Journal and Proceedings of
The Royal Society of New South Wales
Volume 125 Parts 1 and 2 [Issued June, 1992]
CONTENTS
AUTHORS & TITLES
Middlemost, E.A.K., Dulhunty, J.A. and Beck, R.W., Some Mesozoic Igneous
Rocks from Northeastern New South Wales and their Tectonic Setting
PAGES
1-11
Brown, J.K., Health Hazards Associated with Extremely Low Frequency
Electromagnetic Fields from Power Lines and Home Appliances
13-17
Doctoral Thesis Abstract
Coenraads, Robert R., Alluvial Sapphire and Diamond Deposits of the New
England Gem Fields, New South Wales, Australia
[Not extracted here, but available on this page]
19-21
v125, pts 1-2, pp.1-11
Some Mesozoic Igneous Rocks from Northeastern New South Wales and their Tectonic
Setting
E.A.K. Middlemost, J.A. Dulhunty and R.W. Beck
Abstract. K-Ar ages, mineralogy and petrology of a group of volcanic and subvolcanic rocks
from northeastern New South Wales is reported. They range in age from Late Permian (250
±10 million years, or Ma) to Early Cretaceous (10 ±4 Ma) and comprise a basanite, a variety
of basalts and two nepheline normative microsyenites. To develop a model that can account
for their origin and evolution, the Permian and Mesozoic magmatic history of eastern
Australia is evaluated. From the Early Permian to the end of the Early Cretaceous the
magmatic history of New South Wales was frequently interlinked with the evolution of the
linear tectonic feature that became the Sydney- Gunnedah- Bowen Basin System. During the
Late Cretaceous the magmatic and tectonic history of New South Wales was dominated by
the processes of rifting and drifting that led to sea-floor spreading in the Tasman Basin.
For most of the Early Permian a magmatic focus was located beneath the proto- SydneyGunnedah-Bowen Basin System. It produced an extensive belt of volcanoes that extruded a
diverse range of products. The next major magmatic epoch was active during the Late
Permian and Early Triassic. It produced extensive silicic magmatism in New England and
northwards into Queensland. In the Sydney and Gunnedah basins high-K basanitic, basaltic,
trachybasaltic, shoshonitic and latitic materials erupted. Throughout the Mid to Late Triassic
large volumes of andesitic, dacitic and rhyolitic rocks were extruded in southeastern
Queensland. During the Early to Mid Jurassic more alkaline magma was introduced into the
Sydney- Gunnedah- Bowen Basin System and elsewhere in eastern Australia. This magmatic
epoch includes the eruption of the Garrawilla Volcanics in the Gunnedah Basin, and a variety
of alkaline diatremes and intrusives in the central and northwestern parts of the Sydney
Basin. Throughout the Jurassic and Cretaceous small volumes of basanitic/basaltic magma
erupted in the Sydney Basin, In the Early Cretaceous there was renewed calc-alkali activity
along a volcanic chain that extended from Bowen via Rockhampton and then on to the Lord
Howe Rise. At the beginning of the Late Cretaceous the rifting and separation of the Lord
Howe Rise/New Zealand plate from eastern Australia shifted the major magmatic focus to
beneath the zone of active spreading. Rifting triggered the eruption of the alkaline volcanic
and plutonic rocks in the Mt Dromedary cluster of ring complexes and led to changes in the
pattern of sublithospheric convection. These processes gave rise to the Eastern Highlands
which became a new locus for widespread intraplate volcanism.
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v125 pts1-2, pp.13-17
Health Hazards Associated with Extremely Low Frequency Electromagnetic Fields
from Power Lines and Home Appliances
J.K Brown
Summary Paragraph. [p.17] The scientific evidence of whether or not power frequency
EMFs poses a cancer risk remains unresolved. No conclusion can be reached on the basis of
current data due to serious deficiencies in all the studies. However, there is consensus opinion
that the present results indicate the need for further epidemiological studies of highly exposed
populations with the use of personal dosimeters and daily diary records monitoring EMF
exposure over long periods, preferably years.
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