Late Neoproterozoic meta-gabbro in northeastern margin of the Yangtze Block: Magmatism related to late breakup of the Rodinia

Abstract

<p>Late Neoproterozoic tectonic evolution of the Yangtze Block is crucial for better understanding the breakup of Rodinia. The reported mafic magmatism related to the breakup event mainly distributed in the northwestern margin of the Yangtze Block. For the first time this study found a Late Neoproterozoic meta-gabbro pluton in the northeastern margin of the Yangtze Block. By means of petrography, zircon U-Pb geochronology, geochemistry and zircon Hf isotope, the formation age, petrogenesis and tectonic setting of the meta-gabbro pluton were determined and discussed. Dating results show that the pluton was formed at 642-636 Ma, reflecting an important magmatic event during the late Neoproterozoic. Geochemical characteristics indicate a tholeiite series for the meta-gabbro rocks, with positive anomalies of Th, La, Pb, Nd and negative anomalies of Nb, Ta, Zr, which are similar to intraplate basalts contaminated by the crust. The zircon 176Hf/177Hf ratios range from 0.282356 to 0.282563, with epsilon Hf(t) values ranging from + 0.74 to + 1.44. The two-stage Hf model ages range from 1289 Ma to 1748 Ma. Magma source of the meta-gabbro was mainly derived from an enriched mantle, which was evolved from the lithospheric mantle metasomatized by slab-derived melts and contaminated by a small amount of lower crust materials during magma ascent. Together with regional tectonics, we inferred that the meta-gabbro pluton was formed under the setting of intracontinental rift. Our result not only enriches the late Neoproterozoic magmatic activity events in the northern margin of the Yangtze Block, but also provides new evidence for the block involved in the late breakup of the Rodinia.<br></p>