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• 1813–1789 Ma A-type granites were identified in southern NCC. • A-type granites originated from partial melting of TTG of Taihua Complex. • The A-type magmatism was in respond to the breakup of Columbia supercontinent in post-collisional setting. A-type granites are produced commonly in extensional settings and they are important proxies to track breakup of continent. Here we report systematic studies on geochronology and geochemical features of A-type granites in Songxian–Ruyang region, southern margin of the North China Craton (NCC), in order to constrain their petrogenesis and tectonic implications. Zircons from these granites show oscillatory zoning and high Th/U ratios (0.12 to 1.26), indicating a magmatic origin. LA–ICP–MS zircon U–Pb dating shows that they were emplaced at 1813 to 1789 Ma, indicating that they were formed in late Paleoproterozoic. Geochemically, these rocks are high in SiO 2 (67.51–74.42 wt%) and total alkalis (Na 2 O + K 2 O = 7.76–10.19 wt%), and low in MgO (0.09–1.31 wt%), CaO (0.09–1.11 wt%) and P 2 O 5 (0.12–0.26 wt%) contents, with negative Nb, Ta, Sr, P and Ti anomalies. They are characterized by high FeOT/(MgO + FeOT), 10000 Ga/Al ratios (1.57–3.15) and Zr + Nb + Ce + Y contents (566–835 ppm). They are also characterized by high calculated Zr saturation temperatures (892–918 °C), high Ti-in-zircon temperatures (693–912 °C) and metaluminous to weakly peraluminous natures, which are typical features of aluminous A-type granites, further belonging to the A 2 granites. The low zircon ε Hf (t) values (–13.8 to –8.6), along with the low whole rock ε Nd (t) values (–8.62 to –6.10) and low apatite ε Nd (t) values (–8.31 to –6.56), indicate that the Songxian–Ruyang A-type granites were derived from partial melting of the calc-alkaline tonalitic–trondhjemitic–granodioritic gneisses in Taihua Complex, and they were formed in post-collisional extensional setting. Combined with coeval regional granitoids, the south margin of the NCC is in a continuous extensional setting during 1.8–1.6 Ga, and the Songxian–Ruyang A-type granites can represent a response of the breakup of Columbia supercontinent. [ABSTRACT FROM AUTHOR]

• 1.85–1.80 Ga plagiogranites were identified in the JLJB. • The late Paleoproterozoic plagiogranites were formed by partial melting of high-T hydrated oceanic crust. • The JLJB was an arc–continent collision belt during the Paleoproterozoic. Paleoproterozoic plagiogranites were identified in the Gaoliduntai area of the Jiao–Liao–Ji Belt (JLJB), North China Craton (NCC). We conducted a geochronological, geochemical, isotopic, and mineral chemical investigation of the plagiogranites to constrain their petrogenesis and tectonic implications. The Gaoliduntai plagiogranites yielded zircon U–Pb ages of 1802 ± 10, 1828 ± 18, and 1853 ± 11 Ma, indicating emplacement at the late Paleoproterozoic. Geochemically, They are characterized by high SiO 2 and Na 2 O, and low K 2 O and TiO 2 contents, with low total rare earth element (REE) concentrations. They also exhibit enrichment in light REEs and large-ion lithophile elements (e.g., Cs, Rb and Sr), and depletion in heavy REEs and high-field-strength elements (e.g., Nb and Ta). The plagiogranites show varying initial 87Sr/86Sr ratios (0.7012–0.7053), whole-rock ε Nd (t) values (–8.23–+1.15) and apatite ε Nd (t) values (–4.78–+3.30), with whole-rock 206Pb/204Pb (t) (14.223–16.733), 207Pb/204Pb (t) (15.310–15.644) and 208Pb/204Pb (t) (35.310–35.998) values, indicating a depleted mantle source modified with an enrichment component. Zircons in the plagiogranites have positive ε Hf (t) values (+1.0 to +6.4) and T DM2 (Hf) ages of 2408–2078 Ma. Zircons δ18O compositions (2.1‰ to 4.5‰) are lower than the zircons from normal mantle but show similar features to typical plagiogranites. Furthermore, the plagioclases in these plagiogranites are albite (Ab = 95–99). These features lead us to propose that the Gaoliduntai plagiogranites formed by partial melting of high-temperature mafic oceanic crust, with contributions from delaminated crustal components. We suggest that the Paleoproterozoic Gaoliduntai plagiogranites provide evidence of the involvement of ancient oceanic crust in the tectonic evolution of the JLJB. Based on regional geological features and previous studies, we propose that the JLJB was an arc–continent collision belt during the Paleoproterozoic, and that the Gaoliduntai plagiogranites formed in an extensional tectonic setting. [ABSTRACT FROM AUTHOR]

