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应用激光40Ar/39Ar同位素定年方法,对北祁连九个泉绿帘石蓝片岩和硬柱石蓝片岩中的蓝闪石和白云母单矿物进行了多颗粒一次性熔蚀的40Ar/39Ar同位素年龄测定,所获得的硬柱石蓝片岩40Ar/39Ar等时线年龄为(413±5)Ma,绿帘石蓝片岩40Ar/39Ar等时线年龄为(415±7)Ma.结合变质作用峰期温压条件计算,区域大地构造背景分析,413～415Ma的年龄应代表北祁连低温蓝片岩带由硬柱石蓝片岩相向绿帘石蓝片岩相转化的递进变质作用年代的下限.该研究进一步表明,北祁连山九个泉硬柱石蓝片岩可能是在冷俯冲带中角流作用下形成的,代表了古祁连山洋残留洋盆最后闭合的时间,即华北板块和柴达木板块聚合在一起的时代.
Using the 40Ar / 39Ar isotope dating method of laser, 40Ar / 39Ar isotopic dating of one-time multi-grain eroded samples of glaucophane and muscovite single minerals in the Jiguenchuan Epikelite and dacite blue schist from the North Qilian Mountains , The 40Ar / 39Ar isochron age of (413 ± 5) Ma and the 40Ar / 39Ar isochron age of Epicatechischist schist (415 ± 7) Ma are obtained. The combination of metamorphism and peak temperature and pressure According to the analysis of tectonic setting and regional tectonic setting, the age of 413 ~ 415Ma should represent the lower limit of the age of metamorphism of the conversion from dacite blue-lithofacies facies to epidote blue-lithofacies facies in the low-temperature blue lithofacies belt in the North Qilian.The study further shows that, The Jiuquan hydrotallar schist in the northern Qilian Mountains may be formed by the mid-stream flow in the cold subduction zone, representing the last closure time of the remnant oceanic basins in the ancient Qilian Mountains, that is, the time when the North China plate and the Qaidam plate converge together.