hsdp drill site
DESCRIPTION
HSDP Drill Site. HSDP - a detailed look at the Hawaiian plume (and CMB?). (Sharp et al., 2004). center. Melting region. edge. Sampling issues: Pt. 1. EPR MORB range. r = 30 km. r = 130 km. MORB. MORB. The isotopic stratigraphy at the base of the mantle is not simple. Sr. He. - PowerPoint PPT PresentationTRANSCRIPT
HSDPDrill Site
HSDP - a detailed look at the Hawaiian plume (and CMB?)
1500
2000
2500
3000
0
500
1000 subaerial
submarine
Mauna Kea subaerial(including alkalic lavas)
Mauna Loa subaerial tholeiite
Mauna Kea subaerial tholeiite
rotary drilled intervals
massive
hyaloclastite
intrusive
depth (mbsl)
ash or soil
first intrusive
first pillow
degassed
undegassedpillow low SiO2, high Na+K
254 m
1079 m
~2230 m
~2440 m
TD September 23, 1999 (3097.7 mbsl)
Lithostratigraphy of HSDP-2 Core
0 100 200 300 400 500 600 700
0
500
1000
1500
2000
2500
3000
HSDP1
HSDP2
Ar-Ar age
Mauna Kea Age
(Sharp et al., 2004)
0
5
10
15
20
25
100 200 300 400 500 600Model Age (ka)
HSDP Mauna Kea(Kurz, 2002)
MORB Range
edge center
20 km
N
Melt Supplymax = 5 cm/yr
0.001
0.1
0.3
0.5
0.7
0.9
1.0
0.05
Present
200 Ka
400 Ka
600 Ka
800 Ka
Kohala
Hualalai
Mauna Loa
Loihi
Kilauea
Mauna Kea
Magma CaptureArea
HSDP
Mahukona
Melting region
Sampling issues: Pt. 1
4
5
6
7
8
9
10
100 200 300 400 500 600
εNd
( )Model Age ka
EPR MORB range
r = 130 km
r = 30 km
5
10
15
20
25
30
100 200 300 400 500 600
Model Age (ka)
0.7026
0.7030
0.7034
0.7038
100 200 300 400 500 600Model Age (ka)
MORB
MORB
2.440
2.445
2.450
2.455
2.460
2.465
2.470
100 200 300 400 500 600
Model Age (ka)
0.126
0.128
0.130
0.132
0.134
0.136
0.138
100 200 300 400 500 600Age (ka)
He-3 anomaly(Pb anomaly?)
Sr anomaly
Core or core-mantling dense layer
Width of melting region 5 10 15 20 25 30 35 40
0.7025 0.7035
0
500
1000
1500
2000
2500
3000
3He/
4He
87Sr/
86Sr
Sr
He
The isotopic stratigraphy at the base of the mantle is not simple
He-3 anomaly(Pb anomaly?)
Sr anomaly
Core or core-mantling dense layer
Width of melting region 5 10 15 20 25 30 35 40
0.7025 0.7035
0
500
1000
1500
2000
2500
3000
3He/
4He
87Sr/
86Sr
Sr
He
The isotopic stratigraphy at the base of the mantle is not simple
Jellinek & Manga (2002)
QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.
186Os data also interpreted as entrained outer core material; correlates w/ 3He
Brandon et al. (1999)
(R. Walker et al. 1997; Brandon et al. 1998; Meibom & Frei 2002)
Re, Os, Pt and core-mantle interaction?Re, Os, Pt and core-mantle interaction?
Observations: high values of 186Os/188Os and 187Os/188Os in Hawaiian lavas, Siberian lavas, and Os-rich alloys
Hypothesis:Entrainment of ~1 wt% outer core material in plume
Depends on:Inner core-outer core partition coefficients for Re, Os, PtInner
core
Outercore
mantle
crust
Re Os Pt
(Brandon et al. 1998; Shen et al.1996; D.Walker 2000)
Re, Os, Pt systematicsRe, Os, Pt systematics
Inner core
Outercore
mantle
crust
Re Os Pt
Re Os Pt
high Re/Os
high Re/Os
high Pt/Oshigh 187Os/188Oshigh 186Os/188Os
high 187Os/188Os
187Re 187Os 190Pt 186Os
outer core = only reservoir with high 187Os/188Os and 186Os/188Os
Std gchems story
0
2
4
6
8
10
0 100 200 300 400 500 600
MK (HSDP2rev)Mauna LoaMK (HSDP 1)Kilauea
εNd
( )Model Age ka
EPR MORB
Anomalous Mauna Loa
0.7032
0.7034
0.7036
0.7038
0.7040
0.7042
0 100 200 300 400 500 600
87Sr/
86Sr
Model Age (ka)
(b)
Mauna Loa data suggest that core of plume islongitudinally heterogeneous
0
2
4
6
8
10
0 100 200 300 400 500 600
MK (HSDP2rev)Mauna LoaMK (HSDP 1)Kilauea
εNd
( )Model Age ka
EPR MORB
Anomalous Mauna Loa
-2
0
2
4
6
8
10
12
1300 1350 1400 1450 1500 1550 1600 1650
εNd
(° )Potential Temperature C
Plume core( < 15 )r km
Fringe of melting region
( = 15 - 60 )r km
MORB
inferred unmelted plume fringe
(?)D''UpperMantle
LowerMantle
Recent deviant lavas from Mauna Loa require longitudinal heterogeneity along the axis of the plume
He-3 anomaly(Pb anomaly?)
Sr anomaly
Core or core-mantling dense layer
Width of melting region
The axial part of the plume is longitudinally heterogeneous;
The inner fringe of the plume is less heterogeneous
The outer fringe is invisible (no melting)
Conclusions
• Different isotopic anomalies are not spatially correlated in the lowermost mantle
• The 3He anomaly is not a general feature of the “lower mantle” but is a feature of the base of the mantle
• Most of the mantle between the plume source and the surface could have R/Ra ≈ 8; however, there are no lavas to represent this entrained material
• The Sr isotope anomaly (87Sr/86Sr ≈ 0.70365) at Hawaii is a broad feature and the isotopic composition could represent a large volume of the lower mantle under Hawaii
• Patterns for Hf, Nd, Os resemble Sr; but 208Pb resembles 3He• Juxtaposing isotopic data with physical models can yield new
perspectives