Silver is Golden ... or Gold has Lost its Luster (for today)

The last 2 days have been pretty good to silver's ETF (SLV) and pretty ordinary for gold ETF (GLD).  

Gold and silver, often joined at the hip, have disconnected from a price perspective ... and there's some interesting trading at the center of it.  Overall, silver is showing gold who's boss, disconnecting from gold for a 4.6% gain over the last two days.  

Is somebody (or some firm) keen on silver and not so keen on gold, or might a barrier have been tested on an option expiring at quarter-end?

We just moved into quarter-end, and both GLD and SLV moved slightly higher into the 4 pm close, on some synchronized, high volume (right around 3:59 pm).  

But perhaps the 3:33 pm move, unique to silver, (on high volume) is interesting.  Silver hits a peak at 3:33 pm, so perhaps a barrier was tested, say on a knock-in knock-out option.

You can see the additional volume spike in the lower silver graph -- but not in the gold above -- just before the close.

And this graph zooms in on the price movement (up) on the very short infusion of interest in the silver market at 3:33 pm today. It then losing some of its gains before pushing higher again into the close at 4 pm.

Graphs courtesy of Bloomberg LP.