Nutrient dynamics in the Archean-Paleoproterozoic oceans strongly influenced primary productivity and the rise of atmospheric O2. Reconstructing the cycling of key nutrients such as dissolved inorganic phosphate (DIP) at this time is important for our understanding of the timing, rate and extent of atmospheric oxygenation at this time. Banded iron formations (BIF) can be used as proxies for global DIP content in Precambrian marine waters. Estimating Precambrian DIP requires understanding of the mechanisms by which Fe(III)(oxyhydr)oxides scavenge DIP which has come mainly from experimental studies using NaCl solutions that mimick Precambrian marine conditions with for example, elevated Si and Fe(II) concentrations. The two DIP binding modes suggested for Early Proterozoic marine waters are 1) Adsorption - surface attachment on pre-formed Fe(III) (oxyhydr)oxides, and 2) Coprecipitation - incorporation of P into actively growing Fe(III) (oxyhydr)oxides. It has been suggested that the elevated Si concentrations suggested for Precambrian seawater, strongly inhibit adsorption of DIP in Fe(III)(oxyhydr)oxides. However recent coprecipitation experiments show that DIP is strongly scavenged by Fe(III)(oxyhydr)oxides in the presence of Si, seawater cations and hydrothermal As. In this study we show that the DIP uptake onto Fe(III)(oxyhydr)oxides by adsorption is less than 5% of that by coprecipitation. The data imply that in the Early Proterozoic open oceans, the precipitation of Fe(III)(oxyhydr)oxides during mixing of deep anoxic Fe(II)-rich waters with oxygenated ocean surface waters caused DIP removal from surface waters through coprecipitation rather than adsorption. Local variations in DIP and perhaps even stratification of DIP in the oceans were likely created from the continuous removal of DIP from surface waters by Fe(III)(oxyhydr)oxides, and its partial release into the anoxic bottoms waters and in buried sediments. In addition to a DIP famine, the selectivity for DIP over As(V) may have led to As enrichment in surface waters both of which would have most likely decreased the productivity of Cyanobacteria and O2 production. / Näringscirkulationen i haven under arkeikum och paleoproterozoikum påverkade primärproduktionen och uppkomsten av atmosfärisk syrgas (O2). För att förstå när och hur fort koncentrationen av O2 i atmosfären ökade behöver vi rekonstruera hur viktiga näringsämnen, t.ex. löst oorganiskt fosfor (engelska “Dissolved Inorganic Phosphorous”, DIP) cirkulerade. Bandad järnmalm (engelska “Banded Iron Formations”, BIF) kan användas som en markör för DIP i de prekambriska haven. För att kunna använda DIP som markör måste man förstå hur prekambrisk DIP tas upp av järn(III)(oxyhydr)oxider. Hittills har detta studerats med natriumkloridlösningar som ska efterlikna förhållande i de prekambriska haven, med t.ex. förhöjda kisel- och järn(II)-koncentrationer. Ur sådana studier har två bindningsmekanismer föreslagits för paleoproterozoiskt havsvatten 1) Adsorption, d.v.s. DIP binds till ytan på redan bildade kristaller av järn(III)(oxyhydr)oxid, och 2) samutfällning, d.v.s. upptag av fosfor i kristaller av järn(III)(oxyhydr)oxid medan kristallerna bildas. Det har föreslagits att de höga kiselkoncentrationerna som tros ha funnits i de prekambriska havsvattnet hämmade adsorption av DIP på ytan av järn(III) (oxyhydr)oxidkristaller. Men de senaste samutfällningsexperimenten tyder på att järn(III) (oxyhydr)oxid effektivt tar upp DIP även i närvaro av kisel, arsenik från hydrotermala källor och de katjoner som dominerar i havsvatten. I här presenterad studie var mängden DIP som bands till järn(III)(oxyhydr)oxidkristaller genom adsorption mindre än 5 % av den DIP som togs upp av kristallerna via samutfällning. Våra data tyder på att när järn(III) (oxyhydr)oxid fälldes ut i tidiga-proterozoiska hav när järn(II)-rikt djupvatten blandades med syrerikt ytvatten, och att DIP avlägsnades från ytvattnet genom samutfällning snarare än adsorption. Lokala variationer av DIP-koncentrationer i haven, möjligen även skiktning, kan ha orsakats av kontinuerlig utfällning av järn(III)(oxyhydr)oxider ur ytvattnet följt av partiell frigörelse av DIP i syrefria djupvatten och sediment. Kristallisationsprocessen, som gynnar inbindning av DIP och misgynnar inbinding av arsenik (V) kan ha orsakat brist av DIP och anrikning av arsenik i ytvattnet, vilket troligen minskade tillväxten av cyanobakterier med lägre syrgasproduktion som följd. / CLAPO

