This study presents apatite LA-ICP-MS U-Pb age and trace elements concentrations data from differ... more This study presents apatite LA-ICP-MS U-Pb age and trace elements concentrations data from different granite types from the Tatra Mountains, Poland. Apatite from monazite and xenotime-bearing High Tatra granite was dated at 339 ± 5 Ma. The apatite LREE patterns reflect two types of magmas that contributed to this layered magma series. Apatite from a hybrid allanite-bearing diorite from the Goryczkowa Unit was dated at 340 ± 4 Ma with apatite LREE depletion reflecting the role of allanite and titanite during apatite crystallization. Apatite crystals from a hybrid cumulative rock from the Western Tatra Mountains were dated at 344 ± 3 Ma. Apatite is one of the main REE carriers in this sample and exhibit flat REE patterns. Taking into account the relatively low closure temperature of the U-Pb system in apatite (350– 550°C), the c. 340 Ma apatite ages mark the end of high temperature tectonometamorphic activity in the Tatra Mountains.
The main products of volcanic activity in the teschenite-picrite association (TPA) are shallow, s... more The main products of volcanic activity in the teschenite-picrite association (TPA) are shallow, sub-volcanic intrusions, which predominate over extrusive volcanic rocks. They comprise a wide range of intrusive rocks which fall into two main groups: alkaline (teschenite, picrite, syenite, lamprophyre) and subalkaline (dolerite). Previous 40 Ar/ 39 Ar and 40 K/ 40 Ar dating of these rocks in the Polish Outer Western Carpathians, performed on kaersutite, sub-silicic dio-pside, phlogopite/biotite as well as on whole rock samples has yielded Early Cretaceous ages. Fluorapatite crystals were dated by the U-Pb LA-ICP-MS method to obtain the age of selected magmatic rocks (teschenite, lamprophyre) from the Cieszyn igneous province. Apatite-bearing samples from Boguszowice, Puńców and Lipowa yield U-Pb ages of 103± 20 Ma, 119.6 ± 3.2 Ma and 126.5 ± 8.8 Ma, respectively. The weighted average age for all three samples is 117.8 ± 7.3 Ma (MSWD =2.7). The considerably smaller dispersion in the apatite ages compared to the published amphibole and biotite ages is probably caused by the U-Pb system in apatite being less susceptible to the effects of hydrothermal alternation than the 40 Ar/ 39 Ar or 40 K/ 40 Ar system in amphibole and/or biotite. Available data suggest that volcanic activity in the Silesian Basin took place from 128 to 103 Ma with the the main magmatic phase constrained to 128—120 Ma.
Apatite is an important common U-and Th-bearing accessory mineral in igneous, metamorphic and cla... more Apatite is an important common U-and Th-bearing accessory mineral in igneous, metamorphic and clastic sed-imentary rocks. The advent of in situ U–Th–Pb apatite geochronology by the SIMS and LA-(MC)-ICP-MS methods has demonstrated the importance of having uniform and homogeneous reference materials. Recently, it has been shown that Sr and Nd isotopic data combined with U–Pb age and trace element concentration data can provide important constraints on apatite paragenesis because this phase usually exhibits high Sr and REE concentrations but has low Rb/Sr ratios which result in negligible corrections for the ingrowth of radiogenic Sr. However, as ap-atite can potentially have complex internal structures resulting from multiple thermal events, such as inherited cores and metamorphic overgrowths, requires that the Sr and Nd isotopic data should be measured with high spatial resolution. However isobaric interferences hamper the precise determination of Sr or Nd isotopic compositions in LA-MC-ICP-MS analysis. In this work we undertook in situ measurements of Sr and Nd isotopic compositions of eleven apatite reference materials (AP1, AP2, Durango, MAD, Otter Lake, NW-1, Slyudyanka, UWA-1, Mud Tank, McClure Mountain and SDG) commonly used in U–Th–Pb geochronology. Our obtained Sr and Sm– Nd isotopic compositions for these apatite samples are consistent with those values obtained by solution-based methods (isotope dilution and ion chromatography) using MC-ICP-MS or TIMS, which demonstrates the reliability and robustness of our analytical protocol.
