1 10 2 https://theses.otagogeology.org.nz/files/original/95cbf4f4b48c4ccde6c525e897828b44.pdf 5345c1502aa5ec944d6d770c568e625c Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format POLYGON ((170.52696692159904 -45.403743677065485,170.531691806104988 -45.40393525163288,170.531204403806328 -45.408330714688788,170.526564903198135 -45.40811120008383,170.52696692159904 -45.403743677065485)) Author last name Last name of the Author Jones Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? BSc(Hons) Advisers Who supervised/advised this student Norris, R.J. Craw, D. Abstract The Abstract for this thesis The Golden Bar pit is part of the Macraes mine, the largest gold mine in New Zealand. The Macraes mine is mainly developed in the late metamorphic Hyde-Macraes Shear Zone. However, the Golden Bar pit was developed in a mineralised zone about 200 m structurally above the Hyde-Macraes Shear Zone. The host rocks are dominated by massive quartzofeldspathic schist (5-10 m layers) with minor intercalations (1-5 m scale) of micaceous schist. All the host schist has disseminated pyrite (micron to mm scale) from pervasive late metamorphic hydrothermal alteration. In addition, there has been more localised (metre scale) relatively intense hydrothermal alteration controlled by shears subparallel to foliation. Gold occurs in three types of mineralised rock: silicified schist, which dominates, fissile black sheared rock, and cross-cutting quartz veins. There are three principal structural zones in the deposit: (a) a strongly sheared micaceous and graphitic zone at the base of the structural sequence; (b) a weakly deformed schist zone cut by relatively flat-lying (S 20° dipping) quartz veins; and (c) a stack of imbricated schist pods and deformed silicified schist confined between two sub-parallel low-angle N (.ea: 30°) shears. These structural zones were juxtaposed during thrust deformation. The lower black shear zone has m-scale folding and overthrust packages, kink folding and foliation stacking with associated striations that imply west-directed thrusting. Striations and imbrication geometry between the upper two shears imply oblique thrusting that was directed towards the west. Post-mineralisation normal faults locally disrupt the mineralised zone. The Golden Bar pit mineralised zone has some of the structural and mineralogical characteristics of the main Hyde-Macraes Shear Zone, and may be genetically related. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Otago east Macraes Flat Thesis description Number of pages, maps, CDs, etc. vi, 84, [6] leaves : ill., maps ; 30 cm. + 3 charts. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2006Jones_P Creator An entity primarily responsible for making the resource Jones, Philip Hamish. Date A point or period of time associated with an event in the lifecycle of the resource 2006 Title A name given to the resource Structural controls on hydrothermal gold mineralisation above the Hyde-Macraes Shear Zone, Golden Bar pit, Macraes, east Otago Subject The topic of the resource Mineralogy Map Hydrothemal gold mining hydrothermal gold mineralisation https://theses.otagogeology.org.nz/files/original/a455e24de04a2298de4d14d98ec3fe8c.pdf 805f51ea48e87f47a45dc412dd196222 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format POLYGON ((170.182934818106077 -45.389221881064849,170.157422793757831 -45.311542906865732,170.346070613945045 -45.229154539997069,170.591010982684054 -45.354860871011823,170.56613887902509 -45.442453406551699,170.504897593504268 -45.500075929813775,170.182934818106077 -45.389221881064849)) Author last name Last name of the Author Teagle Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student Norris, R.J. Craw, D. Abstract The Abstract for this thesis The Hyde-Macraes Shear-zone is a structural feature, of approximately 25km length, within the Haast Schist Terrane, cropping out about 60km to the north of Dunedin. Two prospects, Nunn's at the north-western end and Golden Bar at the south-eastern end of the shear-zone, have been investigated and mapped in detail. The structure is oriented (s/d) ~070/l5°NW and ~140/20°NE at these prospects respectively. A potentially economic gold and scheelite mineralisation zone of between 5 and l00m thickness is present within the shear-zone, bounded at the top by a thrust fault that shows little relief or variation in orientation over large distances. The lower bounding fault is less planar. Where the shear-zone is thickened movement has taken place along a number of sub-parallel low-angle faults, connected by hinterland-dipping moderate to high angle imbricate faults. From observations of the structures within the shear-zone, such as asymmetric folds, the flexure of schistosity planes and mesoscopic displays of anastomosing fault planes, the evidence for the thrusting nature of the Hyde-Macraes Shear-zone is convincing. The macroscopic structure falls within the Hinterland-dipping Duplex sub-class of the Boyer and Elliot (1980) classification of thrust systems. Though duplexes are essentially compressional features, extensional sites are developed by the ramping and imbrication of the intra-shear schist along the internal inclined faults. Dilational jogs, formed at the bends and flats of these ramp faults provide optimal sites for the concentration of hydrothermal mineralisation. There are three major manifestations of mineralisation; fault related implosion breccias, caused by incremental opening at dilational jogs; grey quartz ± schist breccia veins formed at the bends and flats of ramps, and pull-apart fractures and tension gashes in which large volumes of quartz have been deposited at sites with the orientation expected for extension within a zone subjected to simple shear. High-angle, sub-vertical veins are common through-out the deposit, generally thin and cross-cutting other features, and are interpreted as being of later stage in origin. Elements (Au, W, As) previously precipitated in one of the major mineralisation sites, commonly have been remobilised within these veins. The direction of thrusting has been calculated using the orientation and vergence of mesoscopic asymmetric folds observed within the shear-zone. Estimates from within each prospect are broadly consistent and indicate that movement has been at a high angle to the strike of the shear-zone. The mode direction of movement is to the south-east (155°) at Nunn's and to the south-west (240°) at Golden Bar-Golden Ridge. If it is assumed that the Nunn's and Golden Bar prospects are part of the same macroscopic structure and were formed synchronously, a rotation of the Nunn's prospect of 60-70° about a near vertical axis is required in order to bring both the strike and the direction of movement into parallelism. Such a rotation could only be obtained by a pivoting motion on a low-angle fault plane, however there is no evidence that such a feature exists between Nunn's and Golden Bar. Phase relations within the system Gold-Arsenic-Iron-Hydrogen-Sulphur-Oxygen have been calculated thermodynamically and the influence of Temperature, Pressure, Total Dissolved Sulphur (TDS), pH and the activity of Oyxgen on gold precipitation investigated. It is proposed the gold is deposited when a solution containing both arsenic and gold encounters a reducing horizon (graphite - carbonaceous material). A small change to more reducing conditions causes a large drop in the solubility of arsenic, precipitating arsenopyrite and thus removing large amounts of sulphur from solution. The decrease in the log(TDS) results in the decrease in solubility of the Au(HS)2-complex and the precipitation of gold. The conditions of formation of mineralisation in the Hyde-Macraes Shear-zone have not been well established. From observations of the varying brittle-ductile nature of deformation in the intra-shear schist and the use of the arsenopyrite geothermometer it is suggested that the mineralisation was deposited from metamorphic fluids at a depth of 7±1km and a temperature of 310±30°C. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Hyde Macraes Flat Thesis description Number of pages, maps, CDs, etc. x. 212 p., ill. (some col)., maps (in Pocket),; 30 cm. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 1987Teagle Creator An entity primarily responsible for making the resource Teagle, DAH Date A point or period of time associated with an event in the lifecycle of the resource 1987 Title A name given to the resource Structural controls on gold mineralisation in the Hyde-Macraes Shear Zone, East Otago. Subject The topic of the resource Map Geochemistry Metal-ore deposits Structural geology gold Hyde-Macraes Shear Zone scheelite thrusting