The Atacama Desert is very rich in iodine. Next to nothing grows there, however... Perhaps the Iodine drifts/washes down to the desert from the Andes. Perhaps it was once under the sea...
Some Maca is "supposedly" rich in both Iodine and iron dependent upon where it is grown; a double plus if one needs both. Not too hard to believe given the mineral content analysis of the soil where it is most often grown.
Unfortunately, trace mineral content of foods is rarely, if ever listed...
Maca is grown in many places including Chile; mineral content will vary dependent upon soil... although considering most soils it is grown in are volcanic and Iodine content at the earths core is rather high...