哈萨克斯坦北东天山浅成低温热液型金矿床成矿时代及构造背景   总被引：1，自引：0，他引：1  

武广  陈毓川  陈衍景 《岩石学报》2010,26(12):3683-3695

哈萨克斯坦北东天山地区是中亚造山带重要的浅成低温热液型金矿床产出地区,但其成矿年代学研究非常薄弱。为确定成矿时代,作者运用高精度激光40Ar/39Ar定年法对阿尔哈尔雷金矿床和乌仁科布拉克金矿床的赋矿围岩进行了年龄测定。获得阿尔哈尔雷金矿床安山岩样品20个点40Ar/39Ar等时线年龄为304±7Ma(MSWD=6),乌仁科布拉克金矿床安山玄武岩样品21个点40Ar/39Ar等时线年龄为280±6Ma(MSWD=2.4),表明哈萨克斯坦北东天山地区浅成低温热液型金矿床主要形成于晚石炭世末期-早二叠世。初步的岩石学、地球化学研究表明,哈萨克斯坦北东天山地区晚石炭世末期-二叠纪火山岩主要为流纹岩、粗安岩、玄武粗安岩、玄武安山岩、粗面玄武岩和玄武岩,具双峰式特征,主体属于高钾钙碱性和橄榄玄粗岩系列。哈萨克斯坦北东天山地区晚石炭世末期浅成低温热液型金矿床形成于碰撞晚期向裂谷的转换阶段,而二叠纪浅成低温热液型金矿床产出于陆内裂谷环境。  相似文献   

Discrimination of lithogenic and anthropogenic sources of metals and sulphur in soils of the central-northern part of the Zambian Copperbelt Mining District: A topsoil vs. subsurface soil concept     

Bohdan Kříbek  Vladimír Majer  František Veselovský  Imasiku Nyambe 《Journal of Geochemical Exploration》2010

Samples of topsoil together with reference samples of subsurface soil from a depth of 80–90 cm were collected in the central-northern part of the Zambian Copperbelt to distinguish lithogenic sources of metals from anthropogenic contamination of soils caused by fallout of dust from mining operations, flotation ore treatment plants, tailings dams, smelters and slag dumping grounds. The total sulphur, Cu and Co contents were found to be significantly higher in topsoil relative to subsurface soil over a large part of the surveyed area, and Zn, Pb, As and Hg contents showed a definite increase in the close neighbourhood of smelters and in the direction of prevailing winds. This indicates that the increase of these elements in the topsoil is due to anthropogenic activities. The areal extent and degree of anthropogenic contamination of topsoil can be expressed by an enrichment index (EI) based on the average ratio of the actual and median concentrations of the given contaminants. Although the contamination of soil by dust fallout decreases progressively with depth in the soil profile, in areas strongly affected by mining and mineral processing the anthropogenic contamination by sulphur and copper can be traced to a depth of 80–90 cm. In contrast, the concentration of elements such as Cr, Ni, and V, that show a direct correlation with the content of iron in the soils, increases in the subsurface soil relative to the topsoil. This is particularly evident in areas underlain by rocks of the Katanga Supergroup.  相似文献   

佳木斯地块片麻状花岗岩的锆石离子探针U—Pb年龄   总被引：25，自引：19，他引：25  

吴福元  S  WSILDE 《岩石学报》2001,17(3):443-452

我国东北地区佳木斯地块分布有大量的花岗质岩石，这些花岗岩可分为两个大的类型，其一为基底花岗片麻岩类，岩石曾经历过50Ma左右的角闪岩相－麻粒岩相变质作用的改造，并具有与麻山群变质岩系相同或一致的片麻理构造。其二为片麻状花岗岩类，片麻理发育程度不等，岩石显示明显的岩浆结晶结构，不具有任何后期变质作用叠加的痕迹，传统认为片麻状花岗岩形成于新元古代，但本文通过高精度的锆石离子探针U－Pb测年表明，这些花岗岩主要形成于270－254Ma的晚古生代，且部分岩石中含有较老的锆石颗粒或残留，表明这些花岗岩主要来源于基底岩石的部分熔融，测定岩石的矿物组成和化学成分特点暗示，它的形成可能与佳木斯地块与周围块体或佳木斯地块内部块体间的拼合作用有关。  相似文献   

