River have won their last three games and have 18 points from nine matches, two more points than title holders Estudiantes and Olimpo.
Colon, who had begun the championship with great promise, sacked coach Fernando Gamboa after a fourth successive home defeat, 2-0 to Olimpo, and have slipped to mid-table.
At a packed Monumental, River's inspirational captain Matias muscled his way past three defenders and sent Pavone through into the box where the striker held off a challenge to steer the ball in off the base of the far post.
Coach JJ Lopez's team began the Clausura more concerned about their poor relegation average and the prospect of a promotion playoff than the possibility of the title.
But a mixture of sturdy defence, the skills of teenage playmaker Erik Lamela and the overall mediocrity of the championship sees them leading the pack at the halfway stage.
Colon's Gamboa was sacked with his team on 13 points having won four and lost four of their nine matches but it was their home form at their Elephant's Graveyard ground in Santa Fe that saw him fall.
"(Club president) German (Lerche) said the situation was untenable because of the results at home," Gamboa, whose side had won a difficult away match against San Lorenzo the previous weekend, told reporters.
"There isn't much to explain, nor have I made an analysis (of the situation)," added Gamboa.
On Friday, Estudiantes were held 0-0 at home by San Lorenzo.
