Ward Chesworth

The weathering of basalt and relative mobilities of the major elements at Belbex, France

Abstract A basalt and its weathered profile have been analysed for major elements. Graphical examination shows Al. Fe and Ti to have been essentially immobile. Determining mobility sequences for this deposit is complicated by the long pedogenetic history of the area. Three different sequences are presented, two for different stages of weathering integrated over time, and one that reflects the weathering regime of the present day.

The parent rock effect in the genesis of soil

Abstract Weathering trends emanating from the compositional field of the common igneous rocks, can be shown graphically to converge on compositions relatively rich in SiO2, Al2O3 and Fe2O3. This convergence means that in chemical terms, the effect of the composition of igneous parent rock on the composition of the resulting soil, is an inverse function of time. Given enough time the chemical effect of parent rock would be nullified. The consequences of this to “state factor equations” are indicated.

The Stability of Gibbsite and Boehmite at the Surface of the Earth

Two mutually exclusive views exist concerning the relative stabilities of gibbsite and boehmite in soils. These are examined in terms of experimental and thermodynamic evidence and it is shown that all three possible divariant assemblages of two phases that can exist between gibbsite, beohmite and H2O, may do so at 25°C and 1 atmosphere total pressure depending on the status of H2O. It is further shown that the conditions of H2O chemical potential needed to stabilize boehmite + H2O relative to gibbsite + H2O or gibbsite + boehmite, are unlikely to occur in natural waters in the zone of weathering.RésuméDeux conceptions s’excluant mutuellement existent à propos de la stabilité relative de la gibbsite et de la boehmite dans les sols. Elles sont examinées sur la base de données expérimentales et thermodynamiques et l’on montre que chacune des trois combinaisons divariantes possibles entre deux phases, susceptibles d’exister entre la gibbsite, la hoehmite et l’eau, peuvent effectivement se rencontrer à 25°C et 1 atmosphère de pression totale, selon l’état de H2O. On montre en outre que les conditions de potentiel chimique de H2O nécessaires pour stabiliser boehmite + H2O par rapport à gibbsite + H2O ou gibbsite + boehmite ont peu de chance d’être satisfaites dans les eaux naturelles de la zone d’altération.KurzreferatEs bestehen zwei sich gegenseitig ausschliessende Ansichten über die relativen Beständigkeiten von Gibbsit und Boehmit in Böden. Diese werden auf Grund von experimentellem und thermodynamischem Beweismaterial untersucht und es wird dargelegt, dass alle drei möglichen, divarianten Zusammenstellungen von zwei Phasen die zwischen Gibbsit, Boehmit und Wasser bestehen können, bei 25°C und 1 Atmosphäre Gesamtdruck vorhanden sein können und zwar je nach dem Status des H2O. Es wird ferner gezeigt, dass die für die Stabilisierung von Boehmit + H2O im Verhältnis zu Gibbsit + H2O oder Gibbsit + Boehmit erforderlichen Bedingungen des chemischem Potentials von H2O kaum in natürlichen Wässern in der Verwitterungszone vorhanden sein werden.РезюмеСуществуют два взаимоисключающих взгляда об относительной устойчивости гиббсита и бемита в почве. Этот вопрос рассматривался в свете экспериментальных и термодинамических показаний и стало видно, что все три возможные диварианты группы двух фаз, которые могут существовать между гиббситом, бемитом и Н2O могут быть устойчивыми при 25°С и общем атмосферном давлении 1 в зависимости от состояния Н2O. Добавочно заметили, что состояние химического потенциала Н2O требующегося для стабилизации бемита + Н2O относительно гиббсита + Н2O или гиббсита + бемита навряд ли встречается в естественных водах зон выветривания.

The amelioration of acid mine drainage by anin situ electrochemical method—I. Employing scrap iron as the sacrificial anode

Abstract The project began in an attempt to develop technology to ameliorate acid mine drainage (AMD) problems occurring at the Sherman Iron Ore Mine of Temagami, Ontario, Canada. A series of laboratory experiments were conducted to evaluate the effectiveness of an electrochemical approach to ameliorate AMD. An electrochemical cell was constructed using a block of massive sulphide-graphite rock from the mine site as the cathode, scrap iron as the sacrificial anode, and acidic leachate collected from the mine site as the electrolyte. The cell was effective at raising the pH of ≈ 41.0 L of leachate from 3.0 to a maintenance value of ≈ 5.6. This result was accompanied by a significant decrease in redox potential from > 650 to

Solubility of apatite in clay and zeolite bearing systems: Application to agriculture

Abstract The various forms of apatite release Ca+2 and P-bearing anions into solution. The generally low solubility of these phases, however, has been a drawback to the use of apatite as a direct source of nutrient P in agriculture. Apatite has for the most part been used as a raw material for the production of the more soluble phases used in conventional fertilizers. This necessitates industrial processing by such techniques as acidulation or heat treatment, processes that inevitably increase the cost of the finished product. An alternative is to introduce a cation exchanger which will take up Ca+2, inducing further breakdown of apatite to produce a high enough concentration of P-bearing anions in solution to sustain a crop. Here, we demonstrate that framework, 2:1 sheet, and fibrous sheet silicates (zeolite, vermiculite and palygorskite) when added to apatite-H2O systems, work in this way.

Soil minerals in the system Al 2 O 3 -SiO 2 -H 2 O; phase equilibrium model

Mineralogical reactions in the system Al2O3-SiO2-H2O are examined and an isothermal, isobaric cross-section of the portion of the system applicable to soil genesis, is determined. The relevance of the cross-section to soil mineralogy is discussed

The absence of 6-fold coordinated Al in jadeite melt near the jadeite liquidus

A 27Al MAS NMR study indicates that Jadeite and Jadeite glass produced on the liquidus at 1390° ± 25°C and 35 kbars had Al in two different coordinations. In the solid phase Al was 6-fold and in the glass it was 4-fold. If the glass is taken as a good model for the liquid phase, then the common assumption that the structure of precipitating crystals reflects the structure of the melt must not be automatically accepted.

Metamorphic conditions in a part of the Haliburton Highlands of Ontario

Abstract Metamorphism in the Haliburton Highlands is of Miyashiros low pressure, intermediate type. Physico-chemical conditions ranged from 3.5 to 7 kilobars total pressure and 580 to 700°C.

Agrogeology in East Africa: the Tanzania-Canada project

Abstract Fertilizer self sufficiency is a necessary prerequisite for food security in a nation. In promoting this, the role of the geologist is to find raw materials farmers can use to increase the productivity of their soils. The Tanzania-Canada agrogeology project is the first of its kind wherein geologists, soil scientist and agronomists are working together to find and test materiaks of a geological provenance, that small scale farmers can use to improve the food carrying capacity of their land.

The System SiO2-AlOOH-Fe2O3-H2O and the Kaolinitic Stage of the Goethite Facies

A 25°C, 1 atm total pressure phase diagram for the system SiO2-AlOOH-Fe2O3-H2O, is determined using the Phase Rule and Shreinemaker’s technique as in Chesworth (1974). The waterpresent assemblages so defined are equivalent to a kaolinitic stage of the goethite facies of the weathering zone. As such they constitute the ideal stable assemblages of several earth-surface deposits and the stage can therefore be used to construct models of these deposits.