title: Subsurface andesite geology and hydrothermal alteration at an exploration prospect north of Waihi

authors: Starzynski, William Christopher Roman

subjects: Andesite

abstract: The Coromandel Volcanic Zone hosts the Hauraki Goldfield in the North Island of New Zealand. The goldfield consists of approximately 50 low sulphidation Au-Ag deposits. Situated in Coromandel Group rocks, which host 95% of the gold production in the region, the area of focus of this study is a prospect located 4 km north of the world class Martha Hill Mine. Such epithermal deposits are characterised by zones of altered rock called halos. Seven angled exploratory drill holes from the area were examined in this study. These cores were logged using high resolution photographs from a geological perspective for the first time. Samples were taken for petrographic and mineralogical analysis including X-ray diffraction analysis and for X-ray fluorescence spectroscopy. Leapfrog was used to display the spatial relationship of these results. The aim of this study was to determine the volcanic geology and alteration origins of this project. This was achieved by identifying facies as well as their spatial distribution, determining the mineralogical properties of the facies and their variations down-hole, as well as identifying the style and spatial extent of alteration.
Eight new facies were identified which are hosted in andesitic rock. Three of the facies were based on visible crystal concentration which ranged from, 3% – 65% and occurred throughout the core. Fresh samples were dominated by plagioclase, with relatively minor amounts of quartz and pyroxenes and altered samples comprised of calcite+quartz assemblages with various suits of sulfides and oxides, predominantly pyrite and magnetite. The mineral assemblages and their abundances are comparable to the Waipupu Formation andesite with vast similarities to active andesite volcanoes and Late Archean examples. The rocks exhibit seriate porphyritic textures and glomeroporphyritic clots that are consistent with polybaric fractionation. The textures resulted in the host rocks innate high porosity and permeability which increases with each propagation of hydrothermal fluid. While the common resorption of quartz indicates magma mingling occurring in the magma chamber, these same resorption features as well as observed swallowtail plagioclase microlites also reflect degassing processes within the magma during ascent. Four breccia facies were described based on the concentration and orientation of breccia clasts. These facies occurred dominantly around the edge of alteration zones, which can be attributed to their relatively higher porosity. While some breccia display properties of auto breccia, hydrothermal breccia’s are dominant with all breccia likely altered to some degree. Finally, an irregular facies was described and relates to hydrothermal alteration processes exclusive to moderate and high alteration zones. Using the mineralogy data, in conjunction with stratigraphic logs, zones of alteration could be identified and designated based on intensity, describing two zones of high intensity alteration separated by a zone of moderate alteration and low alteration occurring closer to the surface. These zones give an insight into the flow of paleo fluid during alteration and can hint at the location of Au bearing veins.

text: Subsurface andesite geology and hydrothermal alteration at an exploration prospect north of Waihi The Coromandel Volcanic Zone hosts the Hauraki Goldfield in the North Island of New Zealand. The goldfield consists of approximately 50 low sulphidation Au-Ag deposits. Situated in Coromandel Group rocks, which host 95% of the gold production in the region, the area of focus of this study is a prospect located 4 km north of the world class Martha Hill Mine. Such epithermal deposits are characterised by zones of altered rock called halos. Seven angled exploratory drill holes from the area were examined in this study. These cores were logged using high resolution photographs from a geological perspective for the first time. Samples were taken for petrographic and mineralogical analysis including X-ray diffraction analysis and for X-ray fluorescence spectroscopy. Leapfrog was used to display the spatial relationship of these results. The aim of this study was to determine the volcanic geology and alteration origins of this project. This was achieved by identifying facies as well as their spatial distribution, determining the mineralogical properties of the facies and their variations down-hole, as well as identifying the style and spatial extent of alteration.
Eight new facies were identified which are hosted in andesitic rock. Three of the facies were based on visible crystal concentration which ranged from, 3% – 65% and occurred throughout the core. Fresh samples were dominated by plagioclase, with relatively minor amounts of quartz and pyroxenes and altered samples comprised of calcite+quartz assemblages with various suits of sulfides and oxides, predominantly pyrite and magnetite. The mineral assemblages and their abundances are comparable to the Waipupu Formation andesite with vast similarities to active andesite volcanoes and Late Archean examples. The rocks exhibit seriate porphyritic textures and glomeroporphyritic clots that are consistent with polybaric fractionation. The textures resulted in the host rocks innate high porosity and permeability which increases with each propagation of hydrothermal fluid. While the common resorption of quartz indicates magma mingling occurring in the magma chamber, these same resorption features as well as observed swallowtail plagioclase microlites also reflect degassing processes within the magma during ascent. Four breccia facies were described based on the concentration and orientation of breccia clasts. These facies occurred dominantly around the edge of alteration zones, which can be attributed to their relatively higher porosity. While some breccia display properties of auto breccia, hydrothermal breccia’s are dominant with all breccia likely altered to some degree. Finally, an irregular facies was described and relates to hydrothermal alteration processes exclusive to moderate and high alteration zones. Using the mineralogy data, in conjunction with stratigraphic logs, zones of alteration could be identified and designated based on intensity, describing two zones of high intensity alteration separated by a zone of moderate alteration and low alteration occurring closer to the surface. These zones give an insight into the flow of paleo fluid during alteration and can hint at the location of Au bearing veins.

