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1.
On the contiguous territories of southeastern Russia and northeastern China,many gold-bearing areas are conjugate in space with the gradient zones of the gravity field.Large gold-ore districts,defining in many respects the metallogenic signature of the region,are located on the joints of differently oriented gradient zones.In the best-studied districts,the Precambrian protrusions,staged distribution of magmatic chambers (by vertical) above the Mohorovicic discontinuity and restriction to the peripheral parts of intrusive massifs have been recognized.Different-type gold deposits in the studied ore-placer districts and nodes are often located on the areas of joint of the granitoid massifs and subvolcanic bodies with depressions.Availability of areals of metasomatic alterations of rocks,placers,and ore occurrences of precious metals on such but poorly studied areas can serve as the basis for the revision and detailed forecasting-prospecting works to develop the mineral-raw material base of the region for precious metals.  相似文献   

2.
城市化进程的加快对区域热环境具有重要影响,热环境的改变会引发一系列生态环境问题,科学地评价城市群热环境安全对于城市发展的规划布局和建设舒适的人居环境具有重要意义。本文利用多期MODIS地表温度数据产品,在构建热环境安全等级分级标准的基础上,对长江三角洲城市群热环境安全格局时空变化特征和土地利用变化的影响进行了探讨。结果表明：① 2015年长江三角洲城市群热环境不安全区域多分布于城市建成区及建成区周围,以南京、上海、杭州和宁波等城市形成的“Z”型区域最明显,临界安全区域多分布于郊区,较安全区域集中分布于长江以北平原区域,安全区域则主要分布于杭州及杭州以南山地、丘陵区,太湖大部分区域以及长江三角洲城市群北部区域;② 2005-2015年长江三角洲城市群热环境不安全区域、临界安全区域、较安全区域和安全区域分别呈现扩张、小幅增长、缩减和先缩减后扩张趋势;③ 土地利用结构中建设用地比例过高和林地比例过低是导致热环境安全等级下降的主要原因,其次,建设用地侵占大量耕地也是导致热环境不安全区域扩张的主要原因。  相似文献   

3.
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4.
本文对松原5.7级地震前地磁垂直分量日变化低点时间时空演化特征进行研究，结果显示：1）以去除经度效应后低点时间为0 h的等值线作为低点位移分界线，松原5.7级地震的震中分别位于2018-04-13分界线上和2018-04-24分界线附近；2）异常日期间，中国大陆地磁垂直分量日变形态存在分区特征，去除经度效应后低点时间为正、负的区域内日变形态分别以“W”型和“V”型为主；3）在2018-04-13和2018-04-24这2个异常日期间，中国大陆都存在去除经度效应后的低点时间高梯度带，松原5.7级地震的震中分别位于2018-04-13高梯度区边缘和2018-04-24高梯度区东侧。  相似文献   

5.
We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas.The areas of high concentrations are primarily outside the eastern mouth of the Qiongzhou Strait and on the west side of the Leizhou Peninsula,whereas the areas of low concentrations are located primarily in the eastern Qiongzhou Strait.The maximum Cd,Pb and Zn concentrations in the samples collected in our study do not exceed the official standards for marine sediments,whereas the concentrations of Cr and Cu slightly exceed the standards.Correlations exist between the concentrations of Cu,Pb,Zn,Cr and Cd,and the concentrations of these metals are positively correlated with the mean particle size(φ value),indicating that the finer sediments have adsorbed greater amounts of heavy metal elements than the coarser sediments.An evaluation of the potential environmental risks demonstrates that certain indices of heavy metal pollution and environmental risks are relatively low and may be assigned low risk levels,thereby indicating that,in terms of heavy metals,the marine sedimentary environment in this region is only mildly impacted.Our analysis of the contaminant origins shows that the heavy metals in this region primarily originate in the Pearl River Estuary and that a small amount of them is derived from local runoff.The elevated heavy metal concentrations from the upper sections of the cores started 130 years ago,which indicats that heavy metals in the surface sediments are primarily due to human activities associated with industrialization.  相似文献   

