first data for deep seated xenoliths and mantle geotherm

Page 1

First data for deep seated xenoliths and mantle geotherm of Zarnitsa kimberlite pipe, Daldyn, Yakutia.

Igor Ashchepkov (1), 1), Nikolai Pokhilenko (1), Nikolai Vladykin (2), Zdislav Spetsius (3), Alla Logvinova (1), Stanislav Palessky (1), Olga Khmelnikova (1), and Gleb Shmarov (3)

Sobolev Institute of Geology and Mineralogy SD RAS, Koptyug ave 3, Novosibirsk, Russia (1)Institute of Geochemistry SB RAS, Irkutsk Russia, (2), ALROSA Stock company, Russia (3)

First discovered in Yakutia and the largest in Daldyn region kimberlite pipe is composed from several phases including breccias and porphyric kimberlites. Commonly mantle xenolith from this pipe especially included in the prevailing grey breccia are nearly completely altered. Only relatively fresh material from the brownish – grey breccia from the drilling core and porphyric kimberlites includes material which could be used for the mineral thermobarometry. The picroilmenites from the Zarnitsa pipe are forming three clusters according to the Cr- content: 0.5; 1.0 and 2.5 % Cr2O3 (Ashchepkov,Amshinsky, Pokhilenko, 1980; Amshinsky, Pokhilenko,1984; Alymova et al., 2003) due to the different contamination degree of protokimberlites in mantle peridotites. The ilmenites from porphyric kimberlites are forming stepped trend consisting from three groups of different pressure intervals from 6.5 to 4.0 GPa but more continuous than those determined for the ilmenites from breccia (Ashchepkov et al ., 2010). The relatively low Cr diopsides are corresponding to the deeper part while those containing to 2 -3 of Cr2O3 are from the middle part of the mantle section and are in association with the phlogopites contain the reflecting processes of the protokimbelite differentiation and contamination. Peridotites from the lithosphere base are of Hi temperature type and slightly Fe - enriched and are referred to the porphyroclustic types where garnets contain up to 10% Cr2O3 are they are relatively low in TiO2. But there are alos varieties of reduced Cr and the Fe-enriched which are closer to the deformed type (Agashev et al., 2013). The cold clot in the 60-5.5 GPa (34 mwm-2) are represented by Fe- low peridotites with the garnets of sub-Ca types. The Cr- low and LT eclogites are correspondent to the low 4.5-6.0 GPa interval similar to those from Udachnaya pipe. But near the pyroxenites lens the varieties enriched in Fe and sometimes hybrid pyroxenites appear like in most pf mantle sections in Yakutia. In general the Fe# of the garnets beneath Zarnitsa pipe reveal essential increase which became more pronounced in the uppermost part of the SCLM. the basic cumulates and Phl -Ilm bearing Gar pyroxenites are detected near the Moho boundary. The Gar - Px mantle geotherm in Zarnitsa SCLM is relatively cold. But the heating coinciding with the appearance of Ilm- pyroxenites and basic cumulates in the uppermost part of lithosphere were determined. The trace elements for the mantle peridotites from the common un - enriched type show the peak in Pb, U for both Cpx and garnet probably marking post - subduction origion bu the enriched type reveal HFSE and Sr rise due to metasomatism. 11-05-00060; 11-05-91060-PICS and joint research projects of IGM SB RAS and ALROSA Stock company 77-2, 65-03, 02-05.

Garnets

Spinels

Amphiboles

Ilmenites

Clinopyroxenes

Zarnitsa all tohether Zarnitsa xenolith only

TRE formantle peridotites

0.05 0.10 0.15 0.20 0.25600 800 1000 1200 1400

Fe# Ol in equilibrium with Cpx, Opx, Gar, Chr, Ilm

0.0 4.0 8.0 -6.0 -4.0 -2.0 0.0

SEA

T oCZ arn itsa

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

Diamond

Graphite

1. CaO in Gar2. Al2O 3 in Opx3. Cr2O3 in Cpx4. TiO 2 in Chr5. Cr2O3 in Ilm

8

7

6

5

4

3

2

1

0

P(G

Pa)

