Lucy Creek Project

Mineralisation Style & Geology Setting

In the vicinity of the Lucy Creek project, numerous manganese mineral occurrences are recorded. Lucy Creek and Halfway Dam manganese occurrences are interpreted to be stratabound. At Lucy Creek 2 a 1–2m thick manganese horizon is hosted within dolomitic siltstone of the Tomahawk Formation.

There is disconformity separating the predominantly carbonate sediment Arrinthrunga formation from the overlying clastic sediment Tomahawk formation. This disconformity may have acted as locus for mineralising fluid/wall rock interaction. Within the project area, the disconformity is thought to lie 200-300m below surface.

The basement Altjawarra domain and the Cambrian rocks of the Georgina Basin are cut by a series of north-west and north-east trending faults, which may have acted as pathways for mineralising fluids. The intersections of these faults with the Arrinthrunga formation Tomahawk formation disconformity represent possible sites of MVT-style base metal and manganese mineralisation.

Litchfield considers the area is prospective for manganese‐iron, REE, and base metal mineralisation hosted within the Georgina Basin sequence. Litchfield also considers the area may be prospective for diamonds originating from the basement rocks below the Georgina Basin sediments comprised of  the Altjawarra Block, which is part of the North Australian Craton. The Altjawarra Block is associated with a zone of very thick lithosphere, interpreted to be at least 200 km. The geological setting is believed to be prospective for kimberlitic diamond pipes and the area has been the subject of diamond exploration by several companies.

Historical Exploration

The original discovery of manganese across this ground was during the construction of the Halfway dam. A layer of manganese was found in the floor of the excavations. Although narrow, at around 20cm thick the manganese assayed over 40% and had a low Iron content.

A stratigraphic drill hole was drilled by Exoil in 1966 down to 1,106m at the Lucy Creek 1 area. The rock was a dark, red coloured rock with pronounced gnessic fabric containing dark clots of mafic minerals. The predominant minerals are K-feldspar and sodic plagioclase. Mafic clots are dominated by calcic-alkalic ferroan amphibole and lesser tiantian biotite. Oxide phases are relatively abundent and comprise titanomagnetite and Manganese rich illmenite. Accessory minerals comprise apatite, zircon, monazite. The rock classifies as a syenite or alkali syentie. This synetite represents one of few felsic alkaline rocks recognised from the North Australian craton. Syenites are often associated with both heavy and light rare earths.

Elkedra field work in 2002 mentions they encountered numerous surface occurrences of manganese. Many of the surface samples have ore grade manganese with low-phosphorous content which has characteristics with premium grade manganese ore. They believe the possibility of significant replaces style manganese mineralisation to be present.
Half of the Elkedra manganese samples in the area had base metals enrichments which were indicative of hydrothermal mineralisation, and or typical of manganiferous concentrations present over some base metal deposits.

At Lucy Creek 2 a 1–2m thick manganese horizon is hosted within dolomitic siltstone of the Tomahawk Formation and in 2003 the Elkedra Diamonds team drilled this location with most holes showing massive manganese. There is a possible REE association with carbonate-hosted phosphate-bearing horizons but this has not been demonstrated to date at the tenement.
Anomalous lead to 2.3% in rock chips and 1.4% in percussion drilling is strongly associated with the Mn occurring as fracture controlled and Stratabound replacements. The associated element suite of Ce, Ba, Sr, V, U, Co, Mo, (Ni), (Ag) and (Zn) in Elkedra results is strong suggestive of hydrothermal processes and not at all what would be expected from Scavenging.

Basin stratigraphy and structure has indicated several features strongly favorable for base metal mineralisation related to epigenetic fluids. Potential for sediment-hosted Cu-Co or Au mineralisation cannot yet be determined with the current data however, there are some positive indications from the tectonic-stratigraphic setting by analogy with other sedimentary basins that have undergone fluid migration.