Centre de Recherches Pétrographiques et Géochimiques

We report here the results of a study to develop natural zircon geochemical standards for calibrating the U‐(Th)‐Pb geochronometer and Hf isotopic analyses. Additional data were also collected for the major, minor and trace element contents of the three selected sample sets. A total of five large zircon grains (masses between 0.5 and 238 g) were selected for this study, representing three different suites of zircons with ages of 1065 Ma, 2.5 Ma and 0.9 Ma. Geochemical laboratories can obtain these materials by contacting Geostandards Newsletter.

In this Special Issue, working values are reported for 383 international geostandards along with sample description. All this information is available in the form of databases. The possibility of easily accessing data on geostandards from a microcomputer in the laboratory itself is an efficient means for handling quality control/ quality assurance problems.

Within a short period of one year (November 1992‐ October 1993), ninety‐two IWG‐Member laboratories have been able to characterize the chemical composition of a candidate reference sample, Zinnwaldite ZW‐C, a Li‐mica, reputed difficult to analyse because of its high contents of F and rare alkali elements and of the presence of refractory minerals. Thanks to the help of 163 analysts from the 92 laboratories, it has been possible to assign working values for 20 major and minor elements including the rare alkali elements and for 43 trace elements; all the working values receive the status of recommended values, except H20, C02, LOI, CI and S. It is, indeed, a rare success for such a difficult sample!

ABSTRACT A classification is proposed, based mainly on major element analytical data plotted in a coherent set of three simple chemical-mineralogical diagrams. The procedure follows two complementary steps at two different levels. The first is concerned with the individual sample: the sample is given a name (e.g. granite, adamellite, granodiorite) and its chemical and mineralogical characteristics are determined. The second one is more important: it aims at defining the type of magmatic association (or series) to which the studied sample or group of samples belongs. Three main types of association are distinguished: cafemic (from source-material mainly or completely mantle-derived), aluminous (mainly or completely derived by anatexis of continental crust), and alumino-cafemic (intermediate between the other two types). Subtypes are then distinguished among the cafemic and alumino-cafemic associations: calc-alkaline (or granodioritic), subalkaline (or monzonitic), alkaline (and peralkaline), tholeiitic (or gabbroic-trondhjemitic), etc. In the same way, numerous subtypes and variants are also distinguished among the aluminous associations using a set of complementary criteria such as quartz content, colour index, alkali ratio, quartz–alkalies relationships and alumina index. Although involving a new approach using partly new criteria, this classification is consistent with most of the divisions used in previous typologies. The method may also be used in the classification of the volcanic equivalents of common plutonic rocks.

In this special issue, working values are reported for 272 international geostandards along with sample description. For many geostandards, the number of compiled data were not adequate enough for assigning working values. Users of geostandards are solicited to contribute more and more data particularly on trace elements. Think Geostan is a slogan that we wish to launch to set this problem in the limelight.

Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.

Research Article| January 01, 2002 Noble Gases and Volatile Recycling at Subduction Zones David R. Hilton; David R. Hilton Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, California 92093, drhilton@ucsd.edu Search for other works by this author on: GSW Google Scholar Tobias P. Fischer; Tobias P. Fischer Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, New Mexico 87131 Search for other works by this author on: GSW Google Scholar Bernard Marty Bernard Marty Centre de Recherches Petrographiques et Geochimiques (CRPG), 15 Rue Notre-Dame des Pauvres, B.P. 20, 54501 Vandoeuvre les Nancy Cedex, France Search for other works by this author on: GSW Google Scholar Reviews in Mineralogy and Geochemistry (2002) 47 (1): 319–370. https://doi.org/10.2138/rmg.2002.47.9 Article history first online: 13 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David R. Hilton, Tobias P. Fischer, Bernard Marty; Noble Gases and Volatile Recycling at Subduction Zones. Reviews in Mineralogy and Geochemistry 2002;; 47 (1): 319–370. doi: https://doi.org/10.2138/rmg.2002.47.9 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyReviews in Mineralogy and Geochemistry Search Advanced Search Volatiles are lost from the Earth's mantle to the atmosphere, hydrosphere and crust through a combination of subaerial and submarine volcanic and magmatic activity. These volatiles can be primordial in origin, trapped in the mantle since planetary accretion, produced in situ, or they may be recycled—re-injected into the mantle via material originally at the surface through the subduction process. Quantifying the absolute and relative contributions of these various volatile sources bears fundamental information on a number of issues in the Earth Sciences ranging from the evolution of the atmosphere and hydrosphere to the nature and scale of chemical heterogeneity in... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

