35 research outputs found
Sm-Nd isotopic systematics of lherzolitic shergottite Yamato-793605
We have undertaken Sm-Nd isotopic studies on Yamato-793605 lherzolitic shergottite. The Sm-Nd internal isochron obtained for acid leachates and residues of whole-rock and separated mineral fractions yields an age of 185Ā±16Ma with an initial ĪµNd value of +9.7Ā±0.2. The obtained Sm-Nd age is, within analytical errors, identical to the Rb-Sr age of this meteorite as well as to the previous Rb-Sr and Sm-Nd ages of Allan Hills-77005 and Lewis Cliff 88516, although the Īµ_(Nd) values are not identical to each other. Elemental abundances of lithophile trace elements remain nearly unaffected by aqueous alteration on the Martian surface. The isotopic systems of lherzolitic shergottites, thus, are considered to be indigenous, although disturbances by shock metamorphism are clearly observed. "Young ages of ļ½180Ma" have been consistently obtained from this and previous Rb-Sr, Sm-Nd and U-Pb isotopic studies and appear to represent crystallization events
Rb-Sr isotopic systematics of lherzolitic shergottite Yamato-793605
We have undertaken a Rb-Sr isotopic study of the lherzolitic shergottite, Yamato (Y)-793605. The acid-leaching experiment designed to remove secondary Pb contamination during previous work with U-Th-Pb systematics did not significantly affect the Rb-Sr systematics. A Rb-Sr internal isochron obtained for combined data of leachates and residues yielded an age of 173Ā±14Ma with an initial ^Sr/^Sr ratio of 0.71042Ā±0.00007,using Ī» (^Rb)=1.402Ć10^y^. The Rb-Sr age, initial ^Sr/^Sr ratio and trace element abundance pattern of Y-793605 are all similar to those of lherzolitic shergottites, ALH 77005 and LEW 88516. We favor the 173Ma age for the time of igneous crystallization, because this interpretation is more consistent with characteristics of both the isotopic systematics and mineral chemistry. A minor disturbance of U-Pb systems observed in residue fractions indicate that shock event(s) occurred more recently, without affecting Rb-Sr system
Trace element and isotopic characteristics of inclusions in the Yamato ordinary chondrites Y-75097, Y-793241 and Y-794046
Igneous inclusions and hosts of the Yamato ordinary chondrites Y-75097 (L6), Y-793241 (L6) and Y-794046 (H5) were analyzed for lithophile trace elements, and Rb-Sr, rare gas and oxygen isotopes, together with preliminary petrographic examinations. On a three oxygen-isotope plot, all the inclusions lie near the H-chondrite field. The Y-75097 host and inclusion were severely shocked and the Rb-Sr systematics were disturbed by a 500Ma event which was defined by the K-Ar age. The Y-793241 host and inclusion are unshocked and have an old K-Ar age of 4270Ā±170Ma and undisturbed Rb-Sr systematics for the bulk meteorite. Both Y-75097 and Y-793241 inclusions have similar chemical compositions and mineral assemblages consisting mainly of olivine (Fa_), and minor plagioclase (An_), chlor-apatite, merrillite and chromite. Olivines in both inclusions equilibrated with those of their L6 hosts. The two inclusion mantles consisting of mainly olivine and plagioclase show a highly fractionated REE pattern with middle REE depletion and a large positive Eu anomaly (50-100 times chondritic) (V-shaped). A model calculation suggests that this remarkable REE fractionation was produced by thermal equilibration with the phosphate-rich cores of inclusions during the igneous formation and the metamorphic event. The Y-794046 inclusion comprises abundant anhedral olivines (Fa_), fractured pyroxenes (Fs_) and microcrystalline plagioclase (An_Ab_Or_). The inclusion did not equilibrate with its host which has less Fe-rich olivines (Fa_) and more Fe in pyroxenes (Fs_). The inclusion shows an unfractionated REE pattern. We suggest that the three inclusions formed by melting of differentiated precursor materials carrying unfractionated REE. They were then incorporated into the L-or H-chondrite parent bodies and subjected to the early thermal metamorphism, which eventually overprinted the fractionated REE in the Y-75097 and Y-793241 inclusions by solid/solid equilibrium partitioning. The Y-794046 inclusion was subjected to less extensive equilibration, so that REE abundances remained unfractionated
