How does friction and radiolysis provide hydrogen for "unusual types of methane"?
I found this paper 1 trying to understand what is radiolysis. The decomposition of water by ionization happens at basaltic aquifers on the seafloor, close to seabed. 


  "Water radiolysis is the decomposition of water molecules by ionizing
  radiation produced during the decay of radioactive elements (Debierne,
  1914; Le Caër, 2011). The principal radioactive elements that produce
  ionizing radiation in basalt are uranium (238U and 235U), thorium
  (232Th), and potassium (40K), which collectively emit alpha (α), beta
  (β), and gamma (γ) radiation as they and their daughter nuclides
  decay. Transfer of energy from this radiation excites and ionizes
  water molecules, producing several chemical species: eaq-, HO•, H•,
  HO2•, H3O+, OH-, H2O2, and H2 (Spinks and Woods, 1990; Le Caër, 2011)."





  "The oceanic basement contains the largest aquifer on Earth. Its
  fractured rock contains nearly 2% of Earth’s total volume of seawater
  (Johnson and Pruis, 2003). Although the extent of life and microbial
  activity in oceanic basement is not well known, a variety of evidence
  suggests that microbes reside within the aquifer (Cowen et al., 2003;
  Edwards et al., 2012; Jungbluth et al., 2013; Lever et al., 2013;
  Orcutt et al., 2013). Fisk et al. (1998) and Staudigel et al. (2008)
  report weathering textures suggestive of microbial alteration in
  subseafloor basaltic glass."





  For subseafloor environments, we are particularly interested in the
  production of the reductant H2. Many organisms catabolically utilize
  H2, including methanogens, sulfate-reducers, iron reducers, and
  nitrate reducers (Fang and Zhang, 2011). There is evidence that some
  of these organisms, specifically sulfate reducers and methanogens, are
  active in subseafloor basalt (Lever et al., 2013). Radiolysis
  undoubtedly occurs in subseafloor basalt, as both water and radiation
  are present. Edwards et al. (2012) suggested that in the old and
  relatively weathered basaltic basement of the South Pacific Gyre
  (SPG), radiolytic H2 may be the dominant electron donor.




Trying to understand how hydrogen can be formed by friction I found this other one 2 where the author asociates it to earthquakes, listing three possible origins for hydrogen and saying the frictional origin is still a not well known process. Apparently it happens at fault systems when there are mouvements on lithosphere:


  In the last few decades, three different abiotic H2 generation
  processes have been proposed: 
  
  
  (1) water–rock redox reactions, mostly under hydrothermal conditions    [Janecky and Seyfried, 1986; Coveney et al., 1987],
  (2) radiolytic reactions of H2O [Savary and Pagel, 1997], and
  (3) mechanoradical formation on wet fault surfaces during earthquakes    [Wakita et al., 1980].
  
  
  H2 production by peridotite‐
  water and komatiite‐water hydrothermal reactions, as modern and
  ancient analogs, respectively, has been quantitatively estimated in
  laboratory experiments [Seyfried et al., 2007; Yoshizaki et al.,
  2009]. Radiogenic production of H2 is supported by the analysis of
  H2‐bearing fluid inclusions in quartz containing U‐bearing minerals
  [Dubessy et al., 1988], and has been quantitatively estimated in a
  laboratory g‐irradiation experiment [Lin et al., 2005]. The H2 flux
  per unit of surface area from redox reactions has been estimated to be
  3 × 10−4 mol/m2 yr from a 1 km column of mafic/ultramafic rock with 10
  wt% FeO [Sleep and Zoback, 2007], and the estimated flux from water
  radiolysis in the Witwatersrand basin, South Africa, is 8 × 10−6
  mol/m2 yr [Lin et al., 2005]. In contrast, the H2 flux associated with
  earthquakes and its significance in subsurface ecosystems has not yet
  been explored in either the field or laboratory.


After making experimental flux calcs the paper says this mechanism may have been important for methanogens. And not only eartquakes but meteorite impacts too may have been a source of mollecular hydrogen for primigenious  life not only on Earth but on other planets.


  "Thus, seismic activity and the consequent release of H2 might have
  sustained subsurface microbial communities as long ago as 3.8 Ga.
  Moreover, mechanoradical H2 generation can be induced by meteorite
  impacts as well as by earthquakes, and thus might play an important
  role in the evolution of subsurface biosphere not only on Earth but
  also on other planets."


1 Dzaugis Mary E., Spivack Arthur J., Dunlea Ann G., Murray Richard W., D’Hondt Steven (2016). "Radiolytic Hydrogen Production in the Subseafloor Basaltic Aquifer" Frontiers in Microbiology, 7, ISSN=1664-302X   

2 T Hirose, S Kawagucci, K Suzuki (2011) "Mechanoradical H2 generation during simulated faulting:
Implications for an earthquake‐driven subsurface biosphere." Geophysical research letters.