Sparking
c130jbloke
Your observation is correct. The fan blades are made from Titanium, Ti6-4 alloy to be exact. It is the same alloy used to make titanium golf club heads. They, too, spark when being hit from a tee that has sand accumulation or when hitting out of a sand trap, impressive at dawn or dusk!
Observing it at the fan casing is good as it means the majority of the sand particles are being flung outward and will pass through the fan by-pass instead of being ingested into the core. Over time, some erosion will result at the tips of the fan blades or in the acoustical liners along the walls of the fan casing.
Turbine D