Garnet U-Pb and O isotopic determinations reveal a shear-zone induced hydrothermal system
Portsmouth Research Portal. Bird M. Thirlwall Professor Rob Strachan C. Caledonian orogenesis in Scotland is currently interpreted in terms of a Mid-Ordovician arc—continent collision Grampian event followed by the Silurian collision of Laurentia with Baltica Scandian event. Lu—Hf and Sm—Nd garnet ages of c. Lu—Hf and Sm—Nd ages of c. The existing two-stage Grampian—Scandian model for Caledonian orogenesis in northern Scotland is thus an oversimplification, and the new ages imply a more complex structural evolution. The restriction of the Late Ordovician and Silurian events to the Northern Highland terrane reinforces the suggestion that it was far removed from the Grampian terrane until juxtaposition following major end-Caledonian Devonian sinistral displacement along the Great Glen Fault.
The Lu–Hf dating of garnets and the ages of the Alpine high-pressure metamorphism
The Lu-Hf isotope system, with applications to geo- and cosmochemistry, was first investigated in the early s Patchett b ; Patchett and Tatsumoto a, b , c , following the successful implementation of the Rb-Sr and Sm-Nd isotope systems several years earlier. There are some obvious similarities between the Lu-Hf and Sm-Nd isotope systems and, as a result, they have long been used in concert in a wide range of studies e.
In these two systems all elements are lithophile and refractory with high condensation temperatures. Because of these characteristics it has long been assumed that their abundances in the Earth can be approximated by chondritic meteorites see discussion below. In addition, all elements in these systems behave incompatibly during melting and are concentrated in the melt over the residual solid.
Toggle navigation. Have you forgotten your login? Journal articles. Caroline Lotout 1 AuthorId : Author. Robert Anczkiewicz 3 AuthorId : Author. Jean van den Driessche 2 AuthorId : Author. Hide details. Abstract : Linking mineral growth and time is required to unravel the evolution of metamorphic rocks. However, dating early metamorphic stages is a challenge, due to subsequent retrograde overprinting.
In the retrogressed sample, most of the zircon grains are characterized by negative Eu anomalies and HREE enrichment, and yield an Ordovician U-Pb date of
Subduction zones are places on the Earth where dense ocean crust descends or subducts beneath more buoyant continental or oceanic crust. Active subduction zones are responsible for most of Earth’s large earthquakes and explosive volcanic eruptions. Ancient subduction zones now exposed at the Earth’s surface provide important information on the processes, both physical and chemical, occurring within active subduction zones.
Lu–Hf garnet dating has the potential to yield information about the timing of the prograde evolution of subducting rocks under increasing.
Toggle navigation ScienceBase-Catalog. Your browser does not have support for cookies enabled. Some features of this application will not work. Wintzer, N. Ages are determined with lower-intercept isochron plots from multiple garnet and whole rock fractions, and garnet model age plots show distribution of garnet fractions with excluded points grayed out.
Elemental concentrations of Lu and Hf, isotopic ratios, and epsilon Hf initial and today values are also included for each sample in table form. Samples are from 2 miles north-northwest of the abandoned townsite of Stibnite, Idaho. Click on title to download individual files attached to this item. Lu-Hf Garnet Geochronology Metadata. These data provide age of metamorphism Ore is hosted in metasedimentary rock packages many of which are cut by dikes, so these ages provide part of the early geologic history leading up to ore deposition.
Lu-Hf Dating: The Lu-Hf Isotope System
Continue to access RSC content when you are not at your institution. Follow our step-by-step guide. Bast uni-muenster. When such samples are spiked, correcting for the isobaric interference of Lu on Hf is not always possible if the separation of Lu and Hf is insufficient.
Recently developed Lu-Hf dating methods allow chronology of these garnet separates with high precision (
I primarily use and develop geochemical and isotopic techniques to determine age of rocks and their origin. One of my main research fields is evolution of continental collision zones such as the Himalaya or the Carpathians. Geochronology is of my particular interest, especially means of linking isotopic ages with specific geologic events. Recently I focus on application of isotopes to environmental and archaeological problems. Isotopic systematics and trace element partitioning under extreme conditions.
