title: Petrogenesis and evolution of alkalic basaltic magmas in a continental intraplate setting: the South Auckland Volcanic Field, New Zealand

authors: Cook, Craig

abstract: The South Auckland volcanic field (SAVF) is situated in a continental intraplate tectonic setting and consists of silica-undersaturated alkalic basalts that erupted from about 100 centres between 1.59 and 0.51 Ma. The basalts range in composition from basanites to quartz tholeiites. Two basalt groups are distinguished based on their contrasting mineralogical and geochemical characteristics: group A, a less silica-undersaturated transitional basalt to quartz tholeiite suite; and group B, a strongly silica-undersaturated basanite to nepheline hawaiite suite. The petrogenesis and evolution of the SAVF basalts is examined using new data from 200 samples on mineral chemistry from electron microprobe analyses, major and trace elements from XRF, incompatible trace elements and REE from ICP-MS, and Sr, Nd, and Pb isotopic data from TIMS analyses.

Forsteritic olivine is the dominant phenocryst phase in each rock group (group A: Fo₆₁ - Fo₈₂; group B: Fo₆₄ - Fo₉₂). Clinopyroxene is abundant and ranges from augite (Wo₃₅₋₄₇ En₃₆₋₅₀ Fs₁₁₋₂₃) in group A to diopside (Wo₄₂₋₅₂ En₃₂₋₄₆ Fs₁₀₋₂₀) in group B basalts. Plagioclase (An₄₀₋₇₀) is found as a phenocryst only in group A basalts. The group A basalts are distinguished by their low total alkalis (3.0 - 4.8 wt.%), Nb (9 - 29 ppm) and Zr (97 - 210 ppm) abundances, and low (La/Yb)N (3.4- 7.6), which contrast with group B that have large total alkalis (3.3 - 7.9 wt.%), Nb (35 - 102 ppm) and Zr (194 - 491 ppm), and (La/Yb)N (12 - 47).

The incompatible trace elements of group A lavas have characteristics indicating derivation from an enriched upper mantle source but relatively depleted in Th, K, Nb, Ta, and LREE with small LREE/HREE values, whereas those in group B exhibit strong trace element affinities (i.e., large Th, Nb, Ta, and LREE abundances) with an OIB-like source. Petrogenetic modelling suggests that the group A and B lavas evolved as discrete lineages that do not appear to be related to a common parental magma or source. Partial melting models indicate that < 8 % melting of a garnet-peridotite source is required to produce primary group B magmas, whereas primary group A magmas are generated from < 11 % melting of a spinel-peridotite source. Differentiation of basalts from each group is dominated by olivine and clinopyroxene fractionation, and only minor plagioclase in group A.

Both rock groups fall within a narrow range of Sr and Nd isotopic compositions (⁸⁷Sr/⁸⁶Sr= 0.70273±19 - 0.70330±17 and εNd = + 5.97 to + 6.89) similar to the composition of HIMU-OIB, whereas Pb isotopic compositions are unradiogenic relative to HIMU-OIB (i.e., ²⁰⁶Pb/²⁰⁴Pb = 18.95 - 19.33; ²⁰⁷Pb/²⁰⁴Pb = 15.586 - 15.589; ²⁰⁸Pb/²⁰⁴Pb = 38.731 -38.906) and range between Atlantic MORB and EMII. The group A lavas have slightly higher ⁸⁷Sr/⁸⁶Sr and ²⁰⁷Pb/²⁰⁴Pb, lower ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb, and similar εNd values compared to those in group B, but there is no isotopic or geochemical evidence to suggest that any of the lavas have been contaminated by continental crust. Therefore, the relatively small but distinct differences in Sr and Pb isotopic compositions and similar εNd values are considered to be source-related.

