Jeremiah 15:7

I have fanned them with a fan "Fan, whether verb or noun, is now practically obsolete in the sense here intended." Dr. p. 360. We should rather render, Have winnowed them with a winnowing-fork. The Arabic word midhra, corresponding to the Heb. mizrehhere and in Isaiah 30:24, is "in use in modern Syria, and denotes a wooden fork almost six feet in length, with five or six prongs, bound together by fresh hide, which, on shrinking, forms a tight band.… The wooden shovel of Isaiah 30:24 was used with it. The mixture of corn, chaff, and broken straw, produced by threshing, was shaken about with these two implements, usually in some exposed spot, when a wind was blowing (generally in the afternoon or evening, Ruth 3:2), and the wind carried away the chaff and the straw (Psalms 1:4). If however the wind was too violent it would blow away the corn as well: hence the point of Jeremiah 4:11." Ibid.

the gates of the land the borders(the parts by which men enter and leave the country). Cp. Nahum 3:13.

they have not returned from their ways LXX have, on account of their evils(wicked deeds), probably meant as a free paraphrase, unless we suppose the word for evilsto have fallen out of MT.