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Birger Schmitz - One of the best experts on this subject based on the ideXlab platform.

  • distribution of Chrome Spinel grains across the 3 he anomaly of the tortonian stage at the monte dei corvi section italy
    Special Paper of the Geological Society of America; 542 pp 383-391 (2019), 2019
    Co-Authors: Samuele Boschi, Birger Schmitz, Alessandro Montanari
    Abstract:

    The present-day ocean-climate system configuration took shape during the Miocene Epoch. Toward the end of the epoch, in the late Tortonian at ca. 8.5 Ma, there was an exceptional event: collisional disruption of an >150-km-diameter asteroid, which created the Veritas family of asteroids in the asteroid belt. This event increased the flux of interplanetary dust particles rich in 3He to Earth and probably caused a period of increased dust in the atmosphere, with consequent alteration of global and local environmental conditions. A late Miocene 3He anomaly likely related to the Veritas event has been registered in deep-sea sediments from Ocean Drilling Program (ODP) Site 926 (Atlantic Ocean), ODP Site 757 (Indian Ocean), and in the late Tortonian–early Messinian Monte dei Corvi section near Ancona, Italy. Here, we report the results of a study in the Monte dei Corvi section aimed to recover extraterrestrial Chrome-Spinel grains across the 3He anomaly interval, as has been done for the similar late Eocene 3He anomaly in the nearby Massignano section. In this study, three ~100 kg samples were collected from the Monte dei Corvi section: two within the 3He peak interval and one outside the anomaly interval as a background reference sample. In total, 1151 Chrome-Spinel grains (>63 µm) were recovered, but based on chemical composition, none of the grains has a clear extraterrestrial origin. This supports the inference that the 3He anomaly is indeed related to the Veritas event and not to an approximately coeval breakup of a smaller H-chondritic body in the asteroid belt, an event registered in meteoritic cosmic-ray exposure ages. Spectral studies of the Veritas asteroids indicate that they are made up of carbonaceous chondritic material. Such meteorites generally have very low Chrome-Spinel concentrations in the grain-size range considered here, contrary to the very chromite-rich ordinary chondrites. The terrestrial grains recovered were classified, and their composition showed that all the grains have an ophiolitic origin with no substantial compositional and distributional change through the section. The source area of the terrestrial grains was probably the Dinarides orogen.

  • shock history of the fossil ungrouped achondrite osterplana 065 raman spectroscopy and tem of relict Chrome Spinel grains
    Meteoritics & Planetary Science, 2018
    Co-Authors: S. S. Rout, Philipp R. Heck, Birger Schmitz
    Abstract:

    Chrome-Spinel grains from the fossil ungrouped achondrite Osterplana 065 (Ost 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied Chrome-Spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host Chrome-Spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two Chrome-Spinel grains from Ost 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Ost 065 Chrome-Spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Ost 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Ost 065 is a piece of the impactor that led to the L chondrite parent body breakup. (Less)

  • Shock history of the fossil ungrouped achondrite Österplana 065: Raman spectroscopy and TEM of relict Chrome‐Spinel grains
    Meteoritics & Planetary Science, 2018
    Co-Authors: S. S. Rout, Philipp R. Heck, Birger Schmitz
    Abstract:

    Chrome-Spinel grains from the fossil ungrouped achondrite Osterplana 065 (Ost 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied Chrome-Spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host Chrome-Spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two Chrome-Spinel grains from Ost 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Ost 065 Chrome-Spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Ost 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Ost 065 is a piece of the impactor that led to the L chondrite parent body breakup. (Less)

S. S. Rout - One of the best experts on this subject based on the ideXlab platform.

  • shock history of the fossil ungrouped achondrite osterplana 065 raman spectroscopy and tem of relict Chrome Spinel grains
    Meteoritics & Planetary Science, 2018
    Co-Authors: S. S. Rout, Philipp R. Heck, Birger Schmitz
    Abstract:

    Chrome-Spinel grains from the fossil ungrouped achondrite Osterplana 065 (Ost 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied Chrome-Spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host Chrome-Spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two Chrome-Spinel grains from Ost 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Ost 065 Chrome-Spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Ost 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Ost 065 is a piece of the impactor that led to the L chondrite parent body breakup. (Less)

  • Shock history of the fossil ungrouped achondrite Österplana 065: Raman spectroscopy and TEM of relict Chrome‐Spinel grains
    Meteoritics & Planetary Science, 2018
    Co-Authors: S. S. Rout, Philipp R. Heck, Birger Schmitz
    Abstract:

    Chrome-Spinel grains from the fossil ungrouped achondrite Osterplana 065 (Ost 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied Chrome-Spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host Chrome-Spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two Chrome-Spinel grains from Ost 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Ost 065 Chrome-Spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Ost 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Ost 065 is a piece of the impactor that led to the L chondrite parent body breakup. (Less)

Schmitz Birger - One of the best experts on this subject based on the ideXlab platform.

