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Re-evaluation of the base and precious metal potential south of the Kalimantan Arc

SRK has been evaluating minerals projects in southern West Kalimantan Indonesia for the past four years. This work has been focussed primarily on advising various clients on exploration and development programs for iron ore.

Iron mineralisation in this region is hosted predominantly within shales which have been hydrothermally altered and selectively replaced by massive hematite. SRK established a spatial association between iron mineralisation and porphyritic plutonic rocks early on, and proposed a magmatic-hydrothermal model of formation. This model formed the basis of future exploration programs designed by SRK for the district.

Drilling programs that SRK implemented have confirmed a magmatic-hydrothermal origin for iron formation. However, in addition to intersecting hematite mineralisation, SRK also identified geological and alteration features consistent with porphyry- or epithermal-style base and precious metal systems in the drill core. Such features include the extensive development of volcanic and deformation breccia, and the alteration of sulphide – quartz – chlorite – epidote – carbonate. These results were somewhat unexpected, as the projects of interest occur significantly south of the currently accepted limits for the Kalimantan Arc – a geological district characterised by gold and precious metals mines with a porphyry or epithermal affinity.

The project’s owners recognised the significance of SRK’s interpretation and the recent exploration findings, and are working closely with us to develop sophisticated exploration programs to simultaneously target iron ore and base and precious metals systems within the district.
Through this project evaluation work in West Kalimantan, SRK has identified a potentially new base and precious metals district, in an area historically targeted solely for iron ore. Most recent exploration results indicate that the iron mineralisation may represent one phase of an overall evolving multi-element magmatic-hydrothermal system. As such, base and precious metal deposit styles within the Kalimantan Arc should be considered in exploration models for the southern West Kalimantan, and should consider a re-evaluation of the southern margin of the Kalimantan Arc.

SRK thanks the International Commerce Corporation Pte Ltd for their permission to publish this article.

Louis Bucci:
Kate Bassano:

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