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The sentence in question: 子どもたちの表情は、いきいきと輝いていました

For full context: https://www3.nhk.or.jp/news/web_tokushu/2018_0521.html?utm_int=news_contents_tokushu_004

My attempt at translation: "The facial expression of the children shone in a lively way."

I wonder why と is used there? There is no reported speech or conditional clause involved. The only thing I can imagine is some connection to the "A が B と なる" function, because the facial expression "becomes" sparkling/shining when piggybackriding.

Or is いきいき and onomatopoeion and this is one of these cases where と just appears because of this onomatopoeion ?^^

marked as duplicate by Chocolate grammar May 31 '18 at 12:30

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