Knowledge Resource Center for Ecological Environment in Arid Area
| 中国东部沙地物源示踪及地质意义 | |
| 其他题名 | Tracing the provenance of the Eastern China sandlands and its geological significance |
| 谢静 | |
| 出版年 | 2007 |
| 学位类型 | 博士 |
| 导师 | 丁仲礼 |
| 学位授予单位 | 中国科学院地质与地球物理研究所 |
| 中文摘要 | 重矿物组合、特征重矿物－石榴石、电气石化学组成、锆石U-Pb年龄和Hf同位素组成是非常有效的沉积物源区研究方法。通过这些方法的综合运用，可以给出沉积物源区的岩石组成、岩石结晶年龄和母源岩浆的地壳形成年龄的信息。从而，限定可能源区的位置和组成、估计不同源区的贡献程度。此外，为源区的岩浆、构造演化历史提供一些新的研究视角。\n本论文分析了呼伦贝尔、科尔沁和浑善达克沙地末次冰盛期(LGM)以来沙样和黄土样的重矿物组合、碎屑石榴石和电气石化学组成、锆石U-Pb年龄和Hf同位素组成。同时与蒙古中南部和塔里木中部沙样以及周围可能源区－中亚造山带和华北克拉通组成进行了对比。对它们的源区组成和中亚造山带构造演化模式得到了如下几点认识：\n1. 呼伦贝尔、科尔沁和浑善达克沙地具有相似的源区组成特征，它们的物质来源于中亚造山带和华北克拉通。华北克拉通对科尔沁和浑善达克沙地的贡献约为50%，对呼伦贝尔沙地的贡献较小，约为40%。\n2. 沙地外围的黄土与沙有相同的源区组成特征，暗示它们为同一风力搬运途径下物质分选的产物。\n3. 现代沙和LGM沙具有相同的源区组成特征，为现代沙是LGM沙翻新而成的论点提供一些直接的源区证据。\n4. 塔里木沙样与东部沙地的源区组成不同，排除了西部的塔克拉玛干沙漠作为东部三个沙地源区的可能性。\n5. 来源于中亚造山带的沙样的源区组成指示，中亚造山带中出露的太古代和古元古代变质基底岩石非常少，从新元古代末到中生代发生了连续的俯冲－增生事件。暗示中亚造山带是通过存在于岛弧和微陆块之间的弧前和弧后小洋盆的不断的碰撞－增生形成。碎屑锆石Hf同位素组成表明，中亚造山带显生宙以来有大量新生地幔物质加入。 |
| 英文摘要 | Heavy mineral assemblages, chemical compositions of diagnostic heavy minerals such as garnet and tourmaline, and U-Pb ages and Hf isotopic compositions of zircons are very effective means to determine sediment provenance. An integrated application of the above provides insight on the lithologies, crystallization ages and crustal formation ages of the parent magma of sediment source areas. As a result, the locations and characteristics of potential source areas can be constrained and contributions of different source regions may be evaluated. In addition, the study provides evidence for the magmatic and tectonic history of source areas using a novel approach.\nThe heavy mineral assemblages, and chemical compositions of detrital garnets and tourmalines, U-Pb ages and Hf isotopic compositions of zircons for sand and loess samples deposited since the Last Glacial Maximum (LGM) from the Hulunbeier, Keerqin and Hunshandake sandlands were analyzed and compared to those of central-southern Mongolia, the central Tarim and surrounding potential source areas, the Central Asian Orogenic Belt (CAOB) and North China Craton (NCC). The following remarks on provenance and tectonic history can be made:\n1. The source compositional characteristics of the Hulunbeier, Keerqin and Hunshandake sandlands are similar. They are derived from the CAOB and NCC whose contributions for the Keerqin and Hunshandake sandland are about 50%. For the Hulunbeier sandland it is somewhat less, about 40%.\n2. Loesses around of the sandlands have the identical source signiture as the sands, implying that they are sorted by the same wind regime.\n3. The source characteristics of the present and LGM sands are the same, providing direct evidence that the present sands originated from the reworking of LGM sands.\n4. The provenance characteristics of the three sandlands differ from those of the Tarim. As a result, the possibility that the three eastern sandlands were sourced from the Taklimakan desert can be ruled out.\n5. The source compositions of sand samples derived from the CAOB indicate that the occurrence of Archean and Paleoproterozoic metamorphic basement rocks is limited and continuous subduction-accretion events from the Neoproterozoic to the Mesozoic occurred. This implies that the CAOB is a orogenic collage belt similar to the present day southwest-Pacific, and formed by the amalgamation of small forearc and backarc ocean basins occurring between island arcs and microcontinents during continuous collision and accretion. The Hf isotopic signitures of detrital zircons indicate that large amounts of juvenile mantle materials were added to the CAOB crust during the Phanerozoic. |
| 中文关键词 | 呼伦贝尔 ; 科尔沁 ; 浑善达克 ; 源区 ; 重矿物 ; 锆石U-Pb年龄 ; Hf同位素组成 |
| 英文关键词 | Hulunbeier Hunshandake Keerqin provenance heavy minerals zircon U-Pb ages Hf isotopic composition |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地质与地球物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286548 |
| 推荐引用方式 GB/T 7714 | 谢静. 中国东部沙地物源示踪及地质意义[D]. 中国科学院地质与地球物理研究所,2007. |
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