Pub Date : 2024-11-13DOI: 10.1016/j.jsg.2024.105290
Peng Chen , Siqi Shu , Zhonghai Wu , Tao Wang , Chengjun Feng , Jiamei Liu , Shuai Zhang , Haojie Wang , Kun Li
On 18 December 2023, the Ms 6.2 Jishishan earthquake struck the border region of Gansu province and Qinghai province in the northeastern Tibetan Plateau in China. Field investigations revealed that the 2023 Ms 6.2 Jishishan earthquake produced a ∼1.2-km-long coseismic surface deformation zone with the characteristic centimeter-sized uplift and bulge in the range of 1–13 cm (generally<5 cm), which was mainly restricted to a narrow corridor of 40–50 m in width along an previously-unknown frontal blind fault of the North Lajishan thrust fault zone. In spatial location, the coseismic surface deformation zone corresponds to the core of a late Cenozoic anticline on the hanging wall of blind fault, indicating that the coseismic surface uplift was constrained by the pre-existing tectonic environment.
The North Lajishan thrust fault zone is composed of the west branch fault (F1), east branch fault (F2) and the frontal blind fault (F3), the surveying results document that only the frontal thrust fault (F3) is the Holocene seismically active fault. Thus, the seismogenic fault of the 2023 Ms 6.2 Jishishan earthquake was suggested to be the F3 fault, indicating the northeastward propagation and expansion of the most recent earthquake activities within the North Lajishan thrust fault zone related to the ongoing northeastward shortening of the northeastern Tibetan Plateau accommodating the Eurasia-India continental collision.
{"title":"Coseismic surface deformation and source mechanism of the 2023 Ms 6.2 Jishishan earthquake, northeastern Tibetan Plateau","authors":"Peng Chen , Siqi Shu , Zhonghai Wu , Tao Wang , Chengjun Feng , Jiamei Liu , Shuai Zhang , Haojie Wang , Kun Li","doi":"10.1016/j.jsg.2024.105290","DOIUrl":"10.1016/j.jsg.2024.105290","url":null,"abstract":"<div><div>On 18 December 2023, the Ms 6.2 Jishishan earthquake struck the border region of Gansu province and Qinghai province in the northeastern Tibetan Plateau in China. Field investigations revealed that the 2023 Ms 6.2 Jishishan earthquake produced a ∼1.2-km-long coseismic surface deformation zone with the characteristic centimeter-sized uplift and bulge in the range of 1–13 cm (generally<5 cm), which was mainly restricted to a narrow corridor of 40–50 m in width along an previously-unknown frontal blind fault of the North Lajishan thrust fault zone. In spatial location, the coseismic surface deformation zone corresponds to the core of a late Cenozoic anticline on the hanging wall of blind fault, indicating that the coseismic surface uplift was constrained by the pre-existing tectonic environment.</div><div>The North Lajishan thrust fault zone is composed of the west branch fault (F1), east branch fault (F2) and the frontal blind fault (F3), the surveying results document that only the frontal thrust fault (F3) is the Holocene seismically active fault. Thus, the seismogenic fault of the 2023 Ms 6.2 Jishishan earthquake was suggested to be the F3 fault, indicating the northeastward propagation and expansion of the most recent earthquake activities within the North Lajishan thrust fault zone related to the ongoing northeastward shortening of the northeastern Tibetan Plateau accommodating the Eurasia-India continental collision.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"189 ","pages":"Article 105290"},"PeriodicalIF":2.6,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142663093","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 : 2024-11-08DOI: 10.1016/j.jsg.2024.105287
Frank Thomas , Franz A. Livio , Norberto De Marchi , Raffaele Bitonte
Foreland sectors and foredeep-forebulge systems are affected, as the orogenic wedge migrates, by successive stages of stress states and tectonic deformation, resulting in the development of complex fault networks, even if characterized by limited deformation. The role played by structural inheritance and changes in stress field through time, in influencing the successive re-activations of fault segments, is still a topic to be thoroughly investigated. In this work, thanks to an extensive database made available by courtesy of Energean, we were able to investigate a foreland sector at the margin of the southern Apennines. By means of thickness analysis of the Neogene foredeep sequence and of displacement analysis along the fault network, we documented a shift from forebulge-related extension, in Zanclean, to a new tectonic phase, since Piacenzian, related to a strike slip stress field, possibly related to the activity of the Tremiti Fault Zone. We also characterized the geometry and connectivity of the cover-restricted faults, developing above propagating normal faults and observed a clear correlation between fault propagation tendency and lithological/mechanical layering within the cover units.
