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Basaltic trachyandesites and trachyandesites from the northern North China Craton (NCC) provide an excellent opportunity to examine the nature of their mantle source and the secular evolution of the underlying mantle lithosphere. In addition, our study of these rocks helps to constrain the age and mechanism of NCC lithospheric destruction. In this paper, we report geochronological, geochemical, and Sr–Nd isotopic analyses of the Niujiaogou (NJG) basaltic trachyandesites and trachyandesites. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U–Pb dating yielded an age of 120.7 ± 0.8 million years, which we regard as the crystallization age of the rocks. Analysed whole-rock samples are enriched in both light rare earth elements and large ion lithophile elements (i.e. Rb, Sr and Ba), but depleted in heavy rare earth elements and high field strength elements (i.e. Nb, Ta, and Ti), with slightly negative to positive Eu anomalies (Eu/Eu* = 0.73–1.09). The NJG basaltic trachyandesites and trachyandesites are characterized by low MgO (2.42–3.69 wt.%), Cr (10.3–24.6 ppm) and Ni (17.1–25.6 ppm), suggesting that they may have originated from an extremely evolved magma. In addition, the rocks display negative eNd (t) values (−12.2 to −8.5), which indicate that they were derived from a common lithosphere mantle that had previously been metasomatized by fluids related to subduction of Paleo-Asian Ocean sedimentary units. This magmatism may have been induced by large-scale, transtensional strike-slip on the Tan-Lu fault zone. In accord with earlier studies, these findings provide evidence that the lithospheric mantle source beneath western Liaoning Province was not changed much by the extensive Mesozoic magmatism during Triassic to early Cretaceous time.

Mafic dolerite dykes form a series of swarms that are widespread across the North China Craton (NCC). We present U–Pb zircon ages, geochemical data, and Sr–Nd–Hf isotopic data for representative samples of the Shaanxi dolerite dykes in the southern NCC. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb zircon analyses for three samples yield ages ranging from 448.1 ± 1.2 to 489.6 ± 0.9 Ma (i.e., Cambro-Ordovician). The dolerites are characterised by a wide range of rock compositions. They display enrichments in light rare earth element (LREEs) and large ion lithophile element (LILE) (i.e., Ba, U, K and Pb), as well as depletion in high field strength (HFSE) (Nb, Ta, Hf and Ti). The mafic dykes have relatively uniform ( 87 Sr/ 86 Sr) i ranging from 0.7049 to 0.7076, ( 176 Hf/ 177 Hf) i from 0.282187 to 0.282236, low e Nd (t) values, from − 4.1 to − 4.9, e Hf (t) values of between − 7.9 and − 9.8, for zircon, and high hafnium model ages (T DM1 = 1366–1535 Ma, T DM2 = 1924–2081 Ma). These results suggest that the dykes are derived by partial melting of an enriched, lithospheric mantle source. The magmas underwent fractionation of olivine, pyroxene, plagioclase, and Ti-bearing phases (rutile, ilmenite, titanite), along with crustal contamination. The formation of the Shaanxi Province, NCC mafic dykes can be attributed to the collision between the NCC and south Qinling Block. Specifically, these magmas formed as a result of crustal thinning in response to extension that followed this collision.

Post-orogenic mafic rocks from Northeast China consist of swarms of dolerite dikes. We report a new U–Pb zircon age, as well as whole-rock geochemical and Sr–Nd–Hf isotopic data. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) U–Pb zircon analysis yielded an age of 210.3 ± 1.5 million years (i.e. Triassic) for these mafic dikes. Most Dalian mafic rocks exhibit low K2O + Na2O contents, and span the border between alkaline and calc-alkaline rock associations in the total alkali–silica diagram. The investigated dikes are also characterized by relatively high (87Sr/86Sr)i ratios (0.7061–0.7067) and negative ϵNd (t) (−4.7 to −4.3) and ϵHf (t) values (−4.1 to −1.1), implying that they were derived from an enriched lithospheric mantle source. The mafic dikes are characterized by relatively low MgO (4.65–5.44 wt.%), Mg# (41–44), and compatible element content [such as Cr (89.9–125 ppm) and Ni (56.7–72.2 ppm)], which are the features of an evolved mafic magma. No evidence supports the idea ...

