A fragment of the ca. 890 Ma large igneous province (LIP) in southern Tarim, NW China: A missing link between São Francisco, Congo and North China cratons

Abstract

We identify an early Neoproterozoic Large Igneous Province (LIP) fragment in the South Tarim Terrane (STT) of the NW China (herein term as the Sailajiazitage LIP fragment). The thickness of the volcanic sequence, mainly composed of basalts (ca. 4600 m) and minor rhyolites (ca. 800 m), is up to ca.5300 m. Four zircon samples from the three units of rhyolite at the top, middle and lower parts of the lava sequence yield consistent and concordant SHRIMP/LA-ICPMS U-Pb ages of 895.8 ± 3.7 /892.0 ± 4.1 Ma, 891.8 ± 3.5/894.5 ± 5.8 Ma, 899.0 ± 4.6/893.0 ± 5.9 Ma and 884.5 ± 4.9/894.2 ± 4.8 Ma, respectively, indicating the short duration of the thick volcanic sequence. Systematic geochemical data revealed that the basalts were derived from partial melting of a depleted asthenenospheric mantle source coupled with variable degrees of AFC effect. The rhyolites show typical A-type (or A1-type) granite geochemical features as demonstrated by their high HFSE contents (e.g., Zr = 400–900 ppm, Nb = 70–140 ppm). Both elemental and Nd-Hf-O isotope compositions argue that the silicic magma was the daughter product of the intensive fractionation of the coeval basalts and their zirconium saturation temperature was up to 900 °C, significantly higher than those of A-type granites emplaced in a post-orogenic setting but consistent with those A-type granites genetically related to a mantle plume. Its huge thickness (>5300 m), short duration at ca. 890 Ma and typical continental flood basalt (CFB) geochemical features argue for this being a fragment of an early Neoproterozoic LIP and likely proximal to its plume centre.The c. 890 Ma age suggests a link with the previously proposed reconstruction of North China, São Francisco and Congo cratons, based on their shared 920–890 Ma LIP fragments. This study supplies further evidence for a ca. 920–890 Ma plume or superplume inducing the initial breakup of the supercontinent Rodinia.