Migration of mammals in Ice Age Reconstruction of migration paths of mammals during ice age by studying Sr isotopic signature and trace element record in teeth of mammoths and other animals. Publications Soldner, J. Lokas, E. Revised Middle-Upper Jurassic strontium isotope stratigraphy. Mukhopadhyay, D. Chakraborty, S. Anczkiewicz, R. Skrzypek, E.
Dating a single garnet crystal with very high Sm/Nd ratios (Campo basement unit, Eastern Alps)
Gonzaga, M. Menzies, M. Thirlwall, D. Jacob, A.
The Lu–Hf dating of garnets and the ages of the. Alpine high-pressure metamorphism. Nature , – Eskola, P. (). The mineral facies of rocks.
Anczkiewicz, R. Lu-Hf geochronology and trace element distribution in garnet: Implications for uplift and exhumation of ultra-high pressure granulites in the Sudetes, SW Poland. Lithos , 95 pp. The surrounding rocks were metamorphosed at the same time as indicated by The second metamorphic episode, which affected most of the lower crust in the Orlica-Snieznik Massif OSM occurred at ca. Trace element distribution in garnets from the layered granulites showed significant differences in distribution of medium and HREE in garnets from mafic and felsic protoliths over the course of the metamorphic evolution.
This had strong impact on the isotopic dating results and led to “decoupling” of the Sm-Nd and Lu-Hf clocks, which recorded timing of the two different metamorphic episodes separated by as much as 40 Ma. Moreover, the preservation of the HREE growth zonation profile in garnets from the felsic granulites whose minimum metamorphic temperature was established at degrees C implies that the Lu-Hf system under relatively dry conditions does not undergo significant diffusional re-equilibration even at such extreme temperatures and therefore it sill provides the age of prograde garnet growth.
Under hydrous conditions, at least some resetting will take place, as documented by the partially relaxed HREE zonation profile in the amphibolitised mafic granulite, which yielded a 10 Ma younger age. The HREE distribution study appeared to be a particularly valuable and essential tool, which allowed us to distinguish garnet growth from post-growth complexities and hence, provide improved age interpretation.
Medium REE, on the other hand, did not show any obvious correlation with the isotopic signature of garnet. Two distinct metamorphic episodes recorded in the Stary Gieraltow region show that buoyancy-driven uplift of UHP rocks can be arrested at the base of a continental crust if not supported by any additional force.
Garnet Lu-Hf Ages and Isotope Data for the Stibnite, Idaho Area
Lu-Hf and Sm-Nd garnet geochronology : chronometric closure and implications for dating petrological processes. N2 – To investigate the systematics of the Lu—Hf and Sm—Nd garnet chronometers, we performed REE and isotope analyses on garnet crystals of different size 0. The Lu—Hf dates are similar among grains having radii larger than 1.
One garnet pyroxenite lies significantly below the mantle Hf–Nd isotope array In this study, we have analysed the Lu–Hf and Re–Os isotopic compositions of a Dating mantle differentiation: a comparison of the Lu–Hf, Re–Os and Sm–Nd.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Duchecircne and J. Blichert-Toft and B. Luais and P. Lardeaux and F. Duchecircne , J.
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Lutetium—hafnium dating is a geochronological dating method utilizing the radioactive decay system of lutetium — to hafnium — The trace concentration of the Lu and Hf in earth materials posed some technological difficulties in using Lu—Hf dating extensively in the s. Lutetium is a rare-earth element , with one naturally-occurring stable isotope Lu and one naturally-occurring radioactive isotope Lu.
An age equation is set up for every radiometric dating technique to describe the mathematical relationship of the number of parent and daughter nuclide.
Lu–Hf and Sm–Nd dating of metamorphic garnet: evidence for multiple accretion events during the Caledonian orogeny in Scotland. Research output.