Magma
chamber timescales
 |
Accessory minerals
such as zircon offer unique insights into the
absolute timing of
crystallization in magmas. Crystal ages
constrain
the longevity of crustal magma chambers with
implications for magma
differentiation processes, the detectability
of stored magma by
geophysical methods, volcanic hazard potential
of volcanoes, and the
geothermal potential of shallow magmatic
intrusions. Current projects
focus on Laacher See, an intra-plate volcano
in the Eifel region
(Germany), Tres Virgenes volcano in Baja
Californa, Juan de Fuca Ridge
dacites (a rare example of oceanic
differentiated lavas), and the
Soufriere volcanic complex of Saint Lucia in
the Lesser Antilles Arc.
Because ion microprobe analysis consumes only small amounts of material, trace elements or isotopic ratios (e.g., oxygen: see below) can also be determined from the same mineral grains used for dating. |
| Zircon (high
birefringence) in a soevite carbonatite
inclusion from Laacher See
(field of view approx. 0.4 mm) |
|
 |
|
| SIMS oxygen
isotope
analysis spots in Laacher See zircons preserve
magmatic, mantle-like
values whereas the carbonate matrix is
overprinted by fluids |
Selected references:
A. K. Schmitt, M. R. Perfit, K. H. Rubin, D. F. Stockli, M. C. Smith, L. A. Cotsonika, G. F. Zellmer, W. I. Ridley, and O. M. Lovera (2011) Rapid cooling rates at an active mid–ocean ridge from zircon thermochronology. Earth and Planetary Science Letters 302, 349‐358
A.K. Schmitt, D.F. Stockli, J.M. Lindsay, R. Robertson, O.M. Lovera, and R. Kislitsyn (2010) Episodic growth and homogenization of plutonic roots in arc volcanoes from combined U–Th and (U–Th)/He zircon dating. Earth and Planetary Science Letters 295 (1–2), 91‐103
A.K. Schmitt, D.F. Stockli, S. Niedermann, O.M. Lovera, and B.P. Hausback (2010) Eruption ages of Las Tres Vírgenes volcano (Baja California): A tale of two helium isotopes. Quaternary Geochronology 5 (5), 503‐511
A.K. Schmitt, F. Wetzel, K.M. Cooper, H. Zou, and G. Wörner (2010) Magmatic Longevity of Laacher See Volcano (Eifel, Germany) Indicated by U‐Th Dating of Intrusive Carbonatites. Journal of Petrology 51, 1053‐1085