Petrography and uplift history of the Quaternary Takidani Granodiorite: could it have hosted a supercritical (HDR) geothermal reservoir?     

Masatoshi Bando  Greg Bignall  Kotaro Sekine  Noriyoshi Tsuchiya   《Journal of Volcanology and Geothermal Research》2003,120(3-4):215-234

The Quaternary Takidani Granodiorite (Japan Alps) is analogous to the type of deep-seated (3–5 km deep) intrusive-hosted fracture network system that might support (supercritical) hot dry/wet rock (HDR/HWR) energy extraction. The I-type Takidani Granodiorite comprises: porphyritic granodiorite, porphyritic granite, biotite-hornblende granodiorite, hornblende-biotite granodiorite, biotite-hornblende granite and biotite granite facies; the intrusion has a reverse chemical zonation, characterized by >70 wt% SiO₂ at its inferred margin and <67 wt% SiO₂ at the core. Fluid inclusion evidence indicates that fractured Takidani Granodiorite at one time hosted a liquid-dominated, convective hydrothermal system, with <380°C, low-salinity reservoir fluids at hydrostatic (mesothermal) pressure conditions. ‘Healed’ microfractures also trapped >600°C, hypersaline (35 wt% NaCl_eq) fluids of magmatic origin, with inferred minimum pressures of formation being 600–750 bar, which corresponds to fluid entrapment at 2.4–3.0 km depth. Al-in-hornblende geobarometry indicates that hornblende crystallization occurred at about 1.45 Ma (7.7–9.4 km depth) in the (marginal) eastern Takidani Granodiorite, but later (at 1.25 Ma) and shallower (6.5–7.0 km) near the core of the intrusion. The average rate of uplift across the Takidani Granodiorite from the time of hornblende crystallization has been 5.1–5.9 mm/yr (although uplift was about 7.5 mm/yr prior to 1.2 Ma), which is faster than average uplift rates in the Japan Alps (3 mm/yr during the last 2 million years). A temperature–depth–time window, when the Takidani Granodiorite had potential to host an HDR system, would have been when the internal temperature of the intrusive was cooling from 500°C to 400°C. Taking into account the initial (7.5 mm/yr) rate of uplift and effects of erosion, an optimal temperature–time–depth window is proposed: for 500°C at 1.54–1.57 Ma and 5.2±0.9 km (drilling) depth; and 400°C at 1.36–1.38 Ma and 3.3±0.8 km (drilling) depth, which is within the capabilities of modern drilling technologies, and similar to measured temperature–depth profiles in other active hydrothermal systems (e.g. at Kakkonda, Japan).  相似文献   

Evaluation of predictors of non‐linear seismic demands using ‘fishbone’ models of SMRF buildings     

Nicolas Luco  Yasuhiro Mori  Yosuke Funahashi  C. Allin Cornell  Masayoshi Nakashima 《地震工程与结构动力学》2003,32(14):2267-2288

Predictors (or estimates) of seismic structural demands that are less computationally time‐consuming than non‐linear dynamic analysis can be useful for structural performance assessment and for design. In this paper, we evaluate the bias and precision of predictors that make use of, at most, (i) elastic modal vibration properties of the given structure, (ii) the results of a non‐linear static pushover analysis of the structure, and (iii) elastic and inelastic single‐degree‐of‐freedom time‐history analyses for the specified ground motion record. The main predictor of interest is an extension of first‐mode elastic spectral acceleration that additionally takes into account both the second‐mode contribution to (elastic) structural response and the effects of inelasticity. This predictor is evaluated with respect to non‐linear dynamic analysis results for ‘fishbone’ models of steel moment‐resisting frame (SMRF) buildings. The relatively small number of degrees of freedom for each fishbone model allows us to consider several short‐to‐long period buildings and numerous near‐ and far‐field earthquake ground motions of interest in both Japan and the U.S. Before doing so, though, we verify that estimates of the bias and precision of the predictor obtained using fishbone models are effectively equivalent to those based on typical ‘full‐frame’ models of the same buildings. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

试论碳酸盐岩上覆红土的形成模式及演化趋势   总被引：14，自引：1，他引：14  

符必昌  黄英 《地质科学》2003,38(1):128-136

据长期对岩溶及红土化作用等的研究成果,本文全面系统地分析了碳酸盐岩上覆红土的形成及演化规律,提出了一个新的碳酸盐岩上覆红土的形成模式,进而深入阐明了碳酸盐岩上覆红土的演化规律及其在现代气候条件下的演化趋势等,在解决岩溶及红土学术界存在的碳酸盐岩上覆红土的形成、碳酸盐岩与上覆红土之间的相互关系及其发展演化规律等一系列重大疑难问题上向前迈进了一步,对相关学科的发展将产生积极的推动作用.  相似文献   

