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TRACE ELEMENT PARTITIONING BETWEEN APATITE AND KIMBERLITE-LIKE MELTS
IMPLICATIONS TO KIMBERLITE MELT COMPOSITION AND EMPLACEMENT
AGS 2019
Richard Chow1, Yana Fedortchouk1, Phillipe Normandeau2
1.Department of Earth Sciences, Dalhousie University
2.Northwest Territories Geological Survey
Overview
1. Kimberlites
2. Problems
3. Methods
4. Results
5. Significance
6. Summary
• Variety of surface forms and lithological facies• Volcaniclastic
• Magmatic
• Ascent driven by exsolved fluid phase
(modified from Scott Smith et al., 2008)
Kimberlites
KPK
Present surface
FPK
Class 2 Class 3 Class 1
CK
(Sparks et al. 2013)
Problems• Exact composition of kimberlitic melt → UNKNOWN
• Contamination, emplacement dynamics, lack of quenched melts
• Estimates (Moussallam et al. 2016):
• 18-30 wt.% SiO2
• 30-45 wt.% MgO+CaO
• Similarities to carbonatites
• Model with partitioning data
• How carbonate or silicate rich?
• How are kimberlites emplaced?• Mechanisms involved (KPK)
Apatite
• Ca5(PO4)3(F,Cl,OH)
• Ca sites substitutions: Na, K, Mg, Mn, Fe, Sr, Ba, Pb, Th, U, REEs
• P site substitutions: C, Si, As, V, S
• Incorporates considerable amount of REEs, halogens
• Partitioning controlled by melt composition
• Apatite is commonly used as a tool for inferring processes occurring in other magmatic systems
𝑐𝑖𝑎𝑝𝑎𝑡𝑖𝑡𝑒
𝑐𝑖𝑚𝑒𝑙𝑡
= 𝐷𝑖
Apatite
• Problems:
• Discrepancy in existing data for carbonatitic melts
• No partitioning data available for kimberlitic-like silicate melts
• inaccurate modeling?
𝑐𝑖𝑎𝑝𝑎𝑡𝑖𝑡𝑒
𝑐𝑖𝑚𝑒𝑙𝑡
= 𝐷𝑖
0.0001
0.001
0.01
0.1
1
10
100
Li Be B Rb Cs Sr Ba Sc La Ce Pr Nd Sm Eu Gd Tb Dy Ho Y Er Tm Yb Lu Ti Hf Zr U Th V Nb Ta Pb
D A
pa
tite
/ M
elt
Silicate (Andesite) (Prowatke and Klemme, 2006)
Silicate (Andesite) (Watson and Green, 1981)
Carbonatite (Hammouda, et. al, 2010)
Carbonatite (Klemme and Dalpe, 2003)
Methods
• Piston-cylinder experiments• Temperature – 1150-1350°C
• Pressure – 1GPa
• Duration – 24 to 48H
• Test effect of various parameters on partition coefficient
• Temperature
• Role of water
• Pressure
• Oxygen Fugacity
Starting Mixture80 / 76 / 50 %
10 wt.% H2O
Durango / Synthetic Ap
20 / 50 %
4 % Trace Elements
Starting Mixtures
TA6 TA16 TA9 LS6 LS15 LS15G20 LS26
SiO2 16.59 23.13 22.68 16.95 15.21 28.79 14.37
Al2O3 3.90 5.41 5.29 3.54 3.17 5.62 3.00
TiO2 0.20 0.30 0.30
CoO 0.90 1.50 1.20
MgO 6.88 8.30 9.49 17.77 19.92 12.56 18.83
CaO 35.45 30.22 48.35 23.15 15.94 16.24 15.72
Fe2O3 22.23 20.76 15.67 17.15
Na2O 0.30 0.40 0.40 0.25 0.23 0.25 0.22
K2O 2.30 3.20 3.10 0.83 0.75 2.02 0.71
CO2 33.49 27.54 9.20 7.33 16.91 13.22 29.70
H2O 7.96 7.11 5.62 0.30
Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00
Lamproite derived* Leslie Kimberlite based: – 50% olivine + co2
(based on *Moussallam et al. 2016)
Methods
• Piston-cylinder• ½ and ¾ inch assemblies, NaCl cells, pyrex sleeve,
blass/steel plug and ring
• 3mm diameter Pt and Au-Pd capsules
• 2-3 capsules in each assembly (3/4”)
• Produce a quenched melt with apatite crystals
44 m
m
Blue: thermocouple, red: platinum
capsule, white: ceramic insulator,
black: graphite heater, yellow: Pyrex
insulator, grey: salt cell
Results
Ap
Sp
Melts
LS6 (80%) + Ap (20%) 1150°C 24H
LS15 (80%) + Ap (20%) 1150°C 24H
Sp
Ap
Fo
Carb
Di
Sp
Ap Fo
Carb
Di
LS26 (80%) + Ap (20%) 1150°C 24H
LS6 (80%) +Ap (20%)+ TRC (4%) + 5wt% H2O
