Accurately characterizing the basement faults, including their patterns and movements, holds paramount importance for engineers and seismologists in designing foundations, and geotechnical structures and exploring resources. This research explores the efficacy of unsupervised machine learning models to uncover fault networks that structured and deformed the basement interval in the Dibrugarh region of northeast (NE) India. High-quality three-dimensional seismic data from the upper shelf of northeast India is utilized to extract a comprehensive set of geometric attributes. These attributes are analyzed and amalgamated using two distinct unsupervised machine learning models: the self-organizing map (SOM) and the generative topographic mapping (GTM). Each of these models is interpreted and compared to determine the most effective unsupervised machine learning model for illuminating basement faults and associated deformations. The study reveals that the GTM model, in comparison to the SOM, effectively delimited structural details of the fault networks that influenced the basement interval in the study area. Not only did the GTM model highlight the geometry of major fault networks, but it also captured subtle deformations that structurally modulated the basement rock units through geologic time. The methodology proposed in this study could be applied to other basement geologic settings to aid subsurface interpretation.
{"title":"Unsupervised machine learning models applied to basement faults: An example from the Dibrugarh region, NE India","authors":"Priyadarshi Chinmoy Kumar , Partha Pratim Saikia , Heather Bedle , Kalachand Sain","doi":"10.1016/j.jseaes.2024.106446","DOIUrl":"10.1016/j.jseaes.2024.106446","url":null,"abstract":"<div><div>Accurately characterizing the basement faults, including their patterns and movements, holds paramount importance for engineers and seismologists in designing foundations, and geotechnical structures and exploring resources. This research explores the efficacy of unsupervised machine learning models to uncover fault networks that structured and deformed the basement interval in the Dibrugarh region of northeast (NE) India. High-quality three-dimensional seismic data from the upper shelf of northeast India is utilized to extract a comprehensive set of geometric attributes. These attributes are analyzed and amalgamated using two distinct unsupervised machine learning models: the self-organizing map (SOM) and the generative topographic mapping (GTM). Each of these models is interpreted and compared to determine the most effective unsupervised machine learning model for illuminating basement faults and associated deformations. The study reveals that the GTM model, in comparison to the SOM, effectively delimited structural details of the fault networks that influenced the basement interval in the study area. Not only did the GTM model highlight the geometry of major fault networks, but it also captured subtle deformations that structurally modulated the basement rock units through geologic time. The methodology proposed in this study could be applied to other basement geologic settings to aid subsurface interpretation.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106446"},"PeriodicalIF":2.7,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-09DOI: 10.1016/j.jseaes.2024.106443
Changming Wei , Yuzeng Yao , Jianfei Fu , Rongrong Guo , Jing Liu , Sanshi Jia , Yang Xiao
<div><div>The Anshan-Benxi greenstone belt (ABGB) in the northeastern North China Craton (NCC) preserves ∼ 3.88–2.5 Ga basement rocks, among which the Anshan area has been highly studied due to large number of valuable Neoarchean banded iron formations (BIFs) and thick-bedded metasedimentary rocks. However, few researches focus on the metasedimentary rocks of the Waitoushan-Gongchangling-Benxi (WGB) region in the ABGB. Besides, their provenances still remain puzzled. In this study, we present new whole-rock major and trace element data for metasedimentary rocks in the Waitoushan area and collect 59 previously published geochemical datasets for metasedimentary rocks from across the ABGB, with the aim of determining their provenances, particularly their felsic portions. Collectively, the ABGB metasedimentary rocks consist of chlorite amphibole schists, biotite felsic gneisses/schists, phyllites, biotite amphibole gneisses, garnet biotite gneisses, and two-mica quartz schists. Sixty-eight metasedimentary rocks are geochemically classified into greywacke, shale, and Fe-shale. Greywacke, shale and some Fe-shale samples yield fractioned rare earth element (REE) patterns and high REE abundances that are comparable to those of the average Archean upper continental crust (AUCC), whereas the remaining Fe-shale samples exhibit flat REE patterns and low REE abundances due to the low or absence of Th, U, and LREE-enriched minerals, such as monazite and allanite. According to the chemical index of alteration (CIA), chemical index of weathering (CIW) values and A–CN–K diagram, all metasedimentary rocks exhibit weak to moderate degrees of weathering. Narrow SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratios and index of compositional variability (ICV) values greater than 1 indicate low recycling and immaturity. The Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> ratios, REE patterns and abundances imply that the shale and graywacke were derived from predominantly felsic-related rocks, whereas the Fe-shale sources were hybrid provenances of mafic and felsic-related rocks. We summarize 1612 zircon Lu–Hf isotopes and 129 whole-rock Nd isotopes of sedimentary rocks, volcanic rocks and granitic plutons from the ABGB and surrounding areas to determine where the felsic and mafic provenances of the sedimentary rocks in the ABGB originated. The volcanic rocks in the ABGB provide the dominant mafic sources, whereas felsic provenances may have been supplied from the southern Liaoning granitic plutons and felsic volcanic rocks.</div><div>In this study, a metavolcanic rock interbedded with sedimentary rocks yielded a metamorphic age of ∼ 2512 Ma, limiting the minimum depositional age. Combined with the detrital zircon spectrum from the ABGB sedimentary rocks, the depositional ages of these sedimentary rocks range from ∼ 2.53–2.51 Ga. On the basis of arc- and back-arc-related volcanic rocks and the distribution of sedimentary rocks, we propose that these metasedimentary rocks for
{"title":"Diverse provenances and tectonic setting of late Neoarchean metasedimentary rocks from the Anshan-Benxi greenstone belt, North China Craton: Constraints from whole-rock geochemistry and zircon U–Pb–Lu–Hf isotopes","authors":"Changming Wei , Yuzeng Yao , Jianfei Fu , Rongrong Guo , Jing Liu , Sanshi Jia , Yang Xiao","doi":"10.1016/j.jseaes.2024.106443","DOIUrl":"10.1016/j.jseaes.2024.106443","url":null,"abstract":"<div><div>The Anshan-Benxi greenstone belt (ABGB) in the northeastern North China Craton (NCC) preserves ∼ 3.88–2.5 Ga basement rocks, among which the Anshan area has been highly studied due to large number of valuable Neoarchean banded iron formations (BIFs) and thick-bedded metasedimentary rocks. However, few researches focus on the metasedimentary rocks of the Waitoushan-Gongchangling-Benxi (WGB) region in the ABGB. Besides, their provenances still remain puzzled. In this study, we present new whole-rock major and trace element data for metasedimentary rocks in the Waitoushan area and collect 59 previously published geochemical datasets for metasedimentary rocks from across the ABGB, with the aim of determining their provenances, particularly their felsic portions. Collectively, the ABGB metasedimentary rocks consist of chlorite amphibole schists, biotite felsic gneisses/schists, phyllites, biotite amphibole gneisses, garnet biotite gneisses, and two-mica quartz schists. Sixty-eight metasedimentary rocks are geochemically classified into greywacke, shale, and Fe-shale. Greywacke, shale and some Fe-shale samples yield fractioned rare earth element (REE) patterns and high REE abundances that are comparable to those of the average Archean upper continental crust (AUCC), whereas the remaining Fe-shale samples exhibit flat REE patterns and low REE abundances due to the low or absence of Th, U, and LREE-enriched minerals, such as monazite and allanite. According to the chemical index of alteration (CIA), chemical index of weathering (CIW) values and A–CN–K diagram, all metasedimentary rocks exhibit weak to moderate degrees of weathering. Narrow SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratios and index of compositional variability (ICV) values greater than 1 indicate low recycling and immaturity. The Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> ratios, REE patterns and abundances imply that the shale and graywacke were derived from predominantly felsic-related rocks, whereas the Fe-shale sources were hybrid provenances of mafic and felsic-related rocks. We summarize 1612 zircon Lu–Hf isotopes and 129 whole-rock Nd isotopes of sedimentary rocks, volcanic rocks and granitic plutons from the ABGB and surrounding areas to determine where the felsic and mafic provenances of the sedimentary rocks in the ABGB originated. The volcanic rocks in the ABGB provide the dominant mafic sources, whereas felsic provenances may have been supplied from the southern Liaoning granitic plutons and felsic volcanic rocks.</div><div>In this study, a metavolcanic rock interbedded with sedimentary rocks yielded a metamorphic age of ∼ 2512 Ma, limiting the minimum depositional age. Combined with the detrital zircon spectrum from the ABGB sedimentary rocks, the depositional ages of these sedimentary rocks range from ∼ 2.53–2.51 Ga. On the basis of arc- and back-arc-related volcanic rocks and the distribution of sedimentary rocks, we propose that these metasedimentary rocks for","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106443"},"PeriodicalIF":2.7,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-09DOI: 10.1016/j.jseaes.2024.106448
Luan Thanh Pham , Kamal Abdelrahman , K.N.D. Prasad , Saulo Pomponet Oliveira , David Gomez-Ortiz , Ahmed M. Eldosouky
