Thundelarra (ASX:THX) has extended zinc mineralisation at its Little Mount Isa prospect in Western Australia intersecting 8 metres at 4.76% zinc from 41 metres to 49 metres, while the true width is unknown.
Little Mount Isa prospect is part of the Sophie Downs project which is around 50 kilometres to the north-east of Halls Creek in the East Kimberley region.
The present drilling programme comprised seven reverse circulation drillholes for a total of 750 metres and followed from a previous programme of six RC holes for 719 metres, which successfully tested the possibility of the presence of replacement skarn-style base metal mineralisation at Little Mt Isa.
2013 drill results Little Mount Isa
In 2013, re-evaluation of historical work programs and exploration results over the project area suggested that previous interpretations that the copper-lead-zinc mineralisation at Ilmars and Little Mount Isa were of VMS (volcanogenic massive sulphide) origin may be incorrect.
A small drill program tested the possibility that replacement skarn-style base metal mineralisation exists at Little Mt Isa and at Ilmars and also tested the potential for gold mineralisation at the Duffers prospect.
Results from 2013 yielded new massive sulphide intercepts at Little Mount Isa of:
- 13m at 4.6% Zn from 52m in hole TSDRC06 including:
- 6m at 8.4% Zn; and
- 3m at 12.6% Zn
This successfully tested the possibility that replacement skarn-style base metal mineralisation might exist at Little Mt Isa.
The purpose of this program was to follow up on those previous high grade zinc results to determine if conductors identified in previous VTEM geophysical surveys were in any way associated with, or indicators of, the mineralisation in those holes.
Consequently the drillholes were located in order to test the interpreted position of the conductors and to establish whether or not they were representative of sulphide mineralisation.
TSDRC007 was drilled intermediate between earlier holes TSDRC005 and 006 to test for continuity of relatively high grade zinc mineralisation between these two holes.
High grade zinc mineralisation was intersected between 41 metres and 49 metres (8m at 4.76% Zn, true width unknown), confirming the continuity.
The exact nature of the zinc mineralisation is not yet clear from the information collected to date; it may in part be supergene (smithsonite) as the amount of sphalerite observed in this interval is not consistent with the high zinc grades.
TSDRC008 was targeted to intersect the mineralised horizon down dip from TSDRC006. The mineralised horizon was successfully intersected between 85 metres and 95 metres down hole but the interval reported lower zinc grades (10m @ 0.71% Zn; true width not known).
TSDRC010 was drilled further north along strike of the mineralised zone. It intersected a narrow zone of low grade zinc mineralisation (7m at 0.35% Zn between 38 and 45m).
The true width is probably less, as the hole was drilled oblique to the mineralised zone.
Apart from TSDRC007, zinc intercepts were generally of sub-economic grades. The VTEM conductors were explained by the presence of graphitic schists.
These, combined with the fact that the main zinc sulphide, sphalerite, is not conductive, demonstrate that EM is not an appropriate exploration tool for the prospect, based on the nature of the mineralisation encountered to date
Work to date has explained the VTEM conductors but has not yet eliminated the theoretical possibility that the zinc mineralisation may exist deeper within the Halls Creek Fault Zone as part of a system of replacement skarn-style mineralisation.
The drilling demonstrated the potential for replacement-type skarn mineralisation with the Halls Creek Fault Zone showing potential for skarns at depth.
The drilling extended zinc mineralisation at Little Mount Isa over an approximate 450m strike length.
Future drilling is likely to target the potential for small high grade shoots of mineralisation within the Little Mt Isa zone and also assess the prospectivity at depth with historical Ilmars data to be re-looked in the wake of new geological interpretation of Little Mount Isa and Halls Creek Fault Zone.
On the corporate front, Thundelarra has rationalised its portfolio of exploration ground. The annual overhead associated with work expenditure commitments, tenement rents, and rates has shrunk to manageable levels.
Cash at bank will also increase upon approval by shareholders of resolutions relating to the sale of Hayes Creek and to the placement to chairman Phil Crabb.
This would add a further $1,150,000 to cash reserves will become available, taking the effective cash balance up to about $1,500,000.
This would enable drilling to proceed initially earmarked for programs at Red Bore and at Allamber.
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