Shock melting origin of a troilite-rich clast in the Moorabiechondrite (L3)

A troilite-rich clast enclosing chondrules was found in the Moorabie chondrite (L3). This chondrite is characterized by elongate morphology of chondrules produced by shock deformation. Average composition of the metal and troilite grains in the clast is close to the eutectic composition of the Fe-S system, indicating the melting origin of the clast. The eutectic composition provides the heating temperature to be around 1000℃. Size and distribution of troilite and metal grains in the clast suggest the slow cooling after the melting. Pentlandite as an exsolved phase of troilite in the clast, found first in ordinary chondrites, also supports the melting and slow cooling. Thermal history of the clast indicates that the melting of the opaque minerals and the elongate morphology of chondrules were caused inside the parent body by the shock event which occurred at an early hot stage (around 400℃) of the cooling after the accretion of the chondrite

Sulfidation of metallic iron in the primordial solar nebura

The phase diagram of the Fe-S-H system was constructed based on thermochemical calculations at low total pressure (p(total)=p(H_2)=10^ and 10^ atm). Under these conditions both metallic iron and troilite, and troilite and pyrite are in reaction relation over a wide range of the phase diagram. The most important characteristic of the phase diagram is that the peritectic line is highly proximate to the H-S tie line. Based on the reaction relation the rate of the reaction in the solar gas was studied by applying the experimental data of the FeS formation reaction in the field of corrosion science of metals. The rate is controlled by diffusion in a FeS layer and the parabolic rate constant, k, is approximately given by k (cm^2/s)=0.3 exp (-3.5×10^4(cal/mol)/RT) in the solar nebula condition. The reaction degree was estimated based on various conditions of the cooling solar nebula : (1) contant p (S_2), (2) decreasing p (S_2) and (3) a certain saturation temperature above 0K, when the grain size of metallic iron was controlled by homogeneous nucleation theory

A cooling rate constraint on microtextural development of plagioclase and scapolite: an example from the Lutzow-Holm Complex, East Antarctica

Exsolution lamellae in albite-rich plagioclase and antiphase domains in scapolite from the Lutzow-Holm Complex of East Antarctica were found under a transmission electron microscope.These micro-textures were found in the first cooling period of the three period cooling model proposed from the geochronological data. Based on these micro-textures,the cooling rate of the complex was estimated to be in a range from several to thousands K/my. These rates are concordant with those estimated from the ages of the complex

Relict minerals and their assemblages in Yamato-691 (EH3)

Four relict minerals; olivine, pyroxene, a silica mineral and metallic (Fe, Ni) were found in the chondrules and as the mineral fragments of Yamato-691 (EH3). Two mineral assemblages of the relict minerals were found; (a) olivine+pyroxene+metallic (Fe, Ni), and (b) pyroxene+silica mineral. The relict pyroxene in assemblage (a) was formed from the reaction of olivine and silica-rich phase (gas or liquid). These two assemblages cannot coexist under an equilibrium condition. The compositional difference of pyroxene between assemblages (a) and (b) suggests the fractionation which occurred before the chondrule formation

Refractory precursor components in an Allende ferromagnesian chondrule

Chemical and petrological studies of chondrules revealed that they were formed through melting of pre-existing solid precursor materials, and that one of the refractory lithophile precursors was a high temperature condensate from the nebular gas and related to Ca, Al-rich inclusions (CAIs). Sheng et al. found relict spinel grains with isotopically fractionated Mg in plagioclase-olivine inclusions from CV chondrites and suggested that the major fractionation processes were common to CAIs and chondrules. We have determined the Mg isotopic compositon of five barred olivine chondrules and one coarse-grained rim from the Allende (CV3) meteorite. A reproducibility of instrumental isotope fractionation is plus or minus 2 per thousand per amu. The precision of the Mg-26/Mg-24 data after normalization for mass fractionation can be as good as 0.5 per thousand (2 sigma(mean)). The Mg analytical results are given and indicate that delta Mg-25/Mg-24 and sigma Mg-26 of the chondrules are normal within errors

