摘要
榍石(CaTiSiO5)广泛存在于各类岩石和矿床中,根据其结构、矿物共生组合和化学成分可分为岩浆榍石、热液榍石和变质榍石。榍石具有复杂的化学成分,多种元素(如REE、Fe、Al、Zr等)可以替代榍石中的Ca、Ti、Si和O。榍石的结晶温度、压力和Zr含量之间存在系统变化规律,是榍石Zr温度压力计的基础。榍石因其较高的U含量和封闭温度使其成为理想的U-Pb定年矿物,但需要注意普通Pb的校正。榍石的化学组成可以判别岩石类型:其LREE和Fe/Al值可以区分原岩为火成岩还是变质岩;岩浆榍石的Zr/Y值和Fe含量可以有效地区分长英质岩石和镁铁质岩石。利用榍石Nd同位素组成和Sr、F等元素含量可以示踪岩浆源区和岩浆演化过程。榍石-磁铁矿-石英的矿物共生组合可以指示岩浆高氧逸度特征,且榍石中的变价元素(如Eu、Ce、Ga、Fe、V)以及Th/U值也可用于推断岩浆的氧化还原状态。由于榍石中携带丰富的地球化学信息,其结构和化学组成广泛用于揭示成矿过程。在与矽卡岩密切相关的钨矿床中,榍石Al、Fe、W和Mo含量能够反映钨成矿环境的氧逸度和压力等成矿条件,进而指示矽卡岩型钨矿床的富集成矿机制;在斑岩型铜-钼矿床中,榍石δCe、δEu值可以指示岩浆氧逸度, F含量能指示岩浆黏度,反映钼成矿潜力;而在与花岗岩相关的热液型锡矿床中,富锡岩浆榍石反映出花岗质岩浆中的锡富集特征,受热液改造的榍石则体现后期Sn元素的迁移和聚集过程。此外,榍石中特征元素(U、Th、Fe、Al、REE等)含量和Fe/Al值可以用于判别成矿与不成矿的花岗质岩体,并用于区分不同矿床类型。综上,榍石是一种有效的指示矿物,不仅在成岩和成矿过程的示踪方面体现出独特的优势,在判断和评估某些岩体的成矿潜力方面也具有广阔的前景。
Titanite(CaTiSiO5)exists widely in different rocks and ores,which can be divided into magmatic,hydrothermal,and metamorphic titanite based on its structure,mineral assemblages,and chemical composition.Titanite has a complex chemical composition with a variety of elements(such as REE,Fe,Al,Zr,etc.)replacing the sites of Ca,Ti,Si,and O.The crystallization temperature,pressure,and Zr content of titanite vary systematically,which is the basis for the titanite Zr thermobarometer.Titanite is also an ideal mineral for U-Pb dating due to its high U content and high closure temperature,but attention must be paid to the common Pb corrections.The chemical composition of titanite can be used to clarify the rock type.For example,the LREE value and Fe/Al ratio can distinguish titanite from igneous or metamorphic rocks.The Zr/Y and Fe contents of magmatic titanite can effectively distinguish between felsic and mafic rocks.The Nd isotope and the content of Sr,F,and other elements of titanite could be used to trace the origin and evolution process of magma.The mineral assemblage of titanite-magnetite-quartz indicates high oxygen fugacity in the magma,and the varivalent elements such as Eu,Ce,Ga,Fe,V,and Th/U in titanite also predict the redox state of the magma.Because titanite carries rich geochemical information,its structure and chemical composition are also widely used to reveal the ore-forming process.In the skarn tungsten deposits,the contents of Al,Fe,W,and Mo of titanite reflect the metallogenic conditions of the skarn tungsten deposits,such as oxygen fugaticity and pressure.In the porphyry copper-molybdenum deposits,theδCe andδEu of the titanite indicate the oxygen fugacity of the magma,and the content of F implies the magma viscosity,all of which reflect the potential of molybdenum mineralization.In granite-related hydrothermal tin deposits,the tin-rich magma titanite implies the initial concentration of tin in the granite magma,and the hydrothermally altered titanite reflects the migration and accumulation of tin in the later period.In addition,the characteristic element(U,Th,Fe,Al,REE,etc.)content and the Fe/Al ratio of titanite can be used to distinguish ore-bearing and barren granites,as well as to distinguish different types of deposits.In conclusion,titanite is an effective indicator mineral that not only has a unique advantage for tracing the petrogenesis and metallogenic processes but also has a broad prospect in judging and evaluating the metallogenic potential of certain rocks.
作者
樊子航
陈喜连
许德如
邹少浩
张恒松
冷成彪
杨萃
FAN Zihang;CHEN Xilian;XU Deru;ZOU Shaohao;ZHANG Hengsong;LENG Chengbiao;YANG Cui(National Key Laboratory of Uranium Resource Exploration and Nuclear Remote Sensing,East China University of Technology,Nanchang 330013,Jiangxi,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;Key Laboratory of Strategic Mineral Metallogenic Theory and Deep Prediction in Jiangxi Province,East China University of Technology,Nanchang 330013,Jiangxi,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China)
出处
《大地构造与成矿学》
北大核心
2025年第4期777-796,共20页
Geotectonica et Metallogenia
基金
国家自然科学基金项目(42362013、42363009、U2344205)
江西省自然科学基金项目(20224BAB203036)
赣鄱俊才支持计划-主要学科学术和技术带头人培养项目-青苗人才(学术类)(20243BCE51152)联合资助。
关键词
榍石
类质同象
地球化学特征
榍石Zr温度压力计
岩石成因
成矿示踪
titanite
isomorphism
geochemical characteristics
titanite Zr thermobarometer
petrogenesis
metallogenic tracing
