Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1930. / Cover title. "Reprinted from American mineralogist, Vol. 15, No. 9, September, 1930." eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, 1915. / "A private edition distributed by the University of Chicago libraries." "Reprinted from the Journal of geology, vol. XXIV, no. 2, February-March, Chicago, 1916."

Thesis (Ph. D.)--University of Chicago, 1915. / "A private edition distributed by the University of Chicago libraries." "Reprinted from the Journal of geology, vol. XXIV, no. 2, February-March, Chicago, 1916."

Dissolution rates of hornblende and tremolite were studied in constant pH batch experiments over the pH range 4-6, in order to understand the acid neutralizing role of hornblende in watersheds with low alkalinity. Hornblende and tremolite exhibit linear dissolution kinetics within one or two days after the onset of weathering. During the first 80-100 hours of weathering, base cations are released preferentially to silica in both minerals. During this period a leached surface layer similar in structure to the original material, but altered in composition is believed to be formed. Release rates of Si, Ca, Na, and Mg from hornblende exhibit weak fractional dependence on pH: d[Mg] /dt = k₁[H⁺] 0.13, d[Ca] /dt = k₁[H⁺] 0.065, d[Na] /dt = k₁[H⁺] 0.17, and d[Si] /dt = k₁[H⁺] 0.045. As a result, it is believed that, for large and transient influxes of acidified water, hornblende is not an important pH buffer. Because of rapid dissolution rates, however, hornblende could be an important source of acid neutralizing capacity.

The Areachap Group represents a mid-Proterozoic fossil island arc environment consisting of amphibolite, hornblende gneiss, quartz-feldspathic gneiss, calcsilicates and pelitic schists. Chemical compositions of these highly deformed upper amphibolite/granulite grade metamorphosed rocks indicate protoliths ranging from rhyolite/rhyodacite, calc-alkaline basalt, tholeiite to ultramafic igneous rocks and sediments. The above-mentioned assemblage is typical of an island arc environment. Island arc environments are ideal hosts for volcanic hosted massive sulphide (VHMS) type deposits and may successfully be explored by using the VHMS lithogeochemical alteration model. VHMS deposits not only yield strategic base metals such as zinc (Zn), copper (Cu) and lead (Pb), but significant grades of gold (Au) and silver (Ag) are associated with these deposits. The Areachap Group presents a metallogenic province containing one economic deposit, the Prieska Zn-Cu mine, as well as several sub-economic deposits, including the Areachap mine and other lesser prospects at Boksputs, Kantienpan, Jacomynspan and Rokoptel. The Prieska Zn-Cu mine is the most significant VHMS deposit of the Areachap Group and occurs within the Copperton volcanic centre. This abandoned mine delivered 47 Mt sulphide ore at 1,7 % Cu and 3,8 % Zn with traces of Ag and Au. Four volcanic centres were previously identified in the Areachap Group, namely Upington, Klein Begin, Boksputs and Copperton. Exploration activities were loosely subdivided into the same regions. Regional lithogeochemical sampling campaigns were conducted for the four subproject areas and approximately 5 000 rock samples were analysed for the twelve major oxides and ten trace elements. The region of interest, the Boksputs Subvolcanic area, with a well-established infrastructure, is situated near Groblershoop (50 km east) and Marydale (30 km southeast) in the Northern Cape province and is part of the geological Areachap Group. Several high copper anomalies and the tholeiitic lithological composition of the Boksputs Subproject resulted in this area being selected as the main target region. It was attempted to discriminate between different trace element populations using probability plots, but this was not successful. The complexity of the probability plots was attributed to the large variation in different rock types included in the data set. Corrections were made by determining threshold values for each rock type, but this refinement proved unsuccessful, indicating that the rock classification used was incorrect. Option areas were finally selected, based primarily on absolute Cu values. These areas were mapped in . more detail prior to ground electromagnetic (EM) surveys and drilling. To test the target selection, a proto-lithological map of the area, based on cluster analyses of the lithogeochemical dataset, was drawn. The proto-lithological maps formed the basis of the follow-up work and the application of the VHMS conceptual model. A conductor in the Kantienpan target area was located with a time domain electromagnetic (TDEM) survey and this was drilled. The drilling intersected a massive sulphide body with a tonnage of approximately 5 Mt and an average grade of 4.09 % Zn, 0.49 % Cu and traces of Au and Ag. The orebody was evaluated financially and it was found to be uneconomic as a stand-alone operation. However, if the Kantienpan deposit is considered as an alternative to imported concentrate for the Zincor smelter, this study suggests that the project may be economically feasible. Furthermore, it must be stated that the Areachap Group remains only partly explored and that a world class VHMS deposit may be discovered within the next few years. / Dissertation (MSc)--University of Pretoria, 2008. / Geology / unrestricted

