ABSTRACT

The size-dependent chemical maturity of sediment cycling in a high-altitude glacial/periglacial environment was studied by examining the sediments of the Chorabari Glacier, Mandakini Valley, central Himalaya, India. Sediments evacuated from glacial debris and a periglacial area were studied via particle-size analysis, X-ray fluorescence, and X-ray diffraction of different grain-size fractions. The results suggest a clear control of grain-size fraction over chemical weathering and release of its attendant nutrients from the glacial substrate. Elemental indices suggest the release of nutrients is principally controlled through comminution and sub-glacial chemical weathering of leachable minerals such as feldspar, mica, and apatite. Owing to biogeochemical cycles, the release of nutrients like phosphorous and calcium is predominantly controlled through mineral dissolution process of aluminosilicate rocks containing apatite, carbonate minerals and organic complexes. Overall, the size-dependent chemical maturity of glacial sediments suggests a much more chemically active system than previously thought. This study is of particular importance for downstream weathering tracer studies of detrital sediments.

摘要

通过检查印度喜马拉雅山中部曼达基尼谷地Chorabari冰川的沉积物，研究了高海拔冰川/冰缘环境中沉积物循环的尺寸依赖性化学成熟度。通过粒度分析，X射线荧光和不同粒度部分的X射线衍射研究了从冰川碎片和冰川周缘区域撤离的沉积物。结果表明，在化学风化作用下可以清楚地控制粒度级分，并从冰质底物中释放其伴随的养分。元素指数表明，养分的释放主要通过可溶矿物（如长石，云母和磷灰石）的粉碎和冰下化学风化来控制。由于生物地球化学循环，磷和钙等营养物质的释放主要通过含有磷灰石，碳酸盐矿物和有机配合物的硅铝酸盐岩石的矿物溶解过程来控制。总体而言，冰川沉积物的尺寸依赖性化学成熟度表明其化学活性体系比以前认为的要多得多。这项研究对于碎屑沉积物的下游风化示踪研究特别重要。