中国西部冰川冰尘的粒度及矿物组成

Grain Size Distribution and Mineral Components of Cryoconites of Glaciers in Western China

利用Mastersizer 2000型激光粒度分析仪和X-射线衍射仪分析了新疆木扎尔特冰川、唐古拉山小冬克玛底冰川、东昆仑山玉珠峰冰川和祁连山七一冰川冰尘的粒度组成和矿物特征。结果表明,这4条冰川冰尘的粒度组成以粉砂（2~63μm）为主,占62.32%~86.46%;粘土（〈2μm）含量最低,占2.77%~7.40%。平均粒径的顺序依次是：木扎尔特冰川（84.96±45.14μm）〉玉珠峰冰川（38.96±13.94μm）〉小冬克玛底冰川（34.76±11.41μm）〉七一冰川（20.21±15.81μm）。矿物成份分析表明,冰尘中的碎屑矿物含量高于粘土矿物,主要以石英和长石为主。除木扎尔特冰川之外,其他3条冰川冰尘中的伊利石含量在粘土中最高。七一冰川的伊利石和高岭石含量都高于玉珠峰冰川和小冬克玛底冰川。伊利石和高岭石等均为铝硅酸盐的风化分解产物,来源于陆源物质。伊利石和高岭石含量自东向西减少,说明木扎尔特冰川冰尘主要来自寒冷环境下岩石经过的物理风化而非化学风化形成的局地粉尘。其他3条冰川冰尘除局地来源外,还有一部分是陆源物质经一定距离搬运后物理风化分解而成。

By using Mastersizer 2000 laser particle size analyzer and XRD systems,this paper discusses the characteristics of particle size distribution and mineral components of cryoconites collected from MZRT glacier,XDKMD glacier,YZF glacier and QY glacier in western China. The results show that the cryoconites of these four glaciers are dominated by silt（ 2- 63μm） and clay（ 〈2 μm）,the content of coarse silt and clay accounts for 62. 32% ~86. 46% and 2. 77% ~ 7. 40%,respectively. The mean particle of cryoconites in these four glaciers are in the sequence of MZRT（ 84. 96 ± 45. 14 μm） 〉YZF（ 38. 96 ± 13. 94 μm）〉 XDKMD（ 34. 76 ± 11. 41 μm） 〉QY（ 20. 21 ± 15. 81 μm）. The X- ray diffraction analysis data show that the cryoconites samples in these four glacers contains relatively more mineral materials,and the contents of quartz and feldspar are mainly detrital mineral. In addition to MZRT glaciers,the content of illite in cryoconite clay in other three glaciers is the highest. Because the illite and kaolinite are all the product of mineral weathering and decompose of aluminosilicate,they come from terrestrial matter. The contents of illite and kaolinite decresed from east to west in Tibetan Plateau,indicating that the cryoconites in MZRT glaciers come from local dust formed through grinding and frost weathering during rock deformation,chemical weathering is in its early stages. The cryoconite in other three glaciers come from the terrestrial inputs after transporting at enough of distance,through physical weathering and decomposing.