The migration of Tarim plume magma toward the northeast in Early Permian and its significance for the exploration of PGE-Cu–Ni magmatic sulfide deposits in Xinjiang, NW China: As suggested by Sr–Nd–Hf isotopes, sedimentology and geophysical data

Abstract

It is well known that a genetic link exists between the formation of ultramafic-rocks-hosted PGE-Cu–Ni sulfide deposits and the eruption of associated continental flood basalts. We here present a new model for the relationship between the Cu–Ni deposits located along the northeastern margin of Tarim and the internal Tarim basalt. Sr–Nd isotope and Hf isotope two-stage crust model ages TDMc indicate that whereas the Cu–Ni deposits along the northeastern margin of Tarim have Neoproterozoic and Mesoproterozoic lithology contamination, the surrounding rocks of Cu–Ni deposits in Beishan (Pobei) and Central Tianshan do not have Neoproterozoic lithologies. We propose that this is the result of mixing with the Neoproterozoic rocks in the interior of Tarim block. There is also an east–west trending positive magnetic anomaly belt in the central Tarim Basin, while Early Permian mafic–ultramafic rocks found along the northeastern margin of Tarim probably have a relationship with the Tarim Basin basalt. According to the Bouguer gravity map, the Bachu area near the center of Early Permian plume has high gravity values, with the northeastern high gravity belt in the central Tarim Basin possibly the result of a tilt of the mantle plume to the southwest below the Tarim block, which could be consistent with the earlier uplift and denudation in northeastern Tarim and later in southwestern Tarim from the Early Carboniferous to the Late Permian, as well as with observed uplift in the Bachu area in the Permian. We infer that the tilt of a mantle plume to the southwest below the Tarim block led to the inclined attitude of overlying rocks, with Early Permian magma flowing toward the northeast margin of Tarim. Based on this model, new PGE-Cu–Ni magmatic sulfide deposits related to Early Permian mafic–ultramafic intrusions may be found in the southwest area of Beishan, although this area is covered by Mesozoic and Cenozoic sediments.