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The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event widely observed in the U.S. Midwest and in Ontario, Canada. Several fragments fell onto frozen surfaces of lakes and, thanks to weather radar data, were recovered days after the fall. The studied rock fragments show no or little signs of terrestrial weathering. Here, we present the initial results from an international consortium study to describe the fall, characterize the meteorite, and probe the collision history of Hamburg. About 1 kg of recovered meteorites was initially reported. Petrology, mineral chemistry, trace element and organic chemistry, and O and Cr isotopic compositions are characteristic of H4 chondrites. Cosmic ray exposure ages based on cosmogenic 3He, 21Ne, and 38Ar are ~12 Ma, and roughly agree with each other. Noble gas data as well as the cosmogenic 10Be concentration point to a small 40-60 cm diameter meteoroid. An 40Ar-39Ar age of 4532 ± 24 Ma indicates no major impact event occurring later in its evolutionary history, consistent with data of other H4 chondrites. Microanalyses of phosphates with LA-ICPMS give an average Pb-Pb age of 4549 ± 36 Ma. This is in good agreement with the average SIMS Pb-Pb phosphate age of 4535.3 ± 9.5 Ma and U-Pb Concordia age of 4535 ± 10 Ma. The weighted average age of 4541.6 ± 9.5 Ma reflects the metamorphic phosphate crystallization age after parent body formation in the early solar system.

We have reconstructed the compositional evolution of the silicate and carbonate melt, and various crystalline phases in the subvolcanic reservoir of Kerimasi Volcano in the East African Rift. Trace element concentrations of silicate and carbonate melt inclusions trapped in nepheline, apatite and magnetite from plutonic afrikandite (clinopyroxene-nepheline-perovskite-magnetite-melilite rock) and calciocarbonatite (calcite-apatite-magnetite-perovskite-monticellite-phlogopite rock) show that liquid immiscibility occurred during the generation of carbonatite magmas from a CO.sub.2-rich melilite-nephelinite magma formed at relatively high temperatures (1,100 °C). This carbonatite magma is notably more calcic and less alkaline than that occurring at Oldoinyo Lengai. The CaO-rich (32-41 wt%) nature and alkali-'poor' (at least 7-10 wt% Na.sub.2O + K.sub.2O) nature of these high-temperature (>1,000 °C) carbonate melts result from strong partitioning of Ca (relative to Mg, Fe and Mn) in the immiscible carbonate and the CaO-rich nature (12-17 wt%) of its silicate parent (e.g., melilite-nephelinite). Evolution of the Kerimasi carbonate magma can result in the formation of natrocarbonatite melts with similar composition to those of Oldoinyo Lengai, but with pronounced depletion in REE and HFSE elements. We suggest that this compositional difference results from the different initial parental magmas, e.g., melilite-nephelinite at Kerimasi and a nephelinite at Oldoinyo Lengai. The difference in parental magma composition led to a significant difference in the fractionating mineral phase assemblage and the element partitioning systematics upon silicate-carbonate melt immiscibility. LA-ICP-MS analysis of coeval silicate and carbonate melt inclusions provides an opportunity to infer carbonate melt/silicate melt partition coefficients for a wide range of elements. These data show that Li, Na, Pb, Ca, Sr, Ba, B, all REE (except Sc), U, V, Nb, Ta, P, Mo, W and S are partitioned into the carbonate melt, whereas Mg, Mn, Fe, Co, Cu, Zn, Al, Sc, Ti, Hf and Zr are partitioned into the silicate melt. Potassium and Rb show no preferential partitioning. Kerimasi melt inclusions show that the immiscible calcic carbonate melt is strongly enriched in Sr, Ba, Pb, LREE, P, W, Mo and S relative to other trace elements. Comparison of our data with experimental results indicates that preferential partitioning of oxidized sulfur (as SO.sub.4.sup.2-), Ca and P (as PO.sub.4.sup.3-) into the carbonate melt may promote the partitioning of Nb, Ta, Pb and all REE, excluding Sc, into this phase. Therefore, it is suggested that P and S enrichment in calcic carbonate magmas promotes the genesis of REE-rich carbonatites by liquid immiscibility. Our study shows that changes in the partition coefficients of elements between minerals and the coexisting melts along the liquid line of descent are rather significant at Kerimasi. This is why, in addition to the REE, Nb, Ta and Zr are also enriched in Kerimasi calciocarbonatites. We consider significant amounts of apatite and perovskite precipitated from melilite-nephelinite-derived carbonate melt as igneous minerals can have high LREE, Nb and Zr contents relative to other carbonatite minerals. Electronic supplementary material The online version of this article (doi:10.1007/s00410-014-1093-4) contains supplementary material, which is available to authorized users., Author(s): Tibor Guzmics[sup.1] , Zoltan Zajacz[sup.2] , Roger H. Mitchell[sup.3] , Csaba Szabo[sup.1] , Markus Wälle[sup.2] Author Affiliations: (1) Lithosphere Fluid Research Laboratory, Department of Petrology and Geochemistry, Eotvos University [...]