We describe analytical procedures for trace element determinations developed at the CNRS Service d'Analyse des Roches et des Minéraux (SARM) and report results obtained for five geochemical reference materials: basalt BR, diorite DR‐N, serpentinite UB‐N, anorthosite AN‐G and granite GH. Results for rare earth elements, U and Th are also reported for other reference materials including dunite DTS‐1, peridotite PCC‐1 and basalt BIR‐1. All rocks were decomposed using alkali fusion. Analyses were done by flow injection ICP‐MS and by on‐line low pressure liquid chromatography (LC)‐ICP‐MS for samples containing very low REE, U and Th concentrations. This latter method yielded limits of determination much lower than data by direct introduction and eliminated possible isobaric interference on these elements. Although results agree with most of the working values, when available, results for some elements differed slightly from the recommended concentrations. In these cases, we propose new values for Co, Y and Zn in basalt BR, Zr in diorite DR‐N, Sr and U in granite GH, and Ga and Y in anorthosite AN‐G. Furthermore, although the Sb concentration measured in AN‐G was very close to our limit of determination, our value (0.3 ± 0.1 μg g −1 ) is much lower than the reported working value of 1.4 ± 0.2 μg g −1 . These new values would need to be confirmed by a new inter‐laboratory programme to further characterise these reference materials. Results obtained for REE, Th and U concentrations using the on‐line low pressure LC‐ICP‐MS yielded good limits of determination (ng g −1 to sub‐ng g −1 for rocks and ng l −1 to sub‐ng l −1 for natural waters) and accurate results. The efficiency of the matrix separation allowed accurate measurements of Eu without the need to correct the BaO isobaric interference for samples having Ba/Eu ratios as high as 27700. For REE concentrations in PCC‐1 and DTS‐1, differences with values reported in the literature are interpreted as resulting from possible heterogeneity of the reference materials. Thorium and U values are proposed for these two samples, as well as for AN‐G and UB‐N.

The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the Stardust mission after the flyby at comet Wild 2, the simplest form of amino acids, glycine, has been found together with precursor molecules methylamine and ethylamine. Because of contamination issues of the samples, a cometary origin was deduced from the (13)C isotopic signature. We report the presence of volatile glycine accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer, confirming the Stardust results. Together with the detection of phosphorus and a multitude of organic molecules, this result demonstrates that comets could have played a crucial role in the emergence of life on Earth.

The provenance of water and organic compounds on Earth and other terrestrial planets has been discussed for a long time without reaching a consensus. One of the best means to distinguish between different scenarios is by determining the deuterium-to-hydrogen (D/H) ratios in the reservoirs for comets and Earth's oceans. Here, we report the direct in situ measurement of the D/H ratio in the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard the European Space Agency's Rosetta spacecraft, which is found to be (5.3 ± 0.7) × 10(-4)—that is, approximately three times the terrestrial value. Previous cometary measurements and our new finding suggest a wide range of D/H ratios in the water within Jupiter family objects and preclude the idea that this reservoir is solely composed of Earth ocean-like water.

