Middle Silurian -Late Devonian tectonic evolution in the eastern segment of the northern margin of the North China Plate: Evidence from magmatic rocks in Gongzhuling area

In order to better understand the Silurian -Devonian tectonic framework and evolution process in the eastern part of the northern margin of the North China Plate, We conducted LA-ICP-MS zircon U-Pb dating, geochemical, zircon Hf isotope and whole rock Sr-Nd isotope analysis on the Middle Silurian -Late Devonian magmatic rocks ( Fangniugou volcanic rock and Ximanzhang intrusive rock) near the Gongzhuling City, Jilin Province, with the aim of constraining the tectonic setting of the eastern segment of the northern margin of the North China Plate. The zircon LA-ICP-MS U-Pb ages of the meta-andesite, mylonitized rhyolitic crystal tuff and rhyolite in Fangniugou volcanic rocks are 426 +/- 4. 8Ma, 404 +/- 4. 5Ma and 375. 5 +/- 4. 6Ma respectively, represents the crystallization age of their protolith. Combined with previous dating results, Fangniugou volcanic rocks include 426 similar to 425Ma, similar to 419Ma, 404 similar to 400Ma, 390 similar to 384 Ma, similar to 375 Ma multi -stage volcanic events. Fangniugou volcanic rocks are strong structural deformation, and tectonic contact in the rocks. In fact, they are composed of tectonic fragments formed in different times and different tectonic environments. The formation ages of tonalite mylonite and mylonitized tonalite in the Ximangzhang intrusive rock are 419. +/- 5 3. 7Ma and 424. +/- 7 5. 9Ma respectively, representing the crystallization age of tonalite. The Middle -Late Silurian magmatic rocks (426 similar to 419Ma) are a set of calcalkaline to high potassium calc-alkaline tonalite, granodiorite, andesite, dacite, rhyolite and pyroclastic rocks. The intrusive rocks and volcanic rocks are consistent in time, space and provenance, belonging to the homologous volcanic intrusive complex; With positive epsilon(Nd)(t) ( +1. 04 similar to +1. 21) and epsilon(Hf)(t) ( +1. 26 similar to + 7. 85), relatively enriched in Rb, Ba, Th, U, K (LILEs) and light rare earth elements (LREE), and depleted in Nb, Ta, P and Ti ( HFSEs), mainly derived from the partial melting of Meso-Neoproterozoic accretionary lower crust materials ( subduction plates), which were mixed with mantle and lower crust materials in the ascending process and formed in the active continental margin environment. The Early Devonian metamorphic rhyolitic crystal tuff is enriched in Rb, Th, U, K and depleted in Ba, Nb, Ta, Eu, Sr, P and Ti, showing the geochemical characteristics of aluminous A -type granite, which was formed in the extensional environment after the collision between Bainaimiao island arc and North China Plate; positive epsilon(Nd)(t) ( +1. 28 similar to+ 2. 70) and epsilon(Hf) ( ( + 3. 18 similar to + 7. 22), indicating that it originated from the partial melting of the Middle Neoproterozoic accretionary basaltic lower crust material. After the formation of magma, minerals such as plagioclase, apatite and magnetite are separated and crystallized. The Late Devonian mylonitized rhyolite belongs to calc-alkaline I -type rhyolite; Enriched Rb, Ba, Th, U, K, depleted Nb, Ta, Sr, P, Ti, with positive epsilon(Nd)(t) + 6. 08) and epsilon(Hf) (t) + 9. 63 similar to + 13. 39), indicating that it originated from the partial melting of Neoproterozoic-Middle Cambrian accretionary basaltic lower crustal material; Formed in the active continental margin environment, the paleo Asian Ocean plate began to subduct southward.