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Owing to the paucity of research on synchronous mafic rocks in the Tarim Basin, the late Paleozoic–early Mesozoic tectonic development of this region is not well defined. The Halaqi region is situated on Tarim's northwest edge, and numerous mafic dikes can be found cross-cutting the Permian strata. The whole-rock geochemistry, zircon U–Pb age, and Sr–Nd isotopic signature of these mafic rocks have never been reported before, and this contribution can offer geochronological and petrogenetic investigations that provide fresh insight into the geodynamic development of the area. Major oxide contents in the Halaqi mafic rocks vary, including SiO2 (45.74–50.31 wt.%), Al2O3 (13.28–14.8 wt.%), FeOT (16.48–19.19 wt.%), MgO (7.58–10.32 wt.%), CaO (7.19–12.39 wt.%), Na2O (2.97–4.50 wt.%), K2O (0.24–0.63 wt.%), TiO2 (1.11–1.29 wt.%), MnO (0.14–0.16 wt.%), and P2O5 (0.13–0.17 wt.%). The mafic rocks are enriched in high-field-strength elements (e.g., Zr and Hf) and large-ion lithophile elements (e.g., Sr, Th, and U) but depleted in Nb, Ta, and P. The total REEs in the rocks are lower (ΣREE = 72.80–86.85 ppm), and HREEs are somewhat depleted in comparison to LREEs, with positive Eu anomalies (Eu/Eu* = 1.05–1.17) but weak negative Ce anomalies (Ce/Ce* = 0.91–0.93). Zircon U–Pb ages of 201–247 Ma were obtained from a total of 18 magmatic zircon grains found in the mafic rocks that were studied. These results point to a middle-to-late Triassic emplacement. The mafic dikes exhibit somewhat enriched Nd isotopic compositions (εNd(t) = –1.6~–0.2) and an older Nd model age (TDM = 1.24–1.37 Ga). The Halaqi middle–late Triassic mafic dikes are thought to have originated from the same tectonic background as the Permian Tarim Large Igneous Province, along with similar geochemical and isotopic compositions. This suggests that they are all products of the interaction between asthenospheric and lithospheric mantles in an intraplate extensional environment. Research indicates that the Triassic mafic magmatism in northwest Tarim could be the product of the continuous thermal pulse of the Tarim mantle plume and be a part of the Tarim LIP. [ABSTRACT FROM AUTHOR]

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]

During the Ediacaran–Cambrian transition, a series of stratal continuous and well-preserved siliceous rock and phosphorite assemblages developed in Qingzhen, Guizhou Province, China, facilitating research on the biological evolution, marine chemistry, and palaeoecological environment of this period. Therefore, we investigated the paleontology, trace and rare earth elements, total organic carbon, total sulfur content, and Zn isotopes of the phosphorus-bearing rock series in the Taozichong Formation of the Cambrian period in Qingzhen. Geochemical analysis reveals that the sedimentary rocks in this area were formed in the oxygen-rich seawater environment and were not affected by high-temperature hydrothermal activity. The upwelling ocean current provided abundant rare earth elements and other nutrient elements, as well as conditions for the prosperity of biota in Qingzhen. In addition, the δ66Zn value (−0.21‰–0.41‰ range and 0.17‰ mean) in the Qingzhen phosphorous rock series was much lower than that in seawater, indicating a strong level of biological productivity. The variation trend of δ13C, δ18O, and δ66Zn exhibited four stages and three obvious drift events. The results suggest that climate change during this period led to the intermittent flourishing and extinction of organisms, which triggered the negative drift of δ13C and δ18O in the ocean, resulting in a coordinated response of δ66Zn. The unique ecological environment of the Taozichong Formation in Qingzhen also provides favorable conditions for the population continuation of Ediacaran-type benthic soft-bodied metazoon dominated by discoid fossils, Shaanxilithes, worm fossils, and sponge fossils in the Cambrian strata, as well as participation in the global biological explosion events. The study area provides new insights for rebuilding the global Ediacaran–Cambrian ecosystem during the transition period. [ABSTRACT FROM AUTHOR]

Prydz Bay is an important part of the Pan-African high-grade tectonic mobile belt. The focus of this investigation, by applying zircon LA-ICP-MS U-Pb geochronology, zircon Lu-Hf isotope systematics, and whole-rock geochemistry, is on Pan-African pegmatites in the Larsemann Hills of Prydz Bay, East Antarctica, their association with country rocks, and the formation conditions. Based on the obtained results, it is concluded that the pegmatites exhibit elevated levels of silica and alkali and possess peraluminous features. These pegmatites originated during the late Neoproterozoic–Early Cambrian (Pan-African) event, specifically in the D2–D4 stages. The D2 stage occurred between 546 and 562 Ma, followed by D3-stage pegmatites around 534 Ma. The pegmatites from the D2–D3 stages are considered to originate from Paleoproterozoic crustal materials, while there are at least two phases of pegmatites in the D4 stage (~517 Ma and ~521 Ma). The D4-1 pegmatite (~521 Ma) suggested both Paleo–Mesoproterozoic crustal origin, perhaps connected to extension. The D4-2 pegmatite (~517 Ma) originated from the crust layers. In the Larsemann Hills, Pan-African pegmatites formed in a recurring regime of tension. Therefore, the obtained data elucidate that a Pan-African stretching process might have occurred in Prydz Bay. [ABSTRACT FROM AUTHOR]