Abstract
Eight elements were measured in twenty-eight microinclusion-bearing diamonds using both Electron Probe Micro-Analyzer (EPMA) and the cellulose-calibrated Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) methods. Orthopyroxene microinclusions (< 1 μm) found in one of the diamonds have very similar Si atoms per formula unit and Mg/(Mg + Fe) ratios to those of larger orthopyroxene inclusions in diamonds, indicating that the EPMA analysis of the major elements in individual mineral and fluid microinclusions is accurate to better than 15%. For the fluid-bearing diamonds, very good correlations were found between the element/Fe ratios determined by EPMA and LA-ICP-MS for Mg, Ca, Na and K and most diamonds fall on or close to the 1:1 line, validating the accuracy of both techniques. Al/Fe, Ti/Fe and Ba/Fe ratios show good to moderate correlations. LA-ICP-MS analyses of four coated diamonds show that concentrations in the microinclusion-bearing coat are higher than those in the clear core by two orders of magnitude or more. Since most interferences from C-N-O-H molecular ions can be corrected by reference to analyses of pure synthetic diamond, and fewer interferences are expected for the heavier trace elements, the assembled information suggests that LA-ICP-MS technique combined with the cellulose calibration method provides accurate trace-element analyses of diamonds and allows compositional characterization of fluids trapped in them.
| Original language | English |
|---|---|
| Pages (from-to) | 158-168 |
| Number of pages | 11 |
| Journal | Chemical Geology |
| Volume | 252 |
| Issue number | 3-4 |
| DOIs | |
| State | Published - 15 Jul 2008 |
Bibliographical note
Funding Information:We thank Ofra Klein BenDavid for access and permission to use her unpublished data, Tamar Shalev for her help with the EPMA analyses, Norman Pearson and Debora Araujo for their advice with the LA-ICP-MS work and Claude Dalpe and an anonymous reviewer for many good comments. Research was funded by BSF grant #2004161 to Oded Navon and ARC Linkage and Discovery grants to S.Y. O'Reilly and W.L. Griffin. Y.W. thanks the support of the Kameron foundation for his travel to GEMOC. Analytical data were obtained using instrumentation funded by ARC LIEF, and DEST Systemic Infrastructure Grants and Macquarie University. This is contribution no. 514 from the ARC National Key Centre for the Geochemical Evolution and Metallogeny of Continents ( www.els.mq.edu.au/GEMOC/ ).
Keywords
- Diamond-forming fluids
- Diamonds
- Electron probe
- Fibrous
- HDF
- Laser ablation
- Mantle fluids
- Microinclusions