PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
40 
alteration of the dolomite to olivine and phlogopite to metamorphism 
caused by the basic dyke. My own examination of the area of the mine 
led me to entirely different conclusions, on which the following remarks 
are based. 
The area is composed of a highly metamorphosed series, consisting 
of interstratified amphibolites (basic sills or altered basalts), felspathic 
quartzites, acid gneisses, basic gneisses and schists. This series is 
intruded by dykes of later amphibolite and, still later, by pegmatitic 
dykes of an acid magma. (See figure 1.) 
Ph/oqop/t? 
fcoclk mar// 
NW 
Ph/ogop'ite QVAUTZITE 
PocA hanging 
K-/MBZRLJ T£__ _ 
A Ol/A//T£ '\ \ V 
. Joint 
Hit A 8ook 
Ph/ogopite. 
DyAe. 
SE 
HAZZBURGITE 
foot 
*/• 
y/at/f 
QUAZTZ / 
Horizontal Cross Section of the Ph/oyopite Dyke . 
Fig. 2. 
The phlogopite occurs in a large basic dyke allied to gabbro, which 
differentiated into three zones : — a harzburgite, consisting of hypersthene, 
bronzite, augite, enstatite and magnetite, with a little basic felspar and 
olivine, on the footwall side ; an olivine rock in the middle ; and gabbro. 
allied to kimberlite, on the hanging-wall side. (See figure 2.) The hanging- 
Avall rock consists in some parts of olivine-augite rock with spinel, in some 
parts of the same minerals with some phlogopite. In places a rock consist- 
ing mainly of phlogopite has been developed. In the footwall part of the 
dyke there are also considerable lenses of pure magnetite. Whether this 
differentiation of the magma took place in its first cooling period or in 
the period of subsequent metamorphism is not clear. 
The phlogopite dyke can be followed on the surface for about half a 
mile varying in width of outcrop between 50 and 200 feet. It strikes 
north-north-west, and appears to dip at a very high angle to the east- 
north-east. Towards its northern end it is faulted in an interesting 
manner by a pegmatite dyke. At two points on the outcrop, one near 
the north and one near the south end, occur some small outcrops of 
crystalline dolomitic limestone, which contributed to the idea that the 
dyke was altered limestone. These occurrences are, however, only 
secondary limestone. The gneissic series is variable in strike in the area, 
but mostly west-north-west in the neighbourhood of the dyke. The 
still later pegmatite intrusions branch considerably, but the largest strike 
east-north-east. Several small pegmatitic veins occur in the immediate 
neighbourhood of the phlogopite mine, but none have been noticed as 
yet in the basic dyke rocks. Several intrusions of a rock resembling 
aplite also occur in the vicinity, but this rock so closely resembles some 
of the adjoining metamorphic rocks (the felspathic quartzites) that its 
identity is doubtful. 
