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辽河盆地东部凹陷的粗面斑岩呈次火山相顺层侵入于早第三纪沙河街组地层中,全岩Rb＿Sr等时线年龄为(41.5±2.2)Ma粗面斑岩呈斑状构造,斑晶为钾长石、歪长石和少量斜长石,基质主要为碱性长石.地球化学研究表明,粗面斑岩的SiO2含量变化于59.58(wt%)到61.22(wt%),(K2O+Na2O)介于10.40(wt%)到11.83(wt%)之间,富集高场强元素(如Nb、Th、Zr和Hf)和轻稀土元素,亏损Pb.除具明显的Eu负异常,粗面斑岩的稀土元素配分型式与伴生玄武岩的相似.以上特征表明,粗面斑岩是玄武岩浆直接分异演化的结果,地壳物质的混染作用不显著.此外,粗面斑岩亏损Sr、Eu、K和Rb,其K/Rb和Rb、Eu 和ΣREE分别呈线性相关,表明斜长石和钾长石的分离结晶作用对粗面质岩浆的演化起重要作用.我们认为这种粗面质岩石是玄武质岩浆在低压环境(≤1.0GPa)下经历大比例的分离结晶作用形成,而斜长石和钾长石的分离结晶作用发生超低压(约100MPa)条件下,这与本区沙三期相对稳定的大陆裂谷拉张环境相一致.
The rough porphyry in the eastern sag of Liaohe Basin intruded into the Lower Tertiary Shahejie Formation strata, and the Rb_Sr isochron age of the whole rock was (41.5 ± 2.2) Ma. The results show that the SiO2 content of the rough porphyry varies from 59.58 (wt%) to 61.22 (wt%), (K2O + Na2O) ranged from 10.40 (wt%) to 11.83 (wt%), enriched in high-field elements such as Nb, Th, Zr and Hf and depleted in light rare- , And the REE patterns of the coarse-grained porphyries are similar to those of the associated basalts.The above characteristics show that the rough porphyry is the result of the direct differential evolution of basaltic magmas, and the mixing of the crustal material is insignificant.In addition, Sr, Eu, K and Rb, the K / Rb and Rb, Eu and ΣREE are linearly correlated respectively, indicating that the separation crystallization of plagioclase and K- feldspar plays an important role in the evolution of the facies magma. Paleomagmatism is that the basaltic magma undergoes large-scale segregation and crystallization under low-pressure environment (≤1.0GPa), while the separation crystallization of plagioclase and K-feldspar Under the conditions of ultra-low pressure (about 100 MPa), this is consistent with the relatively stable continental rift tension environment in the third phase of the Shahejie Formation.