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