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1.
糜棱岩化过程中矿物变形温度计 总被引：17，自引：0，他引：17
对有效确定中—低温下糜棱岩变形温度一直以来都没有比较理想的方法，而在研究韧性剪切带过程中对其变形温度的确定又常是必不可少的。根据近年来国际上对天然石英、长石、方解石等矿物变形的研究成果，总结了利用矿物变形指示变形温度的方法。在不同的温度条件下，长石与石英的变形方式具有阶段性，其变形与动态重结晶型式与温度具有明显的对应关系。石英变形中的滑移系及其C 轴组构图主要受变形温度的控制。低温变形中的方解石e 双晶纹形态也与温度呈密切的相关性。观测这些矿物变形的显微构造，可以很好地估计韧性剪切带糜棱岩化过程中的变形温度。 相似文献
2.
油气和含油气包裹体及其在油气地质地球化学研究中的意义 总被引：36，自引：3，他引：36
本文在综合前人研究的基础上，结合笔者的工作经验，提出了一个实用的油气和含油气包裹体分类方案，详细论述了各类油气和含油气包裹体的相态、组成和均一温度特征。在同一油气藏，均一温度越高，油相包裹体中的气态烃和挥发份的含量也越高。依据油相包裹体的均一温度的变化及其与同生水溶液包裹体的均一温度的关系可以研究油气藏在充填过程中油气组成，特别是气态烃和挥发份含量的演变。进而可以研究油气藏的油源--生油岩的类型和热演化程度。本文评述了依据油相包裹体和同生水溶液包裹体ＰＶＴ相图推断其捕获温度和压力范围的有效性和局限性。最后讨论了各类油气和含油气包裹体的成因机制及其在油气地质和地球化学研究中的意义。 相似文献
3.
Determining probable firing temperatures of daub recovered from archaeological sites provides opportunities to interpret the design and/or function of prehistoric structures. This paper critiques some of the methods for determining firing temperatures of daub, and presents a case study using samples from a secure depositional context at the Iron Age archaeological site of Noen U‐Loke, in northeast Thailand. Adopting a multimethod approach, the paper examines relationships between color, micro‐ and macro‐inclusions, elemental and mineralogical composition, physical form, and temperature, through the application of ICP‐MS, XRD analysis, magnetic susceptibility, and light microscopy. The important methodological point here is that the combined interpretation of independent measures provides a better estimate of the original firing temperatures of the archaeological material than has hitherto been possible. Initial examination implied that our samples were fired, in antiquity, at low temperatures, and concluded a nonindustrial source for the daub. We suggest that determining maximum temperatures for this original firing will provide the clearest discrimination between possible types of features (e.g., housing, kiln/furnace) from which the daub originally came. The results of our study indicate that the archaeological daub samples have been exposed to a range of temperatures from 200°C to 1000°C. It seems highly likely, therefore, that the daub was derived from a spatially complex structure, such as an industrial kiln or furnace, which has experienced a range of firing temperatures. © 2002 Wiley Periodicals, Inc. 相似文献
4.
热水沉积作用的研究已经历70余年,目前初步统一了热水沉积及其沉积岩的相关概念。按照形成矿物的温度和颜色特征及类型,将热水沉积作用分为白烟囱型和黑烟囱型,前者主要是在较低温度(100～320℃)下形成硅酸盐、硫酸盐等浅色矿物,后者主要在较高温度(320～400℃)下形成硫化物、氧化物等暗色矿物。大陆的热水沉积热液与海洋热液在温度与物理化学性质方面存在明显差异,大陆热水温度比海洋低,变化范围较海洋大;pH均值比海洋高,变化范围较海洋热水小;Na+K离子浓度与海洋接近,Ca离子与Cl离子浓度比海洋高,但它们的变化范围较海洋大。初步建立了一些关于热水沉积的沉积模式,如海底热液对流模式、盆地压实卤水对流模式、洋中脊岩浆热液—海水混合循环对流模式、热液溢流—喷流—溢流模式。由于热水沉积作用及热水沉积岩的分布具有特殊性和局限性,目前的研究程度较低,对热水沉积的化学过程和热力学过程、热流体成因、物质来源、热水沉积分异、热水沉积机理还不十分清楚,有待于进一步深入系统研究。 相似文献
5.