{"title":"Lithological control and structural inheritance on faults growth in multilayer foreland sequences","authors":"Frank Thomas , Franz A. Livio , Norberto De Marchi , Raffaele Bitonte","doi":"10.1016/j.jsg.2024.105287","DOIUrl":"10.1016/j.jsg.2024.105287","url":null,"abstract":"<div><div>Foreland sectors and foredeep-forebulge systems are affected, as the orogenic wedge migrates, by successive stages of stress states and tectonic deformation, resulting in the development of complex fault networks, even if characterized by limited deformation. The role played by structural inheritance and changes in stress field through time, in influencing the successive re-activations of fault segments, is still a topic to be thoroughly investigated. In this work, thanks to an extensive database made available by courtesy of Energean, we were able to investigate a foreland sector at the margin of the southern Apennines. By means of thickness analysis of the Neogene foredeep sequence and of displacement analysis along the fault network, we documented a shift from forebulge-related extension, in Zanclean, to a new tectonic phase, since Piacenzian, related to a strike slip stress field, possibly related to the activity of the Tremiti Fault Zone. We also characterized the geometry and connectivity of the cover-restricted faults, developing above propagating normal faults and observed a clear correlation between fault propagation tendency and lithological/mechanical layering within the cover units.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"189 ","pages":"Article 105287"},"PeriodicalIF":2.6,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142663092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Ganzi-Yushu-Xianshuihe fault that lies along the northeastern boundary of the Chuan-Dian crustal fragment provides the opportunity to study the tectonic evolution and geodynamic mechanisms of the southeastern Tibetan Plateau. Apatite (U-Th)/He data from an elevation transect provide robust evidence for the initiation of the Ganzi-Yushu fault. The consistent AHe ages of the lower samples constrain the onset of fault activity to 9.4 ± 1.5 Ma. Moreover, the zircon U-Pb dating and rare earth element (REE) analysis confirm that the Queer Shan and Gaogong granitic plutons were emplaced as a whole and then displaced by the Ganzi-Yushu fault. Combining the total offset of these two plutons and the onset timing of the fault activity yields a long-term average left-lateral strike-slip rate of 7.3–10.8 mm/yr for the Ganzi-Yushu fault. Based on the summarized synchronous deformation in the southeastern Tibetan Plateau, including the initiation of fault activity along the whole Ganzi-Yushu-Xianshuihe fault, the slip reversal of the Red River fault, and the fault activity along a series of left-slip faults in the Indochina block, we suggest that the southward extrusion of the Chuan-Dian crustal fragment and clockwise rotation around the Eastern Himalayan Syntaxis initiated at the middle-late Miocene (15-10 Ma).
