A NEW COMPILATION OFELEMENT CONCENTRATIONS INTHE NATURAL RIVER WATERSTANDARD SLRS-6 (NRC-CNRC)

International audienceIn Geosciences, there are only few natural river watercertified reference materials to ensure the quality of theroutine consentration's determination. One of thoseCRM is provided by the NRC-CNRC and called SLRS.Actually, the SLRS-6 has been released. However,there is only 19 elements having their concentrationcertified. Those elements are used to validate themeaasurements. Therefore, when a larger investigationis done, which is the case for the laboratories implied inthe CNRS "Isotrace" consortium, it is relativelylimitant.As done for the previous version of the SLRS (4-5) ourconsortium, working on major and trace elements innatural water, studied in details the CRM SLRS-6.They validated the measurement on the 19 certifiedelements and went further by determining other noncertifiedelements based on regular analysis of themusing ICP-MS and ICP-OES.We now offer a compilation of values for about 20trace elements, including Rare Earth Elements, whichare not certified by the producer as well as for silicon.Values are determined using robust mean and theirassociated expanded uncertainties. The Sr isotopic ratiois also proposed.Thi

An Alternative Protocol for Single Zircon Dissolution with Application to (U-Th-Sm)/He Thermochronometry

International audienceZircon (U‐Th‐Sm)/He (ZHe) thermochronometry is a powerful tool that has been widely used in geology to constrain the exhumation histories of orogens. In this study, we present an alternative protocol for dissolving zircon grains for determination of parent nuclides. This new alkali fusion procedure developed at the SARM (Service d'Analyse des Roches et des Minéraux) in Nancy, France, is fast (requiring only 2 d, including cleaning steps) and offers several advantages over conventional methods by avoiding: (i) use of HF pressure dissolution and (ii) complete removing of grains from the metal microvials. After dissolution, U, Th and Sm were measured using an ICP‐MS. We tested the new procedure on two different ZHe reference materials, the Fish Canyon Tuff and Buluk Tuff; these provided precision values for ZHe‐age estimations of 9 and 6% (1s), respectively. In addition, using this method, zircons from the Buluk Tuff are shown to be chemically more homogenous and more suitable for assessing the uncertainty of the entire integrated procedure

Caractérisation du standard d’eau derivière SLRS-5 (NRC-CNRC) compilationinterlaboratoire du silicium, des terresrares et de 21 autres éléments en trace

National audienceLe standard d’eau de rivière naturelle SLRS-5 (NRC-CNRC) est uneréférence de contrôle qualité en analyse d’eau de routine pour la communautéinternationale. Dix laboratoires français étudiant les élémentsmajeurs et en trace dans les solutions naturelles (groupe de travail del’atelier du CNRS « Isotrace ») valident leurs mesures avec les 19 élémentscertifiés par le producteur. Or, d’autres éléments non certifiés sontrégulièrement analysés par ces laboratoires qui ont comparé et compilé2 années de leurs mesures sur ce standard d’eau. La plupart desmesures sont réalisées par ICP-MS (Inductively Coupled Plasma Mass-Spectrometry).Dans un premier temps, il a été vérifié que les résultats obtenus étaientcohérents pour les éléments certifiés par le producteur. Ainsi Ba présenteune valeur compilée de 14,2 1,4 g/l (330 mesures issues de 9laboratoires participants) en accord avec la valeur certifiée de 14 0,5g/l.Ensuite, des valeurs moyennes et leurs incertitudes associées sont proposéespour des éléments non certifiés par NRC-CNRC tels que le siliciumet 35 éléments en trace (terres rares, Ag, B, Bi, Cs, Ga, Ge, Li, Nb,P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl,W, Y et Zr). Le rapport isotopique deSr est aussi proposé à partir de mesures par TIMS (Thermo IonisationMass Spectrometry).Il apparaît que les mesures individuelles et compilées varient dequelques ng/l à 2400 g/l avec des incertitudes associées comprisesentre 2 et 240%. Les fortes incertitudes associées ne sont pas proportionnellesaux concentrations puisque certaines mesures s’accordent mêmeà de faibles teneurs tels que Bi (0,9 0,3 ng/l valeur compilée). Danscertains cas, un ou deux laboratoires ont caractérisé l’élément impliquantmoins de mesures et une incertitude associée plus élevée quelleque soit la concentration en l’élément. C’est le cas, par exemple, de Ge(0,015 0,014 g/l valeur compilée) caracterisé par seulement 2 laboratoires(34 mesures) et de P (8,19 3,40 g/l) issu de 8 mesuresd’un seul laboratoire. Les terres rares et onze autres éléments (B, Bi,Cs, Li, Rb, Si, Th, Ti, Tl, Y et Zr) ont été déterminés par au moins 3laboratoires différents et apportent des informations complémentairesessentielles à l’utilisatio

