Dr. Ian Nicholls

Newer Volcanics eruptive centres in the Central Highlands sub-province

 
Supervisor(s): Ian Nicholls 
Field of Study: Field relations / volcanology of mafic-intermediate lavas / pyroclastics; petrology, geochemistry
Support Offered: Field and analytical costs
Preferred Program: Honours (including mid-year)

While many studies have been carried out on volcanic complexes in the Western Plains sub-province of the 4.6 Ma to 5000 yr Newer Volcanics Province in western Victoria, there are literally tens to hundreds of similar basaltic complexes and eruption points further north in the Central Highlands – especially north and west of Ballarat. A quick look at the Geoscience Victoria Creswick and Waubra 1:50,000 maps gives a clear impression of the density of scoria and lava cones and rarer tuff rings and maars in this area - maps #83 and 84.
Following up on GSV mapping, these centres urgently need at least reconnaissance studies of their volcanology and the petrography, petrology and geochemistry of their lavas and pyroclastic deposits. It will also be interesting to see whether any of these centres have mantle peridotite xenoliths and/or crustal xenoliths, which will give us clues to the nature of the lithosphere in the area. .
For further information conatact Ian Nicholls.

 

Small Late Devonian granitic bodies associated with the Acheron and Cerberean "cauldrons" (calderas filled with thick ignimbrites), central Victoria

 
Supervisor(s): Ian Nicholls 
Field of Study: Field and relationsships between small Late Devonian granitic intrusions (ring, dykes) and caldera-filling ignimbrites; petrology, geochemistry
Support Offered: Field and analytical costs
Preferred Program: Honours (including mid-year)

The major Late Devonian rhyolite-dacite ignimbrite caldera sequences northeast of Melbourne either overlie or are intruded by a number of relatively small granitic bodies. The largest and most interesting of these is the Black Range Granodiorite, which lies at the northwestern corner of the Acheron Cauldron – see the western edge of the Warburton 1:250,000 map. According to most recent mapping, the main Black Range body extends northward into at least 4 isolated much smaller bodies with similar characteristics (these and the main body are given the same Intrusion number #223 in e.g. “The Geology of Victoria”). These possibly define part of an outer “ring dyke” of the Cerberean Cauldron. However the granites appear to be hornblende-bearing, low-Al I-types, whereas the caldera ignimbrites (and the Strathbogie Batholith, further north) are cordierite-bearing, high-Al S-types. The spatial and age relationships between the granites and ignimbrites, and the petrology and geochemistry of the granites, are in need of a detailed study to attempt to understand any genetic relationships between the various rock types and their parent magmas.
For further information conatact Ian Nicholls.