Palaeozoic Geology of Victoria. 115 



In general these rocks are usually light in colour, varying from 

 light cream to pale green. Sometimes their fragmental character 

 can be recognised macroscopically. In Section A, No. 6 specimen 

 represents a coarse crushed porphyry breccia, with red jasper shale 

 and chloritic inclusions. The mechanical stresses have developed 

 a considerable amount of sericite and thin sections show in addi- 

 tion secondary silicitication. The red jasper has the' appearance of 

 an altered igneous rock, possibly a diabase or andesite; traces of 

 felspar can be recognised, and hematite is disseminated through 

 it. Fragments of fine grained acid igneous rocks, are also present. 



On the other hand, many of the rocks of this group have a very 

 fine texture, with their original character so altered that even thin 

 sec-tions may not give any satisfactory evidence concerning their 

 primary nature, but, on the whole, the microscopic examination 

 clearly points to the fact that they are dynamically altered acid 

 porphyrites and ash beds. 



Specimen 1, Boggy Creek, is a hard schistose rock, which in the 

 thin section, shoAvs a distinctly fragmental character. There is a 

 fine micro-crystalline base of quartz and felspar, in part sericitic,. 

 and set with irregular fragments of plagioclase and quartz, the 

 former predominating. The felspar is probably an oligoclase- 

 albite. Vivid green chlorite is abundant as well as sericite. 



No. 2 is a light grey porphyroid, the thin section showing abun- 

 dant sericite and no chlorite. Small fragments of plagioclase fels- 

 par are present. 



No. 18, Ironstone Creek, is a sericitic rock of similar type, with 

 recognisable granular quartz, but all trace of the felspar has been 

 obliterated. 



No. 19, Ironstone Creek, is a coarse-grained sericitic rock, with 

 a definite schistose structure. Occasional plagioclase fragments are 

 recognisable, and some chlorite is present. Among the inclusions 

 one fragment may represent an altered andesite. The result of in- 

 tense stress is well shown. 



A belt of these porphyroids, 10-12 feet wide, in the bed of Boggv 

 Creek (No. 63, Map 5), is highly pyritic, and micaceous hematite 

 is widely distributed, frequently sparsely disseminated and 

 associated Avith red jasper and ordinary quartz, but occasion- 

 ally moderate outcrops of fairly piire hematite can be observed. 

 More often, however, the ore is highly siliceous and lenticular in 

 occurrence. The iron ores, however, are not restricted to the por- 

 phyroids, but the micaceous variety appears to be the characteristic- 