Caractérisation du standard d’eau de rivièreslrs-6 (nrc-cnrc) compilation interlaboratoiredu silicium, des terres rares et de 21 autreséléments en trace

National audienceL’analyse des eaux nécessite, généralement, des matériaux deréférence certifiés afin d’assurer la qualité des mesures. En Géosciences,il existe peu de standards d’eau de rivière naturelle ayantun nombre important d’éléments certifiés. Or, depuis plusieursannées, une dizaine de laboratoires étudient les éléments majeurset en traces dans les solutions naturelles (groupe de travail del’atelier du CNRS ”Isotrace”) et valident leurs mesures avec les19 éléments certifiés de l’eau de rivière d’Ottawa SLRS produitpar le NRC-CNRC. D’autres éléments non certifiés de cette eausont régulièrement analysés par ces laboratoires à l’aide d’ICP-MS(Inductively Coupled Plasma Mass-Spectrometry) et d’ICP-OES(Inductively Coupled Plasma Optical-Emission Spectrometry).Ces travaux ont fait l’objet de deux publications sur les lots SLRS-4 et SLRS-5. Le nouveau lot SLRS-6 est disponible depuis fin 2015et le groupe de travail propose, dès à présent, les valeurs pour unevingtaine d’éléments en traces non certifiés par le producteur.Comme pour les lots précédents, il a été vérifié que les résultatsobtenus étaient cohérents pour les éléments certifiés par le producteur.Ensuite, des valeurs moyennes et leurs incertitudes associées sontproposées pour des éléments non certifiés par NRC-CNRC telsque le silicium et une vingtaine d’éléments en traces dont les terresrares.L’ensemble des valeurs obtenues est comparé au lot SLRS-5 précédent: SLRS-6 est caractérisé par des teneurs généralement plusfaibles que SLRS-5 ce qui en fait un matériau plus difficile àétudier, proches des limites de détection des techniques utilisées.Enfin, pour comprendre les biais éventuels observés dans les laboratoires,il est aussi discuté individuellement des variations pourchaque élément

Late Jurassic Oceanic Crust and Upper Cretaceous Caribbean Plateau Picritic Basalts Exposed in the Duarte Igneous Complex, Hispaniola

International audienceFour distinct rock units have been recognized near El Aguacate, in the Janico–Juncalito–La Vega area of the Duarte complex (Dominican Republic): (1) serpentinites crosscut by numerous diabasic dikes, (2) basalts interbedded with Late Jurassic ribbon cherts, (3) picrites and ankaramites relatively enriched in incompatible trace elements, and (4) amphibolites and gneissic amphibolites chemically similar to Oceanic Plateau Basalts. Similar Ar-Ar ages of late magmatic amphibole from a picrite, and hornblende from an amphibolite ( (86.1 ± 1.3 Ma and 86.7 ± 1.6 Ma respectively), suggest that the Duarte picrites are contemporaneous with the Deep Sea Drilling Program Leg 15 and Ocean Drilling Program Leg 126 basalts drilled from the Caribbean oceanic plateau. These basalts are associated with sediments containing Late Cretaceous faunas. Sr, Nd, and Pb data show that enriched picrites and amphibolites are isotopically similar to mafic lavas from previously described Caribbean plateau and Gala´pagos hotspot basalts. Major element, trace element, and lead isotopic features of Late Jurassic basalts and diabases are consistent with those of normal oceanic crust basalt. However, these basalts differ from typical N-MORB because they have lower eNd ratios that plot within the range of Ocean Island Basalts. These rocks appear to represent remnants of the Caribbean Jurassic oceanic crust formed from an oceanic ridge possibly close to a hotspot. Later, they were tectonically juxtaposed with Late Cretaceous slices of the Caribbean-Colombian plateau

