Abstract
The Wuhaolai mafic complex is located in the north margin of the North China Craton (NCC), Inner Mongolia. To discuss the mineralogical features, magma evolution process, and tectonic setting of the complex, we analyzed the geochemical compositions of clinopyroxene and hornblende using an electron probe. The results revealed that the parental magma of this complex belonged to the intraplate alkaline basalt series. The normal zoning texture and the relation between Mg# and FeO, Al2O3, CaO, Na2O, SiO2 and Cr2O3 suggested that the clinopyroxenes of pyroxenite and gabbro crystallized from the same parental magma. The similar CaO content of clinopyroxenes indicated that the parental magma of the Wuhaolai complex may have suffered crustal contamination. Furthermore, the characteristics of hornblende demonstrated that the magma source was modified by fluids derived from subducted slab. Based on the value of Kdcpx (0.23–0.27), the equilibrium melt with clinopyroxene exhibited a relatively low Mg# (43–53), indicating that the parental magma was derived from the lithospheric mantle and underwent crystal fractionation. The gabbro crystallization temperature and pressure was found to be lower than that of pyroxenite, indicating that gabbro was formed at a lower depth than that of pyroxenite. Combining the tectonic setting discrimination diagram of clinopyroxene with the results of previous studies on the late Paleozoic intrusions near the research area, we proposed that the Wuhaolai complex was formed in an intraplate environment. The magma source was modified by fluids derived from the subducted slab during the subduction of the Paleo-Asian Ocean (PAO). After the PAO closure, the parental magma of the Wuhaolai complex was produced by the partial melting of the enriched lithospheric mantle
Highlights
As one of the oldest cratons in the world, the formation of the North China Craton (NCC) can traced back to approximately 1.8 Ga (Zhao et al, 2001; Wilde et al, 2002)
The conclusions of our study are summarized as follows: 1. The parental magma of the Wuhaolai mafic complex belongs to the intra-plate alkaline series
The feature of the normal chemical zoning and the other chemical characteristics documented for clinopyroxene in the studied samples of pyroxenite and gabbro from the Wuhaolai mafic complex are attributed to the crystallization process of the same parental magma
Summary
As one of the oldest cratons in the world, the formation of the North China Craton (NCC) can traced back to approximately 1.8 Ga (Zhao et al, 2001; Wilde et al, 2002). The southward subduction of the Paleo-Asia Ocean (PAO) caused dramatic tectono-magmatic activities during the late Paleozoic in the northern NCC (Davis et al, 2001; Xiao et al, 2003; Zhang et al, 2007a; Ying et al, 2011; Menzies et al, 1993; Wilde et al, 2003; Yang et al, 2008; Wu et al, 2008). Large numbers of the late Paleozoic–early Mesozoic plutonic rocks are distributed along the northern NCC (Pan et al, 1996; Zhang et al, 2007b). There still is a great controversy on the PAO closure time in terms of the spatio-temporal distribution of the ophiolites, multi-stage tectonic deformations, and magmatic activities in the northern NCC margin (Zhao et al, 2011). According to the prevailing hypothesis, the PAO closed in the Ordovician–Silurian (Han et al, 1997; Kheraskova et al, 2003), the Devonian–Late Carboniferous (Shi et al, 2013; Zhao et al, 2013), or the Permian–Late Triassic (Jian et al, 2010; Li et al, 2014a; Li et al, 2014b)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