<P> Detailed Nd isotopic mapping in the southwestern Grenville Province between North Bay, Ontario, and Temiscaming, Quebec has revealed the precise trend of the proposed Penokean-aged suture discovered during reconnaissance isotopic mapping by Dickin and McNutt (1989). </p> <p> Lithotectonic domains proposed by Easton (1989} for the greater North Bay area are cross-cut by the suture. As presently located, the Tilden-Tomiko domain boundary effects no apparent offset of the suture which would be expected during low angle differential Grenville thrusting. Although a lack of apparent offset suggests these domains are not significant Grenville structures a definitive answer must await more precise mapping of their boundaries. There appears to be some potential for unravelling aspects of Grenville tectonism through such cross-cutting relationships. </p> <p> In the North Bay-Temiscaming area the full model age transition from ca 1.90 Ga to ca 2.70 Ga is negotiated in stepwise fashion through metasediments of intermediate Nd model age spanning an area from a few kilometers to a few tens of kilometers in width. This suggests the suture boundary is better described as a suture zone. Presently two groups of intermediate aged metasediments are recognized (1} a 2.00-2.39 Ga group and ( 2) a 2. 40-2.60 Ga group. These age groups correspond to rocks of two different lithologies separated along strike of the suture in the Temiscaming and North Bay areas respectively. Although the ages of metasediments comprising the suture zone more or less spans the entire interval between 1.90 and 2.70 Ga, there is no well defined transect wherein the whole range of intermediate aged crust is recorded within a single rock type. Therefore a 'splitting' rather than 'lumping' approach is deemed justified for the intermediate aged crust until provenance studies using zircons can be undertaken to show in a definitive manner whether or not the two groups are related in a genetic sense. </p> <p> The absence of plutonism with crystallization ages between 2.00 and 2.60 Ga in the North Bay-Temiscaming area suggests that metasediments of the suture zone acquired their model age from sedimentological mixing between crust of Archean (ca 2.70 Ga) and Proterozoic (ca 1.90 Ga) provenance. The arrangement of mixed provenance metasediments coincident with the suture suggests a genetic relationship. It is proposed that the mixed provenance metasediments are part of a foreland basin assemblage which formed in response to downloading of the cratonal edge by the combined effect of an overriding island arc and the attempted subduction of the Superior craton. </p> <p> Major element analyses show that mixed provenance and arc derived sediments of the proposed foreland basin display a wide range in their maturity. This is consistent with the foreland basin environment where sediments can be reworked to varying degrees in response to tectonically controlled local sea level fluctuations. Contrasting the dynamic environment of the foreland basin the belt of Archean crust north of the suture with model ages of ca 2.72 Ga shows a very restricted range of reworking implying a uniform depositionary environment e.g., deep water passive margin. </p> <p> North of the field area a lobe of Archean crust extends into the Grenville Province, anchored by the Pontiac Group on the northern margin of the Grenville Front (GF), and consisting in part of the parautocthonous Red Cedar Lake Gneiss south of the GF. The full expression of the Archean lobe within the Grenville Province and north of the North Bay Temiscaming field area is unknown, however, preliminary results from Nd isotopic mapping suggest that Archean crust between the suture and the Grenville Front Tectonic Zone (GFTZ) may be part of, or, derived from this Archean parautocthonous lobe. Archean provenance crust north of the field area defines a relatively homogeneous belt of crust with ca 2.72 Ga model ages and a whole rock Sm-Nd isochron age of 2.77 Ga. This is in sharp contrast to the heterogeneity of model ages displayed by Archean crust further west, between the suture (French River area) and the Grenville Front near Sudbury, Ontario (Dickin et al., 1989). Here, the Archean foreland may owe its peculiar heterogeneity to mixing between 2. 72 Ga crust and 2. 4 Ga Huronian volcanics andjor 1. 7 Ga Kilarnian juvenile crust (Dickin et al., 1990). Evidence for the presence of these crustal endmembers in the North Bay Temiscaming area is lacking. </p> <p> Finally, the presence of a suture zone consisting of mixed provenance metasediments is the best evidence yet in support of the suture hypothesis explanation for the model age transition as opposed to juxtaposition of two crustal age domains by Grenville thrusting. </p> / Thesis / Bachelor of Science (BSc)

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No description available.

