In the past ten years, a great deal of geological study has been reported on the magmatic rocks exposed in the central and western region of the Kuluketage Block, while similar research in the eastern region has rarely been reported. In this paper, we report zircon U–Pb geochronological, zircon Lu–Hf isotopic, whole-rock elemental and Sr–Nd–Pb isotopic data for the Dapingliang intermediate-acid intrusive rocks in the eastern Kuluketage Block, in order to evaluate its petrogenesis and tectonic significance. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating provided a weighted mean 206Pb/238U age of 735 ± 3 Ma for the albitophyre (D1), 717 ± 2 Ma for the granite porphyry (D2) and 721 ± 1 Ma for the diorite porphyrite (D3). Geochemical analyses reveal that D1 and D2 belong to Na-rich alkaline A-type granites, and D3 shows the features of high-K calc-alkaline I-type granite. D1 and D2 are characterized by light rare earth element (LREE) enrichment and relative depletion of high field strength element (HFSE), with relatively flat heavy rare earth element (HREE) patterns and obviously negative Eu anomalies. D3 is characterized by the enrichment of LREE and depletion of HFSE, with negative slope HREE patterns and slightly negative Eu anomalies. In tectonic discrimination diagrams, D1 and D2 fall in the within-plate granite (WPG) field, indicating a rift setting. Although D3 falls within the volcanic arc granite (VAG) field, it most likely formed in a rift setting, as inferred from its petrology, Sr–Nd–Hf isotopes and regional tectonic evolution. Based on pronounced εNd(t), εHf(t), Pb isotopic data, TDM2 and high (87Sr/86Sr)i and elemental compositions, D1 was derived from the partial melting of basement amphibolites of the old lower crust. D2 originated from a mixture of the old lower crust and depleted mantle-derived magmas and was dominated by partial melting of the basement amphibolites of the lower crust. D3 could have been formed by partial melting of K-rich hornblende in the lower crust. Combining previous studies, we think that the c. 745–710 Ma magmatic rocks were formed in a continental rift setting. A partial melting scheme, triggered by underplating of mantle plume-derived magmas, is proposed to interpret the formation of c. 745–710 Ma A-type and I-type granitoids, mantle-derived mafic dykes, bimodal intrusive rocks, adakitic granites and volcanic rocks. These magmatic activities were probably a reflection of the break-up of the Rodinia supercontinent.Highlights(1) Circa 720 Ma magmatism in the eastern Kuluketage Block.(2) Na-rich granite was derived from partial melting of basement amphibolites.(3) The c. 745–710 Ma magmatic rocks were formed in a continental rift setting.(4) The underplating of mantle plume-derived magmas is proposed.

During the past 50 years, many geological and ore-deposit investigations have led to the discovery of the Fe–P–(Ti)-oxide deposits associated with mafic–ultramafic–carbonatite complexes in the Kuluketage block, northeastern Tarim Craton. In this paper, we discuss the genetic and ore-forming ages, tectonic setting, and the genesis of these deposits (Kawuliuke, Qieganbulake and Duosike). LA-ICP-MS zircon U–Pb dating yielded a weighted mean ²⁰⁶Pb/²³⁸U ages of 811 ± 5 Ma, 811 ± 4 Ma, and 840 ± 5 Ma for Kawuliuke ore-bearing pyroxenite, Qieganbulake gabbro and Duosike ore-bearing pyroxenite, respectively. The CL images of the Kawuliuke apatite grains show core–rim structure, suggesting multi-phase crystallisation, whereas the apatite grains from Qieganbulake and Dusike deposits do not show any core–rim texture, suggesting a single-stage crystallisation. LA-ICP-MS apatite ²⁰⁷Pb-corrected U–Pb dating provided weighted mean ²⁰⁶Pb/²³⁸U ages of 814 ± 21 Ma and 771 ± 8 Ma for the Kawuliuke ores, and 810 ± 7 Ma and 841 ± 7 Ma for Qieganbulake and Duosike ores, respectively. The core–rim texture in apatite by CL imaging as well as two different ore-forming ages in the core and rim of the apatite indicate two metallogenic events for the Kawuliuke deposit. The first metallogenic period was magmatic in origin, and the second period was hydrothermal in origin. The initial ore-forming age of the Kawuliuke Fe–P–Ti mineralisation was ca 814 Ma and the second one was ca 771 Ma. On the other hand, the ore-forming ages of the Qieganbulake and Duosike deposits were ca 810 Ma and ca 841 Ma, respectively. Qieganbulake and Duosike deposits were of magmatic origin. Combined with previous geochronological data and the research on the tectonic background, we infer that the Kawuliuke, Qieganbulake and Duosike Fe–P–(Ti)-oxide deposits were formed in a subduction-related tectonic setting and were the product of subduction-related magmatism.

The Qieganbulake deposit associated with a mafic–ultramafic–carbonatite complex in the Kuluketage block is not only the world’s second-largest vermiculite deposit, but also a medium-size carbonatite-related phosphate deposit. Field observations, radiometric dating results and Sr–Nd–Hf isotopes reveal that the parental magmas of the carbonatite and mafic–ultramafic rocks are cogenetic and formed synchronously at c. 810 Ma. Geochemical characteristics and Sr–Nd–Hf–S isotopes ((87Sr/86Sr)i = 0.70581–0.70710; ϵNd(t) = −0.20 to −11.80; ϵHf(t) = −7.5 to −10.3; δ34S = +0.7 ‰ to +3.0 ‰ (some sulfides with high δ34S values (+3.2 to +6.6) were formed by late hydrothermal sulfur)), in combination with mineral compositions and previous research, strongly indicate that the Qieganbulake mafic–ultramafic–carbonatite complex formed via extensive crystal fractionation/cumulation and liquid immiscibility of a carbonated tholeiitic magma, possibly derived from partial melting of an enriched subcontinental lithospheric mantle previously modified by slab-released fluids and sediment input in a continental rift setting. The coupled enriched Sr–Nd isotopic signatures, in combination with previous research, suggest that the enriched subcontinental lithospheric mantle could have been metasomatized by asthenospheric mantle melts to different degrees. The Qieganbulake carbonatite-related phosphate ores were the products of normal fractional crystallization/cumulation of P–Fe3+ complex enriched carbonatite magma in high oxygen fugacity conditions, which was generated by liquid immiscibility of CO2–Fe–Ti–P-rich residual magma undergoing high differentiation.