【作者】 龙晓平；

【导师】 金巍；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2004， 硕士

【摘要】 本次研究依托中国地质调查局“中国中西部前寒武纪重大地质事件群及全球构造意义”项目的二级课题“昆仑山前寒武纪重大地质事件年代格架及东、西昆仑对比”。通过野外路线剖面及局部地质填图，在东昆仑造山带金水口及邻近典型地区采集岩石样品数百件，并分选出锆石颗粒样品 20 余件。通过对这些地区锆石样品系统矿物学、内部结构及微区成因研究，总结出了该区岩浆成因锆石和变质成因锆石的各自特征。据此，讨论了锆石微区成因对锆石 U-Pb测年结果地质解释的制约关系。在锆石 U-Pb 测年结果地质解释的基础上，得到了东昆仑金水口及邻区部分重要地质体的形成时代或变质时代，为东昆仑造山带年代学研究提供了一些高质量的数据，并建立起金水口地区前泥盆纪地质事件格架，将该地区地质演化划分出三个主要阶段。此外，通过重要样品的地球化学研究，对金水口地区重点变质岩系的原岩建造和重要岩体的成因及形成的构造背景，作了有益的探讨。这无论是对东昆仑基础地质研究，还是对探讨东昆仑地质演化，都有重要意义。通过本次研究，获得了一些重要的数据和认识：1）结合前人研究成果，认为金水口地区的层状岩系金水口群白沙河岩组原岩为泥质沉积岩、镁质碳酸盐及基性火山岩建造，为角闪岩相－麻粒岩相变质，其原岩形成于比较稳定的大陆边缘环境。2）东昆仑造山带金水口地区锆石类型主要为岩浆成因锆石和变质成因锆石，其区分标志比较明显。该区岩浆成因锆石微区阴极发光图象颜色明亮，多发育振荡环带，其 Raman 谱线背景值较高，Th/U 比值一般>0.1。而变质成因的锆石微区，其 Raman 谱线背景值很低，阴极发光图像颜色较暗，无振荡环带，Th/U 比值<0.1。结合拉曼光谱及阴极发光等方法，可以有效地区分这些岩 第 I 页 共 1 页<WP=115>中 英 文 摘 要浆成因锆石和变质成因锆石。此外，金水口地区变质成因锆石常见：继承锆石、变质锆石、深熔锆石和变质增生锆石，其特征不尽相同。 3）地球化学研究表明，金水口花岗岩中黑云母花岗闪长岩为 I 型花岗岩类岩石，而金水口石榴堇青石黑云母花岗岩、片麻状黑云母花岗岩、石榴黑云母二长花岗岩等富铝花岗岩显示典型的 S－型花岗岩特征。该区 I－型花岗岩类岩石可能是闪长质岩浆同化混染富铝的上地壳物质的结果，而 S－型花岗岩类岩石则为高区域热流情况下，上地壳富铝物质重熔的结果。这两类花岗岩类岩石可能形成于火山弧构造环境下。 4）金水口地区及邻近地区相关锆石年代学研究表明，该区可以划分出四期岩浆事件和三期变质事件。 一．岩浆事件 Ⅰ格林维尔期基性岩浆事件 该期岩浆事件以金水口变辉长岩体为代表， SHRIMP 分析锆石 U-Pb 同位素年龄为 1239.4Ma。 Ⅱ晋宁期中酸性岩浆事件 该期岩浆事件以清水泉片麻状花岗岩及金水口含石榴花岗闪长岩为代表，颗粒锆石 U-Pb 等时线年龄为 835.6～868Ma。 Ⅲ晚加里东期中酸性岩浆事件 该期岩浆事件以天台山鸡爪/条带状黑云母花岗岩、金水口黑云母二长花岗岩、金水口（含）石榴红柱堇青黑云母花岗岩及白日其利沟花岗闪长岩为代表，SHRIMP 分析锆石 U-Pb 同位素年龄为369～403Ma。 Ⅳ海西－印支期中酸性岩浆事件 该期岩浆事件以天台山黑云母二长花岗岩～金水口角闪花岗闪长岩为代表，SHRIMP 分析锆石 U-Pb 同位素年龄为230～236Ma。该期岩浆事件在白日其利沟地区表现为基性辉长岩，其 SHRIMP分析锆石 U-Pb 同位素年龄为 241.8Ma。 二．变质事件 Ⅰ早－中元古代角闪岩相变质事件 该期变质事件以金水口群白沙河组 第 II 页 共 7 页<WP=116>吉 林 大 学 硕士学位论文变质岩系为代表。 Ⅱ早古生代角闪岩相－麻粒岩相变质事件 该期变质事件以金水口及白日其利沟矽线石榴片麻岩为代表，其变质时限为 425~460Ma。 Ⅲ早古生代末期角闪岩相－麻粒岩相变质事件 该期变质事件以金水口及天台山地区的麻粒岩和矽线石榴片麻岩为代表，其变质时限为 346～391.6Ma。 5）通过对金水口地区岩浆事件和变质事件的研究，结合前人对东昆仑该地区及邻区的研究成果，可以将金水口地区前泥盆纪地质演化划分为三个阶段：早期地壳演化阶段、新元古代造山阶段及早古生代末造山阶段。更多还原

