摘要
铂族元素 (Os,Ir,Pt,Ru,Rh,Pd)具有强亲铁性和强亲铜性 ,为一组地球化学性质相近的相容元素。铂族元素包含两个同位素衰变体系 (1 90 Pt- 1 86Os和 1 87Re- 1 87Os)。近年来 ,铂族元素和 Re- Os同位素在研究各类不同地质作用过程中 ,尤其是在地幔岩石的研究中 ,作用独特 ,效果显著。由于地幔岩石的铂族元素含量较低 ,因此高精度、高灵敏度的分析测试方法的研究就显得十分重要。以往的分析方法 (如常规的 ICP- MS和中子活化分析方法 ) ,对含 10 - 9~ 10 - 1 2 级低含量铂族元素的岩石样品分析精度一般较差 (>15 %~ 10 0 % )。所采用的分析流程通常也无法同时获得样品的铂族元素含量和 Os同位素比值。本文采用新的熔样方法 (HPA- S高温高压釜酸溶法 ) ,新的化学流程 (溶剂萃取和阴离子交换树脂柱 )和新的分析仪器 (多接收等离子体质谱 MC- ICPMS和负离子热电离质谱 N- TIMS) ,用同位素稀释法对低含量地幔橄榄岩样品同时测定铂族元素含量和Os同位素比值 ,获得了高精度的分析结果。对所分析的地幔橄榄岩样品中的铂族元素分配曲线和 Os同位素组成的地质意义进行了初步探讨。
The platinum-group elements (Os, Ir, Pt, Ru, Rh, and Pd) are highly siderophile and chalcophile elements, which are compatible elements and show similar geochemical behaviours. This group of elements includes two radiogenic isotope decay systems of Pt-190-Os-185 and Re-187-Os-187. Recently, the application of PGEs and Re-Os isotope systems in the study of various geological processes, especially in mantle rocks study, has achieved great success and proven to be a useful geochemical tool. Due to the general low concentrations of the PGEs in mantle rocks, it is crucial to develop an analytical method with high precision and high sensitivity. Previous analytical methods such as conventional ICP-MS and INAA usually give low analytical precision of > 15 to 100% for sub-ppb to ppt level rock samples. In addition, the analyses of PGEs and Os isotopic compositions are completed separately using different chemical separation schemes. In this paper, we report a new method that can obtain high-precision results for both the PGEs concentrations and the Os isotopic compositions in one aliquot of low-level mantle rock samples, using a new sample digestion apparatus (HPA-S) and a modified chemical separation method with solvent extraction and anion-exchange resins. The PGEs concentrations and Os isotopic ratios of a set of mantle peridotites are measured by MC-ICPMS and N-TIMS, respectively, and their geological significances are briefly discussed.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2001年第2期325-331,共7页
Acta Petrologica Sinica
基金
国家杰出青年科学基金项目 (编号 :4992 5 30 6 )
国家重点基础研究项目 ( G19990 432 0 8)