南大洋普里兹湾沉积物中生物硅的溶解度研究          下载免费PDF全文

扈传昱  孙维萍沈忱 张海生 《极地研究》2012,24(4):339-345

本文利用中国南极科学考察航次获得的沉积物样品,采用分批（batch）实验方法,获取实验室生物硅溶解度,并结合间隙水中可溶性硅剖面,对普里兹湾沉积物中生物硅的溶出过程进行了初步研究。研究结果如下：在25℃,pH 8条件下,普里兹湾IV-10、 IS-4站表层沉积物中生物硅的实验室溶解度分别为1936、1539μmol/dm3,不同层次沉积物溶出结果显示随深度增加溶解度值降低。根据实验室溶解度数据与间隙水硅酸盐Cd的分析比较,表明研究站位沉积物生物硅的早期成岩过程中生物硅的溶出还伴随有其他化学过程。  相似文献   

延迟交联凝胶研制及其在广西某铀矿堵漏应用          下载免费PDF全文

熊正强  陶士先  刘俊辉  李晓东  薛倩冰 《探矿工程》2020,47(4):140-144

针对地质钻探小井眼条件下失返性漏失堵漏技术难题,开展了适用于地质钻探堵漏要求的聚合物交联凝胶研究。采用单因素优选法,优选了交联凝胶体系用各种处理剂,并以环保型植物胶GJ为成胶剂,加入交联控制剂N1及交联剂1号等组分,研制了一种延迟交联凝胶。该凝胶在广西某铀矿勘查ZK6-37-1孔堵漏成功应用,解决了2个孔段失返性漏失问题。研究结果表明,该凝胶具有交联时间可控(交联时间10～75 min)以及较高的凝胶强度（承压≥6 MPa）,在解决失返性漏失方面具有广阔的应用前景。  相似文献   

秦岭造山带多金属矿普查复杂地层护壁堵漏技术          下载免费PDF全文

柳硕林  韩明耀 《探矿工程》2020,47(1):43-47

秦岭造山带多金属矿普查项目钻探施工过程中钻遇多种复杂地层,垮塌、缩径、漏失等复杂情况频发,严重影响了施工效率。分别采用了植物胶钙处理钻井液、聚乙烯醇无固相钻井液等进行护壁工作,结合不同漏失情况分别实施了随钻堵漏、凝胶堵漏等技术措施,取得了良好的使用效果。  相似文献   

Decadal and seasonal changes in landcover at Padre Island: Implications for the role of the back-barrier in signaling island state change     

Kenton R. Fisher  Ryan C. Ewing  Orencio Duran Vinent 《地球表面变化过程与地形》2023,48(1):163-178

Long-term and seasonal geomorphological changes at Padre Island, Texas are identified and linked with potential external drivers. Aerial and satellite images from 1950 to 2018, monthly images from 2019 to 2020, and a 2018 LiDAR data set are used to assess long-term and seasonal geomorphological changes within a 50 km² area of Padre Island near Port Mansfield, Texas. Trends in landcover are evaluated by mapping and comparing the relative areal coverage of each facies. Vegetated dunes, absent initially, emerged in the fore-island and expanded into the back-barrier to cover 14% of the study area. The active vegetation-free back-barrier dune field steadily decreased in areal extent from 12% to 6% as vegetation spread. Nebkha dune coverage fluctuated between 4% and 7%. Expansive microbial mats colonized the wind tidal and deflation flats surrounding the vegetated dunes and back-barrier dune field giving rise to a remarkably different landscape over the 50-year period studied. An assessment of external forcing factors identifies increased rates of relative sea level rise and decreased sediment influx as the most likely primary factors driving the geomorphological changes. These changes have induced a widespread shift toward stabilization of island sediments by vegetation and microbial mats, which in turn has starved the back-barrier of sediments resulting in low rates of accretion and increased flooding. These findings highlight the sensitivity of the back-barrier and, in particular, the dune facies to changes in sea level and sediment supply, and show that microbial mats are effective at stabilizing island sediments and may be harbingers to barrier island response to rising sea level. As shown in this study, long-term monitoring of geomorphic facies changes and topography can detect important shifts in the island state that can be used to inform decision making for these sensitive coastal landscapes.  相似文献   

硅灰加固宁波软土的试验研究     

王泽平  王常明  江南  张在恒 《岩土工程技术》2020,(2):111-116,121

为探索硅灰对软土的力学性质的影响,以宁波鄞州地区一种淤泥质黏土为试样,掺入不同量的硅灰,对硅灰加固土的力学性质和结构特征进行了测试。采用三轴不固结不排水剪切试验,测试分析了不同掺入量的硅灰加固土的应力应变关系,通过扫描电镜SEM照片分析了不同硅灰掺入量的硅灰加固土的结构特征。结果表明:(1)硅灰可以提高软土的黏聚力,黏聚力随着硅灰掺入量的增加而增大;(2)随着硅灰掺入量的增加,硅灰加固土的抗变形能力呈先增加后减小的趋势;(3)同一围压条件下,随着硅灰掺入量的增加,硅灰加固土的破坏偏应力逐渐增加;(4)随着硅灰掺入量的增加,硅灰加固土中大孔隙逐渐减少,小孔隙逐渐数量增加,孔径<1μm的小孔隙组分逐渐占优。  相似文献   

