title: A fluid flow perspective on the diagenesis of Te Aute limestones

authors: Ricketts, Brian D.

subjects: diagenesis

abstract: Pliocene cool-water, bioclastic Te Aute limestones in East Coast Basin, New Zealand, accumulated either in shelfal shoal areas or about structurally shallow growth fold structures in the tectonically active accretionary forearc prism. Up to five stages of carbonate cementation are recognised, based on cement sequence-stratigraphic concepts, that formed on the seafloor during exposure of the limestones before burial, during burial, uplift, and deformation. Two principal fluid types are identified--topography-driven meteoric fluids and compaction-driven fluids. We have developed conceptual and quantitative models that attempt to relate the physical characteristics of fluid flow to the cement paragenesis. In particular, we have simulated the effects of uplift of the axial ranges bordering East Coast Basin in terms of the degree of penetration of a meteoric wedge into the basin. The dynamics of meteoric flow changed dramatically during uplift over the last 2 m.y. such that the modelled extent of the meteoric wedge is at least 40 km across the basin, and the penetration depth 1500 m or more corresponding with measured freshwater intersections in some oil wells. Cement-fluid relationships include: (1) true marine cements that precipitated in areas remote from shallow freshwater lenses; (2) pre-compaction cements that formed in shallow freshwater lenses beneath limestone "islands"; (3) post-compaction cements derived from compaction-driven flow during burial; (4) early uplift-related fracture-fill cements formed during deformation of the accretionary prism and uplift of the axial ranges; and (5) late uplift-related cements associated with uplift into a shallow meteoric regime.

text: A fluid flow perspective on the diagenesis of Te Aute limestones Pliocene cool-water, bioclastic Te Aute limestones in East Coast Basin, New Zealand, accumulated either in shelfal shoal areas or about structurally shallow growth fold structures in the tectonically active accretionary forearc prism. Up to five stages of carbonate cementation are recognised, based on cement sequence-stratigraphic concepts, that formed on the seafloor during exposure of the limestones before burial, during burial, uplift, and deformation. Two principal fluid types are identified--topography-driven meteoric fluids and compaction-driven fluids. We have developed conceptual and quantitative models that attempt to relate the physical characteristics of fluid flow to the cement paragenesis. In particular, we have simulated the effects of uplift of the axial ranges bordering East Coast Basin in terms of the degree of penetration of a meteoric wedge into the basin. The dynamics of meteoric flow changed dramatically during uplift over the last 2 m.y. such that the modelled extent of the meteoric wedge is at least 40 km across the basin, and the penetration depth 1500 m or more corresponding with measured freshwater intersections in some oil wells. Cement-fluid relationships include: (1) true marine cements that precipitated in areas remote from shallow freshwater lenses; (2) pre-compaction cements that formed in shallow freshwater lenses beneath limestone "islands"; (3) post-compaction cements derived from compaction-driven flow during burial; (4) early uplift-related fracture-fill cements formed during deformation of the accretionary prism and uplift of the axial ranges; and (5) late uplift-related cements associated with uplift into a shallow meteoric regime.

year: 2004-12-01

title: Thiourea monoanion and dianion complexes of rhodium(III) and ruthenium(II)

authors: Henderson, William

subjects: Crystal structures

abstract: The versatility of deprotonated thioureas as ligands is shown by the synthesis and characterisation of a range of rhodium(III) complexes of substituted thioureas, with support from a ruthenium(II) analogue in one case. Reaction of the complexes [LMCl(μ-Cl)]2 [M=Rh, L=η5-C5Me5 (Cp*); M=Ru, L=η6-p-cymene] with Na[MeNHC(S)NCN] and excess trimethylamine base gives the dinuclear complexes [LM{SC(=NCN)NMe}]2 containing chelate-bridging thiourea dianion ligands. The Ru complex was characterised by an X-ray diffraction study. The mononuclear complexes [Cp*Rh{SC(=NCN)NMe}(PPh3)] and [Cp*Rh{SC(=NPh)NPh}(PPh3)], containing chelating thiourea dianion ligands, were prepared by analogous reactions in the presence of triphenylphosphine. Reaction of [Cp*Rh{SC(=NCN)NMe}(PPh3)] with HCl, or [Cp*RhCl(μ-Cl)]2 with 2 equiv. of PPh3 and Na[MeNHC(S)NCN] (with no added base) gave the complex [Cp*RhCl{SC(=NCN)NHMe}(PPh3)], containing a (monodentate) S-bonded thiourea monoanion ligand, which was characterised by an X-ray diffraction study. The AsPh3 and SbPh3 analogues of this complex were also prepared and characterised. Reaction of [Cp*RhCl(μ-Cl)]2 with 2 equiv. of PPh3 or SbPh3 and PhNHC(S)NHPh or various trisubstituted thioureas PhNHC(S)NR1R2, triethylamine and NaBPh4 gave a range of cationic complexes [Cp*Rh{SC(=NR1R2)NPh}(EPh3)]+ (E=P, Sb), as their tetraphenylborate salts, in which the thiourea is bonded as a monoanion through the S and the NPh group. The corresponding reaction utilising 1,6-bis(diphenylphosphino)hexane (dpph) gave the dinuclear complex [Cp*Rh{SC(=N(CH2CH2)2O)NPh}]2(μ-η2-dpph) (BPh4)2.

