Natural Sciences > Earth, Atmospheric, and Planetary Sciences > Geodynamics Seminar(2001)

Geodynamics Seminar(2001) posted by duggu on 1/31/2008

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Abstract/Syllabus

Courseware/Lectures

Test/Tutorials

Course Highlights

This course features an extensive reading list, as well as an image gallery of the class field trip to Yellowstone.

Course Description

The Earth's crust is primarily composed of melting products from mantle plumes and mid-ocean ridges - both presently and over the course of Earth history. While both systems represent upwelling features in a convective mantle, they can be viewed as end-member systems in that plumes represent buoyant flow whereas mid-ocean ridges represent passive corner flow. This paradigm is not strict - flow beneath ridges may be buoyant in some places, for example, but it does provide a reasonable framework for enquiry.

Plumes and ridges can be studied independently, but in many places across the globe the systems interact, often in intriguing fashion. The nature of these interactions provides an opportunity to improve our understanding of both systems, and provides new perspectives on the mantle, crustal, and water column processes associated converting heat from the Earth's interior into new crust, hydrothermal flow, and biological communities on the seafloor.

Special Features

Image gallery

Syllabus

Plume Ridge Interactions

The approach taken for the 2001 Plume-Ridge Interactions Seminar series was to start with basic ideas about mantle convection and tectonics, and an overview of the global hotspot and ridge systems. We then addressed three case studies of plume-ridge interactions in detail. Our first case was the interaction of the Iceland plume - one of the largest plumes in the world - with the Northern Mid-Atlantic Ridge. We then turned to the interaction of the Galapagos plume with the Galapagos Spreading Center, and finished with the interaction of the Cobb Plume with the Juan de Fuca Ridge. Each of these systems provides a different perspective on the nature of plume-ridge interactions, and by comparison and contrast we are able to distill the fundamental aspects out of the complex array of geophysical and geochemical data associated with plume-ridge systems.

Grading

Joint Program students enrolled in the Geodynamics seminar are required to complete a project for the class. This includes research, an oral presentation during the last two or three seminar meetings, and a written paper due at the end of the semester. For first and second year students, the project must be on a topic related to the theme of the seminar and must be different from their main research interest. For more advanced students, the topic may be closely related to their dissertation research.

Course Outline

Course outline.
SECTIONs	TOPICS
Background on Tectonics and Mantle Convection	How do plumes and ridges fit into ideas regarding mantle convection? What is a plume, how are they distributed around the globe? How do the properties of plumes and ridges vary? What would be a canonical model for the chronology of a p/r interaction? What are the burning, unanswered questions regarding plumes, ridges, and p/r interactions? What kinds of data and modeling are needed to answer the important questions?
Case Study 1: Iceland/Northern MAR - Stuck in the Middle?	What is the pattern of mantle flow beneath Iceland? How big is the Iceland plume? Where is it? How far downrift can the chemical and mechanical influence of the Iceland plume be traced? How and where is the plume fragmented and distributed to discrete volcanic systems? What is the role of the Iceland plume in the early stages of rifting on the northern MAR? What do the V-shaped ridges tell us about the p/r interaction and its influence on parameters such as lithospheric strength and upper mantle flow?
Case Study 2: Galapagos/GSC - Gone but Not Forgotten	How has the interaction between the Galapagos plume and the Galapagos Spreading Center evolved over time? How does lava chemistry vary along the GSC and what does this imply regarding the p/r interaction? What is the present pattern of mantle flow beneath this system? What does the mantle matrix do between the two upwelling features? Is there still a melt connection? How big is the Galapagos plume? Where is it?
Case Study 3: Cobb/JdFR - The First Days are the Hardest Days	Is the Cobb hotspot a plume? How has it behaved in the hot-spot reference frame? Does it have a geochemical signature? Where is it presently located? How deep is it rooted? What is the pattern of mantle flow beneath this system? When did the JdFR start bending towards the Cobb hotspot? How is melt distributed beneath the central JdFR? How does lava chemistry vary along the JdFR/Cobb region? What patterns of matrix and melt flow are consistent with the observational and theoretical constraints? How might long-term observatories, such as NeMO and Neptune contribute to our understanding of the p/r interaction?
Esoterica	How do ridges, plumes, and p/r interactions influence the global biogeography of chemosynthetic systems? How do the myriad millions of near-ridge seamounts relate to p/r interactions? How fixed is the hot spot reference frame? Can large plumes create new plate boundaries? How deep is the source region for hotspots?

