Petrogenesis and Geological Significance of Newly Discovered Alkaline Rhyolite in Baerzhe Rare Metal Deposit,Inner Mongolia
To decipher the petrogenesis of the newly discovered alkaline rhyolite in the Baerzhe giant rare metal deposit in Inner Mongolia,and its genetic relationship with the ore-related peralkaline granite and Aliwula alkaline rhyolite from the adjacent area,in this research it carried out high spatial resolution LA-SF-ICP-MS zircon U-Pb dating,mineralogical and whole-rock geochemical studies.The results show that the eruption age of the Baerzhe alkaline rhyolite is 124.4±1.6 Ma,which is obviously younger than that of the Aliwula alkaline rhyolite(141 Ma),which represents a new stage of alkaline volcanic activity in the middle-southern section of the Great Xing'an Range during the Early Cretaceous.The Baerzhe and Aliwula alkaline rhyolites have high SiO2,alkali metals,TFe2O3,F and low Al2O3 contents,and belong to comendites.Both are rich in light rare earth elements(LREE)and high field strength elements(HFSE)such as Nb,Ta,Zr,and Hf,and contain high Rb,Th,U and extremely low Ba and Sr contents.In addition,both have the same whole-rock Nd isotopic composition,with εNd(t)values of 1.6 and 1.7-1.8,respectively.Therefore,both Baerzhe and Aliwula alkaline rhyolites are the products of partial melting of the juvenile lower crust.The Baerzhe alkaline rhyolite and ore-related peralkaline granite have the same formation age and isotope composition,and are different products of same,evolving magmatic system.Given the wider exposure range of volcanic rocks,alkaline volcanic rocks can be used as an important geological prospecting indicator for the underlying rare metal deposits,and it is pointed out that Aliwula area has a good prospecting potential for such deposits.
BaerzheAliwularare metal depositalkaline volcanic rockGreat Xing'an Rangeore deposit geology
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