Zircon U/Pb dating and Hf-O isotopes of the Zhouan ultramafic intrusion in the northern margin of the Yangtze Block, SW China: Constraints on the nature of mantle source and timing of the supercontinent Rodinia breakup

Abstract

The Zhouan ultramafic intrusion in the northern margin of the Yangtze Block is mainly composed of lherzolite. Zircon grains selected from lherzolite are irregular in shape with distinct oscillatory and sector zoning and have Th/U ratios ranging from 0.8 to 10.6, indicating a magmatic origin.

Geochemistry and zircon ages of mafic dikes in the South Qinling, central China: evidence for late Neoproterozoic continental rifting in the northern Yangtze block

“…SIMS zircon U-Pb data of this study constrain the emplacement time of the mafic dikes at ca. 650 Ma, which is contemporaneous with the cycle 3 magmatism in the Yaolinghe Group (Yan et al 2004;Xue et al 2011;Wang et al 2013). Hence, the mafic dikes in the South Qinling belong to the youngest magmatic cycle (~680-650 Ma) in the South Qinling.…”

“…Furthermore, late Neoproterozoic ultramafic-mafic magmatism was identified along the northern margin of the Yangtze block, represented by the Duchongshan and Zhou'an intrusions. Rocks from this unit are mainly composed of troctolite and lherzolite and were demonstrated to be formed between 650 and 635 Ma (Xue et al 2011;Wang et al 2013). From this data it was conjectured that mafic magmatism both in the northern Yangtze and the South Qinling was related to the breakup of Rodinia (e.g., Ling et al 2008;Zhang et al 1999bZhang et al , 2001Zhou et al 1998b).…”

“…The Yaolinghe Group predominately consists of basaltic lavas with minor mafic tuffs, interbedded with silicic volcanic rocks and fine-grained sedimentary rocks (Wang et al 2013;Bader et al 2013). The rocks were subjected to greenschist-facies metamorphism.…”

“…Zircon U-Pb dating has placed a maximum deposition age of the sedimentary rocks at ca. 680 Ma (Wang et al 2013) and eruption ages between 620 and 820 Ma for the volcanic rocks (e.g., Li et al 2003c;Ling et al 2008). It has been demonstrated that the Yaolinghe meta-volcanic sequence consists of three magmatic cycles (Zhu et al 2014).…”

Geochronological and geochemical evidence for the nature of the Dongling Complex in South China

“…(Zheng et al, 2004(Zheng et al, , 2007bChen et al, 2007;Wang et al, 2010b), the occurrence of low ␦ 18 O magmas due to hightemperature water-rock interactions since ∼780 Ma (Zheng et al, 2004(Zheng et al, , 2007aWu et al, 2007;Tang et al, 2008), and the development of rifting sequences in marginal basins since at least 800 Ma (Wang and Li, 2003). The extensional setting continued to at least about 630 Ma, which is evidenced by the development of bimodal volcanism in the Yaolinghe Group (Liu and Zhang, 2013) and ultramafic magmatism in the northern part of the Yangtze craton (Wang et al, 2013d). Thus, the sedimentary protolith of the Dongling rocks are unambiguously controlled by an extensional setting during its deposition at 730-635 Ma.…”