【Abstract】 This study bases on the subjection of The China Geological Survey: ThePrecambrian Important Geological Events Sequence of Kunlun Mountain and TheContrasting between West Kunlun and East Kunlun, which belongs to thesubjection: The Group of Precambrian Important Events in Midwest in China andits Globle Tectonic Significances. There are several hundrends Samples of rocksand more than 20 samples of zircon grains collected in Jinshuikou and its adjacentzone, East Kunlun Orogenic Belt, during the field route section and the localgeologic mapping. By the researches of system mineralogy and interior structureand chronology of zircon in these zones, the characteristics of magmatic zircons andmetamorphic zircons have been summarized. According to these characteristics, therestricted relationships between the characteristics of zircon and the geologicalinterpretions of the U-Pb dating datum of zircon are discussed. Based on thegeological interpretations of the U-Pb dating datum of zircon, the formation timeand the metamorphic age of some important geologic bodies have been obtained inJinshuikou and its adjacent zone, East Kunlun. These studies have offered somevery credible datum for the chronologic research of East Kunlun Orogene Belt andestablished the geological events sequence of Jinshuikou zone before Devonian.According to which, the geologic evolvement in this area can be divided into threemajor stages. Moreover, based on the research of geochemistry, the source rockassemblages of the important metamorphic rocks, the genesis and tectonic settingsof key magmatic bodies in Jinshuikou zone have been discussed. There are veryimportant significances not only in the researches of basic geology, but in thediscussions of geologic evolvement in East Kunlun. 第 IV 页 共 7 页<WP=118>吉 林 大 学 硕士学位论文 Therefore, some basic cognitions can be achieved: 1. Taken the past research fruits into account, the source rocks of BaishaheFormation of Jinshuikou Group, bedded formation in Jinshuikou Zone, areargillaceous sedimentary rock, magnesian carbonate and basic volcanic rock, whichbelong to amphibolite-granulite faces. It is shown that this formation has formed inrelatively stable continental edge. 2. U-Pb isotopic dating of zircon is a common and comparatively crediblechronological method in orogenic belt. The interpretations of its analyzed resultsdepend on the studies of the interior structure and micro genesis of zircon. Thestudies of the interior structures of zircon shown that there are two geneticclassifications of zircon in orogenic belt: magmatic zircon and metamorphic zircon,whose differences are obvious. The magmatic zircon always has oscillatory zoneand rather high background of Raman spectrum. In this kind of zircons, the microcathode luminescence is rather bright and the ratio of Th/U is less than 0.1. On theother hand, the metamorphic zircon has rather low background of Raman spectrum.In the kind of zircons, the micro cathode luminescence is rather dark and the ratioof Th/U is more than 0.1. The studies of the interior structures of zircon indicatethat Raman spectrum and cathode luminescence are an efficient method todistinguish the two genetic classifications of zircon. Furthmore, there are inheritedzircon, metamorphic zircon, anatectic zircon and metamorphic overgrowth zircon inJinshuikou Zone, whose characteristics are different. 3. The research of geochemical shows that biotite granodiorite in Jinshuikou isI-type granite, but garnet cordierite biotite granite, geneissic biotite granite andgarnet biotite monzonitic granite show the characteristics of S-type granite. TheI-type granites may be the result of assimilating and contaminating alliticsupracrustal material by diorite-magma. But the S-type granites are the result ofanatexis of allitic supracrustal material in high regional heat flux. These two typesof granites may have更多还原