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PACIFIC SCIENCE, Vol. XXI, January 1967 
Volcanic conglomerate outcrops east of the 
Motupiko River and consists of rounded spilitic 
pebbles up to 3 cm in diameter, set in a chloritic 
groundmass (vuw 10658). 2 Phenocrysts of 
oligoclase feldspar are partially altered to epi- 
dote and seracite. The volcanic conglomerate is 
faulted against Stevens formation (Maitai se- 
ries) by the Waimea Fault. 
Te Anau Series 
Grindley (1958:22) defined the Te Anau 
series in Otago as Upper Paleozoic (post-De- 
vonian) sediments, volcanics, and intrusives 
deposited or erupted prior to the deposition of 
the Lower Permian Maitai limestone and not 
subsequently converted into schist or gneiss. 
In the Tophouse district, the Te Anau series is 
represented by the Wairau ultramafic mass and 
the Te Anau volcanics and underlies the Maitai 
limestone. 
Wairau Ultramafic Mass 
This mass is one of the two unserpentinized 
ultramafic masses of the Nelson ultramafic belt 
(see Fig. 1). A similar belt of ultramafic rocks 
extends southeastward from the Alpine Fault in 
Otago. The Red Mountain ultramafics of Otago 
(Grindley, 1958) are similar mineralogically to 
the Wairau ultramafic mass of South Nelson. 
The rocks of this mass consist of peridotite 
and serpentinite. The largest exposure of perid- 
otite is at the "Plateau,” a peneplain surface 
2,400 ft above the Wairau Valley. Northward 
of the Plateau, the peridotite becomes progres- 
sively dissected, resulting in craggy crests and 
steep, scree-covered slopes. While the Maitai 
rocks and Te Anau volcanics are covered by 
beech forest and scrub, the ultramafic rocks are 
covered by tussock grass only. 
The Wairau ultramafic mass is faulted to the 
south, west, and possibly to the east. Air photo- 
graphs show a strong lineation at 57° which is 
due to the alignment of dikes composed prin- 
cipally of pyroxenite. Banding, similar to that 
described by Fless (I960) in the Stillwater com- 
plex of Montana, is found along the whole 
western edge of the ultramafic mass. The coarse 
bands, consisting of pyroxenite and varying 
2 These numbers refer to rock catalogue numbers 
of specimens stored in the Geology Department, 
Victoria University of Wellington, New Zealand. 
from 1 to 2 cm in width, are repeated hun- 
dreds of times within any outcrop. The dip in 
the area mapped is relatively low, from 20° to 
40° E. The relationship of the banding to the 
general lineation referred to above is complex, 
and was not studied in detail. 
The rocks of the Plateau include dunite, 
ortho- and clinopyroxene peridotite and harz- 
burgite. These rocks are dark green and coarse- 
grained, and contain crystals up to 0.5 cm in 
diameter. Bands of resistant orthopyroxenite 
frequently stand out on the surface of the 
weathered rock. The pyroxene in the peridotite 
varies in type. Chromite is the sole accessory 
mineral. The dunite consists of large interlock- 
ing crystals of olivine, showing "strain” lamel- 
lae, and accessory chromite which occurs as 
elongate crystals, 2 mm in length. The density 
of the peridotites is constant at 3.30 ± 0.05 
gm/cc for fresh unserpentinized samples and 
provides the density contrast of 0.6 gm/cc 
between the peridotites and New Zealand grey- 
wacke (the basement rock of 2.70 gm/cc den- 
sity which is assumed to underlie the perido- 
tite). 
Serpentine containing hydrogrossular out- 
crops in the center of the Plateau and is coarse- 
grained, dark blue, and massive. Hydrogros- 
sular is set within mesh serpentine in the rock, 
and olivine relicts as well as diopside fragments 
are abundant. The rock contains 10% granular 
magnetite. The gradational nature of the con- 
tact between the serpentinite and the surround- 
ing peridotite suggests a metasomatic origin for 
the serpentinite. 
Crushed serpentinite outcrops along a belt 
west of the Maitland Fault and forms the west- 
ern boundary of the Wairau ultramafic mass. 
The Maitland Fault is the boundary between 
this serpentinite and the undeformed peridotite 
of the Plateau. The serpentinite is light green 
in color and breaks readily into green lensoid 
fragments 5-10 cm in diameter and 1-3 cm in 
thickness. Rocks near the Maitland Fault con- 
sist of antigorite serpentinite with slip fiber 
structure and are composed of large tabular 
crystals of antigorite with minor diopside. Tabu- 
lar crystals of magnetite 2.5 mm in diameter 
form at least 10% of the rock by weight. 
Amphibolite and rodingite occur as a wedge 
in the northeast corner of the area mapped (Fig. 
