Petrology Characteristics And Ore-bearing Analysis Of Alkali Feldspar Granites Of Duobaoshan,Heilongjiang

The Duobaoshan alkali feldspar granite pluton is located in Duobaoshan,the northwestn of Heilongjiang Province.Considering the tectonic position,it is Located among the Siberian plate,North China plate and Paleo-Pacific plate,while it belongs to the Zhalantun-Duobaoshan Island Arc Belt?class-??of the Daxing'anling Arc Basin System?class-??,the Tianshan-Xingmeng orogenic system?class-??.The analysis of genesis,tectonic setting and the ore-bearing potential of granite in article is based on the U-Pb isotopic dating and geochemistry of alkali feldspar granite.The following are the major achievements obtained through this study.The result of the U-Pb isotopic dating of zircon is 300.3±2.0Ma?MSWD=0.22?,it suggests that the diagenetic age of the rock body is the later Carboniferous-early Permian of the mid-late Variscan.The alkali feldspar granite is high SiO₂ content?69.70%⁷7.42%?,K₂O content?4.09%⁵.67%?,Na₂O content?3.13%⁴.13%?,rich K and Na;Rittmann Index?=1.84³.55;it turns out that the rock belongs to Peraluminous high-k calc-alkaline series.Calculated by a zircon saturation thermometer,the diagenetic temperature of Duobaoshan alkali feldspar granite is about 850°C;the incompatible elements such as Rb,Th,U,etc.are enriched,while the large lon lithophile elements such as Ba,Sr,Sm,etc.are lossed;The number of?Eu ranges from 0.05 to 0.65,the average of?Eu is0.21;The Y/Nb ratio is 1.25².2,and the average value was 1.62;All of the these proves suggest that the alkali feldspar granite should be A₂-type granite.The trace elements spider web map,rare earth element distribution pattern map and kinds of tectonic setting discrimination diagram suggest that the alkali feldspar granite is a post-orogenic granite formed in the continental margin island arc environment.It is considered that the Duobaoshan area was in the tectonic background of subduction and collision in the late Devonian-Carboniferous period and extensional tectonic background in the Early Permian.The Fe₂O₃/FeO-SiO₂ diagram shows that it may be related to W-Sn mineralization.however,K/Rb ratio,Ti content,REE and REE characteristics of granite indicate that Cu-mo,Au,W-Sn and other metals have poor ore-bearing properties,while their geochemical characteristics are similar to those of Nanling ion-adsorbed-type REE deposit,which may have certain prospecting prospects for REE deposits.