AGS Colloquium 2022 Workshop

Theory, practice, and new applications of laser ablation inductively-coupled plasma mass spectrometry

Presented by Prof. Chris McFarlane and Brandon Boucher

Workshop summary:

Laser ablation inductively-coupled plasma mass spectrometry (LA ICP-MS) is used for a variety of geochemical and isotopic investigations.  Minimal sample preparation, low detection limits, high spatial resolution, and high throughput make it an attractive technique for geochronology, trace-element characterization and tracer isotope studies.  This workshop is structured with two main parts: 1) a morning session that covers basic operation concepts, instrumentation, and background theory of laser-target interactions and plasma dynamics; 2) an afternoon session covering applications to geochronology, trace-element characterization, and tracer isotopes including worked examples using Iolite data reduction software.  Along the way we will introduce some new techniques now possible using the Agilent 8900 QQQ-ICP-MS recently installed at UNB Earth Sciences: Rb-Sr, K-Ca, Lu-Hf, La-Ba, and Re-Os isochron dating.

Fee structure:

Free for students; registration cost for professional TBA

Morning session

8:30-10:00:

  1. How it works: lasers and plasmas
  2. Laser-target interactions and key variables; crater size, fluence, repetition rate, ablation time, carrier gas
  3. Material-dependence of ablation characteristics (silicates, sulfides, oxides, carbonates)

10:00-10:15: morning coffee break

10:15 – 11:15:

  1. Plasma ionization efficiency and key plasma tuning parameters
  2. Sensitivity vs. robustness: your choice!
  3. A word about detection limits

11:15-12:00:

  1. Planning a LA ICP-MS session
  2. Matrix-matching and standard-sample bracketing; primary vs. secondary standards
  3. Typical precision and long-term reproducibility
  4. Differences between single-quadrupole vs. tandem-quadrupole ICP-MS  

12:00-12:45 Lunch and general discussion

12:45-1:00 Questions arising from morning session

Afternoon session

1:00-2:00

  1. In situ U-(Th)-Pb geochronology of accessory minerals: importance of imaging and internal zoning; integration with micro-XRF, cathodoluminesence and BSE imaging; dealing with common-Pb
  2. Walk-through example of zircon data reduction in Iolite4

2:00-3:00

  1. Trace-element characterization and visualization; trace-element mapping; QAQC modules; walk-through example of sulfide data reduction in Iolite4

3:00-3:15 afternoon coffee break

3:15-4:00

  1. How it works: Tandem-quadrupole ICP-MS (LA MS/MS-ICP-MS)
  2. Applications to dating deformation: mica Rb-Sr and K-Ca isochron dating

4:00-5:00

  1. Tracer isotopes: Sr and Pb isotopes in apatite and feldspars
  2. Novel isotope systems: 138La-138Ba in monazite & fergusonite; 92Nb-92Mo in tantalite
  3. Concluding remarks

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