A scapolite-hornblende-biotite schist from the Grenville province of the Canadian Shield has been analysed for Tl by an atomic absorption technique with a high sensitivity. K, Rb and some major oxides were determined by wet chemistry. Tl, K/Rb, K/Tl and Tl/Rb were compared to several other rocks and for this report were found to be 432ppb, 429, 4.85x10³ and 88.4x10⁻³ respectively. These values are similar to those quoted for other rocks. / Thesis / Bachelor of Science (BSc)

An atomic force microscope (AFM) has been used to conduct force measurements to better understand the role of hydrophobic forces in flotation. The force measurements were conducted between a flat mineral substrate and a hydrophobic glass sphere in aqueous solutions. It is assumed that the hydrophobic glass sphere may simulate the behavior of air bubbles during flotation. The results may provide information relevant to the bubble-particle interactions occurring during flotation. The glass sphere was hydrophobized by octadecyltrichlorosilane so that its water contact angle was 109 degrees. The mineral systems studied include covellite (CuS), sphalerite (ZnS) and hornblende (Ca₂(Mg, Fe)₅(Si₈O₂₂)(OH,F)₂). The collector used for all the mineral systems studied was potassium ethyl xanthate (KEX). For the covellite-xanthate system, a biopotentiostat was used in conjunction with the AFM to control the potential of the mineral surface during force measurements. This was necessary since the adsorption of xanthate is strongly dependent on the electrochemical potential (Eₕ) across the solid/liquid interface. The results show the presence of strong hydrophobic forces not accounted for by the DLVO (named after Derjaguin, Landau, Verwey and Overbeek) theory. Furthermore, the potential at which the strongest hydrophobic force was measured corresponds to the potential where the flotation recovery of covellite reaches a maximum, indicating a close relationship between the two. Direct force measurements were also conducted to study the mechanism of copper-activation of sphalerite. The force measurements conducted with unactivated sphalerite in 10⁻³ M KEX solutions did not show the presence of hydrophobic force while the results obtained with copper-activated sphalerite at pH 9.2 and 4.6 showed strong hydrophobic forces. However, at pH 6.8, no hydrophobic forces were observed, which explains why the flotation of sphalerite is depressed in the neutral pH regime. Direct force measurements were also conducted using hornblende in xanthate solutions to study the mechanism of inadvertent activation and flotation of rock minerals. The results show the presence of long-range hydrophobic forces when hornblende was activated by heavy metal cations such as Cu²⁺ and Ni²⁺ ions. The strong hydrophobic forces were observed at pHs above the precipitation pH of the activating cation. These results were confirmed by the XPS analysis of the activated hornblende samples. Force measurements were conducted between silanated silica surfaces to explore the relationship between hydrophobicity, advancing contact angle (CA), and the magnitude (K) of hydrophobic force. In general, K increases as Contact Angle increases and does so abruptly at Contact Angle=90°. At the same time, the acid-base component of the surface free energy decreases with increasing CA and K. At CA>90°, GammaS^AB approaches zero. Based on the results obtained in the present work a mathematical model for the origin of the hydrophobic force has been developed. It is based on the premise that hydrophobic force originates from the attraction between large dipoles on two opposing surfaces. The model has been used successfully to fit the measured hydrophobic forces using dipole moment as the only adjustable parameter. However, the hydrophobic forces measured at CA>90° cannot be fitted to the model, indicating that there may be an additional mechanism, possibly cavitation, contributing to the appearance of the long-range hydrophobic force. / Ph. D.

