Faure, K. ; Brathwaite, R.L. 2000 Stable isotope composition of deep to shallow palaeo-geothermal fluids in the Hauraki Goldfield, Coromandel. Lower Hutt: Institute of Geological & Nuclear Sciences. Institute of Geological & Nuclear Sciences science report 2000/14 14 p.
Abstract: Samples from relatively deep to shallow palaeo-geothermal systems were collected from the Ohio Creek porphyry Cu-Au deposit, the Waihi Au-Ag epithermal deposit and the Kuaotunu extension quartz veins. Hydrogen and oxygen isotope, and fluid inclusion, measurements reveal that geothermal fluids flowing through the early stages of these systems were dominated by hot, saline, magmatic waters at depth and by cooler, dilute, meteoric water near surface. These results are not totally unexpected, but the data do raise the question on the validity of hydrogen isotope data obtained from water released by thermal decrepitation of fluid inclusions in epithermal vein quartz. The results indicate mixing of magmatic water with meteoric waters which have unrealistically low values. Mechanical decrepitation of fluid inclusions in quartz should be investigated to evaluate the results obtained from thermal decrepitation of fluid inclusions. (auth)