1 10 2 https://theses.otagogeology.org.nz/files/original/8d67f50f02de365aa98b130dd7aa9fd8.pdf 162e7c43bf18e60349c0510b50ed69b4 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 ((172.720715606122013 -41.0531463765194,172.819863327854279 -41.052890961980104,172.815562664355696 -41.092751433143683,172.716554001543926 -41.093154460720861,172.720715606122013 -41.0531463765194)) Author last name Last name of the Author Phillips Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student Craw, D. Abstract The Abstract for this thesis Gold mineralisation at Sams Creek occurs within an under-explored region with a rich history of alluvial gold prospecting dating back to at least the 1850s. Gold at Sams Creek is structurally hosted by sheeted veins and irregular fractures in an A-type peralkaline microgranite dike which extends 7km along strike and is up to 60 meters in thickness. The deposit was first discovered by CRA Exploration and was then further explored by OceanaGold, currently in a joint venture with MOD Resources. The majority of exploration has been conducted in the “Main Zone” including over 120 diamond drill holes. At least three stages of hydrothermal activity have altered the dike including the precipitation of late arsenopyrite veins, and lesser amounts of pyrite, sphalerite, galena, and gold. Scanning Electron Microscopy (SEM) is used to show that gold occurs as an alloy with silver (~80-85% Au) as small growths (up to 40 μm) with pyrite and base metal sulphides. These phases are primarily found cementing and in-filling fractured and brecciated arsenopyrite (the most abundant “ore mineral”). A reduced assemblage characterises the unaltered peralkaline microgranite dike which undergoes its first alteration (T1) under relatively oxidizing and ductile conditions during a late magmatic stage. Later, structurally controlled vein-related alterations (T2, T3, & T4), tied to regional deformation, occur under reduced and brittle conditions. Microstructural deformation during these stages is primarily characterised by a combination of extensional and shear related features. This study isolates geochemical enrichments related to specific alteration and vein assemblages from analysis of a targeted, independent sample set collected for this research. Using exploration generated assays, from 1 m half-core sampling a kilometre of vertical relief, this study also defines spatial distributions and variations in geochemical signatures throughout the deposit scale. A Au-As-Sb assemblage is anomalous over the full scale of the deposit, and zoning patterns of Ag, Pb, and Zn are observed throughout the full range of elevations sampled. Most notably, Ag increases with elevation, while Pb and Zn increase with depth. Mo is also relatively elevated at depth. Hydrothermal zircons first reported by Nazimova (2012) occur as clusters and stringers of <1-15μm anhedral crystals along grain boundaries of arsenopyrite and within the same micro fractures which gold grains occupy. These zircon are interpreted as forming from hydrothermally dissolved and reprecipitated zirconium present in the unaltered Sams Creek Dike. Zircons also occur in un-mineralised samples as larger ellipsoidal to faceted individual grains associated with primary mafic minerals and are interpreted as magmatic in origin. These zircons are up to ~25μm in size and many grains exhibit a spongy dissolution(?) texture. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/5119">http://hdl.handle.net/10523/5119</a> OURArchvive access level Abstract Only Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Sams CreeK NW Nelson Thesis description Number of pages, maps, CDs, etc. xiv, 177 pages A4 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 2014Phillips Creator An entity primarily responsible for making the resource Phillips, Markham Date A point or period of time associated with an event in the lifecycle of the resource 2014 Title A name given to the resource Geochemistry & Timing, Sams Creek Gold Deposit NW Nelson, New Zealand Subject The topic of the resource Geochemistry Exploration Geology exploration geochemistry Geology gold Hydrothermal Zircon Northwest Nelson Sams Creek U-Pb Dating https://theses.otagogeology.org.nz/files/original/7e3bdda9ec41499426abfffc0d46d605.pdf 7f664ad93ccb7c9438adab53e173d97d 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 Author last name Last name of the Author Windle Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student Craw, D. Abstract The Abstract for this thesis Gold mineralization is hosted by a peralkaline granite dyke which outcrops over about eight kilometers in the area of Sams Creek, a tributary of the Takaka River, north-west Nelson. The granite is riebeckite and acmite bearing, with antiperthitic alkali feldspars; it has A-type chemistry, implying an origin by partial melting at a temperature > 800°C. Associated with the granite is a suite of lamprophyre dykes; now highly altered, they probably range from original camptonites to quartz - bearing calc-alkaline types. A quartz- bearing lamprophyre has intruded along the footwall contact of the granite over much of the observed outcrop length; it may have been a source rock for gold. Granite intrusion is inferred to have occurred before or during the D2 deformation in the surrounding shales and quartzites, suggesting a minimum age of 400Ma. Deformation involving E-W compression has caused the granite to break into essentially rigid pieces, of the order of 50 m in size, surrounded by ductilely deforming sediments. Strain has been concentrated into the footwall lamprophyre, which has also served as a conduit for hydrothermal fluids. Locally, small brittle- ductile shear zones occur within the granite; some of them post - date the mineralization. Tectonic imbrication of the granite and the development of fracture permeability have probably controlled the locus of gold mineralization. Two styles of hydrothermal alteration are observed: in Main Zone, hydrolysis of riebeckite produced the assemblage magnetite+ siderite; an influx of Fe, As, Sand associated Au then produced the assemblage quartz + albite + K-feldspar + pyrite + arsenopyrite. Gold is present as the native element, poikilitically enclosed by arsenopyrite. In the western part of the area, iron has been lost during the early stages of alteration to produce the assemblage quartz - albite - K-feldspar; with further reaction, feldspars alter to sericite, and pyrite and arsenopyrite are deposited. Gold values are lower than in Main Zone. The mineralizing fluids are inferred to have been metamorphic in origin. Geothermometry based on the assemblage arsenopyrite - pyrite - sphalerite suggests a temperature of 370±50°C for Main Zone. Fluid inclusions in the western part of the area show evidence of immiscibility between H2O and CO2 ; their homogenization temperature directly yields an estimate of 260 ± 25°C for the hydrothermal fluid. Water-bearing inclusions from Main Zone, taken in conjunction with the arsenopyrite - sphalerite geothermometer, suggest a pressure of between one and two kilobars for the mineralization. In Main Zone, progressive hydrolysis of granite was accompanied by falling aO2 , which resulted in the precipitation of arsenopyrite; this in turn caused a localized fall in total dissolved sulphur which caused gold to coprecipitate. The fluid pH was ~ 9. Further west, in the sericitically altered zone, the fluid pH was buffered to between 5 and 5.4 by the alteration of K-feldspar to sericite. The lower pH has been critical in limiting gold mineralization in the western part of the area. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Sam's Creek Upper Takaka Thesis description Number of pages, maps, CDs, etc. vi. 93 leaves. Ill. Map inside back cover folded. 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 1989Windle Creator An entity primarily responsible for making the resource Windle, S Date A point or period of time associated with an event in the lifecycle of the resource 1989 Title A name given to the resource The Nature and origin of gold mineralisation at Sams Creek, North-west Nelson. Subject The topic of the resource Metal-ore deposits Igneous petrology Sams Creek Takaka River Tasman Region