The Early Izu-Bonin-Mariana Arc

Mark ReaganUniversity of Iowa

Osamu IshizukaGeological Survey of Japan/AIST

Barry Hanan, Rosemary Hickey-Vargas, Matthew Heizler, Sherman Bloomer, Patricia

Fryer, Jim Hawkins, Teruaki Ishii, Katie Kelley, Jun-Ichi Kimura, Yasuhiko Ohara,

Robert Stern, Melinda Woods

West Philippine Basin Parece

Vela Basin

OgasawaraEscarp. ‘04 Shinkai dives

SaipanRota Guam‘06 Shinkai dives

ChichijimaHahajima

Kyu

shu-

Pala

u R

idge

Philippine Plate

PacificPlateIz

u ar

cAmamiPlateauca. 116 Ma

DSDP458,459

Mar

iana

Tro

ugh

Wes

t Mar

iana

Rid

ge

Mar

iana

arc

Vol

cano

, Bon

in a

rcs

ODP 782,786Shinkai divesShikoku

Basin

DSDP447,448

0102030405060

Protoarc Modern arcSecond arc

Timeline for IBM forearc sites

Age in Ma

Back-arcspreading

West Philippine BasinParece Vela Basin

Mariana Trough

First arc

Arc minima?

Arc volcanism

458,

Chi

.S

aipa

n, C

hi.

Oga

s, H

ahaj

Gua

m

Rot

a

448

Gua

m

(Best 40Ar/39Ar and K/Ar age dates)

Sources: Meijer et al. (1983); Taylor (1992); Lee et al. (1995); Gill et al. (1994); Cosca et al. (1998); Pearce et al. (1999); Deschamps and Lallemand (2002); Straub et al. (2003); Ishizuka et al. (2006); This study

S.M

ar. f

orea

rc

Pre-arc

Saipan

Rota

Guam

973

974

975

976977

On-land and dive locations - Marianas

Shinkai 6500 dives8/27/06-9/5/06

975974976

Guam

??

1st and 2nd arc: v,iTransitional boninites: v,i

MORB-like basalts: v,i

Boninites: vAdakitic andesites: v,i

Topography of Mariana forearc(from GeoMapApp)

5:1 vertical exaggeration

Peridotites, gabbros

Trenchsoutheast

Basalt Boninite RhyoliteLocation Dive 975 Dive 974 GuamDive 826 Saipan

(45.1 Ma)SiO2 50.28 56.74 54.64 56.21 77.29TiO2 1.10 0.17 0.57 0.33 0.10

Al2O3 17.34 10.66 15.66 15.88 12.62

Fe2O3* 9.41 8.75 9.10 9.75 1.54

MgO 5.55 15.04 6.17 6.56 0.03CaO 13.25 5.54 10.87 9.06 0.97Na2O 2.60 2.01 2.23 2.06 4.30K2O 0.22 0.82 0.51 0.58 2.55

Representative “Protoarc” compositions

0.1

1

10

100

Cs Rb K Ba Sr Pb Th U Nb Ta La Ce Pr Nd Zr Hf Sm Eu Gd Ti Tb Dy Ho Er Tm Yb Lu Y

site 458 glass

NMORB

Mariana trench slope

Bonin trench slopeDebari et al. (1999)

PM N

orm

aliz

ed C

once

ntra

tion

s

LREE HREEMREE

mostly wedge?mostly slab

Forearc basalts - FAB

(Ti/V =15-21)

0.1

1

10

100

Cs Rb K Ba Sr Pb Th U Nb Ta La Ce Pr Nd Zr Hf Sm Eu Gd Ti Tb Dy Ho Er Tm Yb Lu Y

LAICPMS incompatible trace element concentrations for consanguineous (?) DSDP site 458 glasses

PM N

orm

aliz

ed C

once

ntra

tion

s

Boninite Tholeiite

NMORB

0.10

1.00

10.00

100.00

Cs Rb K Ba Sr Pb Th U Nb Ta La Ce Pr Nd Zr Hf Sm Eu Gd Ti Tb Dy Ho Er Tm Yb Lu Y

site458 (glass)

Mariana trench slope(whole rock)

Bonin IslandsChichijima (glass)PM

Nor

mal

ized

Con

cent

rati

ons

48-49 Ma boninites

Melting: harzburgite, shallow, strong slab flux

0

1

10

100

Cs Rb K Ba Sr Pb Th U Nb Ta La Ce Pr Nd Zr Hf Sm Eu Gd Ti Tb Dy Ho Er Tm Yb Lu Y

PM N

orm

aliz

ed C

once

ntra

tion

sTransitional Boninites

44 Ma - Guam

Ba/La = 13.7

Ba/La = 2843 Ma - Ogasawara

Basalt Andesite RhyoliteLocation Guam Rota GuamSiO2 51.80 50.17 60.61 72.80TiO2 0.36 0.55 0.54 0.29Al2O3 16.83 18.06 17.58 14.16Fe2O3

