Pb-Isotopic Study of Galena by LA-Q-ICP-MS: Testing a New Methodology with Applications to Base-Metal Sulphide Deposits

Abstract

Abstract:In situ laser ablation quadrupole inductively coupled plasma mass spectrometry was used to measure Pb isotopes in galena. Data acquisition was optimized by adjusting spot size, energy density, and ablation time to obtain near steady-state low relative standard deviation (%RSD) signals. Standard-sample bracketing using in-house Broken Hill galena as external reference standard was used and offline data reduction was carried out using VizualAge for Iolite3. Using this methodology, galena grain in polished thin sections from selected massive sulphide deposits of the Bathurst Mining Camp, Canada, were tested and compared to previously published data. Absolute values and errors on the weighted mean of~20 individual analyses from each sample compared favourably with whole-rock Pb-Pb isotope data. This approach provides a mean to obtain rapid, accurate, and moderately (0.1% 2σ) precise Pb isotope measurements in galena and is particularly well suited for exploratory or reconnaissance studies. Further refinement of this approach may be useful in exploration for volcanogenic massive sulphides deposits and might be a useful vectoring tool when complemented with other conventional exploration techniques.

The genesis of the Ali Ou Daoud Jurassic carbonate Zn-Pb Mississippi Valley-type deposit, Moroccan central High Atlas: Constraints from bulk stable C-O-S, in situ radiogenic Pb isotopes, and fluid inclusion studies

“…The galena samples were analyzed using the Laser Ablation Quadrupole Inductively Coupled Plasma Mass Spectrometry (LA Q-ICP-MS) instrument, which consists of ASI (formerly Resonetics) Resolution™ M-50 193 nm ArF (excimer) laser system synchronized to an Agilent 7700x quadrupole inductively coupled plasma mass spectrometer equipped with dual external rotary pumps. For more details on this technique, the reader is referred to McFarlane et al (2016). The precision of Pb isotope analyses was better than ±0.06 %.…”

Advances and Opportunities in Ore Mineralogy

“…Cook et al (2016) [13] provide an overview of current applications of LA-ICP-MS to the trace element analysis of minerals in hydrothermal ore deposits, also noting research gaps, some of the outstanding issues, and future opportunities. The rapidly expanding capabilities of current LA-ICP-MS instrumentation, including both quadrupole and multi-collector systems, include in-situ determination of stable isotopes, and grain-scale mapping of isotopic signatures [14][15][16][17][18]. Outstanding challenges include inadequately constrained issues of down-hole fractionation, the impact of matrix effects, and concerns about how the behaviour of certain minerals during ablation may induce fractionation (e.g., [19]).…”

Trace Element Analysis of Minerals in Magmatic-Hydrothermal Ores by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry: Approaches and Opportunities

“…We speculate on future developments and new applications. Recent advances in geochronology using LA-ICP-MS, Pb isotope analysis, and mapping of sulphur isotopes are covered elsewhere in this Special Issue ( [8,12,13], respectively). Due to space limitations, LA-ICP-MS analysis of fluid inclusions (e.g., [14]), melt inclusions (e.g., [15]), and LA-ICP-MS trace element geothermobarometery (e.g., Ti-in-zircon [16], or Zr-in-titanite [17]), are also not covered here despite their great relevance to understanding the genesis of hydrothermal ore deposits.…”