title: Temporal evolution of a high-k andesitic magmatic system: Taranaki Volcano, New Zealand

authors: Zernack, Anke V.

subjects: Taranaki/Egmont Volcano

abstract: Taranaki (Mt. Egmont) in the western North Island of New Zealand is a high-K andesite volcano with an eruptive history extending over more than 200 kyr. In general, petrological research has concentrated on the post-10 ka record of the modern edifice. This study focuses on the earlier history, which is recorded in 11 major pre-7 ka debris avalanche deposits. Each of these formed as a result of a catastrophic collapse of the edifice of the time. The clast assemblages of these deposits provide insights into the chemical compositions of magmas erupted during the earlier stages of activity of the volcano and form the basis for a new chemo-stratigraphic analysis of the pre-10 ka volcanic succession. Sample suites from the studied debris avalanche deposits show a progressive enrichment in K₂O and large ion lithophile elements (LILE), reflecting a gradual evolution to high-K andesite. The early magmatic system (pre-100 ka) produced a wide range of compositions including relatively primitive basalts and basaltic andesites. These rocks contain phenocryst assemblages that indicate crystallization within the lower crust or mantle, including a broad range of clinopyroxene compositions, high-Al₂O₃ hornblende, olivine and phlogopite. A higher proportion of high-silica compositions in the younger sample suites and the appearance of late-stage, low-pressure mineral phases, such as high-TiO₂ hornblende, biotite and Fe-rich orthopyroxene, reflect a gradual shift to more evolved magmas with time. These new data are interpreted to reflect a multi-stage origin for Taranaki andesites. Parental magmas were generated within a lower crustal ‘hot zone’, which formed as a result of repeated intrusions of primitive melts into the lower crust. The geochemical and mineralogical evidence indicates that prior to 100 ka this zone was relatively thin and cold, so that primitive magmas were able to rise rapidly through the crust without significant interaction and modification. As the hot zone evolved, larger proportions of intruded and underplated mafic material were partially remelted, and interaction of these melts with fractionating mantle-derived magmas generated progressively more K- and LILE-enriched compositions. A complex and dispersed magma assembly and storage system developed in the upper crust where the hot-zone melts were further modified by fractional crystallization and magma mixing and mingling.

text: Temporal evolution of a high-k andesitic magmatic system: Taranaki Volcano, New Zealand Taranaki (Mt. Egmont) in the western North Island of New Zealand is a high-K andesite volcano with an eruptive history extending over more than 200 kyr. In general, petrological research has concentrated on the post-10 ka record of the modern edifice. This study focuses on the earlier history, which is recorded in 11 major pre-7 ka debris avalanche deposits. Each of these formed as a result of a catastrophic collapse of the edifice of the time. The clast assemblages of these deposits provide insights into the chemical compositions of magmas erupted during the earlier stages of activity of the volcano and form the basis for a new chemo-stratigraphic analysis of the pre-10 ka volcanic succession. Sample suites from the studied debris avalanche deposits show a progressive enrichment in K₂O and large ion lithophile elements (LILE), reflecting a gradual evolution to high-K andesite. The early magmatic system (pre-100 ka) produced a wide range of compositions including relatively primitive basalts and basaltic andesites. These rocks contain phenocryst assemblages that indicate crystallization within the lower crust or mantle, including a broad range of clinopyroxene compositions, high-Al₂O₃ hornblende, olivine and phlogopite. A higher proportion of high-silica compositions in the younger sample suites and the appearance of late-stage, low-pressure mineral phases, such as high-TiO₂ hornblende, biotite and Fe-rich orthopyroxene, reflect a gradual shift to more evolved magmas with time. These new data are interpreted to reflect a multi-stage origin for Taranaki andesites. Parental magmas were generated within a lower crustal ‘hot zone’, which formed as a result of repeated intrusions of primitive melts into the lower crust. The geochemical and mineralogical evidence indicates that prior to 100 ka this zone was relatively thin and cold, so that primitive magmas were able to rise rapidly through the crust without significant interaction and modification. As the hot zone evolved, larger proportions of intruded and underplated mafic material were partially remelted, and interaction of these melts with fractionating mantle-derived magmas generated progressively more K- and LILE-enriched compositions. A complex and dispersed magma assembly and storage system developed in the upper crust where the hot-zone melts were further modified by fractional crystallization and magma mixing and mingling.

year: 2011

title: Towards cleaner fertilisers; Solution ion-exchange methods for reducing cadmium levels in reactive phosphate rock

authors: Dyche, Timothy Adam

subjects: Fertiliser

abstract: The aim of this study was to characterise reactive phosphate rock (RPR); a form of rock phosphate which can be used directly as fertiliser, and investigate the potential to reduce cadmium levels in RPR by application of calcium ion solutions derived from waste mussel shells. 

Analytical techniques including ICP-MS, XRD, XRF, SEM-EDX, and FTIR were used in the characterisation of reactive phosphate rock, as provided by Terracare. These techniques allowed for changes to both the macro and trace element composition of reactive phosphate rock to be measured and monitored as it was subjected to a calcium ion solutions and variety of chemical and physical reaction conditions, with the aim of selectively extracting cadmium ions, by ion exchange with calcium, while leaving the general structure of RPR unchanged.

The solubility of phosphate ions in RPR was tested at varying pH, the intention being to determine the pH range of solutions that could be used for cadmium extraction while minimising phosphate losses.