{"title":"Cenozoic faulting of the Ganzi-Yushu (Xianshuihe) fault from apatite (U-Th)/He ages and its implications for the tectonic reorganization in the southeastern Tibetan plateau","authors":"Jingxing Yu, Ying Wang, Dewen Zheng, Huiping Zhang, Jianzhang Pang, Jianguo Xiong, Xudong Zhao","doi":"10.1016/j.jsg.2024.105286","DOIUrl":"10.1016/j.jsg.2024.105286","url":null,"abstract":"<div><div>The Ganzi-Yushu-Xianshuihe fault that lies along the northeastern boundary of the Chuan-Dian crustal fragment provides the opportunity to study the tectonic evolution and geodynamic mechanisms of the southeastern Tibetan Plateau. Apatite (U-Th)/He data from an elevation transect provide robust evidence for the initiation of the Ganzi-Yushu fault. The consistent AHe ages of the lower samples constrain the onset of fault activity to 9.4 ± 1.5 Ma. Moreover, the zircon U-Pb dating and rare earth element (REE) analysis confirm that the Queer Shan and Gaogong granitic plutons were emplaced as a whole and then displaced by the Ganzi-Yushu fault. Combining the total offset of these two plutons and the onset timing of the fault activity yields a long-term average left-lateral strike-slip rate of 7.3–10.8 mm/yr for the Ganzi-Yushu fault. Based on the summarized synchronous deformation in the southeastern Tibetan Plateau, including the initiation of fault activity along the whole Ganzi-Yushu-Xianshuihe fault, the slip reversal of the Red River fault, and the fault activity along a series of left-slip faults in the Indochina block, we suggest that the southward extrusion of the Chuan-Dian crustal fragment and clockwise rotation around the Eastern Himalayan Syntaxis initiated at the middle-late Miocene (15-10 Ma).</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"189 ","pages":"Article 105286"},"PeriodicalIF":2.6,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142663089","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 : 2024-11-04DOI: 10.1016/j.jsg.2024.105276
L.S.B. Oliveira , F.C.C. Nogueira , D.L. Vasconcelos , A. Torabi , B. Alaei , F. Balsamo , F.H.R. Bezerra , J.A.B. Souza
Fault damage zones, composed of sub-seismic deformation structures, are difficult to detect using seismic data. Still, they can be related to fault throw, which is widely measured in the subsurface. This research employs a multiscale approach that integrates outcrop studies with seismic reflection data to investigate the attributes of fault damage zones affecting porous sandstones. We provide an in-depth understanding of the 3D fault zone volume, investigating correlations between geometric attributes of faults (width of damage zone, frequency of subsidiaries structures, and fault termination) in the outcrop and the fault throw in the subsurface, with insights from deformation mechanisms within the fault zone. The methods encompass 1D scanlines to constrain the damage zone width on the outcrop. At the same time, the subsurface analysis uses 3D seismic data, seismic attributes, and deep learning neural network (DNN) fault volumes to interpret fault geometries and quantify fault throws at different depths. Results show that the area presents a complex fault zone with multiple fault sets, deformation bands, and fracture corridors trending mainly NE-SW, NW-SE, and E-W. The integration of surface and subsurface fault data enabled the identification of two portions in each fault set outcropping at the fault tip for E-W/ESE-WNW-striking faults and the central part of the fault for NE-SW-striking faults. Faults with the greatest length do not outcrop with the largest damage zone width since they are outcropping the tip of the fault. The parallel faults overlap their damage zones, increasing the deformation zones in the affected sandstones. Fault throw and damage zone width present a positive correlation. This relation is affected by fault segments and subsidiary faults.