Mesozoic post-collisional andesites occur in the Gerze area within the Qiangtang Terrane of northern Tibet, China. Geochronological, geochemical, and whole-rock Sr–Nd isotopic analyses were performed on this suite of volcanic rocks to characterize their petrogenesis. Laser ablation-inductively coupled plasma-mass spectrometry U–Pb zircon analyses yielded consistent ages ranging from 122.4 ± 0.4 Ma to 124.4 ± 0.4 Ma for two andesite samples (JC01 and GZ01). The andesites belong to the alkaline and sub-alkaline magma series in terms of K2O + Na2O contents (4.7–10 wt.%), and belong to the high-K calc-alkaline and calc-alkaline series on the basis of their high K2O contents (1.0–3.3 wt.%). The volcanic rocks are further characterized by the enrichment of light rare earth elements [(La/Yb)N = 7.4–11.5] and large-ion lithophile elements (e.g., Rb), slightly negative Eu anomalies (Eu/Eu* = 0.79–0.94), and negative anomalies in high field strength elements (e.g., Nb, Ta, and Ti) relative to primitive mantle. The samples show slightly elevated (87Sr/86Sr)i values that range from 0.7049 to 0.7057, and low eNd(t) values of −3.4 to 0.7. These results suggest that the rocks were derived from a compositionally heterogeneous mantle source and that their parent magmas are basalt magma. The parent mafic magmas may have undergone fractional crystallization of olivine, pyroxene, hornblende, and to a lesser extent, plagioclase during ascent through the thickened crustal pile, with minor or no crustal contamination, before the finally erupting as andesites.

Post-orogenic mafic dikes are widespread across eastern Shandong Province, North China Craton, eastern China. We here report new U–Pb zircon ages and bulk-rock geochemical and Sr–Nd–Pb isotopic data for representative samples of these rocks. LA-ICP-MS U–Pb zircon analysis of two mafic dike samples yields consistent ages of 118.7 ± 0.25 million years and 122.4 ± 0.21 million years. These Mesozoic mafic dikes are characterized by high (87Sr/86Sr) i ranging from 0.7082 to 0.7087, low ϵNd(t) values from −17.0 to −17.5, 206Pb/204Pb from 17.14 to 17.18, 207Pb/204Pb from 15.44 to 15.55, and 208Pb/204Pb from 37.47 to 38.20. Our results suggest that the parental magmas of these dikes were derived from an ancient, enriched lithospheric mantle source that was metasomatized by foundered lower crustal eclogitic materials prior to magma generation. The mafic dikes underwent minor fractionation during ascent and negligible crustal contamination. Combined with previous studies, these findings provide additional evidence ...

Basaltic porphyries from the northeast North China craton (NCC) provide an excellent opportunity to examine the nature of their mantle source and the secular evolution of the underlying mantle lithosphere. In addition, the study helps to constrain the age and the mechanism of NCC lithospheric destruction. In this paper, we report geochronological, geochemical, and Sr–Nd isotopic analyses of a suite of mafic lavas. Detailed laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U–Pb dating yielded an age of 223.3 ± 1.1 million years, which we regard as representing the crystallization age of the basaltic porphyries. The bulk-rock analysed samples are enriched in both large ion lithophile elements (LILEs) (i.e. Ba, Sr, and Pb) and light rare earth elements (LREEs), but depleted in high field strong elements (HFSEs) (i.e. Nb, Ta, Zr, Hf, and Ti) and heavy rare earth elements (HREEs), without significant Eu anomalies (Eu/Eu* = 089–0.98). The basaltic porphyries have undergone low degr...