Mingzhong Tian

Physical and chemical properties of sound-producing and soundless sand particles from booming sand dunes, northern China

This study here is the result of a comparative study of the geomorphic features, grain size distribution, major mineral components, and micro-textures of sound-producing and soundless sands from three geoparks in north China, and discusses the possible causes of this naturally occurring, physical phenomenon. The sound-producing sand dunes we have investigated are situated along a curvilinear belt of deserts and experience variable precipitation–evaporation rates on a yearly basis. “Singing sands” occur mainly on barchan-type dunes and adjacent to lakes or springs, whereas soundless sands are mainly located in desert areas where there is no nearby surface or groundwater sources. We have analyzed samples from nine sound-producing and two soundless sand dunes using grain size, X-ray diffraction and fluorescence, and SEM analyses. All sand types are composed largely of quartz and feldspar, but sound-producing sands also contain secondary minerals such as kaolinite (3–5%), albite (2–6%), microcline (2–5%), and calcite (5%) that are lacking in the soundless sand samples. Sound-producing sands are generally fine-grained whereas soundless sands are coarse-grained, and all sand types are generally sub-rounded to rounded indicating long transport distance from their provenance. Sphericity values of both sand types are nearly identical with predominantly oblate shapes. Surface pitting is not a unique feature of either sand types, and hence can be ruled out as a major cause of the acoustic properties of sound-producing sands. Densely distributed dissolution features such as scale-like upturned plates and silica scales on grain surfaces contribute significantly to the sound emission of singing sands. Thus, the physical–climatic conditions in deserts such as the presence of surface water and groundwater and precipitation–evaporation rates, which collectively control the formation and distribution of dissolution features on sand surfaces, have a first-order control on the production of sound-producing sands.

Dynamic Variation of Vegetation Fraction for Ion-Absorbing Type Rare Earths Ore in South China Based on Landsat Data——Case Study of Longnnan Rare Earths Mines

Ion-absorbing Type Rare Earths Ore mining caused a series of environmental problems. The thesis focused on the study of the district for heavy rare earth in Longnan County, Jiangxi Province, South China. It examined characteristics of spatial-temporal variation for vegetation fraction (vf) in study area by 10 images of Landsat TM and ETM+ during 1988 to 2009. The results supported that: (1) there were spatial-temporal differences of vf in each mineral district and the areas for medium to high vf dominated in mineral districts, but low vf distributed on concentrated mining districts; (2) dynamic variation for vf differentiated in each mining area each stage, no change areas dominated in mineral districts, but negative change areas only distributed on concentrated mining districts; (3) the history of production, various technologies and preventive measures were the main factors caused spatial-temporal differences of vf in mineral districts.