UTIG RESEARCH PROJECTS ARCHIVE

Principal Investigator: Jay Pulliam

Funding agency: National Science Foundation EAR 0440176
Start Date: September 1, 2004
Expires: August 31, 2006 (Estimated)

The offshore portion of the CVL is comprised, from northwest to southeast, of the islands of Bioko, Principe, Sao Tome, and Pagalu.

Abstract
Volcanic lineaments are a ubiquitous feature of our planet but their role in the mass transfer between mantle and crust and in the plate tectonic framework is still debated. The Cameroon Volcanic Line (CVL) is a 1600-km-long, SW to NE, Y-shaped chain of volcanic centers and plutons that splits into two branches as it reaches the Adamawa Plateau on the Cameroon-Chad border. Roughly half the total length of the CVL lies on the African continent; the other half extends southeastward into the Gulf of Guinea and the Atlantic Ocean. The offshore portion of the CVL is comprised, from northwest to southeast, of the islands of Bioko, Principe, Sao Tome, and Pagalu. The composition of young basaltic lavas is identical in the oceanic and continental portions of the line, indicating similar parental magmas and little contamination from the crustal rocks, yet there is a significant disparity between the ages of earliest volcanism that created the islands of Bioko and Principe and there is a systematic decrease in radiogenic Pb ratios in either direction along the line from the continent-ocean boundary (Halliday et al., 1990). This suggests that an important change in properties and/or processes occurs between the islands of Bioko and Principe. The lack of an obvious age progression in the CVL (Fitton and Dunlop, 1985; Meyers et al., 1998) has led some authors to refer to it as a "hotline" and invoke Rayleigh-Bernard convection in the upper mantle to explain its odd timing, geochemical characteristics and apparently reactivated volcanism (Meyers et al., 1998; King and Anderson, 1998; King and Ritsema, 2000). However, a modified plume model, perhaps one that involves multiple plumes or lateral transport of material along topography on the base of the lithosphere, might also satisfy the constraints (Burke et al., 1971). We will conduct a complementary seismic study offshore to the large-scale, temporary deployment of broadband seismographs scheduled to begin in Cameroon in 2005. Integrating the results of seismic studies on the CVL islands with the results from Cameroon will help distinguish between various models for the genesis of the CVL and its relationship to convection in the mantle.