We report experiments on optimisation of LA-ICP-MS mapping as a tool for visualising and quantify... more We report experiments on optimisation of LA-ICP-MS mapping as a tool for visualising and quantifying internal structure of trace element concentration in igneous minerals. The experimental design was refined with maps on clinopyroxene and amphibole macrocrysts (mainly antecrysts) from a porphyritic lamprophyre in NE Spain, as well as on a high precision metal wire grid. In terms of spatial resolution, we demonstrate with scanning electron microscope and white light interferometry that a full ablation removes between 0.4 and 0.7 μm of material, depending on ablation parameters. Maps were produced with square laser beam spots of 12 and 24 μm. It was found that complexities can be resolved in the sample even though they are smaller than the beam diameter (e.g., 7–10 μm discontinuities using 12 μm laser beam). Resolution in x and y was found to be identical, probably reflecting the fast washout of the two-volume ablation cell and the short total dwell time of the analyte menu selected. Due to the excellent stage reproducibility and the limited ablation depth, it is feasible to re-ablate the identical map area many times employing different instrument parameters or analyte menus. On the magmatic crystals, LA-ICP-MS maps define very sharp compositional zoning in trace elements, highlighting complex crystallisation histories where 'normal' magmatic fractionation is not the only process. Events of mafic recharge are easily recognised as zones enriched in compatible metals such as Cr, Ni or Sc. Further, trace element maps reveal complexities in mineral zoning previously undetectable with petrography or major element data. These include resorbed primitive cores and oscillatory zoning within apparently homogeneous mineral zones. Therefore, LA-ICP-MS mapping opens a new window of opportunity for analysis of magmatic histories. The wide combination of instrumental parameters, such as laser beam size, scan speed and repetition rate, make it possible to carry out experiments at different levels of detail. We recommend a two-step approach to mapping. The initial step involves rapid maps to gain an overview of potential complexities in the sample; this enhances representativeness of the analysed materials, as a large number of crystals and trace elements can be tested in little time. Subsequently, detailed maps can be carried out on areas of interest. An additional function-ality is to create 1D-profiles from 2D-maps. The potential of the technique to unveil compositional complexities efficiently and at greater detail than traditional microanalysis will help to improve our understanding of processes in the magmatic environment and beyond.
The Moatize-Minjova Basin is a Karoo-aged rift basin located in the Tete Province of central Moza... more The Moatize-Minjova Basin is a Karoo-aged rift basin located in the Tete Province of central Mozambique along the present-day Zambezi River valley. In this basin the Permian Moatize and Matinde formations consist of interbedded carbonaceous mudstones and sandstones with coal seams. The thermal history has been determined using rock samples from two coal exploration boreholes (ca. 500 m depth) to constrain the burial and exhumation history of the basin. Organic maturation levels were determined using vitrinite reflectance and spore fluorescence/colour. Ages and rates of tectonic uplift and denudation have been assessed by apatite fission track analysis. The thermal history was modelled by inverse modelling of the fission track and vitrinite reflectance data. The Moatize Formation attained a coal rank of bituminous coals with low to medium volatiles (1.3e1.7%Rr). Organic maturation levels increase in a linear fashion downhole in the two boreholes, indicating that burial was the main process controlling peak temperature maturation. Calculated palaeogeothermal gradients range from 59 C/km to 40 C/km. According to the models, peak burial temperatures were attained shortly (3e10 Ma) after deposition. Apatite fission track ages [146 to 84 Ma (Cretaceous)] are younger than the stratigraphic age. Thermal modelling indicates two episodes of cooling and exhumation: a first period of rapid cooling between 240 and 230 Ma (Middle e Upper Triassic boundary) implying 2500e3000 m of denudation; and a second period, also of rapid cooling, from 6 Ma (late Miocene) onwards implying 1000e1500 m of denudation. The first episode is related to the main compressional deformation event within the Cape Fold Belt in South Africa, which transferred stress northwards on pre-existing transtensional fault systems within the Karoo rift basins, causing tectonic inversion and uplift. During the Mesozoic and most of the Cenozoic the basin is characterized by very slow cooling. The second period of fast cooling and denudation during the Pliocene was likely related to the southward propagation of the East African Rift System into Mozambique.