  • The terrestrial Cr-Spinels in the Maiolica Limestone: Where are they from?
    2019
    Co-Authors: Lenaz Davide, Schmitz Birger, Alvarez Walter
    Abstract:

    A total of 33 and 65 Chrome-Spinel grains in the >63 and 32-63 \u3bcm fractions have been recovered from 12 beds in two stratigraphically separated groups along the 240-m-thick Monte Acuto section of the Maiolica limestone in central Italy, spanning from Berriasian to the early Hauterivian. The chemistry of these detrital Spinels suggests they may represent windblown ophiolitic detritus showing the evolution of an ophiolite evolving from a MORB setting (Bosso section) to a SSZ setting including a Back Arc and an Arc setting (Monte Acuto section). The possible source of the Maiolica detrital minerals can be located in the obducting ophiolites of the Albanides and/or the Hellenides that showed a similar evolution. In this case it is particularly important to notice how the Chrome-Spinel detritus in the Maiolica limestone records this evolution in a relatively short period of time that lasted about 10 Ma

  • Distribution of Chrome-Spinel grains across the 3He anomaly of the Tortonian Stage at the Monte dei Corvi section, Italy
    'Geological Society of America', 2019
    Co-Authors: Boschi Samuele, Schmitz Birger, Montanari Alessandro
    Abstract:

    The present-day ocean-climate system configuration took shape during the Miocene Epoch. Toward the end of the epoch, in the late Tortonian at ca. 8.5 Ma, there was an exceptional event: collisional disruption of an >150-km-diameter asteroid, which created the Veritas family of asteroids in the asteroid belt. This event increased the flux of interplanetary dust particles rich in 3He to Earth and probably caused a period of increased dust in the atmosphere, with consequent alteration of global and local environmental conditions. A late Miocene 3He anomaly likely related to the Veritas event has been registered in deep-sea sediments from Ocean Drilling Program (ODP) Site 926 (Atlantic Ocean), ODP Site 757 (Indian Ocean), and in the late Tortonian–early Messinian Monte dei Corvi section near Ancona, Italy. Here, we report the results of a study in the Monte dei Corvi section aimed to recover extraterrestrial Chrome-Spinel grains across the 3He anomaly interval, as has been done for the similar late Eocene 3He anomaly in the nearby Massignano section. In this study, three ~100 kg samples were collected from the Monte dei Corvi section: two within the 3He peak interval and one outside the anomaly interval as a background reference sample. In total, 1151 Chrome-Spinel grains (>63 µm) were recovered, but based on chemical composition, none of the grains has a clear extraterrestrial origin. This supports the inference that the 3He anomaly is indeed related to the Veritas event and not to an approximately coeval breakup of a smaller H-chondritic body in the asteroid belt, an event registered in meteoritic cosmic-ray exposure ages. Spectral studies of the Veritas asteroids indicate that they are made up of carbonaceous chondritic material. Such meteorites generally have very low Chrome-Spinel concentrations in the grain-size range considered here, contrary to the very chromite-rich ordinary chondrites. The terrestrial grains recovered were classified, and their composition showed that all the grains have an ophiolitic origin with no substantial compositional and distributional change through the section. The source area of the terrestrial grains was probably the Dinarides orogen

  • Terrestrial Cr-Spinels in the Maiolica limestone : Where are they from?
    'Geological Society of America', 2019
    Co-Authors: Lenaz Davide, Schmitz Birger, Alvarez Walter
    Abstract:

    In total, 33 and 65 Chrome-Spinel (Cr-Spinel) grains in the >63 and 32–63 µm size fractions, respectively, were recovered from 12 beds in two stratigraphically separated groups along the 240-m-thick Monte Acuto section of the Maiolica limestone in central Italy, spanning from the Berriasian to the early Hauterivian. The chemistry of these detrital Spinels suggests they may represent windblown ophiolitic detritus, showing the evolution of an ophiolite evolving from a mid-ocean-ridge basalt setting (Bosso section) to a suprasubduction-zone setting, including a backarc and an arc setting (Monte Acuto section). The source of the Maiolica detrital minerals may have been the obducting ophiolites of the Albanides and/or the Hellenides, which show a similar evolution. In this case, it is particularly important to note how the Cr-Spinel detritus in the Maiolica limestone records this evolution over a relatively short period of time, lasting ~10 m.y

  • Shock history of the fossil ungrouped achondrite Österplana 065 : Raman spectroscopy and TEM of relict Chrome-Spinel grains
    'Wiley', 2018
    Co-Authors: Rout, Surya S., Heck, Philipp R., Schmitz Birger
    Abstract:

    Chrome-Spinel grains from the fossil ungrouped achondrite Österplana 065 (Öst 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied Chrome-Spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host Chrome-Spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two Chrome-Spinel grains from Öst 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Öst 065 Chrome-Spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Öst 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Öst 065 is a piece of the impactor that led to the L chondrite parent body breakup

Philipp R. Heck - One of the best experts on this subject based on the ideXlab platform.

