Initial decratonization of the eastern North China Craton: New constraints from geochronology, geochemistry, and Hf isotopic compositions of Mesozoic igneous rocks in the Qingchengzi district

Abstract

Herein, new zircon U-Pb ages, whole-rock major and trace element geochemistry, and Hf isotopes are presented for four Mesozoic granitic rock samples within the Qingchengzi district, eastern China. These data provide precise age and petrogenesis information with respect to the Mesozoic intrusions in the Qingchengzi district, which further constrain the initial decratonization process of the eastern North China Craton (NCC). The zircon U-Pb data reveal that these granitoids are emplaced in the following two stages: Triassic (243-220 Ma) and Middle Jurassic (∼164 Ma). These Mesozoic rocks (lithology: syenogranite, monzogranite, and biotite granite) contain high concentrations of silica (68.94-77.07 wt.%) and total alkali (7.35-9.71 wt.%) together with low concentrations of MgO (0.07-0.98 wt.%), total Fe 2 O 3 (0.81-2.92 wt.%), and CaO (0.17-1.80 wt.%), and they are characterized by an enrichment of large-ion lithophile elements (LILEs; e.g., Rb, Cs, and K) and light rare earth elements (LREEs)in addition to depletion of high-field-strength elements (HFSEs; e.g., Nb, Ta, and Ti) and heavy rare earth elements (HREEs), indicating that these Mesozoic rocks are similar to I-type granitoids. The ε Hf (t) values of the magmatic zircons in these granitoids range from −18.7 to −11.4. Such geochemical characteristics indicate that these granitoid formations were generated by the partial melting of the ancient lower crustal material. However, the occurrence of mafic microgranular enclaves in the Shuangdinggou monzogranite implies the mixing of the mantle-derived magmas.Combined with the results of the previous research, these new data indicate that initial decratonization of the eastern NCC occurred during the Triassic period in response to the collision and amalgamation of the Yangtze Craton and NCC. During the Jurassic, the dynamic mechanism of lithospheric thinning was overprinted owing to the subduction of the Paleo-Pacific Plate. Furthermore, cratonic destruction reached its peak during the Early Cretaceous, which could be related to the asthenospheric upwelling induced by the rollback of the subducting oceanic slab.[Correction added on 21 October 2019, after first online publication: Funding information has been added.]

Paleoproterozoic Adakitic Rocks in Qingchengzi District, Northeastern Jiao-Liao-Ji Belt: Implications for Petrogenesis and Tectonism

“…Detailed lithologic and structural features can be seen in Li et al [44,45]. There are many magmatic events from Paleoproterozoic to Mesozoic in this district, which intruded into Precambrian strata ( Figure 2) [43][44][45]. In this study, the Paleoproterozoic magmatic rocks were collected from the central part of a dike and adjacent isolated large-scale batholith (southeastern) ( Figure 2).…”

“…During the test, we selected two international standard material samples (Canadian diorite gneiss SY-4 and kinzingite SARM-45) as calibration standards (listed in Supplementary Table S2). The analytical precision was better than 5% for the major elements and better than 10% for the trace elements [43].…”

“…The Eastern Block also includes two blocks (Longgang and Namgrim), which are separated by the JLJB (~1.95 Ga; Figure 1b,c) [3,4]. The collage-aggregation of several microcontinent blocks was accompanied by the formation of important tectonic/orogenic belts (i.e., KB, JLJB, and TNCO) that marked the completion of cratonization, and then the craton was in a long-term stable stage until the occurrence of few magmatic events in Mesozoic [43].…”

“…The standard lead correction was based on the Andersen [49] method. For detailed experimental procedures and parameters, please see Li et al [43,44].…”

“…The 176 Hf/ 177 Hf ratio determined for the GJ-1 standard zircon was 0.282001 ± 0.000015 (n = 27). For detailed experimental operating conditions, procedures, and parameters, please refer to Geng et al [50] and Li et al [43].…”