Apatite incorporates variable and significant amounts of halogens (mainly F and Cl) in its crysta... more Apatite incorporates variable and significant amounts of halogens (mainly F and Cl) in its crystal structure, which can be used to determine the initial F and Cl concentrations of magmas. The amount of chlorine in the apatite lattice also exerts an important compositional control on the degree of fission-track annealing. Chlorine measurements in apatite have conventionally required electron probe microanalysis (EPMA). Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is increasingly used in apatite fission-track dating to determine U concentrations and also in simultaneous U-Pb dating and trace element measurements of apatite. Apatite Cl measurements by ICP-MS would remove the need for EPMA but the high (12.97 eV) first ionisation potential makes analysis challenging. Apatite Cl data were acquired using two analytical set-ups: a Resonetics M-50 193 nm ArF Excimer laser coupled to an Agilent 7700× quadrupole ICP-MS (using a 26 μm spot with an 8 Hz repetition rate) and a Photon Machines Analyte Excite 193 nm ArF Excimer laser coupled to a Thermo Scientific iCAP Qc (using a 30 μm spot with a 4 Hz repetition rate). Chlorine concentrations were determined by LA-ICP-MS (1140 analyses in total) for nineteen apatite occurrences, and there is a comprehensive EPMA Cl and F data set for 13 of the apatite samples. The apatite sample suite includes different compositions representative of the range likely to be encountered in natural apatites, along with extreme variants including two end-member chlorapatites. Between twenty-six and thirty-nine isotopes were determined in each apatite sample corresponding to a typical analytical protocol for integrated apatite fission track (U and Cl contents) and U-Pb dating, along with REE and trace element measurements. 35Cl backgrounds (present mainly in the argon gas) were ~ 45–65 kcps in the first set-up and ~ 4 kcps in the second set-up. 35Cl background-corrected signals ranged from ~ 0 cps in end-member fluorapatite to up to ~ 90 kcps in end-member chlorapatite. Use of a collision cell in both analytical set-ups decreased the low mass sensitivity by approximately an order of magnitude without improving the 35Cl signal-to-background ratio. A minor Ca isotope was used as the internal standard to correct for drift in instrument sensitivity and variations in ablation volume during sessions. The 35Cl/43Ca values for each apatite (10–20 analyses each) when plotted against the EPMA Cl concentrations yield excellently constrained calibration relationships, demonstrating the suitability of the analytical protocol and that routine apatite Cl measurements by ICP-MS are achievable.L'apatite contient des quantités variables et significatives d'halogènes (notamment F et Cl) dans sa structure cristalline qui peuvent être utilisées pour déterminer la concentration initiale en F et Cl des magmas. La quantité de chlore dans le réseau de l'apatite exerce également un contrôle compositionnel important sur le degré de recuit des traces de fission. Les mesures du chlore dans l'apatite ont conventionnellement nécessité la microanalyse par sonde électronique (EPMA). La spectrométrie de masse à source plasma couplée à l'ablation laser (LA-ICP-MS) est de plus en plus utilisé dans la datation sur traces de fission de l'apatite pour déterminer les concentrations en U et aussi pour la datation simultanées U-Pb et les mesures des éléments traces de l'apatite. Les mesures du Cl dans l'apatite par ICP-MS élimineraient la nécessité d'utiliser l'EPMA mais le fait que le premier potentiel d'ionisation (12.97 eV) soit haut rend l'analyse difficile. Les données du Cl dans l'apatite ont été acquises au moyen de deux systèmes analytiques: un laser ArF excimer 193 nm Resonetics M-50 couplé à un ICP-MS quadripôle Agilent 7700× (utilisant un spot de 26 µm avec un taux de répétition de 8 Hz) et un laser ArF excimer 193 nm Photon Machines Analyte Excite couplé à un Thermo Scientific iCAP Qc (en utilisant un spot 30 µm avec un taux de répétition de 4 Hz). Les concentrations en chlore ont été déterminées par LA-ICP-MS (1140 analyses au total) pour dix-neuf occurrences