Search

[Display omitted] • 140–120 Ma volcanic magmatism is recorded in the SNCC. • Yangtze Craton material occurs beneath the SNCC. • Intense crust-mantle interaction is recorded in the SNCC. This study presents new geochronological and geochemical data for Early Cretaceous volcanic rocks in the southern margin of the North China Craton (NCC), to discuss the crust–mantle interaction. The studied rocks include pyroxene andesites from Daying Formation, hornblende andesites and andesites from Jiudian Formation, and rhyolites from a hitherto unnamed Formation. These rocks formed in Early Cretaceous (138–120 Ma), with enrichment in light rare earth elements (REE), depletion in heavy REE and arc-like trace elements characteristics. Pyroxene andesites show low SiO 2 contents and enriched Sr–Nd–Pb–Hf isotopic compositions, with orthopyroxene phenocryst and Paleoproterozoic (2320–1829 Ma) inherited zircons, suggesting that they originated from lithospheric mantle after metasomatism with NCC lower crustal materials. Hornblende andesites have low SiO 2 contents and high Mg# (Mg# = 100 Mg/(Mg + Fe2+)) values, indicating a lithospheric-mantle origin. Considering the distinct whole-rock Sr isotopic compositions we divide them into two groups. Among them, the low (87Sr/86Sr) i andesites possess amount inherited Neoarchean to Neoproterozoic (2548–845 Ma) zircons, indicating the origin of lithospheric mantle with addition of Yangtze Craton (YC) and NCC materials. In comparison, the high (87Sr/86Sr) i andesites, with abundant Neoarchean–Paleozoic inherited zircons (3499–261 Ma), are formed by partial melting of lithospheric mantle with incorporation of NCC supracrustal rocks and YC materials. Rhyolites have extremely high SiO 2 (77.63–82.52 wt.%) and low total Fe 2 O 3 , Cr, Ni contents and Mg# values, combined with ancient inherited zircon ages (2316 and 2251 Ma), suggesting an origin of NCC lower continental crust. Considering the presence of resorption texture of quartz phenocryst, we propose a petrogenetic model of 'crystal mushes' for rhyolites prior to their eruption. These constraints record the intense crust–mantle interaction in the southern margin of the NCC. Given the regional data and spatial distribution of Early Cretaceous rocks within NCC, we believe that the formation of these rocks is related to the contemporaneous far-field effect of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

• 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]

This paper reports new whole–rock major– and trace–element and zircon U Pb and Hf O isotopic data for Early Cretaceous granitic rocks on Liaodong Peninsula, NE China, with the aim of constraining continental reworking in the northeastern North China Craton. On the basis of SiO 2 , MgO, and Sr contents and Sr/Y values, the rocks can be divided into three groups. The low–Mg adakitic rocks show zircon U Pb ages of (134–120 Ma), and high SiO 2 (67.11–71.14 wt%) and low MgO (0.53–0.62 wt%) contents, and high Sr (531–1108 ppm) contents, Sr/Y (29.3–132) ratios, with enriched Sr–Nd–Hf–O isotopic compositions, indicating an origin of thickened lower mafic crust. The high–Mg adakitic rocks show ages of (126–114 Ma) and are characterized by low SiO 2 (53.11–63.88 wt%) and high MgO (2.07–8.93 wt%) contents, and high Sr (391–1041 ppm) contents, Sr/Y (23.9–64.1) ratios, with relatively depleted Sr–Nd–Hf–O isotopic compositions, suggesting that they were derived from partial melting of delaminated lower mafic crust. The normal granitic rocks show ages of (127–121 Ma) and high SiO 2 (71.65–77.22 wt%) and low MgO (0.10–0.51 wt%) and Sr (12.1–309 ppm) contents, Sr/Y (0.89–24.5) ratios, with relatively depleted Sr–Nd–Hf–O isotopic compositions, suggesting an origin from lower mafic crust with normal crustal thickness. These constraints, combined with the regional occurrence of A–type granites, bimodal igneous rocks, and metamorphic core complexes, as well as the regional distribution of Mesozoic granitic rocks displaying a younging trend from southeast to northwest for the Jurassic rocks but a reverse trend for the Cretaceous rocks, recorded the roll–back of the Paleo–Pacific plate towards the Eurasian continental margin. [Display omitted] • Discovery of Early Cretaceous low– and high–Mg adakitic and normal granitic rocks on Liaodong Peninsula. • Reworking of lower crust with different properties occurred in Liaodong Peninsula. • The subducted Paleo–Pacific plate rolled back during Early Cretaceous. [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]