中国多金属结核开辟区的深海环境   总被引：7，自引：0，他引：7  

倪建宇  周怀阳  彭晓彤  梁楚进 《海洋地质与第四纪地质》2002,22(1):43-47

阐述了中国多金属结核开辟区深海环境的水文、生物和化学特征。开辟区海域水柱由表层混合层、温跃层、海底温跃层和海底边界层等不同水层构成，整个海域水动力条件总体上较为缓慢，但也存在着周期性的水流速度大于15cm/s的海底风暴；区内海底生态系统的显著特点是极低的生产力和生物过程速率，但生物多样性极高；整个区域内表层沉积物分布较均一，以低有机含量的硅质粘土、深海软泥为主，其化学组成上受沉积环境和早期成岩作用的影响和控制。  相似文献   

Why do they burn the 'bush'? Fire, rural livelihoods, and conservation in Zambia     

CHRISTINE ERIKSEN 《The Geographical journal》2007,173(3):242-256

Despite the historical importance of fire as a savanna land management tool, much controversy still surrounds discussions on anthropogenic fire utilization and the sustainability of indigenous land management practices in African savannas. This controversy is arguably a result of a discord between official fire policies and actual indigenous fire practices – a discord based on a gap in existing knowledge of, and a lack of informed literature on, the importance of fire for socio-economic and environmental survival in savanna environments. Addressing a continuing lack of research on the political ecology of fire, this study investigates the historical and present day socio-economic, environmental and political frameworks that affect anthropogenic burning regimes and land management in the Kafinda Game Management Area and Kasanka National Park in Zambia. A series of participatory research activities revealed the continuing importance of fire to rural livelihoods, but that a mismatch in desired burning regimes exists between local stakeholders. The paper argues that local power relations are preventing the local communities from adopting burning regimes that would be more environmentally sustainable and more in line with present day farming systems.  相似文献   

长岭山北麓断裂晚第四纪活动性及构造稳定性研究     

柳煜  王爱国  李明永  刘洪春  张有龙 《中国地震》2006,22(4):394-404

通过野外调查表明,长岭山北麓断裂晚第四纪以来表现出强烈的新活动性.沿断裂年青冲沟以及最新阶地发生水平左旋位移,通过测量及位移量的分组分析并结合相关年代计算得到,该活动断裂晚更新世以来水平滑动速率为5.1mm/a,垂直滑动速率为0.19mm/a;全新世以来水平滑动速率3.53±0.34 mm/a,垂直滑动速率0.29±0.03 mm/a.沿断裂全线进行分析并结合断层剖面得到,小红山一带断层上覆0.4～1.2 m的坡洪积层(底部TL年龄6.1±0.7 kaBP)未被错动,而且Ⅰ级河流阶地及河漫滩相沉积物均未发生变形变位.1927年古浪8.0级地震形成的地表破裂向东抵达下井子沟地区,但未通过陶家山北的明代长城.区域分析表明,长岭山北麓断层构成古浪活动断裂带的东延段,和前人已经确定的天桥沟断层、黄羊川断层一起构成古浪左旋走滑兼逆冲活动断裂带.1927年古浪8.0级地震形成大破裂--贯通型的地震地表破裂带,说明该断裂所在地区为破裂的成熟地段.通过计算,并考虑到古浪大地震的离逝时间以及结合区域资料分析表明,该活动断裂所在地区至少500a内是相对稳定的,1000a的预测时段内发生强、大地震的概率也很低,但是不排除发生中强地震的可能.  相似文献   

OCEAN BOTTOM SEISMOMETER AND ONSHOREOFFSHORE SEISMIC EXPERIMENT IN NORTHEASTERN SOUTH CHINA SEA   总被引：7，自引：0，他引：7  

QIU Xuelin~ 《大地构造与成矿学(英文版)》2004,28(1):28-35

Three-component Ocean Bottom Seismometers, portable land stations and marine air gun seismic sources were used to carry out an onshore-offshore deep seismic profile in northeastern South China Sea. This profile, orientated in NNW-SSE, was as long as 500 km and perpendicular to the strike of regional tectonics. The offshore data were processed in Taiwan Ocean University using a number of available software and the onshore data were analyzed in South China Sea Institute of Oceanology by new-written programs and public software. Preliminary results show that the seismic data are in good quality and contain rich information of deep structure. Seismic phases, e.g. Pg, PmP and Pn, are identified in the offset range 5～220 km, which will provide an important dataset for the deep crustal structure and oil-gas basin evolution studies of this region.  相似文献   