d'apatite, et il y a une complète base de données EPMA pour le Cl et le F pour treize des échantillons d'apatite. La suite comprend différents échantillons d'apatite représentant la gamme de compositions susceptible d'être rencontré dans les apatites naturelles, ainsi que des variantes extrêmes dont deux endmembers chlorapatites. Entre vingt-six et trente-neuf isotopes ont été déterminés dans chaque échantillon d'apatite ce qui correspond à un protocole classique d'analyse intégrée des traces de fission (teneurs en U et Cl) et datation U-Pb sur apatite, avec les mesures des REE et des éléments traces. Les bruits de fond du 35Cl (surtout présent dans le gaz argon) étaient d'environ 45–65 kcps pour le premier système d'analyse et d'environ 4 kcps pour le second système. Le signal corrigé du bruit de fond pour 35Cl varie de ~ 0 cps dans l'endmember fluorapatite jusqu'à environ 90 kcps pour l'endmember chlorapatite. L'utilisation d'une cellule de collision avec les deux types de systèmes d'analyse a diminué la sensibilité des faibles masses d'environ un ordre de grandeur sans pour autant améliorer le rapport signal-bruit de fond du 35Cl. Un isotope mineur du Ca a été utilisé comme étalon interne pour corriger la dérive de sensibilité de l'instrument et les variations du volume d'ablation au cours des séances d'analyse. Les valeurs 35Cl/43Ca pour chaque apatite (10–20 analyses chacune) lorsqu'elles sont reportées par rapport aux concentrations en Cl obtenu par EPMA produisent des relations d'étalonnage parfaitement contraintes, ce qui démontre la pertinence du protocole analytique et que les mesures de routine du Cl de l'apatite par ICP-MS sont réalisables.
This study presents apatite LA-ICP-MS U-Pb age and trace elements concentrations data from differ... more This study presents apatite LA-ICP-MS U-Pb age and trace elements concentrations data from different granite types from the Tatra Mountains, Poland. Apatite from monazite and xenotime-bearing High Tatra granite was dated at 339 ± 5 Ma. The apatite LREE patterns reflect two types of magmas that contributed to this layered magma series. Apatite from a hybrid allanite-bearing diorite from the Goryczkowa Unit was dated at 340 ± 4 Ma with apatite LREE depletion reflecting the role of allanite and titanite during apatite crystallization. Apatite crystals from a hybrid cumulative rock from the Western Tatra Mountains were dated at 344 ± 3 Ma. Apatite is one of the main REE carriers in this sample and exhibit flat REE patterns. Taking into account the relatively low closure temperature of the U-Pb system in apatite (350– 550°C), the c. 340 Ma apatite ages mark the end of high temperature tectonometamorphic activity in the Tatra Mountains.
The main products of volcanic activity in the teschenite-picrite association (TPA) are shallow, s... more The main products of volcanic activity in the teschenite-picrite association (TPA) are shallow, sub-volcanic intrusions, which predominate over extrusive volcanic rocks. They comprise a wide range of intrusive rocks which fall into two main groups: alkaline (teschenite, picrite, syenite, lamprophyre) and subalkaline (dolerite). Previous 40 Ar/ 39 Ar and 40 K/ 40 Ar dating of these rocks in the Polish Outer Western Carpathians, performed on kaersutite, sub-silicic dio-pside, phlogopite/biotite as well as on whole rock samples has yielded Early Cretaceous ages. Fluorapatite crystals were dated by the U-Pb LA-ICP-MS method to obtain the age of selected magmatic rocks (teschenite, lamprophyre) from the Cieszyn igneous province. Apatite-bearing samples from Boguszowice, Puńców and Lipowa yield U-Pb ages of 103± 20 Ma, 119.6 ± 3.2 Ma and 126.5 ± 8.8 Ma, respectively. The weighted average age for all three samples is 117.8 ± 7.3 Ma (MSWD =2.7). The considerably smaller dispersion in the apatite ages compared to the published amphibole and biotite ages is probably caused by the U-Pb system in apatite being less susceptible to the effects of hydrothermal alternation than the 40 Ar/ 39 Ar or 40 K/ 40 Ar system in amphibole and/or biotite. Available data suggest that volcanic activity in the Silesian Basin took place from 128 to 103 Ma with the the main magmatic phase constrained to 128—120 Ma.
