title: Discriminating cool-water from warm-water carbonates and their diagenetic environments using element geochemistry: the Oligocene Tikorangi Formation (Taranaki Basin) and the dolomite effect

authors: Hood, Steven D.

subjects: carbonate geochemistry

abstract: Fields portrayed within bivariate element plots have been used to distinguish between carbonates formed in warm- (tropical) water and cool- (temperate) water depositional settings. Here, element concentrations (Ca, Mg, Sr, Na, Fe, and Mn) have been determined for the carbonate fraction of bulk samples from the late Oligocene Tikorangi Formation, a subsurface, mixed dolomite-calcite, cool-water limestone sequence in Taranaki Basin, New Zealand. While the occurrence of dolomite is rare in New Zealand Cenozoic carbonates, and in cool-water carbonates more generally, the dolomite in the Tikorangi carbonates is shown to have a dramatic effect on the "traditional" positioning of cool-water limestone fields within bivariate element plots. Rare undolomitised, wholly calcitic carbonate samples in the Tikorangi Formation have the following average composition: Mg 2800 ppm; Ca 319 100 ppm; Na 800 ppm; Fe 6300 ppm; Sr 2400 ppm; and Mn 300 ppm. Tikorangi Formation dolomite-rich samples (>15% dolomite) have average values of: Mg 53 400 ppm; Ca 290 400 ppm; Na 4700 ppm; Fe 28 100 ppm; Sr 5400 ppm; and Mn 500 ppm. Element-element plots for dolomite-bearing samples show elevated Mg, Na, and Sr values compared with most other low-Mg calcite New Zealand Cenozoic limestones. The increased trace element contents are directly attributable to the trace element-enriched nature of the burial-derived dolomites, termed here the "dolomite effect". Fe levels in the Tikorangi Formation carbonates far exceed both modern and ancient cool-water and warm-water analogues, while Sr values are also higher than those in modern Tasmanian cool-water carbonates, and approach modern Bahaman warm-water carbonate values. Trace element data used in conjunction with more traditional petrographic data have aided in the diagenetic interpretation of the carbonate-dominated Tikorangi sequence. The geochemical results have been particularly useful for providing more definitive evidence for deep burial dolomitisation of the deposits under the influence of marine-modified pore fluids.

text: Discriminating cool-water from warm-water carbonates and their diagenetic environments using element geochemistry: the Oligocene Tikorangi Formation (Taranaki Basin) and the dolomite effect Fields portrayed within bivariate element plots have been used to distinguish between carbonates formed in warm- (tropical) water and cool- (temperate) water depositional settings. Here, element concentrations (Ca, Mg, Sr, Na, Fe, and Mn) have been determined for the carbonate fraction of bulk samples from the late Oligocene Tikorangi Formation, a subsurface, mixed dolomite-calcite, cool-water limestone sequence in Taranaki Basin, New Zealand. While the occurrence of dolomite is rare in New Zealand Cenozoic carbonates, and in cool-water carbonates more generally, the dolomite in the Tikorangi carbonates is shown to have a dramatic effect on the "traditional" positioning of cool-water limestone fields within bivariate element plots. Rare undolomitised, wholly calcitic carbonate samples in the Tikorangi Formation have the following average composition: Mg 2800 ppm; Ca 319 100 ppm; Na 800 ppm; Fe 6300 ppm; Sr 2400 ppm; and Mn 300 ppm. Tikorangi Formation dolomite-rich samples (>15% dolomite) have average values of: Mg 53 400 ppm; Ca 290 400 ppm; Na 4700 ppm; Fe 28 100 ppm; Sr 5400 ppm; and Mn 500 ppm. Element-element plots for dolomite-bearing samples show elevated Mg, Na, and Sr values compared with most other low-Mg calcite New Zealand Cenozoic limestones. The increased trace element contents are directly attributable to the trace element-enriched nature of the burial-derived dolomites, termed here the "dolomite effect". Fe levels in the Tikorangi Formation carbonates far exceed both modern and ancient cool-water and warm-water analogues, while Sr values are also higher than those in modern Tasmanian cool-water carbonates, and approach modern Bahaman warm-water carbonate values. Trace element data used in conjunction with more traditional petrographic data have aided in the diagenetic interpretation of the carbonate-dominated Tikorangi sequence. The geochemical results have been particularly useful for providing more definitive evidence for deep burial dolomitisation of the deposits under the influence of marine-modified pore fluids.

year: 2004-12-01

title: Optimisation of performance of dispersants in aqueous titanium slips

authors: Xu, Qian

subjects: Dispersants

abstract: Slip casting is a well-established ceramic casting technique used for large scale fabrication of ceramic products with complex shapes. A homogenous slip with a desired level of stability is required, which is controlled using a dispersant. This paper describes the selection and optimisation of various dispersants used to produce Ti powder slips. A consideration of the effect of concentration and pH of the solvent on the dispersion of anionic polyelectrolyte dispersants (Dispex N-40, Synthecol SD375 & Dolapix CE64) was examined by measuring the sedimentation height and rate, the streaming potential and the slip viscosity. It was found that Dolapix CE64 showed the best deflocculating effect at 0.3dw.% with pH of 7. In particular, the measurements on Dolapix CE64 gave consistent results. This indicated that Dolapix CE64 is an effective dispersant in the preparation of a titanium slip.

