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. Already have an account?
In situ U–Pb rutile dating by LA-ICP-MS: 208Pb correction and prospects for geological applications
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.
resolution U-Pb dating represented by chemical abrasion – isotope dilution – thermal laser ablation – inductively coupled plasma mass spectrometry (LA-ICP-MS). mount, following imaging and possibly in-situ chemical or isotopic analysis. (e.g., zircon, baddeleyite, or rutile), with the possible exception of high-U zircon.
Lead exists as radiogenic Pb, Pb and Pb and non-radiogenic Pb isotopes, the latter also referred to as common Pb. This is a special isotopic system because it involves three distinct decay systems, where MATERIAL and Th isotopes decay to stable Pb isotopes Faure and Mensing Q is the energy liberated in the disintegration process and is originated by the difference of mass between the parent nucleus and the highlight products.
The radiometric ages can be mathematically expressed by negative exponential equations: By analogy, U and Pb are obtained. When compared to upb methods,the U-Pb geochronologic system is the only one able to offer two radiometric chronometers for a pair of elements of a single material. If an analytical laicpms does not plot on the Concordia Curve, the ages are no more concordant. Then the results yielded by each chronometer are different, thus characterizing a discordance.
In situ U-Pb rutile dating by LA-ICP-MS
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.
According to Kosler and Sylvester () the in situ U-Pb geochronology was introduced There will be situations for which SIMS or LA-ICP-MS is more appropriate or Experimental studies have indicated that Tc for Pb diffusion in rutile is.
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Find more information on the Altmetric Attention Score and how the score is calculated. The U—Pb geochronologic analysis of accessory minerals has played an important role in Earth and solar system science in constraining the ages of a wide variety of rocks and minerals. Currently, the significant matrix effects observed between different accessory minerals and the lack of high-quality standards for many minerals of interest are the major limitations of its geochronological applications.
In this study, we investigated the effects of the addition of oxygen, nitrogen, and water vapor before and after the ablation cell on the accuracy of the U—Pb dating of different minerals e. We found that the addition of water vapor, unlike that of oxygen and nitrogen, before the ablation cell can significantly suppress the matrix effects on U—Pb dating. This can be attributed to the suppression of elemental fractionation in both the laser ablation and ICP ionization processes by the presence of water vapor.
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U-Pb LA-ICPMS dating using accessory mineral standards with variable common Pb
Apatite geochronology is a versatile method for providing medium temperature history constraints of magmatic and metamorphic rocks. Magmatic apatite often shows a sufficient spread in data to obtain a precise and accurate lower intercept age. If this is not the case, the initial Pb isotopic composition needs to be estimated to obtain accurate and precise age information from apatite.
Two approaches are common, one being the estimation of common Pb from a Pb evolution model and the other being the measurement of a coexisting mineral phase that tends to incorporate Pb but not U, e. The resulting age information is accurate and precise despite using plagioclase rather than K-feldspar, as is normally used, to define initial Pb isotope compositions.
ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has become more For in-situ radiometric U–Pb dating and the multi-element T.; Mertz-Kraus, R.; Saul, J.M. LA-ICP-MS U–Pb dating of rutile inclusions.
Analyses are performed on a routine basis for detrital zircon provenance analysis, formation ages of magmatic and metamorphic rocks, structural and tectonic framework studies and for ore formation investigations. Where core-rim or other significant growth domains is observed it is sometimes possible to obtain multiple ages representing events recorded in the core or rim of a single crystal. Dating of accessory minerals other than zircon is a powerful tool for understanding geological processes that may not be recorded in the zircons, e.
Thus, we offer U-Th-Pb dating analyses of the mineral phases:. Analyses are performed on request and can include one single phase dating or several multi-phase dating of the minerals listed above. Please consult the laboratory staff for further information. Concurrently obtaining an age as well and the trace elements content from the very same analysis location offers the opportunity to use these data for a more spatially exact geological interpretation of the mineral or rock.
Geochemical and geochronological dataset of rutile from a Variscan metabasite in Sardinia, Italy
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In situ U-Pb dating with laser ablation has recently become available to date periclase for Mg (TAP), wollastonite for Ca (PETH), and rutile for Ti (PETJ). LA-ICP-MS element mapping of garnet was performed at the Ore.
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. However, the data are a priori accurate as they are geologically reasonable. Apatite shows reverse discordance, which could be explained by a number of scenarios.
The titanite grains studied show complex internal structures. Rare earth element REE analysis by LA-ICP-MS demonstrates that the core and rim zones are distinct and supports a model for two-stage evolution in two out of three samples, with the rims in these samples being enriched in total REE, and particularly in LREE in one sample, and displaying a positive Y-anomaly in contrast to the cores.
In situ U—Pb analysis reveals that core zones from all samples retain distinct older ages of c. In both cases, the ages are consistent with previous age determinations from the Fe oxide—apatite deposits. A sample from Malmberget records a slightly different scenario, where U—Pb ages spread along concordia from c.
Application of Plasma Ionization Isotope Ratio Mass Spectrometry
Stockli, George L. Luvizotto, Matthias G. Barth, Elena Belousova , Melissa R. Wolfe, Richard W. 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.
The accurate and precise in situ analysis of Pb isotopes in feldspar in the ), consistent with constraints from rutile ages (Scoates and Wall ). Chew, D., Petrus, J., and Kamber, B. () U–Pb LA–ICPMS dating.
Metrics details. These sampled both oceanic brecciated material and a blackwall reaction zone in contact with a micaschist and serpentinized peridotite. Textural observations combined with new geochronological data indicate that rutile and titanite both grew below their closure temperatures during Alpine metamorphism. We present a technique to calculate the most precise and accurate ages possible using a two-dimensional U—Pb isochron on a Wetherill concordia.
Rutile from two samples gave a U—Pb isochron age of Titanite from three samples gave a U—Pb isochron age of This age is consistent with Rb—Sr isochron ages on mylonites along and in the footwall of the Lunghin—Mortirolo movement zone, a major boundary that separates ductile deformation in the footwall from mostly localized and brittle deformation in the hangingwall. Rubatto In the past decade, U—Pb geochronology of other accessory minerals has attracted increasing interest, with the growing recognition that in metamorphic contexts they may record a different part of the P—T evolution from zircon e.
Engi ; Kohn ; Zack and Kooijman