48 
General Notes on the Geology of the District. 
The clay and magnesite form part of the extensive lacustrine deposits of 
the Bacchus Marsh district. From the enclosed fossil vegetable remains, 
which occur plentifully in certain places, these beds are usually considered 
to be of older Tertiary age. In the vicinity of Rowsley the whole deposit 
has been covered by a sheet of basalt, but since this rock was poured out by 
the volcanic agencies many deep valleys have been cut out by the Parwan 
and its tributaries. Close to Mr. O'Keefe’s farm the Brisbane Ranges, which 
are formed of Ordovician slates and sandstones, begin and extend in a south¬ 
westerly direction. It is extremely probable that the south-eastern face of 
these hills marks a fault line, which is continued both northerly and southerly 
as a basalt escarpment separating basalt plains which occur at different levels. 
The top of the basalt plateau at Mr. O’Keefe’s house is about 1,030 feet above 
sea level. 
In regard to the origin of the magnesite it is very probably formed by the 
percolation of water containing carbonic acid through the clay. Such water 
would attack decomposing magnesian silicates and convert the magnesia into 
a carbonate, which would be carried in solution to favorable situations and 
there precipitated. 
[28.5.12.] 
REEF MINING, NEAR LOVEY’S LEAD, MARONG GOLD-FIELD. 
By H. S. WMtelaw , Field Geologist. 
The mining lease dealt with in this report consists of portions of allotments 
5 and 6, section X, in the parish of Marong, If miles west of the township of 
Marong, and 10 miles west of the city of Bendigo. 
The surface of the lease consists of alluvial deposits of sand and clay cover¬ 
ing Ordovician slates and sandstones, which form the bed-rock of the surround¬ 
ing region. Auriferous gullies trend generally westward towards the Berry- 
Moolort-Loddon deep-lead system. While working the gravels in one of these 
gutters, known as Lovey’s lead, auriferous reef-quartz, in situ , was discovered 
at 100 feet below the surface and 200 feet north-east of the south-west angle 
of allotment 6. At this spot a winze sunk 18 feet on the quartz shows the 
reef to be between 2 feet and 3 feet wide, dipping about 65° E., with no sug¬ 
gestion of walls. For a depth of 15 feet fair gold was obtained. From the 
bottom of this winze, No. 1 intermediate level was driven along the reef- 
channel for about 23 feet, the last 15 feet being in payable quartz between 
fairly firm walls 2 ft. 6 in. apart. From the end of this level No. 2 winze was 
sunk 20 feet, the reef to within 2 or 3 feet of the bottom maintaining its width, 
dip and value, but presenting a somewhat rubbly appearance, due to a series 
of small faults which fracture it. From the bottom, which is in poor quartz, 
No. 2 intermediate level was driven southward 35 feet to a fault, and to the 
end of the payable gold. These workings show the shoot to be about 20 feet 
in length, measured horizontally, and to pitch to the southward (S. 20° E.) at 
an angle of about 30° ; measured along the pitch it is 60 feet in length. 
In all 205 tons of quartz have been crushed for yields aggregating 113 oz. 
12 dwt. of gold, equal to 11 dwt. 2 gr. per ton ; the first crushing cleaned up 
in December, 1909, returned 39 oz. 16 dwt. ; the last in May of this year 
yielded 11^ oz. from 55 tons, which is barely payable. The working condi¬ 
tions at this stage becoming unfavorable, a new 8 ft. x 3 ft. shaft was sunk. 
At a depth of 175 feet in this shaft, which is in allotment 5, and 150 feet S.S.E. 
of the old shaft, a cross-cut has been driven 35 feet eastward, cutting the reef 
i 
