利用敦煌辐射校正场对FY-2B静止气象卫星进行可见光通道的在轨辐射定标   总被引：12，自引：0，他引：12       下载免费PDF全文

戎志国张玉香  邱康睦胡秀清　张立军 《应用气象学报》2004,15(3):266-272

FY-2B由于杂散光的影响，其可见光通道的发射前定标存在较大误差。利用敦煌戈壁滩辐射校正场可进行FY-2B可见光通道的在轨绝对定标。由于FY-2B对于敦煌场区的卫星天顶角接近50°，需要进行场地的方向特性BRDF修正。2002年7月对FY-2B进行了场地地表反射率、大气消光、探空等项同步测量，并对场地的方向特性进行了测量。资料处理结果表明，FY-2B可见光通道杂散光可影响定标精度达20%。长期监视表明FY-2B可见光通道探测器输出十分稳定。该文将4个可见光通道探测器场地定标得出的定标查找表列出，供用户参考使用。  相似文献   

Petrologic, isotopic, and radiometric age constraints on the origin and tectonic history of the Malino Metamorphic Complex, NW Sulawesi, Indonesia     

Theo van Leeuwen  Charlotte M. Allen  Ade Kadarusman  Marlina Elburg  J. Michael Palin  Muhardjo  Suwijanto 《Journal of Asian Earth Sciences》2007,29(5-6):751-777

The Malino Metamorphic Complex (MMC) is located at the western end of the north arm of Sulawesi. It consists of mica schists and gneisses (derived from proximal turbidite and granitoid protoliths), with intercalations of greenschist, amphibolite, marble, and quartzite, forming an E-W elongated dome-like structure bounded on all sides by faults. The age of the MMC is constrained between Devonian and Early Carboniferous. This Paleozoic age, the presence of Archean and Proterozoic inherited zircons, and the isotopic signature of the mica schists and gneisses indicate that the terrane was derived from the New Guinea-Australian margin of Gondwana. Similarities with basement rocks in the Bird’s Head suggests a common origin. Greenschists forming a discontinuous selvage (metamorphic carapace) around the complex were derived from adjacent autochthonous Paleogene formations. The rocks of the MMC show a Barrovian-type progression from greenschist through epidote-amphibolite to amphibolite facies. P–T estimations suggest a depth of burial of up to 27–30 km. K/Ar and 40Ar/39Ar cooling ages of 23–11 Ma, and a 7 Ma age for unconformably overlying volcanic rocks, indicate that the complex was exhumed during the Miocene. Two tectonic scenarios are considered: 1. the continental fragment docked with Sulawesi during the Mesozoic and was exhumed as a metamorphic core complex during the Miocene; 2. it was subducted beneath the north arm during the late Oligocene and then rapidly returned back to the surface.  相似文献   

Événements panafricains dans l'Adrar Souttouf (Sahara marocain)     

Michel Villeneuve  Hervé Bellon  Abdelkrim El Archi  Mohamed Sahabi  Jean-Pierre Rehault  Jean-Louis Olivet  Abdel M. Aghzer 《Comptes Rendus Geoscience》2006,338(5):359-367

The Adrar Souttouf belt (Western Sahara) lies in the northern part of the Mauritanide belt and was considered as a part of the Hercynian Mauritanian-Appalachian belt. Recently the presence of a Panafrican protolith (595 Ma) was evidenced by the age of inherited zircons from an eclogitic unit and led to consider complex Panafrican events included in the Hercynian belt, as in the central and southern Mauritanide belt. Our new field survey completed by ten KAr dating (whole rocks and separate minerals) confirmed that multiphased Panafrican formations outcrop within the center of the Adrar Souttouf massif. Diverse events ranged from ca. 1000 to 500 Ma, some of them being indicative of an oceanic type environment and metamorphism. The 1000 Ma metamorphic event is recorded for the first time in the West African craton. A large Hercynian remobilisation is also evidenced. To cite this article: M. Villeneuve et al., C. R. Geoscience 338 (2006).  相似文献   

