The Geochemistry And Geological Significance Of Neoarchean Granite In Nanxin-Sishui Area Of Shandong Province

This paper is based on the field geological survey,combined with major and trace elements,analysis of rare earth,U-Pb dating of single grain zircon,and other research methods.It studies some aspects of the regional background,geological characteristics,petrographic character,geochemical characteristic,petrogenesis and geological significance of the reserach area.It includes medium-grained biotite monzogranite of Tiaohuayu unit,fine-grained biotite monzogranite of Qiuziyu unit,and fine-grained syenogranite of Xinanling unit.The average of SiO₂of Tiaohuayu unit is 73.51%.The average of Al₂O₃is 12.84%,of K₂O is 12.84%,which means it's rich in potassium and aluminum.The average of A/CNK is 1.54,so the rock is peraluminous.The average of Ritterman index is 2.15,which more inclines to calcium-alkaline.The average of DI is 88.04,which means the degree of differentiation is good.The standard curve of chondrite of rare earth element reveals they are rich in LREE and lack of HREE,with higher fractionation between LREE and HREE.The average of?Eu is 0.81,which amounts to 0.84 of crust-mantle type granite.The type of accessory minerals is zircon-apatite type.This unit belongs to I-type granite.The average of SiO₂of Qiuziyu unit is 69.76%.The average of Al₂O₃is 15.04%,of K₂O is 3.80%,showing the characteristics in aluminum-rich and potassium.The average of A/CNK is 1.52,so the rock is peraluminous.The average of Ritterman index is 2.77,which more inclines to calcium-alkaline.The average of DI is 85.73,which means middling differentiation.The standard curve of chondrite of rare earth element reveals they are rich in LREE and lack of HREE,with higher fractionation between LREE and HREE.The average of?Eu is 0.75,which amounts to the less than 0.6 of crust-transformed type granite.Major accessory mineral is zircon,apatite,pyrite,magnetite,hematite and so on.The type of accessory minerals is zircon-apatite type.This unit belongs to S-type granite.The average of SiO₂of Xinanling unit is 64.24%.The average of Al₂O₃is 17.72%,of K₂O is 6.89%,showing the characteristics in aluminum-rich and potassium.The average of A/CNK is 1.32.The average of Ritterman index is 7.21,which more inclines to alkaline.The average of DI is 90.14,which means middling differentiation and medium crystallization differentiation.They are rich in LREE and lack of HREE,which have not special“V”-font of the standard curve of chondrite,with medium fractionation between LREE and HREE.The average of?Eu is 0.97,which has an unconspicuous europium anomalies.The type of accessory minerals is magnetite type.This unit belongs to S-type granite.The uranium-lead age of the Qiuziyu unit was 2567±7.4 Ma.From Tiaohuayu unit to Qiuziyu unit,the role of the mantle is diminishing,which reflects the evolution of the lateral crustal flow,and marks the gradually formation of crystalline basement.