Saturday, May 17, 2014
crystallographic sector zoning is a phenomenon that causes all sorts of headaches for geochemists and petrologists. Basically, as different crystallographic faces grow in a medium (e.g. magma), they have different selectivities for different elements. If you want to measure how much of a particular element a growing crystal scavenges from its surrounding, and you don’t measure all sectors, or don’t know their true relative volume, this can cause errors.
However, at least two scientists have turned this around, and used the zoning as a feature, not a problem. Hinsberg and Schumacher (2007) treat the different sectors as co-existing minerals, calculate D values between them, and note that the D values are temperature dependent. Ta da! They now have a single crystal geothermometer that records T over the growth of the mineral. If life hands you lemons, compare the sections and build a new tool.