U th pb dating of phosphate minerals, introduction

  1. Nevertheless, what is astounding is that Dickson et al.
  2. Figures illustrate examples of the ore textures under the microscopes, the accompanying descriptions indicating how the textures have been interpreted.
  3. Perhaps this difference is a reflection of the extent of mixing in each type of sample at their respective levels in the weathering profile.
  4. While diverse, these fields are all linked structurally, crystal-chemically and geochemically.
  5. Similar anomalous or false isochrons are commonly obtained from U- Th-Pb data, which is hardly surprising given the common open system behaviour of the U- Th-Pb system.
  6. Hughes and John Rakovan, p.
U-Th-Pb Dating of Phosphate Minerals

The other four uraninite samples all lay well below concordia and did not conform to any regular linear array. The lower member is dominated by a thick basal dolomite and passes transitionally upwards into the psammitic upper member, which is largely feldspathic schist and quartzite. As has already been briefly noted, supergene alteration principally oxidation of uraninite has not only occurred where the zone of surficial weathering has intersected the top of the No. Geology of the Alligator Rivers Uranium Field. Analyses of iron and manganese oxides in fractures in the Koongarra primary ore.

Mineralogical Society of America - Phosphates

The net result has been the complete destruction of the uraninite in what was the top of the No. These were samples of drill core that had been crushed. Uraninite compositions in the ore are never uniform.

Open Research U-Th-Pb Dating of Phosphate Minerals

U th pb dating of phosphate minerals

The Mineralogy and Crystal Chemistry section concludes with a detailed examination of the crystal chemistry of other naturally-occurring phosphate phases and a listing of an additional minerals. Uranium mineralisation is only present where this alteration has taken place. Monazite and xenotime are highlighted in a fourth chapter, which includes their potential use as solid-state radioactive waste repositories. Galena is the most abundant, commonly occurring as cubes mm wide disseminated in uraninite or gangue, and as stringers and veinlets particularly filling thin fractures within uraninite.

U th pb dating of phosphate minerals

Some of these samples were again crushed drill core, but the majority were crushed percussion drill chips. Similarly, Cunningham et al. Within the primary ore zone this in situ replacement of uraninite is most pronounced immediately above the reverse fault breccia, and this alteration and oxidation diminish upwards stratigraphically. Much progress towards this goal has been, and is being, made within the relatively small creationist geological community.

The failure of U-Th-Pb dating at Koongarra Australia

U-Th-Pb Dating of Phosphate Minerals

The following two chapters treat the stable isotope and trace element compositions of modern and fossil biogenic phosphates, with applications to paleontology, paleoclimatology, and paleoecology. There are five main lines of independent evidence that the mineral-rock systems at Koongarra have been open to diffusion and migration of U, Th and daughter isotopes including Pb. Mark Harrison, Elizabeth J. Groups of uraninite veinlets are intimately intergrown with chlorite, which forms the matrix to the host breccias.


U th pb dating of phosphate minerals

Furthermore, Dickson et al. Oxidation and alteration of uraninite within the primary ore zone has produced a variety of secondary uranium minerals, principally uranyl silicates. Polyphase deformation accompanied metamorphism of the original sediments, that were probably dolomite, shales and siltstones.

It is accompanied by hematite staining of the schists, for the more intense hematite alteration in and near the reverse fault breccia being due to hematite replacement of chlorite. At Koongarra subsequent reverse faulting has juxtaposed the lower Cahill Formation schists and Kombolgie Formation sandstone. Hills and Richards were left with two possible interpretations. For this mixing explanation to be feasible there should be some other evidence of mobilisation of Pb in the area. Influences of the nature of the initial Rb-Sr system on isochron validity.


The highly speculative nature of all radiometric dating methods becomes apparent when one realizes that none of the above assumptions is either valid or provable. Phosphate minerals are an integral component of geological and biological systems. We hope all chapters in this volume encourage researchers to expand their work on all aspects of natural and synthetic phosphate compounds. In the Petrology section, three chapters detail the igneous, metamorphic, and sedimentary aspects of phosphate minerals.

  • Geochronology of hydrothermal uranium deposits and associated igneous rocks in the eastern source area of the Mount Belknap Volcanics, Marysvale, Utah.
  • Biomedical Application of Apatites by Karlis A.
  • The technique did in fact work, Pb isotopic traces of the deeply buried No.
  • Pb has likewise been mobile.
Canon (Schweiz) AG

Catlos, and Jean-Marc Montel, p. Uraninite and its alteration products, Koongarra uranium deposit. Put simply, none of these assumptions can have been observed to have always been true throughout the supposed millions of years the radioactive elements have presumed to have been decaying. As geoscientists turn their attention to the intersection of the biological, geological, and material science realms, there is no group of compounds more germane than the phosphates. Their isotopic data on four samples were plotted on a U-Pb isochron diagram and indicated a non-systematic relationship between the U parent and the Pb daughter.

Dating Someone New After A Breakup U Th Pb Dating Of Phosphate Minerals

Chlorite, predominantly magnesium chlorite, is the principal gangue, and its intimate association with the uraninite indicates that the two minerals formed together. Pb is also prone to diffusion from minerals. The Rn gas is known to migrate along fractures and rise through the ground over considerable distances to form a halo in the air above, while Rn is also transported in ground waters. Nd-Sr isotope constraints on the age and origin of unconfomlity-type uranium deposits in the Alligator Rivers Uranium Field, Northern Territory, Australia.

However, not all of Dickson et al. Analyses of some representative Koongarra uraninites. Movements of uranium and daughter isotopes in the Koongarra uranium deposit. Apatite in Igneous Systems by Philip M. Lead isotope studies at Jabiluka.

Multiple isoclinal recumbent folding accompanied metamorphism. Silicification has also occurred in fault planes and within the Kombolgie Formation sandstone beneath the mineralisation, particularly adjacent to the reverse fault. Further assessment of stable lead isotope measurements for uranium exploration, Pine Creek Geosyncline, Northern Territory, Australia. Even the article we are directing you to could, in principle, st helens dating sites change without notice on sites we do not control.

It is hardly surprising, therefore, anonymous speed dating that the soils overlying the ore zones and the immediate areas of host rocks carry anomalous U concentrations compared to background levels. Council suggested that they join forces. Association of this outer halo alteration with the mineralisation is demonstrated by the apparent symmetrical distribution of this alteration about the orebody. Analyses of alteration sequences of uraninites to uranyl silicates at Koongarra.

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An approach to the mathematical modelling of the uranium series redistribution within ore bodies. Radon survey at the Koongarra uranium deposit, Northern Territory. Of the various radiometric methods, uranium-thorium- lead U-Th-Pb was the first used and it is still widely employed today, particularly when zircons are present in the rocks to be dated. In other words, the quantities of Pb could not simply be accounted for by radioactive decay of U, officer implying open system behaviour.

This of course assumes that the Pb in the galenas was also derived predominantly from U decay. Koongarra uranium deposits. The isotope geology of lead. Because of these geological constraints, Page et al.

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