The Rub’ Al-Khali Basin is one of the largest hydrocarbon producing basins in the world. Since the basin is covered by the Quaternary sand sea, its structural configuration is known only from geophysical data. In this study, we determine the structural lineaments and Moho structure of the basin from high resolution gravity data of the WGM2012 model using recently proposed techniques. The spectrum analysis is used to separate anomalies due to sources at different depth levels from Bouguer gravity data. The edge detection techniques are applied to these anomalies to extract the structural lineaments. In addition, the gravity inversion has been used with the purpose to estimate the Moho depth of the area. The obtained results revealed that most of the trends of shallow lineaments are N-S, W-E and NW–SE directions, the major lineament trend of average depth sources is N–S, while the deep lineaments compare favorably with features of the Moho structure. Our gravity inversion shows a thick crust in the southwest part and thinner in the northeast region. The Moho result consistents with seismic studies in the area, while gravity lineaments add local detail to the framework of the East African Orogen, where the N-S trends in the basin are broadly collinear with the dominant East African orogenic trends. This study provides detailed subsurface structures for a better knowledge of the tectonic evolution of the area.
{"title":"Lineament fabric, crustal structure and isostatic state of the Rub’ Al-Khali Basin from gravity data","authors":"Luan Thanh Pham , Kamal Abdelrahman , K.N.D. Prasad , Saulo Pomponet Oliveira , David Gomez-Ortiz , Ahmed M. Eldosouky","doi":"10.1016/j.jseaes.2024.106448","DOIUrl":"10.1016/j.jseaes.2024.106448","url":null,"abstract":"<div><div>The Rub’ Al-Khali Basin is one of the largest hydrocarbon producing basins in the world. Since the basin is covered by the Quaternary sand sea, its structural configuration is known only from geophysical data. In this study, we determine the structural lineaments and Moho structure of the basin from high resolution gravity data of the WGM2012 model using recently proposed techniques. The spectrum analysis is used to separate anomalies due to sources at different depth levels from Bouguer gravity data. The edge detection techniques are applied to these anomalies to extract the structural lineaments. In addition, the gravity inversion has been used with the purpose to estimate the Moho depth of the area. The obtained results revealed that most of the trends of shallow lineaments are N-S, W-E and NW–SE directions, the major lineament trend of average depth sources is N–S, while the deep lineaments compare favorably with features of the Moho structure. Our gravity inversion shows a thick crust in the southwest part and thinner in the northeast region. The Moho result consistents with seismic studies in the area, while gravity lineaments add local detail to the framework of the East African Orogen, where the N-S trends in the basin are broadly collinear with the dominant East African orogenic trends. This study provides detailed subsurface structures for a better knowledge of the tectonic evolution of the area.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106448"},"PeriodicalIF":2.7,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-09DOI: 10.1016/j.jseaes.2024.106449
Haoqing Liu , Weijun Gan , Yujiang Li , Zhangjun Li , Lishen Liu , Ling Zhang , Shiming Liang , Keliang Zhang , Yanchuan Li , Chenglong Dai
The Lajishan-Jishishan Tectonic Belt (LJTB) experienced several strong earthquakes in recent decades despite its low slip rate and low strain rate. The latest 2023 Jishishan MS 6.2 earthquake received special attention for its unusual secondary disasters, which raises the question about the mechanism of frequent strong earthquakes in the tectonic belt. In this study, we construct a three-dimensional (3D) viscoelastic finite element model to analyze the crustal deformation and stress–strain state around the LJTB, considering the effects of fault geometry and lateral rheological heterogeneity. The results show that with the uniform rheology in the mid-lower crust, there is a significant strike-slip component at both end segments and a thrust component in the middle segments of the tectonic belt, and strike-slip and weak thrust deformation in the north segments of the belt, indicating the important role of fault geometry in controlling the regional crustal deformation. The strengthening of rheology in the mid-lower crust benefits the fault slip but subtly influences crustal deformation. For the middle and south segments of the LJTB, the crust experiences intense horizontal compression, and the heterogeneous rheology in the mid-lower crust facilitates fault thrust motion, as indicated by the 2023 Jishishan MS 6.2 earthquake. The crustal deformation around the tectonic belt is attributed to the hybrid crustal shortening and localized mid-lower crustal flow. Under the compressive tectonic stress field, the strain energy gradually increases on the Jishishan fault zone located above the mid-lower crust with high rheology, eventually generating the Jishishan MS 6.2 earthquake.
