地质通报Issue(2)：251-261,11.
西藏达如错地区晚侏罗世高镁安山岩--班公湖-怒江洋壳俯冲消减的证据
The Late Jurassic high-Mg andesites in the Daru Tso area, Tibet：Evidence for the subduction of the Bangong Co-Nujiang River oceanic lithosphere
摘要
Abstract
This paper reports zircon U-Pb and Hf isotopic data of major and trace elements for the andesites of Jienu Group from the Daru Tso area in the northern Lhasa block. LA-ICP-MS U-Pb zircon analyses suggest that the andesite were formed at 163.3 ± 1.7Ma, and that the volcanic rocks were formed in early Late Jurassic period. Geochemical studies show Daru Tso andesites have typi⁃cal geochemical characteristics similar to the high-Mg andesite (HMA). They are characterized by high MgO content, Mg # values, and low TFeO/MgO ratios. They are enriched in LREE in the chondrite-normalized REE patterns with negative Eu anomalies, and are enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs). Zircon εHf(t) values are from-8.5 to-6.7. Geochemical features of the Daru Tso high-Mg andesites are considered to have been generated by the subduc⁃tion of Bangong Co-Nujiang River oceanic lithosphere, and can be genetically regarded as resulting from partial melting of subduc⁃tion sediment melts that had been metasomatized by mantle peridotite under the condition of oceanic crust subduction. They were formed at the tectonic setting of the active continental margin (Andeans-type) associated with Bangong Co-Nujiang River oceanic crust subduction. It is therefore held that the Late Jurassic Jienu Group volcanic rocks in the Daru Tso area are the products of subduc⁃ tion of the Bangong Co-Nujiang River oceanic lithosphere. These results provide direct evidence of the volcanic rocks for the sub⁃duction of the Bangong Co-Nujiang River Tethys Ocean.关键词
高镁安山岩/俯冲沉积物熔融/班公湖-怒江结合带/LA-ICP-MS锆石U-Pb定年/锆石Hf同位素Key words
high-Mg andesites/subduction sediment melts/Bangong Co-Nujiang River suture zone/LA-ICP-MS zircon U-Pb dating/zircon Hf isotope分类
天文与地球科学引用本文复制引用
李小波,王保弟,刘函,王立全,陈莉..西藏达如错地区晚侏罗世高镁安山岩--班公湖-怒江洋壳俯冲消减的证据[J].地质通报,2015,(2):251-261,11.基金项目
四川省基金项目（编号2014JQ0025）、国家自然科学基金项目（批准号41303028）和中国地质调查局项目 （）
