黔中沉积磷灰石的硫碳同位素及其地质意义   总被引：5，自引：0，他引：5  

陈其英  封兰英 《岩石学报》1996,12(4):594-597

本文研究了黔中磷块岩中磷灰石的结构硫同位素组成。磷灰石的δ３４Ｓ值为３４．２‰～４２．４‰，它高于同期海水的δ３４Ｓ（约３４．２‰），也高于共生的成岩黄铁矿的δ３４Ｓ（１５．４‰～１９．８‰），表明磷灰石形成于富有机质沉积物早期成岩作用硫酸盐还原带的最上部，其间同时伴有大量硫酸盐细菌的还原过程。磷灰石的碳同位素组成（δ１３Ｃ＝－３．６３‰～１．０‰），表明它含有微生物有机质分解演化而来的ＣＯ２－３，而磷灰石比胶结白云石更富集轻同位素则反映出沉积阶段生物作用的影响比成岩阶段更为明显  相似文献   

石英砂选矿厂尾砂综合利用研究   总被引：3，自引：0，他引：3       下载免费PDF全文

蒋学鑫  陈培荣 《地质找矿论丛》2001,16(4):276-278

为了实现石英资源的综合利用和保护环境，对原来的石英砂生产工艺进行了改造，降低了石英尾砂中的杂质含量，基于石英砂中SiO2含量高，粒度细的特点，开发出了以石英尾矿为原料生产石英粉的新工艺，所得产品符合无碱玻纤和釉料熔块工业的要求。  相似文献   

Environmental history of the south-eastern South Atlantic since the Middle Miocene: evidence from the sedimentological records of ODP Sites 1088 and 1092   总被引：1，自引：0，他引：1  

Bernhard Diekmann  Mareike Fälker†  Gerhard Kuhn† 《Sedimentology》2003,50(3):511-529

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Metasomatized harzburgite xenoliths from Avacha volcano as fragments of mantle wedge of the Kamchatka arc: Implication for the metasomatic agent   总被引：6，自引：0，他引：6  

Shoji Arai  Satoko Ishimaru  Victor M. Okrugin 《Island Arc》2003,12(2):233-246

Abstract   Abundant peridotite xenoliths have been found in pyroclasitics of Avacha (Avachinsky) volcano, the south Kamchatka arc, Russia. They are mostly refractory harzburgite with or without clinopyroxene: the Fo of olivine and Cr/(Cr + Al) atomic ratio of spinel range from 91 to 92 and from 0.5 to 0.7, respectively. They are metasomatized to various extents, and the metasomatic orthopyroxene has been formed at the expense of olivine. The metasomatic orthopyroxene, free of deformation and exsolution, is characterized by low contents of CaO and Cr₂O₃. The complicated way of replacement possibly indicates low viscosity of the metasomatic agent, namely hydrous fluids released from the relatively cool slab beneath the south Kamchatka arc. This is a good contrast to the north Kamchatka arc, where the slab has been hot enough to provide slab-derived melts. High content of total orthopyroxene, 40 vol% on average, in metasomatized harzburgite from Avacha suggests silica enrichment of the mantle wedge, and is equivalent to some subcratonic harzburgite. Some subcratonic harzburgites therefore could have been formed by transportation of subarc metasomatized peridotites to a deeper part of the upper mantle.  相似文献   

A Study on the Formation of Smectite in Silica Scales Precipitated from Geothermal Water: The Effect of Magnesium     

Yoshinobu Aramaki    Takushi Yokoyama  Yoshihiro Okaue  Akira Imai  Koichiro Watanabe 《Resource Geology》2005,55(3):281-284

Abstract. Silica scales containing large amounts of smectite were recently found in the pipelines for geothermal water at a geothermal power plant. To elucidate the mechanism of smectite formation, seven silica scale samples were characterized by powder X-ray diffraction, chemical analysis and ²⁷A1 MAS NMR. Smectite was present in samples with MgO levels above 10 wt% and Al₂O₃ levels below 10 wt%. In ²⁷A1 MAS NMR spectra, peaks assigned to both tetrahedrally and octahedrally coordinated aluminum (Al(4) and Al(6)) were observed for Mg-rich samples, whereas a peak due to Al(4) alone appeared in Mg-poor samples. From these observation and comparison between ²⁷A1 MAS NMR spectra for synthesized precipitates of Al₂O₃-SiO₂ containing MgO and not containing MgO, it is concluded that magnesium plays an important role in the stabilization of Al(6), and results in the formation of smectite  相似文献   

纳米纤维状白炭黑的孔隙特征   总被引：5，自引：0，他引：5  

王丽娟鲁安怀  王长秋郑喜珅  赵东军刘瑞 《岩石矿物学杂志》2005,24(6):515-520

在与传统白炭黑对比研究基础上,利用TEM、XRD、FT_IR和氮吸附法对纳米纤维状白炭黑(MLD为92.73%)进行研究,主要讨论了纳米纤维状白炭黑多孔结构的成因、孔径大小、孔分布及孔类型等特征。分析表明纤蛇纹石中氢氧镁石八面体层被酸溶蚀和硅氧四面体层的塌陷是导致这种白炭黑具有多孔纳米纤维结构的直接原因;有两种孔隙类型,即纤维上的孔隙和纤维的堆积孔隙;纤维上的孔隙包括SiO_2微粒间的孔隙、其聚结体间的孔隙、残余纳米管的管道和毛细管道;孔径2.1和3.8nm处的孔隙数量多,并且在纳米纤维(或管)上存在大量小于5nm左右的微孔。研究证明了在用于橡胶、塑料填充补强剂和催化剂载体等方面,纳米纤维状白炭黑更优于传统白炭黑。  相似文献   

