Ion microprobe in-situ dating of U-Pb minerals zircon, monazite, titanite, rutile, baddelejite with a composite internal structure. Dating of minerals or mineral zones formed at different stages during the evolution of a rock unit in order to define detailed P-T-time paths and thus determine rates of geological processes e. Combining different isotopic schemes in order to unravel complex geological evolutions. Cathodoluminescence and back scattered electron imaging as well as element mapping of datable minerals in order to understand diffusion profiles and mobility of isotopes and trace elements. Relating specific zoning patterns to crystallisation processes. The composition of datable minerals such as zircon, monazite and titanite in different geological environments as indicator of coexisting paragenesis to relate age and metamorphism. Modelling the distribution of trace elements between major and accessory phases. Trace element partitioning between garnet and zircon as a tool to detect equilibrium crystallisation. The effect of melt and fluids on the trace element composition of datable minerals. Main interests in the stability of U-bearing minerals over a wide range of P-T-fluid conditions.
Irka Hajdas, Susan Ivy-Ochs 9: Geochemical dataset of the Rhone River delta Lake Geneva sediments — disentangling human impacts from climate change 9: Holocene seismic activity of the Yavansu fault, western Turkey 9: Landscape evolution of the northern Alpine Foreland: Holocene treeline changes in the Canadian Cordillera are controlled by climate and local topography Historical evolution of human land-use in the catchment of Lake Murten
In-situ U-Th-Pb dating of In this study we apply LA-ICP-MS U-Th-Pb dating of monazite, xenotime, zircon, garnet, and staurolite to samples from the Straits Schist, SW Connecticut, a Silurian-Devonian sediment that experienced amphibolite facies metamorphism.
Volume 69 , September , Pages Review Pegmatites and aplites: Their genetic and applied ore geology Author links open overlay panel Harald G. Dill Show more https: Pegmatites are treated in this study together with aplitic rocks, which are compositionally similar to pegmatites but strikingly different from them by their fine-grained texture. Rocks of the granitic suite take an intermediate position between the two and, locally, they are transitional into both end-member types, emphasized in the denomination by supplements such as aplite granite or pegmatitic granite.
A similar scenario can be reported for syenitic and, less frequently, for granodioritic through dioritic rocks which are found to be associated in time and space with pegmatites and aplites. Pegmatites sensu stricto are found as immigrations into environments different from their birthplace where they were trapped in structures providing the accommodation space necessary for their emplacement and sealed off by impervious roof rocks. In principle, granites and pegmatites are two sides of the same coin, both are undergoing mobilization and migration; the granite mirrors diffusion and dissemination, the pegmatite reflects trapping and concentration.
Fractionation and separation can be recognized in the petroleum as well as in the pegmatite—granite systems. While the mineralogy of pegmatites has been intensively studied and also backed by experimental work, the economic or ore geology of these felsic rocks has not been given adequate attention, particularly when it comes to the classification of the pegmatites. The second string to the bow is the wide range of industrial mineral deposits feldspar, feldspathoids, quartz, alumosilicates—corundum, garnet, mica, graphite, kaolin.
Be—Li—Nb pegmatite stock-like and a mineralogical qualifier e. The CMS classification scheme as it stands is purely descriptive and designed for genetic and applied economic geology. In terms of structural geology and geodynamics, pegmatitic deposits primarily occur in ensialic Variscan-type orogens calc-alkaline with a thickened crust and a preponderance of thrusting and nappe stacking.
Prof. Dr. Bernhard Schulz
For more information on current and featured projects, go to http: Around 35 people from various research institutions, service providers and the mining industry attended the workshop from across Australia. Dr Mark Aylmore, recently appointed to take on the role of Applied Mineralogist in the JdLC, chaired the workshop that included presentations from:
Geochronology: Ion microprobe in-situ dating of U-Pb minerals (zircon, monazite, titanite, rutile, baddelejite) with a composite internal of minerals or mineral zones formed at different stages during the evolution of a rock unit in order to define detailed P-T-time paths and thus determine rates of geological processes (e.g. exhumation, subduction, cooling, melt residence and.
