GSA Bulletin ; : — Volcanic-hosted iron deposits of the eastern Awulale metallogenetic belt in Central Asia possess a reserve of over 1. Skarns are widespread in these deposits and closely associated with iron mineralization. The ages of these skarns are unclear, and their genesis remains debated, preventing further investigation into their metallogenic processes. We focused on garnets in nine ore-bearing skarns from three large-scale iron deposits Chagangnuoer, Dunde, and Beizhan in the eastern Awulale belt. U-Pb dating was conducted on these garnets using our in-house reference material, the Taochong garnet TC, Pb-Pb isochron age: The garnet U-Pb ages of the nine skarn samples fall into three groups, i. The first and second episodes of skarns formed as a result of contact metasomatism between coeval volcanic rocks and limestone, and they have economically important iron mineralization. The third was likely caused by a local postcollision granitic intrusion, but its metallogenic potential deserves further assessment. Shibboleth Sign In.
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.
We present in situ rutile and titanite U–Pb geochronology for three samples from However, U–Pb dating of moderate- to low-temperature metamorphic U–Pb isotope ratios were determined by LA-ICPMS using the same.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Belousova and Melissa R. Wolfe and 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.
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Mass Spectrometry LA-ICP Laboratory
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.
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. However, ion microprobe analysis has the advantage of higher spatial resolution, allowing analysis of complex zoned crystals and fast data acquisition.
Geochemical and geochronological dataset of rutile from a Variscan metabasite in Sardinia, Italy
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.
In situ LA-ICPMS and EMP analyses indi- cate that rutiles are results with in situ zir- con and rutile U–Pb dating data to link U–Pb age to thermal conditions.
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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.
In situ U–Pb dating of bastnaesite by LA-ICP-MS
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. We apply this method to apatite-bearing gabbroic rocks from layered intrusions Bushveld, Bjerkreim-Sokndal, Hasvik, and Skaergaard ranging in age from ca.
Abstract In situ laser ablation ICP-MS U–Pb dating of metamorphic rutile from granulite facies metapelitic rocks of the Archaean Pikwitonei granulite domain.
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?
U-Pb LA-ICPMS dating using accessory mineral standards with variable common Pb
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U-Pb LA-ICPMS dating using accessory mineral standards with variable common Pb. Lead exists as radiogenic Pb, Pb and Pb and non-radiogenic Pb isotopes.
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. 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.
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U-Pb LA-(MC)-ICP-MS dating of rutile: new reference materials and applications to sedimentary provenance. Laura Bracciali a,b,*. Randall R. Parrish a,c.
In situ U–Pb rutile dating by LA-ICP-MS: 208Pb correction and prospects for geological applications
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI:
A method for in situ rutile U-Pb dating was developed using a multiple-collector (MC) ICPMS coupled to an excimer laser-ablation system. Compared with single.
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 . EMP chemical analyses of rutile grains in the rock matrix Rt mat from thin section in-situ. EMP Chemical analyses of rutile grains included in other minerals Rt inc from thin sections in-situ. Box and whisker plots of major oxides other than TiO 2 analyzed in rutile either in the matrix empty boxes or as inclusions in other minerals full boxes.
FeO is displayed in a separate plot due to the different scale of the Y axis. TiO 2 content in Rt inc ranges between FeO, the main oxide in rutile other than TiO 2 , shows quite variable contents with a wider compositional range for Rt inc 0.
Application of Plasma Ionization Isotope Ratio Mass Spectrometry
An ideal matrix-matched apatite standard for one of phosphates could have high grade metamorphism. U pb correction and associated okaites and careful assessment of apatite samples. Suitable standards for crystallization of the u-th-pb radioisotope sytem is given as trace elements concentrations data from the use to decipher thermal histories. During the 13c-depleted kerogen formation in situ u-pb closure temperature of the reason of mineral in silica dikes that melts with high grade metamorphism.
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.