Volmink (left wing) was in top form to run in three tries during the match, while prop Khwezi Mona crashed over twice and flyhalf George Whitehead added 13 points with the boot through five conversions and a penalty to set up the comfortable win.
The victory ended the small chance the Gautengers had of sneaking into the semi-final positions, while making sure that last year's finalists would finish second in the North Section behind the unbeaten iSG Pumas.
The Kimberley side will only know their opponent after the final two games in the South Section are completed at the SuperSport Rugby Challenge Festival at Florida Park in Cape Town on Sunday.
The first half was a back-and-forth affair with the Griquas scoring three converted tries to two from the Lions, while Whitehead's successful penalty pushed their lead out to 10 points at 24-14 at the break.
The second half was then very similar, also ending with the home side scoring three tries to two, while visiting flyhalf Eddie Fouche missed one of his conversion attempts, leaving the score 45-26 at full time.
Tafel Lager Griquas - Tries: Anthony Volmink (3), Khwesi Mona (2), Gideon van der Merwe. Conversions: George Whitehead (5), Tinus de Beer. Penalty goal: George Whitehead.
Xerox Golden Lions XV - Tries: James Venter, Mandisi Mithiyane, Dillon Smit, Kenedy Mpeku. Conversions: Eddie Fouche (3).