Canadian Journal of Earth Sciences, , 51 6: Matrix grains in these rocks show complex internal textures consistent with extensive corrosion and overgrowths which are attributed to partial dissolution of earlier monazite in anatectic melt followed by new growth during melt crystallization or subsequent fluid infiltration. The new monazite data show the following: The wide age range of the main Grenvillian metamorphism suggests episodic growth of monazite over a wide time span, consistent with protracted residence of the host rocks under high-temperature conditions.
The clusters in the age distribution likely represent major episodes of melt crystallization in the respective rocks, following the granulite-facies metamorphism. In contrast, the growth of the late Grenvillian monazite at ca.
Timing of metasomatism using SHRIMP U-Pb dating and oxygen isotopes
Hydrothermal xenotime dates polymetallic mineralization at Abra to c. Abstract The Proterozoic Capricorn Orogen is a major tectonic zone that records the assembly and subsequent reworking of the West Australian Craton. Recent seismic transects across the orogen have identified major crustal structures, some of which are spatially associated with hydrothermal mineral deposits. The sedimentary-rock-hosted Abra deposit, which is the largest base-metal accumulation in the Capricorn Orogen, is localized within the crust-cutting Lyons River—Quartzite Well fault zone.
Robust radiometric dates for the timing of sediment deposition and hydrothermal mineralization are essential for understanding the geological history of this long-lived orogen and the processes that formed the ore deposits.
REDUCED VOLUME APPROACH FOR IN SITU U–PB DATING OF ACCESSORY MINERALS 5 ION 1 Dynodest 2 Dynodend FIG. Illustration depicts the ion optics of an ETP discrete-dynode electron multiplier showing the electron gain at each successive dynode.
This belt was assembled at approximately 1. The discovery of abundant monazite in regionally extensive, km thick quartzites found throughout the orogenic belt may provide important new constraints on its tectonic history. These quartzites define the present regional geometry of exposed Proterozoic rocks and are believed to strongly influence local structure. Preliminary results of in-situ microprobe dating of monazite from the Ortega Quartzite in the Tusas Mountains in northern New Mexico suggest an increasing influence of 1.
Monazite from the Jawbone Syncline within northernmost part of the range consistently yields ages of 1. These monazite grains are interpreted to be mostly detrital in origin, with REE and age zoning reflecting the history of the source terranes. Monazite from an anticline immediately to the south has 1. Monazite from the middle and southern Tusas Mountains is predominantly 1. This suggests that a previously documented gradient in deformation and metamorphism from north to south may reflect a multistage tectonic history for the range, with an increasingly intense overprint of 1.
Monazite has also been found in several Proterozoic quartzites in Colorado, allowing the possibility to compare and correlate deformation and metamorphism across the region.
Decay routes[ edit ] The above uranium to lead decay routes occur via a series of alpha and beta decays, in which U with daughter nuclides undergo total eight alpha and six beta decays whereas U with daughters only experience seven alpha and four beta decays. The term U—Pb dating normally implies the coupled use of both decay schemes in the ‘concordia diagram’ see below. However, use of a single decay scheme usually U to Pb leads to the U—Pb isochron dating method, analogous to the rubidium—strontium dating method.
Finally, ages can also be determined from the U—Pb system by analysis of Pb isotope ratios alone. This is termed the lead—lead dating method. Clair Cameron Patterson , an American geochemist who pioneered studies of uranium—lead radiometric dating methods, is famous for having used it to obtain one of the earliest estimates of the age of the Earth.
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Click on the GSA logo to return to the main site. Special Paper , , p. Geodetic constraints on contemporary deformation in the northern Walker Lane: Central Nevada seismic belt postseismic relaxation ; senior author: Postglacial after 20 ka dextral slip rate of the offshore Alpine fault, New Zealand; senior author: Abrupt transition from magma-starved to magma-rich rifting in the eastern Black Sea; senior author: Metamorphic rates in collisional orogeny from in situ allanite and monazite dating; senior author: Increased mid-twentieth century riverbank erosion rates related to the demise of mill dams, South River, Virginia; senior author: Surface cracks record long-term seismic segmentation of the Andean margin; senior author:
Canadian Journal of Earth Sciences
Amphibolite facies metamorphism of the adjacent Vijayan Complex VC to the east is less well constrained but apparently somewhat younger Holzl et al. Additionally, the timing and nature of juxtaposition via thrusting of the HC above the VC is uncertain. The contact between the HC and VC, characterized by strong deformation, exotic tectonic slivers, migmatites, local serpentinite bodies, magnetite deposits, and gold mineralization is a major suture separating the Paleoproterozoic HC from the Grenville-age VC.
ion microprobe dating of monazite inclusions in garnets allows direct assessment of the timing of amphibolite-grade metamorphism and synchronous left-lateral shearing. Results.
