Transcript
Page 1: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

KimberlitesKimberlites: A peep into the Earth’s: A peep into the Earth’sKimberlitesKimberlites: A peep into the Earth s : A peep into the Earth s mantlemantle

Anil KumarAnil KumarAnil KumarAnil Kumar

Isotope Geochemistry GroupIsotope Geochemistry GroupIsotope Geochemistry Group,Isotope Geochemistry Group,National Geophysical Research Institute, National Geophysical Research Institute, 

HyderabadHyderabadHyderabadHyderabad

Page 2: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 3: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 4: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 5: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 6: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 7: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Distribution of kimberlites worldwide

Page 8: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Importance of Kimberlites

They are the only primary sources of diamonds and exotic mantle t i l i th f f d l hi h th t i f timaterial in the form of nodules which are the most informative

messengers from Earth’s mantle

KimberliteKimberlite

Diamond

M tMacrocrysts

Page 9: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Mantle rocks

Peridotite ‐ olivine, denstatite, garnet, and 

clinopyroxene.

Eclogite ‐ garnet g gand clinopyroxene.

Page 10: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 11: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

C conc. in mantle

100 ppm

1000‐3700 ppm

Pyroxene enters the garnetstructure at  high pressure

1000 3700 ppm

A 400‐micron wideferropericlase inclusionferropericlase inclusion

Page 12: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 13: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Utility of kimberlites

• Composition of the deep mantle• Date the deep mantle perturbation eventsp p

Page 14: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Several natural radioisotopes have phalf lives suitable for geochronology

40K 40Ar (and 40Ca) 1 25 GaK Ar (and Ca) 1.25 Ga87Rb 87Sr 48.8 Ga238U 206Pb 4 47 GaU Pb 4.47 Ga235U 207Pb 704 Ma147Sm 143Nd 106 GaSm Nd 106 Ga

Page 15: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

MORB OIBContinental crustContinental crust

Depleted mantle

?

TZ

Undepleted mantle

Page 16: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Cruust 

DM

d /1

44Nd i

Sr /86Sr

i

C

BEBE14

3 N87Crust 

DM

Time Time4.5 Ga 4.5 GaToday Today

Time Time

Page 17: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Narayanpet

DTDelhi

Ti

KoBh

Si16oCB

Ch

WajrakarurBombayHyderabad

Chennai

Calcutta

BuC

BC

SC

DC

La

Ra

14oGSB Z

a

Arabian

Chennai

Trivandrum

WDCEDC

KaCc

100 km ChennaiCG

sea Bay ofBengal

Bangalore

WDC

74o 12o

80oSGT

CG

LamproitesKimberlites

Page 18: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Historically famous diamondsy f

Great Mogul – 900 cts.Koh‐i‐Nor – 793 ctsKoh‐i‐Nor – 793 cts. Nizam – 440 cts. Regent – 410 cts. 

l ffOrloff – 195 cts. Darya‐i‐Noor – 186 cts.Hope – 112 cts.pShah – 95 cts. 

Page 19: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100
Page 20: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

10

6

810

DM

246

Nd

DMCarbonatites

-2

02ε

CHUR

-6-42

60 200 400 600 800 1000 1200

Age in MaAge in Ma

Page 21: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

MORB OIBContinental crust

D l t d tlDepleted mantle

TZ

Undepleted mantle

Page 22: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

16o

Mu:1099+12Ma

Ko:1085+14Ma

NarayanpetCB

DT

Si:1094+ 8MaDelhi

Maj: 1067+ 31Ma

BuC

Ti

KoBh

Si

Mu:1091+56Ma

Si:1097+43Ma

Pipe 1:1091+20Ma 

Pipe 5:1093+20Ma

Ch

Wajrakarur

Pipe 6:1102+23MaPipe 2:1092 +15Ma

BombayHyderabad

Chennai

CalcuttaBC

SC

DC

La

RaPipe 2:1124 +5‐3Ma

Si:1097+43Ma

14o

Pipe 7:1091+10Map

GSB Za

Arabiansea Bay of

Trivandrum

WDCEDC

KaCc

100 km Chennai

SGTCG

y fBengal

Bangalore

Ki b lit74o 12o

80oSGT

LamproitesKimberlites

Page 23: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Present day

EquatorEquator

1100 Ma

Page 24: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Reconstruction at 1100 Ma

Au

In

LaSi

Ka

SF

Co

Am

BaSF

WA

Page 25: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

20

babi

lity 1160 Ma

10R

elat

ive

prob Alkaline

rocks

0400 600 800 1000 1200 1400 1600

Age in Ma

R

Page 26: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Umkondo igneous province1102 – 1112 Ma

Hanson et al. 2004. Science

Page 27: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Warakurna large igneous province Age : 1076 Ma

Page 28: Kimberlites: A peep into the EarthEarths’s mantleWDC EDC Ka Cc 100 km Chennai SGT CG yf Bengal Bangalore Ki b lit 74 o 12 o Lamproites 80 o Kimberlites. Present day Equator 1100

Thank Q


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