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Abstract Methods previously used to distinguish between water adsorbed on external surfaces and in the interlamellar space of Na-montmorillonite during adsorption and desorption of water vapor have been extended to a set of homoionic Li-, Na-, K-, Rb- and Cs-montmorillonite. The textural and structural features have been investigated at different stages of hydration and dehydration using controlled-rate thermal analysis, nitrogen adsorption volumetry, water adsorption gravimetry, immersion microcalorimetry and X-ray powder diffraction under controlled humidity conditions. During hydration, the size of the quasi-crystals decreases from 33 layers to 8 layers for Na-montmorillonite and from 25 layers to 10 layers for K-montmorillonite, but remains stable around 8–11 layers for Cs-montmorillonite. Each homoionic species leads to a one-layer hydrate, which starts forming at specific values of water vapor relative pressure. Li-, Na- and K-montmorillonite can form a two-layer hydrate. By comparing experimental X-ray diffraction patterns with theoretically simulated ones, the evolution of structural characteristics of montmorillonites during hydration or desorption can be described. Using structural and textural data, it is shown that during adsorption: (1) the rate of filling of interlamellar space of the one layer hydrate increases with the relative pressure but decreases with the size of the cations; and (2) the different hydrated states are never homogeneous.

Multicollector ICP-MS has been used for the precise measurement of variations in the isotopic composition of the isotopic standard of magnesium (SRM980) provided by the National Institute of Standards and Technology (Gaithersburg, MD, USA). The SRM980 consists of metal chips weighing between 1 and 50 mg and each unit delivered by the National Institute of Standards and Technology corresponds to a bottle containing about 0.3 g. Height units were analysed. Variations in sample 25Mg/24Mg, and 26Mg/24Mg ratios are expressed as δ25Mg and δ26Mg units, respectively, which are deviations in parts per 103 from the same ratio in a standard solution. The differences in δ25Mg and δ26Mg of the SRM980 are up to 4.20 and 8.19‰, respectively, while the long-term repeatability of δ25Mg and δ26Mg are 0.09 and 0.16‰, respectively, at 95% confidence. However, when plotted in a three-isotope diagram, all the data fall on a single mass fractionation line. Overall limits of error of the SRM980 reported here fall within the previously reported overall limits of error. The isotopic heterogeneity not only corresponds to differences among units but has been found at the chip-size level. This result, due to the precision of the MC-ICP-MS technique, makes the SRM980 inappropriate for the international isotopic standard of magnesium. The SRM980 can still be used to report the excess of 26Mg, which is defined by the deviation from the mass-dependent relationship between 25Mg/24Mg, and 26Mg/24Mg ratios. Two large batches (around 10 g of Mg in each) of pure Mg solutions (in 0.3 M HNO3) have been prepared and characterised. These 2 solutions (DSM3 and Cambridge 1) are suitable reference material because they are immune to heterogeneity. DSM3 and Cambridge 1 are isotopically different (by 1.3‰ per u) and are available upon request from the first author. In addition, DSM3 has an isotopic composition very similar to the Mg-isotopic composition of carbonaceous chondrites (Orgueil and Allende). Because of the lack of heterogeneity and the cosmochemical and geochemical significance of DSM3, we urge the use of DSM3 as the primary isotopic reference material to report Mg-isotopic variations.

Residual solid products of erosion display a wide range of size, density, shape, mineralogy, and chemical composition and are hydrodynamically sorted in large river channels during their transport. We characterize the chemical and isotopic variability of river sediments of the Amazon Basin, collected at different water depths, as a function of grain size. Absolute chemical concentrations and Sr and Nd isotopic ratios greatly varies along channel depth. The Al/Si ratio, tightly linked to grain size distribution, systematically decreases with depth, mostly reflecting dilution by quartz minerals. A double‐normalization diagram is proposed to correct from dilution effects. Elements define fan‐shaped patterns and can be classified in three different groups with respect to hydrodynamic sorting during transport in the Amazon: (1) “poorly sorted” insoluble elements like Al, Fe, Th, and REEs, (2) “well‐sorted” insoluble elements like Zr and Ti, mainly carried by heavy minerals, and (3) alkali (Na to Cs) and alkali‐earth elements (Mg to Ba), for which a large variety of patterns is observed, related, for alkali, to their variable affinity for phyllosilicates. Sr isotopes show that the Amazon River at the mouth is stratified, the Madeira‐ and Solimões‐derived sediments being preferentially transported near the channel surface and at depth, respectively. The comparison between the Solimões and Madeira rivers shows how the interplay between grain sorting, weathering, and crustal composition controls the composition of the suspended river sediments.