text: Thiourea monoanion and dianion complexes of rhodium(III) and ruthenium(II) The versatility of deprotonated thioureas as ligands is shown by the synthesis and characterisation of a range of rhodium(III) complexes of substituted thioureas, with support from a ruthenium(II) analogue in one case. Reaction of the complexes [LMCl(μ-Cl)]2 [M=Rh, L=η5-C5Me5 (Cp*); M=Ru, L=η6-p-cymene] with Na[MeNHC(S)NCN] and excess trimethylamine base gives the dinuclear complexes [LM{SC(=NCN)NMe}]2 containing chelate-bridging thiourea dianion ligands. The Ru complex was characterised by an X-ray diffraction study. The mononuclear complexes [Cp*Rh{SC(=NCN)NMe}(PPh3)] and [Cp*Rh{SC(=NPh)NPh}(PPh3)], containing chelating thiourea dianion ligands, were prepared by analogous reactions in the presence of triphenylphosphine. Reaction of [Cp*Rh{SC(=NCN)NMe}(PPh3)] with HCl, or [Cp*RhCl(μ-Cl)]2 with 2 equiv. of PPh3 and Na[MeNHC(S)NCN] (with no added base) gave the complex [Cp*RhCl{SC(=NCN)NHMe}(PPh3)], containing a (monodentate) S-bonded thiourea monoanion ligand, which was characterised by an X-ray diffraction study. The AsPh3 and SbPh3 analogues of this complex were also prepared and characterised. Reaction of [Cp*RhCl(μ-Cl)]2 with 2 equiv. of PPh3 or SbPh3 and PhNHC(S)NHPh or various trisubstituted thioureas PhNHC(S)NR1R2, triethylamine and NaBPh4 gave a range of cationic complexes [Cp*Rh{SC(=NR1R2)NPh}(EPh3)]+ (E=P, Sb), as their tetraphenylborate salts, in which the thiourea is bonded as a monoanion through the S and the NPh group. The corresponding reaction utilising 1,6-bis(diphenylphosphino)hexane (dpph) gave the dinuclear complex [Cp*Rh{SC(=N(CH2CH2)2O)NPh}]2(μ-η2-dpph) (BPh4)2.

year: 2002-10-01

title: Insecure, unpredictable, hoping to survive: Four cases of Māori people living precariously in Hamilton, Aotearoa New Zealand

authors: Uerata, Lynley Moana

subjects: Māori

abstract: A conceptualisation of precarity is introduced and adopted. A critique of contemporary conceptualisations of precarity is presented, drawing especially on Stuart Hall’s interpretation of articulation and Marx’s concept of relative surplus population. Much of the literature on precarity focusses on the neoliberal mode of contemporary capitalism originating in the late 1970s. However, there is limited literature which explores precarity as a way of life. A precarious way of life is characterised by interacting forms of precarity which embed insecurity, instability, and unpredictability in the everyday lives of real people. An account of the Māori experience of precarity since the pre-colonial era to the present-day is presented. Māori are the indigenous people of Aotearoa New Zealand who were colonised by the British Empire in the 1800s. 
The main research questions addressed in my thesis are: What forms of precarity are present in the everyday context? How do forms of precarity relate to each other? How do forms of precarity relate to being Māori? What kinds of support do those living with precarity gain from social structures, institutions, and social actors? What is the role of culture in the way Māori experience and mediate precarity? An analysis of semi-structured in-depth engagements with Māori people living precariously in Hamilton, Aotearoa New Zealand in 2016, based on four case studies, shows the character and significance of forms, sources, and effects of precarity in everyday life. As historical processes continue to overdetermine experiences of social structures and institutions in the present, in a contemporary capitalist context precarity arises from a wide range of interacting sources, forms, and effects of precarity. Among the different kinds of actors and organisations which comprise the support systems constructed to mediate precarity in the everyday context, cultural practices and resources can play a significant role for people who are culturally connected. When people are integrated into their local and cultural communities, they can cope better with a precarious way of life.

text: Insecure, unpredictable, hoping to survive: Four cases of Māori people living precariously in Hamilton, Aotearoa New Zealand A conceptualisation of precarity is introduced and adopted. A critique of contemporary conceptualisations of precarity is presented, drawing especially on Stuart Hall’s interpretation of articulation and Marx’s concept of relative surplus population. Much of the literature on precarity focusses on the neoliberal mode of contemporary capitalism originating in the late 1970s. However, there is limited literature which explores precarity as a way of life. A precarious way of life is characterised by interacting forms of precarity which embed insecurity, instability, and unpredictability in the everyday lives of real people. An account of the Māori experience of precarity since the pre-colonial era to the present-day is presented. Māori are the indigenous people of Aotearoa New Zealand who were colonised by the British Empire in the 1800s. 
The main research questions addressed in my thesis are: What forms of precarity are present in the everyday context? How do forms of precarity relate to each other? How do forms of precarity relate to being Māori? What kinds of support do those living with precarity gain from social structures, institutions, and social actors? What is the role of culture in the way Māori experience and mediate precarity? An analysis of semi-structured in-depth engagements with Māori people living precariously in Hamilton, Aotearoa New Zealand in 2016, based on four case studies, shows the character and significance of forms, sources, and effects of precarity in everyday life. As historical processes continue to overdetermine experiences of social structures and institutions in the present, in a contemporary capitalist context precarity arises from a wide range of interacting sources, forms, and effects of precarity. Among the different kinds of actors and organisations which comprise the support systems constructed to mediate precarity in the everyday context, cultural practices and resources can play a significant role for people who are culturally connected. When people are integrated into their local and cultural communities, they can cope better with a precarious way of life.

year: 2021