Natural and synthetic quartz growth and dissolution revealed by scanning electron microscope cathodoluminescence

Scanning electron microscope-cathodoluminescence (SEM-CL) reveals textures in quartz that are not observable using any other technique. CL textures in hydrothermal quartz reflect primary precipitation processes that are modified by subsequent dissolution, deformation, fracturing, or recrystallization. Superposition of multiple textures in individual quartz veins yields complex textures with obscure origins. To infer the processes that form complex CL textures in natural hydrothermal quartz, we analyzed samples from eighteen ore deposits of five types as well as synthetic quartz formed in three flow reactor autoclave experiments conducted at up to 50

Permeability and Thermal Conductivity Measurements of Near Surface Units at the Wairakei Geothermal Field, New Zealand

ABSTRACT Thirty one outcrop and drill core samples (to about -500 mRL) from geothermal wells from Te Mihi, western Wairakei Geothermal Field (New Zealand), have been analysed for their mineral assemblage and hydrothermal alteration, thermal conductivity, permeability, bulk rock porosity and density, as part of a study on the affect of the geological parameters on the thermal conductivity. At Wairakei, cores of Huka Falls Formation (soft, lacustrinedeposited tuff and sediments), Waiora Formation (variably consolidated, medium hard, hydrothermally altered volcanic tuff) and Karapiti Rhyolite (hard, altered rhyolite lava and breccias) were analysed from wells WK223, WK224 and WK227 (unaltered/least altered field margin); WK206, WK207, WK212, WK219 and WK247 (Te Mihi upflow zone); and WKM14, WK205, WK210, WK213 and WK221 (infield, south and east of Te Mihi). The effect of hydrothermal alteration (rank and intensity) on thermal conductivity was tested by analysing samples from the same stratigraphic units from different wells, albeit with a range of styles of hydrothermal alteration (e.g. claydominated argillic, characterised by a progression from smectite to illite-dominated clay assemblages, to propylitic). Results demonstrate a good correlation between porosity and thermal conductivity, but no clear relationship between permeability and thermal conductivity. We also compared permeability and thermal conductivity from the Wairakei Field samples with data from rocks in central Europe

Very Long Baseline Interferometry with the SKA

Adding VLBI capability to the SKA arrays will greatly broaden the science of the SKA, and is feasible within the current specifications. SKA-VLBI can be initially implemented by providing phased-array outputs for SKA1-MID and SKA1-SUR and using these extremely sensitive stations with other radio telescopes, and in SKA2 by realising a distributed configuration providing baselines up to thousands of km, merging it with existing VLBI networks. The motivation for and the possible realization of SKA-VLBI is described in this paper