Neoproterozoic rifting in the Upper Yangtze Continental Block: Constraints from granites in the Well W117 borehole, South China.

ABSTRACT: Well W117 in the Sichuan Basin reveals a suite of ~814 Ma quartz monzonites, unconformably overlain by Sinian clastic and carbonate sediments. The quartz monzonites contain no muscovite and amphibole, and are characterized by high SiO₂ (72.26-77.93%), total alkali, and TFe₂O₃/MgO content, and low P₂O₅ and CaO abundance, with variable A/CNK ratio (0.93-1.19), classified as metaluminous to weakly aluminous highly fractionated I-type granites. They are preserved in the Neoproterozoic rift and exhibit restricted negative ε_Nd(t) values (-7.0 to -5.2) and variable zircon ε_Hf(t) values (-13.9 to 2.3), suggesting their generation via melting of both ancient and juvenile crustal materials in an extensional setting. Their p

SUBMITTER: He DF 

PROVIDER: S-EPMC5624896 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature