共查询到20条相似文献，搜索用时 15 毫秒
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尹福光 《沉积与特提斯地质》2003,23(4):79-83
康滇地区裂谷作用已得到证实,但形成这种地堑地垒的格局有多种解释,以传统的地质力学分析为主。笔者借以热力学的自由热对流原理来加以论述：攀西巨厚的火山岩体在下覆异常地幔热作用下,发生自由热对流,引起热量散失,使地壳沉降与隆起不均衡,生成地堑地垒的格局。自由对流单元的侧向迁移,使盆地形成非对称性。 相似文献
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A detailed investigation of the protoglobigerinids from the Kimmeridgian section of the Montagne de Crussol, SE France is presented. This monotonous succession of predominantly carbonate beds represents peri-platform hemipelagic deposits, well dated by ammonites. Three species were determined in thin sections and in isolated forms after extraction by acetolysis. Favusella? parva (Kuznetsova) is the most common species occurring in almost the entire succession from the Orthosphinctes to the Beckeri zones. Favusella hoterivica (Subbotina) has been retrieved less frequently from the Platynota to the Beckeri zones, and it is its oldest occurrence. The rare Globuligerina bathoniana (Pazdrowa) occurs only in the Late Kimmeridgian. Based on our study and the review of the literature a palaeogeographical map was plotted, showing that most of the protoglobigerinid occurrences are in deep water facies of the northern margin and central part of the Tethys. These records demonstrate the presence of Globuligerina bathoniana, G. oxfordiana (Grigelis), Favusella hoterivica, F.? parva and Compactogerina stellapolaris (Grigelis) in the Kimmeridgian. 相似文献
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通过对分离结晶作用和批式熔融作用Cly/Clx-Cly图解的数学分析,笔者认为,虽然ClLa/Clsm-ClLa图解在一定程度上能区分这两种不同岩浆作用过程,但是,Treuil等的解释是不完全的。直线的斜率和截距还极大地受参数Cox,Coy,Dx,Dy的影响。该图解并非总是有效。本文还给出了一般式Cly/Clx-Cly在其它方面的可能应用。 相似文献
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Selenium isotope fractionation during reduction by Fe(II)-Fe(III) hydroxide-sulfate (green rust) 总被引：1，自引：0，他引：1
Thomas M. Johnson 《Geochimica et cosmochimica acta》2003,67(3):413-419
We have determined the extent of Se isotope fractionation induced by reduction of selenate by sulfate interlayered green rust (GRSO4), a Fe(II)-Fe(III) hydroxide-sulfate. This compound is known to reduce selenate to Se(0), and it is the only naturally relevant abiotic selenate reduction pathway documented to date. Se reduction reactions, when they occur in nature, greatly reduce Se mobility and bioavailability. Se stable isotope analysis shows promise as an indicator of Se reduction, and Se isotope fractionation by various Se reactions must be known in order to refine this tool. We measured the increase in the 80Se/76Se ratio of dissolved selenate as lighter isotopes were preferentially consumed during reduction by GRSO4. Six different experiments that used GRSO4 made by two methods, with varying solution compositions and pH, yielded identical isotopic fractionations. Regression of all the data yielded an instantaneous isotope fractionation of 7.36 ± 0.24‰. Selenate reduction by GRSO4 induces much greater isotopic fractionation than does bacterial selenate reduction. If selenate reduction by GRSO4 occurs in nature, it may be identifiable on the basis of its relatively large isotopic fractionation. 相似文献
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在山东蒙阴金伯利岩中，首次发现了沂蒙矿类质同象系列新的富Ti矿物（变）种。理想的晶体化学式可表达为：K（Ti5Fe3Cr2Mg2）12O19（简称K－Ti沂蒙矿）（Ba，K）（Ti5Fe4Mg2Cr）12O19（简称Ba－Ti沂蒙矿）从而与原来确定的沂蒙矿K（Cr5Ti3Fe2Mg2）12O19和钡钛铁铝矿（Ba，K）（Cr4Fe4Ti3Mg）12O19一起构成了金伯利岩中AM12O19磁铁铅矿型矿物的K-Cr、Ba－Cr、K-Ti、Ba-Ti四种端元类型的复杂类质同象系列。新发现的两个矿物（变）种均产出于具叶片状尖晶石出溶体的镁钛铁矿中。根据结构已知的沂蒙矿中原子的占位和配位多面体情况，分析了K－Ti，Ba－Ti沂蒙矿中各原子的占位和配位多面体，认为新发现的两个（变）种在成分上与沂蒙矿和钡钛铁铬矿有明显的区别。根据镁钛铁矿、尖晶石、沂蒙矿新（变）种、钙钛矿之间的相互关系，探讨了它们的形成环境，从而为这类矿物的地幔成因提供了直接证据。 相似文献
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Kent Brooks 《Geology Today》2019,35(5):196-200
Few people have heard of the mineral sphene (also called titanite), but it is nevertheless extremely widespread, occurring in most common rocks. It can be useful to the Earth scientist as it contains information on the timing, temperature and pressure of formation of many common rocks. It is also a source of titanium—and can sometimes be used as a gemstone. 相似文献
