Hi Joel
Without references to hand I can answer only off the top of my head. There are several things to note.
Although a bit dramatized, the article is not a bad summary of some of the innovations in understanding the genesis of granite that has occurred over the last 20 years. These include the true geometry of many granite plutons, the narrow fractures
through which many are emplaced, the viscosity of magmas during emplacement, and the rate of emplacement.
The results, as the article suggests, contrast with the sluggish viscous emplacement of granite blobs which many people have as their mental image of the formation of these rocks. However we should note that the article says the 1,000 years needed to
emplace a granite pluton 10 km across and 50,000 years to emplace one 50 km across are minimum figures.
The answer to your question about how relevant this is to polonium halos the answers is: not much. The article is about time required for emplacement. "Polonium halos" suggest to some that granite crystallisation times must have been very fast, faster
that the 3 minute half life of Po218, so that this isotope could be trapped in biotite.
Thousand to 50,000 year emplacement times for granites still don't help any YEC interpretation of geology. Selective quotation of this article might be used to give some veneer of academic credibility to a claim like "Of course granites can form
quickly, even the godless geologists admit it!".
Incidentally, there are many problems associated with Gentry's Polonium halo story. These include: the assumption that Precambrian granites are primordial, why Polonium halos are found main in association with uranium mineralisation (including in
deposits other than granites), the possibility that many, if not all, are not formed by Polonium at all. But all this is another story.
respectfully
Jonathan
"R. Joel Duff" wrote:
> Hi,
> I just glanced over this story this morning and was wondering if anyone had any comments on the implications of this theory on the polonium (?) halos so often talked about. Story can be found at: http://www.newsandevents.utoronto.ca/bin1/001206a.asp
>
> Earth's continental land masses created in short, fast bursts
> Findings challenge multi-million year continental crust theory
>
> Joel
>
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