Tracing the protolith, UHP metamorphism, and exhumation ages of orthogneiss from the SW Sulu terrane (eastern China): SHRIMP U–Pb dating of mineral inclusion-bearing zircons     

Fulai Liu  Zhiqin Xu  Huaimin Xue 《Lithos》2004,78(4):411-429

Orthogneisses are the major country rocks hosting eclogites in the Sulu UHP terrane, eastern China. All of the analyzed orthogneiss cores from the main drilling hole of the Chinese Continental Scientific Drilling Project (CCSD-MH) have similar major and trace element compositions and a granite protolith. These rocks have relatively high LREE/HREE ratios, strong negative Eu anomalies (Eu/Eu*=0.20–0.39), and negative Ba anomalies (Ba/Ba*=0.25–0.64). Coesite and coesite-bearing UHP mineral assemblages are common inclusions in zircons separated from orthogneiss, paragneiss, amphibolite, and (retrograded) eclogite of the CCSD-MH. This suggests that the eclogite, together with its country rocks, experienced in situ ultrahigh-pressure (UHP) metamorphism. Laser Raman spectroscopy and cathodoluminescence (CL) images show that zircons from the orthogneisses are zoned and that they have distinct mineral inclusions in the different zones. Most zircons retain early magmatic cores with abundant low-pressure mineral inclusions, which are mantled with metamorphic zircon-containing inclusions of coesite and other UHP minerals. The outermost rims on these grains contain low-pressure mineral inclusions, such as quartz and albite. SHRIMP U–Pb dating of the zoned zircons gives three discrete and meaningful groups of ages: Proterozoic ages for the protolith, 227±2 Ma for the coesite-bearing mantles, and 209±3 Ma for the amphibolite facies retrograde rims. The widespread occurrence of UHP mineral inclusions in zircons from the Sulu metamorphic belt dated at about 227 Ma suggests that voluminous continental crust experienced late Triassic subduction to depths of at least 120 km and perhaps more than 200 km. Eighteen million years later, the terrane was rapidly exhumed to midcrustal levels, and the UHP rocks were overprinted by amphibolite facies metamorphism. The exhumation rate deduced from the zircon age data and previously obtained metamorphic P–T data is estimated to be 5.6–11.0 km/Ma. Such rapid exhumation of the Sulu UHP terrane may be due to the buoyancy forces produced by subduction of low-density continental material into the deep mantle.  相似文献   

金坛市开发区的数字影像测图     

王立兴  薛炜  王训霞 《现代测绘》2004,27(3):41-42

为完善数字化测图功能，通过全数字摄影测量系统(VirtuoZo)的数字影像测图模块(IGS)在金坛市开发区1：500测区中的应用，总结提高测图精度和速度的体会。  相似文献   

西安市冬季冷暖的历史演变对采暖的影响          下载免费PDF全文

庞文保 《山西气象》2005,(3):27-28

本文针对CAPPS2.0系统在业务化自动运行过程中的一些问题,提供了一套具体可行的解决方案,实现了CAPPS系统的全自动运行,具有很高的实用价值。  相似文献   

侯马市酸雨概况及其气象条件分析          下载免费PDF全文

薛廷枝  王智娟  史海平  张红安  贾海燕 《山西气象》2005,(4):14-15

通过对侯马近14a酸雨观测资料分析,发现侯马出现酸雨的概率较大,强度较强,时间变化特征明显,与气象条件关系密切。  相似文献   

Correlation between magnetic susceptibility and heavy metals in urban topsoil: a case study from the city of Xuzhou, China   总被引：7，自引：0，他引：7  

Xue Song WANG  Yong QIN 《Environmental Geology》2005,49(1):10-18

Anthropogenic influence, mainly due to urban and industrial activities and traffic exhaust, may affect urban topsoil via atmospheric contamination and solid waste. Magnetic susceptibility measurements were conducted on 21 urban topsoil samples from the city of Xuzhou, China. High intensities of magnetic susceptibility were detected in the majority of the samples. SEM analysis shows that magnetic minerals are in the form of spherules and mainly due to anthropogenic inputs. The heavy metals Pb, Cu, Zn, Se, Sc, Mo, Fe, and Bi show strong correlations with magnetic susceptibility, and Ag, Ba, Cd, Ni, Cr, Sb, and Sn, on the other hand, show a weak correlation with magnetic susceptibility. Whereas, of these metals studied, only Hg has no significant correlation with the susceptibility. The Tomlinson pollution load index (PLI) also shows significant correlation with the susceptibility (χ). The present study shows that magnetic susceptibility is a fast, inexpensive, and non-destructive method for the detection and mapping of contaminated soils.  相似文献   

Element mobility during pyrite weathering: implications for acid and heavy metal pollution at mining-impacted sites   总被引：1，自引：0，他引：1  

Long Lu  Rucheng Wang  Fanrong Chen  Jiyue Xue  Peihua Zhang  Jianjun Lu 《Environmental Geology》2005,49(1):82-89