Apatite is an important common U-and Th-bearing accessory mineral in igneous, metamorphic and cla... more Apatite is an important common U-and Th-bearing accessory mineral in igneous, metamorphic and clastic sed-imentary rocks. The advent of in situ U–Th–Pb apatite geochronology by the SIMS and LA-(MC)-ICP-MS methods has demonstrated the importance of having uniform and homogeneous reference materials. Recently, it has been shown that Sr and Nd isotopic data combined with U–Pb age and trace element concentration data can provide important constraints on apatite paragenesis because this phase usually exhibits high Sr and REE concentrations but has low Rb/Sr ratios which result in negligible corrections for the ingrowth of radiogenic Sr. However, as ap-atite can potentially have complex internal structures resulting from multiple thermal events, such as inherited cores and metamorphic overgrowths, requires that the Sr and Nd isotopic data should be measured with high spatial resolution. However isobaric interferences hamper the precise determination of Sr or Nd isotopic compositions in LA-MC-ICP-MS analysis. In this work we undertook in situ measurements of Sr and Nd isotopic compositions of eleven apatite reference materials (AP1, AP2, Durango, MAD, Otter Lake, NW-1, Slyudyanka, UWA-1, Mud Tank, McClure Mountain and SDG) commonly used in U–Th–Pb geochronology. Our obtained Sr and Sm– Nd isotopic compositions for these apatite samples are consistent with those values obtained by solution-based methods (isotope dilution and ion chromatography) using MC-ICP-MS or TIMS, which demonstrates the reliability and robustness of our analytical protocol.
We report experiments on optimisation of LA-ICP-MS mapping as a tool for visualising and quantify... more We report experiments on optimisation of LA-ICP-MS mapping as a tool for visualising and quantifying internal structure of trace element concentration in igneous minerals. The experimental design was refined with maps on clinopyroxene and amphibole macrocrysts (mainly antecrysts) from a porphyritic lamprophyre in NE Spain, as well as on a high precision metal wire grid. In terms of spatial resolution, we demonstrate with scanning electron microscope and white light interferometry that a full ablation removes between 0.4 and 0.7 μm of material, depending on ablation parameters. Maps were produced with square laser beam spots of 12 and 24 μm. It was found that complexities can be resolved in the sample even though they are smaller than the beam diameter (e.g., 7–10 μm discontinuities using 12 μm laser beam). Resolution in x and y was found to be identical, probably reflecting the fast washout of the two-volume ablation cell and the short total dwell time of the analyte menu selected. Due to the excellent stage reproducibility and the limited ablation depth, it is feasible to re-ablate the identical map area many times employing different instrument parameters or analyte menus. On the magmatic crystals, LA-ICP-MS maps define very sharp compositional zoning in trace elements, highlighting complex crystallisation histories where 'normal' magmatic fractionation is not the only process. Events of mafic recharge are easily recognised as zones enriched in compatible metals such as Cr, Ni or Sc. Further, trace element maps reveal complexities in mineral zoning previously undetectable with petrography or major element data. These include resorbed primitive cores and oscillatory zoning within apparently homogeneous mineral zones. Therefore, LA-ICP-MS mapping opens a new window of opportunity for analysis of magmatic histories. The wide combination of instrumental parameters, such as laser beam size, scan speed and repetition rate, make it possible to carry out experiments at different levels of detail. We recommend a two-step approach to mapping. The initial step involves rapid maps to gain an overview of potential complexities in the sample; this enhances representativeness of the analysed materials, as a large number of crystals and trace elements can be tested in little time. Subsequently, detailed maps can be carried out on areas of interest. An additional function-ality is to create 1D-profiles from 2D-maps. The potential of the technique to unveil compositional complexities efficiently and at greater detail than traditional microanalysis will help to improve our understanding of processes in the magmatic environment and beyond.