Crystallization pathways in the Great Artesian Basin (Australia) spring mound carbonates: Implications for life signatures on Earth and beyond     

Fulvio Franchi  Silvia Frisia 《Sedimentology》2020,67(5):2561-2595

Recent studies of continental carbonates revealed that carbonates with similar fabrics can be formed either by biotic, biologically-induced, biologically-influenced or purely abiotic processes, or a combination of all. The aim of this research is to advance knowledge on the formation of carbonates precipitated (or diagenetically altered) in extreme, continental environments by studying biotic versus abiotic mechanisms of crystallization, and to contribute to the astrobiology debate around terrestrial analogues of Martian extreme environments. Both fossil (upper Pleistocene to Holocene) and active carbonate spring mounds from the Great Artesian Basin (South Australia) have been investigated. These carbonates consist of low-Mg to high-Mg calcite tufa. Four facies have been described: (i) carbonate mudstone/wackestone; (ii) phytohermal framestone/boundstone; (iii) micrite boundstone; and (iv) coarsely crystalline boundstone. The presence of filaments encrusted by micrite, rich in organic compounds, including ultraviolet-protectants, in phytohermal framestone/boundstone and micrite boundstone is clear evidence of the existence of microbial mats at the time of deposition. In contrast, peloidal micrite, despite commonly being considered a microbial precipitate, is not directly associated with filaments in the Great Artesian Basin mounds. It has probably formed from nanocrystal aggregation on colloid particulate. Thus, where biofilms have been documented, it is likely that bacteria catalyzed the development of fabrics. It is less certain that microbes induced calcium carbonate precipitation elsewhere. Trace elements, including rare earth element distribution from laminated facies, highlight strongly evaporative settings (for example, high Li contents). Carbon dioxide degassing and evaporation are two of the main drivers for an increase in fluid alkalinity, resulting in precipitation of carbonates. Hence, although the growth of certain fabrics is fostered by the presence of microbial mats, the formation of carbonate crystals might be independent from it and mainly driven by extrinsic factors. More generally, biological processes may be responsible for fabric and facies development in micritic boundstone whilst micrite nucleation and growth are driven by abiotic factors. Non-classical crystallization pathways (aggregation and fusion of nanoparticles from nucleation clusters) may be more common than previously thought in spring carbonate and this should be carefully considered to avoid misinterpretation of certain fabrics as by-products of life. It is proposed here that the term ‘organic-compound catalyzed mineralization’ should be used for crystal growth in the presence of organic compounds when dealing with astrobiological problems. This term would account for the possibility of multiple crystallization pathways (including non-classical crystallization) that occurred directly from an aqueous solution without the direct influence of microbial mats.  相似文献   

福建北部近岸东台山岛火山岩形成时代、地球化学与古太平洋板块俯冲的响应          下载免费PDF全文

王飞飞  张勇  韩宗珠  宋维宇  吴浩  宁泽 《中国地质》2020,47(5):1426-1437

福建北部沿岸岛屿岩石组合以晚中生代火成岩为主,研究认为是古太平洋俯冲消减的产物,对反演洋盆构造演化具有重要的指示意义。本次对其中的福建北部海域东台山岛上广泛发育的酸性火山岩进行了锆石U-Pb定年以及全岩主微量地球化学分析工作。2件年代学样品分别获得了92 Ma和86 Ma的锆石U-Pb年龄,确定东台山岛火山岩形成于晚白垩世。全岩地球化学特征指示火山岩样品以酸性钙碱性岩石为主,整体富集Rb、Ba等元素,亏损Nb、Ta、Sr、Eu等元素,显示弧型岩浆岩的地球化学组成。研究认为东台山岛火山岩起源于古老下地壳变沉积岩熔融,并在浅层岩浆房内经历了不同程度的结晶分异过程。结合区域上晚中生代岩浆作用由陆向海的时空迁移特征,福建北部沿岸岛屿火山岩形成的深部动力学机制应该与古太平洋俯冲过程中的板片回转过程相关。  相似文献   

