I have posted a post which shows up above your last one on the message board with listings for Benjamin Tonks (a Benjamin Tonks. Even if they are not connected to your Benjamin they may help other researchers.
But I did find a listing for the marriage of Benjamin Digby Tonks on the 26th Jan 1882 in Auckland to Mary Elizabeth Buckland ( she was b. 1861).
From where did the Tonks originally come from - eg what part of the UK before emigration?