Geochronological and geochemical constraints on the coexistent N-MORB- and SSZ-type ophiolites in Babu area (SW China) and tectonic implications
Published on 2018-02-16T10:42:06Z (GMT) by
Our detailed geological, geochemical and geochronological investigations indicate the coexistence of late Paleozoic (270–265 Ma) normal middle ocean ridge basalt (N-MORB)-type and suprasubduction-zone (SSZ)-type ophiolites in the Babu area (SW China). Metaperidotite samples from the Babu ophiolites show high Os concentrations and low Re/Os, <sup>187</sup>Os/<sup>188</sup>Os and <sup>187</sup>Re/<sup>188</sup>Os ratios, and represent residual upper mantle. Metagabbro and metabasalt samples show light rare earth element (LREE)-depleted REE patterns and N-MORB-like primitive mantle-normalized spider diagrams without Nb–Ta and Zr–Hf anomalies,and depleted Sr–Nd isotopic compositions (ε<sub>Nd</sub>(<i>t</i>) = +6.9 – +8.3). These geochemical and Re–Os–Sr–Nd isotopic data show that the Babu ophiolites are derived from a depleted mantle source and represent ancient N-MORB-like oceanic crust. In addition, peridotites, basalts and boninites with SSZ signatures (e.g. Nb–Ta negative anomalies) were also reported in the Babu ophiolites consistent with their generation in a forearc or arc setting. In combination with the arc-related high-Mg<sup>#</sup> limburgite, basalt and andesite, these late Paleozoic ultramafic–mafic rocks are genetically related to Paleotethyan subduction, rather than being Emeishan mantle plume related. The coexisting N-MORB- and SSZ-type ophiolites in the Babu area show similar geochemical and geochronological characteristics to the Jinshajiang–Ailaoshan–Song Ma ophiolites.
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Liu, Huichuan; Peng, Touping; Guo, Xiaofei (2018): Geochronological and geochemical constraints on the coexistent N-MORB- and SSZ-type ophiolites in Babu area (SW China) and tectonic implications. Geological Society of London.