| Abstract |
Cuttings from five geothermal wells at Ngawha, New Zealand 18, 20) and Puna, Hawaii (HGP-A and were analysed for at Results show a primary control by temperature over concentration and a consequent distribution which reflects the form of the present. Adsorbed is stable in rocks up to Hg in silicates to in pyrite to 300?C and over 320?C the values are comparable to unaltered rocks and low. The location of a well within a field relative to zones of permeability is important and higher values in shallower parts may reflect the more permeable location. Temperature, however, must also be considered and higher values throughout a hole may reflect lower temperatures. Apart from any shallower enrichment by adsorbed forms of. Hg, downhole enrichment was found to be associated with secondary minerals; those having formed directly from solution by boiling containing higher concentrations than those formed by processes involving steam separation - condensation. Repeat analyses over time show that after periods on the order of one year appreciable Hg can be lost during storage, and after several years most of the introduced to the rock can be lost, at least for lirhologies such as basalt. |