Genesis And Tectonic Setting Of Late Paleozoic Metamorphic Sedimentary Rocks In Shangyi,Northhebei Province,China

Shangyi metamorphic rocks in northern Hebei are located on Western North Margin of North China Craton,which has a E-W extending in general,and mainly distributed in the Chaoligai?Haobaogou ?Huangtuyao?wushijia?It mainly consists of the?including garnet?biotite plagioclase gneiss and serpentine marble and metamorphic sandstone?The main rock stratigraphic unit is volcano?including garnet?biotite plagioclase gneiss are interbeded,serpentine marble and metamorphic sandstone lenticular output,but the length of size,for a few meters to thousands of meters??including garnet?biotite plagioclase gneiss are gray,the gneissic structure,metacrystal structure,matrix for fine scale granoblastic texture.?including pomegranate?biotite plagiogneiss main minera are plagioclase?35%?,quartz?35%?,biotite?20%?,and a small amount of garnet?5%?,amphibole?1%?and graphite?3%?.The chemical composition of biotite is not high,all of which are high iron biotite.The majority of plagioclase is feldspar,and some of them are feldspar,and there is no zonal development?An=22.79-34.66?.Garnet is mainly composed of Alm?55.43%⁶5.62%?,Spe?15.36%-29.8%?,Pyr?8.36%-13.34%?,Gro?2.39%-7.58%??Some garnets have compositional zoning.The main mineral assemblages are plagioclase?35%?,quartz?35%?,biotite?20%?,and a small amount of garnet?about 5%?,amphibole?1%?and graphite?3%??The chemical compositions of biotite change little,all of them are high iron black mica.Plagioclase?An=22.79-34.66?is mostly feldspar,few of which are middle feldspar and undeveloped zones.Garnet is mainly composed of iron aluminum garnet?Alm=55.43%-65.62%?,manganese aluminum garnet?Spe=15.36%-29.8%?,and magnesium garnet?Pyr=8.36%-13.34%?and a small amount of calcium aluminum garnet?Gro=2.39%-7.58%?.Some garnets have compositional zoning.Serpentine marble is gray,white,blocky structure and medium grained granular crystalline structure.The main mineral assemblages are calcite?65%?and serpentine?30%?,while minor minerals are olivine?2%?and gold mica?3%?.The metamorphic feldspar quartz sandstone is grey,brown and grey,blocky structure and medium granular crystalline structure.The main mineral assemblages are quartz?70%?and potassium feldspar?micro Plagioclase 10%?.Minor minerals include biotite?5%?,Plagioclase?5%?and Muscovite?3%?.?Including pomegranate?change plagiogneiss SiO₂ content of biotite is large,between 63.56%-77.34% and Al2O3 with high content?13.15%-15.82%?.The content of Na2 O was?2.35%-3.3%?,and the content of MgO was?1.23%-3.12%?.The content of CaO is between 1.91%-3.35%.The trace elements of Rb,the average content of Cs was 78 × 10-6,5.2 × 10-6,were significantly lower than the average value of the crust?average values of Rb,Cs in the earth's crust were 150× 10-6,30 × 10-6?,Ba,the average content of Sr was 409 × 10-6,614 × 10-6,were higher than the average in the crust value?average values of Ba,Sr in the earth's crust were 0.05× 10-6,40 × 10-6?.The contents of high field elements Zr,Hf,Nb and Ta are lower than the average values of corresponding elements in the crust.The Hf isotope is basically equal to the mean value in the crust,and the Zr/Hf ratio is lower than the mean value in the crust?Zr/Hf=66.7?.The total REE??REE?of Shangyi metamorphic sedimentary rocks is not varied,which is 84.03×10-6-171.21× 10-6.Chondrite normalized REE patterns show that LREE is enriched and HREE flat,and most of the samples have mild negative Eu anomalies,and few Eu anomalies are absent.The range of its delta EuCN value is 0.81-0.95.The range of?La/Yb?CN values of rock samples is relatively large,ranging from 4.98-24.72 to 2.28-6.26,and the ratio of LREE/HREE is low.?Including pomegranate?of detrital zircons from the biotite plagioclase gneiss of the U-Pb age,with multiple age values,with Neoarchean,Paleoproterozoic and Mesoproterozoic,early Middle Ordovician,late Ordovician and Early Devonian and Early Carboniferous and Late Carboniferous to early Permian,shows that the diversity of detrital zircon provenance.The measured metamorphic zircon Concordia age of 262.4±4.4 Ma,show that the garnet biotite plagioclase gneiss metamorphic age of late paleozoic.Detrital zircon age data serpentinized marble has Neoarchean,Paleoproterozoic and Mesoproterozoic Middle Permian and Early Permian,that diversity has the characteristics of the source area of Shangyi serpentinized marble in detrital zircon.The protolith of the serpentine marble was formed after 280.9 Ma.The detrital zircon metamorphic feldspar quartz sandstone in the ancient age,including the Neoarchean Paleoproterozoic and mesoproterozoic.The protolith of metamorphic quartz sandstone should be formed after Mesoproterozoic?1776Ma?.According to the results of Bhatia and Crook studies,the protolith formation environment is between the island arc environment and the oceanic island arc environment,and may be closer to the former.Display by Simonin graphic?including pomegranate?,biotite plagiogneiss in arenaceous sedimentary rocks to argillaceous sedimentary rock area,located in the transition from the sandy sedimentary rocks to argillaceous sedimentary rock area?The molar ratio of Al/?Al+Fe+Mn?of the sample in the study area is bet ween 0.76-0.86,the average value is 0.81,and the ratio of W?Al?/W?Al+F e+Mn?is between 0.61-0.75 and the average value is 0.67.So?including garne t?biotite plagioclase gneiss protolith material is the source of terrigenous detrit us.At the same time,its sedimentary environment is located on the continental margin.?containing garnet biotite plagioclase gneiss?of the?Ce/ Ce*?CN = 0.697-1.001?average 0.868?,between the ocean basin?0.55?and continental mar gin?0.90-1.30?,and the latter is more similar to the characteristics of rare eart h elements.Therefore,it can be inferred that the protolith of metamorphic sedi mentary rocks in the Shangyi loess kiln should be argillaceous?or argillaceous?sandstone,which is a terrigenous clastic rock formed in the late Paleozoic,pr obably formed in the continental island arc environment.