title: Zircon response to high-grade metamorphism as revealed by U–Pb and cathodoluminescence studies

authors: Siebel, Wolfgang

subjects: Bohemian Massif

abstract: The Acigöl rhyolite field erupted the most recent high-silica rhyolites within the Cappadocian Volcanic Province of central Anatolia, Turkey. It comprises two sequences of domes and pyroclastic rocks with eruption ages of ∼150–200 ka (eastern group) and ∼20–25 ka (western group). Compositionally, the eastern rhyolite group lavas are less evolved (SiO₂ = 74–76 wt%), whereas the western group has higher silica abundance (SiO₂ = ∼77 wt%) with extremely depleted feldspar-compatible trace elements. Within each group, compositional variability is small and ¹⁴³Nd/¹⁴⁴Nd (0.51257–0.51265) and Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.87–18.88, ²⁰⁷Pb/²⁰⁴Pb = 15.65–15.67 and ²⁰⁸Pb/²⁰⁴Pb = 38.94–38.98) are homogeneous. The western group rhyolites have δ¹⁸O(zircon) overlapping mantle values (5.7 ± 0.2%), whereas eastern group rhyolites are enriched in d18O by ∼ 0.5%, consistent with a tendency to lower εNd values. By contrast, western group rhyolites have markedly more radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.7065–0.7091) compared to those of the eastern group (0.7059–0.7065). The presence of angular granitic xenoliths and a correlation between hydration (based on loss on ignition data) and ⁸⁷Sr/⁸⁶Sr in the western lavas, however, indicates that Sr was added during the eruption or posteruption alteration. Isotope constraints preclude the possibility that the rhyolite magmas formed by partial melting of any known regional crystalline basement rocks. Basalts and andesites erupted in the periphery of the Acigöl field are characterised by ⁸⁷Sr/⁸⁶Sr ratios between 0.7040 and 0.7053, ¹⁴³Nd/¹⁴⁴Nd = 0.51259–0.51300, ²⁰⁶Pb/²⁰⁴Pb = 18.85– 18.87, ²⁰⁷Pb/²⁰⁴Pb = 15.646–15.655, ²⁰⁸Pb/²⁰⁴Pb =38.90–38.97. The isotopic and trace element data favour an origin of the rhyolites by mixing of basaltic/andesitic magmas with minor amounts of crustal melts and followed by extensive fractional crystallization.

text: Zircon response to high-grade metamorphism as revealed by U–Pb and cathodoluminescence studies The Acigöl rhyolite field erupted the most recent high-silica rhyolites within the Cappadocian Volcanic Province of central Anatolia, Turkey. It comprises two sequences of domes and pyroclastic rocks with eruption ages of ∼150–200 ka (eastern group) and ∼20–25 ka (western group). Compositionally, the eastern rhyolite group lavas are less evolved (SiO₂ = 74–76 wt%), whereas the western group has higher silica abundance (SiO₂ = ∼77 wt%) with extremely depleted feldspar-compatible trace elements. Within each group, compositional variability is small and ¹⁴³Nd/¹⁴⁴Nd (0.51257–0.51265) and Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.87–18.88, ²⁰⁷Pb/²⁰⁴Pb = 15.65–15.67 and ²⁰⁸Pb/²⁰⁴Pb = 38.94–38.98) are homogeneous. The western group rhyolites have δ¹⁸O(zircon) overlapping mantle values (5.7 ± 0.2%), whereas eastern group rhyolites are enriched in d18O by ∼ 0.5%, consistent with a tendency to lower εNd values. By contrast, western group rhyolites have markedly more radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.7065–0.7091) compared to those of the eastern group (0.7059–0.7065). The presence of angular granitic xenoliths and a correlation between hydration (based on loss on ignition data) and ⁸⁷Sr/⁸⁶Sr in the western lavas, however, indicates that Sr was added during the eruption or posteruption alteration. Isotope constraints preclude the possibility that the rhyolite magmas formed by partial melting of any known regional crystalline basement rocks. Basalts and andesites erupted in the periphery of the Acigöl field are characterised by ⁸⁷Sr/⁸⁶Sr ratios between 0.7040 and 0.7053, ¹⁴³Nd/¹⁴⁴Nd = 0.51259–0.51300, ²⁰⁶Pb/²⁰⁴Pb = 18.85– 18.87, ²⁰⁷Pb/²⁰⁴Pb = 15.646–15.655, ²⁰⁸Pb/²⁰⁴Pb =38.90–38.97. The isotopic and trace element data favour an origin of the rhyolites by mixing of basaltic/andesitic magmas with minor amounts of crustal melts and followed by extensive fractional crystallization.

year: 2012

title: Correlations Between a Cyanobacteria Bloom's Decline and Environmental Dynamics.

authors: O'Rorke, Richard

subjects: cayanobacteria

abstract: Lake Kainui is an ombrogenous peat lake that is eutrophic and has frequent cyanobacterial blooms.  This research aimed to elucidate the factors that correlated with cyanobacterial bloom decline in Lake Kainui.  Abiotic and biotic variables in Lake Kainui were monitored weekly across the bloom decline phase.  Physicochemical parameters measured included nutrients, micronutrients, water temperature, dissolved oxygen (DO), pH and meteorological variables.  Planktonic and particle-associated bacterial community composition (BCC) was assessed through time using molecular fingerprinting (ARISA).  Total algal, cyanobacterial, planktonic bacteria, planktonic viruses and planktonic crustacean abundances were determined using microscopy.