Calcium ion solutions were applied to reactive phosphate rock under a range of different reaction conditions. Changes to calcium ion concentration, contact time, pH, temperature, microwave irradiation, use of different counter ions and addition of potential cadmium stabilising ligands were tested for their effects on reactive phosphate rock. Promising results were observed, with elevated levels of cadmium found in many extraction solutions. Calcium chloride solution of 1 mol L⁻¹ concentration was found to be the most effective at extracting cadmium from RPR.

Mussel shells were characterised by analytical methods including ICP-MS, XRD, XRF, UV-Vis, and FTIR. The effects of heating to temperatures between 300°C and 900°C to the physical and chemical properties of mussel shells were studied. Mussel shells were used as a basis for calcium ion solutions by dissolving crushed mussel shell in mineral acids. These shell solutions were compared with solutions of pure calcium salts for their effectiveness in extracting cadmium ions. 

Overall the results of this study indicate that it is possible for significant amounts of cadmium to exchange from RPR into calcium ion solutions with comparatively small phosphate losses. It appears that mussel shells could provide a suitable source of calcium ions for this purpose. Overall indications are that cadmium extraction from RPR by ion exchange with calcium ion solutions is a concept worthy of further research. If the preliminary results prove to be accurate then further developments have the potential to contribute to improved environmental outcomes for both the fertiliser and shellfish industries in New Zealand.

text: Towards cleaner fertilisers; Solution ion-exchange methods for reducing cadmium levels in reactive phosphate rock The aim of this study was to characterise reactive phosphate rock (RPR); a form of rock phosphate which can be used directly as fertiliser, and investigate the potential to reduce cadmium levels in RPR by application of calcium ion solutions derived from waste mussel shells. 

Analytical techniques including ICP-MS, XRD, XRF, SEM-EDX, and FTIR were used in the characterisation of reactive phosphate rock, as provided by Terracare. These techniques allowed for changes to both the macro and trace element composition of reactive phosphate rock to be measured and monitored as it was subjected to a calcium ion solutions and variety of chemical and physical reaction conditions, with the aim of selectively extracting cadmium ions, by ion exchange with calcium, while leaving the general structure of RPR unchanged.

The solubility of phosphate ions in RPR was tested at varying pH, the intention being to determine the pH range of solutions that could be used for cadmium extraction while minimising phosphate losses.

Calcium ion solutions were applied to reactive phosphate rock under a range of different reaction conditions. Changes to calcium ion concentration, contact time, pH, temperature, microwave irradiation, use of different counter ions and addition of potential cadmium stabilising ligands were tested for their effects on reactive phosphate rock. Promising results were observed, with elevated levels of cadmium found in many extraction solutions. Calcium chloride solution of 1 mol L⁻¹ concentration was found to be the most effective at extracting cadmium from RPR.

Mussel shells were characterised by analytical methods including ICP-MS, XRD, XRF, UV-Vis, and FTIR. The effects of heating to temperatures between 300°C and 900°C to the physical and chemical properties of mussel shells were studied. Mussel shells were used as a basis for calcium ion solutions by dissolving crushed mussel shell in mineral acids. These shell solutions were compared with solutions of pure calcium salts for their effectiveness in extracting cadmium ions. 

Overall the results of this study indicate that it is possible for significant amounts of cadmium to exchange from RPR into calcium ion solutions with comparatively small phosphate losses. It appears that mussel shells could provide a suitable source of calcium ions for this purpose. Overall indications are that cadmium extraction from RPR by ion exchange with calcium ion solutions is a concept worthy of further research. If the preliminary results prove to be accurate then further developments have the potential to contribute to improved environmental outcomes for both the fertiliser and shellfish industries in New Zealand.

year: 2022

title: Waiwhakareke Restoration Plantings: Establishment of Monitoring Plots 2005-06

authors: Grove, E.

subjects: New Zealand

abstract: Waiwhakareke Natural Heritage Park is being developed to reconstruct native lowland and wetland ecosystems as were once widespread in the Waikato Region. The 60ha Natural Heritage Park is located on the north-west outskirts of Hamilton City and includes a peat lake (Horseshoe Lake) which is surrounded by introduced willow trees. There is some native marginal vegetation around the lake, including rushes and sedges, and an extensive area of gently sloping pasture completes the catchment. The restoration and recreation of the native plant and animal communities is being lead by the Hamilton City Council in partnership with The University of Waikato, Wintec, Nga Mana Toopu o Kirikiriroa Limited Resource Management and Cultural Consultants and Tui 2000 (McQueen 2005; McQueen & Clarkson 2003).

text: Waiwhakareke Restoration Plantings: Establishment of Monitoring Plots 2005-06 Waiwhakareke Natural Heritage Park is being developed to reconstruct native lowland and wetland ecosystems as were once widespread in the Waikato Region. The 60ha Natural Heritage Park is located on the north-west outskirts of Hamilton City and includes a peat lake (Horseshoe Lake) which is surrounded by introduced willow trees. There is some native marginal vegetation around the lake, including rushes and sedges, and an extensive area of gently sloping pasture completes the catchment. The restoration and recreation of the native plant and animal communities is being lead by the Hamilton City Council in partnership with The University of Waikato, Wintec, Nga Mana Toopu o Kirikiriroa Limited Resource Management and Cultural Consultants and Tui 2000 (McQueen 2005; McQueen & Clarkson 2003).

year: 2006