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991.
992.
临沧锗矿含碳硅质灰岩的成因及其与锗成矿的关系 总被引:5,自引:1,他引:5
临沧锗矿是我国近年发现的具有独立开采价值且接近超大型规模的锗矿床,其富锗含煤段中存在薄层含碳硅质灰岩,深入研究含碳硅质灰岩的成因对于揭示锗矿床的成因具有重要的意义。通过对薄层含碳硅质灰岩岩石化学、微量元素、稀土元素和碳、氧同位素的系统研究,并与典型的陆相热水沉积物进行对比,得出以下初步认识:(1)含碳硅质灰岩属陆相热水沉积成因;(2)含碳硅质灰岩的微量元素和稀土元素可能主要来自基底的二云母花岗岩;(3)煤中锗主要由形成含碳硅质岩等热水沉积岩的热水带来。 相似文献
993.
994.
Abstract: Microorganisms found at terrestrial and seafloor hydrothermal systems are classified based on their optimum growth temperatures. Prokaryotes exhibiting optimum growth temperatures above 45C are defined as thermophiles, while those with optimum growth temperatures above 80C are called hyperthermophiles. Hyperthermophiles have chemically and thermodynamically stable cytoplasmic‐membrane consisting of ether–lipids. Hyperthermophiles observed at temperature up to 113C in seafloor hydrothermal areas should have thermostable proteins. Presumably, the thermostable proteins are replacing certain amino acid residue by proline instead of alanine in order to increase hydrogen bonds and salt bridges. Microorganisms inhabiting terrestrial and seafloor hydrothermal areas obtain energy mainly by use of chemical disequilibrium, so that their habitat may be restricted to the redox boundary between ambient water and reduced hydrothermal fluids. Among more than 200 species of cultivable thermophiles and hyperthermophiles, hyperthermophiles mainly obtain energy by sulfur reduction, because this reaction can produce energy efficiently at > 80C. Some hyperthermophilic sulfur reducers can reduce Cr(VI), Mn(IV), Fe(III), Co(III), As(V), Se(VI), Tc(VII), Au(III) and U(VI) through hydrogen or organic compounds that act as reducing agents for yielding energy. Some hyperther‐mophiles use W instead of Mo for activating their enzymes. Bacteria can pump out toxic metal ions from their cells, however toxic metal resistance systems of archaea, including hyperthermophiles, have not yet been studied. Methane producing hyperthermophiles can yield energy by the autotrophic reaction, when sufficient carbon dioxide and molecular hydrogen can be supplied and methane can be removed from hydrothermal systems. If nitrogen can be supplied into a hydrothermal system, hydrogen oxidization by nitrogen species (e.g. NO3‐, NO2‐, NO and N2O) may be expected through the metabolism of some hyperthermophiles. 相似文献
995.
Abstract: The bio-essential elements are demanded for the metabolic action of all living organisms. These elements are continuously supplied to biosphere through the elemental cycle on the surface Earth. The geochemical cycle of bio-essential elements was most likely different in the pre-biotic era (ca. 4.4 to 4.0 Ga) compared to the modern Earth. The difference was probably made by the absence of continents and biological mediation in the pre-biotic environments. Geochemical cycle models of bio-essential elements (P, B and Mo) on the pre-biotic Earth are proposed in this study, and these models are examined using available geochemical data.
The input flux of phosphorous in pre-biotic oceans was probably dominated by submarine hydrothermal activities associated with carbonatized oceanic crusts. Such input flux by submarine hydrothermal activities is not known in the present-day oceans, and probably a unique flux in the pre-biotic oceans. Boron chemistry of pre-biotic oceans was also controlled by submarine hydrothermal input flux. The Mo exchange between the pre-biotic ocean and lithosphere may have restricted only at the submarine hydrothermal areas. These suggest that the submarine hydrothermal discharging areas were only locations to obtain bio-essential elements for the earliest life. This model is consistent with the previously proposed model for hydrothermal origin of life. 相似文献
The input flux of phosphorous in pre-biotic oceans was probably dominated by submarine hydrothermal activities associated with carbonatized oceanic crusts. Such input flux by submarine hydrothermal activities is not known in the present-day oceans, and probably a unique flux in the pre-biotic oceans. Boron chemistry of pre-biotic oceans was also controlled by submarine hydrothermal input flux. The Mo exchange between the pre-biotic ocean and lithosphere may have restricted only at the submarine hydrothermal areas. These suggest that the submarine hydrothermal discharging areas were only locations to obtain bio-essential elements for the earliest life. This model is consistent with the previously proposed model for hydrothermal origin of life. 相似文献
996.
997.
