【作者】 侯广顺；

【导师】 韩吟文；

【作者基本信息】 中国地质大学 ， 地球化学， 2003， 硕士

【摘要】 图形是信息的重要载体形式。相对于地质学、地球物理学在GGT计划中的密切合作及相对成熟的区域研究成果编图来说，区域地球化学的系统研究及区域编图还处于探索之中。秦岭-大别造山带是目前已有较好的地球化学研究基础，又是国土资源部“岩石圈三维化学结构研究”项目重点研究地区。论文在该地区进行了造山带地球化学编图的探索，对造山带及邻区地壳化学结构及地球化学分区进行了研究。具体内容包括以下几个方面。1、造山带地球化学编图的理论探讨。目前常见的编图类型大致可以分成两种：一种是以模式化定义来对区域编图要素进行划分，另一种是基于模型化的单指标场的时空分布。两者分别以地质学和地球物理学图件为代表。相对于地球物理学及地球化学场的概念，目前尚难以进行地球化学编图。作者认为：地球化学图件应能够反映造山带的岩石圈地幔性质、区域地壳的生长、演化和构造归属及同位素年代学等内容。笔者尝试提出用Ln(Co*Ni*Cr)、Nb/Ta、铅同位素、钕同位素二阶段亏损地幔模式年龄（T2DM）及εNd(t)等地球化学指标表达以上信息，并在相应的章节对指标进行了理论介绍。2、秦岭-大别造山带地壳化学结构。在对比地质学、地球物理学关于地壳结构研究的基础上，提出了地壳化学结构的概念。通过引进地球化学参考模型地壳不同结构层的元素丰度，根据元素壳内分异特征，提出用大陆地壳整体标准化方法对地壳化学结构进行研究。秦岭-大别造山带的地壳化学结构研究表明：造山带地壳总体上具有分异较弱、地壳演化成熟度较低的特点；太古代基底太华群、崆岭群和大别群都不能代表完整的下地壳组成，下地壳下部可能没有出露。并且，大别群经历了复杂的构造熟化过程；南秦岭和扬子陆块北缘西段的中地壳很大程度上受岩浆底侵的影响，而壳内调整作用不明显。用Ln(Co*Ni*Cr)、Nb/Ta、及针对花岗岩体的KN/A指标的编图是地壳化学结构在平面图上的反映。编图结果显示：Ln(Co*Ni*Cr)指标可以较好地表达地壳不同结构层的演化成熟度情况；Nb/Ta指标对于示踪沉积盖层的源区不太明显；花岗岩类的KN/A指标与通过地壳化学结构得出的结论完全相同，可以反映区域地壳基底的演化成熟度。3、造山带同位素地球化学分区。通过不同块体共计784套铅同位素资料的统计信息，详细描述了不同块体的铅同位素组成特征，并根据基底特征进行了块体划分。华北陆块基底具有低放射成因铅同位素组成。北秦岭构造带至北淮阳构造构造带，显示本研究区较高的放射成因的铅同位素组成。南秦岭构造带部分和扬子陆块北缘显示分段现象。南秦岭与北秦岭相比，显示较贫U铅的特点，而Th铅则相差不大。大别地区北大别单元显示与华北地块南缘相似的206Pb/204Pb和207Pb/204Pb比值，但是，比华北南缘具有较高的208Pb/204Pb值，而与南秦岭相似；南大别主体的超高压单元则完全可以与南秦岭东段相对比，指示了大别地块是南秦岭的东延部分。在630多套Sm-Nd同位素资料统计的基础上，造山带的Sm-Nd同位素体系显示：1、造山带的地壳物质组成复杂，同位素组成具有自亏损地幔至大陆上地壳变化的趋势，说明造山带强烈壳-幔相互作用的动力学特征。2、143Nd/144Nd与w(Sm)/w(Nd)及<WP=6>147Sm/144Nd的正相关关系明显，说明壳内阶段的143Nd/144Nd同位素组成应该进行二阶段校正。钕同位素二阶段亏损地幔模式年龄填图表明：华北陆块北缘整体上是在太古代基底上生长而来；北秦岭与南秦岭构造带都存在较明显的早元古代和中、晚元古代增生期，只是南秦岭含有少量太古代基底；南、北大别的增生期相同：都存在少量的太古代基底信息，早、中元古代是主增生期，同时，存在少量新元古代增生。扬子陆块北缘存在太古代基底，其规模也可能较大，中、新元古代地壳增生也很明显。4、在综合前人及本文研究的基础上，提出了两点新认识：北淮阳可能相当于北秦岭构造带的东延部分，并且向南发生了逆冲推覆；大别地区中、新元古代的地壳增生物质源区可能与耀岭河群的源区相同，都是1.0Ga左右的岩浆底侵在中下地壳的物质。更多还原

