Formation Age,Geochemical Characteristics and Geological Significance of Ergunahe Formation in Enhehada Area of Erguna Block,China
Ergunahe Formation is an important component of the metamorphic crystalline basement of Erguna Block,recording the Precambrian tectonic evolution history;however,it has small distribution area,poor natural outcrops,and relatively little research.Therefore,the systematic field geological survey of Ergunahe Formation in Enhehada area of Erguna Block combined with LA-ICP-MS zircon U-Pb dating,the characteristics of major and trace elements were analyzed;the formation age,protolith types,material source and sedimentary environments of Ergunahe Formation were explored.The results show that Ergunahe Formation is mainly a set of parametamorphic rocks,the sericite phyllite and chlorite schistose mylonite have similar overall petrogeochemical characteristics,showing rich Si(SiO2 content is 63.45％-79.01％),K(K2O content is 2.22％-3.33％)and Al(Al2O3 content is 9.76％-17.10％);the zircon U-Pb weighted average age is(583.0±1.7)Ma,formed in Neoproterozoic Sinian.The chondrite-normalized REE pattern shows a right-leaning pattern with enrichment of LREE and depletion of HREE,and a insignificant negative Eu anomaly.Trace elements are depleted in high field strength elements Nb,Ti,P,and large ion lithophile elements Ba,Sr,and enriched in high field strength elements Zr,Th,U,Hf,and large ion lithophile element Rb.The material source is dominated by felsic sandstone,with the protolith being sandy mudstone and intermediate-acidic volcanic rocks,indicating low maturity,proximal deposition,and a sedimentary environment of an active continental margin,and the presence of passive continental margin materials.
geochemistryErgunahe Formationmetamorphic rockzircon U-Pb ageErguna BlockXing'an-Mongolian orogenic belt
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