青藏高原中部扎布耶茶卡142ka以来石英砂表面特征及环境意义
李明慧[1,2] 康世昌[1,3] 郑绵平[2]
[1]中国科学院青藏高原研究所,北京100085 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国科学院寒区旱区环境工程研究所冰冻罔科学国家重点实验室,甘肃兰州730000
摘 要:
石英抗风化能力强，表面特征保留了许多环境信息，用扫描电镜方法对石英砂表面结构进行了研究．结果表明：扎布耶茶卡的石英颗粒以次棱角状、次圆状为主，撞击坑、贝壳状断口、平行解理和水下磨光面等机械特征出现频率较高；化学特征有二氧化硅沉淀、蜂窝状溶蚀面、硅质球和蚀坑/洞．石英颗粒经历冲洪积作用，搬运至湖泊后又经历了水下机械和化学作用．在142～60kaBP扎布耶茶卡湖区气候寒冷，但无冰川作用存在，石英颗粒搬运距离近，机械特征主要是强烈的物理风化与冲洪积作用形成的，化学特征与弱的水动力条件有关；8．5～3．7kaBP湖区气候温暖，但变化频繁，湖水进一步成化、退缩，山坡后退变缓，机械特征主要由物理风化及搬运中的碰撞造成，化学特征则与弱的水动力条件和高盐环境有关。[著者文摘]
文章出处:
《冰川冻土》-2008年30卷1期 -125-131页
栏目信息:
分 类 号:
文献标识码:
A
文章编号:
1000-0240（2008）01-0125-07
Surface Textures on Quartz Grains from the Zhabuye Saline Lake in the Middle Tibet Plateau since 142 ka BP
LI Ming-hui, KANG Shi-chang, ZHENG Mian-ping（1 .Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China; 2. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China; 3. State Key Laboratory of Cryospheric Science, CAREERI, CAS, Lanzhou Gansu 730000, China）
Abstract:
Many attempts have been made with scanning electron microscopy （SEM） to correlate quartz sand micro-morphology with sedimentary processes, depositional environments and the palaeo-environmental reconstruction. The purpose of this study is to examine the surface textures of quartz grains to reconstruct the palaeo-environment in Zhabuye Saline Lake. Two sedimentary sections are recovered in the north and terrace of the lake. The sediment in the terrace is dated by U series to be approximately 142-60 ka BP, and the sediment in the northern lake is dated by 14C to be 8.5-3.7 ka BP. The surface textures on quartz grains analyzed by SEM have many physical characteristics such as impact pits, conehoidal breakage fracture, polish surface, parallel cleavage, and chemical characteristics such as abraded pits, honeycombed solution surface, siliceous sphere and SiO2 precipitates. During 142-60 ka BP the physical characteristics in grains showed an effect of strong physical weathering and alleviation from a short transport in cold-dry conditions, and the chemical ones showed that they formed in calm water without glaciation. From 8.5 to 3.7 ka BP the physical characteristics suggested that they were formed in a setting of physical weathering and impact, and the chemical ones kept in touch with calm and high salinity water, indicating the climate became warmer relatively but changed frequently with more briny lake water and low angle hillside.[著者文摘]
Key words:
quartz sands; surface textures; SEM; saline lake; Tibet Plateau
基金资助:
国家自然科学基金项目（40401054;40121101;40771187）;中国科学院“百人计划”项目;国家重点基础研究发展计划（973计划）项目（2005CB422004）资助
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