Studies on the Native Plants in the Coastal Sand Dune (IV) Influences of Wind Velocity on Leaf Temperature of Wedelia prostrata Hemsl

The relationship between the leaf temperature of Wedelia prostrata Hemsl and wind velocity was investigated by comparing the shoot and stolon stem. The stolon stem leaf temperature，r gardless of wind velocity，was 6-7℃ lower than the air temperature in the day time. On the other hand，the shoot stem leaf temperature on a low wind day was higher，and on a high wind day was lower，than the air temperature. The difference between the leaf and air temperature was 1-2℃. The relationship between the air (x) and leaf (y) temperature is as follows. Low wind day stolon stem y=0.628x+9.01, r=0.936*** shoot stem y=1.198x-5.28，r=0.985*** High wind day stolon stem y=0.610x+9.65，r=0.963*** shoot stem y=0.667x+8.55，r=0.905**

High abundance ratio of 13^{13}CO to C18^{18}O toward photon-dominated regions in the Orion-A giant molecular cloud

Aims. We derive physical properties such as the optical depths and the column densities of $^{13}$CO and C$^{18}$O to investigate the relationship between the far ultraviolet (FUV) radiation and the abundance ratios between $^{13}$CO and C$^{18}$O. Method. We have carried out wide-field (0.4 deg$^2$) observations with an angular resolution of 25.8 arcsec ($\sim$ 0.05 pc) in $^{13}$CO ($J$=1--0) and C$^{18}$O ($J$=1--0) toward the Orion-A giant molecular cloud using the Nobeyama 45 m telescope in the on-the-fly mode. Results. Overall distributions and velocity structures of the $^{13}$CO and C$^{18}$O emissions are similar to those of the $^{12}$CO ($J$=1--0) emission. The optical depths of the $^{13}$CO and C18O emission lines are estimated to be 0.05 $<$ $\tau_{\rm ^{13}CO}$ $<$ 1.54 and 0.01 $<$ $\tau_{\rm C^{18}O}$ $<$ 0.18, respectively. The column densities of the $^{13}$CO and C$^{18}$O emission lines are estimated to be 0.2 $\times$ 10$^{16}$ $<$ $N_{\rm ^{13}CO}$ $<$ 3.7 $\times$ 10$^{17}$ cm$^{-2}$ and 0.4 $\times$ 10$^{15}$ $<$ $N_{\rm C^{18}O}$ $<$ 3.5 $\times$ 10$^{16}$ cm$^{-2}$, respectively. The abundance ratios between $^{13}$CO and C$^{18}$O, $X_{\rm ^{13}CO}$/$X_{\rm C^{18}O}$, are found to be 5.7 - 33.0. The mean value of $X_{\rm ^{13}CO}$/$X_{\rm C^{18}O}$ in the nearly edge-on photon-dominated regions is found to be 16.47 $\pm$ 0.10, which is a third larger than that the solar system value of 5.5. The mean value of $X_{\rm ^{13}CO}$/$X_{\rm C^{18}O}$ in the other regions is found to be 12.29 $\pm$ 0.02. The difference of the abundance ratio is most likely due to the selective FUV photodissociation of C$^{18}$O.Comment: 11 pages, 9 figures, Accepted to A&

Studies on the Native Plants in the Coastal Sand Dune (III) Comparison of Leaf Temperature on the Shoot and Stolon Stem of Wedelia prostrata Hemsl

The stolon and shoot stem leaf temperature of Wedelia prostrata Hemsl was investigated in comparison with the meteorological environmental conditions. The maximum leaf temperature was 33.4℃ in the case of the stolon stem and 40.5℃ on the shoot stem. However，the air temperature near the stolon stem leaf was 44.0℃，and the sand surface temperature was 63.0℃. The correlation coefficient between the leaf temperature and the meteorological conditions is as folIows: 1.Air temperature (x) and relative humidity (y) near the stem