We implement several procedures that help combat these analytical issues. Pb and U. To decrease molecular interferences at Pb peaks and increase the signal:noise ratio, we also use the energy filter to only accept high-energy ions into the collector. Because common lead and the amount of molecular interferences vary by sample, energy filtering is not always used.
Both apatite and rutile date profiles were calculated using experimentally determined Pb diffusion parameters. (Cherniak, ; Cherniak et al.
Passarelli; Miguel A. Basei; Oswaldo Siga Jr. Sproesser; Vasco A. It provides reliable and accurate results in age determination of superposed events. However, the open-system behavior such as Pb-loss, the inheritance problem and metamictization processes allow and impel us to a much richer understanding of the power and limitations of U-Pb geochronology and thermochronology. Since , the Interdepartmental Laboratory of Isotopic Geology focus the study of the Earth’s geologic processes, dealing with themes such as plate tectonics, plutonism, volcanism, sedimentary rocks, tectono-thermal evolution, and more recently environmental studies.
CPGeo gathers modern laboratories installed inan area of m 2 and is equipped with seven mass spectrometers for radiogenic and stable isotope analysis. The method is considered one of the most precise among the isotopic techniques available for U-Th-Pb geochronology of accessory minerals, because it is relative insensitive to chemical yields or mass spectrometric sensitivity Parrish and Noble , and is therefore largely used by the scientific community.
According to Kosler and Sylvester the in situ U-Pb geochronology was introduced ca. TIMS analyses, comparatively to SIMS analyses, have the advantage of producing high-precision U-Pb data, being specifically important when dating superposed events or even a single crystal, in order to define crystallization ages.
U-Pb LA-ICPMS dating using accessory mineral standards with variable common Pb
Chemical analyses show that rutile included in other minerals Rt inc commonly show higher SiO 2 and FeO contents and lower Nb 2 O 3 and ZrO 2 contents if compared with rutile in the matrix of the garnet-rich layer Rt mat. Cr 2 O 3 concentrations are quite similar in both types of rutile. Rt mat commonly shows a greater variability in minor elements, especially Nb 2 O 3 0. Few compilations of geochemical and geochronological data on rutile in Variscan metabasites can be found in literature, thus these data represent a new insight on a mineral phase the significance and scientific interest of which are rising in the last years.
Future studies on the origin and ages of emplacement and metamorphism either prograde or retrograde of this kind of rock, widespread in the Variscan chain, will benefit from these data as a term of comparison. Part of these data mainly Rt inc belongs to the supplementary material of .
Allanite U-Pb ages together with the petrographic support can provide the time of the peak metamorphism (Kim et al. ). Rutile is the most common TiO2.
Abstract In situ laser ablation ICP-MS U—Pb dating of metamorphic rutile from granulite facies metapelitic rocks of the Archaean Pikwitonei granulite domain Manitoba, Canada provides constraints on Pb diffusion and characterizes the closure behavior of rutile. Age profiles indicate that volume diffusion of Pb occurs in rutile implying that the ages represent cooling ages. To investigate the closure behavior of Pb in rutile closure temperature profiles T c x were constructed based on different models combined with experimentally-determined diffusion parameters.
The classical T c x model of Dodson ; Mat. Forum 7, — indicates a rapid decrease of T c in the rims of grains, providing unrealistic estimates for the cooling rate when combined with U—Pb ages. A new T c x model was constructed based on the analyzed age profiles that are described by an error function. This model shows a more steady decrease in T c throughout the grain from ca.
The new model provides a better description of the relation between age and T c for the analyzed grains. However, both T c x models demonstrate that even in small grains the variations of T c can be significant making it impossible to derive one representative T c for Pb in rutile. The error function-based T c x model allows the determination of cooling rates, which show a decrease over time from ca. This consistency supports the validity of our model and indicates that cooling rates can be estimated from single grains by LA-ICP-MS U—Pb dating of rutile providing constraints on the cooling history of a metamorphic terrane.
In situ laser ablation ICP-MS U-Pb dating of metamorphic rutile from granulite facies metapelitic rocks of the Archaean Pikwitonei granulite domain Manitoba, Canada provides constraints on Pb diffusion and characterizes the closure behavior of rutile. To investigate the closure behavior of Pb in rutile closure temperature profiles Tc x were constructed based on different models combined with experimentally-determined diffusion parameters.
Rutile U-Pb Geochronology
Rutile is a common accessory mineral that occurs in a wide spectrum of metamorphic rocks, such as in blueschists, eclogites, and granulites and as one of the most stable detrital heavy minerals in sedimentary rocks. The advent of rutile trace element thermometry has generated increased interest in a better understanding of rutile formation. Rutile thermometry of the same detrital grains indicates former granulite-facies conditions. The methods outlined in this paper should find wide application in studies that require age information of single spots, e.
