Testing EQ3/6 and GEMBOCHS using fluid-mineral equilibria in the wairakei geothermal system

Bruton, C.J.

doi:10.2172/641095

Cited by 5 publications

(4 citation statements)

References 17 publications

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“…At P(CO 2 ) ϭ 1 MPa, the epidote and most of the wairakite fields are covered by the "calcite blind". Quartz thermodynamic data from Fournier (1983); remaining data from Johnson and Lundeen (1994) with equilibrium constants of wairakite reduced by 0.6 log units to better represent commonly observed relations between wairakite and fluid chemistry in New Zealand geothermal systems (Bruton, 1995). tion of more than 99 percent of the original liquid occurred locally during the deposition of sphalerite in the Broadlands -Ohaaki geothermal system, New Zealand. Carman (2003) proposed open-system boiling as the mechanism to explain the origin of salinities ranging from 5 to Ͼ40 weight percent NaCl equivalent in anhydrite-hosted inclusions from the Ladolam gold deposit on Lihir Island, Papua New Guinea.…”

Section: Discussionmentioning

confidence: 99%

The evolution of volcano-hosted geothermal systems based on deep wells from Karaha-Telaga Bodas, Indonesia

Moore¹,

Allis²,

Němčok³

et al. 2008

American Journal of Science

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Temperature and pressure surveys, fluid samples, and petrologic analyses of rock samples from deep drill holes at the Karaha -Telaga Bodas geothermal field on the volcanic ridge extending northward from Galunggung Volcano, West Java, have provided a unique opportunity to characterize the evolution of an active volcanohosted geothermal system. Wells up to 3 km in depth have encountered temperatures as high as 353 o C and a weakly altered granodiorite that intruded to within 2 to 3 km of the surface. The intrusion is shallowest beneath the southern end of the field where an acid lake overlies a nearly vertical low resistivity structure (<10 ohm-m) defined by magnetotelluric measurements. This structure is interpreted to represent a vapordominated chimney that provides a pathway to the surface for magmatic gases.Four distinct hydrothermal mineral assemblages document the evolution of the geothermal system and the transition from liquid-to vapor-dominated conditions. The earliest assemblage represents the initial liquid-dominated system generated during emplacement of the granodiorite between 5910 ؎ 76 and 4200 ؎ 150 y BP. Tourmaline, biotite, actinolite, epidote and clay minerals were deposited contemporaneously at progressively greater distances from the intrusive contact (assemblage 1). At 4200 ؎ 150 y BP, flank collapse and the formation of the volcano's crater, Kawah Galunggung, resulted in catastrophic decompression and boiling of the hydrothermal fluids. This event initiated development of the modern vapor-dominated regime. Chalcedony and then quartz were deposited as the early low salinity liquids boiled (assemblage 2). Both vapor-and liquid-rich fluid inclusions were trapped in the quartz crystals. Liquid-rich fluid inclusions from the southern part of the field record salinities ranging from 0 to 26 weight percent NaCl-CaCl 2 equivalent and locally contain fluorite daughter crystals. We suggest, based on temperature-salinity relationships and evidence of boiling, that these fluids were progressively concentrated as steam was lost from the system. However, mixing with fluids derived from the underlying intrusion or generated during the formation of acid SO 4 water on the vapor-dominated chimney margins could have contributed to the observed salinities. As pressures declined, CO 2 -and SO 4 -rich steam-heated water drained downward, depositing anhydrite and calcite (assemblage 3) in the fractures, limiting further recharge. Fluid inclusions with salinities up to 31 weight percent NaCl equivalent were trapped in these minerals as the descending water vaporized. The final assemblage is represented by precipitates of NaCl, KCl and FeCl x deposited on rock surfaces in portions of the vapor-dominated zone that boiled dry. Vapor-dominated conditions extend over a distance of at least 10 1 km and to depths below sea level. Deep wells drilled into the underlying liquiddominated reservoir in the northern and central part of the volcanic ridge produce low salinity fluids representing recent recharge of meteoric and ste...

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Section: Discussionmentioning

confidence: 99%

The evolution of volcano-hosted geothermal systems based on deep wells from Karaha-Telaga Bodas, Indonesia

Moore¹,

Allis²,

Němčok³

et al. 2008

American Journal of Science

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“…Bruton (1995) has demonstrated, for example, that the thermodynamic properties of the silica polymorphs have an important influence on the results achieved in simulations such as those carried out here, which involve zeolites and other complex silicates. The implication of this point for the work presented here is that the exact geographical distribution, total abundance of a mineral phase, and the identity of a specific mineral phase is somewhat uncertain.…”

Section: Model Uncertainties and Limitationsmentioning

confidence: 81%

Predicting mineral alteration at the potential nuclear waste repository at Yucca Mountain, NV with reactive transport modeling

Glassley¹

1998

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April 1998This is an informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-ENG-48. DISCLAIMERThis document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.This report has been reproduced directly from the best available copy. ABSTRACTWe present the results of a reactive transport modeling study that examines the sensitivity of mineral evolution to temperature, condensate properties and water flow conditions anticipated to occur in the potential Yucca Mountain nuclear waste repository site. We have investigated a key aspect of the thermal-hydrological repository system, the interaction of condensate water flowing through fractures at the site. Future simulations will include mineral changes at the boiling front, a process not considered in this study.Our simulations show that the principal mineral changes that occur are dissolution of the initial phases (mainly calcite, but also feldspars and clay) and formation of zeolites and hydrated aluminous phases. Major differences in mineral alteration occur over very short distances. Fracture mineral alteration is clearly coupled with the thermal hydrological environment. Fracture porosity is enhanced in those areas where condensate forms, an upper, lower temperature condensate zone and a lower, high temperature condensate zone. The locations where mineral precipitation occur and porosity decreases depend on the integrated residence time of the solution on the fracture surface. In general, mineral precipitation is expected to occur in the region ~150 m above the water table. Whether the changes in porosity are significant enough to modify thermohydrological behavior remains to be evaluated.

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“…Because most water penetrating the NFE is expected to enter via fracture flow, this section focuses on the composition of this water. Extensive previous studies (Bruton, 1996;Bruton et al, 1993;Bruton and Viani, 1992;Carroll et al, 1996;Johnson and Glassley, 1996;Knauss, 1987;Knauss and Copenhaver, 1995;Viani and Bruton, 1991 and see Section 5.3 of this report) have evaluated the likely interactions that may result through reaction primarily with matrix material. The results of these reports are not described here because the effect of such waters on repository materials is expected to be minimal.…”

Section: Chemical Composition Of Water In the Altered Zone Before Entmentioning

Testing EQ3/6 and GEMBOCHS using fluid-mineral equilibria in the wairakei geothermal system

Cited by 5 publications

References 17 publications

The evolution of volcano-hosted geothermal systems based on deep wells from Karaha-Telaga Bodas, Indonesia

The evolution of volcano-hosted geothermal systems based on deep wells from Karaha-Telaga Bodas, Indonesia

Predicting mineral alteration at the potential nuclear waste repository at Yucca Mountain, NV with reactive transport modeling

Near-field/altered-zone models report

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