大兴安岭漠河砂金富集区岩金找矿思路

大兴安岭漠河地区砂金极为丰富,充分研究区内的地质构造特征、砂金分布和富集规律、区域剥蚀深度等,利用砂金信息寻找岩金是区内岩金找矿工作的有效手段之一.利用砂金矿只能寻找剥蚀残留的那一部分岩金矿.对物源区剥蚀程度和探矿构造分析研究,是在砂金富集区内圈定岩金找矿靶区的关键.溶蚀系数可指示砂金是近或远原生源金矿.Pb同位素可指示成矿母岩,利用矿石、岩浆岩、地层和基底铅同位素全方位对比来判别铅同位素的来源是一种近年来国际上认同的办法,砂矿评价中利用铅同位素寻找母岩已获得成功.本区砂金Pb同位素特征值与源区极为相似,可做为砂金富集区寻找岩金的指示元素.本文旨在论述砂金富集区内砂金与岩金空间位置关系、成因上的联系及岩金成矿特点,为下一步岩金找矿工作提供思路和方法.     

High-West and Low-East Distribution Patterns of Chlorophyll a, Primary Productivity and Diatoms in the Subarctic North Pacific Surface Waters, Midwinter 1996

We have determined chlorophyll a (Chla) concentration, primary productivity, cell density and species composition of diatoms, and the number of microzooplankton at the surface in the subarctic North Pacific in January 1996. The wet weight of copepods obtained by vertical tows from 150 m to the surface was also measured during the cruise. Chla concentration and primary productivity tended to be higher in the region west of 180°, the western subarctic North Pacific (WSNP), than east of 180°, the eastern subarctic North Pacific (ESNP). The same results were observed for the total diatom cell densities and for the genera Thalassiosira and Denticulopsis. Significant linear relationships were observed between the Thalassiosira cell density and Chla concentration and primary productivity, indicating that Thalassiosira contributes to the high-WSNP and low-ESNP distribution patterns of Chla concentration and primary productivity. Moreover, naked ciliate abundance tended to be lower in the WSNP than in the ESNP, whereas copepod biomass showed an inverse trend. Significantly negative Spearman rank correlations were found between the Thalassiosira cell density and the number of naked ciliates and between the number of naked ciliates and the wet weight of copepods. These results indicate that copepod grazing indirectly controls Thalassiosira cell density via predation on the naked ciliates. We conclude that the high copepod biomass in the WSNP is a factor controlling the high-WSNP and low-ESNP Thalassiosira abundance and hence Chla concentration and primary productivity patterns.     

湖北蛇屋山卡林型金矿地质及成因

蛇屋山金矿产于以寒武-奥陶系碳酸盐岩为主体的倒转背斜及双重逆冲构造中;矿床属低温热液成因(原生金矿);浅部矿体,即缓倾斜断层构造岩中的原生金矿,经历了第三纪以来近亿年的风化淋滤改造,成为可露采、易堆浸的风化金矿床;矿石品位低,金呈微细粒浸染状。与美国卡林型金矿类比,该矿属卡林型金矿。蛇屋山卡林型金矿分为原生金矿和风化金矿两个亚类。     

中小学避难建筑规划建设标准与容灾能力研究

已知避难建筑相较于场地型避难场所更有利于中长期避难,而目前我国城镇避难场所建设以场地型为主,建筑型避难场所存在严重不足。基于此,首先提出将中小学校舍建设为建筑型避难场所的重要性及可行性,并从空间利用角度对其可作为避难建筑的类型进行分析研究,指出中小学体育馆、食堂、宿舍和教室可建设为避难建筑;其次对我国城镇地区现状中小学校舍能够作为避难建筑的容灾能力进行分析,结果表明:现状满足100%的短期灾时避难人口的避难需求,以及满足60%的中长期灾时避难人口的避难需求;最后通过计算进行预测,可知随着城镇人口的增长,其所需的避难规模能够在日常城镇中小学校舍建设更新中逐步实现,大约需要未来20年时间基本可以实现中等规模灾害建筑型避难,大灾害长期避难能够满足100%的中长期灾时避难人口的避难需求,具有规划规模可实现性和可行性。     

