Evolution of oxygen isotopic composition in the inner solar nebula

Changes in the chemical and isotopic composition of the solar nebula with time are reflected in the properties of different constituents that are preserved in chondritic meteorites. CR carbonaceous chondrites are among the most primitive of all chondrite types and must have preserved solar nebula records largely unchanged. We have analyzed the oxygen and magnesium isotopes in a range of the CR constituents of different formation temperatures and ages, including refractory inclusions and chondrules of various types. The results provide new constraints on the time variation of the oxygen isotopic composition of the inner (<5 AU) solar nebula - the region where refractory inclusions and chondrules most likely formed. A chronology based on the decay of short-lived 26Al (t1/2 ~ 0.73 Ma) indicates that the inner solar nebula gas was 16O-rich when refractory inclusions formed, but less than 0.8 Ma later, gas in the inner solar nebula became 16O-poor and this state persisted at least until CR chondrules formed ~1-2 Myr later. We suggest that the inner solar nebula became 16O-poor because meter-size icy bodies, which were enriched in 17,18O due to isotopic self-shielding during the ultraviolet photo dissociation of CO in the protosolar molecular cloud or protoplanetary disk, agglomerated outside the snowline, drifted rapidly towards the Sun, and evaporated at the snowline. This led to significant enrichment in 16O-depleted water, which then spread through the inner solar system. Astronomical studies of the spatial and/or temporal variations of water abundance in protoplanetary disks may clarify these processes.Comment: 27 pages, 5 figure

Discovery of a New Cl-Rich Silicate Mineral, Ca_(12)(Al_2Mg_3Si_7)O_(32)Cl_6: An Alteration Phase in Allende

During a nanomineralogy investigation of the Allende CV3 carbonaceous chondrite, a new silicate mineral, Ca_(12)(Al_4Mg_3Si_7)O_(32)Cl_6 with the I 4 3d wadalite structure, was identified in the Type B1 Ca-Al-rich inclusion (CAI) Egg-3. Field-emission SEM with EDS and electron back-scatter diffraction and electron microprobe were used to characterize its composition, structure, and associated phases. Synthetic Ca_(12)(Al_4Mg_3Si_7)O_(32)Cl_6 are not reported. The Allende Ca_(12)(Al_4Mg_3Si_7)O_(32)Cl_6 is the first natural occurrence of this phase. Here we discuss its origin and significance for understanding alteration processes on the CV chondrite parent asteroid. The mineral is currently under review by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2014-028). It is a new member of the wadalite group

Adrianite, Ca_(12)(Al_4Mg_3Si_7)O_(32)Cl_6, a new Cl-rich silicate mineral from the Allende meteorite: An alteration phase in a Ca-Al-rich inclusion

Adrianite (IMA 2014-028), Ca_(12)(Al_4Mg_3Si_7)O_(32)Cl_6, is a new Cl-rich silicate mineral and the Si,Mg analog of wadalite. It occurs with monticellite, grossular, wadalite, and hutcheonite in altered areas along some veins between primary melilite, spinel, and Ti,Al-diopside in a Type B1 FUN (Fractionation and Unidentified Nuclear effects) Ca-Al-rich inclusion (CAI), Egg-3, from the Allende CV3 carbonaceous chondrite. The mean chemical composition of type adrianite by electron probe microanalysis is (wt%) CaO 41.5, SiO_2 27.5, Al_2O_3 12.4, MgO 7.3, Na_2O 0.41, Cl 13.0, O=Cl –2.94, total 99.2, giving rise to an empirical formula of (Ca_(11.69)Na_(0.21))(Al_(3.85)Mg_(2.88)Si_(7.23))O_(32)Cl_(5.80). The end-member formula is Ca_(12)(Mg_5Si_9)O_(32)Cl_6. Adrianite has the I43d wadalite structure with a = 11.981 Å, V = 1719.8 Å^3, and Z = 2, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.03 g/cm^3. Adrianite is a new secondary mineral in Allende, apparently formed by alkali-halogen metasomatic alteration of primary CAI minerals such as melilite, anorthite, perovskite, and Ti,Al-diopside on the CV chondrite parent asteroid. Formation of secondary Cl-rich minerals sodalite, adrianite, and wadalite during metasomatic alteration of the Allende CAIs suggests that the metasomatic fluids had Cl-rich compositions. The mineral name is in honor of Adrian J. Brearley, mineralogist at the University of New Mexico, U.S.A., in recognition of his many contributions to the understanding of secondary mineralization in chondritic meteorites

