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

发布时间：2018-04-10 11:12

本文选题：流体包裹体 + 熔体包裹体　；参考：《地质学报》2017年05期

【摘要】：福建永定大坪铌钽矿化花岗斑岩体位于永定县城南部的大石凹-蓝地火山喷发盆地,对斑岩型铌钽矿床的产出具有重要的指示意义。本文通过岩相学、显微测温和激光拉曼等实验对大坪岩体ZK10001和ZK10401钻孔不同深度岩石样品中的流体和熔体包裹体进行了研究,试图揭示岩体的熔体-流体演化过程,分析铌钽等成矿元素的富集机制。观测结果表明,大坪岩体主要发育气液两相盐水溶液包裹体和硅酸盐熔体包裹体。流体包裹体均一温度集中在175～225℃,盐度集中在3%～7%NaCleq,密度集中在0.75～0.95g/cm~3,成矿流体主要为中低温、低盐度和低密度的流体,总体属于H_2O-NaCl体系。熔体包裹体主要分布于石英斑晶雪球结构的环带中,含有钠长石、石英和钽铁矿等子矿物。熔体包裹体完全均一温度较高,能够代表早期原始岩浆的组成。研究表明,大坪岩体的原始岩浆富铌钽等成矿元素和碱性组分,大坪岩体的铌钽矿化是岩浆高度分异的产物,铌钽的富集过程经历了斑晶阶段和基质阶段等两阶段结晶分异过程:在早期斑晶结晶阶段,少量铌钽矿物与斑晶一起结晶,并被斑晶包裹;岩浆演化晚期发生流体出溶现象,但未分异出大量流体,F等挥发分促进了铌钽在结晶残余熔体中富集,并在基质间隙中沉淀。大坪矿化岩体的存在指示出斑岩型铌钽矿床存在的可能性。
[Abstract]:The daping niobium and tantalum mineralized granitic porphyry is located in the Dashiao-Landi volcanic eruption basin in the southern part of Yongding County Fujian Province which is of great significance for the occurrence of porphyry type niobium-tantalum deposits.In this paper, the fluid and melt inclusions in the rock samples of different depths in the ZK10001 and ZK10401 boreholes of the Daping rock mass have been studied by means of petrography, microthermometry and laser Raman experiments in order to reveal the melt-fluid evolution process of the rock mass.The enrichment mechanism of niobium tantalum and other metallogenic elements is analyzed.The results show that the gas-liquid two-phase salt solution inclusions and silicate melt inclusions are mainly developed in the Daping rock mass.The melt inclusions are mainly distributed in the ring zone of quartz porphyry snowball structure and contain subminerals such as albite quartz and tantalite.The melt inclusions have a high homogenization temperature and can represent the composition of the early primitive magma.The results show that the ore forming elements and alkaline components of the original magma are rich in niobium and tantalum, and the mineralization of niobium and tantalum in the Daping rock body is the result of the high differentiation of magma.The enrichment process of niobium and tantalum experienced two stages of crystallization and differentiation: in the early phase of porphyry crystallization, a small amount of niobium and tantalum minerals were crystallized together with the porphyry and were encapsulated by the porphyry, and fluid exsolution occurred in the late stage of magma evolution.However, a large amount of volatiles, such as F, promoted the enrichment of niobium and tantalum in the residual melt and precipitated in the matrix interstice.The existence of Daping mineralized rock mass indicates the possibility of the existence of porphyry type niobium tantalum deposit.
【作者单位】：中国地质科学院矿产资源研究所;中国冶金地质总局第二地质勘察院;中国地质大学地球科学与资源学院;
【基金】：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
【分类号】：P618.79;P618.86

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