T20 Gemological Research in the 21st Century—Characterization, Exploration, and Geological Significance of Diamonds and other Gem Minerals

Sunday, 22 October 2017
8:00 AM - 12:00 PM
Skagit 3

ARE THERE "COLOMBIAN-TYPE" EMERALDS IN CANADA'S NORTHERN CORDILLERA?

Paper number: T20-12
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

  • Donald J. Lake Presenting Author
    The University of British Columbia, Vancouver, BC
  • Lee Groat
    University of British Columbia, Vancouver, BC

Abstract

Assessing the potential for “Colombian-type” sedimentary-hydrothermal beryl (var. emerald) occurrences in the northern Cordillera of Canada’s Yukon and Northwest Territories is necessary to fully evaluate emerald potential in the area, and refine gemstone exploration methods. Previously, emerald exploration has focused on Type-I “granite-related” emerald deposits (e.g.Tsa da Glisza), however no study to date has been directed toward the potential for Colombian-type hydrothermal emerald in this region.

We compared specific features of two unique beryl showings in the Mackenzie Mountains, NT– Mountain River (ca. 345 Ma), and Lened (ca. 100 Ma)– to the Colombian emerald deposit model. Mountain River green beryl is the first known “Colombian-like” beryl outside of Colombia. Beryl-fertile sulfate brines followed deep-seated regional thrust structures, as in the Colombian deposits. Skarn-hosted emerald veins at the Lened showing sourced emerald chromophore elements (V and to a lesser extent Cr) from black mudstone of the regionally extensive Earn or Road River Group, suggesting that these sedimentary units are a significant regional reservoir of emerald chromophore elements V and Cr. We propose that the structural and chemical components required for Colombian-type emerald mineralization are present in the northern Cordillera and merit further exploration based on evidence from these known sites.

To identify targets for Colombian-type emerald exploration, we have applied Na/K, REE, and other element ratios (that have located emerald-mineralized drainages in Colombia) to regional stream sediment geochemical data from Yukon and Northwest Territories. Several anomalies have been identified; portions of which have been field-checked. Regional-scale stream sediment sampling is too coarse to effectively identify such localized occurrences, however preliminary results suggest that there is potential for Colombian-type emerald mineralization.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-304729

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