Chile is a very important country that forms part of the Andean metallogenic belts. The Atacama and Domeyko fault systems in northern Chile control the tectonic- magmatic activities that migrate eastward and the types...Chile is a very important country that forms part of the Andean metallogenic belts. The Atacama and Domeyko fault systems in northern Chile control the tectonic- magmatic activities that migrate eastward and the types of mineral resources. In this paper, we processed and interpreted aeromagnetic data from northern Chile using reduction to pole, upward field continuation, the second derivative calculation in the vertical direction, inclination angle calculation, and analytical signal amplitude analysis. We revealed the locations and planar distribution characteristics of the regional deep faults along the NNE and NS directions. Furthermore, we observed that the major reasons for the formation of the tectonic-magmatic rocks belts were the nearly parallel deep faults distributed from west to east and multiple magmatic activities along these faults. We ascertained the locations of volcanic mechanisms and the relationships between them using these regional deep faults. We deduced the spatial distributions of the basic-intermediate, basic, and acidic igneous rocks, intrusive rocks, and sedimentary sequences. We showed the linear positive magnetic anomalies and magnetic anomaly gradient zones by slowly varying the background, negative magnetic anomaly field, which indicated the presence of strong magmatic activities in these regional deep faults; it also revealed the favorable areas of copper and polymetallic mineralization. This study provides some basic information for further research on the geology, structural characteristics, and mineral resource prospecting in northern Chile.展开更多
Deep drilling data on seismogenic faults that are obtained directly can help in understanding earthquake mechanisms and the resulting changes in deep structure and material composition.However,geophysical data are nec...Deep drilling data on seismogenic faults that are obtained directly can help in understanding earthquake mechanisms and the resulting changes in deep structure and material composition.However,geophysical data are necessary to ensure that the planned borehole accurately drills through the target faults.In this study,the deep crustal structure of the Longmenshan fault is explored to obtain seismogenic fault characteristics of the Wenchuan earthquake.A scientific drilling project,Wenchuan Earthquake Fault Scientific Drilling No.4 Borehole(WFSD-4)is proposed with a borehole designed to drill through the north section of the fault zone while penetrating as many geological bodies and target layers related to seismogenic fault slip as possible.High-precision seismic exploration is then carried out to study the deep structure of the fault zone and achieve the scientific objective of the borehole.Two high-precision deep seismic reflection lines were arranged perpendicularly to the fault zone,and data were obtained through special acquisition schemes and processing methods.Finally,the surface position and drilling depth route of WFSD-4 are determined based on the interpretation results of seismic profiles.The seismic reflection method for site selection of the Wenchuan earthquake fault scientific drilling is proven feasible by comparing the interpretation with the actual drilling results,laying the foundation for further study on the deep structures of fault zones.展开更多
基金supported by the National Science Foundation of China(No.41404070)China Geological Survey(No.DD20160102-02)
文摘Chile is a very important country that forms part of the Andean metallogenic belts. The Atacama and Domeyko fault systems in northern Chile control the tectonic- magmatic activities that migrate eastward and the types of mineral resources. In this paper, we processed and interpreted aeromagnetic data from northern Chile using reduction to pole, upward field continuation, the second derivative calculation in the vertical direction, inclination angle calculation, and analytical signal amplitude analysis. We revealed the locations and planar distribution characteristics of the regional deep faults along the NNE and NS directions. Furthermore, we observed that the major reasons for the formation of the tectonic-magmatic rocks belts were the nearly parallel deep faults distributed from west to east and multiple magmatic activities along these faults. We ascertained the locations of volcanic mechanisms and the relationships between them using these regional deep faults. We deduced the spatial distributions of the basic-intermediate, basic, and acidic igneous rocks, intrusive rocks, and sedimentary sequences. We showed the linear positive magnetic anomalies and magnetic anomaly gradient zones by slowly varying the background, negative magnetic anomaly field, which indicated the presence of strong magmatic activities in these regional deep faults; it also revealed the favorable areas of copper and polymetallic mineralization. This study provides some basic information for further research on the geology, structural characteristics, and mineral resource prospecting in northern Chile.
基金supported by the“Deep Structure and Variation Characteristics of Fracture Shear Band of the Longmenshan Fault Zone”of the National Natural Science Foundation of China (No.42174123)the“Wenchuan Earthquake Fault Scientific Drilling”of the National Science and Technology Planning Project and the“3D Geological Mapping of Longmenshan Fault Zone”Project of the CGS China Geological Survey (No.1212011220265).
文摘Deep drilling data on seismogenic faults that are obtained directly can help in understanding earthquake mechanisms and the resulting changes in deep structure and material composition.However,geophysical data are necessary to ensure that the planned borehole accurately drills through the target faults.In this study,the deep crustal structure of the Longmenshan fault is explored to obtain seismogenic fault characteristics of the Wenchuan earthquake.A scientific drilling project,Wenchuan Earthquake Fault Scientific Drilling No.4 Borehole(WFSD-4)is proposed with a borehole designed to drill through the north section of the fault zone while penetrating as many geological bodies and target layers related to seismogenic fault slip as possible.High-precision seismic exploration is then carried out to study the deep structure of the fault zone and achieve the scientific objective of the borehole.Two high-precision deep seismic reflection lines were arranged perpendicularly to the fault zone,and data were obtained through special acquisition schemes and processing methods.Finally,the surface position and drilling depth route of WFSD-4 are determined based on the interpretation results of seismic profiles.The seismic reflection method for site selection of the Wenchuan earthquake fault scientific drilling is proven feasible by comparing the interpretation with the actual drilling results,laying the foundation for further study on the deep structures of fault zones.
