Summary:
The Ranobe deposit comprises five mineralized units: the upper sand unit (USU) and its sub-units, the surface silt unit (SSU) and an upper silty sand unit (USSU), the intermediate clay sand unit (ICSU), and the lower sand unit (LSU).
While the LSU has been excluded from the current Mineral Resource estimate because of observed differences in the mineral assemblage and limited available mineralogical and metallurgical data for this unit, significant upside potential is believed to exist based on existing drilling results and future exploration and resource definition is planned.
Deposit Types
Variability in mineralization grade of the Ranobe deposit occurs both down the mega-dune system profile and laterally. This reflects the mechanism of mineralization where heavy mineral (HM) is concentrated within the sands by aeolian winnowing, within a mobile dune complex that has experienced multiple episodes of deposition and erosion during the dune building process. The mineralization generally thickens (from 3 m to 39 m) and decreases in grade westwards away from the scarp slope. The deposit anisotropy parallels the scarp slope, with higher HM grades concentrated along the mega-dune crest line.
The primary factor controlling grade and geology continuity is mega-dune morphology. The limestone morphology also impacts sand deposition and continuity of grade along the eastern extents of the Ranobe deposit and in the central part of the deposit, where numerous limestone pinnacles occur.
Mineralization
The deposit is hosted within a stabilized mega-dune system, which is arrested along the basement scarp and extends for approximately 22 km north-northwest. The entire dune unit is mineralized with an assemblage of ilmenite, zircon, rutile, and monazite concentrated within the sands by aeolian winnowing. The mineralization generally thickens (from 3 m to 39 m) and decreases in grade westwards away from the scarp slope. The deposit anisotropy parallels the escarpment slope, with higher HM grades concentrated along the mega-dune crest line. The geological controls on mineralization appear related to areas where the morphology of the LST escarpment (and the ridgelines that extend west from the escarpment) has acted as a barrier to aeolian transport mechanisms of the mobile sand mass that has resulted in concentration of heavy minerals via winnowing of the lighter material.
The aeolian dune system has little induration, low clay content, and variable HM concentrations (averaging approximately 6%, but up to 25% HM) overlying a fluvial or lagoonal unit of clayey sand with minor induration, moderate clay content, and low HM. Along the western margin of the deposit, a thick marginal marine sand sequence occurs at depth, which contains minor indurated horizons, low to moderate clay content, and variable HM concentrations (including strandlines) with up to 40% HM.
The mineral resource extends for 20 km north-south and averages 3 km wide east-west. The average depth of mineralization from the surface to the 1.5% HM cut-off is 20 m, with a range of 3 m to 39 m.
The heavy minerals of economic interest (in order of abundance) are ilmenite, zircon, monazite, leucoxene, and rutile, although significant quantities of garnet have been observed in the deeper marine sands.
The heavy minerals were eroded from hinterland basement rocks, transported by rivers to the ocean, and from there reworked by wave action and deposited as detrital grains on a beach. Subsequently, they were blown by the wind to their ultimate position in the Ranobe deposit, along with detrital grains of quartz.