Grattan Well
Location
The Grattan Well property is centred 20km north northwest of Leonora in the Mt Margaret Mineral Field. Access is via the sealed Leinster to Leonora road which runs parallel to the eastern margin of the property and provides excellent access. Within the property, the majority of the area can be accessed easily by four wheel drive using existing station and exploration tracks.
History
The Grattan Well property has undergone a number of exploration programs. Some of the early programs were poorly documented. Exploration included drilling, geochemical samples, mapping, aerial photography, and other methods, mainly for gold and nickel. These programs generated three main prospects being Mt Davis, Grattan Well and Eagle prospect.
Mount Davis Prospect
As a result of the above soil surveys, several areas of interest were identified including the Mount Davis prospect within Prospecting Licence 37/6466. Subsequent mapping and rock chip sampling demonstrated gold anomalism to be related to a north north-westerly trending sequence of mylonitic chert and sheared felsic and intermediate volcanics associated with the Mount George shear zone. An east-west Proterozoic dyke was found to cut the sequence close to the area of interest.
RC drilling followed, and 28 inclined holes for 2032 metres tested the 300m by 150m geochemically anomalous zone at 80m by 20m drill centres or closer spacing. Significant intercepts greater than 1 g/t gold have been obtained from 18 of the 28 RC holes drilled at Mount Davis.
Overall, the drilling outlined a north north-westerly trending bifurcating mineralised shear over a length of 210m that dips steeply to the west at its northern end and at an angle of 50º east at its southern end. Within the shear, three auriferous quartz veined lenses ranging in strike length from 20 to 50m over true thicknesses of 3 to 6m were found to pitch at 50º in a south-easterly direction.
Grattan Well Prospect
Further RAB and RC drilling was carried out at the Grattan Well prospect in the vicinity of earlier drilling. The highest RAB intersection was 3.10 g/t gold over 15m from 29m and the highest RC intersection was 1.66 g/t gold over 6m from 37m. This work, combined with earlier drilling investigations, showed that mineralisation has a strike extent of about 200m at the Grattan Well prospect, and that tonnage potential is limited.
Soil geochemistry in the area failed to detect the mineralisation identified by drilling, suggesting that the technique has limitations in areas of low relief covered by a veneer of transported sediment.
Eagle and Parrot Prospects
Other prospects identified as a result of geochemical surveys include the Eagle and Parrot prospects.
The Eagle prospect covers a northerly trending soil anomaly with values up to 69 ppb gold within Prospecting Licence Application 37/5610. This anomaly was investigated by two closely spaced RAB drill traverses. Two holes intersected mineralisation associated with sericite-chlorite alteration and quartz veining hosted by sheared high magnesium basalt intercalated with serpentinised ultramafics. The best result was 4.44 g/t gold over 1m from 23m.
At the Parrot prospect, situated one kilometre north northwest of the Grattan Well prospect, gold anomalism based on the analysis of resampled drill spoils was investigated by one RAB drill traverse. One hole intersected 2.67 g/t gold over 2m from 12m. This mineralisation is associated with sericite-hematite alteration and quartz veining in sheared komatiitic basalt.
Geology
The project is dominated by two lithogeology groups. The western sector is underlain by a north north-westerly trending sequence of metamorphosed high magnesium basalts, dolerite-gabbro intrusives, and ultramafic lenses. The eastern sector banded chert and jaspilite are enclosed by foliated volcaniclastic metasediments interlayered by felsic volcanics.
The regionally significant Clifford fault structure is interpreted to run through the project area in a north north-westerly direction. It marks the contact zone between mafic and ultramafic volcanic and intrusive rocks to the west and metasediments, banded chert horizons and felsic volcanic sequences to the east.
Exploration
The area has under gone geological reconnaissance, remote sensing, and geochemical surveys. The data is currently under review.
Outlook
At all the known prospects, late stage shearing is an important factor in providing favourable structural sites for gold mineralisation. The exploration work completed will be progressed to delineate drill targets, and to evaluate the project’s potential in context with Jupiter’s other Leonora Gold Projects.