地质学报2017，Vol.91Issue(5)：1052-1065,14.
福建永定大坪铌钽矿化花岗斑岩体的流体演化对铌钽富集的制约
Constraints of Fluid Evolution on Nb and Ta Enrichment of the Daping Granite Porphyry in Yongding, Fujian
摘要
Abstract
The Daping granite porphyry intrusion with Nb-Ta mineralization locates in the Dashiao-Landi volcanic basin in the south of Yongding,Fujian,which is of certain indicating significance for the existence of porphyry Nb-Ta deposit.In order to reveal melt-fluid evolution and enrichment mechanism of Nb and Ta,fluid and melt inclusions in the rock samples from different depths of drilling ZK10001 and ZK10401 were investigated by means of petrography,microthermometric experiments and laser Raman spectroscopy.Aqueous two-phase inclusions and silicate melt inclusions present dominantly in Daping intrusion.The homogenization temperatures,salinities and densities of fluid inclusions mainly vary from 175 ℃ to 225 ℃,from 3％ to 7％ NaCl equivalent and from 0.75 g/cm3 to 0.95 g/cm3,respectively.The ore-forming fluid of Daping intrusion is characterized by medium-low temperature,low salinity and low density,roughly belonging to the H2O-NaCl system.Melt inclusions which contain albite,quartz and tantalite are mainly distributed in snowball texture in quartz phenocrysts.Homogenization temperatures of melt inclusions are relatively high,which implies that they can represent primitive magma.This study shows that the primitive magma of the Daping intrusion was rich in Nb,Ta and alkaline components and the Daping intrusion with Nb-Ta mineralization was the product of highly fractionated magma.Enrichment process of Nb and Ta can be divided into two stages:phenocrysts formation in deep process and matrix formation in shadow process.At the early stage of phenocryst crystallization,minor amount of niobium-tantalum minerals crystallized along with crystallization of phenocrysts,with some wrapped by phenocrysts.At the late magmatic stage,small volume of fluids exsolved.Volitiles such as F promote the enrichment of niobium and tantalum in residual melt and precipitated within matrix interstice.Occurrence of the Daping mineralized rocks is indicative of possibility of existence of porphyry-type Nb-Ta deposits.关键词
流体包裹体/熔体包裹体/铌钽/大坪斑岩体/福建永定Key words
fluid inclusion/melt inclusion/Nb-Ta/Daping granite porphyry/Yongding County in Fujian Province引用本文复制引用
刘永超,李建康,邹天人,江善元,丁欣,王娴..福建永定大坪铌钽矿化花岗斑岩体的流体演化对铌钽富集的制约[J].地质学报,2017,91(5):1052-1065,14.基金项目
本文为国家重点研发项目(编号2016YFC0600204),国家自然科学基金项目(编号41372088),中央级公益性科研院所基本科研业务费专项基金(K1409),中国地质调查局地质调查项目(编号DD20160056,DD20160055)联合资助成果. （编号2016YFC0600204）
