* Quintana holds off Froome attacks * Colombian will lead to Madrid * Froome (Adds details, quotes) MADRID, Sept 10 (Reuters) - Nairo Quintana effectively clinched his first Tour of Spain title after holding off a series of Chris Froome attacks in Saturday's decisive mountain stage. Tour de France champion Froome had taken a huge chunk out of Quintana's lead in Friday's time trial and knew his last chance was to launch a devastating attack in the final climbs. Froome duly obliged, repeatedly trying to surge away from Movistar's Quintana and reduce the one minute 21 seconds gap on the Alto Aitana climb, but he could not break his rival and ended up no closer. More...