8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

0-LogFO 2Variation of

Cpx, Opx, Gar, Chr, Ilm

Xenoliths G arnet PT estim ates (Ashchepkov, 2006)C px (Ashchepkov, 2010)Eclogites (Ashchepkov, 2010)O px (Brey, Kohler,1990-M cG regor, 1974) G ar- O px (Brey, Kohler,1990)

0.05 0.10 0.15 0.20 0.25600 800 1000 1200 1400

Fe# Ol in equilibrium with Cpx, Opx, Gar, Chr, Ilm

0.0 4.0 8.0 -6.0 -4.0 -2.0 0.0

SEA

T oCZ a rn itsa xen o lith s

45 m w/m 2

35 m w /m 2

Sp

Gr

40 m w/m 2

Diamond

Graphite

1. CaO in Gar2. Al2O 3 in Opx3. Cr2O3 in Cpx4. TiO 2 in Chr5. Cr2O3 in Ilm

8

7

6

5

4

3

2

1

0

P(GPa) 8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

0-LogFO 2Variation of

Cpx, Opx, Gar, Chr, Ilm

0.05 0.10 0.15 0.20 0.25600 800 1000 1200 1400

Fe# Ol in equilibrium with Cpx, Opx, Gar, Chr, Ilm

0.0 4.0 8.0 -6.0 -4.0 -2.0 0.0

SEA

T oCN ev id im k a

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

Diamond

Graphite

1. CaO in Gar2. Al2O 3 in Opx3. Cr2O3 in Cpx4. TiO 2 in Chr5. Cr2O3 in Ilm

8

7

6

5

4

3

2

1

0

P(GPa) 8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

0-LogFO 2Variation of

Cpx, Opx, Gar, Chr, Ilm

0.05 0.10 0.15 0.20 0.25600 800 1000 1200 1400

Fe# Ol in equilibrium with Cpx, Opx, Gar, Chr, Ilm

0.0 4.0 8.0 -6.0 -4.0 -2.0 0.0

SEA

T oCM alyu tk a

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

Diamond

Graphite

1. CaO in Gar2. Al2O3 in Opx3. Cr2O3 in Cpx4. TiO 2 in Chr5. Cr2O3 in Ilm

8

7

6

5

4

3

2

1

0

P(GPa) 8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

P(GPa) 8

7

6

5

4

3

2

1

0-LogFO 2Variation of

Cpx, Opx, Gar, Chr, Ilm

0.05 0.10 0.15 0.20

Fe# O l in equilibrium with Cpx, Opx, Gar, Chr, Ilm

600 800 1000 1200 1400 0.0 4.0 8.0

Variation of Cpx, Opx, Gar, Chr, Ilm

-6.0 -4.0 -2.0 0.0

-LogFO 2

SEA

T oC

GraphiteDiamond

D a ln y a y a

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

1. CaO in Gar2. Al2O 3 in Opx3. Cr2O 3 in Cpx4. TiO 2 in Chr5. Cr2O 3 in Ilm

8

7

6

5

4

3

2

1

0

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

0

P(G

Pa)

AOpxG

0.95 0.90 0.85 0.80Mg' Ol in equilibrium

with Cpx, Opx, Gar, Chr, Ilm

0.05 0.10 0.15 0.20

Fe# O l in equilibrium with Cpx, Opx, Gar, Chr, Ilm

600 800 1000 1200 1400 0.0 4.0 8.0

Variation of Cpx, Opx, Gar, Chr, Ilm

-6.0 -4.0 -2.0 0.0

-LogFO 2

SEA

T oC

GraphiteDiamond

F estiv a ln aya

45 m w /m 2

35 m w/m 2

Sp

Gr

40 m w /m 2

1. CaO in Gar2. Al2O 3 in Opx3. Cr2O 3 in Cpx4. TiO 2 in Chr5. Cr2O 3 in Ilm

8

7

6

5

4

3

2

1

0

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

0

P(G

Pa)

