论文部分内容阅读
提供了从西秦岭6个钾霞橄黄长岩岩筒中分离出的金云母单矿物的40Ar/39Ar同位素定年数据,确定甘肃西秦岭新生代钾霞橄黄长岩的喷发时限主体集中在22~23Ma之间,结合对青藏高原及其周边地区新生代火山岩同位素年代学资料的综合分析,论证了金云母单矿物的40Ar/39Ar同位素定年的地质意义,指出甘肃西秦岭钾霞橄黄长岩与高原及其周边地区其他新生代钾质-超钾质火山岩一样,属于后碰撞火山作用产物.西秦岭新生代火山岩的喷发时代与冈底斯带钾质火山岩的喷发时间有部分重叠,因此西秦岭新生代火山作用是紧随高原腹地之后,后碰撞火山作用向高原东北方向迁移的反映.同位素定年数据不仅进一步证明青藏高原后碰撞火山作用具有时空迁移特征,而且也为探讨和研究西秦岭地区自新近纪以来地质构造演化的深部动力学背景和机制提供了同位素年代学约束.
The 40Ar / 39Ar dating data of phlogopite single minerals isolated from six Karst volcanic plutons in West Qinling are provided. The main eruption time of Neoproterozoic Kaxiasu palaeohigh fossils in West Qinling of Gansu is between 22 and 23 Ma, Combined with the geochronological data of the Cenozoic volcanic rocks in the Qinghai-Tibet Plateau and its surrounding areas, the geologic significance of 40Ar / 39Ar isotopic dating of phlogopite is demonstrated. It is pointed out that the Kashi Xia olivine fossils in the western Qinling Mountains of Gansu and other parts of the plateau and surrounding areas The Cenozoic potassic-ultra-potassic volcanic rocks belong to the post-collisional volcanism, and the eruption ages of the Cenozoic volcanic rocks in the West Qinling Mountains partially overlap with the eruption time of the Potassium-type volcanic rocks in the Gangdise Zone. Therefore, the Cenozoic volcanism of the West Qinling is tight After the plateau in the hinterland, the post-collision volcanism migrated to the northeast of the plateau.Isotopic dating data not only further prove that the post-collision volcanism in the Qinghai-Tibet Plateau has the characteristics of space-time migration, but also to explore and study the West Qinling since the Neolithic evolution of the geological structure The deep kinetic backgrounds and mechanisms provide isotopic chronological constraints.