云南大理地区九顶山和宝丰寺富碱斑岩的年代学与地球化学

发布时间：2018-04-11 06:36

本文选题：富碱斑岩 + 地球化学特征　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：青藏高原东南缘,沿印度板块与欧亚板块碰撞边界的金沙江—哀牢山大断裂附近,分布着一条NW走向富碱斑岩带。近年来由该带内发现了大量与富碱斑岩具有密切成因联系的铜金钼矿床,众多学者也对该带的富碱斑岩的成因机制做了相关研究。本文选择大理地区的九顶山和宝丰寺岩体为研究区,通过LA-ICP-MS锆石U-Pb定年法测得九顶山岩体的二长斑岩年龄为35.3±0.2Ma(MSWD=0.43),宝丰寺岩体的二长斑岩年龄为35.6±0.2Ma(MSWD=0.36)。九顶山岩体和宝丰寺岩体富碱斑岩地球化学特征表明:岩石显示高K2O、高Na2O,和强烈富碱特征,属高钾钙碱性—钾玄岩系列,显示过铝质特征(A/CNK=0.79~1.28)。岩石强烈富集轻稀土元素,轻重稀土分馏明显((La/Yb)N=8.38~55.50),显示轻微的Eu负异常(δEu=0.61~0.82),富集大离子亲石元素(Rb、Th、U、K),亏损高场强元素,并显示“TNT”异常。研究区内的富碱斑岩与云南三江地区大规模岩浆作用的同时性和地球化学特征相似,反映它们在构造背景、物质来源和成岩机制上的联系。区域构造演化与岩石地球化学特征表明,成岩的岩浆活动与印度板块和欧亚板块的碰撞产生的左行走滑有关。研究区内的样品属C型埃达克岩,其富碱岩浆起源于加厚下地壳的熔融作用,并有地幔物质的加入,经历了较为显著的壳幔岩浆混合的作用。
[Abstract]:In the southeastern margin of the Qinghai-Tibet Plateau, near the Jinshajiang-Ailaoshan fault along the collision boundary between the Indian plate and the Eurasian plate, there is an alkali-rich porphyry belt with NW strike.In recent years, a large number of copper-gold-molybdenum deposits closely related to alkali-rich porphyry have been found in this zone, and many scholars have also studied the genetic mechanism of alkali-rich porphyry in this zone.In this paper, Jiudingshan and Baofengsi pluton in Dali area are selected as the study area. The age of the second length porphyry of the Jiudingshan rock body is 35.3 卤0.2 Ma-MSWDU 0.433.The age of the second length porphyry is 35.6 卤0.2MaMSWD0.3636 by LA-ICP-MS zircon U-Pb dating method.The geochemical characteristics of alkali-rich porphyry rocks in Jiudingshan and Baofengsi pluton show that the rocks are characterized by high K _ 2O, high Na _ 2O and strong alkali-rich, and belong to the high-potassium calc-alkaline _ potash series, showing the characteristics of analuminite (A / CNK _ (0.79) 0.79 ~ (1.28)).The rocks are strongly enriched in light rare earth elements (LREE), and the fractionation of LREE shows a slight negative EU anomaly (未 EU0.61 ~ 0.82), enrichment of the large ion lithophile element RbPe, depletion of high field strength elements, and "TNT" anomaly.The alkali-rich porphyry in the study area is similar to the large-scale magmatism and geochemical characteristics in Sanjiang area, Yunnan Province, reflecting their relationship in tectonic setting, material source and diagenetic mechanism.The regional tectonic evolution and petrogeochemical characteristics indicate that diagenetic magmatic activity is related to the left strike-slip caused by the collision between the Indian plate and the Eurasian plate.The samples in the study area belong to the C type adakite. The alkali-rich magma originated from the melting process of thickened lower crust, with the addition of mantle material, and experienced a relatively significant mixing of crust and mantle magma.
【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】：P597.3;P588.15

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