ORIGINAL PAPER Geology and resource development of the Kelvin kimberlite pipe, Northwest Territories, Canada Martina Bezzola 1 & Casey M. Hetman 2 & Gareth Garlick 3 & Robert Creaser 4 & Michael Diering 2 & Tom Nowicki 3 Received: 1 December 2017 /Accepted: 16 August 2018 # Springer-Verlag GmbH Austria, part of Springer Nature 2018 Abstract The early Cambrian to late Neoproterozoic Kelvin kimberlite pipe is located in the southeast of the Archean Slave Craton in northern Canada, eight km northeast of the Gahcho Kué diamond mine. Kelvin was first discovered in 2000 by De Beers Canada. Subsequent exploration undertaken by Kennady Diamonds Inc. between 2012 and 2016 resulted in the discovery of significant thicknesses of volcaniclastic kimberlite that had not previously been observed. Through extensive delineation drilling Kelvin has been shown to present an atypical, steep-sided inclined L-shaped pipe-like morphology with an overall dip of 15 to 20°. With a surface expression of only 0.08 ha Kelvin dips towards the northwest before turning north. The body (which remains open at depth) has been constrained to a current overall strike length of 700 m with varying vertical thickness (70 to 200 m) and width (30 to 70 m). Detailed core logging, petrography and microdiamond analysis have shown that the pipe infill comprises several phases of sub-horizontally oriented kimberlite (KIMB1, KIMB2, KIMB3, KIMB4, KIMB7 and KIMB8) resulting from multiple emplacement events. The pipe infill is dominated by Kimberley-type pyroclastic kimberlite or BKPK^, historically referred to as tuffisitic kimberlite breccia or BTKB^, with less common hypabyssal kimberlite (HK) and minor units with textures transitional between these end-members. An extensive HK sheet complex surrounds the pipe. The emplacement of Kelvin is believed to have been initiated by intrusion of this early sheet system. The main pipe-forming event and formation of the dominant KPK pipe infill, KIMB3, was followed by late stage emplace- ment of additional minor KPK and a hypabyssal to transitional-textured phase along the upper contact of the pipe, cross-cutting the underlying KIMB3. Rb-Sr age dating of phlogopite from a late stage phase has established model ages of 531 ± 8 Ma and 546 ± 8 Ma. Texturally and mineralogically, the Kelvin kimberlite is similar to other KPK systems such as the Gahcho Kué kimberlites and many southern African kimberlites; however, the external morphology, specifically the sub-horizontal inclination of the pipe, is unique. The morphology of Kelvin and the other kimberlites in the Kelvin-Faraday cluster defines a new type of exploration target, one that is likely not unique to the Kennady North Project area. Extensive evaluation work by Kennady Diamonds Inc. has resulted in definition of a maiden Indicated Mineral Resource for Kelvin of 8.5 million tonnes (Mt) of kimberlite at an average grade of 1.6 carats per tonne (cpt) with an average diamond value of US$ 63 per carat (ct). Keywords Kimberley-type pyroclastic kimberlite . Hypabyssal kimberlite . Volcaniclastic . Diamonds . Emplacement . Tuffisitic kimberlite breccia Introduction The Kelvin kimberlite is located in the southeast of the Archean Slave Craton in the Northwest Territories of Canada, eight km northeast of the Gahcho Kué diamond mine (Fig. 1). Exploration work was conducted by De Beers Canada between 1997 and 2003. Approximately 30 holes were drilled in the area, with early drilling returning short, complex intersections dominated by HK. The near surface portion of Kelvin was first identified in 2000 through glacial till sampling and subsequent drill testing of a horizontal-loop electromagnetic (HLEM) anomaly, intersecting minor Editorial handling: B. Kjarsgaard * Martina Bezzola mbezzola@gmail.com 1 Aurora Geosciences Ltd., 3506 McDonald Drive, Yellowknife, NT X1A 2H1, Canada 2 SRK Consulting Inc., Oceanic Plaza, 22nd Floor, 1066 West Hastings Street, Vancouver, BC V6E 3X2, Canada 3 Mineral Services Canada Inc., 88 Lonsdale Ave #501, North Vancouver, BC V7M 2E6, Canada 4 Earth and Atmospheric Sciences, University of Alberta, 116 St. and 85 Ave, Edmonton, AB T6G 2R3, Canada Mineralogy and Petrology https://doi.org/10.1007/s00710-018-0631-6