冰川内部温度与过去冰面温度变化密切相关,因此可以利用冰川钻孔温度对过去冰面温度变化过程进行重建。耦合的热传导-冰流物理模型与相关反演算法,是基于冰川钻孔温度进行古气候重建研究的理论基础和关键。论文收集了过去三十多年基于冰川钻孔温度进行古气候重建的研究文献,从冰川钻孔温度对气候变化的响应和古气候重建等方面进行了概述,并简要讨论了不同反演算法的优劣性和适用条件。尽管很多因素(如太阳辐射、融水等)都会对冰川钻孔温度造成影响,但两极或高纬地区的冷冰川钻孔温度能较好地反映气候变化历史。目前已通过这些不同地区的冰川钻孔温度,重建了末次冰期冰盛期以来不同时间尺度的气候变化历史,同时可与对应的冰芯记录相互印证。此外,通过冰川钻孔温度可以研究冰川与气温的耦合作用,并进一步预测冰川对未来气候变化的响应。利用中纬度冷冰川钻孔温度开展古气候重建的研究较少,未来加深这一方面的研究将有助于揭示中纬度高海拔地区的气候变化状况。 相似文献
6.
V. Magnien D.R. Neuville L. Cormier J.-L. Hazemann S. Pascarelli O. Pinet 《Geochimica et cosmochimica acta》2008,72(8):2157-2168
The kinetics and the mechanisms of iron redox reactions in molten Fe-bearing pyroxene compositions have been investigated by Raman spectroscopy and X-ray absorption Near Edge Structure (XANES) experiments at the iron K-edge. The former experiments have been made only near the glass transition whereas the latter have also been performed from about 1300 to 2100 K. The same kinetics are observed with both techniques. They are described by characteristic times that depend primarily on temperature and not on the initial redox state. At high temperatures, where both kinds of reactions could be investigated, these times are similar for oxidation and reduction. From these characteristic times we have calculated as a function of temperature and composition a parameter termed effective redox diffusivity. For a given melt, the diffusivities follow two distinct Arrhenius laws, which indicate that the mechanisms of the redox reaction are not the same near the glass transition and at high temperatures. As is now well established, diffusion of divalent cations is the dominant mechanism at low temperatures but the enhanced kinetics observed for alkali-bearing melts indicate that Li+ and Na+ also participate in ionic transport. At superliquidus temperatures, in contrast, diffusion of oxygen represents the dominant mechanism. 相似文献
7.
This paper deals with natural temperature records in the heavy (asphaltenes) and the light fractions (C7—light hydrocarbons) of petroleum. Two sets of marine oils formed from different source rocks and petroleum systems were studied using asphaltene kinetics and light hydrocarbon analysis. Both fractions have been reported to contain information about the temperature the respective oils have been exposed to in the subsurface. These indicated temperatures generally correspond to the conditions in the source rock when expulsion occurred. Bulk kinetic analysis of reservoir oil asphaltenes as well as light hydrocarbon (LH) analysis (of dimethylpentanes) were used here in order to evaluate the expulsion temperatures. Surprisingly, when considering information coming from both fractions, an inverse trend between LHs expulsion temperatures (Ctemp) and asphaltenes (Tasph.) can be observed—high Tasph (asphaltene temperatures) occur with low LH Ctemp (light hydrocarbon expulsion temperatures) and low Tasph can be observed when Ctemp is high. These differences are of fundamental importance for the use of such geochemical data in calibrating numerical basin models. The reason for this inverse behaviour is possibly due to the different expulsion behaviour of light hydrocarbons and the heavy fraction of oils, especially when the source rocks contain only moderate amounts of organic matter. In addition it has to be considered that the temperature predictions obtained using asphaltene kinetic analysis are related to the onset temperature of petroleum expulsion, while light hydrocarbons provide, at best, average expulsion temperatures. 相似文献
8.
Cs. Sajg 《Organic Geochemistry》2000,31(12)
Biological marker maturity parameters were used to estimate the minimum HC generation temperatures of crude oils from Eastern Hungary. More than 50 oils and oil shows were analysed. Molecular- and homologous-ratios of biological marker compounds (triterpanes, steranes, mono- and triaromatic steroid hydrocarbons) were used as maturation parameters. The oils have at least five maturity stages, i.e. they have been generated under different thermal conditions. The highest reservoir temperature in each group was chosen as the best estimate of the groups' temperature just below the generation temperature, i.e. reservoirs of the group might be expected to be at shallower depths (lower temperatures) than those of the generation zone due to vertical migration into pools. For each maturation level, a threshold temperature range for genesis was inferred from reservoir temperatures; they are from 130–135°C for the least mature oils to 210–215°C for the most mature oils. In the least mature oils cracking was not observed, hence carbon–carbon cracking reactions had not taken place during their genesis. The most mature oils are intensively cracked oils; they are almost condensates. Two major genetic groups (families) of oils were found in the area. Both are present in each maturation level. The effects of migration were checked, and no influence on maturation was found. A number of the oils are in overpressured reservoirs within, or just above, the zone of the present-day active oil generation, hence the present-day temperatures of the pools must have been maximum temperatures. Contrary to the traditionally accepted temperature range for petroleum generation–maturation reactions (50–150°C), there is strong evidence from this study that the onset of oil generation requires temperatures higher than 130°C and is still proceeding above 215°C. 相似文献
9.
