Objective The Great Xing’an Range is located in the eastern Central Asian Orogenic Belt and contains a Mesozoic volcanic belt that crops out over an area of 100, 000 km^2,dominating the Mesozoic stratigraphy of the G...Objective The Great Xing’an Range is located in the eastern Central Asian Orogenic Belt and contains a Mesozoic volcanic belt that crops out over an area of 100, 000 km^2,dominating the Mesozoic stratigraphy of the Great Xing’an Range.展开更多
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
大兴安岭南段西沙拉地区出露大量的中生代新民组(J_(2)x)和满克头鄂博组(J_(3)m)地层,由于其岩石组合中流纹岩的存在,易混淆地层的划分,导致该流纹岩的地层归属存在争议。因此,以流纹岩为研究对象,进行锆石U-Pb测年,地球化学特征分析,...大兴安岭南段西沙拉地区出露大量的中生代新民组(J_(2)x)和满克头鄂博组(J_(3)m)地层,由于其岩石组合中流纹岩的存在,易混淆地层的划分,导致该流纹岩的地层归属存在争议。因此,以流纹岩为研究对象,进行锆石U-Pb测年,地球化学特征分析,并开展了新民组和满克头鄂博组地层剖面对比研究,进而探讨流纹岩的形成时代、构造背景及地层归属问题。研究指出西沙拉流纹岩的地球化学特征为高硅(SiO_(2)平均含量为75.74%)、富碱(Na_(2)O+K_(2)O平均含量为7.69%),并且镁、钙含量较低,属过铝质、高钾钙碱性系列;球粒陨石标准化的稀土元素配分模式呈右倾型,轻稀土元素相对富集,重稀土元素相对亏损,(La/Yb)N介于10.61~14.21,显示出较强的负铕异常(δEu介于0.44~0.53);大离子亲石元素(large ion lithophilic elements,LILE)Rb、Ba和K相对富集,同时高场强元素(high field strength elements,HFSE)Nb、Ta和Ti相对亏损,这说明岩浆起源于地壳物质;LA-ICP-MS锆石U-Pb测年结果显示流纹岩年龄为(167.7±2.6)Ma,形成于中侏罗世,是蒙古-鄂霍茨克洋闭合后伸展构造作用所形成的产物;结合区域地质、剖面岩石组合类型对比研究认为该流纹岩应归属为满克头鄂博组。展开更多
基金jointly supported by the National Key Research and Development Program of China (grants No. 2018YFC0603806 and 2017YFC0601506)the Geological Survey Project of the China Geological Survey (grants No. DD20160050 and 12120114086201)
文摘Objective The Great Xing’an Range is located in the eastern Central Asian Orogenic Belt and contains a Mesozoic volcanic belt that crops out over an area of 100, 000 km^2,dominating the Mesozoic stratigraphy of the Great Xing’an Range.
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.
文摘大兴安岭南段西沙拉地区出露大量的中生代新民组(J_(2)x)和满克头鄂博组(J_(3)m)地层,由于其岩石组合中流纹岩的存在,易混淆地层的划分,导致该流纹岩的地层归属存在争议。因此,以流纹岩为研究对象,进行锆石U-Pb测年,地球化学特征分析,并开展了新民组和满克头鄂博组地层剖面对比研究,进而探讨流纹岩的形成时代、构造背景及地层归属问题。研究指出西沙拉流纹岩的地球化学特征为高硅(SiO_(2)平均含量为75.74%)、富碱(Na_(2)O+K_(2)O平均含量为7.69%),并且镁、钙含量较低,属过铝质、高钾钙碱性系列;球粒陨石标准化的稀土元素配分模式呈右倾型,轻稀土元素相对富集,重稀土元素相对亏损,(La/Yb)N介于10.61~14.21,显示出较强的负铕异常(δEu介于0.44~0.53);大离子亲石元素(large ion lithophilic elements,LILE)Rb、Ba和K相对富集,同时高场强元素(high field strength elements,HFSE)Nb、Ta和Ti相对亏损,这说明岩浆起源于地壳物质;LA-ICP-MS锆石U-Pb测年结果显示流纹岩年龄为(167.7±2.6)Ma,形成于中侏罗世,是蒙古-鄂霍茨克洋闭合后伸展构造作用所形成的产物;结合区域地质、剖面岩石组合类型对比研究认为该流纹岩应归属为满克头鄂博组。
