冲绳海槽玄武岩中中酸性残余熔体研究及其岩石学意义

与洋壳有关的酸性岩由于对了解幔源岩浆的演化以及判别古老蛇绿岩套及其构造位置的重要意义而倍受岩石学家和构造地质学家的关注。本对发现于冲绳海槽玄武岩基质中的中酸性到酸性残余熔体进行了详细研究，它们提供了幔源玄武岩浆结晶分异形成酸性岩浆的直接证据。在细小的基质矿物间分布有一种玻璃质的残余熔体，其成分随距冷凝边距离(L)的增加而越来越酸性。在SiO2对Na2O K2O图解上，残余熔体的投影点从玄武岩到英安岩均有分布，反映了一个连续的演化系列。在AFM图解上，残余熔体表现出与Thingmuli火山岩系列类似的拉斑玄武岩系列的演化趋势。我们的研究表明：残余熔体的演化受结晶分异作用控制。在早期结晶阶段，辉石的结晶起主导作用，结果造成残余熔体中SiO2、Al2O3，Na2O的迅速增加，FeO、MgO、CaO迅速降低。在晚期结晶阶段，斜长石成为主导结晶相，导致残余熔体中Al2O3，Na2O的迅速消减。Al2O3、Na2O从增加到降低的转变出现在SiO2=62％左右。在L=27．5mm处，85～90％的基质岩浆已发生了结晶作用，导致残余熔体中SiO2含量达到69～70％，而且此处还新出现了一种富FeTi的氧化物。该玄武岩中残余熔体和基质矿物的成分及演化特征分别与Thingmuli火山岩系列中酸性端元的组成相似，在也佐证了Thingmuli火山岩系列是幔源岩浆结晶分异的产物.     

Downstream composition changes of acidic volcanic waters discharged into the Banyupahit stream, Ijen caldera, Indonesia

The crater lake of Kawah Ijen volcano contains extremely low pH (<0.4) waters with high SO₄ (70000 mg/kg), Cl (21000 mg/kg), F (1500 mg/kg), Al (5000 mg/kg), Fe (2000 mg/kg) and trace metal (Cu 0.5, Zn 4, Pb 3 mg/kg) contents. These brines seep outward through the western crater rim and reappear on the other side as streamlets, which form the headwaters of the Banyupahit stream. The Banyupahit first mixes with fresh rivers and thermal springs in the Ijen caldera and then irrigates a coastal agricultural plain which is 30 km from the summit crater.We discuss the downstream composition changes affecting the Banyupahit waters by using stable isotope, chemical and mineralogical data collected from sites along the stream length. The saturation of the stream waters with respect to minerals was evaluated with SOLVEQ and WATEQ4F and compared with the geochemical observations. An aluminous mineralogy (alunogen, pickeringite, tamarugite and kalinite) develops in the upper part of the Banyupahit due to concentration of the headwaters by evaporation. Downstream attenuation of dissolved element concentrations results principally from dilution and from mineral precipitation. The stream pH changes from 0 at the source to >4 close to the mouth. The δD and δ¹⁸O values and the relative SO₄–Cl–F contents of the Banyupahit waters indicate that the tributaries are mostly meteoric. Dissolved SO₄ in the acidic stream come only from the crater lake seepages and are not involved later in microbially mediated reactions, as shown by their δ³⁴S and δ¹⁸O values. Re-equilibration of the stream SO₄ oxygen-isotope composition with H₂O from tributaries does not occur.Calcium, SiO₂, Al, Fe, K and SO₄ behave non-conservatively in the stream waters. Gypsum, silica (amorphous or poorly ordered), a basic aluminum hydroxysulfate (basaluminite?), K-jarosite and amorphous ferric hydroxide may exert a solubility control on these elements along the entire stream length, or in certain stream sections, consistent with the thermochemical model results. Downstream concentration trends and mineral saturation levels suggest that precipitation of Sr-, Pb-rich barite and celestite consume Ba, Sr and Pb, whereas dissolved Cu, Pb and Zn may adsorb onto solid particles, especially after the junctions of the acidic stream with non-acidic rivers. We calculated that significant fluxes of SO₄, F, Cl, Al, SiO₂, Ti, Mn and Cu may reach the irrigation system, possibly causing serious environmental impacts such as soil acidification and induration.     

Analysis of patterns of vertical and temporal distribution of phytoplankton using multifactorial analysis: Acidic Lake Caviahue, Patagonia, Argentina

Most existing studies on the algal communities of acid lakes are based on environments that have been caused by anthropogenic disturbances. Such lakes have a different origin compared to the natural acidic lakes and could be expected to differ also in the mechanisms controlling phytoplankton and trophic status. Planktonic community in Lake Caviahue is somewhat diverse in spite of the low pH of the water. Algae have a distinctive vertical distribution: the values of phytoplankton biomass remain constant throughout the water column and at times were highest in the upper end of the hypolimnion, forming a maximum or a layer of chlorophyll a at depth. The goal of this work was to investigate the factors influencing the seasonal and vertical distribution of phytoplankton. The lake was sampled between the years 2004 and 2006. Physical, chemical and biological parameters at different depths throughout the water column were determined. The interrelationships between environmental variables at different sampling dates were analyzed using an integration of multivariate matrices, multiple factor analysis, to analyze any joint partnerships in the samples. We found that phytoplankton biomass is dominated by Keratococcus rhaphidioides. With regard to zooplankton, we found a single species of rotifers (Philodina sp.). The two arms of the lake and the depths have different behaviours showing differences in the arms' conductivity, dissolved oxygen and pH. The more superficial layers were characterized by high values of phytoplankton and zooplankton biomass, organic and inorganic carbon, dissolved oxygen and pH. The deeper layers showed high values of chlorophyll a, ammonium and phosphorus (dissolved and particulate). From the multivariate analysis the relationships of the each algal species with pH, as a possible indicator of the degree of “acidophilia”, could be extracted.     

