论文部分内容阅读
最近在承德市北部地区发现了许多呈透镜状包体产于花岗片麻岩中的高压基性麻粒岩。运用全岩Ｓｍ －Ｎｄ、Ｒｂ－Ｓｒ、单颗粒锆石Ｕ－Ｐｂ 等多种同位素方法对这些高压麻粒岩进行了年代测定，得出了７个可供研究的年龄数据，即全岩Ｓｍ －Ｎｄ 等时线年龄２５５０±２１Ｍａ和３０６０±２．３Ｍａ，全岩Ｒｂ－Ｓｒ等时线年龄１５５０±３３Ｍａ 和１５６８Ｍａ，和单颗粒锆石Ｕ－Ｐｂ 同位素不一致线的上、下交点年龄分别为３４３２±５５６Ｍａ 和１８１７±１７Ｍａ， 颗粒锆石的谐和年龄１８３１±４ Ｍａ。在详细分析这些年代学数据可能的地质解释的基础上，认为该区的高压麻粒岩经历了复杂的地质演化过程，推测其原岩最早可能形成于新太古代早期至中太古代，并经受了太古宙末期花岗质岩浆侵入和变质作用改造。但其高压麻粒岩相变质很可能是古元古代末一次碰撞造山作用的产物， 最终进入上地壳可能在中元古代早期才完成， 与中元古代地壳的大规模拉张和燕辽裂陷槽的形成有关
Recently, a large number of high-pressure basic granulites in the granitic gneiss have been found in the northern part of Chengde City. The age of these high-pressure granulites was determined by using isotope methods such as whole rock Sm-Nd, Rb-Sr and single-grain zircon U-Pb, and seven age-related data were obtained, that is, whole rock Sm -Nd isochron age of 2550 ± 21Ma and 3060 ± 2.3Ma, the ages of the upper and lower nodes of Rb-Sr isochron age of 1550 ± 33Ma and 1568Ma in the whole rock and U-Pb isotope of single-granular zircon are 3432 ± 556Ma and 1817 ± 17Ma, and the zircon age of 1831 ± 4 Ma. Based on a detailed analysis of possible geologic interpretation of these geochronological data, it is considered that the high-pressure granulites in the area underwent complicated geological evolution, suggesting that the original rocks were probably formed as early as the Neo- Reconstruction of Invasion and Metamorphism of Late Archean Granitic Magma. However, the high-pressure granulite facies metamorphism is likely to be the product of the last collision orogeny in the Paleoproterozoic. The eventual entry into the upper crust may be completed in the early Middle Proterozoic, and the large-scale expansion of the Proterozoic crust and the Yanliao rift trough Formed about