{"title":"Mechanism of crustal deformation around the Lajishan-Jishishan Tectonic Belt, NE Tibet, and implications for occurrence of the 2023 Jishishan MS 6.2 earthquake","authors":"Haoqing Liu , Weijun Gan , Yujiang Li , Zhangjun Li , Lishen Liu , Ling Zhang , Shiming Liang , Keliang Zhang , Yanchuan Li , Chenglong Dai","doi":"10.1016/j.jseaes.2024.106449","DOIUrl":"10.1016/j.jseaes.2024.106449","url":null,"abstract":"<div><div>The Lajishan-Jishishan Tectonic Belt (LJTB) experienced several strong earthquakes in recent decades despite its low slip rate and low strain rate. The latest 2023 Jishishan <em>M</em><sub>S</sub> 6.2 earthquake received special attention for its unusual secondary disasters, which raises the question about the mechanism of frequent strong earthquakes in the tectonic belt. In this study, we construct a three-dimensional (3D) viscoelastic finite element model to analyze the crustal deformation and stress–strain state around the LJTB, considering the effects of fault geometry and lateral rheological heterogeneity. The results show that with the uniform rheology in the mid-lower crust, there is a significant strike-slip component at both end segments and a thrust component in the middle segments of the tectonic belt, and strike-slip and weak thrust deformation in the north segments of the belt, indicating the important role of fault geometry in controlling the regional crustal deformation. The strengthening of rheology in the mid-lower crust benefits the fault slip but subtly influences crustal deformation. For the middle and south segments of the LJTB, the crust experiences intense horizontal compression, and the heterogeneous rheology in the mid-lower crust facilitates fault thrust motion, as indicated by the 2023 Jishishan <em>M</em><sub>S</sub> 6.2 earthquake. The crustal deformation around the tectonic belt is attributed to the hybrid crustal shortening and localized mid-lower crustal flow. Under the compressive tectonic stress field, the strain energy gradually increases on the Jishishan fault zone located above the mid-lower crust with high rheology, eventually generating the Jishishan <em>M</em><sub>S</sub> 6.2 earthquake.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106449"},"PeriodicalIF":2.7,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-07DOI: 10.1016/j.jseaes.2024.106450
Zijun Wang , Boming Zhao
An earthquake early warning (EEW) system can help to mitigate and reduce seismic hazards. While EEW approaches have been developed globally, improving accuracy remains crucial. In this study, a probability-based EEW method is proposed that enables a more precise site ground motion predication using the initial P-wave from a single station. Based on the earthquake database at the southwestern area of China provided by the China Strong Motion Net Center (CSMNC), a total of 437 seismic records with the criteria that 3.0 ≤ Ms ≤ 7.0 were analysed. We first investigated the representative characteristic parameters from different time windows, and established the regression relationships to estimate the peak ground accelerations. Then by combing those original relationships with the Bayesian theorem, the local priori seismic information represented by the b-value was taking into account to further derive an improved estimation model. Finally, the predicated accuracy from the combined method was compared with that from the original method. A comparison of the standard deviations of the estimation differences between the estimated and actual ground motions revealed that the proposed combined method could enhance the precision of the predictions by 39.4 % to 40.9 % when utilising a 3-second time window. It has been noted that the application of a larger window would further improve the accuracy. The proposed method is expected to promote the reliability of an on-site system for EEW.