{"title":"Seismic and outcrop-based 3D characterization of fault damage zones in sandstones, Rio do Peixe Basin, Brazil","authors":"L.S.B. Oliveira , F.C.C. Nogueira , D.L. Vasconcelos , A. Torabi , B. Alaei , F. Balsamo , F.H.R. Bezerra , J.A.B. Souza","doi":"10.1016/j.jsg.2024.105276","DOIUrl":"10.1016/j.jsg.2024.105276","url":null,"abstract":"<div><div>Fault damage zones, composed of sub-seismic deformation structures, are difficult to detect using seismic data. Still, they can be related to fault throw, which is widely measured in the subsurface. This research employs a multiscale approach that integrates outcrop studies with seismic reflection data to investigate the attributes of fault damage zones affecting porous sandstones. We provide an in-depth understanding of the 3D fault zone volume, investigating correlations between geometric attributes of faults (width of damage zone, frequency of subsidiaries structures, and fault termination) in the outcrop and the fault throw in the subsurface, with insights from deformation mechanisms within the fault zone. The methods encompass 1D scanlines to constrain the damage zone width on the outcrop. At the same time, the subsurface analysis uses 3D seismic data, seismic attributes, and deep learning neural network (DNN) fault volumes to interpret fault geometries and quantify fault throws at different depths. Results show that the area presents a complex fault zone with multiple fault sets, deformation bands, and fracture corridors trending mainly NE-SW, NW-SE, and E-W. The integration of surface and subsurface fault data enabled the identification of two portions in each fault set outcropping at the fault tip for E-W/ESE-WNW-striking faults and the central part of the fault for NE-SW-striking faults. Faults with the greatest length do not outcrop with the largest damage zone width since they are outcropping the tip of the fault. The parallel faults overlap their damage zones, increasing the deformation zones in the affected sandstones. Fault throw and damage zone width present a positive correlation. This relation is affected by fault segments and subsidiary faults.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"189 ","pages":"Article 105276"},"PeriodicalIF":2.6,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142663091","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 : 2024-11-01DOI: 10.1016/j.jsg.2024.105266
Xi Li , Chenxu Wang , Lichun Chen , Qingyun Zhou , Weidong Luo , Jun Guo
{"title":"Corrigendum to “Activity and motion characteristics on the southern segment of the Red River fault zone, Yunnan Province, China” [J. Struct. Geol. 188 (2024) 105245]","authors":"Xi Li , Chenxu Wang , Lichun Chen , Qingyun Zhou , Weidong Luo , Jun Guo","doi":"10.1016/j.jsg.2024.105266","DOIUrl":"10.1016/j.jsg.2024.105266","url":null,"abstract":"","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"188 ","pages":"Article 105266"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659341","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 : 2024-10-29DOI: 10.1016/j.jsg.2024.105275
Vincent S. Nowaczewski , Daniel M. Sturmer , Benjamin L. Vaughan
The orientations of intra-cratonic uplifts are commonly used to posit modes of boundary tectonism on continental margins during the time of uplift generation. In North America, a quintessential example of this practice is the ongoing interpretation of the late Paleozoic Ancestral Rocky Mountain Orogeny (ARMO). Continental margins active during ARMO uplifts have been subsequently modified or destroyed, and direct evidence for the styles of coeval tectonism obscured by later deformation, especially within the western Cordillera. Thus, there is a sustained history of workers attempting to deduce the tectonic state of late Paleozoic Laurentian margins from the characteristics of recognized uplifts. Here, using a 3D Finite Element Method (FEM) we show that it is necessary to consider the complete picture of continental fringing tectonism to understand how the intracontinental stress field could be compatible with the ARMO uplifts. Of the preexisting models tested, the model including a transform boundary on the western continental margin is most consistent with ARMO uplifts. A new tectonism model is derived including a left-lateral transtensional boundary on the Laurentian western margin and a refined compressional history along the Appalachian-Marathon margin. Modeling suggests that contemporaneous extension along eastern Greenland may have limited northward growth of the ARMO.
