title: Felsic volcanism in the eastern Waihi area; process origins of the Corbett and Ratarua ignimbrites and the Hikurangi Rhyolite

authors: Cook, Elizabeth Teresa

subjects: ignimbrites

abstract: Volcanic activity began in the north Coromandel Volcanic Zone (CVZ) at 18 Ma, migrated southward during the Miocene to Pliocene, and continued until the Pleistocene (1.9 Ma). The Waihi Caldera was active during the Pliocene and has been infilled with lake sediments (Romanga Formation) and three rhyolitic ignimbrites of the Whitianga Group, the Corbett, Waikino and Owharoa ignimbrites. This study constrains the volcanic history and processes involved in the formation of three volcanic units in eastern Waihi; the Corbett Ignimbrite, Ratarua Ignimbrite and Hikurangi Rhyolite. Detailed stratigraphic logs, petrographic studies, geochemical analyses and U-Pb dating of zircons are presented for each unit.

The Corbett Ignimbrite is a widespread deposit which is constrained to eastern Waihi. It has a maximum exposed thickness of 18 m at its type section, and is a creamy-buff, pumice-rich, crystal-rich, moderately-welded ignimbrite. The basal zone of the ignimbrite is pumice-rich (40-50%), crystal-rich (20-30%) and contains two distinct lithic concentration zones. At one locality the ignimbrite consists of a 9 m thick densely welded zone with abundant fiamme. The matrix is composed of fine ash with shard textures only visible under the scanning electron microscope. Crystals comprise plagioclase, quartz, hornblende, orthopyroxene, augite, titanomagnetite, ilmenite and zircon. Lithics are predominantly andesite with minor rhyolite, dacite and greywacke. Lithic concentration zones suggest that collapse and erosion of the vent occurred several times during the eruption, and these were emplaced by rapid depositional pulses. The upper half of the outcrop represents a more steady flow. Pumice and glass shard composition shows a transition from andesitic to rhyolitic. The source of the Corbett Ignimbrite was thought to have been from either a silicic centre in the vicinity of the Bowentown Rhyolite or from the Waihi Caldera. However, the U-Pb age 6.09 + 0.34 Ma is consistent with older source vents located elsewhere, with two other possible vent locations assessed.

The Corbett Ignimbrite pyroclastic flow was constrained by the welded, fiamme and crystal-rich, dacitic Ratarua Ignimbrite which has been dated at 6.79 + 0.42 Ma. The Ratarua Ignimbrite is exposed on hillsides as angular blocks ranging from 30 cm to several metres in size. Crystals comprise plagioclase, hornblende, orthopyroxene, augite, titanomagnetite, ilmenite and zircon. Lithics are andesite, dacite, rhyolite and rare sandstone.

The spherulitic Hikurangi Rhyolite dome belongs to the Homunga Rhyolite formation and overlies the Corbett Ignimbrite in southeastern Waihi. This rhyolite dome contains quartz, plagioclase, biotite, titanomagnetite and ilmenite phenocrysts. Petrographical analysis of granophyric intergrowth crystals indicates the presence of a granite body below this dome, which is the first evidence of granite present in southern CVZ. U-Pb dating of zircons determined an age of 4.53 + 0.13 Ma for this dome showing a younging in age of the Homunga Rhyolite formation southwards.

The units included in this study show a progression in volcanism with a transition from andesite dominant to rhyolitic. The Ratarua Ignimbrite formed during an earlier period dominated by andesite volcanism. This ignimbrite pre-dates the Corbett Ignimbrite, which formed during later andesitic volcanism in the eastern Waihi area, predating the Waihi Caldera. The youngest unit in this study, the Hikurangi Rhyolite, shows younger rhyolitic volcanism in southeastern Waihi.

text: Felsic volcanism in the eastern Waihi area; process origins of the Corbett and Ratarua ignimbrites and the Hikurangi Rhyolite Volcanic activity began in the north Coromandel Volcanic Zone (CVZ) at 18 Ma, migrated southward during the Miocene to Pliocene, and continued until the Pleistocene (1.9 Ma). The Waihi Caldera was active during the Pliocene and has been infilled with lake sediments (Romanga Formation) and three rhyolitic ignimbrites of the Whitianga Group, the Corbett, Waikino and Owharoa ignimbrites. This study constrains the volcanic history and processes involved in the formation of three volcanic units in eastern Waihi; the Corbett Ignimbrite, Ratarua Ignimbrite and Hikurangi Rhyolite. Detailed stratigraphic logs, petrographic studies, geochemical analyses and U-Pb dating of zircons are presented for each unit.

