Understanding 40Ar:39Ar age systematics along seamounts trails
Channel: Paul Wessel
Date: 2020-02-05

Dr. Anthony Koppers (Oregon State University) gave a guest lecture via Skype in Fall 2008 for a graduate class on Advanced Plate Tectonics in SOEST, University of Hawaii at Manoa.  The students recorded the lecture and produced video podcasts of the event.  This is one of 8 such lectures from the course which was taught by Prof. Paul Wessel.

ABSTRACT:

"The current discussions on the nature of hotspot volcanism, the validity of the mantle plume model, the possible motion of plume conduits, the relation of seamount trails to large igneous provinces, and the shape/form of these plumes, all hinge on a detailed understanding of the geochronology of seamount trails. However, unlocking the age systematics of seamounts themselves, and the seamount trails they are part of, is not a trivial exercise. Despite the fact that these age data are most crucial in the ongoing scientific discussions, often referred to as the "mantle plume debate", we have a very limited age database and many of the earlier age determinations are at a minimum suspect (because of unresolved issues with hydrothermal and seawater alteration). In this seminar of today I will layout three case studies on the Samoan, Louisville, Gilbert Ridge and Tokelau seamount trails with an emphasis on what the 40Ar/39Ar age data tell us about the hotspot hypothesis and related questions. All seamount trails discussed show a consistent younging from their "expected" older to younger end. However, not all age progressions are linear and consistent between seamount trails! In some cases, the classical hotspot model only needs to be "adjusted" to include plume motions (e.g. Hawaii and Louisville). In other cases, including plume motions is not sufficient (e.g. Gilbert Ridge and Tokelau) requiring the possibility of secondary processes (e.g. plate extension, stress-induced volcanism, overprinting). In yet other cases, a hybrid model is required (e.g. Samoa) with mantle plume volcanism first, followed by extensional volcanism later on. A one-model-fits-all approach thus seems improbable and undesirable for settling the "plume debate" at this point!"