In my knowledge It should mean that the veins came in later and cut the volcanic units however I am unsure if there is more to the particular case.

Describing veining that cross cut the host generally means that the veins are younger than the unit...

But I would readily defer to a more knowledgable answer.. I do not know the mine situation first hand...

It does make a person wonder what event created the veins and where they originated from if they are youger than the host... which they would have to be in order to cut the host... the angle (90 degree) may provide a clue.. would have to see more ..

Just an opinion

cheers