NORTHERN TERRITORY
BARKLY COPPER-GOLD SUPER PROJECT
Located in the Northern Territory, Middle Islands’ 100% owned Barkly Copper-Gold Super Project (Barkly Project) comprises 16 exploration licences (14 granted & 2 applications) covering an aggregate 6,918km2.
Figure 1. Barkly Copper-Gold Super Project tenements and targets.
The Barkly tenements primarily cover the interpreted eastward extensions of the prospective Tennant Creek Mineral Field Proterozoic stratigraphy, that includes the East Tennant Ridge and Burnette Downs Rift corridor (Figure 3), masked beneath shallow to moderate depth Georgina Basin cover.
The Georgina Basin extends east from Tennant Creek across the border to Mt Isa and is sub-divided by several basement highs into sub-basins. The principal basement high, the East Tennant Ridge, runs through the Barkly Project area, where the interpreted depths of post-mineral Georgina Basin sedimentary cover range from 100-250m along the ridge axis, increasing on the flanks of the ridge. The underlaying basement and Paleoproterozoic are relatively unexplored because of the veneer of younger sedimentary rocks.
The discovery opportunity at Barkly is for large Iron Oxide Copper-Gold (IOCG) and Sediment Hosted Copper-Zinc-Lead-Silver (SedH) deposits.
Iron Oxide Copper-Gold (IOCG)Targets
The East Tennant corridor has gained recognition as a priority, largely unexplored, prospective IOCG mineral province (Figure 2). IOCG deposits, which are MDI’s primary target, include large lower grade deposits to smaller high-grade variants. Australian deposit examples include Olympic Dam, Oak Dam, Prominent Hill, and Carrapateena in South Australia; Ernest Henry in Queensland, and Warrego and Juno located to the west of the Barkly Project within the Tennant Creek Mineral Field.
The Tennant Creek Mineral Field was one of Australia’s highest-grade gold and copper mining districts producing more than 5.5M oz of gold and 460,000t of copper from historical deposits including Warrego, Juno, Nobles Nob, Juno and Peko. These deposits are variants of ICOG deposits with mineralisation predominantly hosted within magnetite-hematite ‘ironstones’ as discrete lenses or ‘shoots’.
Figure 2. IOCG prospectivity predictive modelling and the Barkly Super Project area.
IOCG deposits and alteration surrounding them have elevated levels of iron oxide minerals magnetite and hematite, which give rise to elevated magnetic and gravity (density) signatures that can be mapped readily with geophysical surveys (magnetics and gravity). The copper-gold mineralisation that makes up the deposits occurs as sulphide minerals with a more restricted areal extent that can commonly also be mapped by gravity surveys and other geophysical techniques (IP, EM, MT). The often-strong geophysical signatures of the alteration and mineralisation lends itself to effective explorations under cover, as is the case at Barkly. Significant examples of ‘blind’ IOCG deposits discovered beneath substantial sedimentary cover include BHP’s Olympic Dam and Oak Dam deposits in South Australia, which are respectively overlain by approximately 400m and 900m of post-mineralisation cover.
Supported by geological interpretations a portfolio of highly ranked magnetic and gravity targets have been identified. For the latest details on the targets please refer to (latest target ASX release)
Figure 3. Magnetics image showing priority prospects and targets – large high amplitude magnetic and/or related gravity anomalies are distributed along major fault corridors – deep crustal faults with interpreted multiple stages of extension and reactivation
Sediment Hosted Copper-Zinc-Lead-Silver (SedH) Targets
The Brunette Downs Rift Corridor (Figure 3) is also considered to be prospective for large sediment hosted Cu -Zn-Pb-Ag deposits (SedH) like those found in the Mt Isa Inlier to the east and southern McArthur Basin to the north. Deposit examples include Mount Isa, Hilton, George Fisher, Lady Loretta, Century, Walford Creek and McArthur (HYC).
The East Tennant Ridge is fault bound and marks the southern margin to the Brunette Downs rift corridor. Proterozoic sedimentary strata within the rift grabens and onlapping onto the basement highs include rocks interpreted to be extensions of the superbasins that host many of the listed deposits above.
The Company has identified targets in two distinct settings:
· within the rift half-graben basins; and,
· on the upthrown graben margin block (East Tennant Ridge).
In both settings, the presence of linear dense horizons encasing well defined density anomalies (‘shoots’) has been confirmed by modelling gravity data and potentially represent sulphide rich sedimentary horizons. The potential stratabound nature of the ‘shoots’ and structural position near basin margin growth faults is consistent with SedH exploration concepts.
For the latest details on the targets please see the link below. (latest target ASX release)
Other Commodity Targets
At Barkly within EL32627, significant phosphate occurrences are demonstrated with multiple drill intercepts >10% P2O5 , 2 – 16m thick; with individual metre intervals up to 37% P2O5 , at depths of 29 – 53m from surface over an extensive area. The occurrences are located approximately 25 km west of the large Wonarah Phosphate Project in extensions the formation that hosts the Wonarah resource.
The mineralisation lies within the late Proterozoic to early Palaeozoic sedimentary rocks of the Georgina Basin which hosts several phosphate deposits in eastern Northern Territory and western Queensland. Mineralisation is contained within flat lying sedimentary rock layers of mudstone, siltstone and chert breccia with varying content of phosphorite.
The drilling conducted by previous explorers recorded intervals of >10% P2O5 mineralisation in 1-2 km spaced drillholes defining an Exploration Target area of 55km2.
The phosphate occurrences are noted for the record, MDI is not exploring these presently.