  • shock history of the fossil ungrouped achondrite osterplana 065 raman spectroscopy and tem of relict Chrome Spinel grains
    Meteoritics & Planetary Science, 2018
    Co-Authors: S. S. Rout, Philipp R. Heck, Birger Schmitz
    Abstract:

    Chrome-Spinel grains from the fossil ungrouped achondrite Osterplana 065 (Ost 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied Chrome-Spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host Chrome-Spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two Chrome-Spinel grains from Ost 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Ost 065 Chrome-Spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Ost 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Ost 065 is a piece of the impactor that led to the L chondrite parent body breakup. (Less)

  • Shock history of the fossil ungrouped achondrite Österplana 065: Raman spectroscopy and TEM of relict Chrome‐Spinel grains
    Meteoritics & Planetary Science, 2018
    Co-Authors: S. S. Rout, Philipp R. Heck, Birger Schmitz
    Abstract:

    Chrome-Spinel grains from the fossil ungrouped achondrite Osterplana 065 (Ost 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied Chrome-Spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host Chrome-Spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two Chrome-Spinel grains from Ost 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Ost 065 Chrome-Spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Ost 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Ost 065 is a piece of the impactor that led to the L chondrite parent body breakup. (Less)

Sarah A. S. Dare - One of the best experts on this subject based on the ideXlab platform.

  • tectonic discrimination of peridotites using fo2 cr and ga ti feiii systematics in Chrome Spinel
    Chemical Geology, 2009
    Co-Authors: Sarah A. S. Dare, Julian A. Pearce, Iain Mcdonald, M T Styles
    Abstract:

    The accessory mineral Chrome–Spinel, [(Mg,Fe) (Cr,Al,Fe)2O4], is well-established as a useful, alteration-resistant petrogenetic and tectonic setting indicator for mafic–ultramafic rocks. This study of unaltered Spinels from 58 peridotites from oceanic and ophiolitic settings further develops the tectonic discrimination of peridotites from mid-ocean ridges (MOR) and supra-subduction zone (SSZ) settings. The geochemical data include the standard suite of elements, together with accurate ferric iron obtained by correcting electron microprobe data with Mossbauer Spinel standards, and gallium (Ga) obtained by Laser Ablation-ICP-MS. The results show that discrimination using the established oxygen fugacity (fO2)–Cr# [Cr/(Cr + Al)] diagram remains effective, but does depend on melt–rock reaction and magmatic differentiation of the reacting melt, in addition to tectonic setting. In particular, the MOR–SSZ boundary for dunites is displaced to higher oxygen fugacities than that for residual harzburgites, with some partially reacted harzburgites proving hard to fingerprint. Ga–Ti–Fe3# [Fe3/(Fe3 + Cr + Al)] systematics provide a potential way to improve the discrimination. Significantly, Ga and Fe3+ have similar ionic radii but only Fe3+ is redox-dependent, so Ga/Fe3# is largely independent of magmatic differentiation while retaining the capability to separate MOR peridotites from the higher Fe3# SSZ peridotites. Whereas Ga/Fe3# ratios decrease during melt–rock reaction, Ti/Fe3# ratios stay constant or increase according to the relative compositions of the mantle lithosphere and the interacting melt. In consequence, the Ti/Fe3# vs. Ga/Fe3# diagram requires only a single boundary to separate MOR harzburgites and dunites (with high ratios) from SSZ harzburgites and dunites (with low ratios). Podiform chromitites can only be fingerprinted if they share a similar history of olivine–Spinel subsolidus re-equilibration as the peridotites. Unlike the oxygen fugacity plot, the Ti/Fe3# vs. Ga/Fe3# diagram can also fingerprint peridotites that have no co-existing olivine or host rock information, such as serpentinites and detrital Spinels. Testing these methods using Spinels in mantle peridotites from the northern Oman–U.A.E. ophiolite confirms independent indicators that the ophiolite records the switch in tectonic setting from MOR to SSZ and hence magma genesis during the initiation of subduction.

