Investor Presentaiton
THE GEOLOGIC SETTING
Several heat-producing granites were (mostly) emplaced in eastern Tasmania during a
period of tectonic compression ~400Mya, which joined Eastern and Western Tasmania
terranes along the largely concealed Tamar Fracture Zone (TFZ): upper figure.
~50Mya Tasmania became part of an extensional regime associated with the
separation of Australia and Antarctica, with a number of grabens developing. In the
Lemont region the bounding faults "..form a complex transfer zone that is expected to
have high fracture permeability" (Berry, 2019: lower figure).
Lastly, Tasmania is located over an interpreted hot spot, the East Australia Plume
System (upper figure), which may explain some of the legacy high heat flow
measurements scattered across the State. (Continental crust averages 65mW/m².)
Spa*ark Energy_21
TFZ
Eastern
Terrane
159
104
83
Western
Terrane
87
Upper Figure: Radio-isotope enriched granites were emplaced during the Devonian, associated
with a compressional regime bringing Tasmania's Western and Eastern Terranes together.
(Eastern outcropping granites in pink: Western ones not shown). High heat flow legacy
measurements support the hypothesis of a 'hot spot' beneath Tasmania (green dashed line from
Davis et al, 2015). The TFZ marks the approximate location of the paleo-plate boundary,
Depth contours from 1km to 9km show the granite deepens rapidly to the west (Leaman, 2012).
Lemont outline included for reference.
Devonport
Port Sorell.
Sub-basin
Lower Figure: Major Tertiary faults (from Berry, 2019). Tasmania was an extensional regime
during this period with several grabens opening up. Berry (2019) regards the "complex transfer
zone" within the Lemont outline as likely to have high permeability.
Tamar
Graben
Macquarie Harbour
Graben
Tiers
94
Longford
Sub-basin
N
Oyster
Bay
Upper
Derwent
Graben
Graben
50 km
Lower
Derwent
GrabenView entire presentation