15 research outputs found
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 (UâThâSm)/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 MinĂ©raux) 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 ICPâMS. We tested the new procedure on two different ZHe reference materials, the Fish Canyon Tuff and Buluk Tuff; these provided precision values for ZHeâage 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
CaractĂ©risation du standard dâeau deriviĂšre SLRS-5 (NRC-CNRC) compilationinterlaboratoire du silicium, des terresrares et de 21 autres Ă©lĂ©ments en trace
National audienceLe standard dâeau de riviĂšre naturelle SLRS-5 (NRC-CNRC) est unerĂ©fĂ©rence de contrĂŽle qualitĂ© en analyse dâeau de routine pour la communautĂ©internationale. Dix laboratoires français Ă©tudiant les Ă©lĂ©mentsmajeurs et en trace dans les solutions naturelles (groupe de travail delâatelier du CNRS « Isotrace ») valident leurs mesures avec les 19 Ă©lĂ©mentscertifiĂ©s par le producteur. Or, dâautres Ă©lĂ©ments non certifiĂ©s sontrĂ©guliĂšrement analysĂ©s par ces laboratoires qui ont comparĂ© et compilĂ©2 annĂ©es de leurs mesures sur ce standard dâeau. La plupart desmesures sont rĂ©alisĂ©es par ICP-MS (Inductively Coupled Plasma Mass-Spectrometry).Dans un premier temps, il a Ă©tĂ© vĂ©rifiĂ© que les rĂ©sultats obtenus Ă©taientcohĂ©rents pour les Ă©lĂ©ments certifiĂ©s par le producteur. Ainsi Ba prĂ©senteune valeur compilĂ©e de 14,2 1,4 g/l (330 mesures issues de 9laboratoires participants) en accord avec la valeur certifiĂ©e de 14 0,5g/l.Ensuite, des valeurs moyennes et leurs incertitudes associĂ©es sont proposĂ©espour des Ă©lĂ©ments non certifiĂ©s par NRC-CNRC tels que le siliciumet 35 Ă©lĂ©ments 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 proposĂ© Ă partir de mesures par TIMS (Thermo IonisationMass Spectrometry).Il apparaĂźt que les mesures individuelles et compilĂ©es varient dequelques ng/l Ă 2400 g/l avec des incertitudes associĂ©es comprisesentre 2 et 240%. Les fortes incertitudes associĂ©es ne sont pas proportionnellesaux concentrations puisque certaines mesures sâaccordent mĂȘmeĂ de faibles teneurs tels que Bi (0,9 0,3 ng/l valeur compilĂ©e). Danscertains cas, un ou deux laboratoires ont caractĂ©risĂ© lâĂ©lĂ©ment impliquantmoins de mesures et une incertitude associĂ©e plus Ă©levĂ©e quelleque soit la concentration en lâĂ©lĂ©ment. Câest le cas, par exemple, de Ge(0,015 0,014 g/l valeur compilĂ©e) caracterisĂ© par seulement 2 laboratoires(34 mesures) et de P (8,19 3,40 g/l) issu de 8 mesuresdâun seul laboratoire. Les terres rares et onze autres Ă©lĂ©ments (B, Bi,Cs, Li, Rb, Si, Th, Ti, Tl, Y et Zr) ont Ă©tĂ© dĂ©terminĂ©s par au moins 3laboratoires diffĂ©rents et apportent des informations complĂ©mentairesessentielles Ă lâutilisatio
CaractĂ©risation du standard dâeau de riviĂšreslrs-6 (nrc-cnrc) compilation interlaboratoiredu silicium, des terres rares et de 21 autresĂ©lĂ©ments en trace
National audienceLâanalyse des eaux nĂ©cessite, gĂ©nĂ©ralement, des matĂ©riaux derĂ©fĂ©rence certifiĂ©s afin dâassurer la qualitĂ© des mesures. En GĂ©osciences,il existe peu de standards dâeau de riviĂšre naturelle ayantun nombre important dâĂ©lĂ©ments certifiĂ©s. Or, depuis plusieursannĂ©es, une dizaine de laboratoires Ă©tudient les Ă©lĂ©ments majeurset en traces dans les solutions naturelles (groupe de travail delâatelier du CNRS âIsotraceâ) et valident leurs mesures avec les19 Ă©lĂ©ments certifiĂ©s de lâeau de riviĂšre dâOttawa SLRS produitpar le NRC-CNRC. Dâautres Ă©lĂ©ments non certifiĂ©s de cette eausont rĂ©guliĂšrement analysĂ©s par ces laboratoires Ă lâaide dâICP-MS(Inductively Coupled Plasma Mass-Spectrometry) et dâICP-OES(Inductively Coupled Plasma Optical-Emission Spectrometry).Ces travaux ont fait lâobjet 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, dĂšs Ă prĂ©sent, les valeurs pour unevingtaine dâĂ©lĂ©ments en traces non certifiĂ©s par le producteur.Comme pour les lots prĂ©cĂ©dents, il a Ă©tĂ© vĂ©rifiĂ© que les rĂ©sultatsobtenus Ă©taient cohĂ©rents pour les Ă©lĂ©ments certifiĂ©s par le producteur.Ensuite, des valeurs moyennes et leurs incertitudes associĂ©es sontproposĂ©es pour des Ă©lĂ©ments non certifiĂ©s par NRC-CNRC telsque le silicium et une vingtaine dâĂ©lĂ©ments en traces dont les terresrares.Lâensemble des valeurs obtenues est comparĂ© au lot SLRS-5 prĂ©cĂ©dent: SLRS-6 est caractĂ©risĂ© par des teneurs gĂ©nĂ©ralement plusfaibles que SLRS-5 ce qui en fait un matĂ©riau plus difficile Ă Ă©tudier, proches des limites de dĂ©tection des techniques utilisĂ©es.Enfin, pour comprendre les biais Ă©ventuels observĂ©s dans les laboratoires,il est aussi discutĂ© individuellement des variations pourchaque Ă©lĂ©ment
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 JanicoâJuncalitoâLa 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 GalaÂŽpagos 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 JanicoâJuncalitoâLa 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 GalaÂŽpagos 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 JanicoâJuncalitoâLa 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 GalaÂŽpagos 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 JanicoâJuncalitoâLa 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 GalaÂŽpagos 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 JanicoâJuncalitoâLa 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 GalaÂŽpagos 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