Analytical Sample Bundle Metadata

1995

GSC/TSD -1995-Contwoyto Lake 76E (south) Till: NTGO KIDD adjusted grain counts

Type: Interpreted data



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Download analytical data for this bundle in one of three formats, depending on the desired convention for treating values below the lower detection limit:

Bundle Description

The grain identifications reported in GSC Open File 3386 (table 2) are based on electron microprobe analyses.  The counts based on the original grain identifications by I and M Morrison were reported in Appendix 3.  The microprobe analyses identified several minerals which were mistakenly picked as kimberlite indicator minerals.  There are also several reported minerals which cannot be equated directly to minerals listed in the NTGO KIDD database.  The table below summarises the mapping from OF 3386 mineral identifications to the NTGO KIDD classification

  NTGO KIDD OF 3341
1 Diamond None reported
2 Pyrope (peridotitic) Pyrope (red)
3 Pyrope (eclogitic) Almandine + spessartine (orange)
4 Total garnet Pyrope + almandine + spessartine
5 Chrome diopside Cr diopside + high Cr diopside
6 Chromite Chromite
7 Ilmenite, picroilmenite Ilmenite + Mg ilmenite
8 Orthopyroxene Not mapped
9 Olivine Not mapped
10 Total Grains 2 + 3 + 5 + 6 + 7

Orthopyroxene was not picked by I and M Morrison, although it may appear as a result of mistaken identification.  Olivine was picked, but microprobe analysis showed that the two “olivine” grains in sample 94BCW2762 were actually grossular.  The mapping is designed to be consistent with data generated by other surveys.  It is problematic in that:

  • Most of the ilmenites have low Mg, and are not characteristic of kimberlites
  • Almost all of the almandines lie outside the field of eclogitic garnets (OF 3079, p21).

The classification of “low Cr diopside”, “Cr diopside” and “high Cr diopside” is also problematic.  In OF 3386, low Cr diopside is classed as a KIM (see table 2).

Minerals which were mistakenly picked as kimberlite indicator minerals include:

  • Staurolite
  • Apatite
  • Tourmaline
  • Rutile
  • Leucoxene (granular Fe,Ti oxides)
  • Spinel
  • Plagioclase
  • Zoisite

 

Sample Classification (Analytical)

IndexSample CountSurveySample TypePrep Lab MaterialControl RefUnknown SourceDuplicates count
27  Till sampling survey, Contwoyto Lake area, NTS 76E, Northwest Territories and Nunavut, 1994. (more) Till HMC separation (Canamera/DIP) No  No 

Analytical Package Description

Laboratory: No laboratory was required

Name: NTGO KIDD remapping (more)

The Northwest Territories Geoscience Office (NTGO) maintains the Kimberlite Indicator and Diamond Database (KIDD).  The KIDD database lists counts for ten quantities:

  • Diamond
  • Pyrope_P
  • Pyrope_E
  • Total_Garnet
  • ChrmDiop
  • Chrom/spin
  • Ilmn_Picro
  • OPX
  • Olivine
  • Total_Grains

This package permits a re-mapping from KIM counts in original reports to KIM counts that are compatible with KIDD.  The grain counts are for the 0.25 – 0.50 mm size fraction.  The weight of the sample that was processed is reported (typically about 10 kg).  The weight of the heavy mineral concentrate that was recovered from the 0.25 – 0.50 mm size fraction is also reported (typically a few tens of grams).

Analytical Suites:

IndexName
1  NTGO KIDD indicator mineral re-assignment

Analytical Methods:

IndexColumn NameSuite OrderMethod OrderSuite RepeatQuantityUnitsDetermination Limit
1  Wt_TblFeed    Wt  grams  
2  Wt_HMC_025_050    Wt  grams  
3  Diamond    Diamond (KIDD)  count  
4  Pyrope_P    Pyrope_P (KIDD)  count  
5  Pyrope_E    Pyrope_E (KIDD)  count  
6  Total_Garnet    Total Garnet (KIDD)  count  
7  ChrmDiop    ChrmDiop (KIDD)  count  
8  Chrom_Spin    Chrom_Spin (KIDD)  count  
9  Ilmn_Picro    Ilmn_Picro (KIDD)  count  
10  OPX  10    OPX (KIDD)  count  
11  Ol  11    Ol (KIDD)  count  
12  Total_Grains  12    Total_Grains (KIDD)  count  
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