The bloom decline coincided with multiple factors including; an increasing ratio of TN:TP, changes in the ratio of mixing depth (z¬mix) to euphotic depth (zeu) and pH.  The lake was stratified for several weeks before the decline and the resulting lake stability potentially created an adverse environment for cyanobacterial dominance.  Changes in planktonic biota were various.  Virus dynamics were positively correlated with phytoplankton dynamics.  If virus abundance was negatively correlated to phytoplankton diversity, it would potentially mean that viruses were controlling the phytoplankton assemblage, however virus abundance was positively correlated to phytoplankton diversity, which suggests that viruses had a positive impact on the bloom.  The positive effect was most likely due to to viruses upregulating the amount of dissolved organic matter through lysis.  Bacterial abundance showed no clear correlation with other variables, but bacterial community composition (BCC) shifted as the bloom declined.  Planktonic Cladocera spiked just after the bloom decline.  Bosmina was the dominant species of Cladocera, but was probably too small to ingest colonial Microcystis, which suggests that the Bosmina may be consuming degradation products produced by Microcystis.  These observations indicate that if planktonic biota played a role in bloom dynamics it was most likely due to shifts in the biota causing shifts in trophic cycling that alternately favour or disfavour blooming.

text: Correlations Between a Cyanobacteria Bloom's Decline and Environmental Dynamics. Lake Kainui is an ombrogenous peat lake that is eutrophic and has frequent cyanobacterial blooms.  This research aimed to elucidate the factors that correlated with cyanobacterial bloom decline in Lake Kainui.  Abiotic and biotic variables in Lake Kainui were monitored weekly across the bloom decline phase.  Physicochemical parameters measured included nutrients, micronutrients, water temperature, dissolved oxygen (DO), pH and meteorological variables.  Planktonic and particle-associated bacterial community composition (BCC) was assessed through time using molecular fingerprinting (ARISA).  Total algal, cyanobacterial, planktonic bacteria, planktonic viruses and planktonic crustacean abundances were determined using microscopy.

The bloom decline coincided with multiple factors including; an increasing ratio of TN:TP, changes in the ratio of mixing depth (z¬mix) to euphotic depth (zeu) and pH.  The lake was stratified for several weeks before the decline and the resulting lake stability potentially created an adverse environment for cyanobacterial dominance.  Changes in planktonic biota were various.  Virus dynamics were positively correlated with phytoplankton dynamics.  If virus abundance was negatively correlated to phytoplankton diversity, it would potentially mean that viruses were controlling the phytoplankton assemblage, however virus abundance was positively correlated to phytoplankton diversity, which suggests that viruses had a positive impact on the bloom.  The positive effect was most likely due to to viruses upregulating the amount of dissolved organic matter through lysis.  Bacterial abundance showed no clear correlation with other variables, but bacterial community composition (BCC) shifted as the bloom declined.  Planktonic Cladocera spiked just after the bloom decline.  Bosmina was the dominant species of Cladocera, but was probably too small to ingest colonial Microcystis, which suggests that the Bosmina may be consuming degradation products produced by Microcystis.  These observations indicate that if planktonic biota played a role in bloom dynamics it was most likely due to shifts in the biota causing shifts in trophic cycling that alternately favour or disfavour blooming.

year: 2009

title: Kaupapa Māori research- Some Kaupapa Māori principles

authors: Smith, Linda Tuhiwai

abstract: This paper was first presented at a conference of Māori academic staff at Massey University in 1996. It predates the publication of Decolonising Methodologies in 1998. You will note that since this paper was first presented our understandings and experiences in using Kaupapa Māori have deepened and we have significant capacity in Kaupapa Māori research. In 1996 there were many topics we could not imagine in depth as we had not completed the work to realise the potential of Kaupapa Māori. Also, our thinking was tentative and we were searching for the pathways to research that made sense in Māori ways. In looking back on the paper I can see my own naïve explorations into ideas that I thought were important. I have resisted the urge to rewrite this paper entirely as I think it stands as a good historical moment of where we were and where we are now. It needs to be read in the context of the 1990s.

text: Kaupapa Māori research- Some Kaupapa Māori principles This paper was first presented at a conference of Māori academic staff at Massey University in 1996. It predates the publication of Decolonising Methodologies in 1998. You will note that since this paper was first presented our understandings and experiences in using Kaupapa Māori have deepened and we have significant capacity in Kaupapa Māori research. In 1996 there were many topics we could not imagine in depth as we had not completed the work to realise the potential of Kaupapa Māori. Also, our thinking was tentative and we were searching for the pathways to research that made sense in Māori ways. In looking back on the paper I can see my own naïve explorations into ideas that I thought were important. I have resisted the urge to rewrite this paper entirely as I think it stands as a good historical moment of where we were and where we are now. It needs to be read in the context of the 1990s.

year: 2015