6.
Many nature reserves are established to protect the habitat needs of particular endangered species of interest but their effec-tiveness for protecting other species is questionable.In this study,this effectiveness was evaluated in a nature reserve network located in the Qinling Mountains,Shaanxi Province,China.The network of reserves was established mainly for the conservation of the giant panda,a species considered as a surrogate for the conservation of many other endangered species in the region.The habitat suitability of nine protected species,including the giant panda,was modeled by using Maximum Entropy（MAXENT） and their spatial congruence was analyzed.Habitat suitability of these species was also overlapped with nature reserve boundaries and their management zones（i.e.,core,buffer and experimental zones）.Results show that in general the habitat of the giant panda constitutes a reasonable surrogate of the habitat of other protected species,and giant panda reserves protect a relatively high proportion of the habitat of other protected species.Therefore,giant panda habitat conservation also allows the conservation of the habitat of other protected species in the region.However,a large area of suitable habitat was excluded from the nature reserve network.In addition,four species exhibited a low proportion of highly suitable habitat inside the core zones of nature reserves.It suggests that a high proportion of suitable habitat of protected species not targeted for conservation is located in the experimental and buffer zones,thus,is being affected by human activities.To increase their conservation effectiveness,nature reserves and their management zones need to be re-examined in order to include suitable habitat of more endangered species.The procedures described in this study can be easily implemented for the conservation of many endangered species not only in China but in many other parts of the world.  相似文献   

7.
Throughout the world, the coastal zones of many countries are used increasingly for aquaculture in addition to other activities such as waste disposal. These activities can cause environmental problems and health problems where they overlap. The interaction between aquaculture and waste disposal, and their relationship with eutrophication are the subjects of this paper. Sewage discharge without adequate dispersion can lead to nutrient elevation and hence eutrophication which has clearly negative effects on aquaculture with the potential for toxic blooms. Blooms may be either toxic or anoxia-causing through the decay process or simply clog the gills of filter-feeding animals in some cases. With the development of aquaculture, especially intensive aquaculture, many environmental problems appeared, and have resulted in eutrophication in some areas. Eutrophication may destroy the health of whole ecosystem which is important for sustainable aquaculture. Sewage discharge may also cause serious public health problems. Filter-feeding shellfish growing in sewage-polluted waters accumulate micro-organims, including human pathogenic bacteria and viruses, and heavy metal ion, presenting a significant health risk. Some farmed animals may also accumulate heavy metals from sewage. Bivalves growing in areas affected by toxic algae blooms may accumulate toxins (such as PSP, DSP) which can be harmful to human beings.  相似文献   

8.
The southwest alpine gorge region is the major state base of hydropower energy development in China and hence planned many cascading hydropower stations. After the reservoir impoundment, the intense water level fluctuations under the interaction of cascade dams operating and the mountainous flooding, usually cause bank collapse, landslide and debris flow hazards. The Xiaowan reservoir(XWR), for example, as the ‘dragon head' meg reservoir located in the middle mainstream of Lancang River, have resulted in a series of geohazards during its building and operating. In this study, we investigated the number and surface area of collapses and landslides(CLs) occurred in the water level fluctuations zone(WLFZ) of XWR using remote sensing images of Gaofen-1 and Google Earth; evaluated the CLs susceptibility using information value method. The results presented that the total WLFZ area of 87.03 km2 and 804 CLs masses with a total area of 1.98 km2 were identified in the riparian zone of XWR. CLs mainly occurred at an elevation of 1190–1240 m, and the CLs density increased with an increase in altitude. The WLFZ with a slope gradient of 25°– 45° is the main CLs distribution area that accounts for more than half of the total CLs area. The susceptibility assessment revealed that high and very high susceptibility zones are generally distributed along zones with an elevation of 1210–1240 m, a slope degree of 25°–45° and a slope aspect perpendicular to the direction of Lancang River. Furthermore, these susceptible zones are close in distance to the dam site and tend to be in the riparian zones with the formation lithology of Silurian strata. These results provide a valuable contribution to prevent and control geohazards in the XWR area. Moreover, this study offers a constructive sample of geohazards assessment in the riparian zone of large reservoirs throughout the mountains of southwest China.  相似文献   

9.
The Volgian-Valanginian succession of shallow-water deposits from the Olenek section(Anabar-Lena region, Arctic Siberia) has been studied by sedimentological and palaeontological methods. High-resolution biostratigraphy of studied interval is based on the ammonites, foraminifers, marine and terrestrial palynomorphs. Foraminiferal and palynological zones have important regional implications providing well-constrained biostratigraphy of the Anabar-Lena region. Sedimentological studies together with ecological analysis of the associations of microbenthos, microphytoplankton and terrestrial palynomorphs allow the palaeoenvironmental reconstructions for the marginal area of the Anabar-Lena palaeosea and coastal land areas.  相似文献   

