Petrogenesis of Early Cretaceous intermediate-felsic dikes in the Jiaodong Peninsula, south-eastern North China Craton: Constraints from geochronology, geochemistry and Sr-Nd-Pb-Hf isotopes

Abstract

Early Cretaceous dike swarms are widely developed in the Jiaodong Peninsula, NE China. In this study, we newly investigated the spatial-temporal distribution, petrography, geochronology and whole-rock geochemistry of the intermediate-felsic dikes from the Jiaobei terrain and the Sulu orogenic belt in the Jiadong Peninsula. The zircon U-Pb dating has constrained the timing of the emplacement of intermediate-felsic dikes to 128-108 Ma. The quartz diorite dikes in Jiaobei show adakitic geochemical features, including high SiO 2 (66.3-67.5 wt.%) contents and high Sr/Y (76-149) and La/Yb (41-91) ratios. The combination of a series of isotopic data, including initial 87 Sr/ 86 Sr ratios (0.7098-0.7104) and negative ε Nd (t) (-20.1 to-14.7) and zircon ε Hf (t) values (-19.9 to-9.5), indicates that these quartz diorite dikes were likely derived from partial melting of thickened ancient lower crust with involvement of underplated mafic magmas. Additionally, the diorite dikes in Jiaobei and those in Sulu show similar chemical compositions, as both yield the high-Mg andesite (or andesitic rocks) (HMAs) characteristics with a high Mg # value (60-72), high MgO, Cr, and Ni contents, and low Na 2 O (average = 3.25 wt.%) contents. They also exhibit crustal geochemical signatures, such as depletion in Nb, Ta, and Ti, but enrichment in Th and U; high initial 87 Sr/ 86 Sr ratios (0.7063-0.7094), and low ε Nd (t) (-16.7 to-9.6) and ε Hf (t) values (-29.4 to-9.8). The entire geochemical evidences imply that they derived from the partial melting of mantle wedge peridotite metasomatized by hydrous fluids from the subduction of the oceanic slab with marine sediments. In combination with the Early Cretaceous intrusions and mafic dikes at Jiaodong, the intermediate-felsic dikes represent a magmatic response to lithospheric thinning resulted from the prolonged thermo-mechanical-chemical erosion processes caused

Origin of Low‐Angle Ductile/Brittle Detachments: Examples From the Cretaceous Linglong Metamorphic Core Complex in Eastern China

“…They are all considered to be synkinematic plutons with respect to the MCC. Early Cretaceous dikes in the MCC give dates of 142–108 Ma (Deng et al, 2017; Guan et al, 1998; Liu et al, 2018; Ma et al, 2014; this study; Table 3), and the dike activity was initiated before the formation of the MCC. The low‐angle and subhorizontal shear zones only occur in the northern part of the MCC that contains the 130–127 Ma plutons.…”

“…They are alkali, porphyritic monzonitic granite derived from partial melting of lower crust with weak crust‐mantle interaction (Li et al, 2019). These plutons contain a series of diabase, diorite, granite, and pegmatite dikes that strike mainly NE‐SW to NNE‐SSW and yielded zircon U‐Pb ages in the range of 158 to 110 Ma (Deng et al, 2017; Guan et al, 1998; Liu et al, 2018; Ma et al, 2014; this study).…”

Origin of the dioritic porphyrite and its associated Matouniu skarn gold polymetallic deposits in the Eastern Hebei Province, North China: Evidence from geochronology, geochemistry, and C–O–S–Pb–Hf isotopes

“…(Hou et al, 2013;Ma et al, 2013). In the same way, the presence of amphibole in residue and under high pressure (≥1.2 GPa) (Liu, Deng, et al, 2018;Rapp, Shimizu, & Norman, 2003), while plagioclase maintains stability at depths less than$50 km (1.5 GPa) (Patiño Douce, 2005;Patiño Douce & Beard, 1995). We, therefore, inferred that the dioritic porphyrite was generated by the partial melting of mafic lower crust with plagioclase ± amphibole ± garnet as a residual phase, suggesting that partial melting occurred at sufficient depths (40-50 km) and under relatively high pressure (1.2-1.5 GPa), and that a thick crustal root was present under the northern margin of the NCC during the Late Jurassic.…”

“…Liu et al, 2016;Liu, Shao, et al, 2018;Shi et al, 2015;Shi et al, 2019;Song et al, 2016;Xiong, 2017;Zhang et al, 2017;Zhang et al, 2020). The carbon and oxygen isotopes of the quartz inclusions and hydrothermal carbonates in the gold deposits in the study area indicated that the source of carbon in the fluids of the main metallogenic stage was mainly the deep-seated magmatic source (Kong et al, 2015;Liu et al, 2016;Liu, Deng, et al, 2018;Shi et al, 2015;Xiong, 2017).…”

“…Xue, Santosh, Tsunogae, As discussed in Section 6.2, the Matouniu dioritic porphyrite was generated by the partial melting of mafic lower crust with plagioclase ± amphibole ± garnet in a residual phase, implying that the thickness of the crust was $40-50 km (Liu, Deng, et al, 2018;Patiño Douce, 2005;Patiño Douce & Beard, 1995;Rapp et al, 2003). However, previous study revealed that the Early Jurassic ($177 Ma) crustal thickness of the eastern NCC was <32 km (e.g., Xu et al, 2004).…”