The chemical weathering of rocks with sulfuric acid is usually not considered in reconstructions of the past evolution of the carbon cycle, although this reaction delivers cations and alkalinity to the ocean without involvement of atmospheric CO2. The contribution of sulfuric acid as a weathering agent is still poorly quantified; the identification of riverine sulfate sources is difficult. The use of {delta}34S and {delta}18O of dissolved sulfate allows us to demonstrate that most of the sulfate in surface waters of the Mackenzie River system, Canada, derives from pyrite oxidation (85% {+/-} 5%) and not from sedimentary sulfate. The calculated flux of pyrite-derived sulfate is 0.13 x 1012 mol/yr, corresponding to 20%-27% of the estimated global budget. This result suggests that the modern global ocean delivery of sulfide-derived sulfate, and thus chemical weathering with sulfuric acid, may be significantly underestimated. A strong correlation between sulfide oxidation rates and mechanical erosion rates suggests that the exposure of fresh mineral surfaces is the rate-limiting factor of sulfide oxidation in the subbasins investigated. The chemical weathering budget of the Mackenzie River shows that more than half of the dissolved inorganic carbon discharged to the ocean is ancient sedimentary carbon from carbonate (62%) and not atmospheric carbon (38%). The subsequent carbonate precipitation in the ocean will thus release more CO2 in the atmosphere-ocean system than that consumed by continental weathering, typically on glacial-interglacial time scales.

The geochemistry (major, trace element, O- and Sr-isotope ratios) and petrology of the Transhimalaya, North Himalaya, High Himalaya and ‘Lesser Himalaya’ plutonic belts are compared based on the analyses of up to 492 samples. The composite Transhimalaya batholith is subalkaline or monzonitic in character rather than calc-alkaline. Its genesis was probably closely related to subduction processes associated with strike-slip movement. It was emplaced on both sides of the boundary between an earlier metavolcanic arc and a continental margin. Two principal periods of magmatic activity occurred: Upper Cretaceous and, particularly in this region, Eocene at the time of the India-Eurasia collision when sediments may have become involved in the subduction process. Magmatic differentiation, characterized by two superimposed stages of evolution, and hybridization processes, involving both basic and acidic magmas, can account for the genesis of the different plutonic units. Although a continental contribution is implied, the isotopic data (6.8 < σ18O < 9·2; 0·704 < 87Sr/86Sr, < 0·707) preclude a significant contribution from either old crust or surface derived sediments. The North, High and ‘Lesser’ Himalaya plutonic belts are fundamentally different and correspond to aluminous associations of two groups of ages (Lower Palaeozoic for the ‘Lesser Himalaya’ and part of the North Himalaya; Upper Cenozoic for the High Himalaya and part of the North Himalaya). They are all high-σ18O (9 < σ18O < 14) granites and adamellites with high initial 87Sr/86Sr, ratios (0·709 to < 0·740). The Lower Palaeozoic group was generated within the Gondwana continental crust, independent of any true orogenesis, with a probable but limited contribution from the mantle. High Himalaya and North Himalaya Cenozoic plutons are directly linked to the activity of the Main Central Thrust. They were derived by similar anatectic processes of the same continental source rocks. The small but distinct chemical and mineralogical differences among the plutons are related to the increase in the intensity of anatexis on going towards the north and the east.