A method of geochronology based on the chemical racemization of amino acids has been developed within the last few years. The various amino acids that make up the proteins of all living organisms consist virtually entirely of thel-enantiomer. After death, thel-enantiomer for each amino acid is slowly racemized over geological time and eventually forms an equilibrium mixture consisting of equal amounts of thed- andl-enantiometer. The increase in D/L ratio can be used to obtain a measure of the time that has elapsed since the organism died. The range of applicability of this method is the Pleistocene and may eventually be useful throughout the Pliocene in some cases. This paper presents a review of the literature on these applications as well as several suggested areas for future research.Unlike radionuclide decay rates, chemical reaction rates are sensitive to changes in such common environmental parameters as temperature, pH, solvent-medium, etc. For this reason, kinetic studies have been conducted at elevated temperatures in various “fossil-types” in order to simulate the changes that occur over long periods of time at the low temperatures found on the surface of the earth. Such studies, while of somewhat limited value for precise extrapolation, do nevertheless provide valuable information on which to base the theoretical concepts necessary for a complete understanding of the geochemical implications of the racemization reaction.Skeletal remains form the most suitable fossils for chronological study. Proteinaceous material is found embedded within the carbonate exoskeletons of invertebrates and the phosphatic endoskeletons of vertebrates. Most of the geochemical racemization studies have been conducted on foraminiferal shells and on bones. However, some work has also been reported on shells of other invertebrates, marine and lacustrine clays, and a few abiogenic concretions.Since the racemization reaction is temperature dependent, it has been used as a paleothermometer to estimate the average temperature to which bones and shells of independently known age have been exposed since their deposition. These average temperatures as a function of time have then been converted into estimates of the magnitude of the Holocene postglacial/Wisconsin glacial temperature change on land. They have also been used to obtain estimates of the “time-averaged” thermal gradient in deep-sea sediments using foraminifera isolated from the sediments. 相似文献
10.
Ye Cao Shengrong Li Meijuan Yao Huafeng Zhang 《Central European Journal of Geosciences》2010,2(4):433-440
Thermoluminescence (TL) of monomineralic separates have been widely used in various geosciences fields in order to trace the thermal history and aid in prospecting for gold deposits. Quartz is a ubiquitous mineral in the Shihu gold deposit, which is situated in the northern part of the Taihang orogenic belt in the North China craton (NCC). The deposit is hosted by ductile-brittle faults within an Archean metamorphic core complex of the Fuping Group. This deposit is characterized by gold-bearing quartz-polymetallic sulfides and quartz veins. New TL results have been obtained for quartz, in which four type-TL glow curves were identified. The gold-bearing quartz present type III glow curves that consist of two peak glow curves at the middle and high peak temperatures with the similar TL intensity. In addition, the cross-sections of peak temperatures and TL intensity highlight the valuable area where the Au-bearing quartz present weak TL intensity and low-middle peak temperatures. Our results significantly enhance the usefulness of quartz in metallogenic studies of the North China craton and as an indicator mineral in mineral exploration of the Taihang Mountain region. 相似文献
11.
The composition of waters from 10 thermal springs located in western Virginia near the 38th parallel lineament have been analysed for major dissolved components and for Sr, Fe, Cu, Zn and Cd; from these analyses, free ion activities have been calculated. The temperatures of the springs range from 17° to 39°C, the heat apparently being derived simply from deep circulation along synclinal, Middle Ordovician limestones. More than 95 per cent of the dissolved solids consist of Ca2+, Mg2+ HCO3?, and SO42?. The concentrations of these components, as well as the spring temperatures, have not changed appreciably in 140 yr in some springs. The waters that have temperatures below 25° are all undersaturated with respect to calcite and dolomite, possibly because they have been contaminated by shallow ground waters. The waters with temperatures above 25° are in equilibrium with calcite and dolomite. Furthermore, in this latter group, the calcium-sulfate activity product and the sulfate-carbonate activity ratio are nearly constant, even though the waters are under saturated with respect to gypsum, anhydrite, celestite and strontianite. This can be explained if CaSO4 is coprecipitated in a mineral such as aragonite. The waters have absorbed some dissolved oxygen near the surface, but at depth they may be anoxic with Eh controlled by the oxidation of pyrite to goethite. The extremely low chloride concentrations of these waters clearly distinguish them from the brines which deposited Mississippi Valley and Appalachian type epithermal ore deposits. 相似文献
12.
