北極新奧爾松冰川沉積物的地球化學(xué)特征研究
發(fā)布時(shí)間：2018-09-18 19:06
【摘要】：高緯度冰川沉積物是全球冰川成因粉塵釋放的重要來(lái)源,粉塵的釋放影響著全球的氣候、大氣氣溶膠、海洋化學(xué)元素和生產(chǎn)力。過(guò)去對(duì)粉塵的源區(qū)(如沙漠和黃土)的研究主要集中在中、低緯度地區(qū),對(duì)來(lái)自高緯度的冰川成因的粉塵研究較少。本文以北極新奧爾松地區(qū)冰川沉積物為研究對(duì)象,通過(guò)野外調(diào)查、實(shí)驗(yàn)分析和數(shù)據(jù)處理等綜合方法,對(duì)冰磧物和冰水沉積物的粒徑、磁化率、主微量元素、同位素組合、碳酸鹽礦物、粘土礦物和鐵氧化物礦物組合等特征進(jìn)行詳細(xì)分析,探究現(xiàn)代新奧爾松高緯度冰川作用下冰川沉積物的產(chǎn)出特征以及剝蝕作用和化學(xué)風(fēng)化對(duì)冰川沉積物的地球化學(xué)特征的影響。主要獲得了以下的認(rèn)識(shí):(1)新奧爾松冰磧物平均粒徑介于9.5～194.4μm,平均值為69.6μm,以粉砂級(jí)和砂級(jí)為主,粘粒較少。粒度頻率分布大部分呈雙峰或多峰特征,典型的細(xì)顆粒組分峰值在10～30μm,粗顆粒組分峰值在100～200μm。新奧爾松冰川壓碎和磨碎的顆粒界限是1mm,大于一般認(rèn)為的0.5mm,說(shuō)明該地區(qū)冰川作用可能相對(duì)較弱。冰磧物沉積之后受剝蝕作用影響會(huì)造成細(xì)組分損失。冰水沉積物平均粒徑為23.7μm,粒度分布呈單峰特征,峰值在20～30μm,代表著冰磧物中的細(xì)組分部分。(2)冰磧物和冰水沉積物磁化率平均值分別為9.7×10-8m3Kg-1和8.5×10-8m3Kg-1,于當(dāng)?shù)鼗鶐r相當(dāng),且于鐵元素含量正相關(guān)。不同沉積物區(qū)位和年齡的冰川沉積物磁化率無(wú)顯著差異,說(shuō)明該地區(qū)很弱的成壤作用。對(duì)A冰川冰磧物的研究發(fā)現(xiàn)出露時(shí)間長(zhǎng)的冰磧物的磁化率值與粒度組成有關(guān),粒度越小,磁化率越高。本文認(rèn)為冰川沉積物的磁化率由母巖決定還受剝蝕作用制約。(3)冰磧物化學(xué)風(fēng)化指數(shù)(CIA)值主要介于55～70,CIA值能從整體上反映LIA冰磧物和冰沼土的化學(xué)風(fēng)化差異。就LIA冰磧物而言,CIA值變化受剝蝕作用影響,并不指示風(fēng)化強(qiáng)度。冰磧物平均化學(xué)組成與黃土和上部大陸地殼非常接近,且CIA值集中分布在UCC至黃土的平均化學(xué)組成風(fēng)化趨勢(shì)線(xiàn)上,說(shuō)明黃土粉塵可能起源于由一系列的冰川和高山作用的剝蝕。(4)冰磧物在冰緣環(huán)境易發(fā)生碳酸鹽礦物的淋溶作用,非以富含碳酸鹽礦物的巖石為母質(zhì)的冰磧物中,粒徑小于2μm的碳酸鹽礦物基本被完全淋溶。苔原植被演替導(dǎo)致的生物化學(xué)風(fēng)化作用可能是碳酸鹽淋溶的主要?jiǎng)恿Α?5)冰水沉積物與冰磧物地球化學(xué)特征無(wú)顯著差異,冰水沉積物除頂部碳酸鹽礦物被淋失外,其余整個(gè)剖面均含小于2μm的碳酸鹽礦物,說(shuō)明剖面沉積物有相當(dāng)一部分直接來(lái)自冰川壓磨巖屑,可能未接受苔原表生作用影響。冰川沉積物的粘土礦物為碎屑沉積,以伊利石(平均含量為63%)、高嶺石(平均含量為19%)、綠泥石(平均含量為17%)為主;粘粒中高的87Sr/86Sr比值可能是當(dāng)前新奧爾松乃至斯?fàn)柾甙腿簫u冰川粉塵釋放的重要指紋特征。冰川沉積物的鐵氧化物礦物并非成壤控制,其特征由其母巖決定,針鐵礦和赤鐵礦的平均含量分別為 0.34%和 0.2%。(6)本文中冰水沉積物的地球化學(xué)特征的變化主要反映物源波動(dòng),并不指示區(qū)域化學(xué)風(fēng)化強(qiáng)度�？傮w而言,冰緣環(huán)境下冰川末端輸出的巖屑其地球化學(xué)特征由其母巖決定,受環(huán)境、氣候變化影響很小;碳酸鹽礦物淋失是冰川沉積物在冰緣環(huán)境風(fēng)化的主要體現(xiàn)。
[Abstract]:High latitude glacial sediments are an important source of global glacial-derived dust emissions, which affect global climate, atmospheric aerosols, marine chemical elements and productivity. In this paper, the glacial sediments in the New Orson area of the Arctic are taken as the research object. The grain size, magnetic susceptibility, major and trace elements, isotope composition, carbonate minerals, clay minerals and iron oxide mineral assemblages of till and glacial water sediments are analyzed in detail through field investigation, experimental analysis and data processing. The characteristics of glacial sediments and the effects of denudation and chemical weathering on the geochemical characteristics of glacial sediments under the action of modern high latitude glaciers in New Orleans are studied. The grain size distribution is mostly bimodal or multi-modal. The typical peak value of fine-grained components is 10-30 micron and that of coarse-grained components is 100-200 micron. The average grain size of the glacial water sediments is 23.7 micron, and the grain size distribution shows a single peak, with a peak value of 20-30 micron, representing the fine fraction of the till. (2) The average magnetic susceptibility of the till and glacial water sediments are 9.7 *10-8 m3 Kg-1 and 8.5 *10-8 m3 Kg-1, respectively, which are equivalent to the local bedrock and the content of iron element. The magnetic susceptibility of glacial sediments at different locations and ages is not significantly different, indicating that the area is weak in the formation of soil. The study of glacial tills at A shows that the magnetic susceptibility of glacial sediments with long exposure time is related to grain size composition. The smaller the grain size, the higher the magnetic susceptibility. (3) The chemical weathering index (CIA) of tills is mainly between 55 and 70, which can reflect the difference of chemical weathering between LIA tills and glacial marsh soils as a whole. The CIA values are very close to each other and are concentrated on the weathering trend line of the average chemical composition from UCC to the loess, indicating that the Loess dust may originate from erosion by a series of glaciers and mountains. (4) The tills are prone to leaching of carbonate minerals in periglacial environments, while the tills are not derived from carbonate-rich rocks. The biochemical weathering caused by vegetation succession in tundra may be the main driving force for carbonate leaching. (5) There is no significant difference in geochemical characteristics between glacial water sediments and tills. Except that carbonate minerals are leached from the top of glacial water sediments, the whole section contains less than 2 microns. Carbonate minerals indicate that a