Characterisation of Reference Materials for In situ Rb-Sr Dating by LA-ICP-MS/MS

International audienceWe present here Rb and Sr mass fractions and 87 Sr/ 86 Sr compositions for four reference materials (RM) obtained from the Service d'Analyse des Roches et des Minéraux (SARM) in Nancy, France: Mica-Mg, Mica-Fe, GL-O and FK-N. These four RMs have different chemical compositions spanning the range of those of most K-bearing feldspars and micas, making them potential calibration materials for in situ Rb-Sr dating of natural minerals by LA-ICP-MS/MS. Selected grains and flakes from the four RMs present variable degrees of heterogeneity observable by SEM-EDS and EPMA imaging and chemical mapping. This heterogeneity is mainly related to inclusions of minerals within flakes and grains and to chemical substitutions linked to crystallographic control and alteration processes. The Mica-Mg RM is the least affected. The powders available at the SARM were analysed by ID-TIMS (87 Sr/ 86 Sr and Sr mass fractions) and ID-MC-ICP-MS (Rb) after digestion and separation. The mean 87 Rb/ 86 Sr ratios are 155.6 ± 4.7% (2s, as for other RMs) for Mica-Mg, 1815 ± 14% for Mica-Fe, 36.2 ± 11% for GL-O and 69.9 ± 5.9% for FK-N. The mean 87 Sr/ 86 Sr ratios are 1.8622 ± 0.36% (2s, as for other RMs) for Mica-Mg, 7.99 ± 13% for Mica-Fe, 0.75305 ± 0.12% for GL-O, and 1.2114 ± 0.17% for FK-N. The four RMs each show dispersion in 87 Sr/ 86 Sr and Rb and Sr mass fractions, to degrees that differ between RMs and that reflect the heterogeneity of their original crystals. The most heterogeneous RMs are GL-O and Mica-Fe. The calculated mean Rb-Sr isotopic ages are 521 ± 24 Ma for Mica-Mg, 287 ± 55 Ma for Mica-Fe, 89.2 ± 9.9 Ma for GL-O and 512 ± 30 Ma for FK-N. The proposed age for Mica-Fe may be unreliable due to the elevated dispersion of individual analysis linked to the highly radiogenic composition of the biotite and to the presence of numerous mineral inclusions. We recommend use of these proposed working values of 87 Sr/ 86 Sr and 87 Rb/ 86 Sr ratios and associated uncertainties when using the four RMs for in situ Rb-Sr dating by LA-ICP-MS/MS. The availability of these four well-characterised RM will allow progress in the development and application of the Rb-Sr dating approach by LA-ICP-MS/MS

Late Jurassic Oceanic Crust and Upper Cretaceous Caribbean Plateau Picritic Basalts Exposed in the Duarte Igneous Complex, Hispaniola

International audienceFour distinct rock units have been recognized near El Aguacate, in the Janico–Juncalito–La Vega area of the Duarte complex (Dominican Republic): (1) serpentinites crosscut by numerous diabasic dikes, (2) basalts interbedded with Late Jurassic ribbon cherts, (3) picrites and ankaramites relatively enriched in incompatible trace elements, and (4) amphibolites and gneissic amphibolites chemically similar to Oceanic Plateau Basalts. Similar Ar-Ar ages of late magmatic amphibole from a picrite, and hornblende from an amphibolite ( (86.1 ± 1.3 Ma and 86.7 ± 1.6 Ma respectively), suggest that the Duarte picrites are contemporaneous with the Deep Sea Drilling Program Leg 15 and Ocean Drilling Program Leg 126 basalts drilled from the Caribbean oceanic plateau. These basalts are associated with sediments containing Late Cretaceous faunas. Sr, Nd, and Pb data show that enriched picrites and amphibolites are isotopically similar to mafic lavas from previously described Caribbean plateau and Gala´pagos hotspot basalts. Major element, trace element, and lead isotopic features of Late Jurassic basalts and diabases are consistent with those of normal oceanic crust basalt. However, these basalts differ from typical N-MORB because they have lower eNd ratios that plot within the range of Ocean Island Basalts. These rocks appear to represent remnants of the Caribbean Jurassic oceanic crust formed from an oceanic ridge possibly close to a hotspot. Later, they were tectonically juxtaposed with Late Cretaceous slices of the Caribbean-Colombian plateau

Late Jurassic Oceanic Crust and Upper Cretaceous Caribbean Plateau Picritic Basalts Exposed in the Duarte Igneous Complex, Hispaniola

