Abstract. The formation and evolution of the Himalayas are intimately linked to the South Tibetan Detachment System (STDS) in the northern Himalayas. Despite ongoing controversies about the deep structural style of the STDS, understanding the emplacement mechanism of the leucogranite in the North Himalayan gneiss domes (NHGDs) remains challenging due to insufficient information about deep structures. In this study, we characterized the subsurface structure of the STDS on the eastern side of the Tethys Himalayas and analyze the relationship between STDS tectonic activity and the formation of the NHGD. We conducted a deep seismic reflection survey with a line length of over 135 km and performed geological field investigations in the eastern Tethys Himalayas (92° E) from 2017 to 2018. Our findings indicate that the STDS presents as a roof thrust fault of duplex structures in the eastern Tethys Himalayas and displays characteristics of two-phase denudation (STDS-1 and STDS-2) from the Miocene, corresponding to the two-phase Tethys tectonic uplift. The first phase of denudation (STDS-1) led to the exposure of its structure around the Yarlhashampo dome. Both STDS-1 and STDS-2 denudation activities play crucial roles in promoting the partial melting of middle crust metasediments, which subsequently migrated upward to form leucogranite through diapirism in the core of the Yarlhashampo dome.
{"title":"Tectonic interplay between the South Tibetan Detachment System and the North Himalayan genesis dome","authors":"Xinyu Dong, Wenhui Li, Zhanwu Lu, Xingfu Huang, Rui Gao","doi":"10.5194/egusphere-2024-2468","DOIUrl":"https://doi.org/10.5194/egusphere-2024-2468","url":null,"abstract":"<strong>Abstract.</strong> The formation and evolution of the Himalayas are intimately linked to the South Tibetan Detachment System (STDS) in the northern Himalayas. Despite ongoing controversies about the deep structural style of the STDS, understanding the emplacement mechanism of the leucogranite in the North Himalayan gneiss domes (NHGDs) remains challenging due to insufficient information about deep structures. In this study, we characterized the subsurface structure of the STDS on the eastern side of the Tethys Himalayas and analyze the relationship between STDS tectonic activity and the formation of the NHGD. We conducted a deep seismic reflection survey with a line length of over 135 km and performed geological field investigations in the eastern Tethys Himalayas (92° E) from 2017 to 2018. Our findings indicate that the STDS presents as a roof thrust fault of duplex structures in the eastern Tethys Himalayas and displays characteristics of two-phase denudation (STDS-1 and STDS-2) from the Miocene, corresponding to the two-phase Tethys tectonic uplift. The first phase of denudation (STDS-1) led to the exposure of its structure around the Yarlhashampo dome. Both STDS-1 and STDS-2 denudation activities play crucial roles in promoting the partial melting of middle crust metasediments, which subsequently migrated upward to form leucogranite through diapirism in the core of the Yarlhashampo dome.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"12 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Moritz O. Ziegler, Robin Seithel, Thomas Niederhuber, Oliver Heidbach, Thomas Kohl, Birgit Müller, Mojtaba Rajabi, Karsten Reiter, Luisa Röckel
Abstract. The contemporary crustal stress state is primarily driven by gravitational volume forces and plate tectonics. However, there are various smaller-scale sources such as geological structures and stiffness contrast that perturb stresses and deviate them from the regional pattern. For example, borehole stress analysis in numerous cases has revealed abrupt rotations of horizontal stress orientation of up to 90° when faults are crossed. Herein, we investigate the rotation of principal stress axes at a fault by means of a 2D generic numerical model. We focus on the near field of the fault and the damage zone with a fault parameterized as a rock stiffness contrast. A substantial influence of the far-field stress field in terms of the differential stress and in terms of the stress ratio RS=S1/S_3 is shown. Furthermore, the contrast in material properties is the basis for any stress rotation, and in particular the stiffness is demonstrated to have a significant influence. Eventually, the impact of the angle between the fault strike and the orientation of SHmax is demonstrated. Our results show that the stress rotation is negatively correlated with the ratio of principal far-field stresses. A small angle between the far-field stress orientation and the fault facilitates stress rotation. A high contrast in rock stiffness further increases the stress rotation angle. Faults striking perpendicular to the maximum principal stress orientation experience no rotation at all. However, faults oriented parallel to the maximum principal stress orientation experience either no rotation or a 90° rotation, dependent on the ratio of principal stresses and the rock stiffness contrast. A comparison with observations from various boreholes worldwide shows that in general the findings are in agreement, even though the dip angle proves to have an influence on the stress rotation, in particular for shallow-dipping faults.
