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B.-S. King

Publications and source records attributed to B.-S. King.

5 recordsLinked to original sources
USGS1996

Spatial radon anomalies on active faults in California

Radon emanation has been observed to be anomalously high along active faults in many parts of the world. We tested this relationship by conducting and repeating soil air radon surveys with a portable radon meter across several faults in California. The results confirm the existence of fault-associated radon anomalies, which show characteristic features that may be related to fault structures but vary in time due to other environmental changes, such as rainfall. Across two creeping faults in San Juan Bautista and Hollister, the radon anomalies showed prominent double peaks straddling the fault gouge zone during dry summers, but the peak-to-background ratios diminished after significant rain fall during winter. Across a locked segment of the San Andreas fault near Olema, the anomaly has a single peak located several meters southwest of the slip zone associated with the 1906 San Francisco earthquake. Across two fault segments that ruptured during the magnitude 7.5 Landers earthquake in 1992, anomalously high radon concentration was found in the fractures three weeks after the earthquake. We attribute the fault-related anomalies to a slow vertical gas flow in or near the fault zones. Radon generated locally in subsurface soil has a concentration profile that increases three orders of magnitude from the surface to a depth or several meters; thus an upward flow that brings up deeper and radon-richer soil air to the detection level can cause a significantly higher concentration reading. This explanation is consistent with concentrations of carbon dioxide and oxygen, measured in soil-air samples collected during one of the surveys.

Applied Geochemistry↗
USGS1993

Radon anomalies on three kinds of faults in California

Radon emanation is known to be anomalously high along active faults in many parts of the world. We tested this relationship in California during July and early August 1992, using a portable radonmeter to conduct soil-air radon surveys at 5 sites across three kinds of faults: Creeping, locked, and freshly broken. Along a 350-m long survey line across a creeping segment of the San Andreas fault at Nyland Ranch in San Juan Bautista, we found anomalous radon concentrations not in the creep zone itself as determined by a creepmeter, but on the adjacent sides, 10 and 30 meters from the center line of the fault. The anomalous values were 5 times higher than the background values measured farther away from the fault. A similar radon anomaly was observed along a 420-m long survey line across a creeping segment of the Calaveras fault near 7th Street in Hollister. There, the anomalous values were about 6 to 11 times the background values and about 40 and 50 m from the center line of the fault. The double-peaked featire of the anomalies may be indicative of a relatively low gas permeability of the fault-gouge materials in the creeping zones and high permeability of fractured rocks in the adjacent shear zones. Along a 144-m survey line across the currently locked segment of the San Andreas fault at the Earthquake Trail near Olema, the radon concentration was indeed anomalously high in the fault zone, by a factor of two above background values. However, the maximum values (3 to 6 times background) again were recorded about 10 meters from the center line. Three weeks after the magnitude 7.5 Landers earthquake of 28 June 1992, we conducted a survey along a 300-m line across the earthquake fault alongside Encantado Road in the epicenter area. The radon values measured at the two main fault breaks were an order of magnitude higher than the background values. A similar result was found along a 420-m line alongside Reche Road about 1.7 km south of Encantado Road. ?? 1993 Birkha??user Verlag.

Pure and Applied Geophysics PAGEOPH↗
USGS1992

Chemical, crystallographic and stable isotopic properties of alunite and jarosite from acid-Hypersaline Australian lakes

