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The kinetics of non-catalyzed decompositions of xylose and its decomposition product furfural in high temperature liquid water (HTLW) was studied for temperature from 180 to 220℃ and under pressure of 10MPa. The main products of xylose decomposition were furfural and formic acid, and furfural further degraded to formic acid under HTLW condition. With the assumption of first order kinetics equation, the evaluated activation energy of xylose and furfural decomposition was 123.27kJ•mol -1 and 58.84kJ•mol -1 , respectively.

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The North Xinjiang region (NW China) is an important part of the Central Asia Orogenic Belt, situated at the junction of Siberia, Tarim and Kazakhstan plates. It is an area characterized by multiple stages of Phanerozoic continental growth, during which several porphyry and epithermal systems were formed. The relationship of these mineral systems to the geodynamic evolution of the region has not yet been well understood. In this paper, we list the main geological characteristics of 21 significant epithermal precious and base metal deposits in North Xinjiang, and classify them into high-sulfidation and low-sulfidation styles, with the latter being predominant. We have selected seven epithermal deposits representing different styles formed under different tectonic regimes and discuss their geology and geochemistry in some detail. The depositscale geology and geochemistry of epithermal systems in North Xinjiang are essentially similar to those in other parts of the world. All epithermal deposits in North Xinjiang are hosted in volcanic rocks with ages ranging from Devonian to Triassic, with the Early Carboniferous volcanic sequences being the most important, followed by the Permian and Triassic. The Devonian-Early Carboniferous host rocks belong to the calc-alkaline series that developed in pre-collisional arc-back-arc basin systems; whereas the Permian-Triassic host volcanic rocks of shoshonite series formed in post-subduction regimes. Available isotopic ages of these epithermal systems cluster in two periods: Early Carboniferous ([320 Ma) and Late Carboniferous-Triassic (320-220 Ma), reflecting two metallogenic episodes that occurred during subductionrelated accretion and post-subduction collision regimes, respectively. Accordingly, three groups of epithermal deposits in North Xinjiang can be recognized as (1) precollisional deposits without or with negligible collisionalrelated modification, (2) deposits formed in collision regime and (3) ore systems strongly overprinted by fluid flow in post-subduction collision regime.