根据磁异常建立磁化强度矢量及其初步应用

本文介绍一种简便的求磁化强度矢量的方法,即由野外观测到的地磁场,经过化极(一般是化为垂直磁化),根据磁异常强度的极值及异常特征,用查表的方法求得磁化强度的倾角和方向,剩磁和感磁数值,这样就可以用于评价磁性地质体的性质与产状。本方法主要用于大面积开展磁法普查以及区域性航空磁测,在作面积性的初步解释推断时,可以免除广泛对各类磁异常进行实地特性采样和测定,能使在较短时间内对面上分布各类磁异常取得磁化强度参数,进而开展对全区磁异常的推断和评价,以加速对异常研究的进程。     

利用磁异常频谱确定磁化强度方向的方法

在磁异常处理及解释推断时,常常需要确定磁化强度方向。因为只有磁化强度方向已知时,才能正确地将磁异常化到垂直磁化,简化磁异常的解释;才能可靠地进行正演计算,为求得剩余异常创造条件;为选择法解释时所需磁化强度方向提供初始值。     

基于总梯度模分析的磁源体边界信息提取及找矿意义

低纬度地区磁异常的化极处理极不稳定,甚至出现奇异现象。因此,低纬度地区磁异常的化极处理一直是位场研究的难点。磁异常总梯度模的曲线形态与磁化强度的大小及方向无关,且其极大值位置与磁源边界具有一定的对应性,模型试验表明了该方法在低纬度地区磁异常分析与解释方面的有效性。本文将基于总梯度模的磁异常分析方法应用于老挝爬立山铁矿区的磁测资料处理,由此排除了由化极不稳定导致的虚假磁异常,圈定了矿致异常的分布范围,进一步指导矿区铁矿勘探。已完成的钻孔资料证明,由该方法确定的磁异常区域与区内磁铁矿体分布位置的吻合性较好。由此表明,该方法对低纬度区磁异常分析与解释具有重要的意义。     

利用磁位求磁化倾角的方法

在磁异常的解释工作中,常常需要对异常做化磁极计算,而化磁极是在假设异常体的磁化方向为地磁场方向的条件下进行的。但在实际情况中,由于磁性体常常存在剩余磁化强度及退磁作用,而使总磁化强度的方向与正常地磁场的方向有很大的偏离,这时就需要首先确定物体的磁化强度的方向。     

地面磁测在巴西低纬度区铁矿勘查中的应用效果

通过对巴西某铁矿磁异常的处理分析,总结了层控型磁铁石英岩铁矿的磁异常特征,并利用化极与三维反演相结合的数据处理与分析手段,对磁异常携带的磁性体信息进行了更深的剖析和提取,通过化极结果圈定了磁性分布范围,利用三维反演结果确定了磁性体在地下的展布形态,钻孔验证结果充分说明物探推断的准确性.工作区位于低磁纬度区,这里提出的数据处理方法为低磁纬度区磁异常的认识提供了成功实例.     

油气勘探中磁异常ΔT解释问题

指出了对磁异常ΔＴ做化极处理不仅方便了解释,而且可以提高磁异常解释的准确程度。在进行理论分析的基础上,以实例说明在解释磁异常ΔＴ化级结果时,应当紧密结合地质资料注意分析实测磁异常的完整情况。     

磁异常化极效果的研究

在磁法数据的三维反演中,异常解释的磁异常化极法在实际运用中得到了广泛的应用。但是,化极后是否可以提高磁异常的准确性还有待研究。运用对化极后的磁异常数据进行三维反演的方法,对局部磁异常进行磁法反演;反演的结果与未进行化极的磁异常数据的三维反演结果进行对比,表明化极后的反演结果更接近异常体模型;同时运用三维可视化技术,建立3D地球物理模型。     

地磁异常数据处理技术在低纬度地区的应用研究——以柬埔寨王国Mesam金矿为例北大核心CSCD

柬埔寨王国位于低纬度地区,地质勘查程度较低,地面高精度磁测技术能够快速获取磁异常信息,进行找矿评价。在低纬度地区磁化方向主要以水平磁化为主,磁性体产生的磁异常以负磁异常为主。本文通过对柬埔寨王国Mesam金矿磁测数据进行倒相180°、化赤和低纬度化极处理对比,认为三种处理方法得到的结果都能够完整地反映磁场分布特点,在不能忽略剩磁影响的低纬度地区对实测数据进行低纬度化极后再进行解释更加贴近真实且细节更加丰富。通过对低纬度化极后的磁异常进行水平总梯度模和小波多尺度分解计算等位场异常处理,认为磁异常水平总梯度模计算能够较好地反映深部地质体的边界范围,小波多尺度分解计算能够提取特定深度地质体的空间信息,在该区选取的磁异常处理技术是有效的,为进一步扩大该金矿区远景储量提供了新的思路。     

分析异常体磁化方向的一个实例

在处理磁测资料时,我们一般都把化磁极当作转换成垂直磁化,在异常体的磁化方向与地磁场方向一致时,这样做是合理的。但是有时会遇到不能用地磁场方向转换成垂直磁化的情况,即异常体的磁化方向并不与地磁场吻合,我们在处理山东     

航磁资料在卫宁北山寻找多金属矿中的应用

为深入研究卫宁北山地区的航磁资料,提取弱磁异常信息,对该区前期的航磁资料进行延拓、化极等处理,对磁异常做出了新的解释,分析了该地区多金属矿床(点)、矿化带与磁异常的关系,结合重力异常资料、电磁测深结果,做出磁性基底受控于近东西向构造,隐伏中酸性岩体是引起弱磁异常的磁源体,也可能就是多金属矿的物源体的推断,并预测了深部成矿远景区。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861