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Far-field stress changes in the southern Australian plate since 5 Ma have produced significant areas of uplift and seismicity. In northwest Tasmania, there is evidence that this stress reorientation to maximum horizontal NW–SE stress has influenced meteoricderived thermal (15–20°C) discharge patterns of confined karstic aquifers, by placing pre-existing NWtrending faults/fractures into a dilated state or a critically stressed state. Previous studies have shown that spring discharge has operated continuously for at least 65,000 years, and has transported large volumes of solutes to the surface to be deposited as mounds of calcite-goethite-silica up to 7 m high. The thermal spring chemistry at one site, Mella, is consistent with descent to at least 1.2–1.5 km, although the hinterland within 50 km is less than 500 m elevation. Thermal spring chemistry is consistent with most of the deep water–rock interaction occurring in low-strontium Smithton Dolomite. While some of this water is discharged at springs, some instead intersects shallow zones of NE-fracture-controlled rock (2×4 km in area) with karstic permeability where, although confined and subject to a NE-directed hydraulic gradient, it circulates and cools to ambient temperature, with only minor mixing with other groundwaters.

Item Type:	Refereed Article
Keywords:	Thermal springs . Karst . Far field stress .Hydrogeochemistry Tasmania
Research Division:	Earth Sciences
Research Group:	Hydrology
Research Field:	Hydrology not elsewhere classified
Objective Division:	Environmental Management
Objective Group:	Other environmental management
Objective Field:	Other environmental management not elsewhere classified
UTAS Author:	Davidson, GJ (Dr Garry Davidson)
ID Code:	74790
Year Published:	2011
Web of Science® Times Cited:	2
Deposited By:	Centre for Ore Deposit Research - CODES CoE
Deposited On:	2011-12-13
Last Modified:	2017-11-06
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