The stage race was Dean's first back following a fractured shoulder suffered at the GreenEdge training camp in the Australian Alps in early December. The 36-year-old had been due to return to racing at the Tour of Sardinia which was cancelled.
Wednesday's accident took place just 10 kilometres into the shortened queen stage. Dean was swerving to avoid riders who had crashed ahead of him on the slippery road, following horrific weather conditions in the Pyrenees, when he collided with a parked car.
"We are especially distraught about this loss," GreenEdge sports director Neil Stephens explained on the team website. "From a sporting perspective, it's terrible to lose a rider to a crash. From a personal perspective, we really feel for him. He has a lot of bad luck this year, and Catalunya was his first race back after a previous injury.
"The race took a really nervous start because of a hard climb in the opening kilometres. We went around a slippery right-hand corner, and some guys crashed in front of Julian. In an attempt to avoid them, Julian swerved and he hit a parked car."
Dean was transported by ambulance from Barcelona to his Valencia base, accompanied by GreenEdge sports director Vittorio Algeri.
"I have spoken to him and what I do know is that it's a severe break, it's going to need an operation which will possibly be plates, and therefore three to six months," Dean's wife Carole told Fairfax Media.
"Three months being the very happy end of the scale and six being crap, so basically it's the season."
"He's pretty tenacious and he doesn't sit on his bum and do nothing," Carole Dean continued. "He pushes his body through rehab, so it might be four months if we're lucky.
"The best case scenario I can think of is that he'll be ready to start the Tour of Spain. That might be a good starting point, but certainly the Giro and the Tour are out."
Dean signed a one-year deal with GreenEdge at the end of 2011, non-committal to his cycling future beyond 2012, saying "I am just looking one year at a time, and there are no specific plans to race in 2013. But you never say 'never'."