Bibliography: leaves [206]-244.

Bibliography: leaves [206]-244. / xxviii, 244 leaves, [31] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 2001

Bibliography: leaves [206]-244. / xxviii, 244 leaves, [31] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 2001

No description available.

The importance of the Musgrave Province in continental reconstructions of Proterozoic Australia is only beginning to be appreciated. The Mesoproterozoic Musgrave Province sits in a geographically central location within Australia and is bounded by older and more isotopically evolved regions including the Gawler Craton of South Australia and Arunta Region of the Northern Territory. Understanding the crustal growth and deformation mechanisms involved in the formation of the Musgrave Province, and also the nature of the basement that separates these tectonic elements, allows for greater insight into defining the timing and processes responsible for the amalgamation of Proterozoic Australia. The ca. 1.60-1.54 Ga Musgravian Gneiss preserves geochemical and isotopic signatures related to ongoing arc-magmatism in an active margin between the North Australian and South Australian Cratons (NAC and SAC). Characteristic geochemical patterns of the Musgravian Gneiss include negative anomalies in Nb, Ti, and Y, and are accompanied by steep LREE patterns. Also characteristic of the Musgravian Gneiss is its juvenile Nd isotopic composition (ɛNd1.55 values from -1.2 to +0.9). The juvenile isotopic signature of the Musgravian Gneiss separates it from the bounding comparitively isotopically evolved terranes of the Arunta Region and Gawler Craton. The geochemical and isotopic signatures of these early Mesoproterozoic felsic rocks have similarities with island arc systems involving residual Ti-bearing minerals and garnet. Circa 1.40 Ga metasedimentary rocks of the eastern Musgrave Province also record vital evidence for determining Australia.s location and fit within a global plate reconstruction context during the late Mesoproterozoic. U-Pb detrital zircon and Sm-Nd isotopic data from these metasedimentary rocks suggests a component of derivation from sources outside of the presently exposed Australian crust. Best fit matches come from rocks originating from eastern Laurentia. Detrital zircon ages range from Palaeoproterozoic to late Mesoproterozoic, constraining the maximum depositional age of the metasediments to approximately 1.40 Ga, similar to that of the Belt Supergroup in western Laurentia. The 1.49-1.36 Ga detrital zircons in the Musgrave metasediments are interpreted to have been derived from the voluminous A-type suites of Laurentia, as this time period represents a “magmatic gap” in Australia, with an extreme paucity of sources this age recognized. The metasedimentary rocks exhibit a range of Nd isotopic signatures, with ɛNd(1.4 Ga) values ranging from -5.1 to 0.9, inconsistent with complete derivation from Australian sources, which are more isotopically evolved. The isotopically juvenile ca. 1.60-1.54 Ga Musgravian Gneiss is also an excellent candidate for the source of the abundant ca. 1.6-1.54 Ga detrital zircons within the lower sequences of the Belt Supergroup. If these interpretations are correct, they support a palaeogeographic reconstruction involving proximity of Australia and Laurentia during the pre-Rodinia Mesoproterozoic. This also increases the prospectivity of the eastern Musgrave Province to host a metamorphised equivalent of the massive Pb-Zn-Ag Sullivan deposit. The geochemical and isotopic signatures recorded in mafic-ultramafic rocks can divulge important information regarding the state of the sub continental lithospheric mantle (SCLM). The voluminous cumulate mafic-ultramafic rocks of the ca. 1.08 Ga Giles Complex record geochemical and Nd-Sr isotopic compositions consistent with an enriched parental magma. Traverses across three layered intrusions, the Kalka, Ewarara, and Gosse Pile were geochemically and isotopically analysed. Whole rock samples display variably depleted to enriched LREE patterns when normalised to chondrite ((La/Sm)N = 0.43-4.72). Clinopyroxene separates display similar depleted to enriched LREE patterns ((La/Sm)N = 0.37-7.33) relative to a chondritic source. The cumulate rocks display isotopically evolved signatures (ɛNd ~-1.0 to .5.0 and ɛSr ~19.0 to 85.0). Using simple bulk mixing and AFC equations, the Nd-Sr data of the more radiogenic samples can be modelled by addition of ~10% average Musgrave crust to a primitive picritic source, without need for an enriched mantle signature. Shallow decompressional melting of an asthenospheric plume source beneath thinned Musgravian lithosphere is envisaged as a source for the parental picritic magma. A model involving early crustal contamination within feeder zones