© 2012 Scott-Smith Petrology Inc.
Sub-Division of Kimberlites:Mineralogical and Textural
Barbara H. Scott Smith
• Mineralogical Classification• identifies different batches of magma
- mineralogy of a rock or a unit reflects composition of melt
• Textural Classification• identifies facies
- characteristics of a rock or a unit reflect the conditions of its origin, i.e. near surface final emplacement processes
Kimberlite Sub-Division
A B CMonticellite 58 41 11Phlogopite 2 29 23Calcite <1 0 25Serpentine 13 14 22Spinel 17 8 13Perovskite 9 6 4Apatite <1 2 2
Total 100 100 100
• Main Subdivision: most dominant groundmass mineral
• Further subdivision: other groundmass minerals which exceed 2/3 modal % of the dominant mineral
A: monticellite kimberliteB: phlogopite-
monticellite kimberliteC: serpentine-phlogopite-
calcite kimberlite
Kimberlite Mineralogical ClassificationModal Analyses Calculated on an Olivine-Free Basis
Skinner and Clement 1979
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Kimberlite MagmasAscend to Surface as Separate Batches of Magma
• Mineralogical Classification• identifies different batches of magma
- mineralogy of a rock or a unit reflects composition of melt
• Textural Classification• identifies facies
- characteristics of a rock or a unit reflect the conditions of its origin, i.e. near surface final emplacement
Kimberlite Sub-Division
Kimberlite Textural-Genetic Classification
• Textures result from final emplacement processes
• Near surface kimberlite magmas comprise
Solids: xenoliths, macrocrysts, phenocrysts
Silicate melt: groundmass
Volatiles: CO2 and H2O
• Each behaves differently in contrasting processes
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Pu’u ‘O’o, Hawaii 1986 Photo: USGS JD Griggs
Hypabyssal Kimberlite: 25% Mixed Grain Sizes of Olivine Macrocrysts (>1mm)
Schematic Olivine Macrocryst Distributions
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Kimberlite Textural-Genetic ClassificationKimberlite Magma Texture
Coherent Magmaclastic
Magmaclasts Interclast MatrixUniform Groundmass
± Segregations of Fluid in Melt (FiM) Non-MagmaticMagmatic
ICK
KPK FPK RVK
Segregations ofMelt in Fluid (MiF)
DiscreteOlivines
Melt-bearingPyroclasts
Interpretation: Rock TypesCK ECK - Extrusive Coherent (mainly lava)
ICK - Intrusive Coherent (mainly HK)VK KPK - Kimberley-type Pyroclastic
FPK - Fort a la Corne-type Pyroclastic RVK - Resedimented Volcaniclastic after Scott Smith 2007
after Field and Scott Smith 1998
(Xenoliths)ECK
HKlava
KPK-type FPK-type
Coherent(replaces magmatic)
Fort a la Corne 175Finlay, Hardy Lake, Lac de Gras
Magmaclastic
Kimberlite Textural-Genetic ClassificationKimberlite Magma Texture
Magmaclastic
Magmaclasts Interclast Matrix
Fort a la Corne 175 Slab FOV=13mm FalC 118 Thin section FOV=4mm FalC 169
Kimberlite Textural-Genetic ClassificationKimberlite Magma Texture
© 2012 Scott-Smith Petrology Inc.
FPKFOV=4mm FalC 152
HKFOV=10mm Finsch, RSA
KPKFOV=0.6mm Camsell Lake
RVKFOV=13mm Hardy Lake 02
Kimberlite Textural-Genetic ClassificationKimberlite Magma Texture
Magmaclastic
Magmaclasts Interclast Matrix
Non-MagmaticMagmaticSegregations ofMelt in Fluid (MiF)
Melt-bearingPyroclasts
KPK-type FPK-type
DiscreteOlivines
DiscreteOlivines
FPKKPK RVKHK
Kimberlite Textural-Genetic ClassificationKimberlite Magma Texture
Magmaclastic
Magmaclasts Interclast Matrix
Non-MagmaticMagmaticSegregations of Melt in Fluid (MiF)
Melt-bearingPyroclasts
KPK-type FPK-type
Kimberlite Textural-Genetic ClassificationKimberlite Magma Texture
Coherent Magmaclastic
Magmaclasts Interclast MatrixUniform Groundmass
± Segregations of Fluid in Melt (FiM) Non-MagmaticMagmatic
ICK
KPK FPK RVK
Segregations ofMelt in Fluid (MiF)
DiscreteOlivines
Melt-bearingPyroclasts
Interpretation: Rock TypesCK ECK - Extrusive Coherent (mainly lava)
ICK - Intrusive Coherent (mainly HK)VK KPK - Kimberley-type Pyroclastic
FPK - Fort a la Corne-type Pyroclastic RVK - Resedimented Volcaniclastic after Scott Smith 2007
after Field and Scott Smith 1998
(Xenoliths)ECK
HKlava
KPK-type FPK-type
© 2012 Scott-Smith Petrology Inc.
