title: Sediment removal as a restoration measure for the campus lakes

authors: Paul, Wendy J.

abstract: The Campus Lakes, Oranga and Knighton, were formed about 1969 as a means of draining the wet, swampy land that the University of Waikato was sited on. Since Prof. Wilf Malcolm, (Vice-chancellor, 1985-1994) first expressed concern about the water quality of the Campus Lakes (Kingsbury, 1989), they have been the subject of at least four reports and one thesis. A number of approaches for improving the lake water quality have been tried or recommended, largely without success. The lakes continue to be unsightly with exotic weed growing to nuisance proportions and phytoplankton scums and blooms occurring annually, as well as discoloration from high concentrations of suspended sediments. The indigenous biodiversity values are low due to domination by pest fish and exotic macrophytes.

This report is part of a larger scale recommendation to take an integrated approach towards the management of Oranga and Knighton lakes. The focus of this study was to investigate the possibility of removal of 0.2 m of the nutrient and organic-rich surficial sediments from the two lakes, and disposal of that sediment by spreading it onto the university playing fields. The specific aims of this study were to determine contaminant concentrations (heavy metals and persistent organochlorines) in the sediments and relate these concentrations to soil environmental guideline values for human health with parkland/recreational land use.

text: Sediment removal as a restoration measure for the campus lakes The Campus Lakes, Oranga and Knighton, were formed about 1969 as a means of draining the wet, swampy land that the University of Waikato was sited on. Since Prof. Wilf Malcolm, (Vice-chancellor, 1985-1994) first expressed concern about the water quality of the Campus Lakes (Kingsbury, 1989), they have been the subject of at least four reports and one thesis. A number of approaches for improving the lake water quality have been tried or recommended, largely without success. The lakes continue to be unsightly with exotic weed growing to nuisance proportions and phytoplankton scums and blooms occurring annually, as well as discoloration from high concentrations of suspended sediments. The indigenous biodiversity values are low due to domination by pest fish and exotic macrophytes.

This report is part of a larger scale recommendation to take an integrated approach towards the management of Oranga and Knighton lakes. The focus of this study was to investigate the possibility of removal of 0.2 m of the nutrient and organic-rich surficial sediments from the two lakes, and disposal of that sediment by spreading it onto the university playing fields. The specific aims of this study were to determine contaminant concentrations (heavy metals and persistent organochlorines) in the sediments and relate these concentrations to soil environmental guideline values for human health with parkland/recreational land use.

year: 2008-05

title: Volcanic geology and hydrothermal alteration of the Onemana Area, Eastern Coromandel Peninsula

authors: Aldrich, Sean Mark

subjects: Volcanic Geology

abstract: The Onemana Peninsula is located on the eastern side of the Coromandel Peninsula north of the township of Whangamata. This study investigates the volcanology, structure and hydrothermal alteration of the northern half of the Onemana Peninsula. The study area is dominated by rhyolite domes and lava flows, with minor andesite lavas, rhyolite pyroclastics and lake sediments. The central region is extensively hydrothermally altered, with high levels of the original system preserved including hydrothermal eruption breccias and sinters.

The Onemana area is dominated by three rhyolite dome complexes: Pohakahaka, Pokohino, and Wharekawa. The Pohakahaka Dome Complex in the south of the study area consists of pyroxene rhyolite domes, lavas and autoclastic breccias. The Pokohino Dome Complex in the central region of the study area consists of biotite rhyolite domes, lavas and autoclastic breccias. Lavas appear to have erupted as coulees and have flowed in a SE direction from a NE-trending ridge. The Wharekawa Dome Complex and Eastern Flows are dominated by biotite rhyolites. Pyroclastic and epiclastic material is overlain by rhyolite lavas in coastal sections north of Pokohino Beach, suggesting explosive activity preceded the eruption of some lavas. Some Eastern Flow lavas have flowed into water and produced a hyaloclastite in the north of the area. The deposition of the Glassy Dome Pyroclastics is thought to have resulted from the collapse of a rhyolite dome. Andesite lavas occur in the west of the study area, and their compositions suggest that they are related to the McBeths Andesite which outcrops 6 km to the NW. A hornblende-biotite ignimbrite is exposed in the north of the area, and is thought to have been erupted from outside the area. Thick lake sediments occur between the Pokohino and Wharekawa dome complexes and infill a graben structure. A hydrothermal eruption breccia resulting from over-pressuring of a geothermal system overlies the lake sediments. 

The structure of the area is dominated by NW, N, and NE striking faults, and minor EW striking faults. The local structure plays an important role in controlling the locations of volcanism and hydrothermal activity. Older N-striking structures appear to have controlled vent locations for the pyroxene rhyolites, while NE-striking structures have controlled the location the biotite rhyolites and hydrothermal alteration. Mineralised structures are controlled by NW and N striking faults between the NE striking Whitipirorua and Pokohino Faults.

XRF analysis of selected volcanic rocks from Onemana show the area to be dominated by medium-K to high-K rhyolites (75-78 wt% SiO₂), with minor andesite (56-58 wt% SiO₂). On the basis of Zr abundance the rhyolites can be divided into high Zr (pyroxene rhyolites) and low Zr (biotite rhyolites, Glassy Dome Rhyolite). The rhyolites are thought to be closely associated with partial melting of the continental crust in a rifting environment.