Byline: Zoltan Zajacz (1), Werner Halter (1), Wim J. Malfait (1), Olivier Bachmann (2), Robert J. Bodnar (3), Marc M. Hirschmann (4), Charles W. Mandeville (5), Yann Morizet (1,6), Othmar Muntener (7), Peter Ulmer (8), James D. Webster (5) Abstract: A new approach was developed to measure the water content of silicate glasses using Raman spectroscopy, which is independent of the glass matrix composition and structure. Contrary to previous studies, the compositional range of our studied silicate glasses was not restricted to rhyolites, but included andesitic, basaltic and phonolitic glasses. We used 21 glasses with known water contents for calibration. To reduce the uncertainties caused by the baseline removal and correct for the influence of the glass composition on the spectra, we developed the following strategy: (1) application of a frequency-dependent intensity correction of the Raman spectra (2) normalization of the water peak using the broad T--O and T--O--T vibration band at 850--1250 cm.sup.-1 wavenumbers (instead of the low wavenumber T--O--T broad band, which appeared to be highly sensitive to the FeO content and the degree of polymerization of the melt) (3) normalization of the integrated Si-O band area by the total number of tetrahedral cations and the position of the band maximum. The calibration line shows a +-0.4 wt% uncertainty at one relative standard deviation in the range of 0.8--9.5 wt% water and a wide range of natural melt compositions. This method provides a simple, quick, broadly available and cost-effective way for a quantitative determination of the water content of silicate glasses. Application to silicate melt inclusions yielded data in good agreement with SIMS data. Author Affiliation: (1) Department of Earth Sciences, Isotope Geochemistry and Mineral Resources, ETH Zurich, 8092, Zurich, Switzerland (2) Section des Sciences de la Terre, Universite de Geneve, Departement de Mineralogie 13, rue des MaraA!chers, 1211, GENEVE 4, Switzerland (3) Department of Geosciences, 4044 Derring Hall, Virginia Tech, Blacksburg, VA, 24061-0420, USA (4) Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN, 55455, USA (5) Department of Earth and Planetary Sciences, A.M.N.H., Central Park West at 79th Street, New York, NY, 10024-5192, USA (6) Now at: Laboratory of Planetology and Geodynamic, University of Nantes, 2 rue de la Houssiniere, 44300, Nantes, France (7) Institute of Geological Sciences, University of Bern, Baltzerstr. 1, 3012, Bern, Switzerland (8) Department of Earth Sciences, Institute for Mineralogy and Petrology, ETH Zurich, 8092, Zurich, Switzerland Article History: Registration Date: 30/09/2005 Received Date: 16/05/2005 Accepted Date: 01/09/2005 Online Date: 08/11/2005 Article note: Communicated by T.L. Grove