新疆北山地区罗东镁铁质-超镁铁质层状岩体岩石成因   总被引：4，自引：0，他引：4  

凌锦兰  夏明哲  郭娜欣  汪帮耀  夏昭德  姜常义 《地球化学》2011,(6):499-515

罗东镁铁质-超镁铁质岩体位于塔里木板块东北部的新疆北山地区,岩体平面形态为眼球状,出露面积约2.1 km2.由纯橄岩、单辉橄榄岩、斜长二辉橄榄岩、橄榄二辉岩、方辉辉石岩、橄长岩、橄榄辉长岩、辉长岩、苏长辉长岩和淡色辉长岩组成,堆晶结构和堆晶韵律发育,属于层状岩体.岩浆演化过程中主要分离结晶/堆晶相是橄榄石和单斜辉石,此...  相似文献   

Geology and age of the Glikson impact structure,Western Australia     

F. A. Macdonald  M. T. D. Wingate  K. Mitchell 《Australian Journal of Earth Sciences》2013,60(4-5):641-651

The Glikson structure is an aeromagnetic and structural anomaly located in the Little Sandy Desert of Western Australia (23°59'S, 121°34′E). Shatter cones and planar microstructures in quartz grains are present in a highly deformed central region, suggesting an impact origin. Circumferential shortening folds and chaotically disposed bedding define a 19 km-diameter area of deformation. Glikson is located in the northwestern Officer Basin in otherwise nearly flat-lying sandstone, siltstone and conglomerate of the Neoproterozoic Mundadjini Formation, intruded by dolerite sills. The structure would not have been detected if not for its strong ring-shaped aeromagnetic anomaly, which has a 10 km inner diameter and a 14 km outer diameter. We interpret the circular magnetic signature as the product of truncation and folding of mafic sills into a ring syncline. The sills most likely correlate with dolerites that intrude the Boondawari Formation ～25 km to the north, for which we report a SHRIMP U?–?Pb baddeleyite and zircon age of 508?±?5 Ma, providing a precise older limit for the impact event that formed the Glikson structure.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987113000595   总被引：11，自引：0，他引：11  

Mei-Fu Zhou  Wei Terry Chen  Christina Yan Wang  Stephen A.Prevec  Patricia Pingping Liu  Geoffrey H.Howarth 《地学前缘(英文版)》2013,4(5):481-502

Magmatic oxide deposits in the～260 Ma Emeishan Large Igneous Province(ELIP),SW China and northern Vietnam,are important sources of Fe,Ti and V.Some giant magmatic Fe-Ti-V oxide deposits, such as the Panzhihua,Hongge,and Baima deposits,are well described in the literature and are hosted in layered mafic-ultramafic intrusions in the Panxi region,the central ELIP.The same type of ELIP- related deposits also occur far to the south and include the Anyi deposit,about 130 km south of Panzhihua,and the Mianhuadi deposit in the Red River fault zone.The Anyi deposit is relatively small but is similarly hosted in a layered mafic intrusion.The Mianhuadi deposit has a zircon U-Pb age of～260 Ma and is thus contemporaneous with the ELIP.This deposit was variably metamorphosed during the Indosinian orogeny and Red River faulting.Compositionally,magnetite of the Mianhuadi deposit contains smaller amounts of Ti and V than that of the other deposits,possibly attributable to the later metamorphism.The distribution of the oxide ore deposits is not related to the domal structure of the ELIP.One major feature of all the oxide deposits in the ELIP is the spatial association of oxide-bearing gabbroic intrusions,syenitic plutons and high-Ti flood basalts.Thus,we propose that magmas from a mantle plume were emplaced into a shallow magma chamber where they were evolved into a field of liquid immiscibility to form two silicate liquids,one with an extremely Fe-Ti-rich gabbroic composition and the other syenitic.An immiscible Fe-Ti-(P) oxide melt may then separate from the mafic magmas to form oxide deposits.The parental magmas from which these deposits formed were likely Fe-Ti-rich picritic in composition and were derived from enriched asthenospheric mantle at a greater depth than the magmas that produced sulfide-bearing intrusions of the ELIP.  相似文献   

