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21.
山东省渤海沿岸湿地价值估算的目的是提醒公众尤其是政府决策部门关注湿地的综合功能,而不是也不应该单纯向湿地索取,更不能破坏性地开发,需要科学保护和合理利用,以使湿地可持续利用。通过分析湿地动态影响因素,提出了湿地保护管理的对策措施。  相似文献   
22.
山东省渤海沿岸湿地价值估算的目的是提醒公众尤其是政府决策部门关注湿地的综合功能,而不是也不应该单纯向湿地索取,更不能破坏性地开发,需要科学保护和合理利用,以使湿地可持续利用。通过分析湿地动态影响因素,提出了湿地保护管理的对策措施。  相似文献   
23.
The Neoproterozoic Tonian strata(ca.870-725 Ma)in the western Jiangnan Orogen archive the records of sedimentary provenance and tectonic setting which can be used to understand the geological evolution of the South China Continent.These strata are separated into the basement and cover sequences by a regional angular unconformity.The basement sequence can be subdivided into the lower and the upper parts by the widespread interbedded ca.840 Ma basalt with pillow structure.In the present work,234 concordant detrital zircon analyses are obtained from three Tonian sandstone samples in the Fanjingshan district,Guizhou Province.Combined with previous results,a total of 1736 analyses of detrital zircon U-Pb ages derived from 12 formations of Tonian strata in the western Jiangnan Orogen are used to decipher the integrated sedimentary and tectonic histories.The zircons from the lowermost part of the basement sequence(the Yujiagou Formation)show oval morphology and display two Paleoproterozoic age peaks at 2325 Ma and 1845 Ma which are similar with the detrital zircon age peaks from the Late Paleoproterozoic to Early Mesoproterozoic Dongchuan/Dahongshan/Hekou groups,suggesting a passive margin basin in which the sediments were mainly sourced from the southwestern Yangtze Block.However,the zircon age population of the lower part of the basement sequence(the Xiaojiahe,Huixiangping formations and their equivalents)indicates the sedimentary derivation from bidirectional sources(the ca.870 Ma arc materials in the south and the old detritus from the southwestern Yangtze Block)which is consistent with a back arc setting for the deposition of the sediments.Zircons from the upper part of the basement sequence(the Duyantang Formation and its equivalent)show euhedral and subangular morphology and display a unimodal age peak at ca.835 Ma.This sequence was possibly deposited in a convergent setting and the detritus were came from the locally distributed syn-collisional igneous rocks.The lower part of the cover sequence(the Xinzhai and Wuye formations and their equivalents)shows a distinct zircon age peak at 815—809 Ma and two subordinate peaks at 2485 Ma and 2018 Ma,suggesting that the basin had gradually transformed into a continental rift basin and received the detritus from the ca.815 Ma post-collisional magmatic rocks as well as from different Paleoproterozoic source rocks in the northern Yangtze Block.We propose a tectonic evolution model that envisages eruption of ca.840 Ma basalt in a back arc basin that existed during ca.870-835 Ma,an angular unconformity was formed during amalgamation of the Yangtze Block and the Cathaysia Block at ca.835-820 Ma and the rifting of the South China Continent was initiated at ca.800 Ma.Our study concludes that the South China Continent was formed on the periphery of the Rodinia supercontinent.  相似文献   
24.
龙泉关韧性剪切带由五台期韧性剪切带和吕梁期韧性剪切带复合而成,五台期韧性剪切带形成于低角闪岩相环境下,吕梁期韧性剪切带形成于绿片岩相环境下。两期韧性剪切带对五台期和吕梁期变质建造具有明显的控制作用,并部分地改造了阜平期变质岩。  相似文献   
25.
实验研究表明,不同厚度的醋酸纤维探测经铀α面源照射蝗,其径迹密度与照射时间有很好的相关性;探测片的本底值不会影响其观测结果;径迹的镜下特征与不同照射角度下的特征径迹变化,是照射角度愈接近直角,圆形特征径迹越多,其它形状的径迹越少;在同一观测孔中探测片采用垂直与平行和悬吊三种方式照射,探测到的氡浓度含量相同,观测工线基本吻合;探测片在不同的环境条件下蚀刻其径迹大小不同,目前我省统一使用的醋酸纤维探测  相似文献   
26.