Chemical, crystallographic and isotopic analyses were made on samples containing alunite and jarosite from the sediments of four acid, hypersaline lakes in southeastern and southwestern Australia. The alunite and jarosite are K-rich with relatively low Na contents based on chemical analysis and determination of unit cell dimensions by powder X-ray diffraction. Correcting the chemical analyses of fine-grained mineral concentrates from Lake Tyrrell, Victoria, for the presence of halite, silica and poorly crystalline aluminosilicates, the following formulas indicate best estimates for solid-solution compositions: for alunite, K 0.87 Na 0.04 (H 3 O) 0.09 (Al 0.92 Fe 0.08 ) 3 (SO 4 ) 2 (OH) 6 and for jarosite, K 0.89 Na 0.07 (H 3 O) 0.04 (Fe 0.80 Al 0.20 ) 3 (SO 4 ) 2 (OH) 6 . The δD-values of alunite are notably larger than those for jarosite from Lake Tyrrell and it appears that the minerals have closely approached hydrogen isotope equilibrium with the acidic regional groundwaters. The δD results are consistent with a fractionation ∼60–70‰ between alunite and jarosite observed in other areas. However, interpretation of δD results is complicated by large variability in fluid δD H2O from evaporation, mixing and possible ion hydration effects in the brine. δD-values of water derived from jarosite by step-wise heating tend to be smaller at 250°C, at which temperature hydronium and other non-hydroxyl water is liberated, than at 550°C, where water is derived from the hydroxyl site, but the differences are not sufficiently different to invalidate measurements of total δD obtained by conventional, single-step heating methods. δ 34 S-values for alunite and jarosite from the four lakes (+19.7 to +21.2‰ CDT) and for aqueous sulfate from Lake Tyrrell (+18.3 to +19.8‰) are close to the values for modern evaporites ( +21.5 ±0.3‰ ">‰ +21.5 ±0.3‰ ) and seawater ( +20±0.5‰ ">‰ +20±0.5‰ ) and are probably typical of seawater-derived aerosols in arid coastal environments. δ 34 -S-values slightly smaller than that for seawater may reflect a minor contribution of sulfate from pyrite oxidation in the Parilla Sand or a reservoir effect from removal of gypsum enriched in 34 S. δ 18 O SO4 -values for alunite from three Western Australia lakes (+17.8 to +18.3‰ V-SMOW), for alunite and jarosite from Lake Tyrrell (+22.6 to +24.9‰) and for aqueous sulfate from Lake Tyrrell (+17.3 to +19.0‰) are much larger than the average value for seawater (+9.6‰). The data suggest an approach to 18 O- 16 O equilibrium between aqueous sulfate and groundwater, which is known from experimental studies to be possible at low pH and low temperatures, but has not been previously documented in nature. A residence time of ∼0.1–1 kyr for sulfate in acidic water (pH 3–4) is needed to achieve the apparent partial oxygen exchange, using previously published data of R.M. Lloyd.

Chemical Geology↗
USGS1981

Chemical modifications accompanying blueschist facies metamorphism of Franciscan conglomerates, Diablo Range, California

As part of an investigation of blueschist-facies mineral parageneses in pebbles and matrix of some Franciscan metaconglomerates of the Diablo Range, California, textural and major-element chemical analyses were conducted on a number of igneous pebbles that comprise a range of rock types from granite and dacite to gabbro and basalt. Compositions of the igneous pebbles differ significantly from common igneous rocks, particularly with respect to Ca, K, Na, Si and H2O. The SiO2 and H2O contents are characteristically high and the K2O contents low. The CaO and Na2O contents may be relatively enriched or reduced in different pebbles. The igneous pebbles show little evidence of alteration prior to their incorporation into the Franciscan conglomerates, and the chemical modifications are considered to have been produced during metamorphism of the conglomerates to (lawsonite + albite + aragonite ?? jadeite)-bearing assemblages. The observed variations in the pebbles are shown to be functions of: (1) bulk chemistry; (2) the igneous mineral assemblage; (3) the stable metamorphic mineral assemblage; and (4) the composition of pore fluids in the conglomerates. The relative proportions of Mg and Fe in most of the pebbles apparently have been unaffected by the metamorphism, and these parameters, along with other textural and chemical factors, were used to determine the petrogenetic affinities of the igneous pebbles. The plutonic and most of the volcanic pebbles correspond to calc-alkaline rock series, whereas a few volcanic pebbles show apparent Fe-enrichment characteristic of tholeiitic rocks. A continental margin arc-batholith complex would be the best source for these igneous detrital assemblages. Conglomerates in local areas differ in igneous lithologies from conglomerates in other areas and probably differ somewhat in age, perhaps reflecting varying degrees of unroofing of such a complex during deposition of Franciscan sediments. ?? 1981.

Chemical Geology↗