Abstract The swelling of some well-defined Mg-, Ca-, Sr- and Ba- homoionic montmorillonites was studied in the domain of water relative pressures lower than 0.95. This involves the expansion of the crystal lattice itself, commonly known as the “interlamellar expansion” or “inner crystalline swelling”. The initial freeze-dried clays were characterized by nitrogen adsorption-desorption volumetry and controlled transformation rate thermal analysis. The evolution of the structural and textural properties of these different clays at different stages of hydration and dehydration was investigated using water adsorption gravimetry, immersion microcalorimetry at different precoverage water vapor relative pressures and X-raydiffraction (XRD) under controlled humidity conditions. Large textural variations are observed in the dry state depending on the exchangeable cations. The 2-layer hydrate exhibits the most ordered layer stacking. Water is mainly adsorbed in the interlamellar space. With increasing water pressure, each homoionic species leads to a 1-layer hydrate and, with the exception of Ba-montmorillonite, to a predominant 2-layer hydrate. The relative pressure corresponding to the formation of the 2-layer hydrate decreases with increasing hydration energy of the interlayer cation. For Ca-, Sr- or Mg-montmoriHonites, simulation of XRD patterns leads to the definition of successive homogeneous states corresponding to the 2-layer hydrate. Furthermore, it yields the water filling ratio corresponding to the different hydration states during adsorption and desorption of water vapor.

[1] The present-day topography of the Tian Shan range is considered to result from crustal shortening related to the ongoing India-Asia collision that started in the early Tertiary. In this study we report evidence for several episodes of localized tectonic activity which occurred prior to that major orogenic event. Apatite fission track analysis and (U-Th)/He dating on apatite and zircon indicate that inherited Paleozoic structures were reactivated in the late Paleozoic-early Mesozoic during a Cimmerian orogenic episode and also in the Late Cretaceous-Paleogene (around 65–60 Ma). These reactivations could have resulted from the accretion of the Kohistan-Dras arc or lithospheric extension in the Siberia-Mongolia zone. Activity resumed in the late Mesozoic prior to the major Tertiary orogenic phase. Finally, the ongoing deformation, which again reactivates inherited tectonic structures, tends to propagate inside the endoreic basins that were preserved in the range, leading to their progressive closure. This study demonstrates the importance of inherited structures in localizing the first increments of the deformation before it propagates into yet undeformed areas.

Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples. The samples are mainly composed of materials similar to those of carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37° ± 10°C, about [Formula: see text] million (statistical) or [Formula: see text] million (systematic) years after the formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles that of the Sun's photosphere than other natural samples do.

Tracing the source of heavy metals in the environment is of key importance for our understanding of their pollution and natural cycles in the surface Earth reservoirs. Up to now, most exclusively Pb isotopes were used to effectively trace metal pollution sources in the environment. Here we report systematic variations of Cd isotope ratios measured in polluted topsoils surrounding a Pb-Zn refinery plant in northern France. Fractionated Cd was measured in soil samples surrounding the refinery, and this fractionation can be attributed to the refining processes. Despite the Cd isotopic ratios being precisely measured, the obtained uncertainties are still large compared to the total isotopic variation. Nevertheless, for the first time, Cd isotopically fractionated by industrial processes may be traced in the environment. On the same samples, Pb isotope systematics suggested that materials actually used by the refinery were not the major source of Pb in soils, probably because refined ore origins changed over the 100 years of operation. On the other hand, Cd isotopes and concentrations measured in topsoils allowed identification of three main origins (industrial dust and slag and agriculture), assuming that all Cd ores are not fractionated, as suggested by terrestrial rocks so far analyzed, and calculation of their relative contributions for each sampling point. Understanding that this refinery context was an ideal situation for such a study, our results lead to the possibility of tracing sources of anthropogenic Cd and better constrain mixing processes, fluxes, transport, and phasing out of industrial input in nature.