Smashing Diamond Jeff Harris

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					Smashing Diamond




              Jeff Harris
                                     Centenary Diamond

                                     Uncut = 599cts. Cut = 274cts

                                     Insured for US$100 million




  2.0cm




Boart diamond - Carbonado

 Value about US$ 88 cents per cts

 Little need for insurance!
                                    Steve Haggerty
              octahedron




tetrahedron
50 µm
    Former β- and γ-phase olivine inclusions?




             Olivine
             KK-109



Ex-solved phase has a spinel mineral chemistry
200km




        500km
Natural Rough Diamond Production (Mct)



                 2004   2005    2006
  Australia      24.3    34.3    28.2
  Zaire          30.9   30.3    28.0
  Botswana       31.1   31.9    32.0
  CIS (Russia)   35.6   38.0    38.4
  South Africa   14.3   15.8    15.4

                  84%    84%    83%
Natural Rough Diamond Production (Mct)


                2004   2005   2006
  Angola        6.1    7.0    7.8
  Canada        12.6   12.3   12.4
  West Africa    2.3    2.3    2.1
  Namibia       2.0    1.9    2.2
  C.A.R.        0.4    0.4    0.4

                14%    13%    15%
  Mct,s         163    178    171
                       Inclusion Types
Peridotitic (P-type)   Eclogitic (E-type)       Websteritic (W-type)

 Olivine               Clinopyroxene               Clinopyroxene
 Enstatite             Pyrope-almandine gnt        Enstatite
 Pyrope garnet         Sulphides                   Py-Al garnet
 Chromite
 Sulphides             Kyanite
                       Coesite              Recent Discoveries
 Chrome diopside       Rutile
 Clouds                Clouds               Majorites
 Mg – ilmenite         Ilmenite             Ferropericlases
 Zircon                                     Ruby
 Native iron                                Moissanite
100 µm
300µm
200 µm
0.20mm
50 µm
200 µm
          86   88       90    92   94   96   98
     14

          Lherzolitic                                                                                    olivines
     12

     10

     8
 N
     6

     4
                                                         Harzburgitic
     2
                                                    30
     0
          86   88       90    92   94   96   98
                             Mg#
                                                  N 20


                                                                                                0
                                                    10
                                                                                              140
                                                                                                    Unknown
                                                                                              120   paragenesis
                                                     0
                                                     0
                                                         86   88   90    92   94   96   98    100
                                                                        Mg#

                                                                                             N 80
                                                                                               60

                                                                                               40
Lherzolite: mode at 92.1 #Mg. Green dashed line
                                                                                               20
Harzburgitic: mode at 93.2 #Mg. Blue dashed line
                                                                                                0
Unknown (no gnt or cpx): mode at 92.9 #Mg                                                           86   88   90    92   94   96   98
                                                                                                                   Mg#
         20                  Wehrlitic
                             Lherzolitic
                             Harzburgitic
                             Websteritic
         15                  Eclogitic

Cr2O 3
         10


         5


         0
              0   5   10     15      20
                       CaO                  Garnet
Damtshaa
                            S              Peridotitic
        FeS 2                               70
                                           Eclogitic
       Pyrite        Monosulpide           Unknown
                     solid solution
  Fe 0.83-1S                                    60
Pyrrhotite
       50                                           50 Ni3S2
                                                         Heazel-
                          (FeNi)9S 8                     woodite
                         Pentlandite
  40
  Fe           10   20     30         40      50         Ni
                  P-Type




                           Steve Richardson, Cape Town




Thomas Stachel, Edmonton




                                                         150 µm
                           E-Type
Inclusion Equilibration Temperatures and Pressures


          Multiple Mineral Geothermometers
          • garnet + olivine (P-type)
          • garnet + orthopyroxene (P-type)
          • garnet + clinopyroxene (P- and E-type)

          Single Mineral Geothermometers
          • Zn in Cr-spinels (P-type)

          Single Mineral Geothermobarometers
          • Cr in garnets (P-type)
          • Ca in P-type clinopyroxene

          •   Nitrogen in diamonds
  0
         Peridotitic                 TO’Neill 79
         N=142                       (Ol-Grt,
         Mean=1158                   50 kbar)
 30            ±106°C

                                 Harzburgitic
                                                       900      1000      1100   1200   1300     1400
N 20                               Lherzolitic        40
                                                            Eclogitic                   TKrogh
                                                            N=117                       (Cpx-Grt,
 10                                                   30    Mean=1174                   50 kbar)
                                                                 ±99°C


  0
  0                                                           Argyle
                                                     N 20     N=49
   900      1000   1100     1200     1300     1400
                        T [°C]                                1241±62°C

                                                      10



                                                       0
                                                        900     1000      1100   1200   1300     1400
                                                                            T [°C]
wet


      dry
Diamond Genesis and Eruption Ages       200 µm




 Sulphide Inclusions : Re – Os
                      U - Pb




 Garnet Inclusions : Nd - Sm
                                      200 µm




 Clinopyroxene Inclusions : Ar - Ar

                                                 0.45 mm
       Genesis ages from garnets and clinopyroxenes
                  E-type (Ga)      W-type(Ga)       P-type (Ga)           Eruption age
South Africa
   Finsch                                          3200±100 (M)       118
   Finsch 1443±166 (M)                                                             118
   Finsch 1657±77 (M)                                                              118
   Finsch                   2111±120 (M)                              118
   Finsch 1580±60 (I)                                                             118
   Kimberley                                                3200±100 (M)           95
   Premier            1150±60 (I)                                              1180±30
   Premier                                                  1930±60 (I)           1180±30
   Venetia                                                  2300±40 (I)                      519
Botswana
   Orapa 990±50 (I)                                                       93
   Jwaneng            1540±20 (I)                                                235±4
Australia
   Argyle 1580±60 (I)                                                           1129±9
Russia
   Udachnaya                                                2010±60 (I)                     361±6

          M = model age         I = isochron age
              Genesis ages from Sulphides

                  E-type (Ga)     P-type (Ga)   Eruption age
South Africa
  Koffiefontein    1048±120                          90
  Koffiefontein     ≈ 1500                           90
  Koffiefontein    2600±30                           90
  Kimberley        2900                              95
Botswana
  Orapa            1000                              93
  Orapa            2500 to 3000                      93
  Jwaneng          1500                              235±4
  Jwaneng          2900                              235±4
Canada
  Panda                             3520±170         53
    INFORMATION FROM THE INCLUSIONS and
                 DIAMONDS

INCLUSIONS
• Mineral abundances
• Major element chemical compositions
• Trace element compositions
• Temperature and pressure of diamond formation
• Genesis and eruption ages of the diamonds

DIAMONDS
• Carbon and nitrogen isotopes
• Nitrogen contents and nitrogen aggregation states
    Carbon and Nitrogen Characteristics

Below 670 km
• A mantle value of -5‰ δ13C. No Nitrogen.
Between 670 and 410km
• A variable value -3.5‰ to -24 ‰ δ13C. No Nitrogen.
Between 410 and 150km
• P-type : Mostly mantle values (-5‰ δ13C).
  200ppm Nitrogen.
• E-type : Variable (+3 ‰ to -30 ‰ δ13C).
  300ppm Nitrogen.
                      300 µm

2.0cm




        Thank you


                    Anetta Banas, Edmonton

				
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