Approximately 1.78 Ga mafic dykes in the Lüliang Complex, North China Craton: Zircon ages and Lu‐Hf isotopes, geochemistry, and implications

Abstract

Mafic dyke swarms are excellent time markers and paleostress indicators. Numerous late Paleoproterozoic mafic dykes are exposed throughout the Trans-North China Orogen (TNCO). Most of these dykes trend NW-SE or NNW-SSE, nearly parallel to the orogen, while a series of E-W trending mafic dykes are restricted in the L€ uliang and southern Taihang areas in the central segment of the TNCO. These dykes were mostly considered to be linked with breakup of the supercontinent Columbia previously. In this study, 16 mafic dykes were investigated in the L€ uliang Complex. Zircon LA-ICP-MS dating of four samples yields magmatic crystallization ages of 1.78-1.79 Ga. These dykes belong to the tholeiite series and consist of basalt, basaltic andesite, and andesite. They are enriched in LREE and LILE and depleted in HFSE, and have negative zircon eHf (t) values of 21.7 to 212.2. The E-W trending mafic dykes show similar geochemical and isotopic features compared to the NW-SE trending dykes in other complexes. They were most likely originated from a lithospheric mantle metasomatized by subduction-related fluids and later emplaced along extensional fractures in a postcollisional setting. NW-SE trending fractures were formed due to gravitational collapse and thinning of the lithosphere. E-W trending fractures in the central segment of the orogen constitute a transverse accommodation belt to equilibrate the different amounts of extension between the northern and southern TNCO. The impact of the postorogenic extension might have continued to approximately 1680 Ma as evidenced by the presence of abundant approximately 1750-1680 Ma anorthositegabbro-mangerite-rapakivi granite suites (AMCG-like) occurring in the northern NCC.

Fluid-Present Partial Melting of Paleoproterozoic Okbang Amphibolite in the Yeongnam Massif, Korea

“…In addition, zircon ε Hf ðtÞ values of basement gneisses in the Yeongnam Massif generally decrease with time at~2.5-2.0 Ga. These variations during the Paleoproterozoic are consistent with the overall variation in zircon U-Pb ages and ε Hf ðtÞ values recorded in igneous rocks of the North China Craton, including the Damiao gabbro-anorthosite suite (Figure 11; [129][130][131][132][133][134]).…”

“…Zircon U-Pb ages and ε Hf ðtÞ values available from Paleoproterozoic gneisses of the Yeongnam Massif[32,35] are also shown in gray diamonds. Gray envelope represents the ranges in U-Pb ages and ε Hf ðtÞ values of zircons compiled from igneous rocks of the North China Craton, including the Damiao gabbro-anorthosite suite[129][130][131][132][133][134]. Evolutionary path of the depleted mantle is based on 176 Hf/ 177 Hf and 176 Lu/ 177 Hf values of Griffin et al[83].…”

Large Igneous Provinces (LIPs) and Anoxia Events in “The Boring Billion”

“…LIPs or major mafic intraplate magmatic events during 1,790-1,750 Ma are very common in many continental blocks including North China, Baltica, Laurentia, Siberia, Northern Australia, Amazonia, São Francisco, Western Africa, East Antarctica, India, and Rio de la Plata (Table 20.A1 in the Appendix to this chapter). The Xiong'er-Taihang LIP in the North China Craton (NCC) is composed of the Taihang dolerite dyke swarm in the central NCC with baddeleyite/zircon U-Pb ages from 1,789 ± 28 Ma to 1,754 ± 71 Ma and the Xiong'er basaltic-andesitic volcanic rocks in the southern NCC with zircon U-Pb ages from 1,783 ± 13 Ma to 1,751 ± 14 Ma (Halls et al, 2000;Peng et al, 2008;He et al, 2009;Peng, 2010;Wang et al, 2014a). The Tomashgorod-AMCG magmatism within the Ukrainian Shield in Baltica consists of mafic dykes and coeval anorthositemangerite-charnockite-granite (AMCG) plutons and minor syenite and kimberlite (Bogdanova et al, 2013, and references therein).…”

“…A = 0.12 Li et al, 2009;Zhang et al, 2012Zhang et al, , 2017aZhang et al, , 2017bWang et al, 2014b;Peng, 2015 A<0.01 Lu et al, 2008b;Xiang et al, 2012;Wang et al, 2015b;Li et al, 2015;Zhang et al, 2015b Xiong'er-Taihang Basalt, andesite, dolerite dyke, with minor rhyolite Xiong'er volcanic rocks: 1,783±13 Ma to 1,751±14 Ma (zircon U-Pb); dolerite dykes: 1,789±28 Ma to 1,754±71 Ma (baddeleyite/zircon U-Pb) A = 0.27 Halls et al, 2000;Peng et al, 2008;He et al, 2009;Peng, 2010;Wang et al, 2014a A = 0.09 Hellström et al, 2004;Söderlund et al, 2005;Ernst et al, 2008 Protogine Zone Dolerite (sill or dyke) A = 0.50 Ronkin et al, 2007Ronkin et al, , 2016Nosova et al, 2012, and references therein;Puchkov et al, 2013, and Ernst et al (2008Ernst et al ( , 2013a, Ernst (2014), and Zhang et al (2018a). Gao et al, 2007Gao et al, , 2008aGao et al, , 2008bSu et al, 2008Su et al, , 2010Sun, 2013;Zhang et al, 2015a;Zhao et al,…”

Magma flow pattern of the 1.78 Ga dyke swarm of the North China Craton during the initial assembly of the Supercontinent Nuna/Columbia: Constraints from rock magnetic and anisotropy of magnetic susceptibility studies

“…Contact margins with the country rocks are well defined, except when occasionally covered by engineering concrete. The dykes have been dated at late Paleoproterozoic times, ranging from 1.79 Ga to 1.77 Ga (see details in Table 1; Halls et al, 2000;Peng et al, 2005;Wang et al, 2014;Yang et al, 2019).…”