New tire with mold flash still showing + your tire seems to be covered with light stone powder + a relatively smooth and worn/polished road could result in this. As you are breaking in a new tire you also have to remember that 100 km on a highway or local roads means just the center of the tread has the mold release worn off. The first time you lean it over aggressively you're on slippery new tire all over again. Were you accelerating relatively aggressively as well?