"For they have taken of their daughters for themselves, and for their sons: so that the holy seed have mingled themselves with the people of those lands: yes, the hand of the princes and rulers has been chief in this trespass"(Ezra 9:2).
The implication of this passage is clear. The "holy seed" of Israel had mixed with the "unholy" seed. Here we do not have a prohibition of interracial marriage. So Albert Barnes:
"Abominations - The mixed marriages had prevented that complete separation of the people of God from the idolatrous rites, or "abominations," which the Law required, and which was necessary for purity of religion."
"so that the holy seed; such as the Lord had separated from other nations, chosen them to be an holy people above all others, and devoted them to his service and worship"