John Wiley and Sons Inc. Dating of the northern Idaho batholith and the Bitterroot metamorphic core complex: magmatism preceding and contemporaneous with extension. Relationships between luhf partial garnet, plutonism, orogeny, garnet exhumation: Idaho—Bitterroot Batholith. Exhumation and with of Eocene metamorphic luhf complexes along garnet Lewis and Clark strike-slip system. Frost CD, Winston D. Nd isotope systematics of coarse- and fine-grained sediments: Examples dating the Middle Proterozoic Belt—Purcell Supergroup.
The Lu–Hf dating of garnets and the ages of the Alpine high-pressure metamorphism
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.
Lu–Hf garnet dating has the potential to yield information about the timing of the prograde evolution of subducting rocks under increasing.
Providing customized analytical solutions at the highest standards of quality assurance and quality control. Samples for U-Pb dating are processed using a Rhino jaw crusher, a Bico disk grinder equipped with ceramic grinding plates, and a Wilfley wet shaker table equipped with a machined Plexiglass top, followed by conventional heavy liquid and magnetic separation using a Frantz magnetic separator.
Four binocular microscope workstations are available for sample picking. The external morphology of mineral grains for analysis can be documented by SEM, and internal structure can be examined in polished grain mounts by cathodoluminescence imaging. TIMS U-Pb geochronology is widely recognized as one of the most robust and precise dating techniques. We have dated rocks from Pliocene to Archean in age, for clients from universities, government and industry.
U and Pb are loaded together on an outgassed zone-refined Re filament, and run separately in peak-hopping mode. Data reduction is done with U-Pbr, an Excel-based routine based on the error estimate algorithms published by Schmitz and Shoene Zircons are routinely analyzed from igneous rocks as well as detrital zircon or stream sediment samples.
Both U-Pb data for geochronology and up to 30 user-selected trace elements, including rare earth elements, are acquired from a single laser shot. Data are reduced using Iolite software Patton et al. Richard Friedman.
Kimberlites from Southern Africa, along with their low-Cr megacrysts, have unusual Hf—Nd isotopic characteristics. Group I kimberlites have Hf values varying from —1. Low-Cr megacryst suites from individual Group I kimberlites have compositions that overlap those of their host kimberlites.
I use high resolution Lu-Hf and Sm-Nd garnet geochronology as well as in situ LA ICPMS U-Pb zircon dating to estimate rates of geological processes. Recently I.
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. A similar record of Mid- and Late Ordovician metamorphic events within the Laurentian-derived Uppermost Allochthons of Norway has been attributed to episodic accretion significantly prior to Silurian continent—continent collision and closure of the Iapetus Ocean.
Garnet Lu-Hf Ages and Isotope Data for the Stibnite, Idaho Area
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.
Determining the timing and rates of past events in these ancient subduction zones, however, has proven extremely difficult. This proposed research will develop a new technique to determine ages on lawsonite, an important mineral that forms during metamorphism associated with subduction zones. Dating lawsonite, therefore, provides geologists the ability to determine the timing and rates of ancient subduction processes.
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. In contrast, Sm—Nd dates are equal to or younger than the — Ma age of peak metamorphism. Instead, the isotope dates are interpreted to reflect partial loss of radiogenic Hf and Nd, and are used to constrain the systematics of the garnet chronometers at high temperature.
The data constrain the grain sizes and thermal histories for which garnet dates can be validly linked to prograde or peak P—T conditions. In addition, garnet dates can now be used to place quantitative constraints on initial cooling from high- and ultrahigh temperature—a temperature segment that is inaccessible to other thermochronometers.
Gonzaga, M. Menzies, M. Thirlwall, D. Jacob, A. Cratonic eclogites and garnet pyroxenites from the Kaapvaal craton have heterogeneous Hf—Nd—Sr— O isotope ratios that define a positive Hf—Nd isotope array and a negative Nd—Sr isotope array. Isotopic variability encompasses depleted mid-ocean ridge basalt and ocean-island basalt to enriched mantle compositions Group I and II kimberlites and overlaps with that of the Kaapvaal craton garnet peridotite xenoliths.
Lu–Hf geochronology and trace element distribution in garnet: implications for uplift Improving precision of Sm-Nd garnet dating by H2SO4 leaching: a simple.
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.
Garnet U-Pb and O isotopic determinations reveal a shear-zone induced hydrothermal system
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.
Lutetium–hafnium dating is a geochronological dating method utilizing the radioactive decay system of lutetium– to hafnium– With a commonly accepted half-life of billion years, the long-living Lu–Hf decay pair survives through.
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Dating a single garnet crystal with very high Sm/Nd ratios (Campo basement unit, Eastern Alps)
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.
Although coupled Sm-Nd and Lu-Hf garnet geochronology is not as prevalent as instances where only one system has been applied to dating.
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. Metamorphism local to the mining area was synchronous with development of the Salmon River Suture Zone to 90 Ma; Getty and others, ; McKay and others, ; Wilford, , which is approximately 50 miles to the west of Stibnite, Idaho.
References Cited: Getty, S. Cordillera: Contributions to Mineralogy and Petrology, v.
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A suite of pyroxenites from the Beni Bousera peridotite massif, northern Morocco, have been analysed for Re—Os and Lu—Hf isotopic compositions. In general, the Nd—Hf isotope compositions of the pyroxenites lie close to the mantle array. As with the Sm—Nd and Rb—Sr systems, parent—daughter and isotopic ratios for the Lu—Hf system have been recently decoupled by a partial melting event associated with transfer of the massif from mantle to crust.
The near-solidus extraction of a siliceous melt from the pyroxenites is also a possible explanation for the orthopyroxene-rich margins to numerous pyroxenite layers, via reaction with peridotite. Pyroxenite Os isotope compositions are much more radiogenic than their host peridotites. In contrast to cratonic eclogites, most pyroxenites analysed here and those reported in the literature lie close to the mantle Nd—Hf isotope array.
Selected samples have ~mm‐sized garnet grains that have been sampled with a micro‐drill and analysed for dating. The Lu–Hf dates of bulk.
The absolute crystallization ages of minerals from hydrothermal fluids measured in situ can unravel the timing of key events leading to the formation of, for instance, ore deposits and hydrothermally derived geological terrains. This skarn age instead correlates with the occurrence of strike-slip and thrust faulting in the region. The low oxygen isotopic composition indicates the role of meteoric water in the garnet formation.
Meteoric water in this hydrothermal system would leach cations from the meta-volcano-sedimentary rocks necessary for mineralization. Silica-rich hydrothermal fluid reacts with calcic-rich materials in the meta-volcano-sedimentary rocks, depositing the garnet and magnetite. Our work suggests that the shear zone is rich in ores, rendering this deposit for NW China a prospective source for future mineral resource exploration. Garnet is an abundant mineral phase found in a range geological settings, from skarn-type ore deposits, granite, and low- and high-grade metamorphic rocks, to the upper mantle.
It is a widely used proxy in geothermobarometry 1 , 2. The stability and generally porphyroblastic nature of garnet makes it an ideal mineral for tracking the evolution of crystallization by measuring the elemental and isotopic compositions of different crystallization zones in garnet 3. On the other hand, heavy rare-earth elements are compatible in garnet, which can provide absolute age constraints using, for instance, the Lu-Hf and Sm-Nd isotopic systems 4 , 5.
More recently, with the advancement of the spatial and temporal resolution of laser ablation inductively coupled plasma mass spectrometry LA-ICP-MS , in-situ analyses of U-Pb isotopes on magmatic-hydrothermal garnet have successfully determined concordia ages that are identical to magmatic zircon U-Pb ages 6 — 9.