| 中国大陆科学钻探工程的科学目标及初步成果 |
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| 引用本文： | 许志琴.中国大陆科学钻探工程的科学目标及初步成果[J].岩石学报,2004,20(1):1-8. |
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| 作者姓名： | 许志琴 |
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| 作者单位： | 中国地质科学院地质研究所,国土资源部大陆动力学实验室,北京,100037 |
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| 基金项目： | 中国大陆科学钻探工程,国家自然科学基金重大项目(40399141)，科技部973项目(2003CB716500)，973预研究项目(2001CCB00900)，国际合作项目(2002CB713900)，国土资源部科技专项(2002207)的资助 |
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| 摘 要： | 中国大陆科学钻探工程的主孔位于苏鲁超高压变质带南部的东海县，其穿过的岩石曾位于板块会聚边界的地幔深处，是研究大陆深俯冲及地幔动力学的最佳地区。中国大陆科学钻探的科学目标旨在通过对钻孔中获取的全部连续岩心、液态和气态样品及原位测井数据进行的全方位测量与综合研究，建立5000m孔深的各类多学科精细剖面，再造北中国板块与扬子板块会聚边界深部三维物质的组成和分布及三维结构构造；阐明板块会聚边缘的深部流体作用、壳一幔相互作用及地幔中物质循环和流变学；寻找超深地幔条件下形成的特征矿物，揭示超高压变质成矿机理；建立结晶岩地区地球物理理论模型和解释标尺；揭示超高压变质岩石的形成与折返模型及板块会聚边界的深部动力学机制。通过5km深孔营造的特殊地下空问，研究现代地壳的物理、化学及生物作用，并将建立亚洲第一个大陆科学钻探深孔长期观察实验站。中国大陆科学钻探工程已取得初步成果。主孔2000m岩心的深度和方位准确归位；建立了岩性、地球化学、构造、矿化、岩石物性、地下流体及各类测井等精细剖面；揭示了发现除超镁铁质岩外的各类岩石中的柯石英；通过SHRIMP测年准确确定超高压及退变质事件的年龄；初步揭示了超高压及退变质过程中流体的变化及水一岩作用；划分了构造岩片单元，确定了其边界的韧性剪切带性质，并发现早期构造信息；建立的随岩性变化的弹性波速度和热导率连续剖面对地震反射和热结构提供了岩石物性的制约；VSP地震剖面揭示了孔区深部的构造岩片结构，以及强地震反射层和大型韧性剪切带有关；发现地下特殊气体一甲烷、二氧化碳及氦气的异常，以及气体异常越往深部越频繁出现的规律。经DNA分析，在超高压岩心中发现在极端条件下形成的微生物。
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| 关 键 词： | 中国 大陆科学钻探工程 主孔 科学目标 初步进展 |
| 文章编号： | 1000-0569/2004/020(01)-0001-08 |
| 修稿时间： | 2003年11月30 |
The scientific goals and investigation progresscs of the Chinese Continental Scientific Drilling Project |
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| Xu ZQ.The scientific goals and investigation progresscs of the Chinese Continental Scientific Drilling Project[J].Acta Petrologica Sinica,2004,20(1):1-8. |
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| Authors: | Xu ZQ |
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| Abstract: | By employing modern deep drilling techniques, Chinese Continental Scientific Drilling Project ( CCSD ) is going to drill 5000 meter deep in Maobei, Donghai County, Jiangsu Province at the eastern part of Dabie-Sulu ultra-high pressure ( UHP) metamorphic belt. As a type example, results from such a deep drilling project will furnish key observational data to improve our understanding of a number of first-order important questions with regard to the physical and chemical processes that are responsible for the formation and evolution of UHP metamorphic terrains worldwide. The scientific objectives of this project are: (1) to reconstruct the 3-dimentional composition and structure of the root zone of the convergent boundary between North China plate and Yangtze plate; (2) to study mechanisms for deep mineralization, fluid circulation, crust-mantle interaction and recycle of crustal and mantle materials into the deep mantle; (3 ) to provide key mineralogical data to constrain the physical and mechanical properties of the upper mantle; (4) to formulate geophysical models and standards for better interpretation of geophysical data of crystalline rocks; (5) to determine the mechanism of formation and exhumation of Dabie-Sulu UHP terrane by integrating mineralogical, petrological, geochemical and structure data from hard rock, liquid, and gas samples taken from the borehole, together with in-situ logging data; (6) to study present-day physical, chemical and biological activities; and finally (7) to establish a deep laboratory for long-term observations.
The main borehole of CCSD has been drilled to the depth of 3600 m. A number of important investigations have been carried out, and as a result, we have made significant improvements in the understanding of the geochemical and geophysical nature of the root zone of the Dabie-Sulu UHP metamorphic belts. The drill core has recovered various rock types (e. g. UHP eclogite, gneiss, schist, quartzite, mylonite and garnet peridotite) and a number of tectono-petrological boundaries. Petrologic, geochemical, structural, mineralization, petrophysical, fluid and other logging profiles of the first 3600 m of the main borehole are established. The depth and orientation of cores are determined by the logging, core scanning, and petrography and structural geology studies. The coesite inclusions are found frequently in the gneisses, schists, amphibolites and eclogites from the drilling core. The protolith age, UHP peak metamorphic and amphibolite facies retrograde ages are determined by the SHRIMP U-Pb zircon dating. The reconstructed structure profile of the main borehole provides detailed and critical information with regard to the tectonic deformation of the root zone of the Dabie-Sulu UHP terrain. The elasticity wave and thermal conductivity profiles of the core provide important petrophysical constraints to the interpretation of the seismic reflection and geothermal data. The VSP seismic profile reveals the deep structure of the tectonic slices, and indicates a close relationships between the strong seismic reflection layers and large ductile shear zone. The intensity of CH4, C02 and He anomalies discovered in the borehole increases with depth. DNA analyses suggest that microbes living in extreme conditions present in the drilling cores. |
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| Keywords: | Chinese Continental Scientific Drilling Project ( CCSD) 5000m main hole Scientific goals Primary investigation progresses |
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