{"title":"Towards a comprehensive boundary tectonism model for the late Paleozoic Ancestral Rocky Mountain orogeny","authors":"Vincent S. Nowaczewski , Daniel M. Sturmer , Benjamin L. Vaughan","doi":"10.1016/j.jsg.2024.105275","DOIUrl":"10.1016/j.jsg.2024.105275","url":null,"abstract":"<div><div>The orientations of intra-cratonic uplifts are commonly used to posit modes of boundary tectonism on continental margins during the time of uplift generation. In North America, a quintessential example of this practice is the ongoing interpretation of the late Paleozoic Ancestral Rocky Mountain Orogeny (ARMO). Continental margins active during ARMO uplifts have been subsequently modified or destroyed, and direct evidence for the styles of coeval tectonism obscured by later deformation, especially within the western Cordillera. Thus, there is a sustained history of workers attempting to deduce the tectonic state of late Paleozoic Laurentian margins from the characteristics of recognized uplifts. Here, using a 3D Finite Element Method (FEM) we show that it is necessary to consider the complete picture of continental fringing tectonism to understand how the intracontinental stress field could be compatible with the ARMO uplifts. Of the preexisting models tested, the model including a transform boundary on the western continental margin is most consistent with ARMO uplifts. A new tectonism model is derived including a left-lateral transtensional boundary on the Laurentian western margin and a refined compressional history along the Appalachian-Marathon margin. Modeling suggests that contemporaneous extension along eastern Greenland may have limited northward growth of the ARMO.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"189 ","pages":"Article 105275"},"PeriodicalIF":2.6,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142663090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Extensional collapse is a common late-to post-collisional feature of orogens. It is particularly prominent in the SW Scandinavian Caledonides, where extensional detachments formed progressively from the initial reactivation of the basal thrust zone to the formation of hinterland-dipping extensional shear zones. A mature stage, documented here, involves the development of bivergent (both hinterland- and foreland-dipping) shear zones and associated vertical basement mobilization. The main foreland-facing extensional shear zone in the study area is the Bergen Detachment – an until recently overlooked or misinterpreted structure. This detachment overprints top-to-W mylonitic fabrics related to the earlier Devonian extension stages and developed in response to the updoming of the Baltica basement west of Bergen (the Øygarden Complex) into a late core complex. Our microstructural and textural examinations suggest that for both the Hardangerfjord Shear Zone and the Bergen Detachment, strain was localized by activation of dislocation creep in quartz through the operation of multiple slip systems in the <a> direction, predominantly prism <a> and rhomb <a>. These examinations and existing radiometric age constraints suggest that the progressive shear zone development occurred over maybe as little as 5 million years, under upper to middle greenschist facies conditions. Synkinematic cooling brought both the Bergen Detachment and Hardangerfjord Shear Zone through the ductile-brittle transition zone. The main explanation for this prolonged collapse development is 1) that the early low-angle detachment became too low-angle for continued shearing, giving rise to the first hinterland-dipping set of shear zones, and 2) that the basement weakened rheologically and mobilized gravitationally with the formation of large upright folds with new detachments along their flanks (the bivergent stage), including the Bergen Detachment.
