Diagrams of Deposition and History

Kimberlites are most commonly found as carrot-shaped pipes, or less commonly, as dikes or as sills. There are three main zones associated with kimberlite pipes: the crater, diatreme, and hypabyssal root zones.

The presence and degree of preservation of these zones depends upon the level of erosion, the abundance of volatiles in the erupting magma, and the stability of the country rock. The kimberlites in Fort à la Corne have undergone very little erosion and glaciers have not scraped off the crater facies pyroclastics. This results in massive tonnage deposits in which most of the deposit is tabular in shape which leads to very low waste to ore stripping ratios. In contrast, the Kimberley and Jagersfontein pipes are smaller and have been eroded down to the diatreme.

Diagram of a Fort à la Corne Kimberlite

The following diagram emphasizes the size contrast (and potential ore tonnage) between a Fort à la Corne Kimberlite and a "pipe only" (Northwest Territories or South Africa) style Kimberlite.