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Hydrothermal gold mineralization occurs in banded iron formation and amphibolite host rocks, respectively, in the Main Hill and Zakanaka deposits in the northern sector of the Pilgangoora greenstone belt of the Pilbara Craton. The supracrustal sequences of the greenstone belt have been folded into NS trending, megascale isoclinal F2A folds, which have been refolded into open to tight F2B folds. D2 to D3 strike-slip shear zones developed preferentially along the limbs of F2A isoclinal folds and along the granitoid-greenstone belt contact. Gold mineralization is controlled by F2B folds and shear zones were interpreted to have been activated or reactivated during D2B deformation in both deposits. Gold associated hydrothermal alteration comprises zoned quartz-calc silicate veins and pyrrhotite-pyrite at the Zakanaka deposit and quartz-amphibole-biotite±diopside and pyrrhotite-lollingite-arsenopyrite at the Main Hill deposit. Thermobarometric and textural studies indicate that gold mineralization occurred synchronous with the peak of amphibolite-facies metamorphism in both deposits. Lead isotope studies on gold-associated hydrothermal microcline, titanite and pyrrhotite in the Zakanaka deposit yield a PbPb isochron with an age of 2888.2±6.1 Ma for the alteration and, hence, gold mineralization. This age is confirmed by a concordant PbPb age using SHRIMP on hydrothermal titanite from the Zakanaka deposit of 2904 ± 70 Ma. The initial isotopic ratio in the ore system, estimated using the isotopic composition of hydrothermal microcline, is much more primitive than 2888 Ma Pb from accepted growth curves. Lead-isotope modeling using the possible ages of rock formation and metamorphic events in the eastern Pilbara Craton shows that the primitive Pb isotope signature is consistent with the 2888 Ma age of alteration, if the Pb was derived from old crust which underwent an early high-grade depletion event. The age of hydrothermal, gold-associated alteration at Zakanaka indirectly constrains the age of the F2B folding event and the peak of amphibolite-facies metamorphism in the Pilgangoora greenstone belt to ca. 2.89 Ga. The special position of the Pilgangoora greenstone belt in the central Pilbara, permits the interpretation of the age of gold mineralization in the light of the tectonic evolution in both parts of the craton, and indicates that mineralization and the associated structural and metamorphic events post-dated the main magmatic evolution in both the east and the west Pilbara Craton, but coincided with late deformational events along strike-slip shear zones in the west Pilbara and late syn- to post-tectonic granitoids and associated metamorphism in the east Pilbara.

Petrophysical properties (magnetic susceptibility, density) and gravity data are presented from greenstone belts of the Yilgarn Craton which have been subjected to greenschist and amphibolite facie...

Publisher Summary This chapter discusses about organization for safety. There needs to be an understanding and recognition of the informal structures and relationships that occur within the more formal imposed organization structure, informal arrangements that very often “oil the wheels” of industry and keep the organization running against all apparent odds. Many organizations have formal structures, determined rationally by the senior executives, and often displayed as charts or “organograms” showing the functions that are considered essential for the effective and smooth running of the organization. Equally important but very rarely committed to paper are the informal working groups established socially by members within the organization. Power has been described as the capacity to influence others to do that which they would not have done voluntarily and is defined by C. Wright Mills as “the capacity to make and carry out decisions even if other people resist.” Power can derive from authority vested in a person by the organization, the control of a desired product, such as money, or by virtue of special knowledge or expertise.

Publisher Summary This chapter discusses about engineering science. Everything that one uses in one's work and daily life is made up of chemical substances, by themselves or in combination of one sort or another. Each substance consists of elements that are the smallest part of matter that can exist by itself. In its free state, an element comprises one or more atoms. In some compounds, one or more of the bonds joining the atoms are the result of an unequal sharing of electrons between the two atoms and these produce ionic compounds that are crystalline solids, usually with a high melting point. They are often soluble in water giving a solution that conducts electricity. Many other compounds have bonds based on an equal sharing of electrons and therefore, they do not ionize. These compounds can be solids having low melting points, or liquids or gases. Usually they are not soluble in water unless they react with it.

