福州复式岩体花岗岩年代学、地球化学及岩石成因

发布时间：2018-01-31 19:56

本文关键词： I-A型复合花岗岩年代学地球化学岩石成因福州复式岩体　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：华南沿海地区发育有大量的中生代花岗岩,虽然这是我国花岗岩研究程度较高的地区之一,但是对于该时期复式岩体的研究并不是很多,其岩石成因和构造背景一直存在较大争议。本文报道了福州复式岩体花岗岩的岩石学、锆石U-Pb年代学、锆石微量元素、Hf同位素和全岩主、微量地球化学的研究结果,试图为深入探讨该时期的岩石成因提供新资料。福州复式岩体的花岗岩主要分为钙碱性和碱性两大类,分别采自于福州岩体、丹阳岩体和魁岐岩体,岩石类型主要为:黑云母钾长花岗岩,二长花岗岩和碱性花岗岩。LA-ICP-MS锆石U-Pb定年结果表明:福州岩体和丹阳岩体形成的年龄约为:106 Ma和111 Ma、101Ma,是早白垩世多期次岩浆活动作用的产物;魁岐岩体形成的年龄为:93Ma、95Ma,是晚白垩世岩浆活动的产物。锆石微量的差异可以推断早白垩世钙碱性花岗岩为I型花岗岩,晚白垩世碱性花岗岩为A型花岗岩,构成了I-A型岩石系列。研究区内的岩石样品均具有Eu负异常、LREE富集和HREE亏损的特征,均显示Rb、Th、U、K、Pb等大离子亲石元素相对富集,Ba、Sr以及高场强元素Nb、Ta、P、Ti相对亏损。本文I型花岗岩的轻重稀土分馏程度较之A型花岗岩明显,LREE/HREE比值较大,A型花岗岩的负铕异常比I型花岗岩明显,同时也佐证了前面I-A型岩石系列的推测。锆石Hf同位素的结果表明,I型花岗岩的εHf(t)值由负到正,地壳模式年龄表明花岗质岩浆源岩来自于新元古代古老地壳的部分熔融,并有少量的地幔组分卷入。A型花岗岩样品εHf(t)值为正,地壳模式年龄指示花岗质岩浆源岩来自于新元古代古老地壳的部分熔融,并有大量幔源组分的混入。福州复式岩体中I-A型花岗岩具有相同的源区,其形成的差异主要是构造环境的变迁、幔源岩浆的加入以及岩浆分异演化多种因素综合作用的结果。
[Abstract]:There are a large number of Mesozoic granites developed in the coastal areas of South China. Although this is one of the areas with a high degree of granite research in China, there are not many studies on the composite rock mass in this period. The petrology, zircon U-Pb geochronology, zircon trace element HF isotope and the whole rock host of the complex granites in Fuzhou are reported in this paper. The results of trace geochemistry try to provide new data for the further study of the petrogenesis of this period. The granites of Fuzhou complex rock body are mainly divided into two types: calc-alkaline and alkaline, which were collected from Fuzhou rock body respectively. Danyang and Qui-qi rock bodies, the main rock types are: biotite potassium feldspar granite. The zircon U-Pb dating results of the monzogranites and alkaline granites show that the ages of formation of Fuzhou and Danyang pluton are about 10 ~ 106 Ma and 111 Ma. 101 Ma was the product of multistage magmatism in early Cretaceous; The age of formation of Kui-qi rock body is: 93 Ma-95 Ma, which is the product of late Cretaceous magmatic activity. The difference of trace zircon can be inferred that the early Cretaceous calc-alkaline granite is I-type granite. The late Cretaceous alkaline granites are A-type granites, forming I-A type rock series. The samples in the study area are characterized by negative EU anomaly LREE enrichment and HREE depletion, indicating RB. The large ion lithophile elements such as Th _ (+) U _ (U) K _ (+) Pb are relatively enriched in Ba-Ba _ (Sr) and the high field strength element (NB ~ (+) Ta _ (P)). The REE / hree ratio of the I-type granite is larger than that of the A-type granite, and the negative europium anomaly of the A-type granite is more obvious than that of the I-type granite. The results of zircon HF isotopes indicate that the 蔚 Hft values of the I-A type granites vary from negative to positive. The crustal model age indicates that the granitic magmatic source rocks originated from the partial melting of the Neoproterozoic ancient crust, and a small amount of mantle components are involved in the sample of .A-type granite. The crustal model age indicates that the granitic magmatic source rocks are derived from the partial melting of the Neoproterozoic ancient crust and are mixed with a large number of mantle-derived components. The I-A type granites in the Fuzhou complex have the same source area. The difference of formation is mainly caused by the changes of tectonic environment, the addition of mantle magma and the comprehensive action of many factors of magmatic differentiation and evolution.
【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】：2015
【分类号】：P588.121

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