Whole-rock trace element analyses via LA-ICP-MS in glasses produced by sodium borate flux fusion

Felipe Padilha Leitzke,Carla Cristine Porcher,Stephan Klemme,Aline Celuppi Wegner,Rommulo Vieira Conceição,Natália Isabel Malüe Vieira,Jasper Berndt

doi:10.1590/2317-4889202120200057

Abstract

Abstract Trace elements provide crucial information about the origin and evolution of the Earth. One common issue regarding their analyses is the reduced analyte recovery during hot plate acid digestion for some geological samples. To overcome this, alkali fluxes (e.g., Lithium borate) have been used to produce an homogeneous synthetic glass that can be used then for both X-ray fluorescence (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In this sense, we developed a method for LA-ICP-MS whole rock trace element analyses in glasses prepared by mixing high-purity sodium tetraborate and rock powders at high-temperature. We selected six international reference materials including peridotite (JP-1), basalt (BRP-1), kimberlite (SARM-39), pyroxenite (NIM-P), diorite (DR-N) and andesite (JA-1). Glasses were produced in a fully automatic fusion machine with step heating. Run products analyses were carried out on a Thermo® Element2 SF-ICP-MS coupled to a New Wave Research® Nd:YAG (213 nm) laser ablation system and on a Thermo® Element XR ICP-MS coupled to an Analyte G2 (193 nm) LA system. Results show that glasses are homogeneous and there is good agreement (generally > 90%) between our data and literature values for most trace elements, including large ion lithophile elements (LILE), high-field strength elements (HFSE) and rare-earth elements (REE).

Highlights

Despite their low abundance, trace elements provide crucial information about geochemical processes during the origin and evolution of the Earth and other planets (e.g., Kelemen et al 1993, Münker 2010, White 2013)
Chromium content measured in the SARM-39 sample is 1,016 ± 56 while literature values range from 1,204 to 1,360, which could be explained by areas that are enriched in Fe-Cr spinel microcrysts that did not react during glass production
We presented a method for determining precisely and accurately whole-rock trace element contents using LA-inductively coupled plasma mass spectrometer (ICP-MS) on glass beads produced by mixing high-purity sodium borate and rock powders at high-temperature

Summary

Introduction

Trace elements provide crucial information about geochemical processes during the origin and evolution of the Earth and other planets (e.g., Kelemen et al 1993, Münker 2010, White 2013). Trace elements have long been used to constrain tectonic settings and petrogenesis of a given geological unit (e.g., Pearce et al 1984, Whalen et al 1987), in mineral exploration and the origin of ore deposits (e.g., Pearce and Gale 1977, Hutchinson and McDonald 2008, Reich et al 2016), or even to constrain large-scale planetary differentiation processes (e.g., Pfänder et al 2007, Leitzke et al 2017) For this reason, the high demand for trace elements analysis has led to a wide methodological/instrumental development in the last 10 to 20 years in geochemistry, promoting increasingly expressive analytical results in this area. The first is the use of analytical techniques that do not require sample digestion such as Spark Source Mass Spectrometry (SSMS), Secondary Ion Mass Spectrometry (SIMS) or instrumental neutron activation

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