{"title":"Stress state at faults: the influence of rock stiffness contrast, stress orientation, and ratio","authors":"Moritz O. Ziegler, Robin Seithel, Thomas Niederhuber, Oliver Heidbach, Thomas Kohl, Birgit Müller, Mojtaba Rajabi, Karsten Reiter, Luisa Röckel","doi":"10.5194/se-15-1047-2024","DOIUrl":"https://doi.org/10.5194/se-15-1047-2024","url":null,"abstract":"Abstract. The contemporary crustal stress state is primarily driven by gravitational volume forces and plate tectonics. However, there are various smaller-scale sources such as geological structures and stiffness contrast that perturb stresses and deviate them from the regional pattern. For example, borehole stress analysis in numerous cases has revealed abrupt rotations of horizontal stress orientation of up to 90° when faults are crossed. Herein, we investigate the rotation of principal stress axes at a fault by means of a 2D generic numerical model. We focus on the near field of the fault and the damage zone with a fault parameterized as a rock stiffness contrast. A substantial influence of the far-field stress field in terms of the differential stress and in terms of the stress ratio RS=S1/S_3 is shown. Furthermore, the contrast in material properties is the basis for any stress rotation, and in particular the stiffness is demonstrated to have a significant influence. Eventually, the impact of the angle between the fault strike and the orientation of SHmax is demonstrated. Our results show that the stress rotation is negatively correlated with the ratio of principal far-field stresses. A small angle between the far-field stress orientation and the fault facilitates stress rotation. A high contrast in rock stiffness further increases the stress rotation angle. Faults striking perpendicular to the maximum principal stress orientation experience no rotation at all. However, faults oriented parallel to the maximum principal stress orientation experience either no rotation or a 90° rotation, dependent on the ratio of principal stresses and the rock stiffness contrast. A comparison with observations from various boreholes worldwide shows that in general the findings are in agreement, even though the dip angle proves to have an influence on the stress rotation, in particular for shallow-dipping faults.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"28 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-22DOI: 10.5194/egusphere-2024-1919
Kathrin Behnen, Marian Hertrich, Hansruedi Maurer, Alexis Shakas, Kai Bröker, Claire Epiney, María Blanch Jover, Domenico Giardini
Abstract. The hypothesis of stress-induced seismic anisotropy was tested in the Bedretto Lab, a deep underground rock laboratory in the Swiss alps. Several comprehensive crosshole seismic surveys were acquired to analyze the directional dependency of seismic wave velocities in the undisturbed host rock. This required precise knowledge on the source and receiver positions as well as a good data quality that allow the determination of traveltimes for different wave types. A tilted transverse isotropic (TTI) model could be established that explains the measured data to a first order. All relevant model parameters could be well constrained using P- and S-wave arrival times. However, a systematic misfit distribution indicates that a more complex anisotropy model might be required to fully explain the measurements. This is consistent with our hypothesis that seismic anisotropy has a significant stress-induced component. More controlled laboratory experiments on the centimeter to decimeter scale were performed to validate our field measurements. These measurements show a comparable order of P- and S-wave anisotropy in the rock volume. The knowledge on the driving mechanism for anisotropy in igneous rocks can potentially help to enhance the monitoring of stress field variations during geothermal operations, thereby improving hazard assessment protocols.
摘要应力诱发地震各向异性的假说在瑞士阿尔卑斯山的地下深层岩石实验室 Bedretto Lab 得到了验证。为了分析未受扰动的主岩中地震波速度的方向依赖性，进行了几次全面的横孔地震勘测。这就要求精确了解震源和接收器的位置，以及良好的数据质量，以便确定不同波型的行进时间。可以建立一个倾斜横向各向同性（TTI）模型，对测量数据进行一阶解释。利用 P 波和 S 波的到达时间，可以很好地约束所有相关的模型参数。然而，系统性的不拟合分布表明，可能需要一个更复杂的各向异性模型才能完全解释测量结果。这与我们的假设是一致的，即地震各向异性有很大的应力诱导成分。为了验证我们的实地测量结果，我们在实验室进行了厘米到分米尺度的更多受控实验。这些测量结果表明，岩体中的 P 波和 S 波各向异性具有可比性。对火成岩各向异性驱动机制的了解可能有助于加强对地热作业期间应力场变化的监测，从而改进危险评估规程。
{"title":"Investigation of Seismic Anisotropy in the Undisturbed Rotondo Granite","authors":"Kathrin Behnen, Marian Hertrich, Hansruedi Maurer, Alexis Shakas, Kai Bröker, Claire Epiney, María Blanch Jover, Domenico Giardini","doi":"10.5194/egusphere-2024-1919","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1919","url":null,"abstract":"<strong>Abstract.</strong> The hypothesis of stress-induced seismic anisotropy was tested in the Bedretto Lab, a deep underground rock laboratory in the Swiss alps. Several comprehensive crosshole seismic surveys were acquired to analyze the directional dependency of seismic wave velocities in the undisturbed host rock. This required precise knowledge on the source and receiver positions as well as a good data quality that allow the determination of traveltimes for different wave types. A tilted transverse isotropic (TTI) model could be established that explains the measured data to a first order. All relevant model parameters could be well constrained using P- and S-wave arrival times. However, a systematic misfit distribution indicates that a more complex anisotropy model might be required to fully explain the measurements. This is consistent with our hypothesis that seismic anisotropy has a significant stress-induced component. More controlled laboratory experiments on the centimeter to decimeter scale were performed to validate our field measurements. These measurements show a comparable order of P- and S-wave anisotropy in the rock volume. The knowledge on the driving mechanism for anisotropy in igneous rocks can potentially help to enhance the monitoring of stress field variations during geothermal operations, thereby improving hazard assessment protocols.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"18 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quang Nguyen, Michal Malinowski, Stanisław Mazur, Sergiy Stovba, Małgorzata Ponikowska, Christian Hübscher
