Subsurface structure of the volcanic centre of the České Středohoří Mountains, North Bohemia, determined by geophysical surveys
Subsurface structure of the volcanic centre of the České Středohoří Mountains, North Bohemia, determined by geophysical surveys
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通过地球物理调查确定的北波希米亚捷克斯特雷多霍日山脉火山中心的地下结构
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
V. Cajz
中科院分区：
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作者：
J. Mrlina;V. Cajz
在北波西米亚的České stv edohoří mts火山中心区域（Ohře裂谷带）进行的地球物理调查表明，沉积环境中可以有效识别异常火山体和特征。为此，我们在具有本质特征的主侵入区开展了新的地球物理测量。目标是入侵的确切位置和几何形状，以及它与火山中心其他组成部分的关系。我们使用了重力、磁力、浅层地震和电磁技术。新的重力和磁场数据与旧的数据库联系在一起，这样我们就可以把这个地区作为一个整体来调查。在预期侵入范围的区域进行了电磁测量，在侵入中心区域进行了地震测量。在所有资料的基础上，以重力模拟为主，圈定了岩体的地表和地下范围，并确定了岩体的隐伏起伏。研究发现，该侵入体是由一个具有几个突出体的单一岩体形成的，而不是由地表露头所表明的一组单独的侵入体形成的。然而，侵入体受到一条主要断层的影响，导致两侧（长辉长岩/二辉长岩）的岩性差异。我们详细地展示了碎屑覆盖的深度和风化带的厚度在砾岩体的中心部分。在该地区主要构造方向上，得到了侵入区内的构造要素指示。研究结果将用于建立整个火山中心的三维地质模型。这项调查可以作为应用于沉积岩包围的火山中心研究的非地震地球物理勘探的一个例子。
Former geophysical surveys performed in the region of the volcanic centre of the České Stř edohoří Mts. in North Bohemia (the Ohře Rift zone) showed that anomalous volcanic bodies and features can be effectively identified within sedimentary environment. For this reason we carried out new geophysical measurements in the area of the main mafic intrusion of essexitic character. The target was the exact location and geometry of the intrusion and its relation to other components of the volcanic centre.We used gravity, magnetic, shallow seismic and electromagnetic techniques. The new gravity and magnetic data were tied to the old databases so that we could investigate the area as a whole complex. Electromagnetic measurements were applied in the area of the expected extent of the intrusion, and the seismic measurements in the central part of the intrusion.Based on all the data, mainly on gravity modelling, we delineated not only the surface and subsurface extent of the intrusion, but we also defined the hidden relief of the intrusion. It was found that the intrusion is formed by a single body that has a few protrusions, and not by a set of separate individual intrusions, as indicated by surface outcrops. However, the body of the intrusion is affected by a major fault that caused lithological differences on both sides (essexite/monzodiorite). In detail we show the depth of the debris cover and the thickness of the weathered zone in the central part of the essexite body. We also derived indications of tectonic elements in the area of the intrusion in the main structural/tectonic direction in the region. The results will be utilized to establish a 3D geological model of the whole volcanic centre.This investigation may serve as an example of non-seismic geophysical exploration applied to the study of volcanic centres surrounded by sedimentary rocks.