Evaluation of directional normalization methods for Landsat TM/ETM+ over primary Amazonian lowland forests     

《International Journal of Applied Earth Observation and Geoinformation》2017

Biodiversity mapping in extensive tropical forest areas poses a major challenge for the interpretation of Landsat images, because floristically clearly distinct forest types may show little difference in reflectance. In such cases, the effects of the bidirectional reflection distribution function (BRDF) can be sufficiently strong to cause erroneous image interpretation and classification. Since the opening of the Landsat archive in 2008, several BRDF normalization methods for Landsat have been developed. The simplest of these consist of an empirical view angle normalization, whereas more complex approaches apply the semi-empirical Ross–Li BRDF model and the MODIS MCD43-series of products to normalize directional Landsat reflectance to standard view and solar angles. Here we quantify the effect of surface anisotropy on Landsat TM/ETM+ images over old-growth Amazonian forests, and evaluate five angular normalization approaches. Even for the narrow swath of the Landsat sensors, we observed directional effects in all spectral bands. Those normalization methods that are based on removing the surface reflectance gradient as observed in each image were adequate to normalize TM/ETM+ imagery to nadir viewing, but were less suitable for multitemporal analysis when the solar vector varied strongly among images. Approaches based on the MODIS BRDF model parameters successfully reduced directional effects in the visible bands, but removed only half of the systematic errors in the infrared bands. The best results were obtained when the semi-empirical BRDF model was calibrated using pairs of Landsat observation. This method produces a single set of BRDF parameters, which can then be used to operationally normalize Landsat TM/ETM+ imagery over Amazonian forests to nadir viewing and a standard solar configuration.  相似文献   

Review paper: Exploration geophysics for intrusion‐hosted rare metals          下载免费PDF全文

M.D. Thomas  K.L. Ford  P. Keating 《Geophysical Prospecting》2016,64(5):1275-1304

Igneous intrusions, notably carbonatitic–alkalic intrusions, peralkaline intrusions, and pegmatites, represent significant sources of rare‐earth metals. Geophysical exploration for and of such intrusions has met with considerable success. Examples of the application of the gravity, magnetic, and radiometric methods in the search for rare metals are presented and described. Ground gravity surveys defining small positive gravity anomalies helped outline the shape and depth of the Nechalacho (formerly Lake) deposit within the Blatchford Lake alkaline complex, Northwest Territories, and of spodumene‐rich mineralization associated with the Tanco deposit, Manitoba, within the hosting Tanco pegmatite. Based on density considerations, the bastnaesite‐bearing main ore body within the Mountain Pass carbonatite, California, should produce a gravity high similar in amplitude to those associated with the Nechalacho and Tanco deposits. Gravity also has utility in modelling hosting carbonatite intrusions, such as the Mount Weld intrusion, Western Australia, and Elk Creek intrusion, Nebraska. The magnetic method is probably the most successful geophysical technique for locating carbonatitic–alkalic host intrusions, which are typically characterized by intense positive, circular to sub‐circular, crescentic, or annular anomalies. Intrusions found by this technique include the Mount Weld carbonatite and the Misery Lake alkali complex, Quebec. Two potential carbonatitic–alkalic intrusions are proposed in the Grenville Province of Eastern Quebec, where application of an automatic technique to locate circular magnetic anomalies identified several examples. Two in particular displayed strong similarities in magnetic pattern to anomalies accompanying known carbonatitic or alkalic intrusions hosting rare‐metal mineralization and are proposed to have a similar origin. Discovery of carbonatitic–alkalic hosts of rare metals has also been achieved by the radiometric method. The Thor Lake group of rare‐earth metal deposits, which includes the Nechalacho deposit, were found by follow‐up investigations of strong equivalent thorium and uranium peaks defined by an airborne survey. Prominent linear radiometric anomalies associated with glacial till in the Canadian Shield have provided vectors based on ice flow directions to source intrusions. The Allan Lake carbonatite in the Grenville Province of Ontario is one such intrusion found by this method. Although not discovered by its radiometric characteristics, the Strange Lake alkali intrusion on the Quebec–Labrador border is associated with prominent linear thorium and uranium anomalies extending at least 50 km down ice from the intrusion. Radiometric exploration of rare metals hosted by pegmatites is evaluated through examination of radiometric signatures of peraluminous pegmatitic granites in the area of the Tanco pegmatite.  相似文献   

