A detailed petrologic study of the maximum assemblage, minimum variance pelitic units contained within The Straits Schist in western Connecticut was undertaken to provide data on the Acadian Orogeny in the northern half of the western highlands of Connecticut. The Straits Schist, contained within the Connecticut Valley synclinorium, is structurally involved in portions of both the Hartland and Gneiss Dome belts, outlining isoclinally refolded nappes plunging off the Waterbury Dome. The Straits Schist is believed to be of Silurian—Devonian age, based on proposed correlations with the Goshen and the Waits River Formations of Massachusetts and Vermont, respectively. Furthermore, the age of metamorphism is interpreted as being Acadian based on the proposed age and stratigraphy, simple metamorphic textures, and uniform grain sizes. Quantitative estimates of the pressure and temperature conditions under which the mineral assemblages of The Straits Schist equilibrated were calculated using calibrated mineral reactions and ion exchange equilibria. Temperatures range from 607° — 747°C, and pressures range from 6.4 — 8.9 kbar across the study area. Estimates of P_H₂0/P_total were obtained and range between 0.21 and 0.57. Although exchange mechanisms have not (or could not have) been determined exactly, biotite and muscovite do show deviation from ideal tri- and di-octahedral stoichiometry, up to 13.7% di-octahedral character and 2.2% tri-octahedral character, respectively. Compositional X-ray maps indicate that The Straits Schist underwent rapid cooling. Therefore, the Acadian Orogeny in western Connecticut is characterized as a high-pressure event that underwent rapid postmetamorphic uplift and cooling. / Master of Science

Thesis (M.Sc. (Soil Science)) --University of Limpopo (Turfloop campus), 2007 / The influence of parent material on physical and chemical properties of soil was studied on granite and schist derived soils on the Syferkuil Experimental Farm, situated in the Mankweng area of the Limpopo Province of South Africa. A total of 49 samples of virgin soils were collected, where granite soils constituted 26 samples and schist soils 23. The study design that was used is cross-sectional. The samples were analysed for physical and chemical properties. The physical properties of granite and schist soils were determined as percentages coarse sand, percentages medium sand, percentages fine sand, percentages very fine sand, percentages silt and percentages clay, whilst the chemical properties were determined as concentrations (cmol (+) kg-1) of Na, Mg, Ca, K ,ESP, CEC and P (mg kg-1), as well as pH. Statistical analysis of the results was performed by application of the Unpaired Student’s T Test, with the level of significance at p<0.05. The results showed that soils derived from granite had significantly higher coarse and medium sand fractions than schist soils; whereas schist soils were significantly higher in fine sand, very fine sand, silt and clay. The concentrations of Na, Ca, ESP and P, as well as CEC and pH in schist derived soils were higher than in granite derived soils although the differences were insignificant. However, significant differences occurred in K and Mg concentrations where schist derived soils had higher concentrations than granite derived soils. However, the concentrations of nutrient elements were found to be insufficient for proper production in agriculture. The sodium concentration was found to be low enough to not lead to sodic soil conditions. It was concluded that both granite and schist soils can be used for agriculture but require careful management because both soils indicated poor nutritional status.

<p> The Larder Lake Break (LLB) is one of the structures controlling the location of gold deposits in the Kirland Lake camp. This intensly carbonated and often strongly foliated zone is part of the Larder Lake Group as defined by Downs (1980). Protoliths at the LLB are problematical. Misema River is a well exposed occurrence of the LLB, showing chlorite schist, pervasively fuchsite quartz carbonate and syenite dyke material. It is divided into three sections. Section I samples indicate an ultramafic protolith as suggested by Jensen Cation plots, and the section is interpreted as komatiitic flow(s). Section II is well foliated and shows both ultramafic and calc-alkalic components which decrease and increase in intensity respectively away from the section I-section II contact. Section II is interpreted as a polymodal sediment. Section III is similar chemically and texturally to section I, and is therefore a komatiitic flow(s). The intrusion of syenite dykes into section I occurred after initial carbonatization and defonnation of the flows and associated sediments. Radiochemical neutron activation analysis shows all but one of the syenite dyke samples to contain greater than 10 ppb gold whereas the other rock types averages approximately 2 ppb. A peak content of 64 ppb occurred at a dyke contact. The high gold contents clearly originate from the syenite dykes, which also provide a heat source for a second period of carbonatization. </p> / Thesis / Bachelor of Science (BSc)

No description available.