Abstract. The structure of the post-Caledonian sedimentary cover in the transition from the Precambrian to the Paleozoic platforms in the Polish sector of the Baltic Sea is a matter of ongoing debate due to the sparsity of quality seismic data and insufficient well data. The new high-resolution BalTec seismic data acquired in 2016 contributed greatly to deciphering the regional geology of the area. Here we show an optimal seismic data-processing workflow for the selected new BalTec seismic profiles offshore Poland, as well as legacy PGI97 regional seismic data. Due to the acquisition in a shallow-water environment, the processing strategy focused on suppressing multiple reflections and guided waves through a cascaded application of modern multiple elimination approaches. We illustrate the potential of the new and re-processed data for focusing seismic interpretation on the area of the Koszalin Fault. In light of the available data, the Koszalin Fault was the main structure controlling Mesozoic subsidence and Late Cretaceous–Paleocene inversion of the eastern portion of the Mid-Polish Trough offshore Poland. The inversion changed its character from thin- to thick-skinned towards the north, away from the Polish coast. The Koszalin Fault reactivated older structural grain inherited from the time of Devonian continental rifting at the margin of Laurussia. The fault runs obliquely to the Caledonian Deformation Front, the feature that remained inactive since its formation at the Silurian–Devonian transition.
{"title":"Post-Caledonian tectonic evolution of the Precambrian and Paleozoic platform boundary zone offshore Poland based on the new and vintage multi-channel reflection seismic data","authors":"Quang Nguyen, Michal Malinowski, Stanisław Mazur, Sergiy Stovba, Małgorzata Ponikowska, Christian Hübscher","doi":"10.5194/se-15-1029-2024","DOIUrl":"https://doi.org/10.5194/se-15-1029-2024","url":null,"abstract":"Abstract. The structure of the post-Caledonian sedimentary cover in the transition from the Precambrian to the Paleozoic platforms in the Polish sector of the Baltic Sea is a matter of ongoing debate due to the sparsity of quality seismic data and insufficient well data. The new high-resolution BalTec seismic data acquired in 2016 contributed greatly to deciphering the regional geology of the area. Here we show an optimal seismic data-processing workflow for the selected new BalTec seismic profiles offshore Poland, as well as legacy PGI97 regional seismic data. Due to the acquisition in a shallow-water environment, the processing strategy focused on suppressing multiple reflections and guided waves through a cascaded application of modern multiple elimination approaches. We illustrate the potential of the new and re-processed data for focusing seismic interpretation on the area of the Koszalin Fault. In light of the available data, the Koszalin Fault was the main structure controlling Mesozoic subsidence and Late Cretaceous–Paleocene inversion of the eastern portion of the Mid-Polish Trough offshore Poland. The inversion changed its character from thin- to thick-skinned towards the north, away from the Polish coast. The Koszalin Fault reactivated older structural grain inherited from the time of Devonian continental rifting at the margin of Laurussia. The fault runs obliquely to the Caledonian Deformation Front, the feature that remained inactive since its formation at the Silurian–Devonian transition.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Frank Zwaan, Tiago M. Alves, Patricia Cadenas, Mohamed Gouiza, Jordan J. J. Phethean, Sascha Brune, Anne C. Glerum
Abstract. Rifting and continental break-up are major research topics within geosciences, and a thorough understanding of the processes involved as well as of the associated natural hazards and natural resources is of great importance to both science and society. As a result, a large body of knowledge is available in the literature, with most of this previous research being focused on tectonic and geodynamic processes and their links to the evolution of rift systems. We believe that the key task for researchers is to make our knowledge of rift systems available and applicable to face current and future societal challenges. In particular, we should embrace a system analysis approach and aim to apply our knowledge to better understand the links between rift processes, natural hazards, and the geo-resources that are of critical importance to realise the energy transition and a sustainable future. The aim of this paper is therefore to provide a first-order framework for such an approach by providing an up-to-date summary of rifting processes, hazards, and geo-resources, followed by an assessment of future challenges and opportunities for research. We address the varied terminology used to characterise rifting in the scientific literature, followed by a description of rifting processes with a focus on the impact of (1) rheology and stain rates, (2) inheritance in three dimensions, (3) magmatism, and (4) surface processes. Subsequently, we describe the considerable natural hazards that occur in rift settings, which are linked to (1) seismicity, (2) magmatism, and (3) mass wasting, and provide some insights into how the impacts of these hazards can be mitigated. Moreover, we classify and describe the geo-resources occurring in rift environments as (1) non-energy resources, (2) geo-energy resources, (3) water and soils, and (4) opportunities for geological storage. Finally, we discuss the main challenges for the future linked to the aforementioned themes and identify numerous opportunities for follow-up research and knowledge application. In particular, we see great potential in systematic knowledge transfer and collaboration between researchers, industry partners, and government bodies, which may be the key to future successes and advancements.