【Abstract】 Map is important media to express information. By comparition with the intimate cooperation of geology and geophysics studies in GGT program and their relatively mature regional mapping citrtion, systemic regional geochemistry research and mapping is still in exploring. Qinling-Dabie Orogen,the mainly part of central orogenic belt of China,is chosen as the subjiect region. This disseration probes to the orogenic geochemical mapping and makes a study of the continental crust chemical structure and geochemical subdivision. The detail as follows:1. Disscusion of orogenic geochemical mapping in theory.Present map can be divided into two types: one is the division of map elements as the assumpsit model,and the other is the onefold field temporal-spatial strength determined by special pattern, geological map and geophysical map as the sample respectively.Until now, to make geechemical map as the field pattern is difficult.The author thinks that geochemical map should express the lithosphere mantle character, regional crust growth, geotectonic ascription and chronlogy dates et. al.,. We chose Ln(Co*Cr*Ni), Nb/Ta, plumbum isotopes composition, neodymium isotope two stage model age of depleted mantle (T2DM) andεNd(t) indexs to express the information and give the introduction of theory in the relevant chapters.2. Continental crust chemical structure of Qinling-Dabie Orogen. This disseration brings forward the continental crust chemical structure concept after comparing with geological and geophysical concepts concerning the different aspects of crust’s samdwich structure. Elements abundence of continental crust different layers provided by Geochemical Earth Reference Model (GERM) are used to give the way to standard the continent crust. This way’s key point is the comparability of different elements which shows the continent crust chemical differenation. Research of continental crust chemical structure shows: crustal differation of Qinling-Dabie orogen is weak; Taihua group and Kongling group, the basements of the adjacent zones, can only represent the upper lower crust; the Dabie group ,basement of the South Qining block, may have experienced complex structural maturation process; the middle crust of South Qinling Block and western part of Yangtze carton north margin may be dominanted by upplanting and consequently the crust differation is unobvious. Ln(Co*Ni*Cr),Nb/Ta and KN/A about granites indexs are used to make in the ichnography to express continental crust chemical stucture. Mapping results shows that Ln(Co*Ni*Cr)can indicate the maturality character of different curst layers; KN/A on regional granites can disclose the basement maturality character;but Nb/Ta can’t indicate the source of sediment cover well.3. Isotopic geochemistry subdivision. On the statistical rusults of 784 collected samples’<WP=8>lead isotopic composition dates, different blocks’ character are described and blocks’ geotectonic ascription are disscused. South margin of North China carton has lower 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values as a whole. North Qinling-Noth Huaiyang belt has bigger 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values. South Qinling block is depleted in U plumbum isotopes by comparison with North Qinling belt, but they have almost the same 208Pb/204Pb limits, and this indicates they both have the enrichment of Th. North Dabie block’ 206Pb/204Pb is alike to that of North China carton, but its 208Pb/204Pb is similar to that of South Qinling Block, bigger than North China carton’s 208Pb/204Pb. The ultra-high perssure metamorphism unit, mainly part of South Dabie block, has almost the same lead isotopes composition as South Qinling block. This indicates that the Dabie block may be the eastern externed part of Souther Qinling Block. Statistic of about 630 Sm-Nd isotopic dates from Qinling-Dabie Orogen shows: 1. mass in this area is complex, Sm-Nd isotopic system has the tendency of changing from depleted mantle to upper continental crust. This is consistent with the intense crust-mantle interaction更多还原