Cool and Hot!

Oh this is going to be be interesting! BBC is reporting that a few years back, geothermal energy drillers in Hawaii unexpectedly drilled through into a chamber of dacitic magma. The magma rushed 5 to 10 meters up the shaft before cooling effects of the drilling fluid solidified it. As a result, they now have samples of undegassed, unaltered, quenched magma.

I think you'd need a fair background in geology to understand how important this is, but simplifying, Hawaii is composed of a first generation melt from the mantle, similar to ocean crust- both are dominantly one flavor or another of basalt. To get something like the composition of continental crust, you either need to remove (by fractional crystalization) 95+ percent of the original basalt, leaving the lowest melting temperature fraction behind, or you need to remelt the material one or more times. The latter has the same effect as the former: segregating the materials with the lowest melting temps from those with the highest.

Dacite is much more like continental rock than it is like basalt.

Further, as noted above, the material still has its initial volatile composition (gases such as carbon dioxide, sulfur dioxide or hydrogen sulfide, and water). While it may have been contaminated by the drilling fluids, we know exactly what the composition of those fluids are: we can subtract that contaminant out. We also know where the magma chamber is; we can sample various spots to see how composition varies from one place to another.

I expect the geoblogosphere will be all over this in the next few days, but only a fellow geo-nerd can really understand how interesting this is.