Auriferous quartz veins in the Bankuan gold deposit occur in the interlayer broken zone of the basal conglomerate of the Tietonggou Formation or at the unconformity between the Tietonggou Formation and the crystalline basement.The composition of fluid inclusions in the minerals indicates that the nature and composition of ore-forming hydrothermal solutions show a drastical change soon after the solutions reached the Tietonggou Formation from the crystalline basement,resulting in gold precipitation.So the Bankuan gold deposit can be assigned to the conglomerate stata-bound-type deposits.137 thermometric data are concentrated in the three ranges 400-340℃,330-220℃ and 180-160℃,representing three episodes of metalogenesis,Oxygen isotope studies demonstrate the evolution of ore-forming hydrothermal solutions from early metamorphic to late meteoric,Diversity of ore-forming materials dominated by deep-source material is supported by sulphur and lead isotope data.From the above discussions it may be concluded that the deposit formed by metamorphism induced as a result of Mesozoic northward intracontinental subduction along the Machaoying fault.  相似文献   
27.
A 3-D coastal ocean model with a tidal turbine module was used in this paper to study the effects of tidal energy extraction on temperature and salinity stratification and density-driven two-layer estuarine circulation. Numerical experiments with various turbine array configurations were carried out to investigate the changes in tidally averaged temperature, salinity, and velocity profiles in an idealized stratified estuary that connects to coastal water through a narrow tidal channel. The model was driven by tides, river inflow, and sea surface heat flux. To represent the realistic size of commercial tidal farms, model simulations were conducted based on a small percentage (less than 10 %) of the total number of turbines that would generate the maximum extractable energy in the system. Model results show that extraction of tidal in-stream energy will increase the vertical mixing and decrease the stratification in the estuary. Installation of in-stream tidal farm will cause a phase lag in tidal wave, which leads to large differences in tidal currents between baseline and tidal farm conditions. Extraction of tidal energy in an estuarine system has stronger impact on the tidally averaged salinity, temperature, and velocity in the surface layer than the bottom layer even though the turbine hub height is close to the bottom. Finally, model results also indicate that extraction of tidal energy weakens the two-layer estuarine circulation, especially during neap tides when tidal mixing is weakest and energy extraction is smallest.  相似文献   
28.
随着苏里格气田的深度开发,大井丛、三维水平井施工逐渐增多,增大了轨迹控制难度。丛式三维水平井存在防碰风险高,斜井段长导致摩阻和扭矩大滑动钻进困难,水平段长及产层不稳定导致钻压传递困难和井壁失稳、井壁清洁困难等问题。针对这些问题,通过优化剖面设计和钻具组合,采用盐水钻井液体系、螺杆优选及现场技术管理和操作人员精心应对,形成了配套的技术对策,有效地实现了钻井工程的安全高效。  相似文献   
29.
豫西卢氏八宝山铁铜多金属矿床是华北克拉通南缘中生代斑岩成矿体系中以铁矿化为主的矿床,其中南矿带和西矿带广泛发育黄铁矿。电子探针成分显示,黄铁矿的主要元素S和Fe的总和超过90%,但同一种黄铁矿表面不同位置微量元素Cu和As的含量存在突变。这种突变说明,来源于同一岩浆热液系统的富液相流体与上升的富气相流体的混合作用是引起黄铁矿沉淀的主要机制。黄铁矿中的As有两种赋存价态As3+和As1–,代表了八宝山斑岩矿床中形成黄铁矿的岩浆流体可能经历了先氧化后还原的环境(As3+指示氧化环境,As1–指示还原环境),说明八宝山矿区具有斑岩铜矿的成矿潜力。  相似文献   
30.
Chalcopyrite is an important sulfide mineral in many types of ore deposits, but matrix‐matched chalcopyrite reference materials for microanalysis are lacking. A new natural chalcopyrite‐bearing specimen (HTS4‐6) was analysed in this study to investigate its potential as a reference material for microbeam sulfur isotope ratio measurement. Detailed textural examination and major element determination showed that the HTS4‐6 chalcopyrite grains have no growth rim or zoning. A total of 607 sulfur isotope ratio spot measurements with secondary ion mass spectrometry (SIMS) conducted on the cruciform sections, and over 120 randomly selected grains yielded highly consistent sulfur isotope ratio. The intermediate measurement precision for four measurement sessions of the 34S/32S measurement results was better than 0.39‰ (2s). Randomly selected chalcopyrite grains of HTS4‐6 were further analysed by LA‐MC‐ICP‐MS, which gave a mean δ34S value of +0.58 ± 0.38‰ (2s, n = 95). The maximum variance (expressed as intermediate precision from SIMS and LA‐MC‐ICP‐MS measurements) is not worse than 0.39‰ (the SIMS value), indicating that HTS4‐6 chalcopyrite is a potential reference material for in situ microbeam sulfur isotope measurements. The mean δ34S value determined by gas source isotope ratio mass spectrometry (GS‐IRMS) is +0.63 ± 0.16‰ (2s, n = 23), consistent with that derived by LA‐MC‐ICP‐MS, and can represent the recommended value for this potential reference material.  相似文献   
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