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祁连山高级变质岩系的形成时代至今尚未得到有效地限制.利用激光等离子体质谱(LA-ICPMS)对祁连山化隆群副片麻岩中的锆石及侵入于化隆群中弱片麻状花岗岩中的锆石进行了U-Pb定年,据此限定化隆群的形成时代.结果表明,化隆群副片麻岩中的碎屑锆石主要为岩浆成因类型,其~(207)Pb/~(206)Pb年龄主要集中于880~900Ma之间,加权平均年龄为(891±9)Ma,该年龄代表副片麻岩沉积物源区火成岩的岩浆结晶年龄,同时代表了化隆群形成时代的下限;弱片麻状花岗岩的自形岩浆锆石的207Pb/206Pb年加权平均年龄为(875±8)Ma,代表了化隆群形成时代的上限.因此,将化隆群的形成时代限定在875~891Ma之间.上述2个样品中的锆石U-Pb年龄还显示有1000~1700Ma的古老锆石,同时还显示有早古生代变质事件的年龄信息.锆石年龄结构反映了祁连山和柴达木北缘具有统一的地壳基底,并且表明祁连山基底具有扬子型块体的构造属性.结果还表明化隆群碎屑岩系是全球Rodinia超大陆聚合事件所导致的强烈造山作用,地壳快速隆升与剥蚀,并快速堆积的产物.
The forming age of the Qilian high-grade metamorphic rocks has not been effectively limited until now.Lacional laser plasma-mass spectrometry (LA-ICPMS) was used to analyze the zircons in the paragneiss of the Qilian Hehuaong Group and the intrusive granulites The results show that the detrital zircons in the Hualong paragneiss are mainly of magmatic origin and the ~ (207) Pb / The ages of ~ (206) Pb are mainly concentrated in the range of 880-900 Ma with a weighted average age of (891 ± 9) Ma, representing the age of magmatic crystallization of igneous rocks in the sedimentary source zone of paragneiss. The lower limit of the age. The annual average 207Pb / 206Pb zircon age of the intrusive magmatic zircons in the weak-gneissic granite is (875 ± 8) Ma, which represents the upper limit of the epoch-forming age Which is between 875 and 891Ma.The U-Pb zircon ages of the two samples also show ancient zircons of 1000 ~ 1700Ma and also show the age information of Early Paleozoic metamorphic events.The zircon age structure reflects the Qilian Mountains And the northern margin of the Qaidam have a uniform crustal basement, and indicate that the Qilian basement And the tectonic attributes of the Yangtze block.The results also show that the Huilong cluster clastic rocks are the products of intense orogeny, rapid uplift and erosion of the earth’s crust and rapid accumulation due to the supercontinent events over the world Rodinia.