Selfrag: An Effective Tool in Sample Preparation for Geological Research

English Abstract:

Extraction of a pure mineral from a geological sample is often vital to analytical techniques ranging from elemental analysis to radiometric dating. The Selfrag instrument uses high-voltage pulsed power discharges to fragment geological material along grain boundaries, conserving morphology and liberating minerals of interest. A series of case studies prove the Selfrag to be a versatile tool. 1) Athabasca Basin sandstones are composed of over 98% quartz. The minor clay constituent retains a geochemical signature of the near-surface environment that can reflect fluid evolution and uranium mineralization at depth. X-ray diffraction of clay-sized material prepared using conventional methods such as disc-mill crushing and centrifugal clay separation displays significant quartz contamination. The Selfrag liberates the clay minerals with minimal quartz contamination, making the sample ideal for subsequent analysis for trace elements and isotopic ratios. 2) The Kiyuk Lake gold deposit is unusual in that it is hosted in Paleoproterozoic sediments, contrary to metamorphosed Archean terranes that typically host significant Canadian gold deposits. Large crystals of actinolite, quartz, calcite, and magnetite were hand-picked from fragmented samples and imaged using scanning electron microscopy. Each mineral was analysed for δ¹⁸O and δ²H to further understanding of the chemical evolution of the deposit. 3) MacMillan Pass is home to several sedimentary-exhalative deposits hosted in Late Devonian sediments. Barite and pyrite from a typical vent complex were successfully fragmented for geochemical analysis to determine potential use as vectors in mineral exploration. 4) Typical crushing methods destroy vital spatial information within minerals that display zonation, such as garnets or zircons. Whole zircons from rhyolitic tuffs and eclogites have been extracted for subsequent radiometric dating and geochemical analysis. Whole garnets from mica schists and eclogites have been extracted for trace element analysis and tomography. The Selfrag is capable of simplifying the process of extracting minerals of interest from a complex matrix, and improves confidence in any analytical method that assumes a mono-minerallic material.