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Processes and environmental significance of the subglacial chemical deposits in Tianshan Mountains

Science China Earth Sciences 2005年第9期48卷 1470-1478页

作者： liu gengnian luo risheng cao jun cui zhijiu College of Environmental Sciences Peking University Beijing 100871 China College of Environmental Sciences Peking University Beijing 100871 China College of Environmental Sciences Peking University Beijing 100871 China College of Environmental Sciences Peking University Beijing 100871 China

On the bedrock surface of Glacier No.1 in the headwater of Urumqi River, Tianshan Mts., well layered and crystallized subglacial calcite precipitations were discovered. Based on observations and analysis of the surface form, sedimentary texture and structure, and chemical composition of the deposits, clues about the subglacial processes and environment are deduced. The radial-growth crustation texture of the deposits, which builds up in the saturated CaCO3 so- lution, proves the existence of pressure melting water and water films under Glacier No.1; and their rhythmic beddings, dissolved planes and unconformable contacts show that the water films responsible for the formation of these structures were in a wide range of spatial as well as tem- poral variations. Though formed under continental glacier in non-limestone area, the deposits are quite similar to those formed under temperate glaciers in limestone areas, a fact that shows a similar process of chemical precipitation between the two. Hence the enrichment of calcium in the subglacial melting water and the process of precipitation have actually little to do with the bedrock lithology and the glacier types. The cemented detritus in the deposits are rich in Fe and Al while depleted in K, Na and Si; also the included clay mineral consists mainly of illite, which reveals some weak chemical weathering under the continental glacier. The subglacial CaCO3 precipitates when plenty of Ca++ melt into the subglacial melting water on a comparatively en- closed ice-bedrock interface under a high CO2 partial pressure, the forming of subglacial chemical deposits therefore offers unequivocal evidence for the ongoing of subglacial chemical reactions.

关键词： subglacial processes, chemical deposits, continental glacier.

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Processes and environmental significance of the subglacial chemical deposits in Tianshan Mountains

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Science China Earth Sciences 2005年第9期 144-152页

作者： liu gengnian, luo risheng, cao jun & cui zhijiu College of Environmental Sciences, Peking University, Beijing 100871, China

关键词： subglacial processes chemical deposits continental glacier.

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Characteristics of the subglacially-formed debris-rich chemical deposits and related subglacial processes of Qiangyong Glacier,Tibet

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Journal of Geographical Sciences 2003年第4期13卷 455-462页

作者： luo risheng, cao Jim, liu gengnian, GUI zhijiu(College of Environmental Sciences, Peking University, Beijing 100871, China) Peking University College of Environmental Sciences Beijing China (GRID:grid.11135.37) (ISNI:***)

Subglacially-formed debris-rich chemical deposits were found both on bedrock surface and in bedrock crevice on the edge of Qiangyong Glacier, one of the continental glaciers in Tibet. Grain size distribution, internal structures and chemical components of the chemical deposits were analyzed. It can be inferred that the temperature of some part of the ice-bedrock interface is close to the melting point and there exists pressure melting water under Qiangyong Glacier. Debris, especially those from continental aerosols, can release Ca++ in the water. At the lee-side of obstacles on glacier bed the CO2 in the melting water might escape from the water and the melting water might refreeze due to the dramatically reduced pressure, making the enrichment and precipitation of CaCO3. The existence of subglacial melting water and the process of regelation under Qiangyong Glacier indicate that sliding could contribute some proportion to the entire movement of Qiangyong Glacier and it belongs to multiplex cold-temperate glaciers.

关键词： Qiangyong Glacier, Tibet subglacially-formed chemical deposits subglacial process continental glacier

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