Kimberlites in CanadaTextural Classification
HK (only)• Snap Lake, NWT • Doyle Lake, NWT• MZ Lake, NWT• Wales Island, Nunavut• Cross, BC• Wemindji, Quebec
1: KPK (+HK)• Gahcho Kue, NWT • Camsell Lake, NWT• Renard, Quebec• Aviat, Nunavut• Qilalugaq, Nunavut
2: FPK• Sturgeon Lake, Saskatchewan • Fort a la Corne, Saskatchewan • Victor/Attawapiskat, Ontario• Candle Lake , Saskatchewan• Mountain Lake, Alberta • Buffalo Hills, Alberta• Birch Mountains, Alberta• Jericho, Nunavut• Knife Lake, Nunavut
3: RVK• Lac de Gras, NWT
TerminologyHK - Hypabyssal (intrusive)
(1) KPK - Kimberley-type PK(2) PK - Fort a la Corne-type PK (3) RVK - Resedimented
Volcaniclastic
Pipe Classes after Skinner and Marsh (2004)
Canadian Kimberlite Geology: OverviewBased on First Decade of Data
Updated 2003
HK
2: FPK 3: RVK 1: KPK 2: FPK2: FPK
Scott Smith 2006
FPK
KPKKPKHK
RVK
Volcaniclastic Kimberlites 1:Fort à la Corne-type
Pyroclastic Kimberlites (FPK)
Barbara H. Scott Smith
© 2012 Scott-Smith Petrology Inc.
Fort à la Corne, SaskatchewanType Area Fort a la Corne-type Pyroclastic Kimberlite - FPK
(A) (B) Emplacement Processes
(1) Crater excavation(2) Crater infill
(C) Diamond distribution
FPK
Scott Smith et al. 1996, 1998; Scott Smith 2008
FPK
= FPKkimberlite
magma
= PK
= VK
Fort à la Corne, SaskatchewanMagmaclastic Kimberlite
Thin section FOV=4mm FalC 169Slab FOV=13mm FalC 118
Fort à la Corne, SaskatchewanMagmaclasts = FPK-type Melt-Bearing Pyroclasts
TS FOV=4mm FalC 145
as above xN
TS FOV=4mm FalC 122
TS FOV=4mm FalC 152
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Fort à la Corne, Saskatchewan What are the Magmaclasts?
• Evidence• Fluidal fragments of typical kimberlite magma• Smooth and often amoeboid shapes indicating surface tension
control (low viscosity as a few basalts and carbonatites)• Vesicles• Quenched to ‘glassy’ groundmass• Composite magmaclasts• Rare broken magmaclast• Adjacent examples of overall similar magmaclasts are different• (Different to KPK-type magmaclasts or melt segregations)
• Conclusions• extrusively formed fragments of fluidal magma, or• melt-bearing pyroclasts• liberated FPK-type melt-bearing pyroclasts
FalC 121
Fort à la Corne, SaskatchewanOlivine = Discrete Crystals
Fort à la Corne, SaskatchewanOlivine = Discrete Crystals
Slab FOV=13mm FalC 145
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Fort à la Corne, SaskatchewanMagmaclasts = FPK-type Melt-Bearing Pyroclasts
TS FOV=4mm FalC 145
as above xN
TS FOV=4mm FalC 122
TS FOV=4mm FalC 152
Fort à la Corne, Saskatchewan What are the Discrete Grains?
• Evidence• associated with melt-bearing pyroclasts containing similar olivines,
garnets etc.• derived from same kimberlite-magma• some broken grains• sorted• clast supported textures
• Conclusions • crystal pyroclasts dominated by olivine • separated from fluidal magma (both melt and fluids) during eruption • pyrocrysts• subaerial liberated pyrocrysts
Fort à la Corne, SaskatchewanMode of Deposition
Note: deposition is within pipe below original surface
• Limited Options are • Primary pyroclastic (FPK)• Resedimented / Reworked (RVK)
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Fort à la Corne Bedding
Fort à la Corne, SaskatchewanWind Winnowing of FPK
Slab FOV=6mm Body 145, Fort a la CornePu’u ‘O’o, Hawaii 1986 Photo: USGS JD Griggs
Fort à la Corne, SaskatchewanEmplacement Processes
© 2012 Scott-Smith Petrology Inc.
