Potash Corp. of Saskatchewan (POT: sentiment, chart, options) has been popular in the options pits today, with call volume soaring to sky-high levels. The stock's July 120 call has seen more than 21,600 contracts change hands so far today, while its July 100, 110, and 130 calls have each seen more than 10,000 contracts cross the tape. After further research, however, it seems that the majority of the aforementioned activity is related.

At 11:40 a.m. Eastern time, the following changed hands: a block of 10,000 July 110 calls for $0.80; a block of 20,000 July 120 calls for $0.20; a block of 10,000 July 130 calls for $0.15. All three trades were marked "late," making it impossible to tell if they were bought or sold. Nevertheless, the bones of the trades appear to be a split strike butterfly (aka broken wing butterfly, skip strike butterfly).

With this strategy, the trader would have bought the 110- and 130-strike calls, while selling twice the amount of 120-strike calls. In this case, the investor would've incurred a net debit of $0.55 ([$0.80 + $0.15] [$0.20 x 2]). The objective of this slightly bullish option play is for the shares of POT to finish right at the $120 level (sold call strike) when options expire on Friday, July 17.

Heading into the close, the security is trading near the $97 level, a gain of $5.90, or 6.5%, from yesterday's close.