【作者】 林清茶；

【导师】 夏斌；

【作者基本信息】 中国科学院研究生院（广州地球化学研究所） ， 构造地质学， 2007， 博士

【摘要】 碱性岩：典型的碱性岩为硅不饱和，出现霞石、白榴石等似长石类矿物。在十九世纪九十年代就将碱性岩分为大西洋型的钠质碱性岩和地中海型的钾质碱性岩，到二十世纪九十年代将碱性岩分为超基性碱性岩、基性碱性岩、中性碱性岩和碱性岩。碱性岩物质来源较深，主要源自上地幔，形成于岩石圈拉张环境，是深部地球动力学过程在浅部地壳的直接表现和历史记录，因此对碱性岩的研究是探索地球深部物质组成、物理化学环境、地壳上层构造和深部动力学过程的一个重要途径。碱性岩是除幔源岩石包体外另一类可提供地幔信息的岩石，是窥探地幔的窗口。本文的研究范围是哀牢山-金沙江钾质碱性岩带，该带位于我国西南三江地区的扬子板块和中缅板块三江褶皱区间的缝合带和多个地体边界带，由喜马拉雅期钾质富碱岩浆岩组成；从北往南由新疆塔什库尔干→沱沱河沿→青海囊谦→西藏江达→云南剑川→下关，向南到金平，中国境内该岩带延长达3700km，且向南延至越南境内，平面上岩带呈反“S”形的线形分布特点。如此年轻的巨型钾质碱性岩带，主要由暗霞正长岩、霞辉岩、等色岩、透辉石正长岩、角闪石正长岩、透辉石花岗岩、石英二长岩、二长花岗斑岩、钾长花岗斑岩、碱长花岗斑岩、云煌岩、煌斑岩、含镁铝榴石橄榄碱煌岩、碱性玄武岩、安粗岩和粗面岩等组成。组成这些钾质碱性岩带的岩石：在岩相上，包括深成相、浅成相和喷溢相等不同岩相；在岩性上，从超基性、基性、中性到酸性岩石；造岩矿物，从超基性到酸性岩石中均有透辉石，在基性、超基性岩中有霞石；在岩石化学成分上，所有岩石均表现出富碱高钾富钙，微量元素富集Rb、Sr、Ba等大离子亲石元素和Th、U等放射性元素，贫Nb、Ta、Zr、Hf等高场强元素；稀土元素富集轻稀土，铕负异常不明显；Sr、Nd、Pb同位素组成，显示了物质来源于富集地幔源区。年龄测量结果表明：东部金平-剑川地区锆石SHRIMP U-Pb年龄范围38Ma-34Ma，西部巴毛穷宗-羊湖-泉水沟-昝坎等Ar-Ar年龄范围44Ma-6Ma，显示哀牢山-金沙江钾质碱性岩浆岩带的岩浆作用东早西晚；岩带从南到北(邦达错-羊湖-阿鲁克库勒)年龄由大到小(44Ma-16Ma-0.4Ma)，显示新生代的岩浆作用由老到新的变化。其中最早的岩浆作用的时间是38Ma，相当于始新世晚期，其控岩断裂构造形成时间晚于印度与欧亚两大陆在始新世中期(45Ma)碰撞的时间。这种因果关系，反映了青藏高原在两个大陆碰撞之后继续向北偏东(21°)推移，受到了塔里木、柴达木和康滇古陆古老基底的阻挡，导致了长达数千公里的金沙江-红河走滑拉分带的形成，同时伴随着钾质碱性深成岩和火山岩产出。该岩带钾质碱性岩浆作用，始于始新世中期(44Ma)到更新世(0.37Ma)，岩浆作用时间长达40Ma之多。这一现象与印度、欧亚两大陆碰撞时间在50Ma-45Ma至今是一致的。结合地质构造、地球物理、矿物岩石学、地球化学、成矿和年代学等资料，本论文对哀牢山-金沙江钾质碱性岩带性质等进行详细论述。更多还原

【Abstract】 The alkali rocks include potassic alkali rocks and natric alkali rocks. And in the 19 century alkali rocks are often associated with Pacific style natric alkali rocks and mediterranean style potassic alkaic rocks. They were usually generated in deep-large-fault zone and closely connected with basic/ultra basic rocks in space. Therefore, alkali-rock is of significance in tectonic petrology. The researching area that is Ailaoshan-Jinshajiang potassic alkalic rock zone lies in the southwest of China. The zone lies at the joint of Yangtze plate and Zhongmian plate in Sanjiang fold series and many rocks’ borderlines. It is composed of Himalaya period potassic alkalic magmatic rock. The zone is 3700 kilometres. The rock belt are composed of malignite, nepheline gabbro, shonkinite, diopside-sienite, hornblende sienite, amphibole-monzonite,granodiorite-granophyre, kaligranite-porphyry, fraidronite, kersanton, precious garnet, olivine alkali-lamprophyre, alkalic-pyroxenolite, alkalic-basalt, latite and trachyte. And the lithofacies of the potassic rock zone include plutonic intrusion, hypabyssal intrusion and eruption.The lithologic characters about the rock zone include ultra basic rocks, basic rocks, neutral rocks and acidic rocks, but the characters of all rocks are alkali. The bigest character is that the content of kalium is more than the natrium. The rock forming mineral of all rocks has diopside, and the nepheline is in the ultra basic rocks and basic rocks. The characters of geochemistry are rich alkali. And at the same time the content of calcium is high. They are rich in alkali, high in Potassium, enriched in LILE, LREE and Pb, depleted in HFSE and have a small Sr, Nd, Pb isotope range. Their source is probably a kind of even metasomatic mantle. This is consistent with the fact that there is kimberlite containing flogopite in the deep-source enclosure of Cenozoic super-K alkali lava in the southern part of this rock zone.The Zircon SHRIMP dating results of 36.8Ma, 36.8Ma, 34.1Ma, 38.3Ma yielded about the rocks in the south belt. This result is in late Eocene and belongs to Himalaya period. The rock-controlling structure of this rockmass may form before 40 Ma, much earlier than 45Ma-the collision time. At the same time the Ar-Ar and K-Ar dating results of 44Ma-0.37Ma yielded about the rocks in the north belt. The time shows the evolvement history and time of volcanic action about the North Tibet. And it reflects that the magmatism time of Ailaoshan-Jinshajiang potassic alkalic rock zone from east is younger than west magmatism time. The time is from the middle of Eocene to Miocene. The durative time of magmatism is 40Ma. This phenomenon is consistent with that about the collision between Europe slab and Asia slab. It hints that the cause of formation is inherent contact with the collision. Studying the information about geological structure, physical geography, mineral petrology, geochemistry, mineral and chronology, we know that the magma of this rock zone is originated from the partly melting of relatively shallower spinel mantle.更多还原