{"title":"(D)rifting in the 21st century: key processes, natural hazards, and geo-resources","authors":"Frank Zwaan, Tiago M. Alves, Patricia Cadenas, Mohamed Gouiza, Jordan J. J. Phethean, Sascha Brune, Anne C. Glerum","doi":"10.5194/se-15-989-2024","DOIUrl":"https://doi.org/10.5194/se-15-989-2024","url":null,"abstract":"Abstract. Rifting and continental break-up are major research topics within geosciences, and a thorough understanding of the processes involved as well as of the associated natural hazards and natural resources is of great importance to both science and society. As a result, a large body of knowledge is available in the literature, with most of this previous research being focused on tectonic and geodynamic processes and their links to the evolution of rift systems. We believe that the key task for researchers is to make our knowledge of rift systems available and applicable to face current and future societal challenges. In particular, we should embrace a system analysis approach and aim to apply our knowledge to better understand the links between rift processes, natural hazards, and the geo-resources that are of critical importance to realise the energy transition and a sustainable future. The aim of this paper is therefore to provide a first-order framework for such an approach by providing an up-to-date summary of rifting processes, hazards, and geo-resources, followed by an assessment of future challenges and opportunities for research. We address the varied terminology used to characterise rifting in the scientific literature, followed by a description of rifting processes with a focus on the impact of (1) rheology and stain rates, (2) inheritance in three dimensions, (3) magmatism, and (4) surface processes. Subsequently, we describe the considerable natural hazards that occur in rift settings, which are linked to (1) seismicity, (2) magmatism, and (3) mass wasting, and provide some insights into how the impacts of these hazards can be mitigated. Moreover, we classify and describe the geo-resources occurring in rift environments as (1) non-energy resources, (2) geo-energy resources, (3) water and soils, and (4) opportunities for geological storage. Finally, we discuss the main challenges for the future linked to the aforementioned themes and identify numerous opportunities for follow-up research and knowledge application. In particular, we see great potential in systematic knowledge transfer and collaboration between researchers, industry partners, and government bodies, which may be the key to future successes and advancements.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"34 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-08DOI: 10.5194/egusphere-2024-1696
Sangmin Ha, Hee-Cheol Kang, Seongjun Lee, Yeong Bae Seong, Jeong-Heon Choi, Seok-Jin Kim, Moon Son
Abstract. Earthquake prediction in intraplate regions, such as South Korea, is challenging due to the complexity of fault zones. This study employed diverse methods and data sources to detect Quaternary surface rupturing along the Yangsan Fault to improve seismic hazard assessment. Paleoseismic data were analyzed to reveal insights into seismic activity, displacement, and structural patterns. Observations from five trench sites indicate at least three faulting events during the Quaternary, with the most recent surface rupturing occurring approximately 3,000 years ago. These events resulted in a cumulative displacement of 3.1–94.0 m and maximum estimated magnitude of 6.7–7.2. The average slip rate of 0.14 mm/yr suggests a quasi-periodic model with possible recurrence intervals exceeding 10,000 years. The structural patterns imply the reactivation of a pre-existing fault core with top-to-the west geometry, causing a dextral strike-slip with a minor reverse component. This study underscores the continuous faulting along the inherited mature fault, the Yangsan Fault, since at least the Early Pleistocene, contributing valuable insights for seismic hazard assessment in the region and offering a broader understanding of intraplate earthquake dynamics for earthquake prediction.
