Project code: 2016-006
Project type: Minerals
Principal Proponent: School of Earth and Environment, Leeds University, Leeds, UK
Principal Investigators: R.J. Chapman, D.A. Banks, C. Spence-Jones.
Project location: South-central and central British Columbia, including areas around Kamloops, Princeton, Prince George and the Cariboo region (Quesnel, Likely/Horsefly, Wells)
This project evaluates the use of laser-ablation technology to vaporize portions of tiny gold grains so that a mass spectrometer can then measure alloyed elements contained in gold grains (LA-ICP-MS). The presence of certain elements and their relative abundance is useful for linking loose gold grains back to a possible source.
How was the data collected?
Most of the samples for this study are from in-house inventories assembled by the researchers during previous field campaigns.
Detrital and bedrock-liberated gold grains are mounted in resin blocks and polished to reveal the core of the gold grain.
Images of the polished block surface are then used to identify each grain within each sample. This allows researchers to correlate the microchemical data from the gold grains with data obtained by LA-ICP-MS.
LA-ICP-MS is used to measure the trace amounts of alloyed elements in individual gold grains. Statistical analysis are then employed to appraise which elements would be useful in distinguishing between different mineral deposits.
Gold grains from bedrock source provide a reference for a deposit type, to which the detrital grains can be correlated.
What was found?
Preliminary findings demonstrated that measurement of trace amounts of alloyed elements in gold grains using LA-ICP-MS might be useful for constructing multi-element templates for comparing gold grain clusters from different locations. This included results that suggested that gold found in alkalic porphyry deposits can be distinguished from gold found in orogenic systems by much higher concentrations of trace elements, particularly palladium, copper, and mercury.
Further study had researchers compare two types of LA-ICP-MS techniques (quadrupole and Time of Flight) and statistical analysis to accurately identify and quantify the trace elements. They found that some microscopic minerals (e.g.pyrite) within the gold grains act as 'sinks' for certain trace elements. This mix of trace elements varies according to source style of mineralization and can help to identify the host gold grain's source.
New findings in the report have further revealed that gold grains are very heterogeneous in terms of trace element distribution and that interpretations of overall alloy content or source must be made carefully made. That heterogeneity allowed the researchers to speculate that larger populations of gold grains may in fact be necessary than first anticipated.
- Summary of Activities 2016, Report 2017-1 p. 201-212 (PDF, 4.6 MB)
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