Pervasive to weak alteration occurs within a NE-trending corridor bounded by the Whitipirorua and Pokohino Faults. There are two main alteration types in the area which represent different hydrothermal environments: alkaline and acid alteration. Alkaline alteration consists of an inner core of quartz silicification, surrounded by quartz+ K-feldspar alteration, which grades out into epidote and weak clay alteration assemblages. Zeolites also occur as an overprinting alteration assemblage. Acid alteration consists of pervasive kaolinite alteration, with small areas of quartz + illite/smectite ± pyrophyllite alteration and opaline quartz silicification.

The Onemana area shows many volcanic and hydrothermal features that are typical of caldera settings and are comparable with the rhyolite volcanic centres in the TVZ. It is suggested that the rhyolitic volcanism at Onemana resulted from late stage volcanism along the ring fracture of a large caldera structure.

text: Volcanic geology and hydrothermal alteration of the Onemana Area, Eastern Coromandel Peninsula The Onemana Peninsula is located on the eastern side of the Coromandel Peninsula north of the township of Whangamata. This study investigates the volcanology, structure and hydrothermal alteration of the northern half of the Onemana Peninsula. The study area is dominated by rhyolite domes and lava flows, with minor andesite lavas, rhyolite pyroclastics and lake sediments. The central region is extensively hydrothermally altered, with high levels of the original system preserved including hydrothermal eruption breccias and sinters.

The Onemana area is dominated by three rhyolite dome complexes: Pohakahaka, Pokohino, and Wharekawa. The Pohakahaka Dome Complex in the south of the study area consists of pyroxene rhyolite domes, lavas and autoclastic breccias. The Pokohino Dome Complex in the central region of the study area consists of biotite rhyolite domes, lavas and autoclastic breccias. Lavas appear to have erupted as coulees and have flowed in a SE direction from a NE-trending ridge. The Wharekawa Dome Complex and Eastern Flows are dominated by biotite rhyolites. Pyroclastic and epiclastic material is overlain by rhyolite lavas in coastal sections north of Pokohino Beach, suggesting explosive activity preceded the eruption of some lavas. Some Eastern Flow lavas have flowed into water and produced a hyaloclastite in the north of the area. The deposition of the Glassy Dome Pyroclastics is thought to have resulted from the collapse of a rhyolite dome. Andesite lavas occur in the west of the study area, and their compositions suggest that they are related to the McBeths Andesite which outcrops 6 km to the NW. A hornblende-biotite ignimbrite is exposed in the north of the area, and is thought to have been erupted from outside the area. Thick lake sediments occur between the Pokohino and Wharekawa dome complexes and infill a graben structure. A hydrothermal eruption breccia resulting from over-pressuring of a geothermal system overlies the lake sediments. 

The structure of the area is dominated by NW, N, and NE striking faults, and minor EW striking faults. The local structure plays an important role in controlling the locations of volcanism and hydrothermal activity. Older N-striking structures appear to have controlled vent locations for the pyroxene rhyolites, while NE-striking structures have controlled the location the biotite rhyolites and hydrothermal alteration. Mineralised structures are controlled by NW and N striking faults between the NE striking Whitipirorua and Pokohino Faults.

XRF analysis of selected volcanic rocks from Onemana show the area to be dominated by medium-K to high-K rhyolites (75-78 wt% SiO₂), with minor andesite (56-58 wt% SiO₂). On the basis of Zr abundance the rhyolites can be divided into high Zr (pyroxene rhyolites) and low Zr (biotite rhyolites, Glassy Dome Rhyolite). The rhyolites are thought to be closely associated with partial melting of the continental crust in a rifting environment.

Pervasive to weak alteration occurs within a NE-trending corridor bounded by the Whitipirorua and Pokohino Faults. There are two main alteration types in the area which represent different hydrothermal environments: alkaline and acid alteration. Alkaline alteration consists of an inner core of quartz silicification, surrounded by quartz+ K-feldspar alteration, which grades out into epidote and weak clay alteration assemblages. Zeolites also occur as an overprinting alteration assemblage. Acid alteration consists of pervasive kaolinite alteration, with small areas of quartz + illite/smectite ± pyrophyllite alteration and opaline quartz silicification.

The Onemana area shows many volcanic and hydrothermal features that are typical of caldera settings and are comparable with the rhyolite volcanic centres in the TVZ. It is suggested that the rhyolitic volcanism at Onemana resulted from late stage volcanism along the ring fracture of a large caldera structure.

year: 1995

title: Ranapia Mokena: son of Mokena Hou

authors: Hart, Philip

abstract: Little is known of the early life of Ranapia Mokena. He owned land close to Thames and acquired interests in other blocks, which provided him with some income, but he was never wealthy, as indicated by his being sued for a series of small debts. He invested in a small way in mining at both Thames and Te Aroha, and even worked in one claim. His life was most notable for being a deacon in the Church of England.
Ranapia was another example of a rangatira who supported the Crown, as was illustrated by his becoming a member of the Thames Native Rifle Volunteers. Childless, in his old age he brought up a niece’s daughter.

text: Ranapia Mokena: son of Mokena Hou Little is known of the early life of Ranapia Mokena. He owned land close to Thames and acquired interests in other blocks, which provided him with some income, but he was never wealthy, as indicated by his being sued for a series of small debts. He invested in a small way in mining at both Thames and Te Aroha, and even worked in one claim. His life was most notable for being a deacon in the Church of England.
Ranapia was another example of a rangatira who supported the Crown, as was illustrated by his becoming a member of the Thames Native Rifle Volunteers. Childless, in his old age he brought up a niece’s daughter.

year: 2016