Speaking at a mid-year town hall meeting last week, Thornton said the company held assets that were neither tier one, nor strategic.
"You can conclude from what I've said, the likelihood of us continuing to own those over time is zero," he said.
"We may own them for period of time, for a variety of different reasons."
Thornton used Hemlo in Canada as an example, given its tier one jurisdiction and tax losses that could be used.
"So, the question is, ‘for how long is that valuable, and at what point is that asset more valuable to somebody else?'" he said.
"And the answer, if you could wave a wand, you'll sell it at exactly the point at which it's the highest value to someone else and we don't need it anymore.
"And there are other assets like that in our portfolio right now, and we are constantly assessing this exact question with respect to those assets.
"KCGM is another one, Lagunas is another one.
"We are constantly assessing ‘what do we think of those assets which are neither tier one nor strategic, and when we will get rid of them?'"
Barrick ran a sale process in 2016 for its KCGM stake. China's Shandong Tyan Home Co was the leading bidder with a rumoured A$1.3 billion offer, but withdrew from talks last year.
Since then, Barrick has said it was "perfectly happy" to continue to own the asset.
Thornton estimated there were 10-15 tier one assets globally, of which Barrick held four.
He defined a strategic asset as one that was not tier one, but had distinct long-term value, such as Veladero due to its location in the El Indio belt.
"I hope the tier one definition is crystal clear, strategic is clear, and things that aren't those two things are clear—we won't in the fullness of time own them," Thornton said.
Barrick went into copper in a big way in 2011 via the C$7.3 billion takeover of Perth's Equinox Minerals, an acquisition Thornton described as "if not the worst, one of the five worst acquisitions in [mining] history".
Thornton said Barrick's copper assets were a natural fit with the portfolio, given limitations around tier one gold assets.
"And so the question for us on copper is, ‘can you take the copper assets, combine them with another party or even two parties and build a first-tier global copper company over time?'" he said.
"Now in answering that question, the likelihood that your partner in that endeavour will be Chinese is very high.
"Why? For the same reasons they're the right partner for Veladero, which is China has got an appetite for copper for as long as the eye can see, they're very long-term in orientation, they need it, they're already buying up copper, so it makes all kinds of sense. So the likelihood of that being the case is very high."
Barrick last month entered into a strategic cooperation agreement with China's Shandong Gold Group, its 50% partner at Veladero.
The two companies will consider opportunities to work together on joint acquisitions or asset sales.
Thornton said Barrick would be just as disciplined on acquisitions as it had been on divestments.