A REE-in-plagioclase-clinopyroxene thermometer has been developed on the basis of the temperature- and composition-dependent rare-earth element (REE) partitioning between coexisting plagioclase and clinopyroxene. This two-mineral exchange thermobarometer is constructed using parameters from lattice strain models for REE?+?Y partitioning in plagioclase and in clinopyroxene that were independently calibrated against experimentally determined mineral-melt partitioning data. An important advantage of this REE-based thermometer is that it can provide accurate temperatures through linear least-squares analysis of REE?+?Y as a group. Applications of the REE-in-plagioclase-clinopyroxene thermometer to volcanic and cumulate rocks show that temperatures derived from the new thermometer agree well with independently constrained magma crystallization temperatures, which adds confidence to applications of the REE-exchange thermometer to natural rocks with a wide spectrum of composition (i.e., from basalt to rhyolite). However, systematic temperature differences appear between the REE- and Mg-exchange thermometers for the volcanic and cumulate rocks. Through numerical simulations of diffusion in plagioclase-clinopyroxene systems, we demonstrate that (1) due to their slower diffusion rates, REE in minerals preferentially records crystallization or near-crystallization temperatures of the rock, and that (2) Mg is readily rest to lower temperatures for rocks from intermediately or slowly cooled magma bodies but records the initial crystallization temperatures of rocks from rapidly cooled magmas. Given their distinct diffusive responses to temperature changes, REE and Mg closure temperatures recorded by the two thermometers can be used in concert to study thermal and magmatic histories of plagioclase- and clinopyroxene-bearing rocks. 相似文献
13.
The clumped isotope composition of carbonates provides a new way to retrieve temperatures for ancient geological systems without knowing the isotopic compositions of co‐existing fluid/minerals. The application of this new thermometer in the past decade, however, has been largely restricted to low‐temperature (<~250 °C) geological processes. In this study, we present clumped isotope analyses for marbles collected from the Backbone Range of Taiwan, which has been subjected to greenschist facies metamorphism during the ongoing arc–continent collision. We find that the ∆47 temperatures either indicate temperatures of the last dynamic open‐system recrystallization of marbles due to tectonic movement/stress or signify closed‐system closure temperatures during rock exhumation, demonstrating that clumped information from marbles has great potential for revealing process characteristics during mountain building. 相似文献
14.
The miscibility gap between rhodonite and bustamite has been experimentally determined at temperatures between 600° and 1,100° C. For temperatures below 700° C the resulting limbs have been extrapolated on T-X-diagram as at such low temperatures equilibrium could not be attained. According to microprobe analyses for the natural assemblages of Ravinella di Sotto (Ivrea zone, Italy) and Broken Hill (N.S.W., Australia) equilibrium temperatures are estimated to be at 500° to 550° C. However these assemblages are thought to have re-equilibrated during cooling and the compositions of equilibrium assemblages are also pressure dependent. According to experiments and to molar volume data the rhodonite structure is stabilized by high pressures whereas bustamite by high temperatures. Based on available experimental results and natural data an isobaric T-X
Ca diagram and two isotherm
-X
Ca diagrams (for T=400° C and T=600° C) are given. 相似文献
15.
Empirical geothermometer dealing with Ti solubility in the Fe‐Mg biotites was originally proposed for biotites in graphitic, peraluminous metapelites containing ilmenite or rutile that equilibrated roughly at 4–6 kbar. Given that biotites are abundant in the porphyry copper systems, this geothermometer has frequently been used for the determination of magmatic–hydrothermal temperatures in the porphyry copper systems. Common associations of porphyry copper deposits (PCDs), that is, low Al content of biotite, biotite chloritization (causes the biotite to become more magnesian and to lose Ti), and biotite formation by amphibole replacement, as well as disequilibrium, local equilibrium, or re‐equilibration of biotites, especially through potassic alteration, may provide significant uncertainty in the temperatures estimated a by Ti‐in‐biotite geothermometer. In addition, besides the calibration range of thermometer for pressure (400–600 MPa), the temperatures of major sulfide precipitation in PCDs (>~400°C) does not fit with the temperature range of thermometer calibration (480–800°C). Worth noting, as confirmed by fluid inclusion data in the Sarkuh PCD, regardless of presence of mineralogical requirements, obtained temperatures of sulfide mineralization using Ti in biotite thermometer could be overestimated. This may be due to the difference between general conditions of sulfide mineralization and calibration range of Ti in the biotite thermometer for pressure and temperature, as well as the metaluminous nature of biotites in PCDs. 相似文献
16.
