Around a dozen bands and several hundred people are expected to attend this Sunday’s Ancient Order of Hibernians parade at Greencastle.
The parade is to a centuries-old Mass Rock believed to be under threat by operation of a gold mining company.
The Tyrone Hibs have called on Catholics to descend in droves upon the pilgrimage site on Sunday afternoon.
The event will mark the 100th anniversary of the Marian apparitions at Fatima.
The parade, due to start at 3pm, will also be used to highlight concerns that the ancient Mass rock could be destroyed.
The Dalradian Gold Company wants to develop a mine in the area and plans to build a processing plant in the area to extract the precious metal from ore mined locally.
They have disputed the claims that the Mass Rock is on land they control.
“The Greencastle parish website indicates that there are three Mass Rocks in the parish,” it said.
“None of these sites are on land controlled or owned by Dalradian. We have no evidence of a Mass Rock on land owned or controlled by us.”