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Diamondiferous kimberlites occur in the Wafangdian area in the eastern part of the North China Craton (NCC). In order to better constrain their magmatic source and emplacement time, we have investigated apatite from two kimberlites, i.e., the #110 dike kimberlite and the #50 root-zone kimberlite by measuring in situ their U–Pb and Sr–Nd isotopic compositions. The crystallization ages of the #110 and #50 apatites are 460.9 ± 16.8 Ma and 455.4 ± 19.3 Ma, respectively. For the #50 apatite, 87Sr/86Sr = 0.70453–0.70613 and εNd(t) = −2.74 to −4.52. For the #110 apatite, 87Sr/86Sr = 0.70394–0.70478 and εNd(t) = −3.46 to −5.65. Based on the similar distribution patterns of the rare earth elements (REEs) and the similar Sr-Nd isotope compositions of the apatite, it is believed that the #110 and #50 kimberlites have the same source region and the kimberlite magmas in Wafangdian were derived from an enriched mantle source (EMI). The primary magmatic composition has little effect on the emplacement pattern. It is more likely that the geological environment played an important role in controlling the retention and removal of volatile components (H2O and CO2). This led to the different evolutionary paths of the kimberlite magma in the later period, resulting in differences in the major element compositions of the apatite. High Sr concentrations may be associated with hydrothermal (H2O-rich fluid) overprinting events in the later magmatic period; the higher light rare earth element (LREE) concentration of the #50 apatite reflects the involvement of the REE3+ + SiO44− ⇔ Ca2+ + PO43− replacement mechanism. Two emplacement patterns of the #110 dike kimberlite (#110 apatite, low Sr, and high Si) and the #50 root-zone (#50 apatite, high Sr, and low Si) kimberlites were identified via major element analysis of the #110 apatite and #50 apatite. [ABSTRACT FROM AUTHOR]

Phlogopite is a crucial indicator for effectively constraining the magmatic evolution and emplacement mechanism of kimberlite. In this study, samples were collected from the No. 110 kimberlite pipe within diamond belt I and the No. 50 kimberlite pipe within diamond belt II in the southern Liaoning diamond mining area in the eastern North China Craton (NCC). Zonation is highly developed in the phlogopite; the major and trace element compositions of the phlogopite zonation in the samples were analyzed. In this study, phlogopite from the No. 50 pipe kimberlite (#50 phlogopite) zonation is divided into the following components: (1) The cores, low Ti-Cr xenocryst, average Mg# = 90.6, has a resorption structure, the presence of serpentine and talc minerals in low Ti-Cr cores (xenocrysts) can be used as evidence for hydrothermal metasomatism; (2) cores/inner rims (between core and outer rim), high Ti-Cr, it is thought to be related to the assimilation of mantle materials by deep kimberlite magma, average Mg# = 88.2; (3) outer rims, low-Cr/Cr-poor, average Mg# = 82.4, Fe, Al and Ba contents increased, and there was a trend of evolution to biotite composition believed to be related to the metasomatic metamorphism of melt and wall rock during the late magmatic evolution or ascent; (4) rinds, it is characterized by re-enrichment of Mg, rind I (low-Ti-Cr, average Mg# = 88.4), rind II (high-Ti-Cr, Mg# = 88.6), rind II may be formed earlier than rind I. Rind is very rare and has been reported for the first time in southern Liaoning kimberlite. This study was only accidentally found in the outermost part of #50 phlogopite, the Mg-rich feature represents an environment in which oxygen fugacity has increased. The phlogopite in samples from pipe No. 110 (#110 phlogopite) exhibits relatively homogeneous characteristics across different zones and is more enriched in Al and Ba, which is likely the result of mantle metasomatism. Due to its euhedral characteristics and limited composition variation, it is considered that #110 phlogopite is more likely to be derived from direct crystallization from magma than from xenocrysts. In addition, based on the simultaneous enrichment of Al and Fe in phlogopite from the core to the outer rim, pipe No. 50 was determined to be a micaceous kimberlite, while pipe No. 110 more closely resembles group I kimberlites. This paper proposes that successive pulses of kimberlite magma emplacement gradually metasomatized the conduit, and subsequent kimberlite magma ascended along the metasomatized conduit, thereby minimizing the interaction between the later magma and the surrounding mantle lithosphere. [ABSTRACT FROM AUTHOR]

Enclaves constitute a key tracer guide to assess the magmatic source and evolutionary processes of Cu–Mo–Au porphyry-type deposits. In this study, four types of enclaves were identified in the Baogutu reduced Cu porphyry-type deposit, West Junggar, Northwest China: gabbroic enclaves (Type 1) and schist enclaves (Type 2) are proposed to be restites and immiscible enclaves, respectively, which confirm the contributions of mantle components and sediments in the reduced Cu porphyry-type deposit. Fine-grained dioritic enclaves (Type 3) have a similar mineral composition and texture to the dioritic host rocks, which are probably autoliths derived from inhomogeneous fractional crystallization. Tuffaceous siltstone enclaves (Type 4) with a zircon U-Pb age of 339.2 ± 7.5 Ma (MSWD = 0.55), the formation age of which is in agreement with the host early Carboniferous rock unit, indicate that these tuffaceous siltstone enclaves might have formed in a contamination process. Moreover, the schist enclaves, together with the newly discovered 2691.3 ± 12.3 Ma inherited zircon in tuffaceous siltstone enclaves, further indicate that the Baogutu arc could be a continental arc. [ABSTRACT FROM AUTHOR]