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281.
282.
Abstract. The Cerro Colorado intrusive stock in the northeastern Chilean Precordillera is a plutonic complex formed during Late Cretaceous (64–72 Ma), and consists predominantly of pyroxene-bearing biotite monzogabbro (Colorado Unit), with lesser amounts of pyroxene-bearing hornblende biotite diorite (Pucaquisca Unit) and biotite hornblende monzonite (Pabellón Unit). Compositional variations of major and trace elements suggest that the Cerro Colorado complex is composed of shoshonitic alkali granitoids generated at the active continental margin. The basic to intermediate rocks of the Colorado Unit are characterized by high contents of A12 O3 (>20 wt%), CaO and LIL elements (K, Sr, Ba), high Fe/Mg ratio and fairly low contents of Cr, Ni and Y. These characteristics suggest that the Colorado Unit was formed by plagioclase-free source magma originated from asthenospheric mantle or mafic lower crust. All the Cerro Colorado rocks generally display linear compositional trends, and the latest Pabellón Unit rocks are richer in SiO2 than the Colorado Unit and Pucaquisca Unit rocks. These indicate that the Pabellón Unit rocks were produced by assimilation-fractional crystallization process of the basic to intermediate magma genetically related to the voluminous Colorado Unit. 相似文献
283.
The Cassini probe observed a young and smooth surface around the south pole of Enceladus, while around the north pole the surface was found to be relatively old and inactive (Porco, C.C. et al. [2006]. Science 311, 1393–1401). This heterogeneous surface implies that the ice thickness of Enceladus is not uniform between the north and south polar regions. Determining the thickness of the icy layer is important to confirm the existence of an internal ocean as well as to reveal the heating mechanism of Enceladus. We show that the measurement of radio waves induced by cosmic neutrinos can be an effective method to constrain the ice thickness of a localized area where conventional gravity or electromagnetic field measurements cannot be used. This method could be used to constrain the thickness of the icy layer on Enceladus even if the ice is a few tens of kilometers thick, measuring over a period of several years, which greatly exceeds the ability of radar sounding, and hence could be used in future orbiter missions. 相似文献
284.
Youhei Kawamura Ashraf M. Dewan Bert Veenendaal Masahiro Hayashi Takeshi Shibuya Itaru Kitahara 《International Journal of Digital Earth》2014,7(4):279-293
Communications network damage resulting from a large disaster causes difficulties in the ability to rapidly understand the current situation and thus make appropriate decisions towards mitigating problems, such as where to send and dispense emergency supplies. The research outlined in this paper focuses on the rapid construction of a network after a disaster occurs. This study suggests ZigBee and geographic information systems (GIS) technologies to resolve these problems and provide an effective communication system. The experimental results of the ZigBee network system are presented, examples are provided of the mapping and analysis undertaken using GIS for the disaster-stricken area of Tsukuba City, Japan, and the communications node arrangements are determined for this region. These results demonstrate the effectiveness of establishing such a communications system for supporting efforts to relieve disaster-damaged areas. 相似文献
285.
286.
Akihiro Tamura Shoji Arai Satoko Ishimaru Eric S. Andal 《Contributions to Mineralogy and Petrology》2008,155(4):491-509
Peridotite samples recovered from IODP Site U1309 at the Atlantis Massif in the Mid-Atlantic Ridge were examined to understand
magmatic processes for the oceanic core complex formation. Original peridotite was fragmented, and the limited short peridotite
intervals are now surrounded by a huge gabbro body probably formed by late-stage melt injections. Each peridotite interval
has various petrographical and geochemical features. A spinel harzburgite in contact with gabbro shows evidence of limited
melt penetrations causing gradual compositional change, in terms of trace-element compositions of pyroxenes, as well as modal
change near the boundary. Geochemistry of clinopyroxenes with least melt effects indicates that the harzburgite is originally
mantle residue formed by partial melting under polybaric conditions, and that such a depleted peridotite is one of the components
of the oceanic core complex. Some of plagioclase-bearing peridotites, on the other hand, have more complicated origin. Although
their original features were partly overprinted by the injected melt, the original peridotites, both residual and non-residual
materials, were possibly derived from the upper mantle. This suggests that the melt injected around an upper mantle region
or into mantle material fragments. The injected melt was possibly generated at the ridge-segment center and, then, moved and
evolved toward the segment end beneath the oceanic core complex. 相似文献
287.
Well‐preserved oval‐shaped dunite clots occur within the exceptionally fresh massive podiform chromitites from the Coto Block of the Zambales Ophiolite Complex, the Philippines. The dunite/chromitite boundary shows an interlocking texture; olivine inclusions in chromites in the podiform chromitites show the same optical extinction with larger adjacent olivines in the dunite clots. This texture was formed by the reaction between chromite‐oversaturated melt and its dunite inclusions. The existence of such type of melt was previously only hypothesized to explain the origin of layered and podiform chromitites but is now confirmed by this discovery. 相似文献