*9.18 8.55 7.24 3.07

MgO 9.81 9.09 2.19 0.96CaO 10.85 11.57 7.60 3.88Na2O 1.64 1.78 3.15 3.68K2O 0.12 0.18 0.76 0.97

Representative Mariana arc lava compositions

"First arc"

0.10

1.00

10.00

100.00

Cs Rb K Ba Sr Pb Th U Nb Ta La Ce Pr Nd Zr Hf Sm Eu Gd Ti Tb Dy Ho Er Yb Lu

0.10

1.00

10.00

100.00

Cs Rb K Ba Sr Pb Th U Nb Ta La Ce Pr Nd Zr Hf Sm Eu Gd Ti Tb Dy Ho Er Yb Lu

31 Ma Mariana trench slope

"First Arc" lavas PM

Nor

mal

ized

Con

cent

rati

ons

42 Ma Guam

ca. 36 Ma Rota, Saipan

30 Ma Bonin TurbiditesGill et al. (1994)

32

34

36

38

40

42

44

46

48

50

South NorthGuam

Mar. Trn.SaipanRota

DSDP458-9

Haha-jima

Chichi-jima

Ogasa.Ridge

ODP786

Adakitic forearc lavas

Boninites

Rhyolites

Transitional boninites

44

41

42.7

45.1

38.3

36

46.7-45.348.2-46.0

44.7

42.9 41.843.944

>47

MORB-like (FAB)

Agein

Ma

Ages and compositions of protoarc and first arc lavas

Ages from this study; Ishizuka et al. (2006); Cosca et al. (1998); Meijer et al. (1983)

49.3

32

?

“Normal” arc lavas

??

?

After Ishizuka et al. (2006)

31?

0

50

100

150

200

250

300

350

K/Ba

0

2

4

6

8

10

12

14

La/Nb

0

5

10

15

20

30 35 40 45 50

Age in 106 years

Rb/La

Mesozoic volcanogenic sed.

Silicic sedimentMORB

Arc

MORBOIB

Total slab flux+melting

-10

-5

0

5

10

15

20

25

30

-10 -5 0 5 10 15

Ndo

Hfo

OIB+Pacific volcanogenic sediment

Silicic sediment

Indian Ocean MORB-OIB+Philippine basins

Pacific MORB

Sources: GEOROC; PETDB; Woodhead et al. (2001); Pearce et al. (1999), this study

458, 459, first arc

Guam

Second arc, modern arc

Chichijima

782,786

37.5

38.0

38.5

39.0

39.5

17.5 18.0 18.5 19.0 19.5 20.0

206Pb/204Pb

208

Pb/

204

Pb Philippine basins

Jurassic volcaniclastic sediment

Average Asian loess

Cenozoic silicic sediments

NHRLIP

Sources: Meijer (1976); Hickey-Vargas and Reagan (1987); Hickey-Vargas (1989); Dobson and Tilton (1989); Taylor et al. (1994); Elliott et al. (1997); Hickey-Vargas (1998); Taylor and Nesbitt (1998); Pearce et al. (1999); Debari et al. (1999); Pettke et al. (2000); Sun and Stern, (2001); Woodhead et al. (2001); Ishizuka et al. (2006), this study

MarianaFAB

BoninFAB

Mariana boninitic

Bonin boniniticMariana first arc

Mariana fore-arc andesites

Indian-like mantle Pacific mantle

SW NE

Transition

West Philippine BasinPacific Plate (?)

Protoarc 49-43 Ma(youngest oldest, 1-d spreading?)

Before 50 Ma

See Stern and Bloomer (1992), Hall et al. (2003)

FABBoniniteTrans. boninites

First arc 42-32 Ma

Transition 45-42 Ma

Conclusions:

• Volcanic stratigraphy of IBM forearc largely supports Stern and

Bloomer model of catastrophic subduction initiation and forearc

spreading

• Oldest subduction related magmas may be FAB

• Subduction initiation occurred at or near Pacific-Indian mantle

domain boundary

• Late Eocene volcanics record a shift to “normal” arc magma

generation processes and therefore “normal” mantle convection 4-7

million years after subduction initiation

• IB & M arcs have similar histories before opening of PVS basins

• Not much evidence for loss of forearc area by subduction erosion