Discovery of a New Garnet Mineral, Ca_3Ti_2(SiAl_2)O_(12): An Alteration Phase in Allende

During a nanomineralogy investigation of the Allende CV3 carbonaceous chondrite, a new Ti-rich silicate, Ca_3Ti_2(SiAl_2)O_(12) with the Ia-3d garnet structure, was identified in the Type B1 Ca,Al-rich inclusion (CAI) Egg-3. Field-emission SEM with EDS and electron back-scatter diffraction and electron microprobe were used to characterize the composition and structure. Synthetic Ca_3Ti_2(SiAl_2)O_(12) is not reported. We present here the natural occurrence of Ca_3Ti_2(SiAl_2)O_(12), as a new alteration silicate in a CAI, and discuss its origin and significance for secondary processes. The mineral is currently under review by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2013-029). It is a new member of the schorlomite group in the garnet supergroup

Adrianite, Ca_(12)(Al_4Mg_3Si_7)O_(32)Cl_6, a new Cl-rich silicate mineral from the Allende meteorite: An alteration phase in a Ca-Al-rich inclusion

Adrianite (IMA 2014-028), Ca_(12)(Al_4Mg_3Si_7)O_(32)Cl_6, is a new Cl-rich silicate mineral and the Si,Mg analog of wadalite. It occurs with monticellite, grossular, wadalite, and hutcheonite in altered areas along some veins between primary melilite, spinel, and Ti,Al-diopside in a Type B1 FUN (Fractionation and Unidentified Nuclear effects) Ca-Al-rich inclusion (CAI), Egg-3, from the Allende CV3 carbonaceous chondrite. The mean chemical composition of type adrianite by electron probe microanalysis is (wt%) CaO 41.5, SiO_2 27.5, Al_2O_3 12.4, MgO 7.3, Na_2O 0.41, Cl 13.0, O=Cl –2.94, total 99.2, giving rise to an empirical formula of (Ca_(11.69)Na_(0.21))(Al_(3.85)Mg_(2.88)Si_(7.23))O_(32)Cl_(5.80). The end-member formula is Ca_(12)(Mg_5Si_9)O_(32)Cl_6. Adrianite has the I43d wadalite structure with a = 11.981 Å, V = 1719.8 Å^3, and Z = 2, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.03 g/cm^3. Adrianite is a new secondary mineral in Allende, apparently formed by alkali-halogen metasomatic alteration of primary CAI minerals such as melilite, anorthite, perovskite, and Ti,Al-diopside on the CV chondrite parent asteroid. Formation of secondary Cl-rich minerals sodalite, adrianite, and wadalite during metasomatic alteration of the Allende CAIs suggests that the metasomatic fluids had Cl-rich compositions. The mineral name is in honor of Adrian J. Brearley, mineralogist at the University of New Mexico, U.S.A., in recognition of his many contributions to the understanding of secondary mineralization in chondritic meteorites

Discovery of new mineral addibischoffite, Ca_2Al_6Al_6O_(20) ,IN A Ca-Al-Rich refractory inclusion from the Acfer 214 CH3 meteorite

Introduction: During a mineralogy investigation of the Acfer 214 CH3 carbonaceous chondrite, a new calcium aluminate mineral, named “addibischoffite”, Ca_2Al_6Al_6O_(20) with the P-1 aenigmatite structure, was identified in a Ca-Al-rich inclusion (CAI). Field-emission scanning electron microscope, electron back-scatter diffraction, electron microprobe and ion microprobe were used to characterize its chemical and oxygen-isotope compositions, structure, and associated phases. Synthetic CaAl_6O_(10) was reported but not fully characterized [e.g., 1]. Presented here is its first natural occurrence as a new refractory mineral in a primitive meteorite. The mineral has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2015-006). The name is in honor of Addi Bischoff, a cosmochemist at Münster University, Germany, for his many contributions to research on CAIs in carbonaceous chondrites, including CH chondrites

Chromite-rich mafic silicate chondrules in ordinary chondrites: Formation by impact melting

Chromium-rich chondrules constitute less than 0.1 percent of all ordinary chondrite (OC) chondrules and comprise three groups: chromian-spinel chondrules, chromian-spinel inclusions, and chromite-rich mafic silicate (CRMS) chondrules. Chromian-spinel chondrules (typically 100-300 microns in apparent diameter) exhibit granular, porphyritic and unusual textures and occur mainly in H chondrites. Their morphologies are distinct from the irregularly shaped chromian-spinel inclusions of similar mineralogy. Chromian-spinel chondrules and inclusions consist of grains of chromian-spinel embedded in plagioclase (Pl) or mesostasis of Pl composition. Many also contain accessory ilmenite (Ilm), high-Ca pyroxene (Px), merrillite (Mer), and rare olivine (Ol); some exhibit concentric mineral and chemical zoning. CRMS chondrules (300-1100 microns in apparent diameter) are generally larger than chromian-spinel chondrules and occur in all metamorphosed OC groups. Most CRMS chondrules are nearly spherical although a few are ellipsoidal with a/b aspect ratios ranging up to 1.7. Textures include cryptocrystalline, granular, radial, barred, and porphyritic varieties; some contain apparently relict grains. The chondrules consist of chromite (Chr), Ol and Pl, along with accessory Mer, troilite (Tr), metallic Fe-Ni (Met), Px and Ilm. The mesostasis in CRMS chondrules is nearly opaque in transmitted light; thus, they can be easily recognized in the optical microscope. Based on the similarity of mineralogy and chemistry between CRMS chondrules of different textures (opaque chromite-rich mesostasis, skeletal morphology of Ol grains, similar bulk compositions) we suggest that these chondrules form a genetically related population

V. V. von Wal as Head of Vilnius Province in 1901—1902

The activities of one of the typical representatives of the Russian regional bureaucracy of the second half of the 19th — early 20th centuries — Viktor Vilhelmovich von Wal as governor of Vilnius province, which he held from 1901 to 1902 is examined in the article.  Particular attention is paid to the circumstances of his appointment to this position, which was due to attempts at administrative reorganization of the management of the northwestern outskirts of Russia. A brief analysis of the socio-political situation that had developed by the beginning of the 20th century in the Vilnius province is given and it is indicated that the most acute problem during this period was the active labor movement, which had a mixed socio-ethnic character in the region. It is concluded that the management model implemented by von Wahl, which was based on the traditional administrative-power dominant, did not correspond to the situation in the region and provoked an increase in the degree of violence in the province. It is noted that, despite the short-term tenure of von Waal as governor of Vilna, it had a number of important consequences, demonstrating the premature liquidation of the institution of the governor-general in the region and the need to soften the administrative policy towards the local population

Variations of Chemical Composition of Matrices among Carbonaceous Chondrites.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月17日（木） 国立国語研究所 2階講

Multiple formation mechanisms of ferrous olivine in CV carbonaceous chondrites during fluid-assisted metamorphism

The CV carbonaceous chondrites experienced alteration that resulted in formation of secondary ferrous olivine (Fa40-100), salite-hedenbergite pyroxenes (Fs10-50Wo45-50), wollastonite, andradite, nepheline, sodalite, phyllosilicates, magnetite, Fe,Ni-sulfides and Ni-rich metal in their Ca,Al-rich inclusions, amoeboid olivine ag-gregates, chondrules, and matrices. It has previously been suggested that fibrous ferrous olivine in dark inclusions in CV chondrites formed by dehydration of phyllosilicates during thermal metamorphism (T. Kojima and K. Tomeoka, Geochim. Cosmochim. Acta, 60, 2651, 1996; A.N. Krot et al., Meteoritics, 30, 748, 1995). This mechanism has been subsequently applied to explain the origin of ferrous olivine in the CV chondrules and matrices (A.N. Krot et al., Meteoritics, 32, 31, 1997). It is, however, inconsistent with the lack of significant fractionation of bulk oxygen isotope compositions of the CV chondrites and the Allende dark inclusions and the common occurrences of ferrous olivine in the aqueously-altered and virtually unmetamorphosed oxidized CV chondrites of the Bali-like subgroup. Based on the petrographic observations and the isotopic compositions of ferrous olivine and coexisting Ca,Fe-rich silicates in CV chondrites and their dark inclusions, we infer that ferrous olivine formed during a fluid-assisted metamorphism by several mechanisms: (i) replacement of Fe,Ni-metal±sulfide nodules, (ii) replacement of magnesian olivine and low-Ca pyroxene, and (iii) direct precipitation from an aqueous solution. Dehydration of phyllosilicates appear to have played only a minor (if any) role. Although our model does not address specifically the origin of ferrous olivine rims around forsterite grains in Allende, the observed homogenization of matrix olivines (which have comparable sizes to thicknesses of the ferrous olivine rims in Allende) from Kaba to Allende suggests that compositions of ferrous olivine rims in Allende cannot be primary and must have been modified by asteroidal alteration