International audienceFour distinct rock units have been recognized near El Aguacate, in the Janico–Juncalito–La Vega area of the Duarte complex (Dominican Republic): (1) serpentinites crosscut by numerous diabasic dikes, (2) basalts interbedded with Late Jurassic ribbon cherts, (3) picrites and ankaramites relatively enriched in incompatible trace elements, and (4) amphibolites and gneissic amphibolites chemically similar to Oceanic Plateau Basalts. Similar Ar-Ar ages of late magmatic amphibole from a picrite, and hornblende from an amphibolite ( (86.1 ± 1.3 Ma and 86.7 ± 1.6 Ma respectively), suggest that the Duarte picrites are contemporaneous with the Deep Sea Drilling Program Leg 15 and Ocean Drilling Program Leg 126 basalts drilled from the Caribbean oceanic plateau. These basalts are associated with sediments containing Late Cretaceous faunas. Sr, Nd, and Pb data show that enriched picrites and amphibolites are isotopically similar to mafic lavas from previously described Caribbean plateau and Gala´pagos hotspot basalts. Major element, trace element, and lead isotopic features of Late Jurassic basalts and diabases are consistent with those of normal oceanic crust basalt. However, these basalts differ from typical N-MORB because they have lower eNd ratios that plot within the range of Ocean Island Basalts. These rocks appear to represent remnants of the Caribbean Jurassic oceanic crust formed from an oceanic ridge possibly close to a hotspot. Later, they were tectonically juxtaposed with Late Cretaceous slices of the Caribbean-Colombian plateau

Late Jurassic Oceanic Crust and Upper Cretaceous Caribbean Plateau Picritic Basalts Exposed in the Duarte Igneous Complex, Hispaniola

International audienceFour distinct rock units have been recognized near El Aguacate, in the Janico–Juncalito–La Vega area of the Duarte complex (Dominican Republic): (1) serpentinites crosscut by numerous diabasic dikes, (2) basalts interbedded with Late Jurassic ribbon cherts, (3) picrites and ankaramites relatively enriched in incompatible trace elements, and (4) amphibolites and gneissic amphibolites chemically similar to Oceanic Plateau Basalts. Similar Ar-Ar ages of late magmatic amphibole from a picrite, and hornblende from an amphibolite ( (86.1 ± 1.3 Ma and 86.7 ± 1.6 Ma respectively), suggest that the Duarte picrites are contemporaneous with the Deep Sea Drilling Program Leg 15 and Ocean Drilling Program Leg 126 basalts drilled from the Caribbean oceanic plateau. These basalts are associated with sediments containing Late Cretaceous faunas. Sr, Nd, and Pb data show that enriched picrites and amphibolites are isotopically similar to mafic lavas from previously described Caribbean plateau and Gala´pagos hotspot basalts. Major element, trace element, and lead isotopic features of Late Jurassic basalts and diabases are consistent with those of normal oceanic crust basalt. However, these basalts differ from typical N-MORB because they have lower eNd ratios that plot within the range of Ocean Island Basalts. These rocks appear to represent remnants of the Caribbean Jurassic oceanic crust formed from an oceanic ridge possibly close to a hotspot. Later, they were tectonically juxtaposed with Late Cretaceous slices of the Caribbean-Colombian plateau

Late Jurassic Oceanic Crust and Upper Cretaceous Caribbean Plateau Picritic Basalts Exposed in the Duarte Igneous Complex, Hispaniola

International audienceFour distinct rock units have been recognized near El Aguacate, in the Janico–Juncalito–La Vega area of the Duarte complex (Dominican Republic): (1) serpentinites crosscut by numerous diabasic dikes, (2) basalts interbedded with Late Jurassic ribbon cherts, (3) picrites and ankaramites relatively enriched in incompatible trace elements, and (4) amphibolites and gneissic amphibolites chemically similar to Oceanic Plateau Basalts. Similar Ar-Ar ages of late magmatic amphibole from a picrite, and hornblende from an amphibolite ( (86.1 ± 1.3 Ma and 86.7 ± 1.6 Ma respectively), suggest that the Duarte picrites are contemporaneous with the Deep Sea Drilling Program Leg 15 and Ocean Drilling Program Leg 126 basalts drilled from the Caribbean oceanic plateau. These basalts are associated with sediments containing Late Cretaceous faunas. Sr, Nd, and Pb data show that enriched picrites and amphibolites are isotopically similar to mafic lavas from previously described Caribbean plateau and Gala´pagos hotspot basalts. Major element, trace element, and lead isotopic features of Late Jurassic basalts and diabases are consistent with those of normal oceanic crust basalt. However, these basalts differ from typical N-MORB because they have lower eNd ratios that plot within the range of Ocean Island Basalts. These rocks appear to represent remnants of the Caribbean Jurassic oceanic crust formed from an oceanic ridge possibly close to a hotspot. Later, they were tectonically juxtaposed with Late Cretaceous slices of the Caribbean-Colombian plateau