year: 2022

title: Structural and biochemical characterisation of O-acetylserine  sulphydrylase (CysK) from Neisseria gonorrhoeae

authors: McGarvie, Jack

subjects: Biochemistry

abstract: Neisseria gonorrhoeae is the causative bacteria of the sexually transmitted infection (STI), gonorrhoea. Rapid emergence of antibiotic resistant strains of N. gonorrhoeae has given rise to almost untreatable gonorrhoea over the last few decades. There is an urgent need for development of new antimicrobial treatments for gonorrhoea infection. Synthesis of the amino acid cysteine is a promising new target for the development of new antimicrobials. Cysteine plays a vital role in protein folding and function, and synthesis of glutathione for protection against oxidative stress during infection. 
The final step of the two-step cysteine biosynthesis pathway is catalysed by the enzyme O-acetylserine sulphydrylase (OASS). Most bacteria have two isoforms of OASS, OASS-A/CysK that utilises sulphide and O-acetylserine for the synthesis of cysteine and OASS-B/CysM that utilises thiosulphate. N. gonorrhoeae has just one OASS isoform (annotated as CysK) in its genome. N. gonorrhoeae displays unique differences in its sulphate acquisition pathway for cysteine biosynthesis, yet little is known about these pathways in N. gonorrhoeae. We propose CysK is a potential antimicrobial target. This 
thesis biochemically characterises the structure and function of CysK to determine its role in cysteine biosynthesis. Kinetic characterisation demonstrates that CysK has O-acetylserine sulphydrylase activity and displays positive cooperativity with respect to substrates, O-acetylserine and sulphide. Sulphide shows partial allosteric inhibition, and the enzyme does not use thiosulphate as a substrate. The structure of CysK was solved to 2.49 Å by X-ray crystallography and shows CysK belongs to the tryptophan synthase β superfamily and adopts a homodimeric structure consisting of two monomers. The structure supports positive cooperativity as co-factor binding residues are in inactive and active conformations in each monomer of the dimer, respectively. Many CysK enzymes form complexes with the first enzyme in the two-step cysteine synthesis pathway, CysE. It appears CysE and CysK from N. gonorrhoeae are unable to form a complex, indicating an alternate pathway for regulation of sulphur flux and cysteine production. Attempts to investigate the in vivo role of CysK were inconclusive.
The research presented in this thesis represents a major leap in our understanding of the  uncharacterised cysteine biosynthesis pathway in N. gonorrhoeae. Data presented here is the basis for future work using the kinetics and structure of CysK to guide computational inhibitor design, to identify lead compounds for CysK inhibition, and thereby development of new antimicrobials for treatment of extensively drug resistant gonorrhoea.

