Barry L. Weaver

Associate Professor

Ph.D., 1980, Birmingham, England
M.S., 1977, Birmingham, England
B.S., 1976, Durham, England

Trace Element Geochemistry of Igneous and Metamorphic Rocks

The abundances of those elements present in trace amounts in igneous and metamorphic rocks can be used to infer much about their origin and evolution. Trace element abundances in igneous rock suites can be used to quantitatively model the processes which controlled magma compositions prior to emplacement/eruption, and to define the compositional characteristics of the source of the magma. Trace element abundances in metamorphic rocks can be used to identify the nature of the protolith and to model the processes responsible for trace element fractionation during metamorphism.

My research interests include the application of x-ray fluorescence and instrumental neutron activation techniques to the analysis of geological materials, and the interpretation of these data in terms of the origin and evolution of igneous and metamorphic rock suites. On a broader level this research leads to a consideration of trace element models for the composition and growth of the continental crust, and for the evolution of the crust-mantle system.

Much of my research has been directed toward an understanding of the geochemistry and petrogenesis of the various components of Arch�an high-grade (granulite-facies) terrains. The trace element chemistry of the components of high-grade terrains can be used to develop and refine models for the growth and evolution of the continental crust during the early history of the Earth. Of particular interest has been the application of trace element studies to understanding the process(es) by which granulite-facies metamorphism occurs. Also, trace element data can be used to refine models for the types of tectonic processes that operated in the Archan.

Recent research has been more focused on the use of trace element abundances in basaltic rocks as probes of the composition of, and compositional variability within, the Earth�s mantle. The trace element characteristics of basaltic rocks erupted in different tectonic environments vary widely due to major chemical heterogeneity in the mantle. In particular, ocean island basalt (OIB) suites produced by hotspot activity record evidence for both large-and small-scale mantle chemical heterogeneity. The significance of these variations, and the origins of the different mantle sources sampled by OIB magmas, are not fully understood. I have undertaken detailed studies of the geochemistry of the South Atlantic islands of St. Helena and Ascension (funded by NSF). St. Helena volcanic rocks represent one end-member in the global spectrum of OIB compositions, and the origin of the highly unusual chemical characteristics of the mantle source region are of considerable interest. Ascension Island, a near neighbour of St. Helena, is geologically very young and the volcanic rocks are different in composition to those of St. Helena. Moreover, chemical variations within the Ascension volcanic suite are suggestive of contributions from a number of distinct mantle sources.

I am in charge of the analytical laboratories necessary for obtaining the trace element data essential to these studies. The School of Geology and Geophysics has an x-ray laboratory housing both an x-ray diffractometer and an x-ray fluorescence spectrometer, and an instrumental neutron activation analysis laboratory.

External funding for my research, including graduate student support, has been provided by the National Science Foundation.

I teach both undergraduate and graduate course in petrology, geochemistry, and x-ray analytical techniques.

Selected Publications

Collerson, K.D., Campbell, L.M., Weaver, B.L., and Palacz, Z.A., 1991, Evidence for extreme mantle fractionation in Early Arch�an ultramafic rocks from Northern Labrador, Nature, 349, 209-214.

Weaver, B.L. ,1991,The origin of ocean island basalt endmember compositions: Trace element and isotopic constraints, Earth Planet. Sci. Lett., 104, 381-397.

Weaver, B.L., Kar, A., Davidson, J.P., and Colucci, M., 1996, Geochemical characteristics of volcanic rocks from Ascension Island, South Atlantic Ocean, Geothermics ,25, 449-470.

Kar, A., Weaver, B.L., Davidson, J.P., and Colucci, M., In press, Origin of differentiated volcanic and plutonic rocks from Ascension Island, South Atlantic Ocean, Journal of Petrology.

	School of Geology and Geophysics
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Weaver Associate Professor Ph.D., 1980, Birmingham, England M.S., 1977, Birmingham, England B.S., 1976, Durham, England bweaver@ou.edu Trace Element Geochemistry of Igneous and Metamorphic Rocks The abundances of those elements present in trace amounts in igneous and metamorphic rocks can be used to infer much about their origin and evolution. Trace element abundances in igneous rock suites can be used to quantitatively model the processes which controlled magma compositions prior to emplacement/eruption, and to define the compositional characteristics of the source of the magma. Trace element abundances in metamorphic rocks can be used to identify the nature of the protolith and to model the processes responsible for trace element fractionation during metamorphism. My research interests include the application of x-ray fluorescence and instrumental neutron activation techniques to the analysis of geological materials, and the interpretation of these data in terms of the origin and evolution of igneous and metamorphic rock suites. On a broader level this research leads to a consideration of trace element models for the composition and growth of the continental crust, and for the evolution of the crust-mantle system. Much of my research has been directed toward an understanding of the geochemistry and petrogenesis of the various components of Arch�an high-grade (granulite-facies) terrains. The trace element chemistry of the components of high-grade terrains can be used to develop and refine models for the growth and evolution of the continental crust during the early history of the Earth. Of particular interest has been the application of trace element studies to understanding the process(es) by which granulite-facies metamorphism occurs. Also, trace element data can be used to refine models for the types of tectonic processes that operated in the Archan. Recent research has been more focused on the use of trace element abundances in basaltic rocks as probes of the composition of, and compositional variability within, the Earth�s mantle. The trace element characteristics of basaltic rocks erupted in different tectonic environments vary widely due to major chemical heterogeneity in the mantle. In particular, ocean island basalt (OIB) suites produced by hotspot activity record evidence for both large-and small-scale mantle chemical heterogeneity. The significance of these variations, and the origins of the different mantle sources sampled by OIB magmas, are not fully understood. I have undertaken detailed studies of the geochemistry of the South Atlantic islands of St. Helena and Ascension (funded by NSF). St. Helena volcanic rocks represent one end-member in the global spectrum of OIB compositions, and the origin of the highly unusual chemical characteristics of the mantle source region are of considerable interest. Ascension Island, a near neighbour of St. Helena, is geologically very young and the volcanic rocks are different in composition to those of St. Helena. Moreover, chemical variations within the Ascension volcanic suite are suggestive of contributions from a number of distinct mantle sources. I am in charge of the analytical laboratories necessary for obtaining the trace element data essential to these studies. The School of Geology and Geophysics has an x-ray laboratory housing both an x-ray diffractometer and an x-ray fluorescence spectrometer, and an instrumental neutron activation analysis laboratory. External funding for my research, including graduate student support, has been provided by the National Science Foundation. I teach both undergraduate and graduate course in petrology, geochemistry, and x-ray analytical techniques. Selected Publications Collerson, K.D., Campbell, L.M., Weaver, B.L., and Palacz, Z.A., 1991, Evidence for extreme mantle fractionation in Early Arch�an ultramafic rocks from Northern Labrador, Nature, 349, 209-214. Weaver, B.L. ,1991,The origin of ocean island basalt endmember compositions: Trace element and isotopic constraints, Earth Planet. Sci. Lett., 104, 381-397. Weaver, B.L., Kar, A., Davidson, J.P., and Colucci, M., 1996, Geochemical characteristics of volcanic rocks from Ascension Island, South Atlantic Ocean, Geothermics ,25, 449-470. Kar, A., Weaver, B.L., Davidson, J.P., and Colucci, M., In press, Origin of differentiated volcanic and plutonic rocks from Ascension Island, South Atlantic Ocean, Journal of Petrology.