Porphyry Indicator Minerals (PIMS): Exploration for Concealed Deposits in QUEST, central British Columbia
(NTS 92I, 93N)
- Farhad Bouzari and Craig Hart, MDRU
Quesnel and Stikine terranes in central British Columbia host Late Triassic to Early Jurassic arcs that are highly-prospective hosts for porphyry copper deposits. However, exploration success in this area is limited due to thin, but extensive veneers of till and related glacial sediments that cover much of the area. QUEST and QUEST-West are examples of projects that have provided a significant amount of new geochemical and geophysical data that warrant follow-up exploration efforts. We suggest that glacial materials may best host evidence of concealed deposits.
Porphyry indicator minerals (PIMS) are minerals, such as apatite, rutile, garnet and titanite, that form during porphyry copper deposit formation and are resistant to weathering. Although easy to collect in heavy mineral concentrates, these minerals have rarely been used as exploration tools, but the QUEST area is an ideal region to test their applicability. These minerals, when formed or altered in hydrothermal porphyry environments, commonly display unique physical properties such as color, size and shape that allow their presence to be used as a prospecting tool in a similar manner to which kimberlite indicator minerals are used. Moreover, the chemical compositions of PIMS can identify mineralizing environments that relate directly to specific alteration zones in porphyry systems. Therefore, by evaluating the presence, abundances, relative proportions, and compositions of PIMS from surficial materials, it is possible to evaluate and better rank geophysical and geochemical anomalies to vector towards concealed porphyry copper deposits.
The aim of this project is to establish a methodology that can effectively evaluate existing geochemical and geophysical targets, and identify new targets and define vectors to source, in highly prospective, but till-covered areas of British Columbia. Specifically, we aim to identify the occurrence, types, relative amounts, character and compositions of porphyry indicator minerals in at least two, well-known porphyry deposits, and determine their signatures in adjacent sedimentary materials (tills and stream sediments).
We will use standard separations for heavy minerals, and standard analytical techniques for their analysis, but will utilize newly-available MLA (mineral liberation analysis) technology which is increasingly used in metallurgical studies and is available from local, commercial labs. Thus, the focus of the analytical work will be on characterizing the physical properties of resistate minerals such as relative abundances of mineral species, grain shape and grain size.
Resistate minerals can fill gaps in the current exploration knowledge in this region and have the potential to provide the missing link between ore deposits and glaciated sedimentary cover. Results of this project will provide a simple tool to assess and rank prospective areas and, in conjunction with available data, better delineate targets.
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