Paleomagnetic constraints on the paleogeography of Permian exotic blocks in the Yarlung Zangbo Mélange Zone, South Tibet

Understanding how Permian exotic blocks (mélanges) formed within the Yarlung Zangbo Suture Zone is crucial for reconstructing the evolution of the Neo-Tethys Ocean and the paleogeography of Gondwana. Here, we report new paleomagnetic data from the Zhongbei limestone—one of the most representative of these blocks in South Tibet—to better constrain its history. Thermal demagnetization isolated a strong overprint component (unblocking up to 300−450 °C) across 24 sites (175 samples), with a mean direction of Dg = 167.2°, Ig = 11.7° (kg = 11.5, α95 = 9.1°). This component is likely carried by abundant framboidal magnetite, overgrowths, embayed edges, or authigenic microcrystalline magnetite. Analysis of 28 studies of remagnetization along the Yarlung Zangbo Suture Zone suggests that the shallow directions are an overprint related to Late Cretaceous arc−continent collision near the equator at ca. 70 Ma. A high-temperature component (unblocking up to 480−580 °C) was isolated from 17 sites (111 samples) with Ds = 140.7°, Is = 54.0° (ks = 24.0, α95 = 7.4°), and it passed a fold test. In these samples, the presence of subhedral to euhedral and single microcrystalline detrital (titano)magnetite grains is observed, suggesting that the high-temperature component is primary. It is likely that the primary component can only be resolved when detrital (titano)magnetite is preserved in sufficient quantity. This component yielded a Permian paleolatitude of 34.5° ± 8.7°S for the Zhongbei limestone block. Our results suggest that the exotic blocks in the Yarlung Zangbo Suture Zone either originated on a seamount along the northern margin of Greater India or were originally part of Greater India.