text: Structural and biochemical characterisation of O-acetylserine  sulphydrylase (CysK) from Neisseria gonorrhoeae Neisseria gonorrhoeae is the causative bacteria of the sexually transmitted infection (STI), gonorrhoea. Rapid emergence of antibiotic resistant strains of N. gonorrhoeae has given rise to almost untreatable gonorrhoea over the last few decades. There is an urgent need for development of new antimicrobial treatments for gonorrhoea infection. Synthesis of the amino acid cysteine is a promising new target for the development of new antimicrobials. Cysteine plays a vital role in protein folding and function, and synthesis of glutathione for protection against oxidative stress during infection. 
The final step of the two-step cysteine biosynthesis pathway is catalysed by the enzyme O-acetylserine sulphydrylase (OASS). Most bacteria have two isoforms of OASS, OASS-A/CysK that utilises sulphide and O-acetylserine for the synthesis of cysteine and OASS-B/CysM that utilises thiosulphate. N. gonorrhoeae has just one OASS isoform (annotated as CysK) in its genome. N. gonorrhoeae displays unique differences in its sulphate acquisition pathway for cysteine biosynthesis, yet little is known about these pathways in N. gonorrhoeae. We propose CysK is a potential antimicrobial target. This 
thesis biochemically characterises the structure and function of CysK to determine its role in cysteine biosynthesis. Kinetic characterisation demonstrates that CysK has O-acetylserine sulphydrylase activity and displays positive cooperativity with respect to substrates, O-acetylserine and sulphide. Sulphide shows partial allosteric inhibition, and the enzyme does not use thiosulphate as a substrate. The structure of CysK was solved to 2.49 Å by X-ray crystallography and shows CysK belongs to the tryptophan synthase β superfamily and adopts a homodimeric structure consisting of two monomers. The structure supports positive cooperativity as co-factor binding residues are in inactive and active conformations in each monomer of the dimer, respectively. Many CysK enzymes form complexes with the first enzyme in the two-step cysteine synthesis pathway, CysE. It appears CysE and CysK from N. gonorrhoeae are unable to form a complex, indicating an alternate pathway for regulation of sulphur flux and cysteine production. Attempts to investigate the in vivo role of CysK were inconclusive.
The research presented in this thesis represents a major leap in our understanding of the  uncharacterised cysteine biosynthesis pathway in N. gonorrhoeae. Data presented here is the basis for future work using the kinetics and structure of CysK to guide computational inhibitor design, to identify lead compounds for CysK inhibition, and thereby development of new antimicrobials for treatment of extensively drug resistant gonorrhoea.

year: 2021

title: HIEMPA: Hybrid Instruments from Electroacoustic Manipulation and Models of Pütorino and Aquascape

authors: Whalley, Ian

subjects: music

abstract: The HIEMPA project combined a team of people with technical, artistic, environmental and cultural expertise towards an artistic outcome aiming to extend the New Zealand sonic art tradition. The work involved collecting audio samples from the aquascape of the Ruakuri Caves and Nature Reserve in Waitomo, South Waikato, New Zealand; and samples of a variety of pütorino – a New Zealand Mäori wind instrument. Following a machine learning analysis of this audio material and an analysis of the performance material, hybrid digital instruments were built and mapped to suitable hardware triggers. The new instruments are playable in realtime, along with the electroacoustic manipulation of pütorino performances. The project takes into account the environmental and cultural significance of the source material, with the results to be released as a set of compositions. This paper discusses the background research and process of the project.

text: HIEMPA: Hybrid Instruments from Electroacoustic Manipulation and Models of Pütorino and Aquascape The HIEMPA project combined a team of people with technical, artistic, environmental and cultural expertise towards an artistic outcome aiming to extend the New Zealand sonic art tradition. The work involved collecting audio samples from the aquascape of the Ruakuri Caves and Nature Reserve in Waitomo, South Waikato, New Zealand; and samples of a variety of pütorino – a New Zealand Mäori wind instrument. Following a machine learning analysis of this audio material and an analysis of the performance material, hybrid digital instruments were built and mapped to suitable hardware triggers. The new instruments are playable in realtime, along with the electroacoustic manipulation of pütorino performances. The project takes into account the environmental and cultural significance of the source material, with the results to be released as a set of compositions. This paper discusses the background research and process of the project.

year: 2008