【摘要】 冰碛物是全球的一个主要粉尘源,联系着全球气候、大气气溶胶、海洋元素和生产力的变化。过去对粉尘,特别是沙漠、黄土的研究主要集中在中纬度地区,但对来自高纬度的冰川粉尘研究较少。为了解现代高纬度冰缘环境下冰川作用、搬运作用和化学风化对冰碛物的物理化学性质的影响,本文以北极新奥尔松Austre Lovénbreen冰川（简称A冰川,下同）深度小于5cm的冰碛物（包括小冰期冰碛物和冰沼土）≤2mm组分为对象,测定了小冰期（Little Ice Age,简称LIA）冰碛物和冰沼土的粒径、磁化率以及元素组成。研究表明:1)A冰川冰碛物粒径组成以砂级为主（>63μm）、粉砂级次之（2⁶3μm）、粘粒最少（<2μm）。A冰川冰碛物大部分呈双峰或多峰特征,LIA冰碛物典型双峰峰值为10³0μm和100²00μm;冰沼土为30⁶0μm和300⁴50μm。近岸LIA冰碛物和冰沼土相对冰川末端LIA冰碛物具有较粗的平均粒径及较高的正偏度,表明其在沉积之后受搬运作用影响损失了细组分。2)A冰川冰碛物磁化率介于5.5×10^-811.4×10^-8m³/kg之间,平均值为7.7×10^-8m³/kg。LIA冰碛物磁化率与总铁含量呈正相关,主要受母岩和搬运作用制约,未受成壤作用影响。3)A冰川冰沼土与LIA冰碛物相比,富Si,但贫Al、Fe、K、Ca、Mg等元素;LIA冰碛物平均化学组成与洛川黄土和上部大陆地壳（Upper Continental Crust,简称UCC）非常接近。A冰川冰碛物CIA平均值为58.57,反映冰缘环境较弱的化学风化条件。A冰川冰碛物CIA值集中分布在UCC至黄土的平均化学组成风化趋势线上,证明了黄土粉尘起源于由一系列的冰川和高山作用产生的沉积物的可能性。分析结果表明,在弱风化的冰缘环境下,CIA值能从整体上反映LIA冰碛物和冰沼土的化学风化差异,但对沉积年龄小的LIA冰碛物而言,搬运作用引起的粒度组成差异和相应的不同矿物类型和含量的改变或是CIA值变化的主要原因。更多还原

【Abstract】 Moraines are main sources of global dusts,which link to global climate,atmospheric aerosol,the oceanic elemental cycles and productivity of the ocean.There has been a focus on the studies of contemporary dust sources（especially the desert and loess） at middle latitudes,but these have been little study of modern high-latitude dust sources,which come primarily from glacial sources.For understanding influence of glaciation,transportation and chemical weathering to physical and chemical property of moraines in modern periglacial environment,here,we investigate the grain size,magnetic susceptibility and chemical elements of moraines（grain size ≤ 2mm） from Austre Lovénbreen glacier,Ny-lesund,Arctic.32 moraines have been sampled on the ground surface at the depth of no more than 5cm in front of Austre Lovénbreen glacier,which covers 5.69km² with its terminus at an elevation of 100 m.These samples can be divided into two parts,28 LIA（Little Ice Age） moraines（sedimentation age ≤ 100 years） and 4 tundra soil samples（sedimentation age ≈ 8762 years）.The results display that;（1） Among the grain sizes of glacial moraines,sand（>63μm） occupies first place,silt（2⁶3μm） comes second and clay（<2μm） is the least.For most moraines,grain size distribution of them generally show bimodal or multimodal spectrum,and the spectrum peaks of LIA moraines and tundra soils appear at 10³0μm,100²00μm and 30⁶0μm,300⁴50μm respectively.Nearshore LIA moraines and tundra soils have more coarse average grain sizes and higher positive skewness than LIA moraines near the terminus of Austre Lov6 nbreen glacier,indicating that fine component（≤63μm） of them was lost distinctly because of transportation.（2） The magnetic susceptibility of moraines ranges from 5.5×10^-8m³/kg to 11.4×10^-8 m³/kg with the average of 7.7×10^-8 m³/kg.It can be found that the magnetic susceptibility of moraines is positively correlated with total iron content,depends on parent material and has an effect by transportation and size sorting.The pedogenesis is weak in periglacial environment.（3） Compared with LIA moraines,tundra soils accumulate Si and deplete Al,Fe,K,Ca and Mg elements.The average chemical compositions of LIA moraines are very similar pattern with Luochuan loess and Clark values of UCC（Upper Continental Crust）.The average of CIA（Chemical Index of Alteration） values is58.57,which indicates the low weathering intensity in periglacial environment.The moraines’ values plotted on a trend between UCC and Luochuan loess in triangle chart of CIA,thus,provides an implication that the loess dust could come from moraines which are the glaciogenic dust sources.Based on the observations,we suggest that the CIA values can generally tell the difference of weathering intensity between of LIA moraines and tundra soils in periglacial environment.For LIA moraines that were deposited with relatively short time,the CIA values could mainly be changed by the grain size sorting and corresponding changes of different mineral types and contents in sediment transportation.更多还原