Finding peaks in geochemical distributions: A re-examination of the helium-continental crust correlation

Parman [Nature (2007) 446, 900-903] has recently suggested that a correlation exists between peaks in the ocean island basalt (OIB) He-4/He-3 distribution and peaks in crustal zircon ages. This correlation is based on matching peaks seen in smooth kernel density estimates. Kernel density estimation is a very useful technique, but care is required when choosing the smoothing bandwidth as spurious peaks can be produced if the bandwidth is too small. Here I provide an introduction to a general statistical technique for determining whether peaks in density estimates are significant, know as SiZer, focusing on its application to the He-4/He-3 data. SiZer identifies only two statistically significant peaks in the OIB He-4/He-3 distribution, compared with the eight peaks identified by Parman, The helium-continental crust correlation does not seem to be supported by the current data. (C) 2008 Elsevier B.V. All rights reserved.