The silica supersaturated waters of northern Evia and eastern central Greece     

G. Stamatis  E. Gartzos 《水文研究》1999,13(17):2833-2845

The area of north Evia and eastern central Greece is characterized by strong geomorphological contrast and is built up mainly of consolidated rocks. Unconsolidated young sediments of Pleistocene to Holocene age cover the valley and basin flats, forming the most productive aquifers in this area. However, two more types of aquifers can be distinguished within the consolidated rock area. The first one is associated with karstified limestones and the second with strongly tectonized ultramafic rocks. The schist–chert formation, with intercalations of shales and cherts, seals the ultramafic masses underneath. Surface and spring waters associated with ultramafic rocks in north Evia and eastern central Greece were studied. Two types of water can be distinguished: (1) high Mg²⁺ and SiO₂ , bicarbonate as the dominant anion, pH 7·4–9·2, temperature 9·5–16·3 °C, low TDS (total dissolved solutes) (459–1037 mg/l), found both in peridotite and serpentinite areas, classified as Mg–HCO₃ type; (2) high Ca²⁺, low Mg²⁺ and SiO₂ , hydroxyl ion as the major anion, pH 11·2, temperature 28 °C, very low TDS (122 mg/l), found in peridotite areas, classified as Ca–OH type. The studied waters are highly supersaturated with respect to quartz, amorphous silica, brucite and most low temperature magnesium silicates (antigorite, sepiolite, talc, etc.). These waters show relatively narrow SiO₂ concentration ranges and a trend parallel to the amorphous silica saturation surface. The silica supersaturated waters have the potential to precipitate silica and consequently could affect the people of the local communities that use it as drinking water, causing health problems (kidney stones). Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

海洋沉积物32 Si测年方法研究     

詹晓青  李超  贾磊  张金鹏  刘广山 《海洋学报》2019,41(2):63-74

天然32Si是宇宙射线成因的，随着降水进入湖泊或海洋，被硅质生物摄取后最终存在于生物硅中。32Si来源单一，生产速率相对恒定，半衰期为150 a，可测年的时间尺度为100~1 000 a，是该时间尺度最合适的测年核素，填补了百年到千年时间尺度测年方法的空白。本文建立了海洋沉积物32Si的测量方法，主要步骤为:（1）样品前处理；（2）生物硅的分离与纯化；（3）生物硅样品中磷的分离与纯化；（4）32P的制样与β计数测量。全程通过硅钼蓝和磷钼蓝分光光度法监测实验过程硅和磷的损失情况，对南沙海域采集的沉积物岩心进行研究，得到南沙海域沉积物岩心32Si的平均活度为16.60 mBq/kg，范围值为8.39~33.34 mBq/kg；32Si在SiO₂中的平均比活度为0.356 Bq/kg，32Si的核素丰度平均值为1.29×10-16（32Si/SiO₂）；根据岩心32Si活度估算得深水区（水深1 335~1 537 m）和浅水区（121~141 m）岩心的沉积速率分别为0.106 cm/a、0.191 cm/a；根据32Si活度计算32Si的平均沉降通量为2.14×10-6 Bq/（cm2·a），与参考文献的结果较为吻合。  相似文献   

Interaction of Freshly Precipitated Silica Gel with Aqueous Silicic Acid Solutions under Ambient and Near Neutral pH-conditions: A Detailed Analysis of Linear Rate Law     

Jiří Faimon  Martin Blecha 《Aquatic Geochemistry》2008,14(1):1-40

Interaction of freshly precipitated silica gel with aqueous solutions was studied at laboratory batch experiments under ambient and near neutral pH-conditions. The overall process showed excellent reversibility: gel growth could be considered as an opposite process to dissolution and a linear rate law could be applied to experimental data. Depending on the used rate law form, the resulting rate constants were sensitive to errors in parameters/variables such as gel surface area, equilibrium constants, Si-fluxes, and reaction quotients. The application of an Integrated Exponential Model appeared to be the best approach for dissolution data evaluation. It yielded the rate constants k _dissol ∼ (4.50 ± 0.68) × 10⁻¹² and k _growth ∼ (2.58 ± 0.39) × 10⁻⁹ mol m⁻² s⁻¹ for zero ionic strength. In contrast, a Differential Model gave best results for growth data modeling. It yielded the rate constants k _dissol ∼ (1.14 ± 0.44) × 10⁻¹¹ and k _growth ∼ (6.08 ± 2.37) × 10⁻⁹ mol m⁻² s⁻¹ for higher ionic strength (I ∼ 0.04 to 0.11 mol L⁻¹). The found silica gel solubility at zero ionic strength was somewhat lower than the generally accepted value. Based on the and standard Gibbs free energy of silica gel formation was calculated as and −850,318 ± 20 J mol⁻¹, respectively. Activation energies for silica gel dissolution and growth were determined as and respectively. An universal value for growth of any silica polymorph, is not consistent with the value for silica gel growth, which questions the hypothesis about one unique activated complex controlling the silica polymorph growth.  相似文献