ROLE OF ADVANCED GEOPHYSICAL PROCESSING IN SEARCHING FOR THE NEXT GIANT GOLD-COPPER DEPOSIT IN NORTH SUMATRA

The ‘Sihayo Project’ is a highly prospective exploration tenement in Mandailing Natal, North Sumatra, Indonesia. The region coincides with the prolific Trans Sumatra Fault Zone (“TSFZ”) which hosts significant gold including the giant Martabe deposit (6 Moz Au, 60 Moz Ag).

Sihayo Gold Limited engaged Intrepid Geophysics to reprocess Sihayo’s legacy geophysical data collection and any other regional geophysical data available and incorporate them into tenement scale and regional scale exploration ready geophysical and geological datasets.

The first stage of this project focused on QAQC and reprocessing, standardising, and optimising of the Sihayo Project’s collective airborne magnetic and radiometric data sets. Intrepid’s unique multiscale edge analysis tool finds local maxima points of the total horizontal derivative for many upward continuations of data. In the case of TMI and gravity data the calculated lines can be used to analyse strike distributions for structural units at depth using a GIS platform. However, more significantly WORME outputs the location and dips of 3D contact surfaces calculated from gravity data.

WORME applied to the Sumatra regional Bouguer gravity anomalies, derived from the global gravity dataset, maps the complex 3D structure of the Trans Sumatra Fault Zone (TSFZ), and shows that current representations of this zone greatly simplify its complexity.

At the tenement level WORME was applied to the pseudo-gravity transformation of the TMI RTP grid converting the TMI data to a monopole representation. This methodology provides a set of calculated 3D contact surfaces and dips from the TMI data that can be used as a geological structural base for exploration mapping.

New WORME 3D mapping of the TSFZ reveals the complex structure of this zone and will lead to greater understanding of the structural and tectonic origin of its resource deposits.

In the absence of geological data Intrepid’s geophysics to geology methodology is providing structural geological data as a base layer of tenement and regional geological mapping to the Sihayo Gold Project.

It has already added value for regenerative scope beyond the Sihayo Starter Project, as new and prioritised targets are derived from new and legacy geophysical survey data. This is the essence of our mantra ‘3D Geology from Geophysics” especially important when exploring undercover and under tree-canopy.