text: Optimisation of performance of dispersants in aqueous titanium slips Slip casting is a well-established ceramic casting technique used for large scale fabrication of ceramic products with complex shapes. A homogenous slip with a desired level of stability is required, which is controlled using a dispersant. This paper describes the selection and optimisation of various dispersants used to produce Ti powder slips. A consideration of the effect of concentration and pH of the solvent on the dispersion of anionic polyelectrolyte dispersants (Dispex N-40, Synthecol SD375 & Dolapix CE64) was examined by measuring the sedimentation height and rate, the streaming potential and the slip viscosity. It was found that Dolapix CE64 showed the best deflocculating effect at 0.3dw.% with pH of 7. In particular, the measurements on Dolapix CE64 gave consistent results. This indicated that Dolapix CE64 is an effective dispersant in the preparation of a titanium slip.

year: 2012

title: Ghost Town

authors: Wrigley, David

abstract: Abstract

A hometown is a thing full of horrors.
Ghosts line the footpaths like spectators at an ANZAC Day parade. They leap from thickets and pounce from suburban ranch sliders like tom cats. 
These ghosts have been waiting for you. There are things they need you to remember. 
When David Wrigley returns to Cambridge, a town he thought he’d left behind him forever, he finds the ghosts are out in force. He stumbles on a note in his mother’s garage, tightly folded and hot to the touch, that sets him off in pursuit of the memory of Jacob Avonlea, a friend from the past who he has never been able to leave behind.
But the currents of memory are unpredictable, and the waters and riverbanks are crowded with the dead. David and Jacob’s friendship, which crackled with a boyish intensity and a surfeit of secrets, was just the first of many stories tussling for attention.
 There is a family history – a fifty year old cataclysm that destroyed his brother. 
The grotesque origins of the school that nurtured David and murdered Jacob. The eccentric founder who brought with him from the mill towns of Manchester a fear of women and a predilection for young boys. 
And then there is the land – the meanders of the Waikato and the eruptions that diverted it from one coast to another, leaving forgotten oxbows in its wake. The roaming forests of kahikateas that followed the river and the wetlands, and once dominated these landscapes but have now all but disappeared. The rich farmland that has usurped the forests and slowly leaks poison into the soil and the waterways.
Ghost Town is a psychogeographer’s novel. A novel in which the landscape and the people that live and act upon it are inseparable, the ghosts of one haunting the present of the other.  It is a story of colonial men, locked into cycles of violence and destruction. The story of the silence they have inflicted upon themselves and on their children, and ultimately on the landscape itself, as the forests retreat, the birdsong hushed.
As we drift downstream, at every bend of the river we can see through the ever-widening gaps in the trees, glimpses of lost futures– that different species of ghost. 
A free and autonomous Māori Waikato. 
A spring-fed lake full of eels and koura. 
Five hundred year old kahikateas growing arrow-straight into the distant blueness.
An egalitarian, socialist Aotearoa. 
A family man gathering his sons into his arms.
A man of forty six raising his eyes towards the swaying tree-tops and starting to sing.

text: Ghost Town Abstract

A hometown is a thing full of horrors.
Ghosts line the footpaths like spectators at an ANZAC Day parade. They leap from thickets and pounce from suburban ranch sliders like tom cats. 
These ghosts have been waiting for you. There are things they need you to remember. 
When David Wrigley returns to Cambridge, a town he thought he’d left behind him forever, he finds the ghosts are out in force. He stumbles on a note in his mother’s garage, tightly folded and hot to the touch, that sets him off in pursuit of the memory of Jacob Avonlea, a friend from the past who he has never been able to leave behind.
But the currents of memory are unpredictable, and the waters and riverbanks are crowded with the dead. David and Jacob’s friendship, which crackled with a boyish intensity and a surfeit of secrets, was just the first of many stories tussling for attention.
 There is a family history – a fifty year old cataclysm that destroyed his brother. 
The grotesque origins of the school that nurtured David and murdered Jacob. The eccentric founder who brought with him from the mill towns of Manchester a fear of women and a predilection for young boys. 
And then there is the land – the meanders of the Waikato and the eruptions that diverted it from one coast to another, leaving forgotten oxbows in its wake. The roaming forests of kahikateas that followed the river and the wetlands, and once dominated these landscapes but have now all but disappeared. The rich farmland that has usurped the forests and slowly leaks poison into the soil and the waterways.
Ghost Town is a psychogeographer’s novel. A novel in which the landscape and the people that live and act upon it are inseparable, the ghosts of one haunting the present of the other.  It is a story of colonial men, locked into cycles of violence and destruction. The story of the silence they have inflicted upon themselves and on their children, and ultimately on the landscape itself, as the forests retreat, the birdsong hushed.
As we drift downstream, at every bend of the river we can see through the ever-widening gaps in the trees, glimpses of lost futures– that different species of ghost. 
A free and autonomous Māori Waikato. 
A spring-fed lake full of eels and koura. 
Five hundred year old kahikateas growing arrow-straight into the distant blueness.
An egalitarian, socialist Aotearoa. 
A family man gathering his sons into his arms.
A man of forty six raising his eyes towards the swaying tree-tops and starting to sing.

year: 2023