{"title":"Quaternary surface ruptures of the inherited mature Yangsan fault: implications for intraplate earthquakes in Southeastern Korea","authors":"Sangmin Ha, Hee-Cheol Kang, Seongjun Lee, Yeong Bae Seong, Jeong-Heon Choi, Seok-Jin Kim, Moon Son","doi":"10.5194/egusphere-2024-1696","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1696","url":null,"abstract":"<strong>Abstract.</strong> Earthquake prediction in intraplate regions, such as South Korea, is challenging due to the complexity of fault zones. This study employed diverse methods and data sources to detect Quaternary surface rupturing along the Yangsan Fault to improve seismic hazard assessment. Paleoseismic data were analyzed to reveal insights into seismic activity, displacement, and structural patterns. Observations from five trench sites indicate at least three faulting events during the Quaternary, with the most recent surface rupturing occurring approximately 3,000 years ago. These events resulted in a cumulative displacement of 3.1–94.0 m and maximum estimated magnitude of 6.7–7.2. The average slip rate of 0.14 mm/yr suggests a quasi-periodic model with possible recurrence intervals exceeding 10,000 years. The structural patterns imply the reactivation of a pre-existing fault core with top-to-the west geometry, causing a dextral strike-slip with a minor reverse component. This study underscores the continuous faulting along the inherited mature fault, the Yangsan Fault, since at least the Early Pleistocene, contributing valuable insights for seismic hazard assessment in the region and offering a broader understanding of intraplate earthquake dynamics for earthquake prediction.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"35 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141945358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anne C. Glerum, Sascha Brune, Joseph M. Magnall, Philipp Weis, Sarah A. Gleeson
Abstract. To meet the growing global demand for metal resources, new ore deposit discoveries are required. However, finding new high-grade deposits, particularly those not exposed at the Earth's surface, is very challenging. Therefore, understanding the geodynamic controls on the mineralizing processes can help identify new areas for exploration. Here we focus on clastic-dominated Zn–Pb deposits, the largest global resource of zinc and lead, which formed in sedimentary basins of extensional systems. Using numerical modelling of lithospheric extension coupled with surface erosion and sedimentation, we determine the geodynamic conditions required to generate the rare spatiotemporal window where potential metal source rocks, transport pathways, and host sequences are present. We show that the largest potential metal endowment can be expected in narrow asymmetric rifts, where the mineralization window spans about 1–3 Myr in the upper ∼ 4 km of the sedimentary infill close to shore. The narrow asymmetric rift type is characterized by rift migration, a process that successively generates hyper-extended crust through sequential faulting, resulting in one wide and one narrow conjugate margin. Rift migration also leads to (1) a sufficient life span of the migration-side border fault to accommodate a thick submarine package of sediments, including coarse (permeable) continental sediments that can act as source rock; (2) rising asthenosphere beneath the thinned lithosphere and crust, resulting in elevated temperatures in these overlying sediments that are favourable for leaching metals from the source rock; (3) the deposition of organic-rich sediments that form the host rock at shallower burial depths and lower temperatures; and (4) the generation of smaller faults that cut the major basin created by the border fault and provide additional pathways for focused fluid flow from source to host rock. Wide rifts with rift migration can have similarly favourable configurations, but these occur less frequently and less potential source rock is produced, thereby limiting potential metal endowment. In simulations of narrow symmetric rifts, the conditions to form ore deposits are rarely fulfilled. Based on these insights, exploration programmes should prioritize the narrow margins formed in asymmetric rift systems, in particular regions within several tens of kilometres from the paleo-shoreline, where we predict the highest-value deposits to have formed.