辽河盆地东部凹陷热历史及构造—热演化特征   总被引：9，自引：5，他引：9  

王永新  汪集旸  胡圣标 《地质科学》2003,38(2):214-220

根据辽河盆地东部凹陷大地热流测量和镜质体反射率数据,恢复了该区的热历史,结果表明:东部凹陷热流呈现古热流高现今热流低的变化特征,沙河街组三段沉积期到东营组沉积期(距今43～25Ma)盆地热流为66～82mWm²,现今热流值为47～70mWm²。构造沉降史分析显示,盆地经历了早期的裂谷阶段(距今43～25Ma)和后期的热沉降阶段,裂谷阶段包含了两个裂谷亚旋回。盆地现今较低的大地热流和较高的古热流及典型的裂谷型构造沉降样式为东部凹陷的构造—热演化提供了重要认识。  相似文献   

A high precision U–Pb age of metamorphic rutile in coesite-bearing eclogite from the Dabie Mountains in central China: a new constraint on the cooling history     

Qiuli Li  Shuguang Li  Yong-Fei Zheng  Huimin Li  Hans Joachim Massonne  Qingchen Wang 《Chemical Geology》2003,200(3-4):255-265

This paper first reports a high precision U–Pb age of 218±1.2 Ma for rutile in coesite-bearing eclogite from Jinheqiao in the Dabie Mounteins, east–central China. This work shows that the U–Pb mineral (rutile+omphacite) isochron age of 218±2.5 Ma and conventional rutile U–Pb concordia age of 218±1.2 Ma obtained by common Pb correction based on the Pb isotopic composition of omphacite in the same eclogite sample are consistent, proving that the omphacite with low U/Pb ratio (μ=2.8) can be used for common Pb correction in U–Pb dating of rutile. Oxygen isotope analysis of rutile aliquots gave the consistent δ¹⁸O values of −6.1±0.1%, demonstrating oxygen isotope homogenization in the rutile of different grains as inclusion in garnet and grain in matrix. Oxygen isotope thermometry yields temperatures of 695±35 and 460±15 °C for quartz–garnet and quartz–rutile pairs, respectively. These oxygen isotopic observations suggest that the diffusion of oxygen in rutile as inclusion in garnet is not controlled by garnet. According to field-based thermochronological studies of rutile, an estimate of the T_c of about 460 °C for U–Pb system in rutile under rapid cooling conditions (20 °C/Ma) was advised. Based on this U–Pb age as well as the reported chronological data with their corresponding metamorphic and/or closure temperature, an improved T–t path has been constructed. The T–t path confirms that the UHPM rocks in South Dabie experienced a rapid cooling following the peak metamorphism before 220 Ma and a long isothermal stage from 213 to 180 Ma around 425 °C.  相似文献   

The postglacial history of three Picea species in New England, USA     

Matts Lindbladh  George L Jacobson Jr.Molly Schauffler 《Quaternary Research》2003,59(1):61-69

Given the difficulty of separating the three Picea species—P. glauca, P. mariana, and P. rubens (white, black, and red spruce)—in the pollen record, little is known about their unique histories in eastern North America following deglaciation. Here we report the first use of a classification tree analysis (CART) to distinguish pollen grains of these species. It was successfully applied to fossil pollen from eight sites in Maine and one in Massachusetts. We focused on the late glacial/early Holocene (14,000 to 8000 cal yr B.P.) and the late Holocene (1400 cal yr B.P. to present)—the two key periods since deglaciation when Picea has been abundant in the region. The result shows a shift from a Picea forest of P. glauca and P. mariana in the late glacial to a forest of P. rubens and P. mariana in the late Holocene. The small number of P. rubens grains identified from the late glacial/early Holocene samples (<5%) suggests that that species was either absent or rare at most of the sites. The occurrence and distribution of the three species do not reveal any geographic or temporal trend during late glacial time, but the data suggest that they were distributed in local patches on the landscape. The results of this study indicate that the recent population expansion of Picea (1000 to 500 cal yr B.P.) was likely the first time since deglaciation that P. rubens was abundant in the region.  相似文献   