The Franciscan Complex forms the structurally complicated, locally chaotic basement of the Northern and Central California and southwestern Oregon Coast Ranges. It is an accretionary wedge formed during the Late- Jurassic-Tertiary subduction along the west coast of North America. In northern California, the Franciscan is subdivided into three belts, the Western, Central, and Coastal belts, which show a zonation in age, metamorphic “grade”, and structural style. Franciscan mélanges are present in the Central belt, as well as the Diablo Range --a tectonic window within the structurally overlying Great Valley Group--, and the Nacimiento Block, where the study area is located. One of the best exposures of Franciscan mélange, where contact relationships between blocks and matrix can be observed, crops out along 6 km of seacliffs near San Simeon. Boudinaged blocks of graywacke, greenstone, chert, and much rarer blueschist and graphite-schist are ix dispersed in the shale matrix. Block sizes range from 10 cm to 15 m. The discovery of interlayered blueschist and graphite-schists, and the presence of lawsonite in some graphite-schists demonstrates that these two lithologies were metamorphosed together. Graphite-schist blocks in the Franciscan have not been reported prior to this study. Two main mineral assemblages were recognized among the studied 34 mafic blueschist blocks: 1) Lws + Na-amp + Pmp + Phe + Ttn + Chl recrystallized at ~5 kbar and 200-250°C, and 2) Lws + Na-amp + Pmp + Phe + Ttn + Ep + Chl, which recrystallized under slightly higher temperatures but similar pressures (300-350°C, at 5 kbar). A pre-blueschist facies metamorphic event under greenschist facies conditions is recorded by calcic cores overprinted by Na-amp rims in about half of the blocks. Sodic amphibole rims with a higher Fe3+ content probably developed due to the breakdown of epidote during a decrease in T. These mafic blueschists followed a counterclockwise P-T path. Remnants of “actinolitic rinds”, which are reaction zones formed when the blocks were in contact with serpentine, were found associated with nine of the studied mafic blueschist blocks. Such rinds were thought to be unique to better-studied Franciscan high-T blocks. Graphite-schist blocks (30 studied) contain Qtz + Phen + Ab + Gr, and are of two types. One type has relict sedimentary textures with a weak foliation defined by graphite and pressure solution seams. The other type has a compositional layering with layers containing well recrystallized quartz. Nine of these blocks also contain lawsonite within the more graphitic layers. The geochemistry of the blueschist blocks indicates that they were derived from the MORB-like oceanic crust, and seamounts underplated during the initiation of subduction. The mainly mafic protolith contained a small volume of interlayered sediment, as indicated by the presence of associated metasedimentary graphite-schists. Blueschist facies conditions were attained at the bottom of the overriding plate during the initial states of Franciscan subduction (150-155 Ma). Mafic material continued to be underplated, and low-T dynamic blueschist-facies metamorphism continued to form until at least ~137 Ma. A model is proposed in which exhumation was facilitated by normal faulting near the surface driven by gravitational collapse driven by decrease in subduction plate dip around 80 Ma that is known to have caused the Laramide orogeny. During this time, blueschist and graphite-schist blocks were plucked from the bottom of the hanging wall, incorporated into the shaleand water-rich shear zone at the plate interface, and exhumed during the upward flow of mélange driven by the movement of the downgoing plate. Blocks were extended and boudinaged, and metasomatically altered in the cataclastic zones that developed along necks and margins of the blocks during upwelling and the dewatering that led to final compaction near the surface. / text

The Saxonian Granulite Massif in the Saxothuringian Domain of the Bohemian Massif, is represented by a single granulite body consisting of felsic and mafic granulites formed during Variscan tectono-metamorphic event. The granulites with peak metamorphic P-T conditions of ~2.3 GPa and 970-1060 řC (Fuhrman and Lindsley, 1988; Rötzler and Romer, 2001) were exhumed and emplaced into the palaeozic sedimentary cover sequence, which resulted into contact metamorphism affecting these metasedimentary rocks and development of a contact metamorphic aureole. In the map view, the granulite body has elongated shape with the long axis oriented in NE- SW direction and it is surrounded by the so called schist mantle reflecting the extent of the contact metamorphic aureole. Within two kilometers distance away from the contact with granulite body, the metamorphic grade in metasediments decreases from cordierite gneiss, andalusite bearing micaschist to phyllite. Detailed field structural analysis in the studied area revealed a deformation record associated with four main deformation phases. In granulites the oldest deformation fabric contains kyanite and sillimanite. This fabric is locally overprinted by the subhorizontal green schist facies fabric, mainly along the margins of the granulite body. In metasediments, the...