is favoured, and consequently explorers looking for Ni-Cu-Co sulphides should concentrate on locating these feeder zones. Few absolute age constraints exist for the timing of the intracratonic Petermann Orogeny of the Musgrave Province. The Petermann Orogeny is responsible for much of the lithospheric architecture we see today within the Musgrave Province, uplifting and exhuming large parts along crustal scale E-W trending fault/shear systems. Isotopic and geochemical analysis of a suite of stratigraphic units within the Neoproterozoic to Cambrian Officer Basin to the immediate south indicate the development of a foreland architecture at ca. 600 Ma. An excursion in ɛNd values towards increasingly less negative values at this time is interpreted as representing a large influx of Musgrave derived sediments. Understanding the nature of the basement separating the SAC from the NAC and WAC is vital in constructing models of the amalgamation of Proterozoic Australia. This region is poorly understood as it is overlain by the thick sedimentary cover of the Officer Basin. However, the Coompana Block is one place where basement is shallow enough to be intersected in drillcore. The previously geochronologically, geochemically, and isotopically uncharacterised granitic gneiss of the Coompana Block represents an important period of within-plate magmatism during a time of relative magmatic quiescence in the Australian Proterozoic. U-Pb LA-ICPMS dating of magmatic zircons provides an age of ca. 1.50 Ga, interpreted as the crystallisation age of the granite protolith. The samples have distinctive A-type chemistry characterised by high contents of Zr, Nb, Y, Ga, LREE with low Mg#, Sr, CaO and HREE. ɛNd values are high with respect to surrounding exposed crust of the Musgrave Province and Gawler Craton, and range from +1.2 to +3.3 at 1.5 Ga. The tectonic environment into which the granite was emplaced is also unclear, however one possibility is emplacement within an extensional environment represented by interlayered basalts and arenaceous sediments of the Coompana Block. Regardless, the granitic gneiss intersected in Mallabie 1 represents magmatic activity during the “Australian magmatic gap” of ca. 1.52-1.35 Ga, and is a possible source for detrital ca. 1.50 zircons found within sedimentary rocks of Tasmania and Antarctica, and metasedimentary rocks of the eastern Musgrave Province. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1261003 / Thesis(PhD)-- University of Adelaide, School of Earth and Environmental Sciences, 2006

The importance of the Musgrave Province in continental reconstructions of Proterozoic Australia is only beginning to be appreciated. The Mesoproterozoic Musgrave Province sits in a geographically central location within Australia and is bounded by older and more isotopically evolved regions including the Gawler Craton of South Australia and Arunta Region of the Northern Territory. Understanding the crustal growth and deformation mechanisms involved in the formation of the Musgrave Province, and also the nature of the basement that separates these tectonic elements, allows for greater insight into defining the timing and processes responsible for the amalgamation of Proterozoic Australia. The ca. 1.60-1.54 Ga Musgravian Gneiss preserves geochemical and isotopic signatures related to ongoing arc-magmatism in an active margin between the North Australian and South Australian Cratons (NAC and SAC). Characteristic geochemical patterns of the Musgravian Gneiss include negative anomalies in Nb, Ti, and Y, and are accompanied by steep LREE patterns. Also characteristic of the Musgravian Gneiss is its juvenile Nd isotopic composition (ɛNd1.55 values from -1.2 to +0.9). The juvenile isotopic signature of the Musgravian Gneiss separates it from the bounding comparitively isotopically evolved terranes of the Arunta Region and Gawler Craton. The geochemical and isotopic signatures of these early Mesoproterozoic felsic rocks have similarities with island arc systems involving residual Ti-bearing minerals and garnet. Circa 1.40 Ga metasedimentary rocks of the eastern Musgrave Province also record vital evidence for determining Australia.s location and fit within a global plate reconstruction context during the late Mesoproterozoic. U-Pb detrital zircon and Sm-Nd isotopic data from these metasedimentary rocks suggests a component of derivation from sources outside of the presently exposed Australian crust. Best fit matches come from rocks originating from eastern Laurentia. Detrital zircon ages range from Palaeoproterozoic to late Mesoproterozoic, constraining the maximum depositional age of the metasediments to approximately 1.40 Ga, similar to that of the Belt Supergroup in western Laurentia. The 1.49-1.36 Ga detrital zircons in the