西菲律宾海26万年来古生产力变化的颗石藻证据

基于国际海洋古全球变化研究项目(IMAGES)在西菲律宾海本哈姆海台获取的高质量柱状沉积物岩芯MD06-3047(17°00.44′N、124°47.93′E),利用颗石藻下透光带属种Florisphaera profunda的相对丰度以及初级生产力转换函数,恢复了260 ka以来西菲律宾海上部水体营养跃层以及初级生产力的变化历史。发现该区域26万年以来初级生产力冰期-间冰期变化特征较不明显,冰期生产力平均值略高于间冰期。通过与前人已发表的指示东亚冬季风强弱的伊利石/蒙脱石记录和热带太平洋纬向表层海水温度梯度记录的对比,提出MIS 8期以来,热带西菲律宾海古生产力变化的主要受控因素在MIS 5a左右发生明显转变。在MIS 8后期至MIS 5a之间,初级生产力受到长期类ENSO过程的影响较为显著,当热带东西太平洋海水表层温度梯度较小的时期,认为热带太平洋处于类El Niňo状态,此时西菲律宾海营养跃层相对较浅,生产力较高,反之则相反。而在MIS 5末期至末次冰消期时段,生产力受东亚冬季风的影响相对于长期ENSO过程更强,可能掩盖了后者的古生产力信号。冰期东亚冬季风加强,一方面,可以引起上部水体混合加强,增加下部营养物质向上的输送,另一方面大量风尘物质的输入可以刺激颗石藻的生长;反之在冰消期,水体混合较弱,风尘输入显著减少,生产力也随之降低。     

Phase stability and kinetics of methane hydrate formation in presence of calcium and magnesium carbonate

The huge amount of methane hydrate deposits identified in deep marine sediments is considered as the new resource for future energy. Since carbonates are one of the major components of marine sediments, in the present study, an investigation has been made to study methane hydrate stability and kinetics in the presence of CaCO₃ and MgCO₃. Effect of the presence of carbonates on the solubility of methane in the system has also been examined as it directly affects the hydrate formation process. It has been observed that in presence of CaCO₃ and MgCO₃, the hydrate formation is inhibited. Comparative studies have also been done in the presence of artificial seawater to consider the effect of presence of different salts. Mole consumption of methane gas during hydrate formation in different carbonate samples was measured using real gas equation and found to be minimum in CaCO₃ in seawater sample due to the combined effect of the presence of CaCO₃ and different salts of seawater. An increase in nucleation and induction time was also observed demonstrating the inhibition of hydrate formation in the presence of these components. Further, the decrease in hydrate formation rate also confirmed the inhibition effect of CaCO₃ and MgCO₃ on hydrate formation.     

基于奇异谱分析的深圳近海净初级生产力时间序列研究

海洋净初级生产力(Net Primary Productivity, NPP)长时间序列分析可获取NPP多年变化趋势、季节变化等动态信息,对海洋环境的监测与预报具有重要意义。本文以2003～2013年月际尺度净初级生产力卫星遥感产品为数据源,通过奇异谱分析提取标准化净初级生产力时间序列的长期趋势和周期振荡特征。研究表明,①浮标监测数据的叶绿素a浓度、海表温度与MODIS的叶绿素a浓度、海表温度产品变化趋势基本一致,NPP时间序列产品可用于分析深圳近岸海域净初级生产力的变化趋势。②空间分布上,深圳西部海域的NPP和叶绿素a浓度远高于大鹏湾和大亚湾,大鹏湾和大亚湾的NPP和叶绿素a浓度均值及变化趋势非常接近。三个海区NPP、叶绿素a浓度、海表温度和光合有效辐射在季风转换期变化剧烈。③长期趋势上,深圳西部海域呈现2 a周期波动趋势,在均值附近以年为周期上下波动。大鹏湾和大亚湾2003～2006年NPP低于平均水平, 2008年后NPP开始以年为周期围绕平均值上下波动, 2012年后NPP整体与均值持平。④周期特征上,深圳西部海域、大鹏湾和大亚湾的NPP呈"W"或"M"型周年变化,存在夏季主高峰(6～7月)和冬季次高峰(12～1月)。     

