Ashton defines Buffalo Hills deposit

Delineation drilling by Ashton Mining of Canada (ACA-T) at the Buffalo Hills project in Alberta indicates that the prospective K252 kimberlite is irregularly shaped and smaller than first thought.

Ashton has no plans to collect a larger bulk-sample from the body.

Of the 36 kimberlites found to date, K252 has yielded, by far, the most interesting results. The pipe was discovered in March 2000 under 75 metres of glacial overburden. Unlike the other Buffalo Hills kimberlites, K252 has a weak magnetic signature and was originally identified through an airborne electromagnetic (EM) survey. It was further defined with ground EM, gravity and seismic surveys.

An initial, 226.9 kg sample of drilled material yielded 244 microdiamonds and 19 macrodiamonds (the latter is here defined as exceeding 0.5 mm in at least one dimension). Ten of the macros measured greater than 0.5 mm in two dimensions, including four stones that exceeded 1 mm in two dimensions. The largest recovered diamond measured 2.35 by 2.19 by 0.63 mm. Two distinct phases were recognized: an upper fine-to-medium-grained volcaniclastic kimberlite, and an underlying kimberlite breccia.

Additional drilling was performed in October 2000, resulting in the collection of a 1.28-tonne sample of volcaniclastic kimberlite from four core holes.

Wanting to recover only larger stones, Ashton processed the 1.28-tonne sample by dense media separation (DMS) and recovered 0.85 carat of diamonds larger than a 0.8-mm sq. mesh screen size, for a preliminary grade of 0.662 carat per tonne (or 66.2 carats per 100 tonnes). The largest diamond recovered was a colourless composite crystal weighing 0.36 carat.

Encouraged by the presence of larger stones in a small amount of sample, Ashton collected a much larger, 22.8-tonne drill sample from K252 in March 2001. The mini-bulk sample was collected from three large-diameter reverse-circulation (RC) holes drilled to depths of just over 200 metres, near the pipe’s interpreted centre. The 22.8-tonne sample yielded a 12.54-carat parcel of diamonds greater than 0.8 mm in size, for a sample grade of 0.55 carat per tonne. The two largest stones included a 0.94-carat composite crystal recovered from the kimberlite breccia, and a 0.65-carat diamond from the volcaniclastic phase. Both were colourless.

Based on previous drilling and a geophysical signature measuring 150 metres in diameter, Ashton interpreted K252 pipe to be about 2 hectares in size. This winter, Ashton probed the outer edges of the geophysical anomaly with seven 12-cm-diameter RC holes to depths of 200 metres. Only two of the holes encountered “significant” intercepts of kimberlite, indicating that the body is likely less than 2 hectares in size. Activity at K252 will not resume until after Ashton compiles and evaluates all its data.

In other work, Ashton further tested the K6 kimberlite, which was discovered in early 1997 and sits under thin cover 500 metres southeast of K252. The K6 first returned 33 micros and three macros from 153.7 kg of sample. The geophysical anomaly at K6 measures roughly 250 by 600 metres and consists of two magnetic highs, with their peaks 400 metres apart. A follow-up, 13.96-tonne mini-bulk sample, collected from drilling and surface pits near the centre of northern magnetic anomaly, returned 0.876 carat of diamonds, for an implied grade of 6.3 carats per 100 tonnes. A clear yellow diamond weighing 0.76 carat was recovered.

A ground gravity survey recently identified a strong gravity signature associated with K6. The centre of the gravity anomaly is associated with an untested magnetic low on the northern portion of K6, about 100 metres south of the magnetic high peak. Ashton tested the centre of the gravity anomaly with a single, vertically drilled RC hole that was still in kimberlite when it was shut down at 200 metres of depth.

The six tonnes of sample recovered from K6 will be tested for macros using Ashton’s plant in North Vancouver. Results are expected in the second quarter.

Meanwhile, Ashton recently drill-tested one new geophysical anomaly at Buffalo Hills without intersecting kimberlite.

Situated 300 km north of Edmonton, the Buffalo Hills diamond project is a joint venture among Ashton, Alberta Energy (ACE-T) and Pure Gold Minerals (PUG-T). Ashton and Alberta Energy each hold a 45% interest, with the remainder held by Pure Gold.