{"title":"Geodynamic controls on clastic-dominated base metal deposits","authors":"Anne C. Glerum, Sascha Brune, Joseph M. Magnall, Philipp Weis, Sarah A. Gleeson","doi":"10.5194/se-15-921-2024","DOIUrl":"https://doi.org/10.5194/se-15-921-2024","url":null,"abstract":"Abstract. To meet the growing global demand for metal resources, new ore deposit discoveries are required. However, finding new high-grade deposits, particularly those not exposed at the Earth's surface, is very challenging. Therefore, understanding the geodynamic controls on the mineralizing processes can help identify new areas for exploration. Here we focus on clastic-dominated Zn–Pb deposits, the largest global resource of zinc and lead, which formed in sedimentary basins of extensional systems. Using numerical modelling of lithospheric extension coupled with surface erosion and sedimentation, we determine the geodynamic conditions required to generate the rare spatiotemporal window where potential metal source rocks, transport pathways, and host sequences are present. We show that the largest potential metal endowment can be expected in narrow asymmetric rifts, where the mineralization window spans about 1–3 Myr in the upper ∼ 4 km of the sedimentary infill close to shore. The narrow asymmetric rift type is characterized by rift migration, a process that successively generates hyper-extended crust through sequential faulting, resulting in one wide and one narrow conjugate margin. Rift migration also leads to (1) a sufficient life span of the migration-side border fault to accommodate a thick submarine package of sediments, including coarse (permeable) continental sediments that can act as source rock; (2) rising asthenosphere beneath the thinned lithosphere and crust, resulting in elevated temperatures in these overlying sediments that are favourable for leaching metals from the source rock; (3) the deposition of organic-rich sediments that form the host rock at shallower burial depths and lower temperatures; and (4) the generation of smaller faults that cut the major basin created by the border fault and provide additional pathways for focused fluid flow from source to host rock. Wide rifts with rift migration can have similarly favourable configurations, but these occur less frequently and less potential source rock is produced, thereby limiting potential metal endowment. In simulations of narrow symmetric rifts, the conditions to form ore deposits are rarely fulfilled. Based on these insights, exploration programmes should prioritize the narrow margins formed in asymmetric rift systems, in particular regions within several tens of kilometres from the paleo-shoreline, where we predict the highest-value deposits to have formed.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"44 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141945359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-30DOI: 10.5194/egusphere-2024-2319
Riccardo Asti, Selina Bonini, Giulio Viola, Gianluca Vignaroli
Abstract. Structural inheritance plays a significant role upon the evolution of fault systems in different tectonic settings. Both positive reactivation of pre-orogenic extensional faults and negative reactivation of syn-orogenic reverse faults during orogenic cycles have been extensively studied and documented. By contrast, only few studies have addressed the impact of structural inheritance in regions undergoing polyphase tectonic histories. Here, we present the Monti Martani Fault System (MMFS) case study (Northern Apennines, Italy) as an example of a seismically active region where it is possible to investigate the role of inherited pre-orogenic structural features upon the post-orogenic tectonic evolution. Based on new field structural data from extensional faults that controlled the Plio-Quaternary evolution of the system, we propose that the MMFS does not consist of a kilometer-long L-shaped single normal fault, as previously proposed in the literature, but is instead a set of several NW-SE trending shorter extensional faults arranged in an en-echelon style. Paleostress analysis yielded three distinct extension directions during the Plio-Quaternary post-orogenic extension, which are NE-SW, NNE-SSW and NW-SE. We relate the first two directions to local orientation fluctuations of the regional stress field interacting with moderately oblique inherited structural features, and the latter direction to a short-live orogen-parallel extensional event whose geodynamic causes remain unclear. We suggest that the NE-SW regional post-orogenic extension direction controls the strike of most of the NW-SE Apenninic-trending extensional faults, while the morphostructural trend of the Monti Martani Ridge and of its boundaries with the surrounding Plio-Quaternary Medio Tiberino and Terni basins is controlled by the strike of the ~N-S and ~E-W pre-orogenic (Jurassic) inherited structural features. We also discuss the implications of these observations upon the seismotectonics of the MMFS. Our findings suggest that, in contrast to previous suggestions, the fault system cannot be classified as an active and capable structural feature.