Based on back scattered electron images and electron micro-probe analysis results, four alteration layers, including a transition layer, a reticulated ferric oxide layer, a nubby ferric oxide layer and a cellular ferric oxide layer, were identified in the naturally weathering products of pyrite. These layers represent a progressive alteration sequence of pyrite under weathering conditions. The cellular ferric oxide layer correlates with the strongest weathering phase and results from the dissolution of nubby ferric oxide by acidic porewater. Leaching coefficient was introduced to better express the response of element mobility to the degree of pyrite weathering. Its variation shows that the mobility of S, Co and Bi is stronger than As, Cu and Zn. Sulfur in pyrite is oxidized to sulfuric acid and sulfate that are basically released into to porewater, and heavy metals Co and Bi are evidently released by acid dissolution. As, Cu and Zn are enriched in ferric oxide by adsorption and by co-precipitation, but they would re-release to the environment via desorption or dissolution when porewater pH becomes low enough. Consequently, Co, Bi, As, Cu and Zn may pose a substantial impact on water quality. Considering that metal mobility and its concentration in mine waste are two important factors influencing heavy metal pollution at mining-impacted sites, Bi and Co are more important pollutants in this case.  相似文献   

海水温度对衰亡期浒苔释放生源硫影响的模拟研究   总被引：1，自引：0，他引：1  

韩露  邓雪  李培峰  高先池  刘春颖 《海洋学报》2018,40(10):110-118

为研究浒苔释放生源硫的特征，本文对采集于黄海绿潮中期和末期的浒苔进行了实验室模拟培养，探讨了不同温度对衰亡期浒苔释放生源硫化物的影响。实验结果表明，在10~25℃温度范围内，温度升高能够加速浒苔的衰亡。二甲基硫（DMS）的平均释放速率范围为2.79~150.70 nmol/（L·g·d），二甲基硫基丙酸内盐（DMSP）的平均释放速率范围为2.16~113.26 nmol/（L·g·d）。温度升高能够使DMS和DMSP的释放速率加快，释放量增加，DMS最大平均释放速率在25℃条件下比10℃条件下升高了约60%，培养液中DMS浓度升高了2~3倍。采集于绿潮末期的浒苔培养液中的DMS和DMSP和采集于绿潮中期的浒苔相比，浓度有所增加，采集于浒苔绿潮末期浒苔培养液中DMS的最高平均浓度为418.41 nmol/L，约为中期的4倍；DMSP的最高平均浓度为316.14 nmol/L，是中期的3倍。浒苔绿潮的爆发会对水体中的硫体系循环产生影响，进而影响该海域生态环境。  相似文献   

Instantaneous Shorelines as an Intermediate for Island Shoreline Mapping based on Aerial/Satellite Stereo Images     

Yamin Dang  Xinghua Zhou  Jun Xu  Shuqiang Xue 《Marine Geodesy》2018,41(3):219-229

Island shoreline mapping based on field measurements by collecting visually discernible features is costly and even unrealistic to be implemented in practice because of the nonuniqueness, fuzziness, and ambiguity of shoreline features. The MHHW (the mean higher high water) shoreline, i.e., the intersection of the coastal profile with the MHHW, is recommended to be chosen as a significant shoreline indicator of an island. An approach for mapping the MHHW shoreline using the aerial/satellite stereo images is proposed. In the proposed procedure, first, the height difference between the instantaneous shoreline and the MHHW shoreline is calculated by the ocean tide model; then the orthometric/normal height of the instantaneous shoreline is determined from the stereo images; last, the instantaneous shoreline is used as an intermediate for determination of the height of the MHHW shoreline. The proposed procedure is applied to the MiaoZiHu Island located in the East China Sea. Preliminary experimental result shows that in ideal cases, the horizontal positional accuracy of the extracted shoreline can reach 0.2 m from aerial images of 0.1 m resolution.  相似文献   

Small-scale natural disaster risk scenario analysis: a case study from the town of Shuitou,Pingyang County,Wenzhou, China     

Yaolong Liu  Guorui Feng  Ye Xue  Huaming Zhang  Ruoguang Wang 《Natural Hazards》2015,75(3):2167-2183

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近岸海域大型水母来源与迁移路径分析——以红沿河电厂海域为例     

孙雪  魏皓  张海彦  王彦涛  张广跃  刘汉霖 《海洋与湖沼》2019,50(6):1281-1291

近岸海域水母暴发可导致滨海火/核电厂取水口堵塞,对电厂安全运行造成潜在威胁。寻找水母源地及其迁移路径是水母治理的基础。本文基于拉格朗日质点追踪方法(LTRANS)建立反向追踪模型,并结合水母生态学特性对2015年6—9月聚集在红沿河电厂海域的大型水母进行溯源,获得水母源地及迁移路径,可以为螅状体栖息地寻找和水母拦截打捞提供依据,对近岸海域水母灾害防治具有重要指导意义。溯源结果表明:(1)红沿河电厂及其邻近海域的水母可能来自多个不同源区,辽东湾西部、北部及电厂南北两侧等海域的水母均有可能迁移至电厂附近;(2)受水温和环流影响,6—9月期间到达电厂附近的水母主要源区及迁移路径不同,早期出现在电厂海域的水母很可能是局地产生的,而7—9月持续的高风险水母灾害则主要取决于渤海不同源区水母的物理聚集;(3)根据水母的主要迁移路径,建议在电厂取水口约15km的海域设置一条封闭监测断面,对水母进行实时监测;在距离取水口约30km的外侧海域设置一条调查断面,于7月初至8月中旬,每5天进行一次定点拖网调查。此外,在距离电厂取水口15—20km的西南方向上,对水母进行拦截打捞可大大降低水母入侵风险。  相似文献