摘要
单颗粒锆石的形态、颜色等特征记录了其母岩结晶过程的温度、压力、结晶介质的化学性质等信息,鉴定不同沙漠/沙地碎屑错石的晶体形态特征可以指示沉积物的原岩类型,进而可以帮助追溯物源。本文分析了中国北方塔克拉玛干沙漠、巴丹吉林沙漠、腾格里沙漠、毛乌素沙地、浑善达克沙地、科尔沁沙地等6个沙漠/沙地36个地表样品的碎屑锆石形态特征。结果显示,同一沙漠/沙地样品锆石形态特征较为一致,而不同沙漠/沙地样品锆石形态有差异。塔克拉玛干沙漠锆石多为无色或淡紫色,包裹体较少,锆石颗粒锥面较发育,短柱状锆石含量较多,指示该沙漠物质主要来自其北缘天山山脉早中生代碱性花岗岩。巴丹吉林沙漠和腾格里沙漠锆石形态特征较类似,相比较而言巴丹吉林沙漠锆石多为淡粉色,形态上锥面较发育,较少见到包裹体;而腾格里沙漠锆石颗粒细长柱较多和含包裹体颗粒较多,这两个沙漠物质可能来自其南部中央造山带的变质岩和其北缘中亚造山带早中生代碱性花岗岩。毛乌素沙地多为深色、锥面发育和短柱状颗粒锆石较常见,含包裹体颗粒较多,该沙地物质主要来自其西北孔兹岩带以及北部阴山山脉碱性花岗岩。浑善达克沙地锆石形态似毛乌素沙地,指示其物源与毛乌素沙地类似。科尔沁沙地锆石磨蚀严重,扁柱状锆石颗粒较常见,指示该沙地物质大部分来自其南缘燕山山脉的显生宙浅海沉积岩。本研究表明碎屑锆石形态特征可以指示沙漠或沙地沉积物的源区。
Deserts,sand fields,and Gobi deserts in Northern China are proposed as one of the most persistent sources of world wide wind-blown mineral dust, and also source of the aolian deposit in Chinese Loess Plateau. However, specific pathways and detailed area of dust have not been established yet. This paper contributes to this problem by investigating source areas of six major deserts and sand fields （Taklimakan desert, Badain Jaran desert, Tengger desert, Mu Us sand field, Otindag sand field, Horqin sand field）in Northern China. Here, zircon typology is introduced as a tool to trace the original orogenic belts or cratons for aeolian sediment since their shape is associated with the rock petrogenetic types. Long columnar zircons often come from magmatic rock, short columnar and columnar with well developed pyramids come from alkaline granites. Acidic granite zircons are always columnar, while sandstones produce flat columnar zircons. Thus, six types of zircon shape mentioned above are introduced to distinguish different rocks; five colors of the zircons are recognized（ colorless,light pink, pink,light purpl and purple）to identify relative ages of the rocks. Inclusion in zircon is also introduced to analyze rock metamorphism. Four orogenic belts and cratons are discussed in this study, the Tarim Craton, the Central Asian Orogenic System（CAOS） ,the Central Orogenic Belt（COB） and the North China Craton（NCC）. The Tarim Craton is widely distributed by Neoarchaean gneisses （TTG type granites and minor supracrustal rocks ）, and Proterozoic metamorphic rocks. The CAOS mainly consists of Early-Middle Triassic metaluminous-weakly peraluminous, calc-alkaline-high-K calc-alkaline or weak alkaline rocks and Late Triassic-Early Jurassic metaluminous-wealy peraluminum,high-K calc-alkaline or alkaline granites. The NCC is mainly covered by Early to Late Archean basement rocks. On the north of the NCC, the Yanshan Fold and Thrust Belt （YFTB） , is characterized by Late Triassic to Late Jurassic sandstones.
出处
《第四纪研究》
CAS
CSCD
北大核心
2013年第2期334-344,共11页
Quaternary Sciences
基金
国家自然科学基金项目(40930103
41021002和40902045)
中国科学院战略性先导科技专项项目(批准号:XDA05120704)共同资助
关键词
沙漠
沙地
物源
锆石
形态
分类
desert, sand field, sediment source, zircon, typology, classify