Variations in incompatible element ratios such as K/Nb and Zr/Nb indicate that the SA VF basalts were derived from two distinct sources. Group B basalts show incompatible trace element signatures characteristic of a LREE-enriched HIMU-OIB-like source, which can be accounted for by recycling of subducted oceanic crust at mantle depths. In contrast, the group A basalts have incompatible trace element affinities that are intermediate between a HIMU and an EMII-type component that could have resulted from subduction-related metasomatism of the subcontinental lithosphere modified by a HIMU plume. These events may have been connected with the subduction of the Phoenix plate and plume-related magmatism when New Zealand was at the eastern margin of the Gondwanaland supercontinent.

text: Petrogenesis and evolution of alkalic basaltic magmas in a continental intraplate setting: the South Auckland Volcanic Field, New Zealand The South Auckland volcanic field (SAVF) is situated in a continental intraplate tectonic setting and consists of silica-undersaturated alkalic basalts that erupted from about 100 centres between 1.59 and 0.51 Ma. The basalts range in composition from basanites to quartz tholeiites. Two basalt groups are distinguished based on their contrasting mineralogical and geochemical characteristics: group A, a less silica-undersaturated transitional basalt to quartz tholeiite suite; and group B, a strongly silica-undersaturated basanite to nepheline hawaiite suite. The petrogenesis and evolution of the SAVF basalts is examined using new data from 200 samples on mineral chemistry from electron microprobe analyses, major and trace elements from XRF, incompatible trace elements and REE from ICP-MS, and Sr, Nd, and Pb isotopic data from TIMS analyses.

Forsteritic olivine is the dominant phenocryst phase in each rock group (group A: Fo₆₁ - Fo₈₂; group B: Fo₆₄ - Fo₉₂). Clinopyroxene is abundant and ranges from augite (Wo₃₅₋₄₇ En₃₆₋₅₀ Fs₁₁₋₂₃) in group A to diopside (Wo₄₂₋₅₂ En₃₂₋₄₆ Fs₁₀₋₂₀) in group B basalts. Plagioclase (An₄₀₋₇₀) is found as a phenocryst only in group A basalts. The group A basalts are distinguished by their low total alkalis (3.0 - 4.8 wt.%), Nb (9 - 29 ppm) and Zr (97 - 210 ppm) abundances, and low (La/Yb)N (3.4- 7.6), which contrast with group B that have large total alkalis (3.3 - 7.9 wt.%), Nb (35 - 102 ppm) and Zr (194 - 491 ppm), and (La/Yb)N (12 - 47).

The incompatible trace elements of group A lavas have characteristics indicating derivation from an enriched upper mantle source but relatively depleted in Th, K, Nb, Ta, and LREE with small LREE/HREE values, whereas those in group B exhibit strong trace element affinities (i.e., large Th, Nb, Ta, and LREE abundances) with an OIB-like source. Petrogenetic modelling suggests that the group A and B lavas evolved as discrete lineages that do not appear to be related to a common parental magma or source. Partial melting models indicate that < 8 % melting of a garnet-peridotite source is required to produce primary group B magmas, whereas primary group A magmas are generated from < 11 % melting of a spinel-peridotite source. Differentiation of basalts from each group is dominated by olivine and clinopyroxene fractionation, and only minor plagioclase in group A.

Both rock groups fall within a narrow range of Sr and Nd isotopic compositions (⁸⁷Sr/⁸⁶Sr= 0.70273±19 - 0.70330±17 and εNd = + 5.97 to + 6.89) similar to the composition of HIMU-OIB, whereas Pb isotopic compositions are unradiogenic relative to HIMU-OIB (i.e., ²⁰⁶Pb/²⁰⁴Pb = 18.95 - 19.33; ²⁰⁷Pb/²⁰⁴Pb = 15.586 - 15.589; ²⁰⁸Pb/²⁰⁴Pb = 38.731 -38.906) and range between Atlantic MORB and EMII. The group A lavas have slightly higher ⁸⁷Sr/⁸⁶Sr and ²⁰⁷Pb/²⁰⁴Pb, lower ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb, and similar εNd values compared to those in group B, but there is no isotopic or geochemical evidence to suggest that any of the lavas have been contaminated by continental crust. Therefore, the relatively small but distinct differences in Sr and Pb isotopic compositions and similar εNd values are considered to be source-related.

