The incident could hardly have happened at a worse position for the Chinese boat, 240 nautical miles (nm) from Cape Horn in southern Chile, one of the most remote places on Earth.
The breakage in the top section of the mast means that the team cannot properly manoeuvre the boat. No members of the nine-strong crew on board were injured.
The team originally announced that they would have to quit the leg but now they are investigating whether they can continue after making repairs in Argentina.
“There’s still a possibility we could limp all the way to Brazil — the leg destination — and that way we’d still earn two points. It may make all the difference in the end. We’ll see,” said a team spokesman.
The boat’s French skipper Charles Caudrelier sent a message to his team, saying he was devastated by the breakage.
The team of Chinese rookies had been joint leaders of the nine-month, offshore marathon race with Abu Dhabi Ocean Racing at the halfway stage.
“The mast broke without warning, in about 30 knots of wind,” saif Caudrelier. “We are unable to sail safely on starboard tack, but we are able to make reasonable speed on port tack. We will head towards Ushuaia, Argentina, and assess our options.”
The team was on its way to Itajaí, south-eastern Brazil, from Auckland, New Zealand on the 6,776nm leg when the accident happened.
Volvo Ocean Race organisers said they had alerted maritime safety organisations and were doing everything they could to assist the crew.
It is the second major breakage to hit the seven-strong fleet since the race began on Oct. 11 from Alicante, Spain.
On Nov. 29, during the second leg in the Indian Ocean, Denmark’s Team Vestas Wind badly damaged their boat after it smashed into a reef.
The crew escaped unhurt after wading through waters known to be shark-infested to reach safety.
The Volvo Ocean Race is generally reckoned to be the toughest offshore challenge in sailing. In 2011-12, five of the six-strong fleet suffered major breakages.
In all, the 2014-15 race will cover 38,739nm, visiting 11 ports and every continent. It is due to conclude in Gothenburg, Sweden, on June 27.
(Editing by Ken Ferris)