High metal concentrations in fluid inclusions?

I've got a question for any readers with expertise in ore deposits. There's a paper in the Feb. 6 issue of Science (Wilkinson et al; discussion of paper here; warning: paywall) about anomalously high concentrations of metals found in fluid inclusions in ore minerals. I'm curious what you think, and whether the conclusions have practical implications for mineral exploration.

Here are the basics, as far as I understand them. Hot water traveling through rock is responsible for depositing many of the ore deposits that we use for metals. (There are exceptions - iron, for instance.) In previous work, the concentration of metals in the hot water has been estimated from the tiny bits of fluid trapped in quartz or other minerals in ore deposits, but not in the ore minerals themselves. (The quartz has been interpreted as having formed at the same time as the ore minerals, but the study authors argue that it's difficult to be certain.) The concentrations of the metals in those inclusions are fairly low, which means that a lot of water would need to have traveled through the rock in order to form the ore deposits.

This study measured the amount of metals in fluid inclusions in the minerals quartz and sphalerite (zinc sulfide) from two different lead-zinc deposits (one from a Mississippi-Valley-Type deposit in Arkansas, and one from a higher temperature deposit in Ireland). In both cases, the concentration of metals (especially lead) were one to two orders of magnitude higher in the sphalerite. That's a huge difference, and would mean that much smaller amounts of water (and shorter amounts of time) may be necessary to form economic mineral deposits. It also means that the processes that collect and concentrate dissolved metals may be more important in making an ore deposit than the processes that cause them to be precipitated.

But the commentary said that both experiments and theoretical models (I'm not sure which, exactly - thermodynamic models?) predicted lower concentrations than those observed, so I'm curious exactly how big of a problem these observations are for ore geochemistry. (This study dealt with lead-zinc deposits, but the commentary mentioned that other studies had found similar results for copper and gold.) This paper talked about ways that lead and zinc could be concentrated, by evaporation of brines, but I'm not sure what processes might control the concentration of copper or gold in deeper deposits. Does it change the way one might explore, or are the targets the same regardless of whether we understand the source of the fluids or not? (Would understanding this problem make it easier to guess which sites wouldn't have economic concentrations of metals?)

References:

Wilkinson, J.J., Stoffell, B., Wilkinson, C.C., Jeffries, T.E., and Appold, M.S., 2009, Anomalously metal-rich fluids form hydrothermal ore deposits: Science, v. 323, p. 764-767.

Perspective: Bodnar, Robert J., 2009, Heavy metals or punk rocks? Science, v. 323, p. 724-725.