Geochemical constraints on the origin of Early Cretaceous alkaline intrusions and its tectonic implication, Sulu Orogeni
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ORIGINAL ARTICLE
Geochemical constraints on the origin of Early Cretaceous alkaline intrusions and its tectonic implication, Sulu Orogenic Belt, Eastern North China Craton Shen Liu1 • Caixia Feng1 • Yan Fan1 • Kairui Tai1 • Tianjing Gao1 Ian M. Coulson2
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Received: 18 May 2020 / Revised: 15 July 2020 / Accepted: 29 July 2020 Ó Science Press and Institute of Geochemistry, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Post-orogenic alkaline intrusions from the Sulu Orogenic Belt of eastern North China Craton consist of A-type granites. In this study, we report U–Pb zircon ages, geochemical data, Sr–Nd–Pb, and zircon Hf isotopic data for these rocks. The LA-ICP-MS U–Pb zircon analyses yield consistent ages ranging from 127.1 ± 2.4 to 119.5 ± 4.8 Ma for four samples. The alkaline rocks are characterized by high total alkalis (K2O ? Na2O = 8.32–10.11 wt%), light rare-earth element enrichment, and heavy rare-earth element depletion, with a wide range (La/ Yb)N values (20–48), moderate negative Eu anomalies (Eu/ Eu* = 0.50–0.74), enrichment in large-ion lithophile elements (LILEs, i.e., Rb, Th, U and Pb), and depletion in Ba, Sr and high field strength elements (HFSEs, i.e., Nb, Ta, and Ti), high (87Sr/86Sr)i ranging from 0.708 to 0.7089, low eNd (t) values from -19.4 to -16.8, (206Pb/204Pb)i = 16.751 – 16.935, (207Pb/204Pb)i = 15.381-15.535, (208Pb/204Pb)i = 37.472–37.838, negative eHf (t) values between -21.3 and -25.7 for the magmatic zircons, and larger TDM2 model ages from 2.5 to 2.8 Ga. These results suggest that the rocks were derived from a common enriched lithospheric mantle source that was metasomatized by foundered lower crustal eclogitic materials before magma generation. Furthermore, the geochemical and isotopic feature implies that the primary magma of these rocks originated through partial melting of ancient lithospheric mantle that was variably hybridized by melts derived from & Shen Liu [email protected] 1
State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
2
Solid Earth Studies Laboratory, Department of Geology, University of Regina, Regina, SK S4S 0A2, Canada
lower crust eclogite. These rocks in this study may have been generated by subsequent fractionation of potassium feldspar, plagioclase, ilmenite, and/or rutile. However, negligible crustal contamination occurred during the diagenesis process. Keywords Post-orogenic magmatism Alkaline rocks Contamination Sulu Orogenic Belt North China Craton
1 Introduction As a typical Archaean craton, the North China Craton (NCC) exhibits distinct characteristics from other cratons (Menzies et al. 2007; Griffin et al. 1998; Menzies and Xu 1998; Xu et al. 1998a, b; Fan et al. 2000; Zheng et al. 2001, 2006; Gao et al. 2002, 2004; Zhang et al. 2002, 2003; Wu et al. 1998, 2003, 2005a, b, 2006; Chen et al. 2004; Wilde et al. 2004; Zhai et al. 2007). For example, strong lithospheric destruction has occurred since the Mesozoic. Nevertheless, there are still many cont
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