{"title":"A probability-based approach for estimating ground motion using initial P-wave for earthquake early warning","authors":"Zijun Wang , Boming Zhao","doi":"10.1016/j.jseaes.2024.106450","DOIUrl":"10.1016/j.jseaes.2024.106450","url":null,"abstract":"<div><div>An earthquake early warning (EEW) system can help to mitigate and reduce seismic hazards. While EEW approaches have been developed globally, improving accuracy remains crucial. In this study, a probability-based EEW method is proposed that enables a more precise site ground motion predication using the initial P-wave from a single station. Based on the earthquake database at the southwestern area of China provided by the China Strong Motion Net Center (CSMNC), a total of 437 seismic records with the criteria that 3.0 ≤ Ms ≤ 7.0 were analysed. We first investigated the representative characteristic parameters from different time windows, and established the regression relationships to estimate the peak ground accelerations. Then by combing those original relationships with the Bayesian theorem, the local priori seismic information represented by the <em>b</em>-value was taking into account to further derive an improved estimation model. Finally, the predicated accuracy from the combined method was compared with that from the original method. A comparison of the standard deviations of the estimation differences between the estimated and actual ground motions revealed that the proposed combined method could enhance the precision of the predictions by 39.4 % to 40.9 % when utilising a 3-second time window. It has been noted that the application of a larger window would further improve the accuracy. The proposed method is expected to promote the reliability of an on-site system for EEW.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106450"},"PeriodicalIF":2.7,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-07DOI: 10.1016/j.jseaes.2024.106444
Tunahan Arık, Alp Ünal, Şafak Altunkaynak
One of the Eocene plutons in NW Anatolia, the Northern Kapıdağ Pluton (NKP) was syn-kinematically intruded into the Kapıdağ Shear Zone (KSZ). The NKP is granodioritic in composition and displays progressive deformation from south to north. The southern part of the NKP is composed of an isotropic granodiorite without any trace of deformation. Towards the north, it gradually passes into a deformed granodiorite in which the development of ductile and brittle structures is clearly observed. The NKP shows a well-developed mylonitic foliation and stretching lineation and several shear sense indicators such as the S-C fabrics and “σ”-type rotated porphyroclasts which indicate a dextral sense of shear. Microstructural investigations suggest that the NKP underwent continuous deformation at temperatures from 600 °C to below 250 °C. The field, structural and geochronological data collectively indicate that the KSZ was active during the early Eocene.
The EBSD and three-dimensional strain analysis results of NKP show that the samples display crystal-preferred orientation and Flinn k values change between 0.92 and 5.32 indicating a transtensional regime. Lode’s ratios of the samples vary from −0.64 to + 0.13 and are plotted in the general constrictional field in the Hsu diagram. The kinematic vorticity numbers (Wk) of the samples change between 0.73 and 0.99 indicating a simple shear domination. Collectively, all of these data indicate that the KSZ is a simple shear-dominated dextral transtensional shear zone. We infer that KSZ was most likely developed as a result of strain localization along the break-off of the Tethyan oceanic slab during the Eocene.
