Petrogenesis and tectonic implications of the Early Cretaceous Dagushan adakitic porphyries in the Anshan area,North China Craton  

作　　者：Xiaohui Sun Haoshu Tang Yan Luan 

机构地区：[1]Key Laboratory of Western China’s Mineral Resources and Geological Engineering,MOE,School of Earth Science and Resources,Chang’an University,Xi'an 710054,China [2]State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China

出　　处：《Acta Geochimica》2022年第1期24-38,共15页地球化学学报（英文）

基　　金：jointly supported by the National Natural Science Foundation of China(Nos.41872085,41503035);the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2019JM-160,2017JM4006);Fundamental Research Funds for the Central Universities(300102271201)。

摘　　要：The eastern part of the North China Craton suffered significant lithospheric thinning since the Mesozoic,and petrogenesis of the Dagushan adakitic diorite porphyries provides an excellent opportunity to investigate the lithospheric thinning mechanism and geodynamic setting.The zircon LA-ICP-MS U–Pb geochronology reveals that the representative Dagushan adakitic porphyry was formed at 120.5±0.5 Ma.The Dagushan diorite porphyries are characterized by the relatively high contents of SiO_(2)(64.25–65.70 wt%),Al_(2) O_(3)(15.00–15.38 wt%),Sr(333–491 ppm),low contents of Y(6.50–10.3 ppm),and Yb(0.57–0.85 ppm),and resultant high Sr/Y(47–57)and La/Yb(37–55)ratios,exhibiting geochemical characteristics of typical adakites.Moreover,the relatively high Mg O contents(MgO=2.23–2.29 wt%)and Mg numbers(Mg^(#)-=54–56)of the Dagushan adakitic rocks imply that the pristine adakitic magma interacted with mantle peridotite.However,the zircon Hf isotopic signatures(εHf(t)=-19.0 to-28.0;TDM2=2378–2944 Ma)suggest an ancient lower crustal source.Therefore,it is proposed that the Dagushan adakitic rock was probably generated by partial melting of delaminated lower crust which was triggered by the Tan-Lu Fault Zone,and the interaction of pristine adakitic magma with mantle peridotite during the ascent finally generated the Dagushan high Mg^(#)adakitic rocks.It is suggested that delamination was an important mechanism for lithospheric thinning of the NCC.

关 键 词：Diorite porphyry ADAKITE Lower crust Delamination NCC 

分 类 号：P534.53[天文地球—古生物学与地层学] P548[天文地球—地质学]