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Hydrothermal syntheses of microstructures of semiconducting ZnO are reported. Top- and bottom-closed, single-crystalline hexagonal microtubes of ZnO exhibiting wide emission in the UV-visible range are successfully fabricated by a facile, template and base-free hydrothermal growth.

The fractionation of lithium isotopes between synthetic spodumene as representative of Li-bearing clinopyroxene and Cl- and OH-bearing aqueous fluids was experimentally determined between 500 and 900[degrees]C at 2.0 GPa. In all the experiments, [sup.7]Li was preferentially partitioned into the fluid. The fractionation is temperature dependent and approximated by the equation [DELTA][sup.7][Li.sub.(clinopyroxene-fluid)] = -4.61x(1,000/T [K]) + 2.48; [R.sup.2] = 0.86. Significant Li isotopic fractionation of about 1.0 [per thousand] exists even at high temperatures of 900[degrees]C. Using neutral and weakly basic fluids revealed that the amount of fractionation is not different. The Li isotopic fractionation between altered basalt and hot spring water (350[degrees]C) in natural samples is in good agreement with our experimentally determined fractionation curve. The data confirm earlier speculations drawn from the Li isotopic record of dehydrated metamorphic rocks that fluids expelled from a dehydrating slab carry heavier Li into the mantle wedge, and that a light Li component is introduced into the deeper mantle. Li and Li isotopes are redistributed among wedge minerals as fluids travel across the wedge into hotter regions of arc magma production. This modifies the Li isotopic characteristics of slab-derived fluids erasing their source memory, and explains the absence of cross-arc variations of Li isotopes in arc basalts.

The hydrothermal synthesis and structural characterization of two new germanates with an interesting structure containing double helical Ge-chains and unusual [Ge.sub.4][(OH).sub.4] cubanes is reported. Both germanates keep the same topological novel inorganic framework, which is assembled from [Ge.sub.4][(OH).sub.4] cubane and chiral intertwined Ge-O double helices.