{"title":"An Eocene transtensional shear zone driven by the strain localization along slab break-off: Implications from the sheared syn-kinematic northern Kapıdağ Pluton (NW Anatolia, Turkey)","authors":"Tunahan Arık, Alp Ünal, Şafak Altunkaynak","doi":"10.1016/j.jseaes.2024.106444","DOIUrl":"10.1016/j.jseaes.2024.106444","url":null,"abstract":"<div><div>One of the Eocene plutons in NW Anatolia, the Northern Kapıdağ Pluton (NKP) was <em>syn</em>-kinematically intruded into the Kapıdağ Shear Zone (KSZ). The NKP is granodioritic in composition and displays progressive deformation from south to north. The southern part of the NKP is composed of an isotropic granodiorite without any trace of deformation. Towards the north, it gradually passes into a deformed granodiorite in which the development of ductile and brittle structures is clearly observed. The NKP shows a well-developed mylonitic foliation and stretching lineation and several shear sense indicators such as the S-C fabrics and “σ”-type rotated porphyroclasts which indicate a dextral sense of shear. Microstructural investigations suggest that the NKP underwent continuous deformation at temperatures from 600 °C to below 250 °C. The field, structural and geochronological data collectively indicate that the KSZ was active during the early Eocene.</div><div>The EBSD and three-dimensional strain analysis results of NKP show that the samples display crystal-preferred orientation and Flinn k values change between 0.92 and 5.32 indicating a transtensional regime. Lode’s ratios of the samples vary from −0.64 to + 0.13 and are plotted in the general constrictional field in the Hsu diagram. The kinematic vorticity numbers (Wk) of the samples change between 0.73 and 0.99 indicating a simple shear domination. Collectively, all of these data indicate that the KSZ is a simple shear-dominated dextral transtensional shear zone. We infer that KSZ was most likely developed as a result of strain localization along the break-off of the Tethyan oceanic slab during the Eocene.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106444"},"PeriodicalIF":2.7,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-07DOI: 10.1016/j.jseaes.2024.106442
Yi Liu , Zhipeng Li , Jiyong Li , Fengli Shao , Zhigang Kong , Xuelong Liu , Wenchang Li , Xiuyu Yin
Peninsular Malaysia, known as the world’s producer of tin, has drawn great attention to the close affinity between tin mineralization and granitoids during the Permian-Triassic period. This paper reports new petrography, zircon U-Pb ages, whole-rock geochemical and Sr-Nd-Pb-Hf isotopic data of granitoids from the Gerik pluton in Malaysia Main Range province. These samples consist two compositionally distinctive suites, the low silica series (LSS) represented by biotite granites and the high silica series (HSS) represented by tourmaline-bearing granites. They have identical zircon U-Pb ages of 217–215 Ma. The results of petrology and geochemistry indicate that both the LSS and the HSS originated from a mixed source involving igneous protoliths and crustal metasediments. Furthermore, the LSS are best explained as resulting from the AFC process (assimilation and fractional crystallization). By contrast, the HSS display unusual REE tetrad effect, fractionation of twin-elements (low Nb/Ta, Zr/Hf and high Y/Ho) and variable 87Sr/86Sri (0.7058 to 0.7282), clearly showing melt-fluid interaction during the late magmatic stage. We further infer that the magmatic fluids with unradiogenic Sr isotopes are most likely exotic origin and were derived from deep magma reservoir. The external fluids can migrate efficiently to the shallow part of the crust and interact with the highly evolved granitic melts represented by the HSS. Meanwhile, the magmatic fluids may also bring in plenty of fluid-mobile Sn, which finally developed the most abundant hydrothermal vein-type tin deposits in Peninsular Malaysia.
{"title":"Petrogenesis of Late Triassic granitoids in Peninsular Malaysia, Southeast Asia: Implication for crystal-melt fractionation and melt-fluid interaction during granitic magma differentiation","authors":"Yi Liu , Zhipeng Li , Jiyong Li , Fengli Shao , Zhigang Kong , Xuelong Liu , Wenchang Li , Xiuyu Yin","doi":"10.1016/j.jseaes.2024.106442","DOIUrl":"10.1016/j.jseaes.2024.106442","url":null,"abstract":"<div><div>Peninsular Malaysia, known as the world’s producer of tin, has drawn great attention to the close affinity between tin mineralization and granitoids during the Permian-Triassic period. This paper reports new petrography, zircon U-Pb ages, whole-rock geochemical and Sr-Nd-Pb-Hf isotopic data of granitoids from the Gerik pluton in Malaysia Main Range province. These samples consist two compositionally distinctive suites, the low silica series (LSS) represented by biotite granites and the high silica series (HSS) represented by tourmaline-bearing granites. They have identical zircon U-Pb ages of 217–215 Ma. The results of petrology and geochemistry indicate that both the LSS and the HSS originated from a mixed source involving igneous protoliths and crustal metasediments. Furthermore, the LSS are best explained as resulting from the AFC process (assimilation and fractional crystallization). By contrast, the HSS display unusual REE tetrad effect, fractionation of twin-elements (low Nb/Ta, Zr/Hf and high Y/Ho) and variable <sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub> (0.7058 to 0.7282), clearly showing melt-fluid interaction during the late magmatic stage. We further infer that the magmatic fluids with unradiogenic Sr isotopes are most likely exotic origin and were derived from deep magma reservoir. The external fluids can migrate efficiently to the shallow part of the crust and interact with the highly evolved granitic melts represented by the HSS. Meanwhile, the magmatic fluids may also bring in plenty of fluid-mobile Sn, which finally developed the most abundant hydrothermal vein-type tin deposits in Peninsular Malaysia.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106442"},"PeriodicalIF":2.7,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143146022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on the local seismic events recorded at 207 stations in a dense array across the Jiali fault zone in the Eastern Himalayan Syntaxis, we have investigated the splitting characteristics of shear-waves in the Guxiang-Zhamu section of the Jiali fault zone. A total of 192 pairs of valid shear-wave splitting parameters (fast direction and time delay) at 112 stations are obtained for analysis of the upper crustal anisotropy. The anisotropy results have exhibited significant spatial differences. The consistency of the fast directions with the strikes of faults in the vicinity of the stations suggests that the upper crustal anisotropy in the study area is mainly influenced by the geometries of the faults. The time delays on the north side of the main branch of the Jiali fault zone are significantly larger than those on the south side, which indicates that the tectonic stress has accumulated along the Jiali fault zone because the continuous northward push of the Indian Plate, and the stress accumulated on the north side of the Jiali fault zone is larger than that on the south side due to the geometry of the fault.