{"title":"The collapse of the Caledonian orogen in SW Norway: Insights from quartz textures","authors":"Carolina Cavalcante , Haakon Fossen , Leonardo Lagoeiro , Rhander Taufner","doi":"10.1016/j.jsg.2024.105274","DOIUrl":"10.1016/j.jsg.2024.105274","url":null,"abstract":"<div><div>Extensional collapse is a common late-to post-collisional feature of orogens. It is particularly prominent in the SW Scandinavian Caledonides, where extensional detachments formed progressively from the initial reactivation of the basal thrust zone to the formation of hinterland-dipping extensional shear zones. A mature stage, documented here, involves the development of bivergent (both hinterland- and foreland-dipping) shear zones and associated vertical basement mobilization. The main foreland-facing extensional shear zone in the study area is the Bergen Detachment – an until recently overlooked or misinterpreted structure. This detachment overprints top-to-W mylonitic fabrics related to the earlier Devonian extension stages and developed in response to the updoming of the Baltica basement west of Bergen (the Øygarden Complex) into a late core complex. Our microstructural and textural examinations suggest that for both the Hardangerfjord Shear Zone and the Bergen Detachment, strain was localized by activation of dislocation creep in quartz through the operation of multiple slip systems in the <a> direction, predominantly prism <a> and rhomb <a>. These examinations and existing radiometric age constraints suggest that the progressive shear zone development occurred over maybe as little as 5 million years, under upper to middle greenschist facies conditions. Synkinematic cooling brought both the Bergen Detachment and Hardangerfjord Shear Zone through the ductile-brittle transition zone. The main explanation for this prolonged collapse development is 1) that the early low-angle detachment became too low-angle for continued shearing, giving rise to the first hinterland-dipping set of shear zones, and 2) that the basement weakened rheologically and mobilized gravitationally with the formation of large upright folds with new detachments along their flanks (the bivergent stage), including the Bergen Detachment.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"189 ","pages":"Article 105274"},"PeriodicalIF":2.6,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.1016/j.jsg.2024.105273
Shixi Liao , Fei Cao , Lin Jiang , Yan Wang , Peijin Li , Chaohua Guo , Lin Pan , Xiao Wang
The complexity and heterogeneity of ultra-deep faulted karst reservoirs pose significant challenges for hydrocarbon exploration. In this study, we integrated remote sensing image analysis, field measurements, and core sample testing to evaluate the characteristics and controlling factors of carbonate reservoir spaces within the Middle and Lower Triassic formations along a regional strike-slip fault in the Qingjiang region of China. The strike-slip fault zone is composed of multiple fault cores and damage zones. Based on differences in damage zone width and linear fault density, the fault zone was subdivided into transtensional and transpressional segmentations. The carbonate reservoirs, primarily developed within the damage zones, consist of fractures, fracture clusters, and cavities. Detailed measurements of the carbonate outcrops were conducted to obtain geometric parameters of the reservoir spaces. Quantitative results indicate that in the transtensional segmentation, the reservoir is dominated by tensile fracture-cavity systems, characterized by larger fracture apertures (0.13–1.25 m), higher linear fracture density (0.38–8.37 m⁻1), and well-developed cavities (0.03–4.84 m2), which contribute to better fluid connectivity and storage capacity. In contrast, the transpressional segmentation is dominated by compressional fracture-fracture cluster systems, with longer fractures (0.11–12.52 m), smaller fracture apertures (0.01–0.94 m), and extensive fracture clusters development (0.18–17.87 m2), but with lower fluid connectivity and limited storage capacity. Mechanical testing results show that the average compressive strength in the transtensional segmentation (133.95 MPa) is significantly higher than that in the transpressional segmentation (70.28 MPa). In terms of mineral composition, the transtensional segmentation has a higher calcite content, whereas the transpressional segmentation is richer in dolomite and quartz. Based on the observed differences in reservoir space characteristics across the strike-slip fault zone, we discussed the combined effects of structural segmentation, formation thickness, rock mechanics, and brittle mineral content on reservoir space development. The study emphasizes that stress conditions (primary factor) and material properties (secondary factor) jointly control fluid migration and storage efficiency in the reservoirs. Additionally, we suggest that the outcrop studies in the Qingjiang region provide valuable geological analogs for faulted karst reservoirs, offering critical insights for improving the precision of carbonate reservoir exploration and optimizing production efficiency.
