基于U-Pb定年和单颗粒锆石粒径分析示踪中国黄土高原黄土和红粘土物源  

Tracing the Provenance of Loess and Red Clay on the Chinese Loess Plateau Using the U-Pb Dating and Single-size Zircon Size

作　　者：李云[1,2] 宋友桂[1] 聂军胜[3] 孙博亚[1,2] 

机构地区：[1]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,西安710075 [2]中国科学院大学,北京100049 [3]兰州大学西部环境与气候变化研究院,兰州730000

出　　处：《地质论评》2014年第2期380-388,共9页Geological Review

基　　金：国家重点基础研究规划项目973项目(2010CB833406和2013CB955904);国家自然科学基金(41290253);黄土与第四纪地质国家重点实验室资助的成果

摘　　要：中国黄土高原的风成沉积蕴含着丰富的大陆古气候和大气环流变化信息，但关于黄土和红粘土物源是否有变化目前仍存在着争论。近些年，锆石的LA-ICP—MS定年被广泛用于追踪沉积物来源，本文把碎屑锆石的u—Pb定年运用到红粘土中，并结合前人的数据和碎屑锆石粒径分析对黄土和红粘土物源进行了重新的讨论，认为黄土高原黄土碎屑锆石主要来源于黄土高原北部戈壁沙漠和附近的沙漠，极少量锆石来源于青藏高原北部，而不是主要来源于青藏高原北部和柴达木盆地，红粘土的锆石物源受近缘的基岩影响较大，朝那6．2—3．6Ma红粘土锆石碎屑部分来源于附近的六盘山。而且在0．12Ma、0．86Ma、1．25Ma之间，黄土碎屑锆石物源较稳定，存在少量变化，在2．6Ma和3．6Ma前后，黄土、红粘土碎屑锆石物源存在明显变化，这可能和全球变冷导致近地面冬季风增强有关。The loess--paleosol sequences of the Chinese Loess Plateau provide one of Earth＇s most complete and intensively studied terrestrial records of climate change. However, the following questions are still controversial issues： 1. Where is the eolian source of the loess？ 2. Is the provenance of the Quaternary loess different from the Tertiary Red Clay and does the provenance of the Quaternary alterative loess--paleosol sequences change？ Here we apply single-grain zircon U-Pb age data for red clay, coupled with some previous data and single-size zircon size to analyze the source of eolian deposits on the Chinese Loess Plateau. We conclude that the gobi （stony desert） in southern Mongolia and the adjoining gobi and sand deserts in China are the dominant source areas of the Loess Plateau, with a small portion coming from northern Tibetan Plateau, rather than mainly deriving from northern Tibetan Plateau and Qaidam Basin; the provenance of red clay is partly influenced by the close by bedrock, and zircon detrital of the Chaona red clay during 6. 2 ～ 3.6 Ma partly derive from the Liupan Shah. The provenances of loess around 0. 12 Ma, 0. 86 Ma and 1.25 Ma dont change obviously, but the provenances of loess and red clay deposited at 2. 6Ma and 3. 6Ma changes obviously.

关 键 词：洛川 朝那 LA—ICP—MS锆石U-Pb定年 黄土 红粘土物源 

分 类 号：P597.3[天文地球—地球化学] P531[天文地球—地质学]