• “Rims” of new apatite around Durango apatite
• Leslie composition not forming sizable melts and apatites
TA6 (46%) + SynAp (50%) + Trc (4%) + 10 wt.% H2O
Ap
Melt
TA6 (66%) + Dap (10%) + SynAp (20%) + Trc (4%)
Ap
Melt
Natural Leslie Kimberlite
Sp
Ap
Fo
Carb
Di
Experimental Leslie
LS15
K2O 0.056
CaO 47.944
Na2O 0.006
FeO 0.616
MnO 0.019
SiO2 4.454
P2O5 30.919
Cl 0.186
F 1.894
BaO 0.000
SrO 0.000
V2O5 0.129
SO3 0.028
Nd2O3 0.051
Pr2O5 0.398
Ce2O3 0.500
La2O3 1.447
TOTAL 88.387
TA6 TA9
K2O 0.092
CaO 50.586
Na2O 0.030
FeO 0.004
MnO 0.035
SiO2 2.820
P2O5 34.991
Cl 0.207
F 2.435
BaO 0.000
SrO 0.000
V2O5 0.086
SO3 0.001
Nd2O3 0.055
Pr2O5 0.454
Ce2O3 0.401
La2O3 0.712
TOTAL 92.911
K2O 0.065
CaO 51.566
Na2O 0.010
FeO 0.014
MnO 0.019
SiO2 2.288
P2O5 35.943
Cl 0.173
F 2.502
BaO 0.000
SrO 0.000
V2O5 0.076
SO3 0.045
Nd2O3 0.051
Pr2O5 0.420
Ce2O3 0.476
La2O3 0.406
TOTAL 94.055
K2O 0.04
CaO 48.41
Na2O 0.05
FeO 0.22
MnO 0.00
SiO2 1.37
P2O5 36.85
Cl 0.01
F 1.99
BaO 0.00
SrO 3.59
V2O5 0.16
Nd2O3 0.16
Pr2O5 0.51
Ce2O3 2.04
La2O3 1.55
Total 97.80
Natural Leslie
Apatite Composition
K2O 0.025
CaO 53.619
Na2O 0.073
FeO 0.011
MnO 0.044
SiO2 0.535
P2O5 39.504
Cl 0.194
F 2.349
BaO 0.080
SrO 0.111
V2O5 0.060
SO3 0.131
Nd2O3 0.090
Pr2O3 0.402
Ce2O3 0.387
La2O3 0.173
TOTAL 97.735
CAA
LS6 LS15K2O 0.043
CaO 47.739
Na2O 0.002
FeO 0.769
MnO 0.019
SiO2 4.913
P2O5 30.323
Cl 0.192
F 1.854
BaO 0.006
SrO 0.016
V2O5 0.066
SO3 0.033
Nd2O3 0.023
Pr2O5 0.402
Ce2O3 0.556
La2O3 1.355
TOTAL 88.168
K2O 0.057
CaO 48.236
Na2O 0.008
FeO 0.603
MnO 0.020
SiO2 4.991
P2O5 29.625
Cl 0.173
F 1.808
BaO 0.000
SrO 0.059
V2O5 0.118
SO3 0.058
Nd2O3 0.068
Pr2O5 0.419
Ce2O3 0.499
La2O3 1.604
TOTAL 88.118
K2O 0.038
CaO 51.781
Na2O 0.134
FeO 0.231
MnO 0.004
SiO2 0.347
P2O5 40.475
Cl 0.227
F 2.823
BaO 0.000
SrO 0.000
V2O5 0.084
SO3 0.367
Nd2O3 0.177
Pr2O5 0.356
Ce2O3 0.827
La2O3 0.420
TOTAL 97.662
K2O 0.020
CaO 52.218
Na2O 0.181
FeO 0.247
MnO 0.013
SiO2 0.351
P2O5 40.204
Cl 0.337
F 2.806
BaO 0.009
SrO 0.000
V2O5 0.053
SO3 0.328
Nd2O3 0.191
Pr2O5 0.407
Ce2O3 0.736
La2O3 0.365
TOTAL 97.897
24H 48H 24H 48H
Checking Equilibrium
Partition Coefficients
0.0001
0.001
0.01
0.1
1
10
100
Li Be B Rb Cs Sr Ba Sc La Ce Pr Nd Sm Eu Gd Tb Dy Ho Y Er Tm Yb Lu Ti Hf Zr U Th V Nb Ta Pb
D A
pa
tite
/ M
elt
Silicate (Andesite) (Prowatke and Klemme, 2006)
Silicate (Andesite) (Watson and Green, 1981)
Carbonatite (Hammouda, et. al, 2010)
Carbonatite (Klemme and Dalpe, 2003)
PC_178 Carbonate
PC_178 TA9
Significance
• Contribute to partition coefficient data of apatite
• Modeling kimberlite composition must rely on using D values for silicate and carbonatite melts • sensitive to the melt composition
• Improve constraints on:• Crystallization conditions and volatile behavior for kimberlite emplacement
• Kimberlite composition – silicic or carbonatitic?
• Apatite as a diamond preservation indicator• Quality associated with rapid ascent time
• Volatiles and fluid released from magma facilitates a rapid ascent
Summary
• Preliminary Conclusions:
• Experimental Leslie composition similar to natural
• SiO2 content of melt effecting REE compatibility?
• SiO2 content of apatite effecting REE compatibility?
• Further experiments and analysis planned
Acknowledgements
• Assistance in funding provided by:
• Dalhousie University Laser Ablation ICP-MS Laboratory
• Robert M. MacKay Electron Microprobe Laboratory