{"title":"Faulted karst reservoir spaces in Middle-Lower Triassic carbonates, Qingjiang Region, Yangtze block, China","authors":"Shixi Liao , Fei Cao , Lin Jiang , Yan Wang , Peijin Li , Chaohua Guo , Lin Pan , Xiao Wang","doi":"10.1016/j.jsg.2024.105273","DOIUrl":"10.1016/j.jsg.2024.105273","url":null,"abstract":"<div><div>The complexity and heterogeneity of ultra-deep faulted karst reservoirs pose significant challenges for hydrocarbon exploration. In this study, we integrated remote sensing image analysis, field measurements, and core sample testing to evaluate the characteristics and controlling factors of carbonate reservoir spaces within the Middle and Lower Triassic formations along a regional strike-slip fault in the Qingjiang region of China. The strike-slip fault zone is composed of multiple fault cores and damage zones. Based on differences in damage zone width and linear fault density, the fault zone was subdivided into transtensional and transpressional segmentations. The carbonate reservoirs, primarily developed within the damage zones, consist of fractures, fracture clusters, and cavities. Detailed measurements of the carbonate outcrops were conducted to obtain geometric parameters of the reservoir spaces. Quantitative results indicate that in the transtensional segmentation, the reservoir is dominated by tensile fracture-cavity systems, characterized by larger fracture apertures (0.13–1.25 m), higher linear fracture density (0.38–8.37 m⁻<sup>1</sup>), and well-developed cavities (0.03–4.84 m<sup>2</sup>), which contribute to better fluid connectivity and storage capacity. In contrast, the transpressional segmentation is dominated by compressional fracture-fracture cluster systems, with longer fractures (0.11–12.52 m), smaller fracture apertures (0.01–0.94 m), and extensive fracture clusters development (0.18–17.87 m<sup>2</sup>), but with lower fluid connectivity and limited storage capacity. Mechanical testing results show that the average compressive strength in the transtensional segmentation (133.95 MPa) is significantly higher than that in the transpressional segmentation (70.28 MPa). In terms of mineral composition, the transtensional segmentation has a higher calcite content, whereas the transpressional segmentation is richer in dolomite and quartz. Based on the observed differences in reservoir space characteristics across the strike-slip fault zone, we discussed the combined effects of structural segmentation, formation thickness, rock mechanics, and brittle mineral content on reservoir space development. The study emphasizes that stress conditions (primary factor) and material properties (secondary factor) jointly control fluid migration and storage efficiency in the reservoirs. Additionally, we suggest that the outcrop studies in the Qingjiang region provide valuable geological analogs for faulted karst reservoirs, offering critical insights for improving the precision of carbonate reservoir exploration and optimizing production efficiency.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"189 ","pages":"Article 105273"},"PeriodicalIF":2.6,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446498","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 : 2024-10-15DOI: 10.1016/j.jsg.2024.105272
Hongrui Zhang , Thomas Blenkinsop , Zengqian Hou
The Baiyangping district is located in the northern Lanping Basin, SE Tibetan plateau. This area has undergone 80°–90° clockwise rotation around the Eastern Himalayan Syntaxis during the Oligocene–Early Miocene. Three major shear zones (Gaoligong, Biluoxueshan–Chongshan, and Ailao Shan–Red River) define the regional scale architecture that hosts the Baiyangping district. Several N-S structures parallel to the Biluoxueshan-Chongshan shear zone in the Baiyangping district underwent simple shear during ore formation. The Baiyangping district orebodies consist of two conjugate sets of veins (WNW-and NE-striking) and bedding-parallel veins. Block rotation occurred along the main shear zones, and conjugate veins occupied Riedel shear fractures (R and R′). Dilation occurred under progressive simple shear as the veins rotated. Ore-forming fluids migrated upwards into the dilating zones, and interacted with host rocks which buffered the fluids, increasing δ13CPDB values in higher carbon content host rocks, and then sealing the space. Repeated cycles of dilation and cementation formed the orebodies of the Baiyangping district. This study highlights how block rotation can be linked to structures that control ore vein formation at the outcrop scale within obliquely convergent orogenic belts.
