Paleoproterozoic Nb–enriched meta-gabbros in the Quanji Massif, NW China: Implications for assembly of the Columbia supercontinent

Diverse models have been proposed for the role of the Tarim Craton within the Paleoproterozoic Columbia supercontinent assembly. Here we report a suite of ∼1.71 Ga Nb-enriched meta–gabbro lenses in the eastern Quanji Massif, within the Tarim Craton in NW China. The meta–gabbroic rocks have Nb contents of 11.5–16.4 ppm with Nb/La ratios varying from 0.84 to 1.02 ((Nb/La)N = 0.81–0.98) and Nb/U ratios from 38.0 to 47.2. They show low SiO2 (45.1–48.5 wt.%) and MgO (5.96–6.81 wt.%) and Mg# (Mg# = Mg/(Mg + Fe) = 43.5–47.7), high FeOt (13.0–15.7 wt.%) and moderate TiO2 (1.70–2.51 wt.%), with tholeiitic affinities. These rocks possess low fractionated REE patterns without obvious Eu anomalies (Eu/Eu* = 0.87–1.02). Their primitive mantle-normalized elements patterns display significant Zr–Hf troughs, positive Nb anomalies, weak negative Ti and P anomalies, and high contents of Rb and Ba, resembling Nb-enriched basalts generated in arc-related tectonic settings. Their arc–like geochemical signatures together with whole rock ɛNd(t) values of 0.4–2.1 and corresponding old TDM (2.22–2.37 Ga) as well as (143Nd/144Nd)t and (87Sr/86Sr)t (t = 1712 Ma) values of 0.5104–0.5105 and 0.7030–0.7058, respectively, suggest that their precursor magma originated from mantle wedge peridotite metasomatised by subduction-derived melts. The results from our study reveal subduction along the eastern periphery of the Tarim Craton and marginal outgrowth continuing to ∼1.7 Ga within the Columbia supercontinent. [Display omitted] •Paleoproterozoic (1.71 Ga) Nb–enriched gabbros in Quanji Massif, NW China.•Magma sourced from mantle wedge peridotite metasomatized by subduction–derived melts and emplaced in an arc setting.•Assembly of the Columbia supercontinent continued to late Paleoproterozoic.