台湾恒春半岛的隆起珊瑚礁台地          下载免费PDF全文

王鑫 《第四纪研究》1997,17(4):327-332

台湾本岛南端的恒春半岛,出露隆起珊瑚礁石灰岩和现代珊瑚礁海岸。隆起珊瑚礁石灰岩在地貌上的表现是多阶的台地。最高的公园面可达海拔300m,依次向下,是海拔约100～160m的笼仔埔面,海拔70～80m的埔顶面以及海拔10～20m的垦丁面。在恒春半岛的西侧,珊瑚礁台地面已经倾斜,因此高度的表现不同。ESR及¹⁴C定年表明,抬升的更新世珊瑚礁台地形成于0.5Ma B.P.前后及0.13Ma B.P.两时期;海拔10～20m的全新世珊瑚礁台地约形成于6 000a B.P.的时期。这些证据显示了地质时期里全球变迁的蛛丝马迹。  相似文献   

超积累植物与找矿   总被引：13，自引：0，他引：13  

唐世荣  黄昌勇  朱祖祥 《物探与化探》1997,21(4):263-268

本文介绍了超积累植物的概念和它在地质找矿中的意义,回顾了国外超积累植物的研究历史,并对应用超积累植物进行找矿的发展方向进行了讨论。  相似文献   

Numerical models of mantle convection with secular cooling     

Wanda DeLandro-Clarke  Gary T. Jarvis 《Geophysical Journal International》1997,129(1):183-193

A 2-D time-dependent finite-difference numerical model is used to investigate the thermal character and evolution of a convecting layer which is cooling as it convects. Two basic cooling modes are considered: in the first, both upper and lower boundaries are cooled at the same rate, while maintaining the same temperature difference across the layer; in the second, the lower boundary temperature decreases with time while the upper boundary temperature is fixed at 0°C. The first cooling mode simulates the effects of internal heating while the second simulates planetary cooling as mantle convection extracts heat from, and thereby cools, the Earth's core. The mathematical analogue between the effects of cooling and internal heating is verified for finite-amplitude convection. It is found that after an initial transient period the central core of a steady but vigorous convection cell cools at a constant rate which is governed by the rate of cooling of the boundaries and the viscosity structure of the layer. For upper-mantle models the transient stage lasts for about 30 per cent of the age of the Earth, while for the whole mantle it lasts for longer than the age of the Earth. Consequently, in our models the bulk cooling of the mantle lags behind the cooling of the core-mantle boundary. Models with temperature-dependent viscosity are found to cool in the same manner as models with depth-dependent viscosity; the rate of cooling is controlled primarily by the horizontally averaged variation of viscosity with depth. If the Earth's mantle cools in a similar fashion, secular cooling of the planet may be insensitive to lateral variations of viscosity.  相似文献   

Book Reviews     

《The Professional geographer》1997,49(2):257-268

Committee on Protection and Management of Pacific Northwest Anadromous Salmonids Upstream: Salmon and Society in the Pacific Northwest Cook, Ian G; Doel, Marcus A. and Li, Rex (eds.) Fragmented Asia: Regional Integration and National Disintegration in Pacific Asia Crush, Jonathan Power of Development de Blij, H. J., and Muller, Peter O. Physical Geography of the Global Environment Hayward, David J. International Trade and Regional Economies: The Impacts of European Integration on the United States Kennedy, Michael The Global Positioning System and GIS: An Introduction Lowe, Philip; Marsden, Terry and Whatmore, Sarah (eds) Regulating Agriculture Marsden, Terry; Lowe, Philip and Whatmore, Sarah (eds) Labour and Locality: Uneven Development and the Rural Labour Process Marsden, Terry; Lowe, Philip and Whatmore, Sarah (eds) Rural Restructuring: Global Processes and Their Responses Whatmore, Sarah; Marsden, Terry and Lowe, Philip (eds) Gender and Rurality Whatmore, Sarah; Marsden, Terry and Lowe, Philip (eds) Rural Enterprise: Shifting Perspectives on Small-Scale Production Martopo, Sugeng and Mitchell, Bruce (eds) Bali: Balancing Environment, Economy and Culture Ould-Mey, Mohameden Global Restructuring and Peripheral States: The Carrot and the Stick in Mauritania Redclift, Michael and Benton, Ted (eds) Social Theory and the Global Environment Thomas–Slayter, Barbara and Rocheleau, Dianne Gender, Environment, and Development in Kenya: A Grassroots Perspective Wallach, Bret Losing Asia: Modernization and the Culture of Development Wennberg, John E. Dartmouth Atlas of Health Care Wilson, David and Huff, James O. (eds) Marginalized Places and Populations: A Structurationist Agenda  相似文献