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Alkaline intrusions in the eastern Shandong Province consist of quartz monzonite and granite. U-Pb zircon ages, geochemical data, and Sr-Nd-Pb isotopic data for these rocks are reported in the present paper. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb zircon analyses yielded consistent ages ranging from 114.3 ± 0.3 to 122.3 ± 0.4 Ma for six samples of the felsic rocks. The felsic rocks are characterised by a wide range of chemical compositions (SiO = 55.14-77.63 wt. %, MgO = 0.09-4.64 wt. %, FeO = 0.56-7.6 wt. %, CaO = 0.40-5.2 wt. %), light rare earth elements (LREEs) and large ion lithophile elements (LILEs) (i.e., Rb, Pb, U) enrichment, as well as significant rare earth elements (HREEs) and heavy field strength (HFSEs) (Nb, Ta, P and Ti) depletion, various and high (Sr/Sr) ranging from 0.7066 to 0.7087, low ε (t) values from −14.1 to −17.1, high neodymium model ages (T = 1.56-2.38Ga, T = 2.02-2.25Ga), Pb/Pb = 17.12-17.16, Pb/Pb = 15.44-15.51, and Pb/Pb = 37.55-37.72. The results suggested that these rocks were derived from an enriched crustal source. In addition, the alkaline rocks also evolved as the result of the fractionation of potassium feldspar, plagioclase, +/− ilmenite or rutile and apatite. However, the alkaline rocks were not affected by crustal contamination. Moreover, the generation of the alkaline rocks can be attributed to the structural collapse of the Sulu organic belt due to various processes. [ABSTRACT FROM AUTHOR]

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 that intense lithospheric thinning beneath eastern Shandong occurred at ∼120 Ma, and that this condition was caused by the removal/foundering of the lithospheric mantle and lower crust. [ABSTRACT FROM PUBLISHER]

The ages and source of early Precambrian mafic dykes in western Shandong Province, North China Craton (NCC), were determined using geochronological, and whole-rock geochemical, and whole–rock Sr–Nd isotopic data. U–Pb dating of zircons by laser ablation–inductively coupled plasma-mass spectrometry yields weighted average 207 Pb/ 206 Pb ages of 2514 ± 11 Ma, 2526 ± 8 Ma, and 2505 ± 7 Ma for three dykes. The dykes are classified as alkaline dolerites, and belong to the shoshonitic series. These dolerites are characterized by low concentrations of the light rare earth elements, negligible Eu anomalies, positive Rb, Ba, U, K, Pb, and Sr anomalies, and depletions in high field strength elements. In addition, the mafic dykes have depleted initial ( 87 Sr/ 86 Sr) i and high ε Nd (i) values. Collectively, these data suggest that the mafic dykes were derived from the partial melting of a depleted mantle source, that of the mantle that was hybridized during interaction with continental crust or sediments from the subducted block/plate. The parental mafic magmas of these dykes underwent the fractional crystallization of olivine, pyroxene, hornblende, and Fe–Ti oxides during ascent, with negligible evidence for crustal contamination prior to emplacement at a high crustal level. The mafic magmas were emplaced to form swarms of dykes in response to lithospheric extension, which affected the NCC ~ 2.55 Ga, during the late Neoarchaean. [ABSTRACT FROM AUTHOR]