Asymmetrical valleys created by the geomorphic response of rivers to strike-slip fault     

Ke Zhang  Kaiyu Liu  Jinchun Yang 《Quaternary Research》2004,62(3):310-315

Offset fluvial valleys, including rivers beheaded and deflected by strike-slip faults, have long been used to estimate horizontal displacements on the faults. Larger rivers crossing such faults, however, sometimes show either no offset or only a small amount of offset compared to smaller rivers crossing the same faults. The larger rivers with higher erosional rates may widen their valleys asymmetrically downstream of strike-slip faults, rather than being beheaded or deflected. Examples are described from the Yellow River near the NE margin of the Tibetan Plateau. River beheading and asymmetrical widening are two end-members of a fluvial valley's response to strike-slip faulting, whereas deflection is a combination of both. Recognition of the formation of such asymmetrical valleys related to strike-slip faulting will help to understand fault activity better over longer time spans and enable a re-evaluation of many fault histories worldwide.  相似文献   

Deglacial to middle Holocene (16,600 to 6000 calendar years BP) climate change in the northeastern United States inferred from multi-proxy stable isotope data, Seneca Lake, New York     

Katharine Guiles Ellis  Henry T. Mullins  William P. Patterson 《Journal of Paleolimnology》2004,31(3):343-361

Climate change in the northeastern United States has been inferred for the last deglaciation to middle Holocene (∼16,600 to 6000 calendar years ago) using multi-proxy data (total organic matter, total carbonate content, δ¹⁸ O calcite and δ¹³ C calcite) from a 5 m long sediment core from Seneca Lake, New York. Much of the regional postglacial warming occurred during the well-known Bolling and Allerod warm periods (∼14.5 to 13.0 ka), but climate amelioration in the northeastern United States preceded that in Greenland by ∼2000 years. An Oldest Dryas climate event (∼15.1 to 14.7 ka) is recognized in Seneca Lake as is a brief Older Dryas (∼14.1 ka) cold event. This latter cold event correlates with the regional expansion of glacial Lake Iroquois and global meltwater pulse IA. An increase in winter precipitation and a shorter growing season likely characterized the northeastern United States at this time. The Intra-Allerod Cold Period (∼13.2 ka) is also evident supporting an “Amphi-Atlantic Oscillation” at this time. The well-known Younger Dryas cold interval occurred in the northeastern United States between 12.9 and 11.6 ka, consistent with ice core data from Greenland. In the Seneca Lake record, however, the Younger Dryas appears as an asymmetric event characterized by an abrupt, high-amplitude beginning followed by a more gradual recovery. Compared to European records, the Younger Dryas in the northeastern United States was a relatively low-amplitude event. The largest amplitude and longest duration anomaly in the Seneca Lake record occurs after the Younger Dryas, between ∼11.6 and 10.3 ka. This “post-Younger Dryas climate interval” represents the last deglacial climate event prior to the start of the Holocene in the northeastern United States, but has not been recognized in Greenland or Europe. The early to middle Holocene in the northeastern United States was characterized by low-amplitude climate variability. A general warming trend during the Holocene Hypsithermal peaked at ∼9 ka coincident with maximum summer insolation controlled by orbital parameters. Millennial- to century-scale variability is also evident in the Holocene Seneca Lake record, including the well-known 8.2 ka cold event (as well as events at ∼7.1 and 6.6 ka). Hemispherical cooling during the Holocene Neoglacial in the northeastern United States began ∼5.5 ka in response to decreasing summer insolation.  相似文献   

湘东北大万金矿区构造成矿背景探讨   总被引：4，自引：2，他引：4  

肖拥军  陈广浩  符巩固 《大地构造与成矿学》2002,26(2):143-147

自中元古代以来,湘东北地区经过多期次的构造活动,形成以EW向构造为基础,NNE向构造为主的构造特征,韧性剪切推覆带和长平断裂控矿作用明显,冷家溪群是金的预富层位,大万金矿区NWW向断裂构造是主要的容矿构造,主要成矿作用发生于燕山晚期,燕山期花岗岩体及其有关热液对金矿床形成有着积极的作用。  相似文献