阿尔泰额尔齐斯带东段酸性岩墙群地球化学特征及其地质意义

野外地质调查发现在阿尔泰南缘额尔齐斯构造带东段、额尔齐斯活动断裂与富蕴-锡泊渡断裂之间发育了一套未变形的酸性岩墙群.岩墙群侵位于海西期片麻岩化花岗岩和上石炭统深变质的额尔齐斯组岩层中,薄片鉴定和岩石地球化学分析确定为具有细晶结构的流纹斑岩.岩石的SiO2含量为70.9%～75.38%,K2O＋Na2O含量为7.55%～8.99%;大部分样品Na2O＞K2O,里特曼指数值为1.8～2.5之间,Al2O3=12.80%～14.53%,A/CNK=0.9～1.1,NK/A=0.7～0.9,具有准铝质-弱过铝质、低镁、高钾钠、低钙和锶、高（Fe）mol/（Mg）mol特点,具A型花岗岩类特点,属于亚碱性脉岩.岩石轻稀土富集,大离子亲石元素相对富集,具有明显的中等负铕异常,壳源特征明显.锆石U-Pb二次粒子微探针测年显示岩墙群形成于277～286Ma.推断岩墙是阿尔泰海西期造山运动结束后,在拉张构造环境下的地壳局部熔融产物.     

钽钼杂多酸—碱性染料多元缔合物体系的研究

在PVA、OP或Tween-60存在下,采用平衡移动法确定了碱性染料亚甲基蓝、耐尔蓝(NB)、罗丹明B(RB)、丁基罗丹明B(BRB)、结晶紫(CV)、乙基紫(EV)与Ta的摩尔比是1:1至7:1;考察了NB(或BRB)-钽钼杂多酸缔合物的红外光谱,初步探讨了反应机理:比较了几个碱性染料-钽钼杂多酸缔合物体系的光度特性,筛选出两个摩尔吸光系数>2×10~6的分析体系,并用于合金钢和地质标样中痕量Ta的测定,方法可行。     

东营凹陷北部沙河街组四段深部储层多重成岩环境及演化模式

主要通过薄片鉴定、扫描电镜观察、包裹体分析、粘土矿物分析、镜质体反射率测试和岩心物性分析等手段,结合构造发育史和有机质热演化史等研究成果,以揭示东营凹陷北带古近系深部碎屑岩储层成岩环境及演化模式为目的展开研究工作。结果表明:东营凹陷北带古近系深部碎屑岩储层存在酸性、碱性和酸性碱性交替等多重成岩环境。酸性成岩环境以碳酸盐矿物溶解、长石溶解蚀变为高岭石并伴生石英次生加大等为标志,碱性成岩环境以石英质颗粒及其次生加大边溶解、长石次生加大和晚期碳酸盐矿物沉淀为标志。研究区古近系深部碎屑岩储层成岩环境由浅至深大致经历了碱性—酸性—酸性碱性交替(局部碱性较强)—碱性—弱碱性的演化过程,并建立了沙河街组四段的成岩演化和储层改造模式。     

Soil water residence times and solute uptake on a dolomite bedrock—preliminary results

Calcium and magnesium levels have been monitored in slope foot drainage waters on a dolomite bedrock. Both calcium and magnesium rich pulses occur. Short term dissolution experiments demonstrate high calcium levels in solution while other authors have suggested that long residence time groundwater has relatively high levels of magnesium due to calcite precipitation. Patterns of field fluctuations in Ca: Mg ratios can thus be tentatively interpreted in terms of short residence time water of high calcium content mixing with long residence time water of high magnesium content. Fluorometric dye tracing has been used to indicate the orders of magnitude of soil water residence times, suggesting that quickflow components are resident in the system for a few hours to a few days. Further work is in progress.     

Photocatalytic Activity of Combustion Synthesized Nanocrystalline CeAlO3

The photocatalytic activity of combustion synthesized nanocrystalline CeAlO₃ was determined for the degradation of four anionic and four cationic dyes. The perovskite oxide showed high‐photocatalytic activity and a complete degradation of all the dyes was possible within 2 h. The photocatalytic activity of the compound was comparable with the activity of the commercial Degussa P‐25 TiO₂ catalyst. The degradation of dyes was found to follow first order kinetics and the first order degradation rate constants were determined.     

白银厂酸性火山岩地球化学特征及成因分析

甘肃白银厂矿田是我国著名的火山成因块状硫化物矿床产地,赋矿岩石主要为酸性火山岩(石英角斑岩和石英角斑凝灰岩)。文章通过对白银厂矿区酸性火山岩的岩相学和岩石地球化学特征研究,结果表明:1)岩石发生了低绿片岩相的变质作用,镜下可见明显的绢云母化、绿泥石化等蚀变作用,造成了岩石K、Ca、Na、Rb等活泼元素的迁移;2)岩石具有高硅、低钛、弱铝、贫镁,亏损高场强元素Nb、Ta,以及明显的Sr、P、Ti、Eu的负异常和Th、U、Pb正异常特征,表明本区酸性火山岩可能为下地壳基性岩重熔的产物,源区存在斜长石、磷灰石以及钛铁矿等矿物的残留,并且岩浆在演化过程中经历过围岩的混染与弱的分离结晶作用;3)结合北祁连的区域构造演化、岩浆活动以及本区火山岩的年代学资料,认为该酸性火山岩可能处于由岛弧向弧后盆地过渡的环境中。