太行山东麓断裂带板内构造地貌反转与机制   总被引：5，自引：0，他引：5       下载免费PDF全文

曹现志  李三忠  刘鑫  索艳慧  赵淑娟  许立青  戴黎明  王鹏程  余珊 《地学前缘》2013,20(4):88-103

华北克拉通前寒武纪基底可划分为东部地块、中部带和西部地块。中生代以来,华北克拉通发生减薄破坏,其破坏中心位于东部地块,而西部地块与中部带基本保持完整,其过渡带就是太行山东侧。太行山地区近乎平行发育着两条重要的断裂：太行山大断裂和太行山山前断裂,统称为太行山东麓断裂带。通过研究发现,太行山山前断裂是继承早前寒武纪构造带形成的断裂,控制着太行山与东部地块前寒武纪基底的差异,古新世以来发生板内构造地貌的负反转,构成渤海湾盆地的西界断裂。太行山大断裂则在燕山期时为重要的逆冲断裂,对太行山的隆起起着重要作用;中新世以来,伴随着山西地堑系的形成,太行山大断裂发生构造负反转,控制着一系列山间地堑的发育。新生代以来,该区构造演化特征整体表现为向西构造迁移的特点,是区域走滑伸展背景下的一种新的板内盆山关系。  相似文献   

综合物探方法在新疆某铜矿区中的应用探讨   总被引：1，自引：0，他引：1  

刘方  张晓帆  陈川 《新疆地质》2013,(1):113-116

介绍了综合物探方法在富蕴县某矿区寻找隐伏矿体的应用.在地质勘查基础上,利用地面高精度磁法,大功率激电中梯和激电测深等物探手段进行隐伏矿体预测,在工作区内发现与成矿有关的地球物理异常,经钻探验证效果较好,说明该综合物探评价体系在此铜矿区应用很成功,显示其快速、高效和实用等优点.  相似文献   

西藏古大湖成盐模式的提出与分析探讨          下载免费PDF全文

王跃峰  白朝军  张明云 《盐湖研究》2006,14(3):1-5

根据目前对青藏高原第四系及古环境研究的最新进展,提出了西藏地区盐湖成盐的模式———古大湖成盐模式,并列举了诸多具有说服力的证据,为研究盐湖矿产形成规律和进一步开发利用,促进西藏经济发展,将产生积极的影响。  相似文献   

长偶极大功率可控源电磁波响应特征研究   总被引：16，自引：9，他引：7       下载免费PDF全文

底青云  王妙月  王若  王光杰 《地球物理学报》2008,51(6):1917-1928

地球物理学中关于电磁波勘探研究通常采用的是地球半空间模型.然而,对于几十公里的有限长电缆源（长偶极源）,远距离电磁波场探测必须要考虑电离层的影响,它是一个全空间问题.关于包含电离层、空气层和地球介质（我们称“地-电离层”模式）的电磁波场特征的研究在国外较少,国内几乎是空白.本文采用全空间积分方程法首先对小尺度的可控源电磁波场特征进行了研究,由于此时电离层的影响可忽略,它应该和半空间成熟的CSAMT模拟结果一致,对比结果表明,二者是一致的,验证了全空间模拟方法的可靠性和有效性.随后进行了50 km长电缆电离层和空气层高度都为100 km的“地-电离层”模式大尺度电磁波场模拟,以探讨大尺度可控源电磁波场的特征.给定频率的“地-电离层”模式电磁场的衰减曲线表明长电缆远距离电磁波场由于受电离层的作用存在衰减逐渐变小的过渡场和衰减变小的波导场.为了探讨复杂介质“地-电离层”模式电磁波特征,对“地-电离层”模式的典型地盾和地台多层介质模型进行了数值模拟,得到了偶极源长度50 km、电流200A、收发距离远达1600 km和2500 km的合理的电磁场结果.最后,对一简单含油储层结构模型进行了长偶极、大功率、远距离电磁波场响应计算.储层横向不均匀复杂结构模拟的结果表明,考虑电离层和大气层的“地-电离层”模式大尺度深层复杂介质模拟时,电磁场对深部目标体仍有很好的异常响应.  相似文献   

Large-scale cold water dispersant effectiveness experiments with Alaskan crude oils and Corexit 9500 and 9527 dispersants     

Randy C. Belore  Ken Trudel  Alan Guarino 《Marine pollution bulletin》2009,58(1):118-1031

There continues to be reluctance in some jurisdictions to use chemical dispersants as a viable countermeasure for accidental oil spills. One argument used by some opponents to dispersant use is that “chemical dispersants do not work effectively in cold water”. To address this issue, the U.S. Minerals Management Service (MMS) funded and conducted two series of large-scale dispersant experiments in very cold water at Ohmsett - The National Oil Spill Response Test Facility, located in Leonardo, New Jersey in February-March 2006 and January-March 2007. Alaska North Slope, Endicott, Northstar and Pt. McIntyre crude oils and Corexit 9500 and Corexit 9527 dispersants were used in the two test series. The crude oils were tested both when fresh and after weathering. Results demonstrated that both Corexit 9500 and Corexit 9527 dispersants were 85-99% effective in dispersing the fresh and weathered crude oils tested at cold temperatures. The MMS expects that results from these test series will assist government regulators and responders in making science based decisions on the use of dispersants as a response tool for oil spills in the Arctic.  相似文献   