The Corbett Ignimbrite is a widespread deposit which is constrained to eastern Waihi. It has a maximum exposed thickness of 18 m at its type section, and is a creamy-buff, pumice-rich, crystal-rich, moderately-welded ignimbrite. The basal zone of the ignimbrite is pumice-rich (40-50%), crystal-rich (20-30%) and contains two distinct lithic concentration zones. At one locality the ignimbrite consists of a 9 m thick densely welded zone with abundant fiamme. The matrix is composed of fine ash with shard textures only visible under the scanning electron microscope. Crystals comprise plagioclase, quartz, hornblende, orthopyroxene, augite, titanomagnetite, ilmenite and zircon. Lithics are predominantly andesite with minor rhyolite, dacite and greywacke. Lithic concentration zones suggest that collapse and erosion of the vent occurred several times during the eruption, and these were emplaced by rapid depositional pulses. The upper half of the outcrop represents a more steady flow. Pumice and glass shard composition shows a transition from andesitic to rhyolitic. The source of the Corbett Ignimbrite was thought to have been from either a silicic centre in the vicinity of the Bowentown Rhyolite or from the Waihi Caldera. However, the U-Pb age 6.09 + 0.34 Ma is consistent with older source vents located elsewhere, with two other possible vent locations assessed.

The Corbett Ignimbrite pyroclastic flow was constrained by the welded, fiamme and crystal-rich, dacitic Ratarua Ignimbrite which has been dated at 6.79 + 0.42 Ma. The Ratarua Ignimbrite is exposed on hillsides as angular blocks ranging from 30 cm to several metres in size. Crystals comprise plagioclase, hornblende, orthopyroxene, augite, titanomagnetite, ilmenite and zircon. Lithics are andesite, dacite, rhyolite and rare sandstone.

The spherulitic Hikurangi Rhyolite dome belongs to the Homunga Rhyolite formation and overlies the Corbett Ignimbrite in southeastern Waihi. This rhyolite dome contains quartz, plagioclase, biotite, titanomagnetite and ilmenite phenocrysts. Petrographical analysis of granophyric intergrowth crystals indicates the presence of a granite body below this dome, which is the first evidence of granite present in southern CVZ. U-Pb dating of zircons determined an age of 4.53 + 0.13 Ma for this dome showing a younging in age of the Homunga Rhyolite formation southwards.

The units included in this study show a progression in volcanism with a transition from andesite dominant to rhyolitic. The Ratarua Ignimbrite formed during an earlier period dominated by andesite volcanism. This ignimbrite pre-dates the Corbett Ignimbrite, which formed during later andesitic volcanism in the eastern Waihi area, predating the Waihi Caldera. The youngest unit in this study, the Hikurangi Rhyolite, shows younger rhyolitic volcanism in southeastern Waihi.

year: 2016

title: The cultural classroom: The faikava as an epistemological site for teaching and learning

authors: Fehoko, Edmond S.

subjects: Tongan

abstract: My Masters research explored the experiences and perceptions of New Zealand-born Tongan males who participate in the faikava (kava-drinking). The faikava is a well-known ceremonial cultural practice that in recent times has been adapted as an informal and recreational activity embedded in the activities of some churches and other agencies in Tongan migrant communities in New Zealand, Australia and in the United States of America. This cultural practice includes aspects of socialising, sharing and talking, social bonding and fostering camaraderie. For my study, the faikava was the vehicle for my data collection. This presentation will argue the value of the faikava as an epistemological site which provides New Zealand- born Tongan males with the opportunity to reinforce their knowledge of the anga fakatonga (Tongan culture) protocols and language and to engage in discussion about issues of concern to Tongan people today. Drawing on this, I will share my experience in researching in a gendered, social and cultural space in a predominant male practice.

