Ma and ca. 140 Ma) in a Jurassic Meso-Tethys and Paleo-Pacific supra-subduction zone setting. Our revision locates SW Borneo with other SE Tethysides blocks in Eurasia where accretionary orogens have influenced rises after 200 Ma.