Deadmans Gully

Initial quantitative interpretation of magnetic data for the Windermere prospect was focused on the Deadman’s Gully anomaly where sub-cropping skarn with tin mineralisation has been intersected by previous explorers (see figure 1.). Note, that mineralized skarn was not intersected in holes 4, 5 & 6 thus the skarn may not be as extensive as shown?

The strong magnetic anomaly (750nT) is localised to an area of limestone outcrop within the Hodgkinson Formation at a granite contact. The TMI anomaly (figure 2.) is dipolar with a circular high flanked by an acute negative on the southern side of the anomaly. The previous drilling is located to the west of the anomaly, between the high and flanking magnetic low. The RTP anomaly pattern (figure 3.) is more symmetrical, but still retains a flanking low in the west.

Previous drilling has shown the skarn to be thin (~50m thick) and flat lying with a (E-W) width of 50 - 100m and strike length (N-S) of the order of 150 - 250m. The magnetic model was established with these dimensions and required a susceptibility value of the order of 0.25 SI units to simulate the two TMI anomaly profiles (figure 4) —drawn as E-W and N-S sections across the anomaly.

Also shown in figures 2. & 3. is the position of the model relative to the RTP and TMI contours. The model is located over the centre of the RTP anomaly closure, as would be expected, and is located between the TMI high and low closures. However, the model should be located over the outline of the skarn and drill holes, which indicates that the influence of remanence is required to shift the anomaly to the east. The presence of remanence was initially deducted from the shape of the RTP pattern, with a low to the west, and this has been confirmed by the model study.

Anomaly trend to North of Deadmans Gully

A series of magnetic highs are observed (figure 5.) to trend to the north of the Deadmans Gully anomaly, with the Nettle Granite to the west defined by a weak magnetic low. Two mapped outcrops of Hodgkinson Formation limestone are also noted within this low.

The magnetic highs have been labelled W1, W2 and W3 with an intense anomaly (2,000nT), at the northern end of the trend, noted as W4. Each anomaly has been modelled to ascertain if the variation in intensity is due to depth or susceptibility contrast.

Anomaly W1 comprises at least three overlapping sources but basically, a tabular, steeply dipping body that may be 200m wide and 300m long giving a broad anomaly high (100nT) with a low on the southern side. The body is modelled as having a moderate apparent susceptibility (0.023 SI) which would not reflect skarn or iron potential. The profiles also show an elevated background on the east and west that may be due to increased response in the Hodgkinson formation, but this has not been included into the model. The magnetic high thins in the north and is flanked by a local 50nT low, which has been modelled as a thin body of similar susceptibility (0.03 SI) and a possible skarn with remanence (related to the Wild granite).

The image below is of the Windermere/Deadmans Gully RTP Zones.

Click on the zone for an enlarged map. (eg. W1)