Kimberlite source elusive at Chesterfield Inlet

Shear Minerals (SRM-V) wrapped up this year’s exploration program on the Chesterfield Inlet diamond project in Nunavut still seeking the source of some promising indicator mineral anomalies and kimberlite float occurrences.

With the objective of discovering larger tonnage kimberlites, 10 geophysical targets were tested with 11 holes using a light-weight reverse circulation (RC) percussion rig. All 10 targets were explained by a non-kimberlitic magnetic source.

The Chesterfield Inlet project comprises a group of 35 mineral claims covering 280 sq. km in the Kivalliq region of eastern Nunavut. The project, owned 62.8% by Shear and the rest by Stornoway Diamond (SWY-T), is under option to the Canadian exploration subsidiary of Rio Tinto (RTP-N, RIO-L).

Rio Tinto Exploration Canada can earn an initial 51% interest by incurring exploration expenditures of $2 million before the end of 2012. Shear is the operator of the project during the initial earn-in period. This year’s program was budgeted at $500,000.

Chesterfield Inlet is immediately north of the much larger 2,400-sq.-km Churchill diamond project where Shear and Stornoway have discovered 88 kimberlites to date. The Churchill kimberlites include a series of significantly diamond-bearing, vertically emplaced dykes up to 4 metres wide that have returned sample grades of up to 2.18 carats per tonne.

“Analysis of the newly discovered kimberlite dykes and the previously drilled kimberlites led to the distinction of two types of kimberlites on the (Churchill) property, Type A (low interest) and Type B (high interest),” stated a 2010 technical report on the Churchill project, prepared by Apex Geoscience.

In October 2009, a three-day prospecting program was carried out on the Chesterfield Inlet claims. A total of 24 priority geophysical anomalies were prospected, as well as areas up-ice from previously identified high-interest, kimberlitic indicator mineral chemistry.

The Chesterfield Inlet claims are in an area called the North corridor where previous till sampling in 2003-06 showed anomalous indicator minerals, including pyrope garnet, eclogitic garnet, chrome diopside, ilmenite and chromite.

Shear discovered two occurrences of kimberlite float near and up-ice of the area of high-interest mineral chemistry. The kimberlite float was classified as low-interest Type A. The 2009 prospecting program also determined that three of the geophysical targets were caused by magnetic rocks other than kimberlite.

Earlier this year, a low-level airborne magnetic survey totaling 2,136 line km was flown over two blocks of the Chesterfield Inlet project. Preliminary interpretation of the block 1 data revealed 33 targets that required follow-up investigation.

During this year’s summer pro-g ram, field crews conducted ground magnetic surveying, prospecting and heavy mineral sampling on more than 35 high-priority targets, resulting in the discovery of four new kimberlite float occurrences.

Three of the new discoveries are clustered in a 600-metre area and are referred to as the SAZ kimberlite float. A 37-kg sample of weathered kimberlite fragments collected from a series of frost boils in a 65-metre area of SAZ yielded a previously reported 17 microdiamonds. The largest diamond, measuring 0.6 by 0.4 by 0.2 mm, was retrieved from a 0.3-mm sized screen.

“We are very encouraged by the discovery of four new kimberlite float occurrences as proof that ground prospecting and boots on the ground are the effective way to explore this project,” Pamela Strand, president of Shear, stated in a news release.

“A number of targets remain unexplained by ground prospecting and we are encouraged by the confirmation of diamonds in the SAZ float. We have additional work underway to determine the nature of the SAZ kimberlite float occurrences.”

Shear is trading around 8¢ in a 52-week range of 4.5¢-12¢. With 421.5 million shares outstanding, the junior is considering a rollback at a ratio not to exceed 10-to-1.

The company recently bought the past-producing Jericho diamond mine and related assets for $2 million cash, 80 million shares and a 2% royalty.