AOpxG

0.95 0.90 0.85 0.80Mg' Ol in equilibrium

with Cpx, Opx, Gar, Chr, Ilm

0.05 0.10 0.15 0.20

Fe# Ol in equilibrium with Cpx, Opx, Gar, Chr, Ilm

600 800 1000 1200 1400 0.0 4.0 8.0

Variation of Cpx, Opx, Gar, Chr, Ilm

-6.0 -4.0 -2.0 0.0

-LogFO 2

SEA

T oC

GraphiteDiamond

O sen n ya ya

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

1. CaO in Gar2. Al2O3 in Opx3. Cr2O3 in Cpx4. TiO 2 in Chr5. Cr2O3 in Ilm

8

7

6

5

4

3

2

1

0

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

0

P(G

Pa)

AOpxG

0.95 0.90 0.85 0.80Mg' Ol in equilibrium

with Cpx, Opx, Gar, Chr, Ilm

0.05 0.10 0.15 0.20

Fe# O l in equilibrium with Cpx, Opx, Gar, Chr, Ilm

600 800 1000 1200 1400 0.0 4.0 8.0

Variation of Cpx, Opx, Gar, Chr, Ilm

-6.0 -4.0 -2.0 0.0

-LogFO 2

SEA

T oC

GraphiteDiamond

L etn ya ya

45 m w/m 2

35 m w/m 2

Sp

Gr

40 m w/m 2

1. CaO in G ar2. Al2O3 in Opx3. Cr2O3 in Cpx4. TiO2 in Chr5. Cr2O3 in Ilm

8

7

6

5

4

3

2

1

0

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

0

P(G

Pa)

AOpxG

0.95 0.90 0.85 0.80Mg' Ol in equilibrium

with Cpx, Opx, Gar, Chr, Ilm

Satellites located nearby

Z a rn itsa

40 44 48 52T iO 2 %

0.0

0.4

0.8

1.2 A l2 O 3 %

40 44 48 52T iO 2 %

0.0

1.0

2.0

3.0

4.0C r2 O 3 %

30.0

40.0

50.0

60.0 T i O 2 %

0 4 8 12 16 20M gO %

0 % F e2 O 3

20 % F e2O 3

40 % F e2 O 3

40 44 48 52T iO 2 %

25.0

30.0

35.0

40.0

45.0

50.0F eO %

40 44 48 52T iO 2 %

0.0

0.1

0.2

0.3 N iO %

40 44 48 52T iO 2 %

0.0

0.2

0.4

0.6

0.8V 2 O 5 %

BrecciaPorphyric kimberlitexenoliths

2 4 6FeO %

0

1

2

3

4

5

Cr 2

O3

%

2 4 6FeO %

0

0.2

0.4

0.6

0.8

1

TiO

2 %

2 4 6

2

4

6

Na 2

O %

2 4 6

4

8

12

Al 2

O3

%

8 16MgO %

2

4

6

8

10

Na 2

O %

ConcentrateXenolithsEclogites

0 2 4 6 8 10 12Cr2O3

0

4

8

12

CaO

0 2 4 6 8 10 12 14Cr2O3

0

4

8

12

16

20

FeO

0 2 4 6 8 10 12 14Cr2O3

0

0.4

0.8

1.2

1.6

2

TiO2

0 2 4 6 8 10 12 14Cr2O3

8

12

16

20

24

MgO

0 2 4 6 8 10 12 14Cr2O3

0

0.05

0.1

0.15

0.2

0.25

Na2O

0 2 4 6 8 10 12Cr2O3

0

0.2

0.4

0.6

0.8

NiO

Z a rn itsa

Concentrate brecciaConcentrate porphyric kim berliteXenoliths

Satellites distant Large pipes in Daldyn field

6 8Si (f.u.)

0

0.1

0.2

0.3

0.4

Cr (

f.u.)

6 8Si (f.u.)

0

0.05

0.1

0.15

0.2

0.25

Ti (f

.u.)

6 8

0.01

0.02

0.03

Mn

(f.u.

)

6 8

1

2

3

Al (

f.u.)

