This trip to explore the serpentinite in Collins Valley was made possible by the kindness of the land owner, One-Forty-One Forestry, who gave permission for the visit. It took in two sites - the quarry and a long exposure on a forestry track to the south of SH60 (see map, right). 

Both lie on the western edge of a broad band of Patuki Melange, which has been intruded into Permo-Triassic rocks on the Rai Saddle.

​The Patuki Melange has been emplaced by collision of the Dun Mountain Ophiolite Belt with the sedimentary Pelorus Group rocks as a result of seafloor spreading during the late Permian or early Triassic. The resulting melange consists of large boulders, mainly of sedimentary rocks, embedded in a serpentinite matrix. The matrix is highly sheared, as evidenced by the slickensiding (photos, below),

The walk into the quarry showed exposures of the Triassic Greville Formation and Tramway Sandstone (though the latter here consists mainly of mudstones).  In the quarry face, different facets of the melange were visible, including bouldery beds of sedimentary material, and layers of dark grey-greenish serpentinite.

At the second site, to the south of SH60, a long sequence was examined through the edge of the serpentinite, which here was deeply weathered, To the south-east this gave way not to sedimentary of the Ward Formation, as expected, but to an unmapped diorite-like rock, veined with ?quartz. 

Serpentinite Quarry
​

Slickensided serpentinite boulders

Exposure through edge of serpentinite