Variations in incompatible element ratios such as K/Nb and Zr/Nb indicate that the SA VF basalts were derived from two distinct sources. Group B basalts show incompatible trace element signatures characteristic of a LREE-enriched HIMU-OIB-like source, which can be accounted for by recycling of subducted oceanic crust at mantle depths. In contrast, the group A basalts have incompatible trace element affinities that are intermediate between a HIMU and an EMII-type component that could have resulted from subduction-related metasomatism of the subcontinental lithosphere modified by a HIMU plume. These events may have been connected with the subduction of the Phoenix plate and plume-related magmatism when New Zealand was at the eastern margin of the Gondwanaland supercontinent.

year: 2002

title: Living in two worlds. Challenges facing Pacific communities: The case of Fijians in New Zealand

authors: Vunidilo, Kalisito

subjects: Fijians

abstract: Living in two worlds is an insider perspective of how indigenous Pacific Immigrant communities, in this specific case Fijian's living in New Zealand face the challenges of living two cultures in a developed country like New Zealand.  The quest to hold on to one's indigenous culture while adapting to another, in order to survive the realities of everyday circumstances can be a complicated struggle. 

The main objective of this research was to collate and analyze information from Fijian families who migrated to New Zealand from 1970's to the mid 1980's with reference to the challenges they faced.  In order to understand such constant struggles there are underlying questions and factors that should be considered.  For example - why do people continue to be conservative about their cultural identities or how do they react to unfamiliar challenges in a multicultural society.  Another could be - what influences have been seen in order for their children to recognize their indigenous identity.  Comparable factors that will bring to other aspects of living in two worlds which would be considered were socio-economic issues, higher education, technological advancement, immigration policies, development constraints and quality of living standards.

Fijians and other indigenous Pacific people have through the years gained the ultimate will to defend their cultural and traditional identity whilst living in a world of western values and culture.  Coupled with this have been the complexities of holding on to the values of both worlds.  As this project probed into these newly rediscovered stories about journeys to their new homeland filled with opportunities, capitalism or westernization had never withered their passion and dreams as Pacific people to better themselves.  They also enjoyed the luxury of both worlds as conservators of Pacific cultures and exploiters of technological advancement filled with huge dreams, opportunities and better standards of living. 

Fijians have the smallest population of Pacific people in New Zealand when compared to Samoa, Tonga, and Cook Islanders.  There were relatively small number of Fijians who arrived after the end of World War 2 and they were basically employed in farms, forestry work stations and industrial areas.  Others were in New Zealand on government scholarships, training or internship and work experience programs. Most of these people returned home while a very small proportion stayed behind.  

In the early 1970's and 1980's there was also an influx of seasonal workers in the Central North Island areas including Hawkes Bay, Tokoroa and the Waikato region.  Most people were recruited from the Pacific Islands including Fiji because of their hard working attitude and cheap labour margins.  When their term was completed some decided to stay and work, eventually residing legally and permanently with their families.  Another group of men came via Wellington by boat, destined to become maintenance and repair workers. (bound for maintenance and repair work and ) but were left stranded when the shipping company ownership changed.  The dock and maritime workers union fought for the case stating the government on humanitarian grounds should provide them with employment and residency status.  After an extensive legal struggle, which lasted almost seven years these early Fijian workers and their families were granted work and residency permits.  The (remaining) other families came as visitors or through marriage links and were granted work and residency permits.

The 1996 statistics (Statistics New Zealand, Census 1996) stated that Fijians were the most highly skilled and educated Pacific Island population in New Zealand.  These statistics had been directly influenced by the latest influx of well educated and highly qualified Fijians who arrived in the late 1990's.  The research will also highlight whether those who arrived before this latest influx faced the same challenges.  These challenges will be compared to those faced by the generation of Fijians and Pacific people who were born and bred in New Zealand.

text: Living in two worlds. Challenges facing Pacific communities: The case of Fijians in New Zealand Living in two worlds is an insider perspective of how indigenous Pacific Immigrant communities, in this specific case Fijian's living in New Zealand face the challenges of living two cultures in a developed country like New Zealand.  The quest to hold on to one's indigenous culture while adapting to another, in order to survive the realities of everyday circumstances can be a complicated struggle. 

