The Metamorphic Supracrustal Rocks In The Weihai Area:Its Geological Characteristics And Tectonic Significances

The geotectonic location of the Jiaodong area is located at the edge of the continental subduction collision zone between the northern margin of the North China plate and the South China plate,and the continental margin of the ancient Pacific plate subduction to the Eurasian continent,including the eastern margin of the North China plate and the northern section of the Sulu UHP metamorphic belt.The Sulu UHP metamorphic belt is located between the North China Plate and the South China plate;it is the product of the mid-late Triassic subduction collision of these two plates.It is a key areas to study the subduction collage of the North China-South China plate and related continental dynamics.The northwest boundary position of the Sulu UHP belt is still a controversial hot issue,and there have been relatively large differences.Regional surveys show that there are a series of metamorphic supracrustal rocks in the Sulu UHP belt,there are still many problems about their structural affinity and the age of original rock and metamorphism.On the basis of summarizing and summarizing the research results of the predecessors,this paper samples the metamorphic supracrustal rocks in the North Sulu Weihai area,and carries out the petrography and zircon U-Pb isotope geochronology analysis.Through the characteristics of the age spectrum to define the original rock and metamorphic age of the metamorphic supracrustal rocks,and the properties of the provenance area are discriminated to determine its structural affinity,and finally define the northwestern boundary of the Sulu UHP belt.The results of this study indicate that the metamorphic supracrustal rocks in Weihai and Wuji area is North China plate affinity,and its original rock age should be around 2068±23 Ma,and experienced two-stage metamorphism events of ~1861 Ma and ~1830 Ma;The metamorphic supracrustal rocks in Haiyangsuo area is South China plate affinity and experienced metamorphic events from 1689 to 1769 Ma.The Triassic metamorphic age were not measured in the five samples,indicating that the metamorphic supracrustal rocks did not participate in the subduction-collision-exhumation mechanism of the North China-South China Plate during the Triassic Period;the metamorphic supracrustal rocks in Weihai area and the Jingshan Group in Jiaobei have very good contrast and similarity in terms of petrography,chronology and tectonic affinity,it is believed that the metamorphic supracrustal rocks in the North Sulu Weihai area and the Jingshan group in Jiaobei belong to the same set of metamorphic supracrustal rocks series,the Mesozoic tectonic action caused some of the Jingshan group in the Jiaobei area to be pushed to the northern margin of the South China plate,which is now the North Sulu Weihai area;Due to the mixed structure,the Weihai area both exposes rocks with the basement properties of the North China plate and the South China plate.Therefore,the Wulian-Yantai fault cannot be absolutely as the boundary of the North China plate and the North Sulu UHP metamorphic belt,and the northwestern boundary of the Sulu UHP belt may not be a simple fault,this paper tends to the northwestern boundary of the Sulu UHP belt is located between the Wulian-Yantai and Mishan fault,it's a tectonic melange belt with a certain width.