{"title":"Reconciling post-orogenic faulting, paleostress evolution and structural inheritance in the seismogenic Northern Apennines (Italy): Insights from the Monti Martani Fault System","authors":"Riccardo Asti, Selina Bonini, Giulio Viola, Gianluca Vignaroli","doi":"10.5194/egusphere-2024-2319","DOIUrl":"https://doi.org/10.5194/egusphere-2024-2319","url":null,"abstract":"<strong>Abstract.</strong> Structural inheritance plays a significant role upon the evolution of fault systems in different tectonic settings. Both positive reactivation of pre-orogenic extensional faults and negative reactivation of syn-orogenic reverse faults during orogenic cycles have been extensively studied and documented. By contrast, only few studies have addressed the impact of structural inheritance in regions undergoing polyphase tectonic histories. Here, we present the Monti Martani Fault System (MMFS) case study (Northern Apennines, Italy) as an example of a seismically active region where it is possible to investigate the role of inherited pre-orogenic structural features upon the post-orogenic tectonic evolution. Based on new field structural data from extensional faults that controlled the Plio-Quaternary evolution of the system, we propose that the MMFS does not consist of a kilometer-long L-shaped single normal fault, as previously proposed in the literature, but is instead a set of several NW-SE trending shorter extensional faults arranged in an en-echelon style. Paleostress analysis yielded three distinct extension directions during the Plio-Quaternary post-orogenic extension, which are NE-SW, NNE-SSW and NW-SE. We relate the first two directions to local orientation fluctuations of the regional stress field interacting with moderately oblique inherited structural features, and the latter direction to a short-live orogen-parallel extensional event whose geodynamic causes remain unclear. We suggest that the NE-SW regional post-orogenic extension direction controls the strike of most of the NW-SE Apenninic-trending extensional faults, while the morphostructural trend of the Monti Martani Ridge and of its boundaries with the surrounding Plio-Quaternary Medio Tiberino and Terni basins is controlled by the strike of the ~N-S and ~E-W pre-orogenic (Jurassic) inherited structural features. We also discuss the implications of these observations upon the seismotectonics of the MMFS. Our findings suggest that, in contrast to previous suggestions, the fault system cannot be classified as an active and capable structural feature.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"229 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.5194/egusphere-2024-1515
Fabio Cammarano, Henrique Berger Roisenberg, Alessio Conclave, Islam Fadel, Mark van der Meijde
Abstract. Subduction-related geodynamic processes significantly influence plate tectonics and Earth’s evolution, yet their impact on the continental crust remains poorly understood. We investigated the Sardinia-Corsica continental block, situated in the Mediterranean Sea, which has experienced intense subduction-driven geodynamic events. By analyzing P-wave receiver functions from our LiSard seismic network and publicly available stations, we aimed to understand crustal structure and composition. We inferred the Moho depth and examined the P-wave to S-wave velocity ratio (VP /VS ). We interpret our findings considering petrological data, heat flux measurements, and other geophysical information. We found that the Variscan granitoid batholith has the greatest Moho depths in both Sardinia and Corsica. VP /VS ratios (ranging from 1.65 to 1.70) are consistent with average crustal values of SiO2 between 65 % and 70 %. However, in central Corsica, two stations have exceptionally high VP /VS values (>1.80), suggesting the possible presence of serpentinite throughout the crust. In Alpine Corsica, a station exhibited similar high VP /VS values but a shallower Moho depth of 21 km. The western part of Sardinia, where Cenozoic volcanism occurred, also showed a shallower Moho depth (20–25 km) and high VP /VS values. The highest VP /VS value (1.91) is recorded in an area where surface-wave dispersion curves from ambient noise identified the lowest average S-wave velocity and where the highest heat flux has been reported, indicating elevated crustal temperatures and possible presence of melt within the crust. Overall, our results indicate that the recent geodynamic processes have left the granitoid batholith almost intact, with minimal alteration to its composition.
摘要。与俯冲有关的地球动力过程对板块构造和地球演化有重大影响，但人们对它们对大陆地壳的影响仍然知之甚少。我们对位于地中海的撒丁岛-科西嘉大陆块进行了研究，该大陆块经历了强烈的俯冲驱动地球动力事件。通过分析 LiSard 地震网络和公开台站的 P 波接收函数，我们旨在了解地壳结构和组成。我们推断了莫霍深度，并研究了 P 波与 S 波的速度比（VP /VS ）。我们结合岩石学数据、热通量测量和其他地球物理信息对研究结果进行了解释。我们发现，在撒丁岛和科西嘉岛，瓦利斯坎花岗岩岩床的莫霍深度最大。VP/VS比率（从1.65到1.70不等）与地壳中二氧化硅的平均值（65%到70%）相一致。然而，在科西嘉岛中部，有两个站点的 VP /VS 值特别高（1.80），表明整个地壳可能存在蛇绿岩。在科西嘉高山地区，一个站点显示出类似的高 VP /VS 值，但莫霍深较浅，为 21 千米。撒丁岛西部发生过新生代火山活动，该地区的莫霍深也较浅（20-25 千米），VP /VS 值较高。最高的 VP /VS 值（1.91）记录在一个区域，该区域的环境噪声面波频散曲线确定了最低的平均 S 波速度，而且据报道该区域的热通量最高，表明地壳温度升高，地壳内可能存在熔体。总之，我们的研究结果表明，近期的地球动力过程使花岗岩熔岩几乎完好无损，其成分变化极小。
