|Title||Fine Fraction Indicator Mineral Signatures of Porphyry, VMS and other deposits|
|Author||Lougheed, H D; McClenaghan, M B; Layton-Matthews, D|
|Source||Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 40, 2017. Open Access|
|Links||Online - En ligne|
|Alt Series||Earth Sciences Sector, Contribution Series 20160430|
|Publisher||Geological Association of Canada|
|Publisher||Mineralogical Association of Canada|
|Meeting||Geological Association of Canada - Mineralogical Association of Canada Joint Annual Meeting; Kingston; CA; May 14-18, 2017|
|Media||paper; on-line; digital|
|Subjects||metallic minerals; mineralogy; general geology; indicator elements; mineral exploration; exploration methods; diamond; gold; base metals; scanning electron microscope (SEM)|
Geoscience Initiative (TGI-4), Intrusion/Porphyry Ore Systems|
|Abstract||The use of indicator mineral methods for mineral exploration in glaciated terrain has been slowly expanding since the 1960s when they were first used for gold and diamond exploration. Today, indicator
minerals are used for exploration for a broad range of commodities including diamonds, gold, PGE, and base metals. For indicator minerals to be effectively recovered from till samples, they must be sufficiently dense to allow separation and
concentration from till using gravity methods. Indicator minerals are generally present in low concentrations within till (ppb levels), and therefore large samples (10-20 kg) are commonly necessary to obtain significant and useful numbers of grains
in a sample. After density separation, the resulting heavy mineral concentrate (HMC) samples are sieved to a desired fraction for examination under a binocular microscope.|
Grain size has traditionally been a limiting factor on analysis, as
material smaller than 0.250 mm is too small to manipulate accurately and increasing grain counts make thorough examination impractical. This study plans to utilize a scanning electron microscope equipped with an energy dispersive x-ray spectrometer
(EDS) and Mineral Liberation Analysis (MLA) automated quantitative mineralogy software to enable rapid quantification of the modal mineralogy and grain size/shape characteristics of <0.250 mm HMC.
The first phase of study has focused on the
handling and effective separation of <0.250 mm HMC material into meaningful size fractions. The fine grain size makes material loss and contamination a serious concern, and thus the authors have designed proprietary, single-use sieves that can be
disposed of between sample runs. This eliminates the chance of cross contamination between samples due to ineffective cleaning. Protocol for the effective handling of this fine material, focusing on minimizing loss and contamination while maintaining
the efficacy of the sieving procedure, have been designed and implemented. The observed grain size distributions
and material loss within the four size fractions chosen for study have given superior results than those obtained with standard
stainless steel laboratory sieves.
The next phase of study (currently ongoing) sees the mounting of each size fraction into epoxy ring mounts, which are subsequently quartered and reassembled into a second mount, giving a planar surface with both
basal and cross sectional surfaces available for SEM analysis. The resulting MLA scans will allow the construction of mineralogical databases for each sample and the characterization of each fraction of till.
|Summary||(Plain Language Summary, not published)|
This abstract reports preliminary results for new heavy mineral processing methods to allow for the characterization of minerals that indicate porphyry
Cu and VMS fertility. This research is part of the GSC's TGI 5 Program.