text: The cultural classroom: The faikava as an epistemological site for teaching and learning My Masters research explored the experiences and perceptions of New Zealand-born Tongan males who participate in the faikava (kava-drinking). The faikava is a well-known ceremonial cultural practice that in recent times has been adapted as an informal and recreational activity embedded in the activities of some churches and other agencies in Tongan migrant communities in New Zealand, Australia and in the United States of America. This cultural practice includes aspects of socialising, sharing and talking, social bonding and fostering camaraderie. For my study, the faikava was the vehicle for my data collection. This presentation will argue the value of the faikava as an epistemological site which provides New Zealand- born Tongan males with the opportunity to reinforce their knowledge of the anga fakatonga (Tongan culture) protocols and language and to engage in discussion about issues of concern to Tongan people today. Drawing on this, I will share my experience in researching in a gendered, social and cultural space in a predominant male practice.

year: 2017

title: Tūtereinga o Pirirākau: He piringa rākau,  he piringa whakairo, he piringa whare, he piringa mana Māori motuhake Reclaiming identity and mana Māori motuhake

authors: Rolleston, Elisha

subjects: Ngāti Ranginui

abstract: Since the early 19th century, colonisation has deeply harmed Pirirākau, a hapū of Ngāti Ranginui in Tauranga moana, severely and consistently undermining our vitality, livelihood, ambitions, and aspirations. Colonisation through the lens of land alienation, economic impoverishment, mass settler immigration, warfare, cultural marginalisation and assimilation, and multi-level hegemonic racism has had profound negative impacts on the identity, connectedness, sense of belonging, and mana Māori motuhake for Pirirākau.

As a counter-colonial strategy, this thesis explores the role that the Tūtereinga whare whakairo has contributed towards the reclamation of the identity and mana Māori motuhake for Pirirākau. Tūtereinga whare whakairo, a mnemonic architectural vessel fashioned with anthropomorphic figures, is pivotal in the reclamation of the identity and mana Māori motuhake for Pirirākau. Our wharenui is the focal point of our marae – Tūtereinga and remains the cornerstone of the identity of Pirirākau. The historic moments manifested in its carved patterns and structural elements are inextricably connected with and dependent upon the structure of the world fabricated by mātauranga Māori. However, due to the disastrous effects of colonisation, whakairo rākau and its associated architectural practices that are central to Māori identity and mana Māori motuhake suffered decline in many parts of Aotearoa, leading to the detrimental impacts of Māori identity and mana Māori motuhake.

Our wharenui Tūtereinga is a visual representation of our identity and mana that preserves our whakapapa, history, and inter-generational narratives unique to Pirirākau in the form of whakairo rākau, tukutuku, and kōwhaiwhai, enabling the transmission of knowledge for generations through traditional narratives and customary protocols and practices.

text: Tūtereinga o Pirirākau: He piringa rākau,  he piringa whakairo, he piringa whare, he piringa mana Māori motuhake Reclaiming identity and mana Māori motuhake Since the early 19th century, colonisation has deeply harmed Pirirākau, a hapū of Ngāti Ranginui in Tauranga moana, severely and consistently undermining our vitality, livelihood, ambitions, and aspirations. Colonisation through the lens of land alienation, economic impoverishment, mass settler immigration, warfare, cultural marginalisation and assimilation, and multi-level hegemonic racism has had profound negative impacts on the identity, connectedness, sense of belonging, and mana Māori motuhake for Pirirākau.

As a counter-colonial strategy, this thesis explores the role that the Tūtereinga whare whakairo has contributed towards the reclamation of the identity and mana Māori motuhake for Pirirākau. Tūtereinga whare whakairo, a mnemonic architectural vessel fashioned with anthropomorphic figures, is pivotal in the reclamation of the identity and mana Māori motuhake for Pirirākau. Our wharenui is the focal point of our marae – Tūtereinga and remains the cornerstone of the identity of Pirirākau. The historic moments manifested in its carved patterns and structural elements are inextricably connected with and dependent upon the structure of the world fabricated by mātauranga Māori. However, due to the disastrous effects of colonisation, whakairo rākau and its associated architectural practices that are central to Māori identity and mana Māori motuhake suffered decline in many parts of Aotearoa, leading to the detrimental impacts of Māori identity and mana Māori motuhake.

Our wharenui Tūtereinga is a visual representation of our identity and mana that preserves our whakapapa, history, and inter-generational narratives unique to Pirirākau in the form of whakairo rākau, tukutuku, and kōwhaiwhai, enabling the transmission of knowledge for generations through traditional narratives and customary protocols and practices.

year: 2024