Reaction-path calculations of groundwater chemistry and mineral formation at Rainier Mesa, Nevada

Kerrisk, J.F.

doi:10.2172/59163

Cited by 20 publications

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“…A similar zonation might be expected where ground water became increasingly sodic or less silicic with depth, but bulk-rock chemistry shows that zones III and IV probably formed in an essentially closed chemical system with no Naenrichment compared to clinoptilolite-bearing rocks in zone II. Kerrisk (1983) concluded that aqueous silica activity decreases from waters in equilibrium with cristobalite to waters in equilibrium with quartz, and controls the mineral evolution with depth. Therefore, the deeper diagenetic zones at Yucca Mountain may be an indirect result of the transformation of cristobalite to quartz with depth.…”

Section: Factors Controlling Diagenesismentioning

confidence: 99%

Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada

Broxton

Bish

Warren

1987

Clays and clay miner.

121

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Abstract--Yucca Mountain is being studied as a potential site in southern Nevada for an underground, high-level nuclear waste repository. A major consideration for selecting this site is the presence of abundant zeolites in Miocene ash-flow tufts underlying the region. Beneath Yucca Mountain four diagenetic mineral zones have been recognized that become progressively less hydrous with depth.Zone I, the shallowest zone, is 375-584 m thick in the central part of Yucca Mountain, but 170 m thick to the north. Zone I contains vitric tufts that consist of uualtered volcanic glass and minor smectite, opal, heulandite, and Ca-rich clinoptilolite. Zone II thins south to north from 700 to 480 m and is characterized by complete replacement of volcanic glass by clinoptilolite with and without mordenite, and by lesser amounts of opal, K-feldspar, quartz, and smectite. Zone III thins south to north from 400 to 98 m thick and consists of analcime, K-feldspar, quartz, and minor calcite and smectite. Heulandite occurs locally at the top of zone III in the eastern part of Yucca Mountain. Zone IV occurs in the deepest structural levels of the volcanic pile and is characterized by albite, K-feldspar, quartz, and minor calcite and smectite.Clinoptilolite and heulandites in zone I have uniform Ca-rich compositions (60-90 mole % Ca) and Si:AI ratios that are mainly between 4.0 and 4.6. In contrast, clinoptilolites deeper in the volcanic sequence have highly variable compositions that vary vertically and laterally. Deeper clinoptilolites in the eastern part of Yucca Mountain are calcic-potassic and tend to become more calcium-rich with depth. Clinoptilolites at equivalent stratigraphic levels on the western side of Yucca Mountain have sodic-potassic compositions and tend to become more sodium-rich with depth. Despite their differences in exchangeable cation compositions these two deeper compositional suites have similar Si:A1 ratios, generally between 4.4 and 5.0. Analcimes have nearly pure end-member compositions, typical of these minerals formed by diagenetic alteration of siliceous volcanic glass; however, K-feldspars are Si-rich compared to the ideal feldspar formula.Bulk-rock contents of Si, Na, K, Ca, and Mg of zeolitic tufts generally differ significantly from stratigraphically equivalent vitric tufts, suggesting that zeolite diagenesis took place in an open chemical system. Both the whole rock and the clinoptilolite are relatively rich in Ca and Mg in the eastern part of Yucca Mountain and rich in Na in the western part. The Ca-and Mg-rich compositions of the zeolitized tufts in the eastern part of Yucca Mountain may be due to cation exchange by the sorptive minerals with ground water partially derived from underlying Paleozoic carbonate aquifers.Diagenetic zones become thinner and occur at stratigraphically higher levels from south to north across Yucca Mountain, probably due to a higher geothermal gradient in the northern part of the area. The diagenetic zones were established when the geothermal gradient was greater than it ...

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Section: Factors Controlling Diagenesismentioning

confidence: 99%

Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada

Broxton

Bish

Warren

1987

Clays and clay miner.

121

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“…Also, no tridymite, Cristobalite, or opal-CT was identified in the original analyses. These phases are important in understanding mineral reactions with depth (Kerrisk 1983;Bish 1986). The relationship between clinoptilolite and Cristobalite in the tuffs supports aqueous silica activity as the controlling variable in the clinoptilolite-to-analcime reaction.…”

Section: Mineral Distributions In Drill Holes J-13 Ue-26a#1 Anmentioning

confidence: 91%

Mineralogy of drill holes J-13, UE-25A No. 1, and USW G-1 at Yucca Mountain, Nevada

Bish¹

1986

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The mineralogy of drill holes J-13, UE-25A#1, and USW G-l was previously determined using qualitative and semiquantitative techniques, and most of the available data were neither complete nor accurate. New quantitative x-ray diffraction data were obtained for rocks from all three of these drill holes at Yucca Mountain, Nevada. These quantitative analyses employed both external and internal standard x-ray powder diffraction methods and permitted the precise determination of all phasei commonly found in the tuffs at Yucca Mountain, including glass and opal-GT.These new data supplant previous analyses and include numerous additional phases. New findings of particular importance include better constraints on the distribution of the more soluble silica polymorphs, cristobalite and opal-CT. Opal-CT was associated solely with clinoptilolite-bearing horizons, and cristobalite disaopearance coincided with the appearance of analcime in USW G-l. Unlike previous analyses, we identified significant amounts of smectite in drill hole J-13. We found no evidence to support previous reports of the occurrence of erionite or phillipsite in these drill holes.

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“…Mordenite is commonly formed along with smectite during the initial stages of volcanic-glass dissolution (Kerrisk, 1983). As replacement proceeds, smectite is transformed to filiform or fibrous bundles of mordenite.…”

Section: Origin Of Alteration Minerals In Gougesmentioning

confidence: 99%

Characteristics of Clay Minerals in Gouges of the Dongrae Fault, Southeastern Korea, and Implications for Fault Activity

Choo¹,

Chang

2000

Clays and clay miner.

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Abstract--The Dongrae fault within the Yangsan fault system is considered one of the major faults in the southeastern part of Korea, extending over 150 km. The results of K-Ar radiogenic dating of fault gouges collected from six localities show a relatively wide range in age from 57.5 million years ago (Ma) to 40.3 Ma. Fault gouges are composed of newly formed minerals, including smectite, illite, zeolite, kaolinite, K-rich feldspar, apatite, and pyrite. The occurrence of abundant smectite and illite-lM d with lesser quantifies of zeolite suggests that the fault gouges experienced hydrothermal alteration at low temperatures. Smectite is probably unstable relative to other clay minerals, such as illite and zeolite. Considering that filiform mordenite is replacing the smectite, we suggest that mordenite formed by recrystallization involving a solid-state transformation. Under high fluid/rock ratios, smectite seems to have formed in the early stage of alteration. In contrast, zeolite minerals and authigenic K-rich feldspar progressively appeared with time as the fluid/rock ratio decreased with the changing chemistry of the hydrothermal fluids. The composition of clay minerals in the gouge materials probably was controlled by the chemistry and the amount of circulating fluids derived from adjacent granitic rocks.

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Reaction-path calculations of groundwater chemistry and mineral formation at Rainier Mesa, Nevada

Cited by 20 publications

References 0 publications

Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada

Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada

Mineralogy of drill holes J-13, UE-25A No. 1, and USW G-1 at Yucca Mountain, Nevada

Characteristics of Clay Minerals in Gouges of the Dongrae Fault, Southeastern Korea, and Implications for Fault Activity

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