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排序方式: 共有129条查询结果,搜索用时 31 毫秒
41.
PP3超镁铁岩主要岩石类型有纯橄岩和石榴石橄榄岩,两者为渐变,主要矿物为橄榄石、铬尖晶石、石榴石、单斜辉石和斜方辉石.铬尖晶石的Cr#[Cr/(Cr+Mg) ×100]从51~89变化,TiO2和MnO2值分别低于0.26%和0.46%.铬尖晶石矿物表现为4期次演化的特点,反映了从岩浆期、榴辉岩相、角闪岩相和绿片岩相演化特征.随着超镁铁岩的演化,铬尖晶石表现为Cr#不断增大,而Mg#[Mg×100/(Mg+Fe2+) ]不断减少、氧逸度不断增加的过程.PP3铬尖晶石反映了地幔来源,为大陆岩石圈超镁铁岩特征,后期随折返而演化.从石榴石与铬尖晶石相互转变过程看出,PP3超镁铁岩经历了深度加大的过程,超镁铁岩曾经到达100km以上的岩石圈地幔深处.在绿片岩相-绿片角闪岩相变质过程中,铬尖晶石中Cr、Mg和Al减少,Fe相对增加,产生富Cr尖晶石变质作用样式.晚期剪切变形等次生变化影响了铬尖晶石矿物成分. 相似文献
42.
Migration of total chromium and chloride anion in the Rocha River used for estimating degradation of agricultural soil quality at the Thiu Rancho zone 下载免费PDF全文
The Rocha River is a receptor to receive wastewater from household, hospital and industry, from where contaminants are transported in the river, affecting biodiversity and the ecosystem of the area. In this paper we estimated the maximum transport of total chromium and chloride anion by applying the analytical model of Ogata & Banks (1961) , and the results obtained are grouped into three zones: Contaminated, transition, and uncontaminated. The analytical model was applied with 13 samples collected from the river piezometers installed near Rocha, where they are arranged in two lines, i.e. RH-1 to RH-6 as the first line and RH-9 to RH-12 as the second line. The total chromium concentrations range from 0.16 mg/L (RH-1) and 0.11 mg/L (RH-9) at the closest points to Rocha River, to 0.13 mg/L (RH-7) and 0.03 mg/L (RH-12) at the most remote points to the river. The advance of the pollutants does not exceed 50 meters with respect to the axis of the Rocha River. 相似文献
43.
随着多接收质谱仪分析技术的进步,铬稳定同位素体系在最近二十几年的环境科学和地球化学中得到了越来越广泛的应用。铬元素属于氧化还原敏感元素,在氧化还原反应过程中伴随着较大的同位素分馏。因此,铬同位素在指示现代或古代环境的氧化还原状态方面有着重要的应用。同时,铬也是中度相容和轻度亲铁元素,使得铬稳定同位素体系也可用来制约高温地质过程(如核幔分异、地幔熔融和岩浆分异结晶等)以及地外行星的演化。本综述首先介绍铬稳定同位素体系,随后讲述分析方法、铬同位素分馏原理以及铬同位素在高温、低温地球化学中的应用。 相似文献
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地下水污染的原位修复是当今国际上净化地下水最具发展前景的新技术,但对铬污染地下水原位修复尚未有科学有效的评价方法。定量评价地下水中Cr(Ⅵ)的被还原程度成为保护与修复铬污染地下水的关键问题。通过室内Cr(Ⅵ)的还原实验,分析Cr(Ⅵ)在还原过程中铬稳定同位素变化规律,研究其分馏机理,探索利用铬同位素定量评价地下水中Cr(Ⅵ)还原程度的可行性。研究结果表明:Cr(Ⅵ)在被还原成Cr(Ⅲ)过程中,发生明显的同位素分馏,即反应物中53Cr逐渐富集,同时生成物中52Cr逐渐富集;分馏过程可用瑞利分馏模型描述,分馏系数α为常数0.99842。表明δ53Cr能够定量评价水体中Cr(Ⅵ)的还原程度,为评价地下水铬污染修复提供了新途径。 相似文献
47.
本文研究了有溴化十六烷基吡啶(CPB)存在时,在pH5.0—7.0的NaAc-HAc缓冲溶液中,苯基荧光酮(PF)与Cr(Ⅵ)的显色反应。在80—90℃保温10min,生成紫红色三元配合物,其组成比为:〔Ct(Ⅵ)〕:〔PF〕:〔CPB)=1:2:2。ε_(580)为1.1×10~5L·mol~(-1)·cm~(-1),0—6μg Cr(Ⅵ)/25ml范围内符合比尔定律。在碱熔分离后并有混合掩蔽剂存在下,一般共存离子不干扰Cr(Ⅵ)的测定.应用本法测定了环境水、土壤和矿石中痕量Cr。 相似文献
48.
Vladislav Chrastný Jan Rohovec Eva Čadková Jan Pašava Juraj Farkaš Martin Novák 《Geostandards and Geoanalytical Research》2014,38(1):103-110
In recent years, routine application of the stable isotope determination of chromium (Cr) in environmental and health protection research has led to the search for simpler chromite decomposition techniques. As the range of Cr isotope abundance ratios in nature is very narrow, conventional chromite decomposition techniques are no longer suitable, due to the relatively high risk of contamination during laboratory procedures. We have developed a protocol for the decomposition of chromites based on oxidation by bromic acid at room temperature. The procedure takes 15 d and requires two doses of bromic acid during the reaction period (day 1 and 8), due to the limited stability of the reagent. Chromium extracted by alkaline oxidative fusion and by bromic acid decomposition yielded statistically indistinguishable δ53Cr values, measured by multi‐collector inductively coupled plasma‐mass spectrometry following addition of a 50Cr‐54Cr double‐spike. 相似文献
49.
利用硅藻土负载羟基氧化铁颗粒作吸附剂对六价铬进行吸附和解吸附实验,探讨了硅藻土负载羟基氧化铁对六价铬的吸附机制和固体浓度效应。实验结果表明:在实验条件下,当吸附剂的用量从0.05 g增加到0.2 g时,六价铬的吸附量从23940.124μg/g降低到8575.415μg/g,吸附剂对Cr6+的吸附存在明显的固体浓度(Cs)效应。吸附滞后角随着Cs 的增加而减小,吸附反应的可逆性增大。将实验数据分别用Languir和Freundlich吸附模型进行拟合,发现Freundl-ich吸附模型对实验数据拟合效果较好,表明该吸附反应以单分子层吸附为主。 相似文献
50.
Quartz‐andalusite‐fuchsite rocks in an Archaean greenstone belt at Menzies, Western Australia, are described in their geological setting. They are shown to have developed from intense metasomatism of layered rocks of komatiitic composition. Ratios of the immobile components Al2O3, TiO2, Cr, V and Zr are consistent, despite wide variations in their absolute values, and compare closely with those of an underlying komatiite suite. Marked depletion of Ca, Na, Mg and Fe has led to a strongly peraluminous composition and enhanced Cr values. Silicification and introduction of K has also occurred. Most of the metasomatism took place before peak metamorphism, and the mineral assemblage is now dominated by andalusite, fuchsite, and recrystallized quartz. Schlieren or vein‐like segregations rich in andalusite, chromite, rutile and minor sulphides and tourmaline are interpreted as the original fluid pathways, where concentration of immobiles was achieved through solution of mobile components, and volume loss. They have been termed residual veins. Metasomatism is believed to have taken place by synvolcanic processes analogous to those operating in modern hot spring systems. The rocks were severely modified by metamorphism and tectonism. The fuchsitic rocks at Menzies are compared to similar rocks in other areas. 相似文献