Hydrogen just doesn't get bound up into minerals (unless essentially as water) and not at any great density, and there isn't another plausible substance that would be hanging out in a canyon on mars.
tbc I don't believe there's oil on mars nor do I think it is remotely likely.
“Methane (CH4) is abundant on the giant planets—Jupiter, Saturn, Uranus and Neptune—where it was the product of chemical processing of primordial solar nebula material. On Earth, though, methane is special. Of the 1,750 parts per billion by volume (ppbv) of methane in Earth’s atmosphere, 90 to 95 percent is biological in origin.”[1]
[1] https://www.scientificamerican.com/article/methane-on-mars-t...
Melting (freezing) point 195.42K-77.73°C
The pressure on mars is too low for liquid ammonia to exist and the freezing/sublimation temperature is more like 180K or -100C
And to exist underground in large amounts for millions or billions of years it’s not good enough for temperatures to occasionally be low enough to freeze ammonia, when it was warmer the ammonia would turn into gas and blow away so unless there is a significant local source of ammonia it is highly doubtful that is where the hydrogen comes from.