Abstract At least 30 gold deposits verified by means of one or more notable diamond drill hole results have been discovered in Central Lapland in the last 20 years, and these can be divided spatially into groups, between which the metal composition varies. The deposits contain varying amounts of sulphides and sulpharsenides as well as gold. Pyrite is the most common sulphide mineral in the gold deposits associated with volcanic rocks, and usually pyrrhotite in those associated with sedimentary rocks. The principal sulphide minerals in those connected with banded iron formations are pyrite and arsenopyrite. A separate group of formations consists of the palaeoplacer gold deposits associated with the molasse-like quartzites and conglomerates of Central Lapland. The iron oxide-copper-gold deposits of Central Lapland, which are a significant potential source of copper and gold, are mostly associated with skarn rocks at the eastern contact of the acidic intrusive rocks of Western Lapland and with skarn rocks occurring as interlayers in metavolcanic and metasedimentary rocks. The gold deposits that have led to actual mining activities in Central Lapland are Saattopora in Kittilä and Pahtavaara in Sodankylä. Apart from the Laurinoja iron oxide-copper-gold ore body in Kolari, copper concentrate has been produced from the Saattopora gold ore deposit and the Pahtavuoma copper ore deposit. Only one gold ore in Central Lapland is being actively exploited at present, that of the Pahtavaara mine, which was worked in 1995–2000 and reopened in 2003. The best starting point for successful gold ore exploration in Central Lapland can be achieved through a thorough knowledge of the deformation zones and their structures and alteration processes and the application of geochemical methods. Magnetic surveys can be of help in identifying and locating deformation zones of interest for exploration purposes and the majority of the associated shear zones and faults. Ore-critical zones usually feature graphite-bearing schists and iron sulphide-bearing sequences that can be traced by electrical methods and used as marker zones to verify the results of geological mapping. Geological, geophysical and geochemical techniques have been used in great diversity, and in particular till geochemistry and bedrock drilling have been methods by which the gold and copper deposits in Central Lapland have been discovered. A total of 7.6 million tonnes of gold and copper ores, including the Laurinoja iron oxide-copper-gold ore, were extracted in Central Lapland over the period 1982–2000. The resulting production of gold during this period was 10 800 kg, together with 21 000 tonnes of copper in concentrates and 4500 kg of silver. The gold and copper ores have been concentrated by gravity separation and/or flotation, since the ores so far taken into production has been of the free milling type. However, a substantial proportion of the deposits in the area contain copper, nickel, cobalt and arsenic as well, in the form of sulphides or sulpharsenides, so that the achievement of commercially saleable products calls for the use of different leaching processes. Deposits have also been found in Central Lapland that have consisted partly or entirely of refractory gold ore in which gold is lying in the crystal lattice of pyrite and/or arsenopyrite, the processing of which by the above-mentioned methods is not economic, as it requires pre-treatment by bio-oxidation or pressure oxidation in order to convert the gold to a cyanide-soluble form.

A quartz diorite intrusion of probable early Tertiary age that crops out over at least 6 square miles in the Palo Verde Ranch area in Pinal County, Arizona was mapped as a distinct intrusion. The quartz diorite intrudes an area comprising Pinal Schist, Oracle granite, andesitic flows, granoaplite, and dike rocks including both pegmatite and diabase. Two major physical features, the Owl Head Buttes and Chief Buttes volcanic areas, both remnants of an extensive early Tertiary series of flows of intermediate composition that covered the area, now remain as lava-capped buttes above the pediment. Weak but persistent fracture-controlled copper mineralization is found in the quartz diorite and the Pinal Schist at or near their mutual contacts in the form of chrysocolla, malachite, black copper oxides, chalcocite, chalcopyrite, and bornite, in decreasing order. Pyrite is rare. Alteration related to northeast and northwest-trending fractures increases in intensity from the common propylitic to argillic to the northeast toward the San Juan claims area. A barely discernible increase in copper sulfides mirrors the alteration zoning, although geochemical sampling showed background copper in the quartz diorite to be more uniform away from fractures.