Calendar

Each seminar features an invited speaker followed by a discussion moderated by a WHOI scientist. Moderators are encouraged to present synoptic material of their own relevant research.

Course calendar.
SES #	SPEAKER(S)	TOPICS
1	Dr. Neil Ribe /Dr. Peter Kelemen	Scenes in the Life of a Mantle Plume
2	Dr. Bill White / Dr. Mark Kurz	Origin and Evolution of the Galapagos Plateau
3	Dr. Guust Nolet / Dr. Aibing Li	Seismic Tomography of the Iceland Plume
4	Dr. Jean Guy Schilling / Dr. Stan Hart	Basic Geochemical Aspects of Plume - Ridge Interactions
5	Dr. Doug Wilson / Dr. Pablo Canales	Plate Motions and Spreading Ridge Evolution Near the Galapagos Hotspot
6	Dr. David Bercovici / Dr. Greg Hirth	Dynamics of Plumes and Hotspots
7	Dr. Garrett Ito / Dr. Jian Lin	Evolution and Dynamics of the Iceland Hotspot in the North Atlantic
8	Dr. Peter Kelemen / Dr. Ken Sims	Mantle Heterogeneity in the North Atlantic
9	Dr. Bill Menke / Dr. Rob Sohn	Magmatic Structure of Axial Volcano, Juan de Fuca Ridge
10	Dr. Yang Shen / Dr. Bob Detrick	Iceland Plume: Blowing in the Wind?
11	Dr. Mike Perfit / Dr. Ken Sims	Insights into Ridge-Hotspot Interaction on the Juan de Fuca Ridge: Geochemical Investigations of Axial Seamount and Adjacent Rift Zones
12	Dr. Dennis Geist / Dr. Henry Dick	Plumes at Plate Boundaries (When Bad Things Happen to Good Plumes)
13	Dr. Katrina Edwards / Dr. Susan Humphris	Chemolithoautotrophic Extremophiles and Biogeography of Vent Biota
14	Dr. Jason Phipps-Morgan / Dr. Jack Whitehead	Origination Depth of Mantle Plumes
		Field Trip to Yellowstone

Readings

Ribe, N., U. Christensen, and J. Theissing. "The dynamics of plume-ridge interaction, 1: Ridge-centered plumes." Earth Planet Sci Lett 134 (1995): 155-168.

Ito, G., Y. Shen, G. Hirth, and C. Wolfe. "Mantle flow, melting and dehydration of the Iceland mantle plume." Earth Planet Sci Lett 165 (1999): 81-96.

White, W. M., A. R. McBirney, and R. A. Duncan. "Petrology and Geochemistry of the Galapagos: Portrait of a Pathological Mantle Plume." J Geophys Res 93 (1993): 19533-19563.

Richards, M. A., and R. W. Griffiths. "Thermal entrainment by deflected mantle plumes." Nature 342 (1989): 900-902.

Schilling, J. G. "Upper mantle Heterogeneities and dynamics." Nature 314 (1985): 62-67.

———. "Fluxes and excess temperatures of the mantle plumes inferred from their interaction with migrating mid-ocean ridges." Nature 352 (1991): 397-403.

Wilson, D. S., and R. N. Hey. "History of rift propagation and magnetization intensity for the Cocos-Nazca spreading center." J Geophys Res 100 (1995): 10,041-10,056.