Correlation between musculoskeletal structure of the hand and primate locomotion: Morphometric and mechanical analysis in prehension using the cross- and triple-ratios
Biometric ratios of the relative length of the rays in the hand have been analyzed between primate species in the light of their hand function or phylogeny. However, how relative lengths among phalanges are mechanically linked to the grasping function of primates with different locomotor behaviors remains unclear. To clarify this, we calculated cross and triple-ratios, which are related to the torque distribution, and the torque generation mode at different joint angles using the lengths of the phalanges and metacarpal bones in 52 primates belonging to 25 species. The torque exerted on the finger joint and traction force of the flexor tendons necessary for a cylindrical grip and a suspensory hand posture were calculated using the moment arm of flexor tendons measured on magnetic resonance images, and were compared among\ua0Hylobates\ua0spp.,\ua0Ateles\ua0sp., and\ua0Papio hamadryas. Finally, the torques calculated from the model were validated by a mechanical study detecting the force exerted on the phalanx by pulling the digital flexor muscles during suspension in these three species. Canonical discriminant analysis of cross and triple-ratios classified primates almost in accordance with their current classification based on locomotor behavior. The traction force was markedly reduced with flexion of the MCP joint parallel to the torque in brachiating primates; this was notably lower in the terrestrial quadrupedal primates than in the arboreal primates at mild flexion. Our mechanical study supported these features in the torque and traction force generation efficiencies. Our results suggest that suspensory or terrestrial quadrupedal primates have hand structures that can exert more torque at a suspensory posture, or palmigrade and digitigrade locomotion, respectively. Furthermore, our study suggests availability of the cross and triple-ratios as one of the indicators to estimate the hand function from the skeletal structure
Dissolved helium distribution in deep groundwaters from the Tono area, central Japan: a tool for tracing groundwater flow in fractured granite
Effects of terrigenic He components on tritiumāhelium dating: A case study of shallow groundwater in the Saijo Basin
Dating using a combination of 3H and 3He is believed to be the most practical method for estimating the short residence time of shallow groundwater. However, this method must estimate tritiogenic 3He alone and tends to overestimate the residence time of groundwater, if terrigenic 3He from the mantle cannot be excluded from the total dissolved 3He. We demonstrate the exclusion of terrigenic 3He in the Saijo Basin, where mantle He is easily released along the major active fault, Median Tectonic Line. The 3He/4He ratios suggest that the west bank of the Kamo River, which lies within the basin, has experienced greater emanations of mantle He than the east bank. We estimate the residence times to be 1.1ā96 years by the proposed exclusion method
Multivariate statistical analyses of rare earth element compositions of spring waters from the Arima and Kii areas, Southwest Japan
The geochemistry of water and gas phases from high pCO
Two types of cold CO2 rich groundwaters are located within the northern part of the Sikhote-Alin ridge: the first type is a CaāMgāHCO3 water with low TDS content (ā¤ 1.7 g/l) and high concentrations of Fe2+, Mn2+, Ba2+, and SiO2, whilst the second type is a NaāHCO3 water with a high TDS content (ā 14 g/l) and elevated concentrations of Li+, Btot, Sr2+, Brā, and Iā. A notable feature of these waters is a predominance of CO2 in the gas phase (up to 99 vol. %) and low contents of other gases (CH4, N2, O2, etc.). The origins of both water types can be identified on the basis of water (Ī“D, Ī“18O) and gas (Ī“13C, 3He/4He, 4He/20Ne) isotopic compositions considered in the context of the geology and hydrology of the region