Apatite is widely utilized to reflect the character and petrogenesis of the parental felsic magma. The compositional variation of apatite from mafic rocks and its applicability to the record of whole-rock are still not well understood. In this study, we present the in situ geochemical analysis of apatite from two types of mafic rocks in the northeastern North China Craton (amphibole-rich mafic rocks for group 1, and pyroxene-rich mafic rocks for group 2). All apatite samples display typically right-sloping rare earth element (REE) patterns, with enrichment in light REE relative to heavy REE, and homogeneous Nd isotopic compositions, suggesting a magmatic origin. Higher apatite REE contents in mafic rocks of group 2 than those of group 1 show a different crystallization sequence in apatite. Extensive apatite crystallization in amphibole-rich mafic rocks, occurs earlier than in pyroxene-rich mafic rocks. The magma differentiation is responsible for the low apatite REE concentrations in group 1 mafic rocks. Combined with previous apatite data, both apatite REE patterns and compositional variations in mafic rocks are mainly controlled by the composition of the original melt. The crystallization of titanite before apatite impoverishes melts in the apatite-compatible trace elements (e.g., middle REE), whereas the crystallization of plagioclase concurrently with apatite can cause some subtle compositional variations of Sr and light REE. Apatite in mafic rocks exhibits higher Sr concentrations than in felsic rocks, which is most likely attributed to the weakening extent of the plagioclase crystallization. [Display omitted] • Apatite compositions in mafic rocks mainly depend on the parental melt. • Apatite grains from appinite crystallize earlier than those from gabbro. • The crystallization of mineral phases can cause apatite compositional variations. [ABSTRACT FROM AUTHOR]

This paper reports new whole-rock major and trace element, Sr Nd isotopic, and zircon U Pb and Hf O isotopic data for Late Triassic intrusive rocks on Liaodong Peninsula, NE China, aiming to constrain the petrogenesis of these rocks in terms of lithospheric thinning in the northeastern North China Craton (NCC). New zircon U Pb data indicate that the rocks were emplaced during the Late Triassic (220–211 Ma). Based on petrology, petrography and geochemistry, we divided these rocks into three groups. The Group 1 rocks, including hornblende gabbro, hornblende diorite and mafic vein, show low SiO 2 , Na 2 O + K 2 O and high MgO contents, with (87Sr/86Sr) i (0.7066–0.7071), ε Nd (t) (−10.6 to −5.7), ε Hf (t) (−16.6 to +1.5), and δ18O (7.06‰–7.82‰) values, indicating that they were formed by partial melting of lithospheric mantle with addition of lower continent crust materials. The Group 2 rocks, including syenites, display high SiO 2 , Na 2 O + K 2 O and low MgO contents, with (87Sr/86Sr) i (0.7064–0.7073), ε Nd (t) (−14.8 to −14.5), ε Hf (t) (−11.7 to −5.7), and δ18O (5.49‰–6.37‰) values, indicating they were originated through partial melting of lithospheric mantle with continent crust materials added, coupled by fractional crystallization of mafic minerals. The Group 3 rocks, including monzogranite and syenogranite, show high SiO 2, Na 2 O + K 2 O and low MgO contents, with different isotopic signatures: the former shows (87Sr/86Sr) i (0.7085–0.7087), ε Nd (t) (−17.0 to −16.8), ε Hf (t) (−17.9 to −4.4) and δ18O (6.10‰–6.95‰) values. The latter shows higher ε Nd (t) (−9.0 to −8.1), ε Hf (t) (−3.4 to +1.2) and lower δ18O (5.52‰–7.29‰) values. Combined with the adakitic features of monzogranite and different two model ages, we believe they were derived from partial melting of ancient thickened lower crust and juvenile crust, respectively. Together with the spatial and temporal distribution of the Late Triassic rocks, we believe that these rocks were related to the collision between NCC and Yangtze Craton, and the initiation of lithospheric thinning of NCC in eastern segment began in Late Triassic. Unlabelled Image • Late Triassic intrusive rocks on Liaodong Peninsula were formed between 220 and 211 Ma. • These rocks were formed after the collision between NCC and YC. • Lithospheric thinning of northeastern NCC began at ~220 Ma. [ABSTRACT FROM AUTHOR]