  • Tectonic discrimination of peridotites using fO2–Cr# and Ga–Ti–FeIII systematics in Chrome–Spinel
    Chemical Geology, 2008
    Co-Authors: Sarah A. S. Dare, Julian A. Pearce, Iain Mcdonald, Michael Styles
    Abstract:

    The accessory mineral Chrome–Spinel, [(Mg,Fe) (Cr,Al,Fe)2O4], is well-established as a useful, alteration-resistant petrogenetic and tectonic setting indicator for mafic–ultramafic rocks. This study of unaltered Spinels from 58 peridotites from oceanic and ophiolitic settings further develops the tectonic discrimination of peridotites from mid-ocean ridges (MOR) and supra-subduction zone (SSZ) settings. The geochemical data include the standard suite of elements, together with accurate ferric iron obtained by correcting electron microprobe data with Mossbauer Spinel standards, and gallium (Ga) obtained by Laser Ablation-ICP-MS. The results show that discrimination using the established oxygen fugacity (fO2)–Cr# [Cr/(Cr + Al)] diagram remains effective, but does depend on melt–rock reaction and magmatic differentiation of the reacting melt, in addition to tectonic setting. In particular, the MOR–SSZ boundary for dunites is displaced to higher oxygen fugacities than that for residual harzburgites, with some partially reacted harzburgites proving hard to fingerprint. Ga–Ti–Fe3# [Fe3/(Fe3 + Cr + Al)] systematics provide a potential way to improve the discrimination. Significantly, Ga and Fe3+ have similar ionic radii but only Fe3+ is redox-dependent, so Ga/Fe3# is largely independent of magmatic differentiation while retaining the capability to separate MOR peridotites from the higher Fe3# SSZ peridotites. Whereas Ga/Fe3# ratios decrease during melt–rock reaction, Ti/Fe3# ratios stay constant or increase according to the relative compositions of the mantle lithosphere and the interacting melt. In consequence, the Ti/Fe3# vs. Ga/Fe3# diagram requires only a single boundary to separate MOR harzburgites and dunites (with high ratios) from SSZ harzburgites and dunites (with low ratios). Podiform chromitites can only be fingerprinted if they share a similar history of olivine–Spinel subsolidus re-equilibration as the peridotites. Unlike the oxygen fugacity plot, the Ti/Fe3# vs. Ga/Fe3# diagram can also fingerprint peridotites that have no co-existing olivine or host rock information, such as serpentinites and detrital Spinels. Testing these methods using Spinels in mantle peridotites from the northern Oman–U.A.E. ophiolite confirms independent indicators that the ophiolite records the switch in tectonic setting from MOR to SSZ and hence magma genesis during the initiation of subduction.

  • Chrome-Spinel geochemistry of the northern Oman-United Arab Emirates ophiolite
    2007
    Co-Authors: Sarah A. S. Dare
    Abstract:

    The Oman ophiolite is the largest and best preserved ophiolite in the world and records a switch from mid-ocean ridge (MOR) to supra-subduction zone (SSZ) setting. This study investigates the geochemical variability of Chrome-Spinel in the mantle sequence of the poorly known United Arab Emirates (U.A.E.) part of the northern Oman-U.A.E. ophiolite. Extensive field work was carried out and 260 samples collected for petrogenetic studies and geochemical mapping of the U.A.E. mantle. Chrome-Spinel geochemistry provides valuable information on bom the residual mantle and on the nature and extent of melt-rock reaction. In particular, it is used to fingerprint the compositions of the magmas that interacted with the mantle lithosphere. This study also develops a new method to analyse gallium in Chrome-Spinel by Laser Ablation-ICP-MS, and successfully uses it to improve the tectonic discrimination of Chrome-Spinel. The results show that the U.A.E. mantle lithosphere formed at a MOR-type setting and was modified by melt-rock reaction with MORB-type and SSZ-type melts. This history of melt infiltration strongly resembles the magmatic history of the crustal sequence in each of the Aswad and Khawr Fakkan Blocks. Geochemical mapping illustrates a strong spatial control on the pattern of melt infiltration in the mantle and constrains the proximity of each mantle domain with respect to the subduction zone. The Khawr Fakkan mantle extensively interacted with boninitic melts during subduction initiation. Thus, it was closer to the subduction zone than the Aswad mantle which predominantly interacted with island-arc tholeiite melts. Importantly, this work demonstrates for the first time that the Dibba Zone peridotites originate from pre-existing 'true' MOR mantle lithosphere between the trench and the main body of the ophiolite. A further important conclusion is that the mantle lithosphere of the northern Oman-U.A.E. ophiolite was not the source region for the SSZ magmatism. Previous workers proposed that the plane of detachment and the subduction zone were the same, which implies that the mantle of the ophiolite was the source of the SSZ magmatism. Instead, this study proposes that detachment of the ophiolite took place at a shallower level than the plane of the subduction zone and thus provides strong evidence for a subduction zone at a still deeper level. During detachment, the ophiolite incorporated slices of ultramafic rock near the trench (i.e. the Dibba Zone peridotites) as it bulldozed its way over the underlying plate and onto the continental margin of Arabia.