Evidence
• Clast-supported textures
• Loosely packed textures
• Planar bedding, normal grading
• Megagraded beds, marker horizons
• Ballistic impact fragmentation and dropstone
• Lack of abrasion, breakage and fines
• Composite melt-bearing pyroclasts
• Clustering of xenolith type
• Phases of kimberlite representing batches of magma
Conclusion• primary pyroclastic fallout (column collapse)
Fort à la Corne, SaskatchewanMode of Deposition
Fort à la Corne, Saskatchewan Interclast Matrix: Carbonate Cement
• Contrasts with groundmass in melt-bearing pyroclasts
• Composed of carbonate, serpentine and some magnetite of magmatic origin
• Similar mineralogy to late-stage fluids of kimberlite magmas thus likely derived from kimberlite fluids
• Void infill crystallisation textures
• Pore space infilling by crystallisation of later kimberlitic fluids rising from vent through an uncemented pile of pyroclasts
• Rapid cementation indicated by lack of weathering
Fort à la Corne, Saskatchewan Interclast Matrix: Conclusions
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Fort à la Corne, Saskatchewan-type PK (FPK) Summary of Textures (and Geology)
• 25% olivine macrocrysts• 25% olivine phenocrysts• 50% melt + fluids
Typical Erupting Kimberlite (= HK)
Snap Lake Sheets 80km W of Gahcho Kué
Melt-Bearing Pyroclast-dominated FPK
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Fort à la Corne, SaskatchewanEmplacement Processes
Olivine Pyrocryst-dominated FPK
macrocrysts
phenocrysts
(ash from melt)
macrocrystic ol pyrocryst FPK
70-103 Ma.
FPK Summary
© 2012 Scott-Smith Petrology Inc.
Volcaniclastic Kimberlites 2:Resedimented
Volcaniclastic Kimberlites (RVK)
Barbara H. Scott Smith
Canadian Kimberlite Geology: OverviewField And Scott Smith (1999) Based On First Decade Of DataPipe Classes (1,2,3) From Skinner And Marsh (2004)
Updated 2003
HK
2: FPK 3: RVK 1: KPK 2: FPK2: FPK
Scott Smith 2006
FPK
KPKKPKHK
RVK
Lac de gras, NWTMode of Deposition
Note: deposition is within pipe below original surface
• Limited Options are • Primary pyroclastic (FPK)• Resedimented / Reworked (RVK)
• major from crater rim/wall – shallow large bodies• minor within crater – unlikely to be detected
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PK
Koala PK FOV=7mm
DO27 PK FOV=1.6mm xN
FPK
Lac de Gras Pipe Infill
Scott Smith 2006
RVK
Hardy Lake 2 FOV=12mm
Lac de Gras Pipe Infill
Scott Smith 2006
Mudstone
Ekati
Lac de Gras Pipe Infill
Scott Smith 2006
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RVK
Hardy Lake 2
RVK
Lac de Gras Pipe Infill
Scott Smith 2006
RVK
Hardy Lake 2
RVK
Lac de Gras Pipe Infill
Scott Smith 2006
Panda Open Pit, Ekati
RVK
Lac de Gras Pipe Infill
Scott Smith 2006
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RVK
Lac de Gras Pipe Infill
Scott Smith 2006
Moss and Russell 2006
FPK
Lac de Gras Pipe Infill
Scott Smith 2006
Lac de Gras Pipe Infill
Scott Smith 2006
After Nowicki et al. 2004 Dyck et al. 2004
McKinlay et al. 1998
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RVKSummary
48-75 Ma.
After Nowicki et al. 2004 Dyck et al. 2004
McKinlay et al. 1998
macrocrystic ol pyrocryst FPK
kimberlite magma
Canadian Kimberlite GeologyEmplacement Summary: Graded Olivine Pyrocryst FPK
ol pyrocryst FPK
Canadian Kimberlite GeologyEmplacement Summary: Olivine Pyrocryst FPK
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ol pyrocryst FPK
country rock (shale)
FPK
RVKRVK
Canadian Kimberlite GeologyEmplacement Summary: RVK
Kimberlite Textural-Genetic ClassificationStage 3a: Step 1 - Kimberlite Magma Texture
Coherent Magmaclastic
Magmaclasts Interclast MatrixUniform Groundmass
± Segregations of Fluid in Melt (FiM) Non-MagmaticMagmatic
ICK
KPK FPK RVK
Segregations ofMelt in Fluid (MiF)
DiscreteOlivines
Melt-bearingPyroclasts
Interpretation: Rock TypesCK ECK - Extrusive Coherent (mainly lava)
ICK - Intrusive Coherent (mainly HK)VK KPK - Kimberley-type Pyroclastic
FPK - Fort a la Corne-type Pyroclastic RVK - Resedimented Volcaniclastic after Scott Smith 2007
after Field and Scott Smith 1998
(Xenoliths)ECK
HKlava
KPK-type FPK-type
Canadian Kimberlite Geology: OverviewField And Scott Smith (1999) Based On First Decade Of DataPipe Classes (1,2,3) From Skinner And Marsh (2004)
Updated 2003
HK
2: FPK 3: RVK 1: KPK 2: FPK2: FPK
Scott Smith 2006
FPK
KPKKPKHK
RVK
© 2012 Scott-Smith Petrology Inc.
Canadian Kimberlite GeologySummary of Textures
Scott Smith 2008
Canadian Kimberlite GeologySummary Based on Second Decade of Data
Kimberlite Terminology and ClassificationSystematic Framework: Description, Classification, Interpretation