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Contrib Mineral Petrol (2014) 168:1057
DOI 10.1007/s00410-014-1057-8
ORIGINAL PAPER
Submicronscale traceelement distributions in natural zircons of known provenance: implications for Tiinzircon thermometry
Amy E. Hofmann Michael B. Baker John M. Eiler
Abstract NanoSIMS measurements of Ti, P, Y, Ce, and Hf in zircon separates from the Youngest Toba Tuff, the Bishop Tuff, the Quottoon Igneous Complex, the Sierra Nevada batholith, and an Adirondack migmatite show that micron-scale oscillatory zoning of Ti is common. The zircons we have studied typically display banded concentration gradients, having between 1 and 7 peaks in Ti abundance over length scales of 1020 mthe beam diameter commonly used for SIMS trace-element zircon analyses with amplitudes of up to 4.5 ppm Ti (baseline values are ~14 ppm) and widths (measured at half-height) of between ~0.2 and 4 m. Spatial correlations between concentrations of Ti and other trace elements (P, Y, and Ce) are also common, but variable in character, ranging from oscillatory co-variation of Ti, P, Y, and Ce to cases where only a subset of peaks for a given element is spatially correlated with peaks in Ti. There are also longer length-scale, generally positive correlations among concentrations of Ti, P, Y, and Ce (i.e., gradients on which narrower peaks are superimposed). In contrast, Hf concentrations are either uncorrelated or inversely correlated with these longer length-scale
Communicated by T. L. Grove.
Electronic supplementary material The online version of this article (doi:http://dx.doi.org/10.1007/s00410-014-1057-8
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A. E. Hofmann (*) M. B. Baker J. M. Eiler
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA e-mail: [email protected]
Present Address: A. E. Hofmann
Department of Chemistry, Franklin & Marshall College, Lancaster, PA 17604, USA
Received: 2 November 2013 / Accepted: 18 August 2014 / Published online: 3 September 2014 Springer-Verlag Berlin Heidelberg 2014
variations in Ti concentrations. The wide range in Ti concentrations over distances of less than 1 m and the various correlations between Ti concentrations and those of the other analyzed elements suggest that on the micron scale and at temperatures between ~700 and 800 C, zircon-liquid Ti partitioning is not controlled by bulk or lattice equilibrium. Treating our NanoSIMS Ti ion maps as though they were conventional...