Rock Combinations And Zircon U-Pb Geochronology Of The Sujifang Metamorphosed Supracrustal Rocks Within Kangbo County,Northern Hebei Province And Its Geological Implications

The northern part of the Kangbao area of northern Hebei is located on the northern edge of the northern part of the northern margin of the North China Craton.The Sujifang metamorphosed supracrustal rocks is located in Sujufang,Yihusai,Dongjingzi and other places in Kangbao County,they are distributed along the northeast,southeast,and west directions in the region,the Sujifang metamorphosed supracrustal rocks are mainly composed of sillimanite-garnet-biotite gneisses,garnet-quartzo-feldspathic paragneisses,graphitic marbles,Among them,the graphitic marble is overlaid on the sillimanite-garnet-biotite gneisses,and the garnet-quartzo-feldspathic interspersed with rock masses along the direction of gneiss.The main minerals of sillimanite-garnet-biotite gneisses is quartz,plagioclase,K-feldspar,biotite,garnet,sillimanite,etc,The sillimanite is distributed in the form of a short column around the garnet or needle-like inside the garnet.The mineral chemical characteristics indicate that the terminal components of the garnet are Almandine and Pyrope,and potassic feldspar is mainly microclase feldspar,mostly from the type-semi-self-type short columnar.Plagioclase brand An(27.31~33.58),mainly for the oligoclase and feldspar.The Zircon U-Pb Geochronological studies have shown that the zircon edge of the sillimanite-garnet-biotite gneisses in the Sujifang metamorphosed supracrustal rocks' s zircons are metamorphic hyperplasia zircon and the nuclear zircons are detritus zircon,It formed an age of 1903±6.3Ma,and the protolith of sillimanite-garnet-biotite gneisses should be a sedimentary rock,Sedimentary rocks were deposited between 1903 and 1971 Ma and began to degenerate;The zircon of graphitic marble in Sujifang metamorphosed supracrustal rocks is a metamorphic-proliferating zircon in the marginal part of the zircon,the nuclear part is inherited from zircon.The age of formation is 1857±11Ma,and the deposition is finished between 1857~2040Ma and begins to degenerate.Combine with the characteristics of rock composition and chronological basis of the combination of Sujifang metamorphosed supracrustal rocks,Contrasting with the Khondalite series in the Liangcheng area in the south of the Chicheng-Chongli-Shangyi fault zone,we can find that there are great similarities in mineral composition and age assignment between the Sujifang metamorphosed supracrustal rocks and the Khondalite series in Liangcheng area.Therefore,the metamorphosed supracrustal rocks in the Sujiafang area can be re-determined and divided into the Khondalite series,this set of formations and the Khondalite series in the Liangcheng area in the south can be classified into the same set of strata.In addition,the division of the Khondalite belt can extend from the Chicheng-Chongli-Shangyi fault zone to the northeast direction to the Kangbao area.The formation period of this fault zone is also limited to 1857~1903Ma.