The main objective of this research was to collate and analyze information from Fijian families who migrated to New Zealand from 1970's to the mid 1980's with reference to the challenges they faced.  In order to understand such constant struggles there are underlying questions and factors that should be considered.  For example - why do people continue to be conservative about their cultural identities or how do they react to unfamiliar challenges in a multicultural society.  Another could be - what influences have been seen in order for their children to recognize their indigenous identity.  Comparable factors that will bring to other aspects of living in two worlds which would be considered were socio-economic issues, higher education, technological advancement, immigration policies, development constraints and quality of living standards.

Fijians and other indigenous Pacific people have through the years gained the ultimate will to defend their cultural and traditional identity whilst living in a world of western values and culture.  Coupled with this have been the complexities of holding on to the values of both worlds.  As this project probed into these newly rediscovered stories about journeys to their new homeland filled with opportunities, capitalism or westernization had never withered their passion and dreams as Pacific people to better themselves.  They also enjoyed the luxury of both worlds as conservators of Pacific cultures and exploiters of technological advancement filled with huge dreams, opportunities and better standards of living. 

Fijians have the smallest population of Pacific people in New Zealand when compared to Samoa, Tonga, and Cook Islanders.  There were relatively small number of Fijians who arrived after the end of World War 2 and they were basically employed in farms, forestry work stations and industrial areas.  Others were in New Zealand on government scholarships, training or internship and work experience programs. Most of these people returned home while a very small proportion stayed behind.  

In the early 1970's and 1980's there was also an influx of seasonal workers in the Central North Island areas including Hawkes Bay, Tokoroa and the Waikato region.  Most people were recruited from the Pacific Islands including Fiji because of their hard working attitude and cheap labour margins.  When their term was completed some decided to stay and work, eventually residing legally and permanently with their families.  Another group of men came via Wellington by boat, destined to become maintenance and repair workers. (bound for maintenance and repair work and ) but were left stranded when the shipping company ownership changed.  The dock and maritime workers union fought for the case stating the government on humanitarian grounds should provide them with employment and residency status.  After an extensive legal struggle, which lasted almost seven years these early Fijian workers and their families were granted work and residency permits.  The (remaining) other families came as visitors or through marriage links and were granted work and residency permits.

The 1996 statistics (Statistics New Zealand, Census 1996) stated that Fijians were the most highly skilled and educated Pacific Island population in New Zealand.  These statistics had been directly influenced by the latest influx of well educated and highly qualified Fijians who arrived in the late 1990's.  The research will also highlight whether those who arrived before this latest influx faced the same challenges.  These challenges will be compared to those faced by the generation of Fijians and Pacific people who were born and bred in New Zealand.

year: 2006

title: Waikato shallow lakes modelling

authors: Lehmann, Moritz K.

subjects: Lakes

abstract: The principal aim of this study is to apply a modelling approach to identify, evaluate and prioritise specific in-lake and catchment restoration options which could be applied to improve the water quality and ecological health of peat and riverine lake types across the Waikato Region. Four representative lakes have been selected as case studies for this work based on their social, cultural and ecological significance, as well as the availability of historical monitoring data and the potential transferability of the study findings to similar lake systems. The lakes include Rotomānuka, Ngāroto, Waahi and Waikare.

text: Waikato shallow lakes modelling The principal aim of this study is to apply a modelling approach to identify, evaluate and prioritise specific in-lake and catchment restoration options which could be applied to improve the water quality and ecological health of peat and riverine lake types across the Waikato Region. Four representative lakes have been selected as case studies for this work based on their social, cultural and ecological significance, as well as the availability of historical monitoring data and the potential transferability of the study findings to similar lake systems. The lakes include Rotomānuka, Ngāroto, Waahi and Waikare.

year: 2017