青藏高原与东西两侧大陆的气温差异 总被引：1，自引：1，他引：0
主要对我国昆仑山-秦岭以南的东西部气温的差异问题进行简要讨论。比较气象台站实测气温和换算至海面后的温度,明显反映西部、中部和东部3个地貌阶块的海面气温自西向东逐级降低。我国西部高原地区全年温度较东部丘陵平原区相对偏高,主要原因在于青藏高原和南亚次大陆主要为西南季风所控制,致使气温相对偏高,而东部深受东南季风和来自高纬冬季风的影响,气温相对偏低。因而,全球变化和区域性季风气候是导致东西部气温差异的主导原因,而不能笼统地归之为高原增温效应和东部"冷槽"影响所致。 相似文献
17.
Triaxial testing is being carried out on a mixture of Na-bentonite and sand to provide parameters for computer modelling of a nuclear-fuel waste disposal vault when the material is used as a sealant. Drained and undrained tests with porewater pressure measurement have been performed at confining pressures up to 6 MPa. The program is now being extended to 10 MPa and elevated temperatures.
In the long term, at room temperatures, it is predicted that the material will behave like a normally consolidated clay and strain harden plastically with increasing mean effective stress. In shear, its undrained strength will decrease slightly after failure. Working relationships, based on critical state soil mechanics, have been established for the normal consolidation and failure conditions of the material. The behaviour of the material in drained conditions can be predicted from these relationships. 相似文献
18.
Abstract A study has been made of the high-pressure early-Alpine re-equilibration in the eclogites and metasedimentary cover of the Val d'Ala di Lanzo ophiolite. All of the main high-pressure minerals have been analysed and their compositions used to determine re-equilibration temperatures. The minimum conditions proposed ( P = 1.3 GPa, T = 450–460°C) are also indicated by the presence of a jadeite+quartz-bearing metagranite.
The temperatures are compared with those reported for similar eclogites from the Voltri Group, the Aosta Valley and the Valais. Comparison of recalculated temperatures shows that the temperature (and probably the pressure) of the eclogitic re-equilibration increased in the Aosta Valley and the Valais, in keeping with what has been observed in the internal Penninic basement of the Gran Paradiso and Monte Rosa crystalline massifs. 相似文献
The temperatures are compared with those reported for similar eclogites from the Voltri Group, the Aosta Valley and the Valais. Comparison of recalculated temperatures shows that the temperature (and probably the pressure) of the eclogitic re-equilibration increased in the Aosta Valley and the Valais, in keeping with what has been observed in the internal Penninic basement of the Gran Paradiso and Monte Rosa crystalline massifs. 相似文献
19.
吕正祥 《沉积与特提斯地质》2003,23(3):106-109
笔者利用川西远源气藏中流体包裹体形成温度和成分信息等，得出大量对预测气藏有利的地质认识。包体温度表明储层建设性溶蚀作用发生于燕山晚期，气藏中的有利储层分布在燕山晚期构造高部位的有利微相砂体中；断裂、裂缝发育具多期性；气藏中的烃类流体信息反映出川西远源气藏成藏具有多期性。 相似文献
20.
《Quaternary Science Reviews》2003,22(8-9):915-923
We report evidence of deformation at sub-freezing temperatures beneath Hagafellsjökull-Eystri, an Icelandic surge-type glacier. The bed of a piedmont lobe that advanced during the 1999 surge comprises deformed blocks of glacier ice set within frozen sediment. This material has also been injected through overlying ice to form a network of crevasse-squeeze ridges. This layer contains evidence for two phases of deformation under contrasting rheological conditions: (1) deformation under relatively warm conditions, when the blocks of glacier ice acted as competent clasts within an unfrozen deforming matrix and (2) subsequent deformation at sub-freezing temperatures when the ice blocks were attenuated into the surrounding frozen matrix along fractures and planar shears enriched with excess ice. This suggests that the basal thermal regime of the advancing ice margin changed from warm-based to cold-based during the surge event. The persistence and potential prevalence of subglacial sediment deformation at sub-freezing temperatures has fundamental implications for our understanding of the dynamic behaviour, sediment flux and geomorphic ability of cold-based glaciers. 相似文献