Three-component borehole magnetics in the COSC-2 drill hole

COSC-2 钻孔中的三组件钻孔磁铁

• 批准号: 439183143
• 负责人: Dr. Christopher Virgil
• 金额: --
• 依托单位: Institut für Geophysik und Extraterrestrische Physik
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/439183143?language=en
• 关键词: Three; component; borehole; magnetics; COSC

About 400 million years ago, in the Silurian and lower Devonian geological time periods, a collision of two continents took place in the region of what is now Scandinavia. The paleo-continent Laurentia was underthrusted by Baltica, and the Caldonian montains were formed. The mountain-building processes are of great interest for geosciences due to several similarities to the processes currently taking place in the Himalayan region. In order to study the mountain building processes, two boreholes, each approx. 2,5 km deep, were planned to be drilled within the COSC (Collisional Orogeny in the Scandinavian Caledonides) project into the suture zone between the former continents. COSC-1 was drilled in 2014, COSC-2 is scheduled for summer 2020. COSC-2 will be drilled through several units of the lower allochthon down to the autochthonous Fennoscandian basement. One of the main objectives of the COSC-2 project is to define the character and age of deformation of the greenschist facies thrust-sheets, the main Caledonian décollement and the Precambrian basement. In the proposed study, we will carry out three-component magnetometer measurements in the COSC-2 borehole. The data will be processed and reoriented to a geographical reference frame. The resulting magnetic field anomalies will be interpreted in combination with aeromagnetic and seismic data (both surface and wire-line data) in terms of a large-scale 3-D model. Through three-dimensional modelling, we will significantly reduce the non-uniqueness in present models. The results are incorporated into the existing models and thus increase accuracy of the regional structural model.The main focus of interpretation will be on the contact zone between the Caledonide décollement, hosted by Alum shale, and the Fennoscandian basement. Using the vector information of the natural remanent magnetization derived from the three-component borehole magnetic data we will be able the test several hypotheses about the geological setting in the vicinity (~ 200 m) of the drill hole. In regions of significant remanent magnetization, for example within the Rätan granite forming the Fennoscandian basement, the natural remanent magnetization will be used to derive important constraints for the reconstruction of deformation processes and the tectonic history of the Scandinavian Caledonides. Therefore, we will contribute to an improved understanding of mountain building processes, one of the major goals of the COSC project.

大约4亿年前，在志留纪和下泥盆纪地质时期，两个大陆的碰撞发生在现在的斯堪的纳维亚地区。古陆劳伦蒂亚受到波罗的海的俯冲，形成了加尔多尼亚山脉。造山过程与喜马拉雅地区目前正在进行的造山过程有几个相似之处，因此引起了地球科学的极大兴趣。为了研究造山过程，我们设计了两个钻孔，每个钻孔大约两个。2，5公里深，计划在COSC(斯堪的纳维亚喀里多尼迪斯碰撞造山带)项目内钻探到前两大洲之间的缝合带。COSC-1于2014年进行了钻探，COSC-2计划于2020年夏季进行。COSC-2将通过下层异地陶层的几个单元向下钻至原地的芬诺斯坎迪亚地下室。COSC-2项目的主要目标之一是确定绿片岩相逆冲断块、主要加里东裂陷和前寒武纪基底的变形特征和年龄。在拟议的研究中，我们将在COSC-2井中进行三分量磁强计测量。将对数据进行处理，并将其重新定位到地理参考框架。由此产生的磁场异常将结合航磁和地震数据(地面和电线数据)以大规模三维模型进行解释。通过三维建模，我们将大大减少现有模型中的不唯一性。结果被纳入现有的模型中，从而提高了区域构造模型的精度。主要的解释重点将是以明铝页岩为容矿的Caledonide沉积与Fennoscandian基底之间的接触带。利用由三分量钻孔磁数据得到的天然剩磁矢量信息，我们将能够检验有关钻孔附近(~200m)地质背景的几个假设。在剩余磁化显著的地区，例如在形成芬诺斯坎迪亚基底的Rätan花岗岩中，自然剩余磁化将被用来得出重要的约束条件，以重建斯堪的纳维亚加里多尼德的变形过程和构造历史。因此，我们将促进对造山过程的更好理解，这是COSC项目的主要目标之一。