Long-term plankton studies at the lower Rhine/Germany     

Günther Friedrich  Marlies Pohlmann 《Limnologica》2009,39(1):14-39

The river Rhine has lain under considerable anthropogenic stress of its water quality for 100 years. As early as 1905 the first results of studies of the plankton in the Rhine were published. Due to the long residence time of the water a real potamoplankton can develop and at the end of the Lower Rhine it reaches its highest density. The paper consists of two parts. At first an overview is given about the history of plankton studies in the Rhine. The second part is the presentation of results from a monitoring at the Lower Rhine from 1979 to 2004.First systematic studies started at the beginning of the 20th century at the beginning of pollution. Our studies started during a phase of recreation from extreme pollution and eutrophication. Samples were taken at four stations: Bad Honnef, km 640, entrance to North Rhine-Westphalia, Düsseldorf, km 732, Duisburg, km 792 downstream large industrial effluents and big cities, Kleve-Bimmen, km 865 at the border to the Netherlands.In the 1970s nutrients were high, especially phosphate 0.65 mg PO₄-P L⁻¹ in 1979. After 1980 phosphate dropped to 0.11 mg PO₄-P L⁻¹ in 2004 (mean values of the growing season). Ammonia was reduced from about 0.52 (1979) to 0.02 (2004) mg NH₄-N L⁻¹. Nitrate remained between 3.72 (1989) and 2.26 (2004) mg NO₃-N L⁻¹ at a relatively high level. Oxygen concentrations were very low during the 1960s and 1970s, sometimes only 4 mg L⁻¹ O₂. During our studies the oxygen increased up to 9 mg L⁻¹ O₂ with a tendency to 11 mg L⁻¹ O₂ in the last years. Chlorophyll a was estimated to be between 59 (1979) and 31μg L⁻¹ (1986) with short peaks up to 170 μg L⁻¹ (1989). Since 1992 the mean values have varied between 30 (1993) and 21 μg L⁻¹ (2004).The floristic phytoplankton composition is characterised by the dominance of the centric diatom Stephanodiscus hantzschii. Other diatoms like Skeletonema subsalsum, Skeletonema potamos and Asterionella formosa were regularly present in smaller quantities. The second dominant group was coccale green algae. During the 1980s they formed up to 35% of the biomass. Since the 1990s their contribution to the phytoplankton became much smaller. This change corresponds with the increase of wastewater treatment and the diminution of nutrients. All the other groups of algae were present in minor quantities. During the time of higher trophy in the 1970s and 1980s the phytoplankton formed two peaks, in recent years only one peak has developed, depending on different flow conditions during the growing season and lower trophic state in the upstream parts of the river.Excellent correspondence exists between cell number, biovolume and chlorophyll a content and the results of delayed fluorescence (DF) measurement. The trophic status in the Lower Rhine may be estimated as (moderate) eutrophic. The ecological status of the phytoplankton is good based on the requirements of the European Water Framework Directive (WFD).The zooplankton consists mainly of rotatoria and larvs of Dreissena polymorpha. Grazing on phytoplankton seems to be mainly due to the large quantities of benthic Dreissena and the newly introduced mussel Corbicula.  相似文献   

长偶极大功率可控源激励下目标体电性参数的频率响应   总被引：13，自引：6，他引：7       下载免费PDF全文

底青云  王光杰  王妙月  王若 《地球物理学报》2009,52(1):275-280

利用三维（3D）全空间积分方程准线性解作为数值模拟手段,对包含电离层、大气层和地球介质层的“地-电离层”典型异常目标体多层介质模型进行了数值模拟,得到了偶极源长度100 km、电流200 A、收发距离远达1600 km的合理的异常电性目标体的电阻率-频率响应结果.通过对不同埋深异常目标体的电阻率-频率特征的讨论,认为当考虑电离层和大气层的“地-电离层”大尺度深层横向不均匀复杂介质模拟时,电磁场对深部目标体仍有很好的异常响应,但当异常体电阻率及同一电阻率的岩石埋深不同时,其电阻率-频率的响应特征有很大不同,这正反映了不同岩石物性参数的电阻率-频率响应特征.文中结果表明从长偶极大功率源（WEM）激励的电磁场观测资料区分岩石的电阻率参数是可能的,这为利用WEM观测资料建立电性参数和岩石/地层参数经验关系奠定了基础.  相似文献