MIS 6期以来西菲律宾海表层营养物质水平演化及其控制因素:浮游有孔虫Globigerinoides ruber的Cd/Ca证据

通过西菲律宾海MD06-3052孔浮游有孔虫Globigerinoides ruber的n(Cd)/n(Ca)[n(Cd)和n(Ca)分别指示Cd元素和Ca元素的物质的量]变化研究及其与陆源物质输入、海水结构以及海洋初级生产力等重建结果对比,从营养物质来源和利用两方面,探究了MIS6期以来该区域表层营养物质水平演化及其控制因素,从而为热带西太平洋生物泵作用和营养物质循环提供新思路和新证据。MIS6期以及MIS 2—3期研究区吕宋岛来源的陆源物质输入增多,导致了研究区MIS 6晚期、MIS 3早期和MIS2期浮游有孔虫G. ruber n(Cd)/n(Ca)的升高。而在MIS 3晚期,尽管陆源物质输入量大、次表层营养物质上涌,但初级生产力对于营养物质的利用量大于前两者营养物质输入量之和,最终形成研究区浮游有孔虫G. ruber n(Cd)/n(Ca)在MIS 3晚期呈现逐渐降低的趋势。海平面的迅速升高导致营养物质来源短期不足引起MIS 6/5冰消期浮游有孔虫G. ruber n(Cd)/n(Ca)呈现低值。而MIS 5e期研究区陆源物质输入的增多,又促使浮游有孔虫G. ruber n(Cd)/n(Ca)出现高值。此外, MIS 4—5d期,陆源物质输入较低、次表层营养物质仍受到阻碍,但研究区初级生产力在MIS4—5d期则逐渐升高,致使研究区浮游有孔虫G.rubern(Cd)/n(Ca)呈现下降趋势。研究结果反映不同时期浮游有孔虫G.rubern(Cd)/n(Ca)的受控因素不同,需要对其从营养物质来源和利用两方面因素加以考虑,才能获得更为准确的研究结果。总之,本文对西菲律宾海浮游有孔虫n(Cd)/n(Ca)指标的探究,不仅为该指标在热带西太平洋区域的古海洋学研究打下了基础,还为该指标在其他海域更为准确的探究提供了新的思路。     

焦家金矿深部原生晕地球化学特征

焦家金矿是胶西北地区典型的金矿床,该区成矿具有多期、多阶段叠加共同作用的特点。通过对典型剖面上钻孔不同部位岩性样品的微量元素测试分析,运用数学地质分析方法,对焦家金矿床深部地球化学特征进行了研究,得出深部成矿微量元素特征组合为Au,Ag,Cu,Pb,Zn,As,Sb,Bi,Hg,W,Mo,Sn;原生晕轴向分带序列为:Hg,As,Sb(矿头晕)→Au,Ag,Cu,Pb,Zn,Bi,Sn(矿中晕)→W,Mo(矿尾晕)。由此建立了地球化学原生晕异常模型,并总结了地球化学找矿标志,为深部找矿提供依据。     

Nucleation and stabilization of Eocene dolomite in evaporative lacustrine deposits from central Tibetan plateau

In past decades, the formation of dolomite at low temperature has been widely studied in both natural systems and cultured experiments, yet the mechanism(s) involved in the nucleation and precipitation of dolomite remains unresolved. Late Eocene dolomitic deposits from core in the upper Niubao Formation (Lunpola Basin, central Tibetan Plateau, China) are selected as a case study to understand the dolomitization process(es) in the geological record. Dolomite formation in Lunpola Basin can be ascribed to a different mechanism forming the large quantities of replacive dolostones in the geological record; and provides a potential fossil analogue for primary dolomite precipitation at low temperature. This analogue consists of an alternation of laminated dolomitic beds, organic-rich and siliciclastic layers; formed in response to intense evaporation interpreted to take place in a continental shallow lake environment. Mineralogical, textural and stable isotopic evaluations suggest that the dolomite from those dense-clotted laminated beds is a primary precipitate. At the nanoscale, these dolomitic beds are composed of Ca–Mg carbonate globular nanocrystals (diameter 80 to 100 nm) embedded in an organic matrix and attached to clay flakes. Micro-infrared spectroscopy analyses have revealed the presence of aliphatic compounds in the organic matrix. Microscopic and elemental compositional studies suggest that clay surfaces may facilitate the nucleation of dolomite at low temperature in the same way as the organic matrix does. The dolomite laminae show values for δ¹⁸O_VPDB from −3.2 to −1.76‰ and for δ¹³C_VPDB from −2.62 to −3.78‰. Inferred δ¹⁸O_SMOW values of the lake water reveal typical evaporitic hydrological conditions. These findings provide a potential link to primary dolomite formation in ancient and modern sedimentary environments; and shed new light on the palaeoenvironmental conditions in central Tibet during the Eocene.