Sinton, J. M., D. S. Wilson, D. M. Christie, R. N. Hey, and J. R. Delaney. "Petrologic consequences of rift propagation on oceanic spreading ridges." Earth Planet Sci Lett 62 (1983): 193-207.

Hieronymus, C. F., and D. Bercovici. "Discrete alternating hotspot islands formed by the interaction of magma transport and lithospheric flexure." Nature 397 (1999): 604-607.

———. "Non-hotspot formation of volcanic chains: control of tectonic and flexural stresses on magma transport." Earth Planet Sci Lett 181 (2000): 539-554.

Albers, M., and U. R. Christensen. "Channeling of plume flow beneath mid-ocean ridges." Earth Planet Sci Lett 187 (2001): 207-220.

Ito, G. "Reykjanes 'V'-shaped ridges originating from a pulsing and dehydrating mantle plume." Nature 411 (2001): 681-684.

Korenaga, J., and P. B. Kelemen. "Major element heterogeneity in the mantle source of the North Atlantic igneous province." Earth Planet Sci Lett 184 (2000): 251-268.

Gudmundsson, O., B. Brandsdottir, W. Menke, and H. Olafsson. "The magma chamber of Katla volcano in the propagating volcanic zone of south Iceland revealed by seismic undershooting." Geophys J Int 119 (1994): 227-296.

Fox, C. G. "In situ ground deformation measurements from the summit of Axial Volcano during the 1998 volcanic episode." Geophys Res Lett 26 (1999): 3437-3440.

Embley, R. W., W. W. Chadwick Jr., M. R. Perfit, M. C. Smith, and J. R. Delaney. "Recent eruptions on the CoAxial segment of the Juan de Fuca Ridge: Implications for mid-ocean ridge accretion processe.s" J Geophys Res 105 (2000): 16501-16525.

Steingerger, B., and R. J. O'Connell. "Effects of mantle flow on hotspot motion." In The History and Dynamics of Global Plate Motions. Edited by M. A. Richards, R. G. Gordon, and R. D. van der Hilst. Washington, D.C: AGU Monograph Series, 2000, pp. 377-398. ISBN: 0875909795.

Shen, Y., et al. "Seismic evidence for a lower mantle origin of the Iceland plume." Nature 395 (1998): 62-65.

Rhodes, J. M., C. Morgan, and R. A. Liias. "Geochemistry of Axial Seamount lavas: Magmatic relationship between the Cobb hotspot and the Juan de Fuca Ridge." J Geophys Res 95 (1990): 12,713-12,733.

Desonie, D. L., and R. A. Duncan. "The Cobb-Eickelberg seamount chain: Hotspot volcanism with mid-ocean ridge basalt affinity." J Geophys Res 95 (1990): 12,697-12,711.

Geist, D., T. Naumann, and P. Larson. "Evolution of Galapagos Magmas: Mantle and Crustal Fractionation without Assimilation." J. Petrology 39 (1998): 953-971.

Geist, D., and M. Richards. "Origin of the Columbia Plateau and Snake River Plain: Deflection of the Yellowstone plume." Geology 21(1993): 789-792.

Naumann, T. R., and D. J. Geist. "Generation of alkalic basalt by crystal fractionation of tholeiitic magma." Geology 27 (1999): 423-426.

McCollom, T. M. "Geochemical constraints on primary productivity in submarine hydrothermal vent plumes." Deep-Sea Research 47 (2000): 85-101.

Tunnicliffe, V., and C. M. R. Fowler. "Influence of sea-floor spreading on the global hydrothermal vent fauna." Nature 379 (1996): 531-533.

Morgan, Phipps, et al. "Observational hints for a plume-fed sub-oceanic asthneosphere and its role in mantle convection." Journal of Geophys. Res. 100 (1995): 12753-12768.

Morgan, Phipps, J., and W. J. Morgan. "Two-stage melting and the geochemical evolution of the mantle: a recipe for mantle plum-pudding." Earth Planet Sci Lett170 (1999): 215-239.