10.
城市污泥土地利用的环境问题是限制其大规模利用的主要因素。本文建立基于权重线性加和模型的城市污泥土地利用环境风险控制方法,提出北京市城市污泥土地利用环境风险控制方案。不同因素对城市污泥施用的环境影响依次为：土壤重金属含量（0.22）>土地利用类型（0.17）≈土壤类型（0.17）≈自然降雨（0.17）>坡度（0.13）>与自然水体距离（0.09）>与城镇居民区距离（0.05）。北京市城市污泥低风险适宜施用区域主要集中在平谷和顺义交界处、昌平-延庆中部以及房山的东部山间林地,施用面积为2033 km2。中风险施用区分布在西南部、东南部的林地和旱地的混合区域,面积为5079 km2。高风险施用区面积为380 km2,分布在石景山以及门头沟东北部、房山西南部以及平谷北部区域。禁止施用区面积达8916 km2,主要分布在城区及城区周边的郊县、延庆、怀柔、密云等部分区域。  相似文献   

11.
山东黄河下游地区局部生态地球化学评价是在多目标区域地球化学调查和区域生态地球化学评价基础上,选特色农产品产地,绿色无公害蔬菜生产基地,地方病分布区及小清河沿岸、东营油气开采污染区等局部生态地球化学环境区。按一定的方法和采样密度采集土壤、浅层地下水、土壤溶液、植物根系土、籽实、土壤生物、微生物和种子库样品,分析As,Cd等重金属元素、N,B等有益营养元素、六六六、DDT等有机物和土壤微生物类群、功能、结构多样性,研究有益营养元素、重金属元素、有毒有机污染物的分布规律、赋存状态、来源及它们在土壤、水体及生物体中的迁移、转化、累积规律与生态效应,探讨对重金属元素污染的生物修复。提出特色农产品基地布局规划建议和地方病防治、重金属污染的治理措施。  相似文献   

12.
高密市化山矿区是山东省重要的重晶石成矿区。矿区位于胶莱盆地内,矿床赋存于莱阳群杨家庄组构造破碎带中,严格受北西向构造控制,分布有5条规模较大的矿脉,主要矿石类型为方解石-重晶石型,该文对该重晶石矿的矿床成因(低温热液裂隙充填型)、成矿模式及找矿标志进行了分析研究,对该矿区的进一步勘查及类似地区的找矿工作具有一定的指导意义。  相似文献   

13.
以南京市江南8区380家国有商业银行网点,211家股份制商业银行网点为研究样本数据,综合运用缓冲区分析、Ripley’s K函数和空间热点探测方法,分析了国有商业银行和股份制商业银行网点的空间布局特征。结果表明:两类商业银行均呈现出一定的中心集聚态势,但"向心"程度、集聚的广度与强度存在差异。缓冲区分析表明,股份制商业银行由市中心向外呈现明显递减的特点,但国有商业银行在前3个缓冲圈层内分布比较均匀;Ripley’s K函数方法表明,两类商业银行均呈现先增后减的倒"U"型空间集聚特征,但股份制商业银行集聚范围小于国有商业银行;空间热点探测方法表明,两类商业银行热点区域集聚强度相异,国有商业银行低于股份制商业银行。分析空间热点重叠部位,将国有商业银行与股份制商业银行空间布局导向分为商业中心导向、高新技术-商业中心导向和人力资本-政府机构-商业中心导向。  相似文献   

14.
用GPS资料研究华北地区形变场和构造应力场   总被引：5，自引：2，他引：3  
利用华北地区地质构造、第四纪以来的活动断层、地形、地壳厚度、地壳及上地幔地震波速度结构等资料,构建了三维有限元框架模型,利用最新GPS观测结果作为边界约束条件,模拟计算了华北地区的形变场及构造应力场。结果表明,模型预测地表速度场和GPS观测结果比较一致。模拟结果中,大型NNE向断层如汾渭地堑断裂系呈右旋运动,NWW向断层如张家口渤海断裂带呈左旋运动,与野外地质考察结果一致。在地表以下10～20km处,模型预测应力场的主压应力方向为NNE、EW向,主张应力大约为主压应力2～8倍。模型中最大剪切应力场在山西、华北平原中部和东部沿海分别出现3条NNE向高梯度带,此梯度带与研究区域的主要地震活动带相对应。  相似文献   

15.
The Jianchang Basin is one of the main localities of the precious fossils of Jehol Biota in western Liaoning. The fossil-bearing horizons are mainly in the Yixian- and J iufotang formations. In the Weijialing－Yaolugou of southwest Jianchang Basin, many precious fossils have been found at Luojiagou Bed of the 2nd Member of the Yixian Formation and at Xidian Bed of the 1st member of the Jiufotang Formation. The geologic setting, sedimentary environment and paleogeography of the precious fossil-bearing beds were also studied.  相似文献   

