Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite,rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area,in order to constrain th...Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite,rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area,in order to constrain their genesis and tectonic significance.Zircon LA-ICP-MS U-Pb data indicate that the rhyolite and rhyolitic lithic crystal tuff were formed during 137±5 Ma and 143±1 Ma,respectively.These volcanic rocks have high SiO2(70.03%–76.46%)and K2O+Na2O(8.10%–9.52%)contents,but low CaO(0.03%–0.95%)and MgO(0.07%–0.67%)contents,which belong to the peraluminous and high-K calc-alkaline rocks.They are enriched in light rare earth elements(REEs),and exhibit fractionation of light over heavy REEs,withδEu values of 0.37–0.83.The volcanic rocks are enriched in LILEs(e.g.,Rb,U and K)and depleted in HFSEs(e.g.,Nb,Ti,P and Ta).The chemical composition suggests that these volcanic rocks formed by partial melting of crust material.Combined with previous regional research results,the authors consider that the volcanic rocks of the Manketouebo Formation in the Keyihe area were formed under an extensional environment related to the closure of the Mongolia–Okhotsk Ocean.展开更多
1.Objective Pegmatite hosts important resource of rare metals,e.g.,lithium(Li)and beryllium(Be).In recent years,increasingly more studies were dedicated to characterize and unravel the formation of pegmatite-type depo...1.Objective Pegmatite hosts important resource of rare metals,e.g.,lithium(Li)and beryllium(Be).In recent years,increasingly more studies were dedicated to characterize and unravel the formation of pegmatite-type deposits,for which accurate dating of pegmatite formation and mineralization is essential.The Songpan-Ganzi orogenic belt is a major rare metal metallogenic belt in China,hosting many important pegmatite-type Li deposits,including the Lijiagou,Dangba,Jiajika,Yelonggou,Cuola,and Declalongba.Radiometric age data(mica Ar-Ar and zircon/cassiterite U-Pb)from these Li deposits are sparse,ranging from 210 to 152 Ma.However,obtaining reliable zircon U-Pb dates can be a challenge due to the strong decidualization in pegmatites.As a result,the formation and mineralization ages of these rare metal pegmatites remain controversial,which hampers the development of pegmatite-type metallogenic model for the Songpan-Ganzi orogenic belt.展开更多
基金Supported by Project of National Natural Science Foundation of China(No.41872234)。
文摘Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite,rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area,in order to constrain their genesis and tectonic significance.Zircon LA-ICP-MS U-Pb data indicate that the rhyolite and rhyolitic lithic crystal tuff were formed during 137±5 Ma and 143±1 Ma,respectively.These volcanic rocks have high SiO2(70.03%–76.46%)and K2O+Na2O(8.10%–9.52%)contents,but low CaO(0.03%–0.95%)and MgO(0.07%–0.67%)contents,which belong to the peraluminous and high-K calc-alkaline rocks.They are enriched in light rare earth elements(REEs),and exhibit fractionation of light over heavy REEs,withδEu values of 0.37–0.83.The volcanic rocks are enriched in LILEs(e.g.,Rb,U and K)and depleted in HFSEs(e.g.,Nb,Ti,P and Ta).The chemical composition suggests that these volcanic rocks formed by partial melting of crust material.Combined with previous regional research results,the authors consider that the volcanic rocks of the Manketouebo Formation in the Keyihe area were formed under an extensional environment related to the closure of the Mongolia–Okhotsk Ocean.
基金financially supported by the Geological Survey Project of China Geological Survey(DD20230341)the National Natural Science Funds Integration Project(92262302)。
文摘1.Objective Pegmatite hosts important resource of rare metals,e.g.,lithium(Li)and beryllium(Be).In recent years,increasingly more studies were dedicated to characterize and unravel the formation of pegmatite-type deposits,for which accurate dating of pegmatite formation and mineralization is essential.The Songpan-Ganzi orogenic belt is a major rare metal metallogenic belt in China,hosting many important pegmatite-type Li deposits,including the Lijiagou,Dangba,Jiajika,Yelonggou,Cuola,and Declalongba.Radiometric age data(mica Ar-Ar and zircon/cassiterite U-Pb)from these Li deposits are sparse,ranging from 210 to 152 Ma.However,obtaining reliable zircon U-Pb dates can be a challenge due to the strong decidualization in pegmatites.As a result,the formation and mineralization ages of these rare metal pegmatites remain controversial,which hampers the development of pegmatite-type metallogenic model for the Songpan-Ganzi orogenic belt.
