"...what % of this volume would be sales to exercise warrants?"

I don't believe that exercising a warrant ever shows up on the tape, and thus it wouldn't show up in the volume numbers. I think exercising is done through the transfer agents, behind the scenes. None of it would show up on the tape.

I should note though, that close to the exercise date, you will usually see extra trading activity in the warrants. Many, perhaps most, retail warrant holders probably don't want to put up the extra cash, the exercise price. Instead they will sell the warrant on the open market before the exercise date. Such warrants will often be picked up by arbitragers or market makers, who pick up large quantities of warrants and then make a small profit when they submit the shares for conversion. If the warrant is dangerously close to being out of the money though, the arbitragers would tend to stay away, not wanting to get burned with warrants that might all of a sudden become worhless.

The above is for widely held warrants. I assume these San Gold warrants are closely held, since I can't find quotes for them, and since they don't appear on the canadianwarrants.com website. But I believe even the exercise of closely held warrants would not show up on the tape. However, it's possible that extra share trading activitiy could result due to warrant holders selling shares obtained by exercising their warrants.