云南大莲花山和卓潘岩体岩浆源区及形成机制

发布时间：2018-08-05 19:39

【摘要】：本文以大莲花山富碱斑岩和卓潘碱性杂岩体为研究对象,通过岩石学、岩相学、岩石地球化学、锆石U-Pb年代学和Hf同位素等研究方法,探讨碱性侵入体的岩浆源区、形成过程及大地构造环境。研究取得如下主要认识:(1)大莲花山和卓潘岩体具有富碱高钾,准铝质-弱过铝质特征,富集大离子亲石元素和轻稀土元素,显著亏损Ta、Nb、Ti、P等高场强元素,具有弱的负Eu异常,两者均为钾玄岩系列。两岩体普遍亏损Ti、Nb、Ta,表明两者岩浆源区均具有板片俯冲脱水交代形成富集岩石圈地幔特征。(2)大莲花山富碱(斑)岩体角闪石英二长斑岩U-Pb年龄为34±0.4Ma,黑云二长岩锆石U-Pb年龄为33±0.3Ma。卓潘岩体正长岩锆石U-Pb年龄为33±0.4Ma,辉长岩锆石U-Pb年龄为34±0.3Ma。厘定了兰坪盆地富碱斑岩的主要岩浆活动时限为37~33Ma。(3)大莲花山锆石Hf同位素?Hf(t)值介于-1.1~+8.9之间,以正值为主,表明岩浆主要来自于地幔,有少量地壳物质的贡献。卓潘岩体锆石Hf同位素?Hf(t)值介于-4.3~-10.6之间,表明源区物质主要来自下地壳。(4)解析岩浆形成过程和大地环境:中元古代大洋板块双向俯冲形成交代富集的大陆岩石圈地幔,同时地壳加厚形成新生的下地壳。始新世末,由于拆沉作用减压,金沙江-红河走滑断裂带的应力状态由压剪切转变为张剪切,形成大莲花山富碱斑岩和卓潘碱性杂岩体。
[Abstract]:In this paper, the alkaline porphyry and the Zhuopan alkaline complex in Dalianhuashan are studied. The magma source area of the alkaline intrusive body is discussed by means of petrology, petrography, petrochemistry, zircon U-Pb chronology and HF isotope. Formation process and tectonic environment. The main results are as follows: (1) the Dalianhuashan and Zhuopan intrusions are characterized by rich alkali and high potassium, quasi-aluminum-weak peraluminous elements, enrichment of large ion lithophile elements and light rare earth elements, significant depletion of high field strength elements such as Tahlang NbTiTiP and weak negative EU anomalies. Both belong to the series of kaliacite. The results show that both magmatic source regions are characterized by plate subduction dehydration and metasomatism to form enriched lithospheric mantle. (2) the U-Pb age of hornblende quartz monzogranite is 34 卤0.4 Ma. and the zircon U-Pb age is 33 卤0.3 Ma. in the alkali rich (porphyry) body of Dalianhuashan. The zircon U-Pb age of the syenite and pyroxenite is 33 卤0.4 Ma and 34 卤0.3 Ma, respectively. The main magmatic activity time of alkali rich porphyry in Lanping basin is determined to be 37 ~ 33 Ma. (3) the HF (t) value of zircon from Dalianhuashan is between -1.1 ~ 8.9, which is mainly positive, indicating that the magma is mainly derived from the mantle and contributed by a small amount of crustal material. The HF (t) values of zircon HF isotopes in the Zhuopan rock body range from -4.3 to 10.6, indicating that the source material mainly comes from the lower crust. (4) Analytic magmatic formation process and geoenvironment: Mesoproterozoic oceanic plate subducted bidirectionally to form metasomatic enriched continental lithospheric mantle. At the same time, the crust is thickened to form the new lower crust. At the end of Eocene, the stress state of the Jinshajiang-Honghe strike-slip fault zone changed from compressive shear to tensional shear due to decompression, forming the Dalianhuashan alkali-rich porphyry and Zhuopan alkaline complex.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P587

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