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