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by VLM
4503 days ago
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Zircons are industrially useful as the primary ore for zirconium metal. If you keep it reasonably cool, like under red hot, it makes a great nuclear fuel rod protective cladding, assuming you refine out the hafnium which does little good in a fuel rod. Its also good for high temp ceramics, although too expensive for your fireplace, probably. If you get the metal red hot and dip it in water it does a fair impersonation of sodium being dumped in water at room temp. Unfortunately, recently, an extremely large demonstration of this effect was performed in Japan with predictable outcome. Anyway there's lots of profit involved, leading to lots of geological research, leading to interesting discoveries. |
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There are cases ("heavy mineral sands") where zircon is used as an ore, but essentially none of the research on zircons has anything to do with this.
Zircons have a number of nice properties:
1) They contain trace amounts of uranium and (initially) no trace amounts of lead. This allows them to be dated through U/Pb dating, which is relatively precise and is still accurate over _very_ long timescales.
2) They can undergo heating to very high temperatures without allowing lead to escape from the crystal lattice, resulting in the date being "reset". This allows dating of the original zircon grain even after the rock hosting it has gone metamorphism.
3) They're very durable physically and chemically. For this reason, they show up in sedimentary rocks and preserve a record of what was being eroded to produce the sedimentary rocks in question. Even when the sedimentary rocks have been changed into metamorphic rocks, the zircons are often preserved.
4) They're not very rare. Zircon isn't "main" rock forming mineral, but it's a not-too-uncommon accessory mineral in many igneous rocks (mostly in felsic magmas). Because zircons are so durable, they show up in sedimentary and metamorphic rocks sourced from the original igneous rock.
All of these reasons is why you'll see a lot of dating of zircons. They're somewhat common, durable, easy to date, and yield accurate results.
This leads to a lot of uses that you might not think of at first.
For example, if you want to know where (geographically) a given sedimentary rock was sourced from (i.e. what was eroded to form it), the most accurate way is to use the "age spectra" of the zircons within it. You basically disaggregate the rock, sort out the zircons (they're very dense), and date every single grain of zircon (and sometimes many zones on every grain). You take the distribution of ages that you get and compare it to the know ages of large igneous bodies that were likely to be exposed and eroding at the time. By matching the distributions (i.e. mixing models, etc), you can get an estimate of where sediment was being sourced from.
This may sound esoteric, but it's very useful for things like oil exploration.