Publisher Summary This chapter discusses about employers obligation for safety. As the safety legislation was being developed in the mid and late 19th century, the onus for preventing accidents and looking after oneself rested with the individual worker. Gradually it became apparent that the worker had little control over the conditions under which he worked and often was not trained in anything other than the immediate skills needed to operate the machinery. Health and Safety at Work (HSW) also requires the employer to make arrangements for the safe use, handling, and storage of substances and equipment. The detailed requirements in respect of certain substances are contained in regulations such as highly flammable liquid (HFL) and Control Of Substances Hazardous To Health (COSHH) Regulations 1988. Safe storage of substances relates not only to the physical arrangements such as racking, but also to possible chemical reactions between adjacently stored substances. A number of serious warehouse fires reinforce this requirement.

Publisher Summary This chapter discusses about industrial relation law. The Employment Protection Act 1978 has superseded the major part of the 1975 Act although many of the requirements of the latter Act have been incorporated in the 1978 Act. Within 13 weeks of commencing employment, the employer is required to give to the employee a written statement of his conditions of employment that must contain certain prescribed information. Copies of additional information relating to local working rules may also be included. The employee is also entitled to know of any disciplinary rules that might apply to him and to whom he can appeal if he is aggrieved. The Employment Act 1980 modifies the previous Acts in respect to closed shop rights of unions and also deals with rights to maternity pay and in the event of unfair dismissals. One of the main considerations of a tribunal in reaching its decision has been whether, in all the circumstances, the action the employer took was reasonable.

The three-dimensional geometry of greenstone belts in Africa and Canada is reasonably well constrained by gravity, geoelectric and seismic reflection data. A comparison of greenstone belts throughout the world shows that their overall geometries are everywhere similar. They are typically about 5 km thick and have relatively flat bases. The magnitude and direction of the dip of their contacts with surrounding granitoid rocks is variable, probably owing to local differences in their tectonic histories. The greenstones are sometimes intruded by sheet-like granitoid bodies. Thicker granitoid intrusions which form basement ridges are also recognised. Fewer geophysical studies are available from Western Australian greenstone belts. However, gravity data show that in some cases the granitoid?greenstone contact dips at a shallow angle away from the greenstone belt. There is also evidence that some of the granitoids are sheet-like. These observations carry the implication that mineralised greenstones may be present in the sub-surface below areas of granitoid outcrop. Evidence from the Murchison Greenstone Belt in South Africa, and from the Eastern Goldfields, suggests that a spatial correlation exists between mineralisation and concealed granitoid bodies. As the latter granitoids may be revealed as gravity 'lows', regional gravity surveys may be a useful first-order exploration tool within greenstone belts.

We use a set of analytical techniques for fluid inclusion analysis to determine the bulk properties of the ore fluids from five orogenic gold deposits. The most common ore fluid is a low salinity (0.4-6.5 wt% NaCl) two- to three-phase aqueous-carbonic fluid. Its Th(total) range is 200-400 °C, and total homogenization occurs by bubble or liquid disappearance. A less common aqueous fluid of similar bulk salinity and Th(total) is also documented. Microchemical data show that the ore fluid in the five deposits is chemically uniform and made of Na, subordinateK and B and minor to trace amounts of Cu, As, Li, Sr, Rb, Ba, Cs, Sb and Au (range 0.5-5 μg/g). Thermodynamic modelling carried out for one of the studied deposits indicates that the ore fluid was in equilibrium with vein minerals at the time of gold deposition, and that its vapour phase was distinctly enriched in Au, B, As and Sb. The proposed mechanism of gold precipitation is a combination of fluid decompression and boiling. Combining these results with 3D geometrical reconstructions of one of the studied deposits (Sigma), we estimate that a minimum ore fluid volume of c. 0.1-1.0 km3 is sufficient to generate a world-class orogenic deposit.