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Arsenite adsorption on galena (PbS) and sphalerite (ZnS) 总被引：1，自引：0，他引：1
Benjamin C. Bostick 《Geochimica et cosmochimica acta》2003,67(5):895-907
Arsenite, As(III), sorption on galena (PbS) and sphalerite (ZnS) was investigated as a function of solution composition and characterized using X-ray absorption spectroscopy (XAS). Adsorption conformed to a Langmuir isotherm except at the highest surface loadings, and it was not strongly affected by changes in ionic strength. Arsenite sorbed appreciably only at pH > ∼5 for PbS and pH ∼4.5 for ZnS, behavior distinct from its adsorption on other substrates. Arsenite adsorption on PbS and ZnS resulted in the conversion from As-O to As-S coordination. Arsenite does not adsorb through ligand-exchange of surface hydroxyl or sulfhydryl groups. Rather, it forms a polynuclear arsenic sulfide complex on ZnS and PbS consistent with the As3S3(SH)3 trimer postulated by Helz et al. (1995) for sulfidic solutions. This complex was unstable in the presence of oxidizing agents and synchrotron light—it quickly converted to As(V), which was largely retained by the surface. These data illustrate the complexity of As(III) adsorption to even simple sulfide minerals. 相似文献
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Thermodynamic properties of high-pressure minerals that are not recoverable from synthesis experiments by conventional quenching
methods (“unquenchable” phases) usually are calculated from equation of state data and phase diagram topologies. The present
study shows that, with cryogenic methods of recovery and sample treatment, phases with a suitable decomposition rate can be
made accessible to direct thermodynamic measurements. A set of samples of Ca(OH)2-II has been synthesized in a multianvil device and subsequently recovered by cooling the high-pressure assembly with liquid
nitrogen. Upon heating from liquid nitrogen to room temperature, the material transformed back to Ca(OH)2-I. The heat effect of this backtransformation was measured by differential scanning calorimetry. A commercial differential
scanning calorimeter (Netzsch DSC 404), modified to allow sample loading at liquid nitrogen temperature was used to heat the
material from −150 to +200 °C at rates varying between 5 and 15 °C min−1. The transformation started around −50 °C very gradually, and peaked at about 0 °C. To obtain a baseline correction, each
sample was scanned under exactly the same conditions after the backtransformation was complete. Because of the relative sluggishness,
onset and offset temperatures were not well defined as compared to fast (e.g., melting) reactions. To aid in integration,
the resulting signals were successfully fitted using a generic asymmetric peak model. The enthalpy of backtransformation was
determined to be ΔH =−10.37 ± 0.50 kJ mol−1. From previous in situ X-ray diffraction experiments, the location of the direct transformation in P-T space has been constrained to 5.7 ± 0.4 GPa at 500 °C (Kunz et al. 1996). With the reaction volume known from the same study,
and assuming that ΔC
p
of the transformation remains negligible between the conditions of our measurements and 500 °C, our result gives an estimate
of the entropy of transition and the P-T slope of the reaction curve. To a first approximation, the values ΔS = −16.00 ± 0.65 J(mol · K)−1 and dP/dT = 0.0040 ± 0.0002 GPa/K have been determined. These results need to be refined by equation of state data for Ca(OH)2-II.
Received: 30 December 1999 / Accepted: 10 April 2000 相似文献
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《Geochimica et cosmochimica acta》1999,63(19-20):2939-2955
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用强功率四圆单晶衍射仪精确地修正了氟碳铈矿和氟铈矿的晶体结构．氟碳铈矿（ｂａｓｔｎａｅｓｉｔｅ，Ｃｅ（ＣＯ３）Ｆ）属六方晶系，其晶胞参数为：ａ＝０．７１４３８（９）ｎｍ，ｃ＝０．９８０８（２）ｎｍ，γ＝１２０°，Ｚ＝６，空间群Ｐ６－２ｃ．使用３６７个（Ｆ≥３σ（Ｆ））独立衍射点，经多轮最小二乘法修正后，最终获得偏离因子Ｒ＝０．０４９９．氟碳铈矿的晶体结构特征表现为［ＣＯ３］平面三角形平行ｃ轴分布，铈的配位数为９，Ｃｅ－Ｏ（Ｆ）平均键长为０．２５１５ｎｍ，Ｃ－Ｏ平均键长０．１３２７ｎｍ，每个氟原子与周围三个铈原子相连．氟铈矿（ｆｌｕｏｃｅｒｉｔｅ，ＣｅＦ３）属六方晶系，其晶胞参数为：ａ＝０．７１４１２（２１）ｎｍ，ｃ＝０．７２９８９（２１）ｎｍ，γ＝１２０°，Ｚ＝６．其空间群为：Ｐ３－ｃ１（Ｎｏ．１６５）．使用３２１个（Ｆ≥３σ（Ｆ）））独立衍射点，经多轮最小二乘法修正后，最终获得偏离因子Ｒ＝０．０５４２．氟铈矿的晶体结构表现为每个氟原子与周围三个铈原子相连接，每个铈原子与周围９个氟原子相连，铈的配位数为９，Ｃｅ－Ｆ平均键长为０．２４６８ｎｍ． 相似文献