AIR is an independent heavy minerals exploration, mining and processing operation focused on the ilmenite deposits derived from dolerite sills of the Roper Gulf Shire region in the Northern Territory of Australia.
The Project is located approximately 590 kilometres south east of Darwin; 120 kilometres east of the town of Mataranka; and circa 110 kilometres west of the Gulf of Carpentaria.
Access from Darwin is via the Stuart Highway to Mataranka and then via the Roper Highway; or via light aircraft to the sealed airstrip at Minyerri.
A portion of the dolerite rich tenements within the Project Area were originally discovered by Rio Tinto in the early 1990’s. Following discovery, Rio Tinto undertook reconnaissance hand auger sampling of the dolerite soil regolith from 1991 to 1996.
In 2000, Exploration & Resource Development Pty Limited (‘ERD’) were granted tenements formerly belonging to Rio Tinto and commenced a soil and lag sampling program followed by a small auger drilling program. Fifty sites representing the majority of the stratigraphic dolerite sill horizons were inspected and samples were gathered. The results of this exploration activity indicated the potential for a high grade ilmenite deposit.
Since 2002, AIR (formerly named ERD) has made several Exploration Licence applications and subsequently been granted a number of additional ELs, and two MLs (refer to section 4.6.2). The granted ELs and MLs cover an area of circa 3,390 square kilometres.
In December 2012, the Project was granted a mineral lease and construction of the processing plant and ancillary infrastructure began in October 2012 (completed in early 2013). The processing plant was procured from Union Resources & Engineering Co,. Ltd and FeCon Solutions Pty Ltd, and constructed on site by MS Contracting Pty Ltd and Monte Electrical Pty Ltd. The site infrastructure was designed by Darwin based engineers and constructed by local contractors.
Construction of the processing plant and mine site
The Project lies in the central-western Bauhinia Shelf of the southern McArthur Basin, in the northeast of the Northern Territory. The McArthur Basin comprises an unmetamorphosed and relatively undeformed succession of marine clastic and carbonate sedimentary rocks, interspersed with extrusive volcanic and intrusive igneous sills of Palaeoproterozoic-Mesoproterozoic age of up to 10 kilometres thick. The region also exhibits highly mineralised Isa Superbasin to the southeast and contains base metals, gold, uranium, iron ore, manganese, diamonds, platinum group elements and petroleum.
The Project targets the weathered ilmenite-bearing Derim Derim Dolerite sills that have undergone unroofing, prolonged weathering, and erosion that has resulted in the accumulation of widespread deposits of heavy mineral-bearing sediment, these include pisolitic, clay-rich, dolerite regolith soils and unconsolidated quaternary to recent sediments.
Derim Derim Dolerite
The Derim Derim Dolerite is a continental tholeiitic dolerite that varies from aphanitic basalt to holocrystalline microgabbro in texture and composition. It comprises of plagioclase feldspar (variably altered to sericite), clinopyroxene (pigeonite-variably altered to epidote and chlorite), and minor (up to about 3-5%) iron-titanium oxides (magnetite, titanomagnetite and ilmenite).
Historical sampling and testing indicates that the dolerite appears to have undergone intensive insitu lateritisation and contains heavy minerals of magnetite, titanomagnetite and ilmenite. Pisolites were also formed during intensive insitu lateritisation. Angular sandstone fragments and thin horizons of angular sandstone clasts suggest that the laterites were reworked locally into poorly bedded, pisolitic, strongly ferruginous, clay-rich elluvial and colluvial regolith deposits of enriched heavy mineral content where the heavy mineral grains are mostly euhedral and unabraided as a result of limited transport. They overlie weathered dolerite and form the bulk of the immediate resource potential. “Black soils” containing smectite clays (responsible for desiccation cracks during the dry season) in contact with the pisolitic regolith and often overlying weathered dolerite also contain heavy minerals that have been trapped by the cyclic shrinking and swelling habit of the smectite. These heavy mineral grains are more strongly abraided. Alluvium in drainage channels comprising unconsolidated sands and grits also contains heavy minerals confined to the coarser layers.
The Project lies in the central-western Bauhinia Shelf of the southern part of the McArthur Basin, in the northeast of the Northern Territory. The McArthur Basin comprises an unmetamorphosed and relatively undeformed succession of marine clastic and carbonate sedimentary rocks, interspersed with extrusive volcanic and intrusive igneous sills, of Palaeoproterozoic-Mesoproterozoic age, up to 10km thick. It correlates with the highly mineralised Isa Superbasin to the southeast and contains occurrences and resources of base metals, gold, uranium, iron ore, manganese, diamonds, platinum group elements and petroleum.
The McArthur Basin developed in response to basement growth faults and accommodation structures represented now by the north-south trending Batten and Walker Troughs and northwest trending fault zones that include the Urapunga Fault Zone that passes through the southern part of the Project Area.
The Project Area is underlain by mudstones and sandstones of the Roper Group, Table 3 sets out the Stratigraphy of the Roper Group and Sill Groups. The Roper Group is of Mesoproterozoic age, 1,324 to 1,429 million years old, and varies from 1.5km to over 3km thick. It is extensively intruded by post-depositional mafic dikes and sills of Derim Derim Dolerite, dated at 1,324 million years. Geological records show the region is gently sloping to flat-lying area. This area is locally folded into broad folds and tightly folded domes.
Stratigraphy of Roper Group and Sill Groups
Lower Palaeozoic rocks in the area unconformably overlie the Proterozoic succession comprising Cambrian Antrim Basalts in the far western area of the Project Area. A strongly dissected sheet of Upper Palaeozoic Cretaceous conglomerates, sandstones, siltstones and claystones are preserved as outliers and mesas throughout. Cambrian and Ordovician sediments are recorded in the Katherine district to the west but evidence of these or other intervening Palaeozoic lithologies is missing from the Project Area. It is assumed that they have either been eroded away or were never deposited suggesting that the Palaeozoic was a period of extensive denudation.
● The following Cenozoic period, starting from the end of the Cretaceous 65 million years ago, was an