Experiments on metasomatism were carried out in the scheelite-aqueous MnCl₂ solution system at 100, 125 and 150°C.
As a result, the replacement texture of scheelite by huebnerite was confirmed in all experimental systems. Based on SEM observation of the section of the reacted samples, dissolution of scheelite and precipitation of huebnerite are considered to have occurred simultaneously. The replacement texture of scheelite by huebnerite progresses toward the inside of scheelite because there was no change in the form of the sample after the reaction. Since molar volume of huebnerite and scheelite are 41.88 and 47.05 cm³, respectively, large volume of void space is formed in the reaction layer.
Activation energies of the dissolution reaction of scheelite were estimated to be 56.4 kJ/mol in 0.01 mol/l aqueous MnCl₂ solution, 70.2 kJ/mol in 0.10 mol/l aqueous MnCl₂ solution and 62.2 kJ/mol in 1.00 mol/l aqueous MnCl₂ solution.
SEM observation, observation in the polished section and estimated activation energies suggest that the dissolution reaction of scheelite is a rate-limiting factor.

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The Sugashima ultramafic mass is one of the largest ultramafic bodies in the Mikabu belt, and is composed of a hornblende-poor part (Unit I) and a hornblende-rich part (Unit II). Unit I is a layered complex with laminar and convoluted structures probably formed as a crystal mush.
Detailed petrographic studies reveal that orthopyroxene exists in almost all the rock types forming the igneous layering of Unit I: dunite, plagioclase wehrlite and olivine gabbro. Orthopyroxene crystals commonly occur adjacent to olivine crystals and locally show poikilitic textures enclosing olivine grains with rounded or irregular shapes, indicating their peritectic growth from a basaltic magma at a pressure lower than 0.9 GPa.

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Petrography of two metatexite specimens from the Abukuma and Ryoke metamorphic belts in Japan suggests that spinel was produced together with cordierite and granitic melt by a partial melting reaction that consumes sillimanite and biotite. Reproductive experiments were performed at a pressure of 200 MPa and temperatures ranging from 700 to 950°C. The starting material was uncrushed Takanuki pelitic gneiss containing abundant biotite and sillimanite without spinel. From the experimental results we confirm that the following spinel-producing partial melting reaction takes place commonly at 800°C and higher temperatures.
Sillimanite+biotite+plagioclase+quartz±H₂O→spinel+cordierite+granitic melt.
Of particular importance is that spinel occurs only within silica-poor portion of the granitic melts produced at temperatures lower than 900°C. On the other hand, spinel is in direct contact with quartz in the run products at 950°C, being in good harmony with the petrogenetic grid of Vielzeuf and Holloway (1988). Thus it can be pointed out that SiO₂-undersaturated domains are easily formed locally during partial melting due to kinetic reasons and/or to the complete consumption of quartz by the melting reactions in pelitic rocks.

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Planetary geology provides information on processes on the surface and interiorl of terrestria planets, satellites, and asteroids in the solar system. Surface composition and mineralogy is one of clues to understand planetary geology and, in particular, it is essential to determine the composition of planetary surface in order to discuss the origin and geologic/geochemical evolution. The mineralogical information is investigated using spectroscopy in the visible and near-infrared regions of the electromagnetic spectrum, because most of rock-forming minerals exhibit characteristic absorption features at these wavelengths. Especially, silicate minerals such as olivines and pyroxenes show diagnostic absorption bands due to the presence of Fe²⁺. The compositional interpretation of reflectance spectra using the remote sensing techniques is based on the principle of the crystal field theory. Recently, with the advances in computer and detector technology, the new field of imaging spectroscopy is developing in remote sensing. Imaging spectroscopy is an instrument of combination of imaging, technique to obtain planetary images, and spectroscopic technique. While the instrument is in use in the laboratory, in an aircraft, and in Earth-based telescope, only a few spaceborne instruments for planetary observation were applied because of difficulty in technical development. This instrument can obtain a three-dimensional cube data with two spatial and third spectral dimensions and may provide the determination of composition and mapping of compositions across the planetary surface at high resolution. To develop more general views on planetary geology, it will be required to develop the imaging spectroscopy for spacecrafts.

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