SF对水泥土的影响初探     

黄殿瑛  张可能 《大地构造与成矿学》1995,19(3):284-287

本文介绍了一种新型的软土地基处理剂──硅粉在水泥加固土中部分取代水泥后的试验结果，掺入硅粉后水泥用量可大幅度减少，水泥土强度有很大提高。对水泥土中ＳＦ的作用进行了探讨。  相似文献   

The Hot—Spring Genesis of the Shimen Realgar Deposit,Northwest Hunan     

张景荣  王蔚等 《中国地球化学学报》1993,12(2):137-147

The Shimen realgar deposit is characterized by the pipi-shaped orebody and the development of silica sinter and hydrothermal explosive breccia which are typical of hot spring activity.Very similar trace-element associations are noticed between the silica cap and the breccia and modern hot spring waters in the area.The chemistr of ore-forming solutions is also well comparable with that of modern hot spring.,The spring system that gave rise to the mineralization was charged by ground waters heated through thermal conducting systems in the deep crust and,to a lesser extent,by geothermal gradient.ΔD,δ^18O,δ^13CCH4andδ^13CH4andδ^13CCO2values and ^40Ar/^36Ar and 3^He/^4He ratios indicate that the spring system is of crustal derivation.The ore-forming metals were supplied by surrounding strata,particularly those underlying the ore deposits.The mechanim of ore deposition is thought to be hydrothermal explosion and accompanying boiling and abrupt changes in pH and Eh.Located in northwest Hunan,the Shimen realgar deposit is the leading arsenic producer in the country,However,regardless of its long mining history,the genesis of this deposit has long been a puzzle.It was considered to be postmagmatic epithermal in the leading arsenic producer in the puzzle.It Was considered to be postmagmatic epithermal in origin,but this is trongly challenged by filling(metasomatism)in karst environment proposed later by Zhou Zhiquan(1986)also encounters a number of difficulties.For example,why can the pipi-shaped orebody vertically extend up to several hundreds meters without any compatible development in the lateral dimension? A hot spring genesis is suggested in the present paper based on geological observations and laboratory studies conducted by the authors in recent years.  相似文献   

Measurement of biogenic sulfur emissions from soils and vegetation using dynamic enclosure methods: Total sulfur gas emissions via MFC/FD/FPD determinations     

D. L. MacTaggart  D. F. Adams  S. O. Farwell 《Journal of Atmospheric Chemistry》1987,5(4):417-437

Metal foil collection/flash desorption/flame photometric detection (MFC/FD/FPD) was one of the analytical methods used to measure emissions of gaseous, sulfur-containing compounds from several terrestrial natural sources during a cooperative field program in the summer of 1985. Nonspeciated, total sulfur gas emissions were determined by using the MFC/FD/FPD technique in combination with a Nafion Perma-Pure drying device to sample air from three designs of dynamic enclosure chambers. These enclosures were placed over various soil orders and vegetation in the vicinity of field sites in Iowa and Ohio previously examined during the 1977–80 SURE study of biogenic sulfur fluxes. Because of the sensitivity and detection characteristics of the MFC/FD/FPD technique, it was possible to obtain measurements on enclosure air samples that were collected for relatively short time periods,. e.g., 1 to 5 min. The magnitudes of these time-resolved, total sulfur gas emissions are correlated exponentially with internal enclosure air temperatures. Potential errors and uncertainties associated with this application of the MFC/FD/FPD methodology are assessed.The total sulfur gas flux values obtained from this study and the SURE program are compared. Unquantified sources of error in the current two parameter extrapolation model used to calculate regional and global terrestrial source strengths of biogenic sulfur emissions are also summarized and are shown to prevent a reliable estimate of overall uncertainty limits in the resultant inventory.  相似文献   

On Silica Activity and Serpentinization   总被引：10，自引：0，他引：10  

Frost  B. Ronald; Beard  James S. 《Journal of Petrology》2007,48(7):1351-1368

Serpentinites have the lowest silica activity of common crustalrocks. At the serpentinization front, where olivine, serpentine,and brucite are present, silica activities (relative to quartz)are of the order of 10^–2·5 to 10^–5, dependingon the temperature. Here we argue that this low silica activityis the critical property that produces the unusual geochemicalenvironments characteristic of serpentinization. The formationof magnetite is driven by the extraction of silica from theFe₃Si₂O₅(OH)₄ component of serpentine, producing extremely reducingconditions as evinced by the rare iron alloys that partiallyserpentinized peridotites contain. The incongruent dissolutionof diopside to form Ca²⁺, serpentine, and silica becomes increasinglyfavored at lower T, producing the alkalic fluids characteristicof serpentinites. The interaction of these fluids with adjacentrocks produces rodingites, and we argue that desilication isalso part of the rodingite-forming process. The low silica activityalso explains the occurrence of low-silica minerals such ashydrogrossular, andradite, jadeite, diaspore, and corundum inserpentinites or rocks adjacent to serpentinites. The tendencyfor silica activity to decrease with decreasing temperaturemeans that the presence of certain minerals in serpentinitescan be used as indicators of the temperature of serpentinization.These include, with decreasing temperature, diopside, andraditeand diaspore. Because the assemblage serpentine + brucite marksthe lowest silica activity reached in most serpentinites, thepresence and distribution of brucite, which commonly is a crypticphase in serpentinites, is critical to interpreting the processesthat lead to the hydration of any given serpentinite. KEY WORDS: serpentinization; serpentinites; silica activity; oxygen fugacity; rodingites; magnetization of serpentinites  相似文献