Highway damage related to faults near Pierre, South Dakota
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Open-File Report↗
Geology topics
D. D. Eberl
Publications and source records attributed to D. D. Eberl.
Ostwald ripening and interparticle-diffraction effects for illite crystals
The Warren-Averbach method, an X-ray diffraction (XRD) method used to measure mean particle thickness and particle-thickness distribution, is used to restudy sericite from the Silverton caldera. Apparent particle-thickness distributions indicate that the clays may have undergone Ostwald ripening and that this process has modified the K-Ar ages of the samples. The mechanism of Ostwald ripening can account for many of the features found for the hydrothermal alteration of illite. Expandabilities measured by the XRD peak-position method for illite/smectites (I/S) from various locations are smaller than expandabilities measured by transmission electron microscopy (TEM) and by the Warren-Averbach (W-A) method. This disparity is interpreted as being related to the presence of nonswelling basal surfaces that form the ends of stacks of illite particles (short-stack effect), stacks that, according to the theory of interparticle diffraction, diffract as coherent X-ray scattering domains. -from Authors
American Mineralogist↗
Sericite from the Silverton caldera, Colorado: correlation among structure, composition, origin, and particle thickness.
The mineralogy and the origin of a suite of almost pure sericites, collected from fractures in hydrothermally altered volcanic rocks in the vicinity of the Silverton caldera in the western San Juan Mountains of Colorado, USA, are analysed.-J.A.Z.
American Mineralogist↗
Controlled and renewable release of phosphorous in soils from mixtures of phosphate rock and NH4-exchanged clinoptilolite
A controlled and renewable release fertilization system is proposed that employs NH4 saturated clinoptilolite to aid in the dissolution of phosphate rock (apatite), and thereby to release soluble N, P, and exchangeable Ca for uptake by plants. The system is based on the principle that exchangers can sequester Ca ions released by the dissolution of apatite, thereby leading to further dissolution of the apatite. Experiments show that the quantity of P released by this method is an order of magnitude more than that released by apatite alone. This system offers an alternative technology to the acidulation of phosphate rock, and may circumvent problems associated with highly soluble fertilizers.
Zeolites↗
Dissolution of alkaline earth sulfates in the presence of montmorillonite
In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and 226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that 226Ra from H2SO4-circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.
Water, Air, & Soil Pollution↗
Clay mineral formation and transformation in rocks and soils
Three mechanisms for clay mineral formation (inheritance, neoformation, and transformation) operating in three geological environments (weathering, sedimentary, and diagenetic-hydrothermal) yield nine possibilities for the origin of clay minerals in nature. Several of these possibilities are discussed in terms of the rock cycle. The mineralogy of clays neoformed in the weathering environment is a function of solution chemistry, with the most dilute solutions favoring formation of the least soluble clays. After erosion and transportation, these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size. Clays undergo little reaction in the ocean, except for ion exchange and the neoformation of smectite; therefore, most clays found on the ocean floor are inherited from adjacent continents. Upon burial and heating, however, dioctahedral smectite reacts in the diagenetic environment to yield mixed-layer illite-smectite, and finally illite. With uplift and weathering, the cycle begins again. Refs.
Philosophical Transactions of the Royal Society A:↗
Mineral paragenesis in the talc-water experimental hydrothermal system.
The talc-like gel was treated between 300o and 550oC at 1 kbar for 7, 30, 50, 120 and 200 days. The trends suggest that stevensite and/or corrensite are the stable minerals at <450oC. At 500o- 550oC, talc is stable.-K.A.R.
American Mineralogist↗