66 
trend of the Mann Ranges, if produced in an easterly direc- 
tion across the intervening tract of sandhills, is in the same 
straight line as the axis of the Musgrave Ranges. 
Both ranges consist of igneous intrusions^ and altered 
sedimentary and igneous rocks. The western portion of the 
Mann Ranges, of no great width at this end, consists almost 
wholly of igneous exposures. In the centre the '3ore of 
igneous intrusion is flanked on either side, namely, its north- 
ern and southern boundaries, by complexes of gneiss, schist, 
and gneissic quartzite ; whereas on the eastern limits of the 
range, by far the widest portion, the main intrusion lies hid- 
den beneath the metamorphic series, into which it was in- 
jected, to appear once more at the surface to the eastward, in 
the Musgrave Ranges. 
A ground plan of the metamorphic exposures of the 
Mann Ranges gives roughly a U-shaped form, the flanks that 
skirt the middle of the ranges forming the straight arms of 
the U, the curved base of the letter being represented by the 
thicker mass of crystalline schists at the eastern end. 
As a rule, the trend of the ranges coincides with the 
strike of the rock, except in a few instances, where irregu- 
larity of stress produced by igneous intrusion has interfered, 
and where a local bulging out of the mass, no doubt the 
result of an igneous offshoot, has produced a spur, the axis of 
which does not conform with the general direction of the 
range. 
Though mineralogically not as rich as the Musgrave 
Ranges, the Mann Ranges are geologically of particular 
interest, as they exhibit many examples of rock movements 
and fracture that accompanied igneous intrusion, t 
Igneous Rocks.~An intrusion of granite has been by far 
the greatest, it continuing uninterruptedly as the backbone 
of the whole range, to disappear under superincumbent 
gneisses on the east, and occurring as isolated outliers for a 
considerable distance to the west. The character of the rock 
varies, passing from a true granite (in portions porphyritic) 
to various metapyrigen gneisses. + J ^ 
OAo ^m^P>T^ J. Forrest, Explorations in Australia, III., page 
T n~ -^^^ ^^^ri Ranges are composed of reddish granite." Also 
J. Oarruthers :— "The Mann Ranges are covered with pines blood- 
wood, a tew scattered gums, dense spinitex, and scattered patches 
of coai-se grass, the foiTnation being red and grev granite "— 
(Adelaide Observer, January 16, 1892, page 9.) 
+1 aI^^"!?^^'^ ^^^ statement:—". . . hills and mountains of 
the Mann Ranges, some few of the Musgrave chain, and all west 
ot the Mann Ranges have been shivered into fragments bv vol- 
?g"i^^?i;^«^ • •.. ."-E. Giles, Geogr. Travels in Centr. Austr., 
l»/^-187d, Part, ii., page 103. 
I The term as employed by Dr. J. W. Gregory. 
