Northumbria police have arrested the other youth on suspicion of murder and he is currently being held in police custody.
Detectives believe that that an altercation occurred in Gill Street at about 23:00 BST last night, during which Mark was stabbed.
Mark made his way via Axbridge Gardens to Elswick Road before collapsing at the junction with Caroline Street.
Detective Chief Inspector Roger Ford, who is leading the murder investigation, said: "We believe that at the time this happened, around 23:10 BST, there were a number of people in the areas of Gill Street, Axbridge Gardens and Elswick Road and I have no doubt that members of the public who were walking, driving or living in the area would have seen or heard something.
"I would urge these people to contact the police urgently. Knife crime is completely unacceptable and it's vital that people come forward with information."
A post-mortem examination is ongoing but police have confirmed that Mark died from a stab wound.
Last night's attack is likely to prompt further concern about teenage knife crime, with a string of stabbings having recently taken place in Britain.
Last Saturday a 16-year-old boy suffered a punctured lung after being stabbed in an apparently unprovoked attack in north Manchester, while Adam Regis, the 15-year-old nephew of Olympic sprinter John Regis, was stabbed to death in east London in March.
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