Chris Marone Previous Speakers EarthScope speakers are selected based on their outstanding research accomplishments involving EarthScope as well as their abilities to engage a variety of audiences. Each speaker presents science-based lectures on their own EarthScope-related project, and their talks include an introduction highlighting broader EarthScope objectives and accomplishments.
Her research focuses on using GPS and imaging geodesy to examine tectonic phenomena including long-term plate motions, the distribution of relative motion within plate boundary zones, earthquakes, and transient tectonic deformation as well as non-tectonic signals such as glacial isostatic adjustment and glacier dynamics.
Julie is PI of an ongoing EarthScope project using GPS to look at fault locking and possible transient tectonic signals along the eastern edge of the Alaska subduction zone. Continuously operating GPS sites, such as those in the Earthscope Plate Boundary Observatory PBO , have allowed us to reduce measurement uncertainty and capture transient events such as slow slip episodes, postseismic motion, and seasonal variations, providing a more complete image of the deformation field. The deformation field here is complex, with contributions from long-term tectonic motion, earthquakes, postseismic deformation, slow slip episodes, seasonal snow loading, and the adjustment of the Earth to current and past ice loss.
Markley, a Steven R. Dunn, a Michael J. Jercinovic, b William H. Peck, c Michael L. Copyright remains with the author s or their institution s.
In situ geochronology on zoned monazite and zircon indicate growth by dissolution–precipitation in both phases at ~– Ma. Trace element geochemistry of rim domains in these phases are best explained by dissolution–reprecipitation in equilibrium with Na-rich fluid.
Advanced Search Abstract Paulsens is a mesothermal orogenic gold deposit located in the Wyloo Inlier on the southern margin of the Pilbara craton of Western Australia. Monazite and xenotime in the veins and from hydrothermally altered country rocks yield three distinct U-Pb dates of ca. Regional-scale hydrothermal events at ca. The in situ secondary ion mass spectrometry dating of monazite and xenotime employed here will lead to better targeting of orogenic gold deposits in the northern Capricorn Orogen, and these techniques can be utilized for orogenic gold exploration worldwide.
Introduction Exploration targeting of gold deposits can be significantly improved by understanding metallogenic events in both space and time Hronsky et al. By knowing the ages of hydrothermal mineralization, host rocks, and regional tectonothermal events, the search space can be minimized, and the financial risk to explorers greatly reduced Rasmussen et al.
Radioactive decay[ edit ] Example of a radioactive decay chain from lead Pb to lead Pb. The final decay product, lead Pb , is stable and can no longer undergo spontaneous radioactive decay. All ordinary matter is made up of combinations of chemical elements , each with its own atomic number , indicating the number of protons in the atomic nucleus.
Additionally, elements may exist in different isotopes , with each isotope of an element differing in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide. Some nuclides are inherently unstable.
Dating of apatite and monazite inclusions within apatite provides evidence for at least one younger metasomatic event at ~ Ga, and possibly multiple superimposed metasomatic events between and Ga. Lead isotop analyses of pyrite show extremely radiogenic Pb/ Pb ratios up to ~80 unsupported by in situ U decay. This excess.
Walther Kinetics of quartz dissolution at low temperature Chemical Geology, Vol. Brewster On circular polarization, as exhibited in the optical structure of amethyst, with remarks on the distribution of the colouring matter in that mineral Transactions of the Royal Society of Edinburgh, Vol. Wooster Growth and properties of large crystals of synthetic quartz Mineralogical Magazine, Vol. Thomas Response of synthetic quartz to X-ray irradiation Nature, Vol. Buerger The significance of “block structure” in crystals American Mineralogist, Vol.
Buerger The genesis of twin crystals American Mineralogist, Vol. Walker The Scientific Monthly, Vol.