Monogenetic Volcanism: A Window into Mantle Heterogeneity and Magmatic Processes

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• Ninad Bondre (Nature Geoscience, London)
• Tuesday 21 October 2008, 16:30-17:30
• Tilley Lecture Theatre, Department of Earth Sciences.

If you have a question about this talk, please contact Francis Rowland.

Monogenetic volcano-fields – fields containing small, predominantly-basaltic volcanoes – occur either in intraplate settings or in association with larger, polygenetic volcanoes. Recent work has revealed that chemical and isotopic diversity within the products of single monogenetic volcanoes may be the rule, rather than the exception. Such volcanoes form during single, relatively short-lived (months to years) eruptions; compositional variability therefore raises several questions regarding their sources and plumbing systems. Whether the geochemical diversity reflects small-scale heterogeneity in the mantle source and inefficient mixing of small magma batches, or relatively rapid and somewhat erratic differentiation, is yet to be satisfactorily resolved by geochemical studies. Resolving this will likely require tapping into the rich information provided by field relationships and focusing on compositional variations between, as well as within, monogenetic volcanoes. This talk will address key questions pertaining to monogenetic volcanism by considering the Jordan Valley Volcanic Field in southeastern Oregon as an example. The integration of field, geochemical and geochronologic data for this field hints at small-scale mantle heterogeneity and suggests that monogenetic volcanoes may provide important constraints on the evolution and transport of basaltic magma in continental settings.

Key References:

Kogiso, T., M. M. Hirschmann, and P. W. Reiners (2004), Length scales of mantle heterogeneities and their relationship to ocean island basalt geochemistry, Geochim. Cosmochim. Acta., 68, 345-360.

McKenzie D, Stracke A, Blichert-Toft J, Albarede F, Gronvold K, O’Nions R. K (2004), Source enrichment processes responsible for isotopic anomalies in oceanic island basalts, Geochim. Cosmochim. Acta., 68, 2699-2724.

Nature Geoscience editorial (2008), The mantle’s fabric, Nature Geosci., 1(4), p. 205.

Ramos, F. C., and M. R. Reid (2005), Distinguishing between melting of heterogeneous mantle sources from crustal contamination: insights from Sr isotopes at the phenocryst scale, Pisgah Crater, California, J. Petrol., 46, 999-1012.

Strong. M., and J. Wolff (2003), Compositional variations within scoria cones, Geology, 31, 143-146.

This talk is part of the Department of Earth Sciences Seminars (downtown) series.

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