[{id:1,Pages:[{Fields:[{FieldName:"field1",Value:"the fox"},{FieldName:"field2",Value:"is brown"}]}]},{id:2,Pages:[{Fields:[{FieldName:"field1",Value:"jumps"},{FieldName:"field2",Value:"the fox"}]}]}]

db.collection.find({"Pages.Fields":{"$elemMatch":{"FieldName":"field1","Value":"the fox"}}})