HR: 1340h
AN: U13A-0869    [Abstracts]
TI: Constraining Absolute Plate Motion by 40Ar/39Ar Age Dating and Geochemical Fingerprinting of Linear Volcanic Chains
AU: * Koppers, A A
EM: akoppers@coas.oregonstate.edu
AF: College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis, OR 97331- 5503, United States
AU: Staudigel, H
EM: hstaudigel@ucsd.edu
AF: Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093- 0225, United States
AU: Konter, J
EM: jkonter@projects.sdsu.edu
AF: Department of Geological Sciences, San Diego State University, San Diego, CA 92182, United States
AB: Determination of reliable Absolute Plate Motion (APM) models remains a major frontier in global tectonics and geodynamics. However, APM models have been constructed with mixed success in the past, based on the geometry of linear volcanic chains and assuming a mantle reference frame of "fixed" hotspots. These reconstructions have been negatively impacted by the facts that the number of continuous volcanic chains decreases significantly back through geological time, become discontinuous and cannot be associated with active or zero-aged volcanoes. In reality, most APM models start to deteriorate for plate motion stages older than 40 Ma and become largely unconstrained prior to 70 Ma. In addition, the few seamount trails that were studied in detail often show disturbed age progressions, indicating that their volcanic evolutions were affected by processes other than hotspot volcanism or that their mantle plumes were not fixed in the Earth's mantle. Recent age data shows that the volcanoes themselves require build-up times of several millions of years, adding yet another complication in the reconstruction of APM models. The above difficulties show that the relationships between the morphology of linear volcanic chains, their age systematics and absolute plate motions are more complex than originally envisioned by Morgan in 1971. However, there are a series of observations and recent developments that make us confident that linear volcanic chains remain attractive targets for detailed geochronological and geochemical investigations that will help us to improve APM models. In fact, they may re-establish the basic assumption of an absolute reference frame with respect to which we can determine past plate motions, in particular, for periods older than 70 Ma. Recent denser sampling of seamounts has shown that some seamount chains retain very distinct geochemical fingerprints over tens of millions of years. Good examples are the EM2-type Samoan shield building lavas and the HIMU-type hotspots that formed the Cook-Austral chain. The latter hotspots can be extended into the Tertiary seamounts of the Gilbert Ridge and Tokelau Seamounts, and even the West Pacific Seamount Province which includes HIMU-type seamounts as old as 120 Ma. Correlating geochemistry with geochronology thus allows us to join segments of seamount trails that otherwise could not be connected, when based on their morphologies and ages alone. In turn, we have found an effective tool that we can apply in deciphering the history of intra-plate volcanism in the oceans, allowing us to reconstruct longer portions of their APM histories, up to at least 120 Ma.
DE: 1033 Intra-plate processes (3615, 8415)
DE: 1115 Radioisotope geochronology
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8157 Plate motions: past (3040)
DE: 8415 Intra-plate processes (1033, 3615)
SC: Union [U]
MN: 2007 Fall Meeting