地质学报2025，Vol.99Issue(4)：1274-1288,15.DOI:10.19762/j.cnki.dizhixuebao.2023086
北秦岭高耀—官坡地区锡及稀有金属伟晶岩年代学、地球化学特征及地质意义
Cassiterite U-Pb age,geochemistry and their geological implications of Sn-rare metal pegmatites in Gaoyao-Guanpo area,northern Qinling tectonic belt
摘要
Abstract
The junction area between Henan and Shaanxi provinces in the northern Qinling tectonic belt is a significant region for pegmatitic uranium and rare metal mineralization in China.Recent discoveries of the Huoyangou Sn-Nb-Ta deposit and the Dadonggou Sn-Li-Ta polymetallic deposit highlight the area's substantial potential for Sn and rare metal mineralization.This study investigates the petrographic,geochemical,and cassiterite LA-ICP-MS U-Pb dating characteristics of mineralized pegmatites from Huoyangou and Dadonggou to determine the metallogenic age,source characteristics,and tectonic setting of these ore-bearing pegmatites.Cassiterite U-Pb dating reveals ages of 410.4±3.1 Ma and 428.8±8.3 Ma for the ore-bearing granitic pegmatites,indicating formation during the Late Silurian and Early Devonian.These pegmatites are characterized by enrichment in aluminum minerals such as muscovite,with a high corundum content in CIPW standard minerals(averaging 4.24％)and an aluminum saturation index(A/CNK)value of 1.35,displaying strong peraluminous characteristics.The pegmatites are enriched in Li,Rb,Cs,and Ta,with a low Nb/Ta ratio(averaging 5.43),and exhibit a negative correlation between Y and Rb,indicating characteristics of S-type granite.Low CaO content(averaging 0.36％),low LREE content(9.02×10-6 on average),and Zr/Hf value(9.44 on average),along with CaO/Na2O＜0.3,enrichment in Rb and Ta,and depletion in Ba,Th,and Sr,suggest an origin from the dehydration and melting of lower crustal metamorphic mudstone.The pegmatites contain volatile-rich magmatic characteristic minerals such as tourmaline,lithium pyroxene,and apatite,as well as highly differentiated granitic characteristic minerals such as cassiterite,niobium-tantalite,and beryl.The high differentiation index(DI)(averaging 93.15),enrichment in Rb and Cs,and depletion in Ba indicate a high degree of crystalline differentiation.Integrating these geochemical characteristics with regional tectonic evolution,we propose that these pegmatites formed in a post-orogenic,relatively stable tectonic environment.They exhibit a magmatic evolution relationship with Late Silurian granite bodies such as Huanglongmiao and Luoziping,representing the highly differentiated and evolved peraluminous granite magma derived from the dehydration and melting of metamorphic mudstone in the lower crust.关键词
锡石U-Pb定年/地球化学/花岗伟晶岩/锡及稀有金属/北秦岭Key words
cassiterite U-Pb dating/geochemistry/granitic pegmatite/Sn and rare metal/northern Qinling tectonic belt引用本文复制引用
蔡文春,田科,高峰,杨宗永,张小明,吴应忠,鲁麟,王天毅,张炳林,姚肖博..北秦岭高耀—官坡地区锡及稀有金属伟晶岩年代学、地球化学特征及地质意义[J].地质学报,2025,99(4):1274-1288,15.基金项目
本文为陕西省公益性地质调查项目(编号202104,202301,202401)和陕西省自然科学基础研究计划——一般项目(青年项目)(编号2022JQ—276)联合资助的成果. （编号202104,202301,202401）