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Pub Date : 2024-10-12DOI: 10.1016/j.jsg.2024.105271
Luiza de C. Mendes , Mateus Basso , Juan Villacreces Morales , Guilherme F. Chinelatto , Joan Marie Blanco , Ulisses M.C. Correia , João Paulo Ponte , Gabriela F. Matheus , Marilia M. Camargo , Jean Carlos R. Gavidia , Renato S.P.de Medeiros , Alexandre C. Vidal
<div><div>Faults and fractures are central for characterizing the permeability distribution in carbonate reservoirs since they act as pathways for diagenetic fluids that often favor intense rock dissolution and permeability. Usually, high permeability zones and fractures are not easily recognized in seismic data due to limited resolution and they are often associated with higher concentrations of hydrocarbons or even significant fluid losses during drilling, thus creating a challenge for hydrocarbon exploration. In the Santos Basin, southeast Brazil, the pre-salt carbonate reservoirs from the Barra Velha Formation (BVE) are the main hydrocarbon producers in Brazilian Atlantic margin and well-known for being extremely heterogeneous, exhibiting complex dual-porosity systems. In this study, we built a conceptual model of these fracture zones and non-matrix porosity formation that helped narrowing the understanding of these complex systems. The characterization of faults and fractures was carried out using seismic, well-logs, and borehole image data to understand the influence of these structures in the porosity formation along the Barra Velha Formation. In the study area, three fault sets were defined (F<sub>1</sub>, F<sub>2</sub>, and F<sub>3</sub>) from seismic data. F<sub>1</sub> represents to the larger faults, while the F<sub>3</sub> fault set represents the smaller faults related to the reactivation of F<sub>1</sub>; both sets being oriented NE-SW. The F<sub>2</sub> fault set is associated with the rift formation and is oriented to NNE-SSW. These three fault sets compartmentalized the studied area into different domains, each exhibiting distinct fracture sets. The natural open fractures were formed during the reactivation of rift faults and are oriented mainly NW, NNE-NNW, NE, and ENE and were identified across the entire study area, but with different intensity values. The fracture intensity closely relates to the distance from major faults where the wells with the highest fracture intensity occurs located 150–590 m from the larger F<sub>1</sub> fault set. Scan-lines were conducted throughout the area to determine the fault width, and an average value of 1.2 km was established. Seven non-matrix porosity classes were characterized and classified into stratigraphically concordant and discordant non-matrix pore types at well scale through borehole image interpretation. The Barra Velha Formation exhibit higher occurrence of stratigraphically discordant non-matrix porosity related to fractured zones while stratigraphically concordant non-matrix porosity is mainly controlled by the paleotopography of the study area. Overall, non-matrix porosity formation tends to follow an orientation that suggests a preferential dissolution flow towards NE and ENE directions. Intervals with higher silica content shows a positive correlation with both fracture intensity and stratigraphically discordant non-matrix porosities. This work provides a conceptual model ab
断层和裂缝是描述碳酸盐岩储层渗透率分布特征的核心，因为它们是成岩流体的通道，往往有利于岩石的强烈溶解和渗透。通常，由于分辨率有限，地震数据不易识别高渗透带和断裂，而且它们往往与较高的碳氢化合物浓度或钻探过程中的大量流体损失相关联，从而给碳氢化合物勘探带来了挑战。在巴西东南部的桑托斯盆地，来自 Barra Velha Formation（BVE）的盐前碳酸盐岩储层是巴西大西洋边缘的主要碳氢化合物产地，因其异质性极强、表现出复杂的双孔隙度系统而闻名。在这项研究中，我们建立了这些断裂带和非基质孔隙度形成的概念模型，有助于加深对这些复杂系统的理解。我们利用地震、井录和井眼图像数据对断层和裂缝进行了特征描述，以了解这些结构对 Barra Velha 地层沿线孔隙度形成的影响。在研究区域，根据地震数据确定了三个断层组（F1、F2 和 F3）。F1 代表较大的断层，而 F3 断层组则代表与 F1 重新激活有关的较小断层；两组断层均呈东北-西南走向。F2 断层组与裂谷地层有关，走向为东北-西南。这三个断层组将研究区域划分为不同的区域，每个区域都有不同的断裂组。天然开放断裂是在裂谷断层重新活化过程中形成的，主要走向为 NW、NNE-NNW、NE 和 ENE。断裂强度与主要断层的距离密切相关，断裂强度最高的水井位于距离较大的 F1 断层组 150-590 米处。为确定断层宽度，在整个区域内进行了扫描测线，确定平均值为 1.2 千米。通过井眼图像解释，在油井尺度上确定了七个非基质孔隙度等级，并将其划分为地层一致和不一致的非基质孔隙类型。Barra Velha 地层的地层不和谐非基质孔隙度较高，与断裂带有关，而地层和谐非基质孔隙度主要受研究区域的古地形控制。总体而言，非基质孔隙度的形成方向倾向于向东北和东北方向溶解流动。二氧化硅含量较高的区段与断裂强度和地层不和谐的非基质孔隙度均呈正相关。这项研究为盐前碳酸盐岩中的裂缝和非基质孔隙度分布提供了一个概念模型，有助于解决油田评价和开发过程中一些相关的构造和地层不确定性问题。
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