Musgrave metasediments are interpreted to have been derived from the voluminous A-type suites of Laurentia, as this time period represents a “magmatic gap” in Australia, with an extreme paucity of sources this age recognized. The metasedimentary rocks exhibit a range of Nd isotopic signatures, with ɛNd(1.4 Ga) values ranging from -5.1 to 0.9, inconsistent with complete derivation from Australian sources, which are more isotopically evolved. The isotopically juvenile ca. 1.60-1.54 Ga Musgravian Gneiss is also an excellent candidate for the source of the abundant ca. 1.6-1.54 Ga detrital zircons within the lower sequences of the Belt Supergroup. If these interpretations are correct, they support a palaeogeographic reconstruction involving proximity of Australia and Laurentia during the pre-Rodinia Mesoproterozoic. This also increases the prospectivity of the eastern Musgrave Province to host a metamorphised equivalent of the massive Pb-Zn-Ag Sullivan deposit. The geochemical and isotopic signatures recorded in mafic-ultramafic rocks can divulge important information regarding the state of the sub continental lithospheric mantle (SCLM). The voluminous cumulate mafic-ultramafic rocks of the ca. 1.08 Ga Giles Complex record geochemical and Nd-Sr isotopic compositions consistent with an enriched parental magma. Traverses across three layered intrusions, the Kalka, Ewarara, and Gosse Pile were geochemically and isotopically analysed. Whole rock samples display variably depleted to enriched LREE patterns when normalised to chondrite ((La/Sm)N = 0.43-4.72). Clinopyroxene separates display similar depleted to enriched LREE patterns ((La/Sm)N = 0.37-7.33) relative to a chondritic source. The cumulate rocks display isotopically evolved signatures (ɛNd ~-1.0 to .5.0 and ɛSr ~19.0 to 85.0). Using simple bulk mixing and AFC equations, the Nd-Sr data of the more radiogenic samples can be modelled by addition of ~10% average Musgrave crust to a primitive picritic source, without need for an enriched mantle signature. Shallow decompressional melting of an asthenospheric plume source beneath thinned Musgravian lithosphere is envisaged as a source for the parental picritic magma. A model involving early crustal contamination within feeder zones is favoured, and consequently explorers looking for Ni-Cu-Co sulphides should concentrate on locating these feeder zones. Few absolute age constraints exist for the timing of the intracratonic Petermann Orogeny of the Musgrave Province. The Petermann Orogeny is responsible for much of the lithospheric architecture we see today within the Musgrave Province, uplifting and exhuming large parts along crustal scale E-W trending fault/shear systems. Isotopic and geochemical analysis of a suite of stratigraphic units within the Neoproterozoic to Cambrian Officer Basin to the immediate south indicate the development of a foreland architecture at ca. 600 Ma. An excursion in ɛNd values towards increasingly less negative values at this time is interpreted as representing a large influx of Musgrave derived sediments. Understanding the nature of the basement separating the SAC from the NAC and WAC is vital in constructing models of the amalgamation of Proterozoic Australia. This region is poorly understood as it is overlain by the thick sedimentary cover of the Officer Basin. However, the Coompana Block is one place where basement is shallow enough to be intersected in drillcore. The previously geochronologically, geochemically, and isotopically uncharacterised granitic gneiss of the Coompana Block represents an important period of within-plate magmatism during a time of relative magmatic quiescence in the Australian Proterozoic. U-Pb LA-ICPMS dating of magmatic zircons provides an age of ca. 1.50 Ga, interpreted as the crystallisation age of the granite protolith. The samples have distinctive A-type chemistry characterised by high contents of Zr, Nb, Y, Ga, LREE with low Mg#, Sr, CaO and HREE. ɛNd values are high with respect to surrounding exposed crust of the Musgrave Province and Gawler Craton, and range from +1.2 to +3.3 at 1.5 Ga. The tectonic environment into which the granite was emplaced is also unclear, however one possibility is emplacement within an extensional environment represented by interlayered basalts and arenaceous sediments of the Coompana Block. Regardless, the granitic gneiss intersected in Mallabie 1 represents magmatic activity during the “Australian magmatic gap” of ca. 1.52-1.35 Ga, and is a possible source for detrital ca. 1.50 zircons found within sedimentary rocks of Tasmania and Antarctica, and metasedimentary rocks of the eastern Musgrave Province. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1261003 / Thesis(PhD)-- University of Adelaide, School of Earth and Environmental Sciences, 2006