scholarly journals Genesis of High-Mg Adakites in the Southeastern Margin of North China Craton: Geochemical and U-Pb Geochronological Perspectives

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuo Zheng ◽  
Yanfei An ◽  
Chunkit Lai ◽  
Hongzhi Wang ◽  
Yunfeng Li
Keyword(s):  
Early Cretaceous ◽  
North China Craton ◽  
North China ◽  
Eastern China ◽  
Parental Magma ◽  
Quartz Diorite ◽  
Underground Mines ◽  
Geodynamic Setting ◽  
Southeastern Margin ◽  
Regional Tectonic

In the eastern North China Craton (NCC), Mesozoic tectonics was dominated by the Paleo-Pacific subduction rollback and the Tanlu crustal-scale fault movement. The regional transtension had generated extensive adakitic magmatism, some Cu-Au ore-forming but others not. To establish the geodynamic setting and any metallogenic link for the adakites from the southeastern NCC margin, we analyzed the ore-barren adakitic rocks from underground mines in the Huaibei-Linhuan coalfield (where surface igneous outcrops are scarce), and compared their ages and geochemistry with other mineralized and ore-barren adakites across Eastern China. Zircon U-Pb dating reveals two magmatic episodes in the Huaibei-Linhuan coalfield: 1) early-Early Cretaceous (ca. 130–129 Ma) (quartz-)diorite and granodiorite, and 2) late-Early Cretaceous (ca. 115.8 and 105.8 Ma) microgabbro and dolerite. Whole-rock geochemistry indicates that the (quartz-)diorite and granodiorite are high-Mg adakitic, featured by low K2O/Na2O (avg. 0.33), high Sr/La (avg. 44.3), and lack of correlation between SiO2 (fractionation index) and Sr/Y (avg. 56.55) and MREE/HREE (avg. 1.09), resembling typical adakites derived from oceanic-slab partial melting. Geochronological correlation with the regional tectonic events suggests that the slab-melting may have been caused by the Paleo-Pacific subduction rollback. Further extension and crustal thinning in the late-Early Cretaceous along the southern Tanlu fault may have formed the gabbro-dolerite in the coalfield. Geochemical comparison suggests that parental magma of the Huaibei-Linhuan adakites may have had similar water content [similar zircon 10,000*(Eu/Eu*)/Y and Eu/Eu* ratios] to typical porphyry Cu-Au ore-forming magmas, yet the former may have been considerably more reduced (lower zircon Ce/Nd and whole-rock V/Sc ratios). We considered that the assimilation of Carboniferous-Permian coal seams in the area may have further lowered the magma fO2 and thus its potential to form Cu-Au mineralization.

Early Cretaceous Xiuyan adakitic granitoids in the Liaodong Peninsula, eastern China: petrogenesis and implications for lithospheric thinning of the North China Craton

2021 ◽  
Vol 58 (1) ◽  
pp. 50-66
Author(s):  
Yang Dong ◽  
Jingdang Liu ◽  
Yanfei Zhang ◽  
Shiyong Dou ◽  
Yanbin Li ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
North China Craton ◽  
Lower Crust ◽  
North China ◽  
Eastern China ◽  
Lithospheric Thinning ◽  
The North ◽  
Magma Sources ◽  
Liaodong Peninsula ◽  
T Values

Mesozoic magmatic rocks are widely distributed in the North China Craton (NCC) and are crucial to understanding the timing, location, and geodynamic mechanisms of lithospheric thinning of the NCC. In this study, we report geochronological, petrogeochemical, and Lu–Hf isotopic data for adakitic granitoids from different parts of Xiuyan pluton in the Liaodong Peninsula, aiming to constrain their magma sources, petrogenesis, and tectonic implications. The adakites are metaluminous to weakly peraluminous and are classified as high-K calc-alkaline I-type granite with Early Cretaceous zircon U–Pb ages of 129–126 Ma. They exhibit adakite-like geochemical characteristics, such as high Sr content and low Yb and Y contents, coupled with high Sr/Y and no pronounced Eu anomalies. They are enriched in Rb, U, and light rare-earth elements and are depleted in Ta, Nb, P, and Ti. The adakites from the eastern part of the pluton have low εHf(t) values (–8.5 to –4.0) with old TDM2 ages (1.57–1.31 Ga), indicating they were derived from the lower crust containing juvenile mantle-derived materials. In contrast, adakites from the northern part of the pluton have lower εHf(t) values (–19.7 to –16.6) with older TDM2 ages (2.21–2.03 Ga), indicating that they were derived mainly from an ancient crust. Our results show that both adakitic magmas were derived from partial melting of delaminated lower crust. Their relatively high MgO and Ni contents and Mg# values indicate that the melts interacted with mantle peridotites. The lower crust delamination beneath the Liaodong Peninsula resulted from paleo-Pacific plate subduction during the Early Cretaceous, which resulted in thinning of Mesozoic crust in the Xiuyan area.

Early Cretaceous extensional allochthons in the Taihang Shan associated with destruction of the North China Craton

2021 ◽  
pp. 104933
Author(s):  
Wuke Chen ◽  
Yi Liufu ◽  
Lei Wu ◽  
Chenyu Zhang ◽  
Hongwei Zhang ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
North China Craton ◽  
North China ◽  
The North

The Early Cretaceous Yangzhaiyu Lode Gold Deposit, North China Craton: A Link Between Craton Reactivation and Gold Veining

2012 ◽  
Vol 107 (1) ◽  
pp. 43-79 ◽  
Author(s):  
J.-W. Li ◽  
Z.-K. Li ◽  
M.-F. Zhou ◽  
L. Chen ◽  
S.-J. Bi ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Early Cretaceous ◽  
North China Craton ◽  
North China ◽  
Lode Gold ◽  
Lode Gold Deposit

scholarly journals Applications of Vitrinite Anisotropy in the Tectonics: A Case Study of Huaibei Coalfield, Southern North China

2012 ◽  
Vol 2012 ◽  
pp. 1-16
Author(s):  
Yudong Wu ◽  
Quanlin Hou ◽  
Yiwen Ju ◽  
Daiyong Cao ◽  
Junjia Fan ◽  
...  
Keyword(s):  
North China ◽  
Vitrinite Reflectance ◽  
Eastern China ◽  
Tectonic Stress ◽  
Deformation Mechanisms ◽  
Thermal Metamorphism ◽  
Regional Tectonic ◽  
Projection Analysis ◽  
Huaibei Coalfield

29 oriented and 10 nonoriented coal samples are collected in the study from three different regions of the Huaibei coalfield, eastern China, and their vitrinite reflectance indicating surface (RIS) parameters are systematically calculated and analyzed. Using the available methods, Kilby’s transformations and RIS triaxial orientations are obtained. The magnitudes and orientations of the RIS axes of the three regions were respectively projected on the horizontal planes and vertical sections. The results show that the samples in high deformed region have significant anisotropy magnitudes (higher Bw/Rmax and Ram values) with a biaxial negative style, whereas the samples in the slightly deformed area have unimpressive anisotropy magnitudes with a biaxial negative style. Thermal metamorphism superposed might enhance the complication and variation of RIS style. RIS projection analysis deduced that the RIS orientation is mainly controlled by regional tectonic stress, and likely influenced by deformation mechanisms of coal.

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