1,721,015 research outputs found
Chondritic ingredients: I. Usual suspects and some oddballs in the Leoville CV3 meteorite
No full textReduced CV3 chondrites are relatively pristine rocks and prime candidates for studies exploring processes that predated planet formation. We closely examined the petrographic features and trace elemental composition of different CV3 constituents in the accretionary breccia Leoville. The petrographic results are presented here. Our sample (2.2 cm2) is not brecciated. The main ingredientabout 65 area%is fine- to coarse-grained ferromagnesian type I chondrules. Minor constituents (in order of 2-D abundance) include refractory inclusions, Al-rich chondrules, and very fine-crystalline clasts of moderately volatile composition. Type II chondrules and metal nuggets occur sporadically. The chondrulematrix ratio is approximately 3:1. Medium- and coarse-grained chondrules exhibit porphyritic textures, probably caused by incomplete melting, and frequent, partial or continuous, recrystallized dust rims. The fine-grained population most likely represents randomly sectioned dust rims. The rim material and some of the medium-grained objects are relatively troilite-rich. Iron-nickel metal is rare. In addition, almost all constituents show strikingly ragged or convoluted outlines. Only a few, rim-less components exhibit smooth contours. Evidence for incomplete melting and the formation of recrystallized or igneous rims in carbonaceous chondrites is well established, suggesting that both processes were widespread events. The observed features in Leoville support this conclusion. In addition, our findings indicate that surface abrasion in a turbulent dust-filled regime may have taken place after the consolidation of dust rims. Alternatively, the irregular, convoluted nature of at least the rimmed chondrules may have been inherent to the dust accretion event and was not erased by subsequent heating.DFG (German Research Foundation) [PA1970/1-1, PA909/2-1, PA909/2-2
Chondritic ingredients: II. Reconstructing early solar system history via refractory lithophile trace elements in individual objects of the Leoville CV3 chondrite
No full textA single web-interface to access, visualise and model data from multiple geo- and cosmochemical databases
No full textExperimental investigation of the nebular formation of chondrule rims and the formation of chondrite parent bodies
No full textWe developed an experimental setup to test the hypothesis that accretionary rims around chondrules formed in the solar nebula by accretion of dust on the surfaces of hot chondrules. Our experimental method allows us to form dust rims around chondrule analogs while levitated in an inert-gas flow. We used micrometer-sized powdered San Carlos olivine to accrete individual dust particles onto the chondrule analogs at room temperature (20 degrees C) and at 1100 degrees C. The resulting dust rims were analyzed by means of two different techniques: non-destructivemicro computer tomography, and scanning electron microscopy. Both methods give very similar results for the dust rimstructure and a mean dust rim porosity of 60% for the hot coated samples, demonstrating that both methods are equally well suited for sample analysis. The chondrule analog's bulk composition has no measurable impact on the accretion efficiency of the dust. We measured the chemical composition of chondrule analog and dust rim to check whether elemental exchange between the two components occurred. Such a reaction zone was not found; thus, we can experimentally confirm the sharp border between chondrules and dust rims described in the literature. We adopted a simple model to derive the degree of post-accretionary compaction for different carbonaceous chondrites. Moreover, we measured the rim porosity of a fragment of Murchison meteorite, analyzed it with micro-CT and found rim porosities with this technique that are comparable to those described in the literature. (C) 2012 Elsevier Ltd. All rights reserved.Deutsche Forschungsgemeinschaft (DFG) [Bl 298/13-1, SPP 1385
Overcoming Fragmentation of Geochemical Data Resources: Collaboration between EarthChem, Astromat, GEOROC, and MetBase
No full textGlobal geochemical datasets are increasingly valuable for solving research questions in geochemistry, volcanology and beyond. To support new research, open sharing and access of geochemical data needs to be easy for researchers so they can take full advantage of the rapidly growing volume of data generated in laboratories across the globe, and to comply with the principles of Open Science. Instead, the fragmented landscape of geochemical data systems makes it difficult for researchers to find, access, and contribute their data: Geochemical data are curated and published in a range of thematic, institutional, and programmatic data systems that differ in architecture, metadata schemas, terminology, and data output formats. Researchers have to figure out where to obtain the data they need; learn to use different search applications; retrieve data from multiple databases and painstakingly reformat the datasets they obtained from different systems to integrate them. They need to select an appropriate repository for their data, and potentially work with different submission systems and templates. Collaboration among geochemical data systems is a critical step to overcome this fragmentation and facilitate geochemical data management and access for the research community by coordinating, aligning, and integrating their systems. Through collaboration, data repositories and databases can also leverage each other’s expertise and resources to operate their services more effectively and efficiently.
We here report about new collaborative efforts among four geochemical data systems that aim to harmonize and integrate their data holdings and software ecosystem for the benefit of the research community and to improve their sustainability: EarthChem (https://earthchem.org/), GEOROC (https://georoc.eu/), MetBase (https://metbase.org/), and the Astromaterials Data System (https://www.astromat.org/). Building on the long-term collaboration between EarthChem and GEOROC, this collaboration leverages the new development of the Astromaterials Data System with modern technology and two new projects funded to overhaul the infrastructure of the GEOROC and MetBase databases as an opportunity to jointly develop a more resilient, sustainable platform for data exchange. Results of the collaboration so far include: a) alignment of the Astronaut and MetBase data models b) migration of the MetBase data holdings into the Astromat synthesis database; c) alignment of the EarthChem and GEOROC data models; d) new automated synchronization process of GEOROC data to the ECP; e) harmonized vocabularies for chemical variables, analytical methods (Others are in development in alignment with emerging efforts of the OneGeochemstry initiative); f) design of the future shared architecture of EarthChem and GEOROC that includes plans for a joint data entry tool for curators and a single data submission platform for researchers to contribute their data to the affiliated domain repositories.
The ultimate goal of this harmonization between EarthChem, Astromat, GEOROC and MetBase is to make it easier for researchers to access and contribute data. We hope to integrate further systems in the future, building on ongoing collaborations with the Australian Geochemistry Network, the US Geological Survey, SAMIS (Sample Analysis Microinformation System), the GFZ Data Services, and the Sparrow software
- …
