摘要
为查明在内蒙古巴尔哲超大型稀有稀土金属矿区新发现的碱性流纹岩岩石成因,及其与碱性花岗岩成矿岩体、以及邻区阿里乌拉碱性流纹岩的成因联系,开展了锆石U-Pb定年、矿物学和全岩地球化学研究.结果表明,巴尔哲碱性流纹岩喷发年龄为124.4±1.6 Ma,明显年轻于阿里乌拉碱性流纹岩(141 Ma),代表了大兴安岭中南段早白垩世新一期碱性火山岩活动.巴尔哲和阿里乌拉碱性流纹岩具有较高的SiO_(2)、碱金属、TFe_(2)O_(3)、F和较低的Al_(2)O_(3)含量,均归属于钠闪碱流岩.两者均富集轻稀土元素(LREE)和Nb、Ta、Zr、Hf等高场强元素(HFSE),含有较高的Rb、Th、U和极低的Ba、Sr含量.另外,两者具有相同的全岩Nd同位素组成,ε_(Nd)(t)值分别为1.6和1.7~1.8.因此,巴尔哲和阿里乌拉碱性流纹岩均为新生地壳部分熔融的产物.巴尔哲碱性流纹岩与碱性花岗岩成矿岩体形成时代和同位素组成均一致,应属同一岩浆体系不同演化阶段的产物.鉴于火山岩出露范围更广,碱性火山岩可以作为深部稀有稀土金属矿床的重要地质找矿标志,并指出阿里乌拉地区具有该类金属矿产较好的找矿潜力.
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 middlesouthern section of the Great Xing’an Range during the Early Cretaceous.The Baerzhe and Aliwula alkaline rhyolites have high SiO_(2),alkali metals,TFe_(2)O_(3),F and low Al_(2)O_(3) 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 ε_(Nd)(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.
作者
淡凯波
张道涵
栾钰薇
宋崇宇
于淼
刘常伟
Dan Kaibo;Zhang Daohan;Luan Yuwei;Song Chongyu;Yu Miao;Liu Changwei(Luoyang Luanchuan Molybdenum Industry Group Co.,Ltd.,Luanchuan 471000,China;School of Earth Resources,China University of Geosciences,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China;China Geological Survey Development Research Center,Beijing 100037,China;Beijing Institute of Geological Hazard Prevention,Beijing 100120,China;The Inner Mongolia Chifeng Geological Mineral Exploration and Development Co.,Ltd.,Chifeng 024005,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2024年第4期1324-1338,共15页
Earth Science
基金
国家自然科学基金项目(No.42072093).
