An Australian snowboarder who died after a fall on the back-country slopes near the Mt Cheeseman Ski Area was not wearing a safety helmet.

Tim Stone, 29, slipped about 100 metres down an icy slope and into a stony riverbed in Tarn Basin on Friday afternoon.

The Sydneysider sustained severe head injuries and was taken by helicopter to Christchurch Hospital, where he died on Sunday afternoon.

Stone was with two colleagues when he fell. One stayed with him while the other ran for 1 1/2 hours to raise the alarm.

Jeremy Stone used a Facebook posting to praise Tod Mason and Nathaniel Jamieson for helping his younger brother "in his time of greatest need".

Jeremy Stone described the snowboarder as "my beautiful brother and great mate".

A separate posting on Jeremy Stone's Facebook page also praised Mason.

"Thank you for risking your life on Friday Tod in a selfless way, to run and rush back to help. Thank you for pulling Tim out of the water. Thank you for being such a good mate all through your times together," it stated.

The Press understands Tim Stone's parents are flying to Christchurch from a holiday in Alaska.

Mountain Safety Council avalanche and alpine programme manager Andrew Hobman visited the accident scene on Friday.

He said the trio had been struggling to traverse the slope because of the heavily compacted snow.

Stone removed his board and attempted to proceed on foot and slipped down a 45-degree slope and into the stream, Hobman said.

"His colleagues got to him and pulled him out of the stream and did a fantastic job in looking after him and running all the way out," he said.

"It is absolutely tragic when things like this happen. They were visitors really enjoying what we have to offer and it is absolutely tragic that it should have to end like this."

Hobman said skiers and snowboarders should wear helmets to reduce the risk of head injuries.

The Mountain Safety Council recommended a helmet.

Mt Cheeseman Ski Area manager James Young said the snowboarders were outside the patrolled area.

People were advised to check signs showing snow conditions before venturing out of bounds, he said.

The slopes in Tarn Basin could be patchy, with icy areas that had melted and then frozen again.

"Our procedures are comprehensive and more than adequate. It is just one of those things. We can't tell people not to go there and we can't force people to follow our advice," he said.

Ad Feedback Young said it was "very desirable" to wear a helmet, when skiing or snowboarding, but they could not compel people to wear them. Signs in the gear-hire area recommend helmets, which can be hired for about $10 a day.

A Canterbury District Health Board spokeswoman confirmed the death was being referred to the coroner.