Aster多光谱遥感异常提取在新疆天湖铁矿中的应用   总被引：3，自引：0，他引：3  

陈建明  孙卫东  闫柏琨  于浩 《新疆地质》2009,27(4)

ASTER遥感数据因波段范围宽、波段多,在蚀变异常提取与矿产勘探中有较好的应用前景.据金属矿床常见蚀变矿物光谱特征与ASTER数据波段设置特点,提出硅酸盐铁、Fe~(2+)、白云石等提取的光谱指数.在此基础上研究该数据大气校正、干扰剔除等数据处理技术方法,提出了异常提取技术流程与步骤,在新疆东天山天湖铁矿区进行了试验研究,将矿物提取结果与地质图对比分析,表明提取结果与数据处理技术流程较可靠.  相似文献   

油气放射性勘查中若干问题的讨论     

吴慧山  林玉飞 《铀矿地质》1992,8(1):35-42

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航空放射性测量中的一项重要工作—飞机改装     

刘宜铬 《铀矿地质》1990,6(1):41-47

为了发挥航测仪器的性能和提高测量精度,用于航空放射性测量的飞机必须进行必要的改装,改装工作除了保证航测仪器安装可靠、牢固之外,还要使飞机对仪器的磁干扰,放射性干扰和电干扰降低到允许的水平。本文对运五和运十二飞机存在的干扰情况进行了讨论,并就如何消除这些干扰提出了切合实际的改装方案。  相似文献   

Radiometric ages of the Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian, Duckmantian]: A comparison of U–Pb zircon single-crystal ages and Ar/Ar sanidine single-crystal plateau ages     

Paul C. Lyons  T.E. Krogh  Y.Y. Kwok  Donald W. Davis  William F. Outerbridge  Howard T. Evans  Jr.   《International Journal of Coal Geology》2006,67(4):259-266

The Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian Series, Duckmantian Stage]–a kaolinized, volcanic-ash deposit occurring in Kentucky, West Virginia, Tennessee, and Virginia–is the most widespread bed in the Middle Pennsylvanian of the central Appalachian basin, USA. A concordant single-crystal U–Pb zircon datum for this tonstein gives a ²⁰⁶Pb/²³⁸U age of 314.6 ± 0.9 Ma (2σ). This age is in approximate agreement with a mean sanidine plateau age of 311.5 ± 1.3 Ma (1σ, n = 11) for the Fire Clay tonstein. The difference between the two ages may be due to bias between the ⁴⁰K and ²³⁸U decay constants and other factors. The age of the Fire Clay tonstein has important implications for Duckmantian Stage (Westphalian Series) sedimentation rates, correlations with the Westphalian Series of Europe, Middle Pennsylvanian volcanic events, and the late Paleozoic time scale.  相似文献   

伽玛能谱快速找金方法及其应用   总被引：1，自引：0，他引：1  

陈礼宽  胡兴凤 《江苏地质》1996,20(3):166-171

选用携带式微机伽玛能谱仪测定岩石，土壤中钠，钍，钾及其放射性总量，能定量或半定量地估算某些含金地质体中的含量。对新疆某地进行地面，井下测定，新发现金矿脉一条，金储量６２４ｋｇ；圈定４个金矿化段，２个富集金地段；验证评价２个综合化探晕圈，快速评价２个金矿区和８个金矿点；特别对井下预测金品位准确可靠，能及时指导矿区井下采掘。  相似文献