16.
The distribution of trace metals in remote alpine region is an effective way to understand the impacts of regional human activity and vegetation on the alpine ecosystem. In this study, the concentrations of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) in the soils of Gongga Mountain, Eastern Tibetan Plateau, were investigated to reveal their seasonal and spatial distribution and enrichment state, and to decipher the effects of atmospheric deposition and vegetation on their distributions among five vegetation zones. The results showed that the concentrations of Cd, Pb, and Zn were higher in the O horizon than in other horizons despite the seasonal changes, whereas Cu was enriched in the C horizon. The enrichment states of the metals studied in the soils decreased in the order of Cd > Pb > Zn > Cu. Cd and Pb were mainly sourced from atmospheric deposition; Zn was from both atmospheric deposition and parent materials, whereas Cu was mainly from parent materials. Seasonally, the trace metals were generally higher in May and December but lower in September, implying the impact of vegetation on the distribution of trace metals under the plant uptake and the litter decomposition. Spatially, the higher enrichment of Cu, Pb, and Zn in the soils existed in the mixed broadleaf-coniferous forests and coniferous forests (approximately 3000 m above sea level). The results suggested that atmospheric deposition and biological processes are main factors controlling the seasonal and spatial distribution of trace metals in the soils of the remote alpine ecosystem.  相似文献   

17.
Surface sediments were collected from Lake Manzala, the Mediterranean coastal wetland located to the east of the Nile Delta, Egypt, to assess the effect of drain effluent on the spatial variations of sedimentary characteristics and heavy metal pollution. Grain-size compositions, textures, and heavy metal distribution patterns in sediments are presented using GIS technique. Results of the analysis of the sediment showed a clear effect of drain effluent, with an increase in fine fractions and homogeneous suspensions in transportation mode. Lake sediments were dominated by sandy mud textures, and mode of transportation was homogeneous suspension and rolling. Spatial distribution of heavy metals(Fe, Mn, Zn, Cu, Ni, Cr, and Pb) was studied in the lake's surficial sediments, along with their relationship to drain effluent and their contamination status in the ecological system. Heavy metal pollution status was assessed by means of accepted sediment quality guidelines and contamination assessment methods(contamination factor, contamination degree, modified contamination degree, geo-accumulation, and enrichment factor). Among the determined heavy metals, Pb had the most ecological risk. Generally, the heavy metals in the surface sediments indicated pollution risk ranging from moderate to considerable, particularly, in those sites facing drains and inlets that had the highest toxic effluent. The results were interpreted by statistical means. A cluster analysis defined areas facing drain discharge and inlets as separated groups. ANOVA indicated that most of the sedimentation and studied metals directed this clustering.  相似文献   

18.
The spatial connections of endogenous deposits with anomalies of the vertical density gradient in lithosphere,calculated on the formulas for the spherical gravity sources are analyzed for Amur Province. The spatial parameters of tin-bearing, tungsten-bearing and gold-bearing regional ore-magmatic systems (ore regions, belts, zones and areas) are characterized by correlation of deep gradient density anomalies in the crust and upper mantle with the extensivity of superficial ore mineralization. Tin-ore deposits are mainly connected with density heterogeneities of the upper crust layer (up to a depth of 20 km), and tungsten, molibdenium and polymetallic deposits-with anomalies of the density gradient in the low crust layer (at a depth of 30 km) and in the upper mantle (at a depth of 60～70 km). Gold-ore regions are characterized by the greatest vertical range of fluid-magmatic systems (about 100 km from the surface) and arethrough ones in relation to mantle and crust tectonic structures. Opportunity is shown for the 3D density gradient model of the Amur Province lithosphere to be applied for constructing the forecast metallogenic models.  相似文献   

19.
On the contiguous territories of Russia and China, along the left and right banks of the Amur River (Heilongjiang Province of China, and Amur Oblast′ of Russia), several Precambrian protrusions (Gonzhinsk, Mamynsk, Amurkhe, and Khumakhe) are known. On the Russian territory, along the setting and on the area of the protrusions, lode manifestations, precious-metal deposits, and gold-platinoid placers are known having the industrial imponance. Ultramafites are metasomatically altered more likely by the action of the kate Paleozoic intrusions and produced by them hydrothermae, and are transformed into listvenites. It can be concluded that as one of the sources of precious metals in the placers were the aureoles of listvenitization. This is evidenced by the presence of talc (typomorphic mineral of apoultrabasites) inclusions together with Pt-, Pd- and Ir-bearing gold in the corrosive coatings of the primary platinoids. This conclusion requires the revision of the work strategy of prospecting the lode gold and PGE manifestations within the ore-placer node because apoultrabasites before were considered non-promising for precious metals.  相似文献   

20.
On the contiguous territories of Russia and Chi-na,along the left and right banks of the Amur Riv-er (Heilongjiang Province of China,and Amur Oblast' of Russia),among the Late Mesozoic ter-rigenous and volcano-plutonic formations,several Precambrian prot…  相似文献   

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