considerable portion of the sediments in the profile come directly from glacial grinding debris and may not be affected by tundra epigenesis. Clay minerals in the glacial sediments are clastic deposits, dominated by illite (63%), kaolinite (19%) and chlorite (17%) with a high 87Sr/86Sr ratio in clay grains. The average content of goethite and hematite is 0.34% and 0.2% respectively. (6) The geochemical characteristics of glacial water sediments in this paper are the main changes. Generally speaking, the geochemical characteristics of the debris exported from the end of the glacier in periglacial environment are determined by its parent rocks, and the influence of environment and climate change is very small. The leaching of carbonate minerals is the main manifestation of the weathering of the glacial sediments in periglacial environment.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：P343.6
本文編號(hào)：2248823
[Abstract]:High latitude glacial sediments are an important source of global glacial-derived dust emissions, which affect global climate, atmospheric aerosols, marine chemical elements and productivity. In this paper, the glacial sediments in the New Orson area of the Arctic are taken as the research object. The grain size, magnetic susceptibility, major and trace elements, isotope composition, carbonate minerals, clay minerals and iron oxide mineral assemblages of till and glacial water sediments are analyzed in detail through field investigation, experimental analysis and data processing. The characteristics of glacial sediments and the effects of denudation and chemical weathering on the geochemical characteristics of glacial sediments under the action of modern high latitude glaciers in New Orleans are studied. The grain size distribution is mostly bimodal or multi-modal. The typical peak value of fine-grained components is 10-30 micron and that of coarse-grained components is 100-200 micron. The average grain size of the glacial water sediments is 23.7 micron, and the grain size distribution shows a single peak, with a peak value of 20-30 micron, representing the fine fraction of the till. (2) The average magnetic susceptibility of the till and glacial water sediments are 9.7 *10-8 m3 Kg-1 and 8.5 *10-8 m3 Kg-1, respectively, which are equivalent to the local bedrock and the content of iron element. The magnetic susceptibility of glacial sediments at different locations and ages is not significantly different, indicating that the area is weak in the formation of soil. The study of glacial tills at A shows that the magnetic susceptibility of glacial sediments with long exposure time is related to grain size composition. The smaller the grain size, the higher the magnetic susceptibility. (3) The chemical weathering index (CIA) of tills is mainly between 55 and 70, which can reflect the difference of chemical weathering between LIA tills and glacial marsh soils as a whole. The CIA values are very close to each other and are concentrated on the weathering trend line of the average chemical composition from UCC to the loess, indicating that the Loess dust may originate from erosion by a series of glaciers and mountains. (4) The tills are prone to leaching of carbonate minerals in periglacial environments, while the tills are not derived from carbonate-rich rocks. The biochemical weathering caused by vegetation succession in tundra may be the main driving force for carbonate leaching. (5) There is no significant difference in geochemical characteristics between glacial water sediments and tills. Except that carbonate minerals are leached from the top of glacial water sediments, the whole section contains less than 2 microns. Carbonate minerals indicate that a considerable portion of the sediments in the profile come directly from glacial grinding debris and may not be affected by tundra epigenesis. Clay minerals in the glacial sediments are clastic deposits, dominated by illite (63%), kaolinite (19%) and chlorite (17%) with a high 87Sr/86Sr ratio in clay grains. The average content of goethite and hematite is 0.34% and 0.2% respectively. (6) The geochemical characteristics of glacial water sediments in this paper are the main changes. Generally speaking, the geochemical characteristics of the debris exported from the end of the glacier in periglacial environment are determined by its parent rocks, and the influence of environment and climate change is very small. The leaching of carbonate minerals is the main manifestation of the weathering of the glacial sediments in periglacial environment.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：P343.6
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