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Use of a simplified Mahalanobis distance approach to constrain the dispersion and provenance of Cr-pyrope populations at the Chidliak kimberlite province, Nunavut, Canada

  • Herman S. Grütter
  • Jennifer A. Pell
  • Catherine E. Fitzgerald
Original Paper
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Abstract

Exploration for diamond-bearing kimberlites in the Chidliak project area by Peregrine Diamonds has generated a grid-like till sampling pattern across four discrete areas of interest totalling 402 km2 that is densely populated with research-grade compositional data for 10,743 mantle-derived Cr-pyrope garnets. The available dataset is well suited to statistical analysis, in part due to the relatively unbiased spatial coverage. Previous workers showed empirically that the TiO2 and Mn thermometry (Ti-TMn) attributes of Cr-pyrope populations at the Chidliak project may serve as source-specific “fingerprints”. In this work, we employ a simplified version of the multivariate Mahalanobis distance technique to formally examine the variability of, and differences between, Ti-TMn attributes of Cr-pyrope subpopulations recovered from a Laurentide-age glaciated terrain that also contains 30 known kimberlites within the four areas of interest. We show the simplified Mahalanobis distance approach enables accurate discrimination of Cr-pyrope subpopulations with subtly to distinctly different Ti-TMn attributes, and permits proper demarcation of their respective kimberlite source(s), specifically in areas with straightforward glacial histories. Redistribution and blending of Cr-pyrope subpopulations from known kimberlite sources is also observed, and typifies areas at Chidliak with complex late-glacial histories. Our results support <1 km horizontal scale subtle to obvious variability in the proportions of TiO2-rich and high-temperature (> 1100 °C) Cr-pyropes between closely spaced kimberlite source(s) and also between physically adjacent magma batches within single kimberlite pipes. The local scale variability is attributed to protokimberlite fluid or melt interacting with, and metasomatizing discrete conduits within, the ambient diamond-facies peridotitic mantle at times closely preceding eruption of kimberlite magma batches at Chidliak.

Keywords

Multivariate geostatistics Kimberlite indicator mineral Diamond exploration Cr-pyrope garnet Mantle fluid/melt interaction 

Notes

Acknowledgements

The authors acknowledge support and encouragement provided by Peregrine Diamonds Limited, and the permission granted to publish these results. Overburden Drilling Management Limited and C.F. Mineral Research Limited are thanked for providing the year-on-year consistent, research-grade indicator mineral data that underpin our work. We are grateful to the Editor-in-Chief of the journal for meticulous editing, rapid turn-around and constructive comments to improve overall presentation. Two anonymous peers also provided brief comments.

Supplementary material

710_2018_578_MOESM1_ESM.pdf (3.4 mb)
ESM 1 (PDF 3529 kb)

References

  1. Averill SA, Huneault RG (2003) Controlling the quality of kimberlite indicator mineral processing using indicator mineral spikes. The Association of Applied Geochemists, Explore. Newsletter 119:19–21Google Scholar
  2. Averill SA, McClenaghan MB (1994) Distribution and character of kimberlite indicator mineral in glacial sediments, C14 and Diamond Lake kimberlite pipes, Kirkland Lake, Ontario. Geol Surv Canada Open File 2819, 52 pGoogle Scholar
  3. Broster B, Munn M, Pronk A (1997) Inferences on glacial flow from till clast dispersal, Waterford area, New Brunswick. Géog Phys Quatern 51:29–39Google Scholar
  4. Clark R (1967) A contribution to glacial studies of the Malham Tarn area. Field Stud 2:479–491Google Scholar
  5. Clayton KM (1966) The origin of the landforms of the Malham area. Field Stud 2:359–384Google Scholar
  6. Creighton S (2009) A semi-empirical manganese-in-garnet single crystal thermometer. Lithos 112S:177–182CrossRefGoogle Scholar
  7. Giuliani A, Kamenetsky VS, Kendrick MA, Phillips D, Wyatt BA, Maas R (2013) Oxide, sulphide and carbonate minerals in a mantle polymict breccia: Metasomatism by proto-kimberlite magmas, and relationship to the kimberlite megacrystic suite. Chem Geol 353:4–18CrossRefGoogle Scholar
  8. Grütter HS, Tuer J (2009) Constraints on deep mantle tenor of Sarfartoq-area kimberlites (Greenland) based on modern thermobarometry of mantle-derived xenocrysts. Lithos 112S:124–129CrossRefGoogle Scholar
  9. Grütter HS, Apter DB, Kong J (1999) Crust–mantle coupling: evidence from mantle-derived xenocrystic garnets. In: Gurney JJ et al (eds) Proceedings of the 7th International Kimberlite Conference, vol 1. Red Roof Design, Cape Town, pp 307–313Google Scholar
  10. Grütter HS, Gurney JJ, Menzies AH, Winter F (2004) An updated classification scheme for mantle-derived garnet, for use by diamond explorers. Lithos 77:841–857CrossRefGoogle Scholar
  11. Januszczak N, Seller MH, Kurszlaukis S, Murphy C, Delgaty J, Tappe S, Ali K, Zhu J, Ellemers P (2013) A multidisciplinary approach to the Attawapiskat kimberlite field, Canada: accelerating the discovery-to-production pipeline. In: Pearson D et al (eds) Proceedings of 10th International Kimberlite Conference, vol 2. Springer, New Delhi, pp 157–171CrossRefGoogle Scholar
  12. Johnson C (2014) Fingerprinting Quaternary subglacial processes on Hall Peninsula, Baffin Island, using multiproxy data. Masters thesis, University of Waterloo, CanadaGoogle Scholar
  13. Johnson C, Ross M, Tremblay T (2013) Glacial geomorphology of north-central Hall Peninsula, southern Baffin Island, Nunavut. Geol Surv Canada Open File 7413, 57 ppGoogle Scholar
  14. Malkovets VG, Griffin WL, O'Reilly SY, Wood BJ (2007) Diamond, subcalcic garnet and mantle metasomatism: kimberlite sampling patterns define the link. Geology 35:339–342CrossRefGoogle Scholar
  15. Neilson S, Grütter H, Pell J, Grenon H (2012) The evolution of kimberlite indicator mineral interpretation on the Chidliak project, Baffin Island, Nunavut. Tenth International Kimberlite Conference Extended Abstract #162, 5 ppGoogle Scholar
  16. Pell J, Grütter H, Neilson S, Lockhart G, Dempsey S, Grenon H (2013) Exploration and discovery of the Chidliak kimberlite province, Baffin Island, Nunavut: Canada’s newest diamond district. In: Pearson D et al. (eds) Proceedings of 10th International Kimberlite Conference, vol 2, Springer, New Delhi, pp 209–227Google Scholar
  17. Teknomo, K (2014) Similarity Measurement. http://people.revoledu.com/kardi/tutorial/Similarity/MahalanobisDistance.html. Accessed on May 30, 2014

Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  • Herman S. Grütter
    • 1
  • Jennifer A. Pell
    • 1
  • Catherine E. Fitzgerald
    • 1
  1. 1.Peregrine Diamonds Ltd.VancouverCanada

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