I work in Wythe County Virginia and I have found the marriage record for Robert Burchett and Alverta.
Wythe County VA Courthouse: Marriage Book 2A, Page 145
Robert Burchette, age 23, born Smyth County VA, married Alvertine Haden, age 22, born Wythe County VA, on 12 Jan 1890. Both were residents of Wythe County. His father was listed as "not known," but his mother's name was Elizabeth Burchette. Her parents were listed as James M. Haden and Eliza Sayers. They were married by S.T. McPherson.
I found James Haden's marriage record on page 58 of the same book.
James Haden, farmer, age 24, married Eliza Sayers, age 26, divorced, on 1 June 1871. Both were listed as having been born in Wythe County, but he was a resident of Grayson County and she of Wythe. His parents were listed as not known and her parents were listed as David Sayers and Grisly Sayers. They were married by A. Fisher.
I spoke with the archivist at the Kegley Library at Wytheville Community College and she said she is not aware of any Indian reservations having been located in the Ivanhoe area, let alone Wythe County, although there may have been pockets of settlements here and there. The marriage records mention nothing about any of these people being Native Americans.