Rutile is a common accessory mineral that is found in a wide range of rock types on Earth and beyond e. On Earth, all major rock types exhibit rutile-bearing samples.
The power of in situ U/Pb rutile dating is illus- Communicated by J. Hoefs. trated by comparing ages of detrital rutile and zircon from a recent sediment from the.
Box , Beijing , P. E-mail: xieliewen mail. The advantages include high spatial resolution, high sample throughput, good precision and accuracy, and limited sample preparation. For the application of these techniques in U—Th—Pb geochronology, the main challenges involve ion counter drift, matrix differences between reference materials and samples, laser-induced downhole elemental fractionation and common lead corrections. We review recent efforts to improve spatial resolution, calibrate ion counter drift, and correct for common lead contamination, elemental fractionation and matrix mismatching.
Multi-collectors simultaneously measure all isotopic signals over flat-topped peaks so that 1 the detection efficiency is significantly improved and relatively high spatial resolution is obtained, 4,5 and 2 the effects of spectral skew and flicker noise from the plasma source or ablated particles are removed or significantly reduced, resulting in improved counting statistics and lower internal and external uncertainties in isotopic ratios.
In situ U-Pb rutile dating by LA-ICP-MS
Storey, Martin Smith , T. N2 – In situ U—Pb dating of a variety of mineral phases is an important goal in petrology. This study reports data chiefly from titanite, but also from rutile and apatite, obtained using the laser ablation LA -ICP-MS methodology on polished thick sections in order to retain as much petrologic information as possible, and allowing trace element analyses from adjacent areas to the U—Pb analyses. The samples analysed come from Svecofennian intermediate to acid volcanic rocks of the Porphyry Group within the major iron ore province of Norrbotten, northern Sweden, where titanite is a common phase associated with the mineralisation.
A new protocol for in situ Hf isotope analysis of rutile is presented, and rutiles with ≥ 40 ppm Hf. A new rutile standard for in situ U-Pb dating.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Schmitt and T. Schmitt , T. Zack Published Geology Chemical Geology. View via Publisher. Save to Library. Create Alert. Launch Research Feed.
Time resolved rutile U/Pb data derived from LA-ICPMS – a case study from the North Pamir
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Zircon is the most commonly used mineral in U-Pb dating but monazite, apatite, xenotime, titanite, rutile, baddeleyite, perovskite and allanite are also used and.
Help Contact us. Bracciali, Laura. Geosciences , 9 The significant and continuous improvement of instrumentation and approaches has opened new fields of applications by extending the range of minerals that can be dated by this method. Following the development and distribution to the community of good quality reference materials in the last decade, rutile U-Pb thermochronology with a precision only slightly worse than zircon has become a commonly used method to track cooling of deep-seated rocks.
Recrystallization and secondary growth during metamorphism and the presence of grain boundary fluids can also affect the U-Pb isotopic system in rutile. A growing body of research focusing on U-Pb dating of rutile by LA ICP-MS is greatly improving our understanding of the behavior of this mineral with regards to retention of radiogenic Pb. This is key to fully exploit its potential as a tracker of geological processes. The latest developments in this field are reviewed in this contribution.
The combined application of U-Pb zircon and rutile chronology in provenance studies, particularly when complemented by lower-T thermochronometry data, allows the isotopic characterization of the sources across a wide range of temperatures. The benefits of applying detrital zircon-rutile U-Pb chronology as a coupled provenance proxy are presented here, with a focus on the Eastern Himalayan-Indo-Burman region, where a growing number of successful studies employs such an approach to help constrain river drainage and basin evolution and to infer feedback relationships between erosion, tectonics and climate.
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Matrix‐matched reference materials are necessary for accurate microbeam U‐Pb dating and Hf isotopic determination. This study introduces.
This paper presents new data related to the emplacement ages of the Amakinskaya and Taezhnaya kimberlites of the Mirny field, Siberia, located in the southern part of the Yakutian diamondiferous province. This study analyzed rutile and titanite grains along with zircons for U-Pb isotope composition by laser ablation LA -inductively coupled plasma-mass spectrometry ICP-MS and evaluated the applicability of rutile and titanite for the dating of kimberlite emplacements.
Both minerals contain substantial admixtures of common Pb in their Pb isotope composition. Therefore, the Pb method was applied for common Pb correction during age calculation. All age estimates correspond to the main epoch of diamondiferous kimberlite activity in the Siberian platform and suggest the formation of the Mirny kimberlite field within a single event or two separate events occurring close together in time. Results obtained from this study indicate that rutile and titanite can be useful for the dating of kimberlite emplacements.
Agashev V. Pokhilenko V. Tolstov V.