Chase Mining Corporation’s (CML) is expanding its Barkly North Rare Earths Project, with new applications for adjoining Exploration Licences to explore 160km north-west of the project.
The 160km linear extent of the rare earths trend was revealed by Geoscience Australia (GA), through the North Australian Geochemical Survey.
The two expanded licences, EL 33128 and 33129, are expected to be offered grants over the next few months, with the newer applications ELs 33229 and 33230 expected to be granted before January 2023. CML has proposed to firstly conduct more surface sampling throughout the project area once granted in order to better define and identify the sources of the rare earths.
It is anticipated that a program of shallow drilling traverses will then allow the confirmation of a mineral resource.
The gravity and magnetic targets will be modelled. Those that are confirmed as being caused by rocks at reasonable depths may be further investigated with more geophysics and drilling.
Rare earths potential
The Geoscience Australia conducted North Australian Geochemical Survey which covered the entire Barkly region west of Mount Isa with very widely spaced stream sediment samples of various sieve sizes, and with a variety of analyses for all elements.
A CML study of this very large public database revealed this continuous 160km trend of peak rare earth anomalism with accompanying high values in supporting elements, notably niobium chrome and uranium.
The project area is covered by lateritised sediments with strongly developed clayey soil profiles, and the trend bears no relationship to the underlying basement rocks, or to magnetic features.
Ionic clay rare earth deposits have advantages over hard rock rare earth deposits. They are cheaper to mine and process, and the waste material does not present problems with toxic elements. Much of the world supply is from clay hosted deposits.
Base metal potential
In addition to the prospects for ionic rare earths, the Barkly North project area has had a long-recognised potential for major base metals deposits in the underlying unexposed older sequences.
These sequences include those that host the major shale hosted and IOCG deposits in McArthur River and Mount Isa districts.
The 1993 BHP corehole MD1 in the centre of the project intercepted a 100m thick black dolomitic shale with scattered copper lead and zinc sulphides.
A lack of data to guide exploration hampered efforts to select drill sites as follow up holes.
This problem is being overcome by Geoscience Australia which has selected the area for detailed study and has recently been publishing their seismic and detailed gravity surveys.
The recent detailed gravity data is proving very useful and has revealed a nonmagnetic gravity trend arcing through MD1.
This has provided CML with a target for future follow up geophysics and possible drilling.
Nonmagnetic gravity ridges such as this are most likely to represent the dense prospective pyritic dolomitic shale which hosts the mineralisation intercepted in the BHP drillhole.
Further west, within the new EL applications (33229 and 33230), the GA detailed gravity survey outlined other gravity targets, some of which are magnetic.
The adjacent or combined magnetic and gravity responses are typical of IOCG styles of mineralisation. They could alternatively represent intrusive bodies, with mineralisation on the contacts with carbonate sediments.
The depths of these western targets are unknown, but they can be calculated by modelling the new detailed data. GA has verified the existence of IOCG style alteration and mineralisation in the Barkly region
They have drilled combined gravity and magnetic targets through similar cover, about 250km to the south of the project, and have triggered an exploration rush in that area.
Image courtesy of Chase Minerals.
