利用多接收器电感耦合等离子体质谱仪(MC-ICPMS)测定镁铁-超镁铁质岩石中的铼-锇同位素组成

报道了用多接收器电感耦合等离子体质谱仪(MC-ICPMS)测定Re-Os同位素组成的质谱方法和化学分离方法,并应用该方法测定了天然镁铁-超镁铁质岩石样品中的Os同位素组成及Re、Os含量.Re同位素组成的MC-ICPMS测定利用膜除溶雾化器(Aridus)和静态法拉第杯接收的方式完成,采用Ir标准溶液在线校正仪器的质量分馏.Os同位素组成的MC-ICPMS测定采用常规雾化器和离子计数器静态接收的方式完成,并用10%的HCl-EtOH和10%的HCl溶液交替清洗进样系统来消除Os的"记忆效应".岩石样品的Re和Os化学分离采用Carius管溶样法,结合CCl4萃取以及微蒸馏的方法分离纯化Os,利用阴离子交换树脂的方法分离纯化Re.运用上述方法,对6个镁铁-超镁铁质岩石样品中的Re、Os含量和187Os/188Os同位素比值进行了测定,获得了理想的分析结果.

Measurements of Re-Os isotopic composition in mafic-ultramafic rocks by multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS)

A Re-Os isotopic measurement method by multi-collector inductively coupled plasma mass spectrometer(MC-ICPMS) and Re-Os chemical procedures for natural rocks are reported. For Re measurements, an Aridus desolvation high-efficiency nebulizer is used for sample delivery and element Ir is added into sample solution as an internal isotopic standard in order to correct mass fractionation on-line, and Re and Ir ion beams are detected on Faraday cup simultaneously. For Os measurements, Os ion beams are detected by static multi-ion counting electron multiplier collectors, and the Os memory effect may be eliminated by using 10% HCl-EtOH mixture solution and 10% HCl to clean inlet system alternately. Chemical procedures for Re and Os separation include: Carius tube is used to digest rock samples, Os is separated by CCl4 solvent extraction and purified with micro-distillation method, and Re is separated through anion exchange chromatography. The Re and Os concentrations and Os isotopic ratios of six mafic-ultramafic rocks determined by MC-ICPMS are presented, and the results are in agreement with those measured by negative thermal ionization mass spectrometry (N-TIMS) within analytical uncertainty.