{"title":"On crustal composition of the Sardinia-Corsica continental block inferred from receiver functions","authors":"Fabio Cammarano, Henrique Berger Roisenberg, Alessio Conclave, Islam Fadel, Mark van der Meijde","doi":"10.5194/egusphere-2024-1515","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1515","url":null,"abstract":"<strong>Abstract.</strong> Subduction-related geodynamic processes significantly influence plate tectonics and Earth’s evolution, yet their impact on the continental crust remains poorly understood. We investigated the Sardinia-Corsica continental block, situated in the Mediterranean Sea, which has experienced intense subduction-driven geodynamic events. By analyzing P-wave receiver functions from our LiSard seismic network and publicly available stations, we aimed to understand crustal structure and composition. We inferred the Moho depth and examined the P-wave to S-wave velocity ratio (<em>V<sub>P</sub></em> /<em>V<sub>S</sub></em> ). We interpret our findings considering petrological data, heat flux measurements, and other geophysical information. We found that the Variscan granitoid batholith has the greatest Moho depths in both Sardinia and Corsica. <em>V<sub>P</sub></em> /<em>V<sub>S</sub></em> ratios (ranging from 1.65 to 1.70) are consistent with average crustal values of <em>SiO</em><sub>2</sub> between 65 % and 70 %. However, in central Corsica, two stations have exceptionally high <em>V<sub>P</sub></em> /<em>V<sub>S</sub></em> values (>1.80), suggesting the possible presence of serpentinite throughout the crust. In Alpine Corsica, a station exhibited similar high <em>V<sub>P</sub></em> /<em>V<sub>S</sub></em> values but a shallower Moho depth of 21 km. The western part of Sardinia, where Cenozoic volcanism occurred, also showed a shallower Moho depth (20–25 km) and high <em>V<sub>P</sub></em> /<em>V<sub>S</sub></em> values. The highest <em>V<sub>P</sub></em> /<em>V<sub>S</sub></em> value (1.91) is recorded in an area where surface-wave dispersion curves from ambient noise identified the lowest average S-wave velocity and where the highest heat flux has been reported, indicating elevated crustal temperatures and possible presence of melt within the crust. Overall, our results indicate that the recent geodynamic processes have left the granitoid batholith almost intact, with minimal alteration to its composition.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"131 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141781967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The process of siliceous sponge dissolution during diagenesis was interpreted not only as an important part of marine Si cycle (comprising Si burial) but also as a significant mechanism of chert formation (so-called “chertification”; Maliva and Siever, 1989a). Both ideas were widely accepted by researches and are commonly used in geological studies. New research contradicts these seminal assumptions and indicates that in pre-Eocene marine Si cycle, although siliceous sponges were an important part of the ecosystems, did not play a controlling role in regulating dSi (= dissolved silicon) concentration in the porewater as well as in chert formation. The presented studies based on advanced mineralogical (XRD, EBSD; SEM-EDS) and microtextural (SEM) analysis of rocks and sponge remnants verify the role of siliceous sponges in the formation of Cretaceous siliceous rocks, by studying successions deposited in similar marine environments, which contain abundant fossils of siliceous sponges associated with cherts and authigenic silica polymorphs and those without them. For the first time, the mineralogical and microtextural transformations of siliceous sponge loose spicules/rigid skeletal networks, which led to their preservation as siliceous or pyrite/marcasite infillings and also in form of limonite coatings, are presented. The data presented here about the diagenesis of siliceous sponges skeletons opens the discussion on the usefulness of stable isotopic studies of δ30Si in geological studies of fossils of silicifiers preserved as secondary silica polymorphs (opal-CT).
{"title":"The role of siliceous sponges in pre-Eocene marine Si cycle from the perspective of rock mineralogy","authors":"Agata Jurkowska, Ewa Świerczewska-Gładysz, Szymon Kowalik Filipowicz","doi":"10.5194/egusphere-2024-2003","DOIUrl":"https://doi.org/10.5194/egusphere-2024-2003","url":null,"abstract":"<strong>Abstract.</strong> The process of siliceous sponge dissolution during diagenesis was interpreted not only as an important part of marine Si cycle (comprising Si burial) but also as a significant mechanism of chert formation (so-called “chertification”; Maliva and Siever, 1989a). Both ideas were widely accepted by researches and are commonly used in geological studies. New research contradicts these seminal assumptions and indicates that in pre-Eocene marine Si cycle, although siliceous sponges were an important part of the ecosystems, did not play a controlling role in regulating dSi (= dissolved silicon) concentration in the porewater as well as in chert formation. The presented studies based on advanced mineralogical (XRD, EBSD; SEM-EDS) and microtextural (SEM) analysis of rocks and sponge remnants verify the role of siliceous sponges in the formation of Cretaceous siliceous rocks, by studying successions deposited in similar marine environments, which contain abundant fossils of siliceous sponges associated with cherts and authigenic silica polymorphs and those without them. For the first time, the mineralogical and microtextural transformations of siliceous sponge loose spicules/rigid skeletal networks, which led to their preservation as siliceous or pyrite/marcasite infillings and also in form of limonite coatings, are presented. The data presented here about the diagenesis of siliceous sponges skeletons opens the discussion on the usefulness of stable isotopic studies of δ<sup>30</sup>Si in geological studies of fossils of silicifiers preserved as secondary silica polymorphs (opal-CT).","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"95 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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