The Moatize-Minjova Basin is a Karoo-aged rift basin located in the Tete Province of central Moza... more The Moatize-Minjova Basin is a Karoo-aged rift basin located in the Tete Province of central Mozambique along the present-day Zambezi River valley. In this basin the Permian Moatize and Matinde formations consist of interbedded carbonaceous mudstones and sandstones with coal seams. The thermal history has been determined using rock samples from two coal exploration boreholes (ca. 500 m depth) to constrain the burial and exhumation history of the basin. Organic maturation levels were determined using vitrinite reflectance and spore fluorescence/colour. Ages and rates of tectonic uplift and denudation have been assessed by apatite fission track analysis. The thermal history was modelled by inverse modelling of the fission track and vitrinite reflectance data. The Moatize Formation attained a coal rank of bituminous coals with low to medium volatiles (1.3e1.7%Rr). Organic maturation levels increase in a linear fashion downhole in the two boreholes, indicating that burial was the main process controlling peak temperature maturation. Calculated palaeogeothermal gradients range from 59 C/km to 40 C/km. According to the models, peak burial temperatures were attained shortly (3e10 Ma) after deposition. Apatite fission track ages [146 to 84 Ma (Cretaceous)] are younger than the stratigraphic age. Thermal modelling indicates two episodes of cooling and exhumation: a first period of rapid cooling between 240 and 230 Ma (Middle e Upper Triassic boundary) implying 2500e3000 m of denudation; and a second period, also of rapid cooling, from 6 Ma (late Miocene) onwards implying 1000e1500 m of denudation. The first episode is related to the main compressional deformation event within the Cape Fold Belt in South Africa, which transferred stress northwards on pre-existing transtensional fault systems within the Karoo rift basins, causing tectonic inversion and uplift. During the Mesozoic and most of the Cenozoic the basin is characterized by very slow cooling. The second period of fast cooling and denudation during the Pliocene was likely related to the southward propagation of the East African Rift System into Mozambique.
Apatite incorporates variable and significant amounts of halogens (mainly F and Cl) in its crysta... more Apatite incorporates variable and significant amounts of halogens (mainly F and Cl) in its crystal structure, which can be used to determine the initial F and Cl concentrations of magmas. The amount of chlorine in the apatite lattice also exerts an important compositional control on the degree of fission-track annealing. Chlorine measurements in apatite have conventionally required electron probe microanalysis (EPMA). Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is increasingly used in apatite fission-track dating to determine U concentrations and also in simultaneous U-Pb dating and trace element measurements of apatite. Apatite Cl measurements by ICP-MS would remove the need for EPMA but the high (12.97 eV) first ionisation potential makes analysis challenging. Apatite Cl data were acquired using two analytical set-ups: a Resonetics M-50 193 nm ArF Excimer laser coupled to an Agilent 7700× quadrupole ICP-MS (using a 26 μm spot with an 8 Hz repetition rate) and a Photon Machines Analyte Excite 193 nm ArF Excimer laser coupled to a Thermo Scientific iCAP Qc (using a 30 μm spot with a 4 Hz repetition rate). Chlorine concentrations were determined by LA-ICP-MS (1140 analyses in total) for nineteen apatite occurrences, and there is a comprehensive EPMA Cl and F data set for 13 of the apatite samples. The apatite sample suite includes different compositions representative of the range likely to be encountered in natural apatites, along with extreme variants including two end-member chlorapatites. Between twenty-six and thirty-nine isotopes were determined in each apatite sample corresponding to a typical analytical protocol for integrated apatite fission track (U and Cl contents) and U-Pb dating, along with REE and trace element measurements. 