东太平洋隆是现代海底热液活动及热液沉积分布最为广泛的构造环境之一。本文对采自 EPR13°N 现代海底热液活动区附近的两个沉积物岩心分别进行了元素地球化学分析,并结合沉积物中有孔虫壳体对岩心进行关键层位 14C 年代学研究。目的在于通过对比距现代海底热液喷口不同距离的两岩心的地球化学特征,研究热液活动在岩心沉积物中所何存的地球化学记录,探讨海底热液活动对洋中脊附近沉积作用的贡献,以及热液活动在一定地质历史时期内的变化规律。显示,距热液喷口区相对较近的 B13-26 岩心沉积物含有丰富的热液特征组分,绝大多数微量元素和 REE 都与 Fe和Mn 成较强的正相关关系,而与 Al、Na、Ca、Mg、Ti 等元素相关性较弱或呈负相关,说明这些元素的富集机制主要是热液成因非晶质 Fe-Mn 化合物对热液及海水中元素的吸附作用。距热液喷口区相对较远的 B13-62岩心上部沉积物中元素的富集特征与 B13-26 岩心相似,但中下部沉积物中 Fe 与 Mn 无明显的相关关系,说明这些元素的富集主要受深海粘土沉积的影响,而受热液活动的影响减弱或消失。由于与海隆扩张轴距离的不同,两岩心受热液活动影响的强度不同。由海隆扩张轴向外,沉积作用受热活动的影响逐渐减弱,正常深海沉积作用逐渐加强。两个岩心沉积物地球化学上的共性是 Ca 和 Sr 都与其他元素呈现负相关关系或极微弱的正相关关系,表明生物碳酸盐沉积作用的独特性。有孔虫 14C 年龄测定结果表明,B13-26 岩心 35~250cm 段年龄十分接近,前后相差仅在几百年内。根据年龄测量中的误差范围,可以断定这段沉积物岩心是短时间内快速沉积的产物。结合热液活动特征性元素在岩心中的分布特征,判断该岩心段记录一次强烈的热液活动事件,从而形成了典型的事件沉积。在 B13-62 岩心的45~50cm 处测得有孔虫的 14C 年龄为距今 32900±530 yr。由于 14C 测年方法上的局限性,在岩心 135~140cm 处 14C 测年只能给出大于40000 yr 的结果。显然,B13-62 岩心处早期并没有受到热液活动明显的影响,沉积速率非常缓慢,只是在近期受到了热液活动的影响,形成了上部富含 Fe、Mn、Zn、Cr、Co、Ni、V 等热液活动特征元素的沉积。 相似文献
998.
Source process of a long-period event at Kilauea volcano, Hawaii 总被引:1,自引:0,他引:1
Hiroyuki Kumagai Bernard A. Chouet Phillip B. Dawson 《Geophysical Journal International》2005,161(1):243-254
999.
河草坑铀矿田位于大富足岩体北西部接触带附近,构造、岩浆及热液活动强烈,发育多种类型的铀矿床、矿点及放射性异常点带.其中发育在花岗岩外带含碳变质岩中的岩浆热液型铀矿,以及发育在花岗岩内带的岩浆热液叠加氧化淋滤而成的复成因铀矿,是今后的找矿目标类型. 相似文献
1000.
R.M. Prol-Ledesma C. Canet M.A. Torres-Vera M.J. Forrest M.A. Armienta 《Journal of Volcanology and Geothermal Research》2004,137(4):102
Shallow submarine hydrothermal activity has been observed in the Bahía Concepción bay, located at the Gulf coast of the Baja California Peninsula, along faults probably related to the extensional tectonics of the Gulf of California region. Diffuse and focused venting of hydrothermal water and gas occurs in the intertidal and shallow subtidal areas down to 15 m along a NW–SE-trending onshore–offshore fault. Temperatures in the fluid discharge area vary from 50 °C at the sea bottom up to 87 °C at a depth of 10 cm in the sediments.Chemical analyses revealed that thermal water is enriched in Ca, As, Hg, Mn, Ba, HCO3, Li, Sr, B, I, Cs, Fe and Si, and it has lower concentrations of Cl, Na, SO4 and Br than seawater. The chemical characteristics of the water samples indicate the occurrence of mixing between seawater and a thermal end-member. Stable isotopic oxygen and hydrogen composition of thermal samples plot close to the Local Meteoric Water Line on a mixing trend between a thermal end-member and seawater. The composition of the thermal end-member was calculated from the chemistry of the submarine samples data by assuming a negligible amount of Mg for the thermal end-member. The results of the mixing model based on the chemical and isotopic composition indicate a maximum of 40% of the thermal end-member in the submarine vent fluid.Chemical geothermometers (Na/Li, Na–K–Ca and Si) were applied to the thermal end-member concentration and indicate a reservoir temperature of approximately 200 °C. The application of K–Mg and Na/Li geothermometers for vent fluids points to a shallow equilibrium temperature of about 120 °C.Results were integrated in a hydrogeological conceptual model that describes formation of thermal fluids by infiltration and subsequent heating of meteoric water. Vent fluid is generated by further mixing with seawater. 相似文献