A petrographic study has been made of the contact relations between metagabbro and nepheline gneiss underlain by marble, in Monmouth township, Haliburton County, Ontario. A bad of hornblende nepheline-garnet gneiss about 80 feetwide trending north-south is underlain at a shear contact by marble. Round inclusion up to 18 inches across of red pyroxene with some spinel and rimmed by olivine occur in the marble a few feet below the contact. For a few inches above the contact the nepheline gneiss sometimes is biotite-bearing. To the east the nepheline gneiss grades into a band of hybrid nepheline metagabbro (containing pink augite) about 50 feet wide. This in turn is followed by a zone of garnetiferous clinozoisite metagabbro about 220 feet wide. Clinozoisite persists in the metagabbro for 100 feet beyond this zone and is followed by hornblende-(pyroxene)-plagioclase metagabbro. Pyroxene-garnet-(nepheline) skarn is interlayered with nepheline gneiss at one outcrop ear the fault contact with marble. It appears that gabbroic magma has intruded limestone and developed a skarn at the contact. Assimilation of lime by the magma has developed pink augite (titanaugite ?) , clinozoisite and grossularite in the gabbro. Subsequent injection of a highly fluid nepheline magma, or of solutions containing soda, alumina and iron and not saturated with silica, formed nepheline-bearing rock between marble and gabbro. Soda metasomatism produced a hybrid nepheline gabbro adjacent to the nepheline-bearirg rock. Regional metamorphism later imparted a foliation to the marble and nepheline rock, and produced a metamorphic texture the gabbro. Faulting of a unknown age brought nepheline gneiss and marble into sharp contact and probably trapped the skarn as horses only one of which is now exposed. / Thesis / Doctor of Philosophy (PhD)

New and existing U–Pb and 40Ar/39Ar geochronological data, and oxygen and hydrogen stable isotope data, are combined with structural and metamorphic data from Thor–Odin, the southern culmination of the Monashee Complex. This leads to a new interpretation of the timing of deformation and metamorphism. Amphibolites in Thor–Odin with hornblende 40Ar/39Ar dates between ~75–70 and ~51 Ma experienced more 18O- and D-depletion than amphibolites with older dates. The younger dates that were previously interpreted as cooling ages, may have resulted from complete or partial Ar loss in the presence of meteoric fluids that were introduced into the rock during extension. <br><br> Monazite crystals in pelitic schist, quartzite and orthogneiss, which have U–Pb ages younger than 40Ar/39Ar hornblende ages in amphibolite in northwest Thor–Odin, may have grown during tension in the presence of fluids. Titanite, xenotime and zircon dates may be interpreted in the same way. Thus, the U–Pb dates that were previously interpreted as representing peak of metamorphism and the hornblende 40Ar/39Ar dates that were previously interpreted as representing cooling ages, may be interpreted as reflecting meteoric fluid penetration of the crust during regional extension. This implies that the age of the thermal peak of metamorphism is older than ~75–70 Ma. Migmatisation in a basement orthogneiss in Thor–Odin occurred at ~1.8 Ga. Dissolution rims are preserved in zircon between ~1.8 Ga domains and 52 Ma overgrowths. Because growth of new zircon (and possibly other U–Pb accessory phases) did not take place, any geological event that occurred during the ~1.8 Ga to 52 Ma time interval is not recorded. Cordilleran deformation and metamorphism may have taken place within that time interval, e.g. in the Middle Jurassic and/or mid- to Late Cretaceous, the time of Cordilleran deformation and metamorphism in the rocks overlying the Monashee Complex. <br><br> The Joss Mountain orthogneiss, west of the Monashee Complex in the Selkirk Allochthon, is dated at 362 +/– 13 Ma. F3 folding in pelitic schist at Joss Mountain is constrained between ~73 and ~70 Ma. Existing structural, metamorphic and geochronological data in, and close to, the Shuswap Metamorphic Complex in the southern Canadian Cordillera are shown to be consistent with a channel flow model.

The geology of the northeastern and southwestern sections of the aureole of the Loon Lake pluton of Chandos township was mapped. Thirty five pairs of hornblende and biotite were separated from the rocks and spectrographically analyzed for Be, Ga, Ti, Cr, V, Li, Ni, Co, Cu, Mn, Zr, Sr, Ba and Rb. Major element analyses were made by wet chemical methods on 8 pairs of hornblende and biotite. The relations of minor and major elements are discussed in terms of distribution coefficients. / Thesis / Master of Science (MS)