[email protected]@utah.edu Detection of present-day slab-driven mantle flow...
19
[email protected] http://web.utah.edu/t Detection of present-day slab-driven mantle flow Michael S. Thorne Edward J. Garnero Allen K. McNamara Heiner Igel Dept. of Geology & Geophysics, University of Utah School of Earth and Space Exploration, Arizona State University Dept. of Earth & Environmental Sciences, Ludwig Maximilians University
-
date post
15-Jan-2016 -
Category
Documents
-
view
219 -
download
0
Transcript of [email protected]@utah.edu Detection of present-day slab-driven mantle flow...
[email protected] http://web.utah.edu/thorne
Detection of present-day slab-driven mantle flow
Michael S. ThorneEdward J. GarneroAllen K. McNamara
Heiner Igel
Dept. of Geology & Geophysics, University of UtahSchool of Earth and Space Exploration, Arizona State University
Dept. of Earth & Environmental Sciences, Ludwig Maximilians University
[email protected] http://web.utah.edu/thorne
Past Ultra-low velocity zone detections
McNamara et al. 2010
[email protected] http://web.utah.edu/thorne
PSVaxi Model Space
δVS, δVP:(-15%,-5%) (-30%,-10%)(-45%,-15%) (-5%,-5%)(-10%,-10%) (-15%,-15%)
δρ: 0%, +10%
h: 5, 7.5, 10, 12.5, 15, 20, 30 km
width: 1.5°, 3.0°, 4.5°, 6.0°, 12.0°
edge: 8.5° - 19.0° in 1.5° increments
total: 580 models
[email protected] http://web.utah.edu/thorne
Type A&B waveforms & ULVZ position
NORMAL
ULVZ Model:δVS = -45%δVP = -15%δρ = +10%h = 12.5 kmwidth = 3.0°
[email protected] http://web.utah.edu/thorne
Type A&B waveforms & ULVZ position
Type A
ULVZ Model:δVS = -45%δVP = -15%δρ = +10%h = 12.5 kmwidth = 3.0°
[email protected] http://web.utah.edu/thorne
Type A&B waveforms & ULVZ position
ULVZ Model:δVS = -45%δVP = -15%δρ = +10%h = 12.5 kmwidth = 3.0°
Type B
[email protected] http://web.utah.edu/thorne
Type A&B waveforms & ULVZ position
ULVZ Model:δVS = -45%δVP = -15%δρ = +10%h = 12.5 kmwidth = 3.0°
Type B
[email protected] http://web.utah.edu/thorne
Results: Normal, Type A & B locations
Tomo: Grand, 2002
[email protected] http://web.utah.edu/thorne
δVS = -45%, δVP = -15%δρ = 10% thickness =10-15 km width ≈ 200-300 km
length ≈ 800 km
Results: Mega-sizedULVZ
[email protected] http://web.utah.edu/thorne
Thermochemical convection modeling
• 3 distinct compositional reservoirsi. background mantleii. LLSVPiii. ULVZ
• ULVZs preferentially align along LLSVP boundaries
• ULVZs fast moving, merging ULVZs realign with LLSVPboundaries on hundred million year time scales.
McNamara et al. 2010
[email protected] http://web.utah.edu/thorne
Conclusions
• SPdKS capable of high resolution mapping of ULVZ position and properties.
• IF LLSVP’s are thermochemical piles…
a) mega-sized ULVZ in LLSVP hole may be indicative of multiple merging piles.
b) may give rise to mantle plumes rising near interior edges of piles.
c) indeed, mega-sized ULVZ lies directly beneath the Samoa hot spot.
