A Dorchester man who has become one of the state’s leading authorities on urban planning will return to his native Detroit this month to take on a key role in that city’s administration. James Arthur Jemison will become Detroit’s chief of Housing and Revitalization under Mayor Mike Duggan. Most recently, Jemison has served as the state’s Deputy Undersecretary of Housing and Community Development for the Patrick administration. The UMass Amherst graduate lives with his wife Annie and their children in the Ashmont-Adams neighborhood, where they have been deeply involved in civic life. Jemison was born in Detroit, but was raised in Massachusetts.