35Cl backgrounds (present mainly in the argon gas) were ~ 45–65 kcps in the first set-up and ~ 4 kcps in the second set-up. 35Cl background-corrected signals ranged from ~ 0 cps in end-member fluorapatite to up to ~ 90 kcps in end-member chlorapatite. Use of a collision cell in both analytical set-ups decreased the low mass sensitivity by approximately an order of magnitude without improving the 35Cl signal-to-background ratio. A minor Ca isotope was used as the internal standard to correct for drift in instrument sensitivity and variations in ablation volume during sessions. The 35Cl/43Ca values for each apatite (10–20 analyses each) when plotted against the EPMA Cl concentrations yield excellently constrained calibration relationships, demonstrating the suitability of the analytical protocol and that routine apatite Cl measurements by ICP-MS are achievable.L'apatite contient des quantités variables et significatives d'halogènes (notamment F et Cl) dans sa structure cristalline qui peuvent être utilisées pour déterminer la concentration initiale en F et Cl des magmas. La quantité de chlore dans le réseau de l'apatite exerce également un contrôle compositionnel important sur le degré de recuit des traces de fission. Les mesures du chlore dans l'apatite ont conventionnellement nécessité la microanalyse par sonde électronique (EPMA). La spectrométrie de masse à source plasma couplée à l'ablation laser (LA-ICP-MS) est de plus en plus utilisé dans la datation sur traces de fission de l'apatite pour déterminer les concentrations en U et aussi pour la datation simultanées U-Pb et les mesures des éléments traces de l'apatite. Les mesures du Cl dans l'apatite par ICP-MS élimineraient la nécessité d'utiliser l'EPMA mais le fait que le premier potentiel d'ionisation (12.97 eV) soit haut rend l'analyse difficile. Les données du Cl dans l'apatite ont été acquises au moyen de deux systèmes analytiques: un laser ArF excimer 193 nm Resonetics M-50 couplé à un ICP-MS quadripôle Agilent 7700× (utilisant un spot de 26 µm avec un taux de répétition de 8 Hz) et un laser ArF excimer 193 nm Photon Machines Analyte Excite couplé à un Thermo Scientific iCAP Qc (en utilisant un spot 30 µm avec un taux de répétition de 4 Hz). Les concentrations en chlore ont été déterminées par LA-ICP-MS (1140 analyses au total) pour dix-neuf occurrences d'apatite, et il y a une complète base de données EPMA pour le Cl et le F pour treize des échantillons d'apatite. La suite comprend différents échantillons d'apatite représentant la gamme de compositions susceptible d'être rencontré dans les apatites naturelles, ainsi que des variantes extrêmes dont deux endmembers chlorapatites. Entre vingt-six et trente-neuf isotopes ont été déterminés dans chaque échantillon d'apatite ce qui correspond à un protocole classique d'analyse intégrée des traces de fission (teneurs en U et Cl) et datation U-Pb sur apatite, avec les mesures des REE et des éléments traces. Les bruits de fond du 35Cl (surtout présent dans le gaz argon) étaient d'environ 45–65 kcps pour le premier système d'analyse et d'environ 4 kcps pour le second système. Le signal corrigé du bruit de fond pour 35Cl varie de ~ 0 cps dans l'endmember fluorapatite jusqu'à environ 90 kcps pour l'endmember chlorapatite. L'utilisation d'une cellule de collision avec les deux types de systèmes d'analyse a diminué la sensibilité des faibles masses d'environ un ordre de grandeur sans pour autant améliorer le rapport signal-bruit de fond du 35Cl. Un isotope mineur du Ca a été utilisé comme étalon interne pour corriger la dérive de sensibilité de l'instrument et les variations du volume d'ablation au cours des séances d'analyse. Les valeurs 35Cl/43Ca pour chaque apatite (10–20 analyses chacune) lorsqu'elles sont reportées par rapport aux concentrations en Cl obtenu par EPMA produisent des relations d'étalonnage parfaitement contraintes, ce qui démontre la pertinence du protocole analytique et que les mesures de routine du Cl de l'apatite par ICP-MS sont réalisables.
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