1. Sytykan2. Yubileinaya3. Komsom olskaya4. Zarnitsa

6 80.4

0.8

1.2

1.6

2

Ca

(f.u.

)

0.5 0.6K2O%

0.6

0.8

1

1.2

1.4

1.6

1.8

Na

(f.u.

)

6 8FeO %

0.2

0.4

0.6

0.8

K (f

.u.)

6 8Si

1

1.2

1.4

1.6

1.8

2

2.2

K+N

a (f.

u.)

Parg

asite

Parg

asite

hor

blen

de

Hor

blen

de

Ric

hter

ite

Parg

asite

Hor

blen

de

Ric

hter

ite

Parg

asite

hor

blen

de

6 80.2

0.3

0.4

0.5

0.6

Fe (f

.u.)

6 83.2

3.6

4

4.4

4.8

5.2

Mg

(f.u.

)

2 4 6 8FeO %

0

1

2

3

Cr 2

O3

%

2 4 6 8FeO %

0

2

4

6

TiO

2 %

2 4 6 8

16

20

24

28

32

MgO

%

2 4 6 810

12

14

16

Al 2

O3

%

2 4 6 8

0.2

0.4

0.6

0.8

1

Na 2

O %

2 4 6 8FeO %

32

36

40

44

48

SiO

2 %

1. Concentrate2. Peridotite xenoliths

PhlogopitesLa Pr Eu Tb Ho Tm Lu

0.10

1.00

10.00

100.00

1000.00

Sam

ple/

C1

La Pr Eu Tb Ho Tm Lu

0.10

1.00

10.00

100.00

Sam

ple/

C1

Rb Th Nb La Pb Nd Sm Zr Gd Ho Er Lu

0.01

0.10

1.00

10.00

100.00

Sam

ple/

PM

Rb Th Nb La Pb Nd Sm Zr Gd Ho Er Lu

0.01

0.10

1.00

10.00

100.00

1000.00

Sam

ple/

PM

Ce Nd Sm Gd Dy Er Yb

Ce Nd Sm Gd Dy Er Yb

Cs Ba U Ta Ce Pr Sr Hf Eu Dy Y Yb

Cs Ba U Ta Ce Pr Sr Hf Eu Dy Y Yb

A.

Б.

1 . 2 . 3 .4 .

1 . 2 .

Clinopyroxene

Garnets

Ilmenites

Chrom ites

1 .

1 . 2 .3 .4 .5 .

0 20 40 60Cr2O3

0

2

4

6

TiO 2

0 20 40 60Cr2O3

10

20

30

40

50

60

FeO

0 20 40 60Cr2O3

0

20

40

60

Al2O3

0 20 40 60Cr2O3

0

0.2

0.4

0.6

0.8

MnO

0 20 40 60Cr2O3

0

0.05

0.1

0.15

0.2

0.25

0.3

NiO

0 20 40 60Cr2O3

0.1

0.2

0.3

0.4

0.5

0.6

V2O 5

0 20 40 60Cr2O3

4

8

12

16

20

MgO

ConcentrateXenoliths

600 800 1000 1200 1400

600 800 1000 1200 1400

SEA

T oC

GraphiteDiamond

D aln ya ya

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

8

7

6

5

4

3

2

1

0

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

AOpxG

T oC

8

7

6

5

4

3

2

1

P(G

Pa)

Z arn itsa

8

7

6

5

4

3

2

1

P(G

Pa)

600 800 1000 1200 1400

SEA

T oC

GraphiteDiamond

U d a ch n aya

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

1. OpxMc742. Cpx As103. Cpx NT004. Gar As105. Chr As106. Ilm As7. BrKo90

8

7

6

5

4

3

2

1

P(G

Pa)

8

7

6

5

4

3

2

1

P(G

Pa)

600 800 1000 1200 1400

SEA

T oC

S y ty k a n sk a y a

45 m w /m 2

35 m w /m 2

Sp

Gr

40 m w /m 2

Diam ond

Graphite

8

7

6

5

4

3

2

1

0

P(GPa) 8

7

6

5

4

3

2

1AFG

Opx Geotherms