投稿时间：2022-12-13
修订日期：2023-02-15
网络发布日期：2023-07-08
中文摘要:大兴安岭南段维拉斯托大型稀有金属-锡多金属矿床的成矿岩体从深部的中粒花岗岩向上逐渐过渡为斑状细粒碱长花岗岩，记录了岩浆演化的不同阶段。为查明铌铁矿族矿物成分、结构变化及其与岩浆演化过程的耦合关系，文章对采自不同深度的3种类型花岗岩（中粒花岗岩、石英斑晶不具雪球结构的斑状细粒富云母碱长花岗岩和具雪球结构的斑状细粒碱长花岗岩）中的铌铁矿族矿物进行了详细的电子探针成分分析和元素面扫工作。维拉斯托矿床铌铁矿族矿物主要为铌铁矿，发育渐变环带结构，从核部到边部Ta含量增加，且斑状细粒富云母碱长花岗岩和斑状细粒碱长花岗岩铌铁矿族矿物边部的铌铁矿、铌锰矿相较于幔部和核部的铌铁矿，其Ta含量具有明显的组分间隔；铌铁矿族矿物Mn/(Fe+Mn)原子比具有多种演化趋势，与分离结晶的矿物相和流体交代作用有关。中粒花岗岩和斑状细粒富云母碱长花岗岩中的铌铁矿结晶于岩浆阶段，斑状细粒碱长花岗岩中的铌铁矿族矿物结晶于岩浆-热液过渡阶段。其中，斑状细粒富云母碱长花岗岩铌铁矿边部Ta含量增加与铁锂云母的分离结晶作用有关，斑状细粒碱长花岗斑岩铌铁矿族矿物边部Ta含量的突变与岩浆-热液过渡阶段的水硅酸盐液体中Ta溶解度的增加有关。斑状细粒碱长花岗岩石英斑晶中共生的熔体包裹体和流体包裹体表明，石英斑晶的雪球结构形成于熔-流体共存的岩浆-热液过渡阶段，出溶的富钨流体交代铌铁矿族矿物在其边部形成富铌钽的黑钨矿，并导致边部铌铁矿族矿物中的Mn含量增加。铌铁矿族矿物结构和成分的连续变化可以用来示踪岩浆-热液演化过程。
Abstract:The large Weilasituo rare metal-tin polymetallic deposit is located in the southern Great Xing’ an Range, NE China. The petrographical changes from medium-grained granite (lower part) to porphyritic fine-grained alkalifeldspar granite (upper part) record the process of magma evolution. To decipher the relationship between magma evolution and the compositional and textural variations of columbite group minerals (CGMs), major element analysis and element mapping for the CGMs were performed using the electron microprobe. Three types of granite were recognized from bottom to top of the Weilasituo intrusion, i.e., medium-grained granite, porphyritic finegrained zinnwaldite alkali-feldspar granite in which the quartz phenocryst has no snowball texture, and porphyritic fine-grained alkali-feldspar granite featured by the snowball texture of quartz phenocryst. The CGMs in the Weilasituo deposit mainly consist of columbite with compositional zoning. The content of Ta increases from core to rim of the CGMs in all the granites, while a compositional gap exists between the outermost zoning of the CGMs and its inside in the two types of porphyritic fine-grained granite. The atomic Mn/(Mn + Fe) values show a different evolutionary trend, which is related to the separated minerals and fluid-mineral reaction. The CGMs in the medium-grained granite and porphyritic fine-grained zinnwaldite alkali-feldspar granite crystallized in the magmatic stage, and the CGMs in the porphyritic fine-grained alkali-feldspar granite formed in the magmatic-hydrothermal transition. The abruptly increasing Ta content of the outermost zoning of the CGMs in the porphyritic fine-grained zinnwaldite alkali-feldspar granite is caused by the separation of zinnwaldite, and the high Ta content of the outermost zoning of CGMs in the porphyritic fine-grained alkali-feldspar granite is attributed to the increased solubility of Ta in hydrosilicate liquid during the magmatic-hydrothermal transition. The co-existing of melt and fluid inclusions in the quartz phenocryst indicates that the snowball texture of quartz formed at the magmatic-hydrothermal transition. In this stage, the exsolved W-rich fluid replaced the crystallized CGMs, forming wolframite in its edge and increasing the Mn concentration in the outermost CGMs. The successive textural and compositional variations of CGMs could be used to trace the magmatic-hydrothermal evolutionary process.
keywords:geochemistry columbite group minerals fractional crystallization of granitic magma magmatichydrothermal transition Weilasituo rare metal-tin polymetallic deposit the southern Great Xing'an Range
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基金项目:本文得到大兴安岭赤峰地区锡多金属矿产调查评价三级项目（编号： DD20230287）、内蒙古自治区地质勘查基金项目（编号： 2015-01-YS01）和内蒙古玉龙矿业股份有限公司科研项目（编号： 2020110033002072）共同资助
引用文本：
杨飞,武广,陈公正,张彤,李英雷,李士辉,师江朋.2023.维拉斯托稀有金属-锡多金属矿床铌铁矿族矿物特征及其对岩浆-热液演化的指示[J].矿床地质,42(3):463~480YANG Fei,WU Guang,CHEN GongZheng,ZHANG Tong,LI YingLei,LI ShiHui,SHI JiangPeng.2023.Compositional and textural variations of columbite group minerals from Weilasituo rare metal-tin polymetallic deposit: Implications for tracing magmatic-hydrothermal evolution[J].Mineral Deposits42(3):463~480
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