{"title":"The upper crustal anisotropy in the Guxiang-Zhamu section of the Jiali fault in the Eastern Himalayan Syntaxis","authors":"Xuelai Cao, Lijun Chang, Zhenyu Wang, Zhifeng Ding","doi":"10.1016/j.jseaes.2024.106440","DOIUrl":"10.1016/j.jseaes.2024.106440","url":null,"abstract":"<div><div>Based on the local seismic events recorded at 207 stations in a dense array across the Jiali fault zone in the Eastern Himalayan Syntaxis, we have investigated the splitting characteristics of shear-waves in the Guxiang-Zhamu section of the Jiali fault zone. A total of 192 pairs of valid shear-wave splitting parameters (fast direction and time delay) at 112 stations are obtained for analysis of the upper crustal anisotropy. The anisotropy results have exhibited significant spatial differences. The consistency of the fast directions with the strikes of faults in the vicinity of the stations suggests that the upper crustal anisotropy in the study area is mainly influenced by the geometries of the faults. The time delays on the north side of the main branch of the Jiali fault zone are significantly larger than those on the south side, which indicates that the tectonic stress has accumulated along the Jiali fault zone because the continuous northward push of the Indian Plate, and the stress accumulated on the north side of the Jiali fault zone is larger than that on the south side due to the geometry of the fault.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106440"},"PeriodicalIF":2.7,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-01DOI: 10.1016/j.jseaes.2024.106432
Liang Fan , Jia Chang , Jian-Wei Li , Ji-Xiang Sui , Shi-Guang Du , Long-Hui Huang
The Dashui gold (Au) deposit is one of the largest Au deposits in West Qinling orogenic belt and unique in that its metallic minerals are dominated by hematite but sulfides are extremely scarce. The age and genesis of the Dashui Au deposit, however, remain poorly constrained. To resolve these issues, here we present robust apatite U-Pb dating results under the context of detailed textural and compositional studies. The ore mineral assemblages at Dashui consist of fine-grained quartz, hematite, kaolinite, apatite, native Au, and trace amounts of pyrite. The presence of hematite and gold as inclusions fully enclosed in quartz and apatite suggests that the former minerals are of primary origin rather than, as generally considered, a product of supergene oxidation of Au-bearing pyrite. Cathodoluminescence imaging reveals that the ores contain two types of apatite. CL-bright apatite was likely inherited from the magmatic wall rocks, whereas CL-dark apatite precipitated coevally with the ore minerals. In-situ LA-ICP-MS U-Pb isotope analysis of the CL-dark apatite suggests that the Dashui deposit formed at 217.2 ± 4.1 Ma, contemporaneously with the main stage of regional Au mineralization in the West Qinling orogenic belt that formed under the Triassic subduction-collisional tectonic setting. Given than Au mineralization at Dashui is temporarily and spatially associated with intermediate to felsic porphyry intrusions, and that the ore sulfides have S isotopes consistent with a magmatic-hydrothermal origin, the deposit can be broadly classified as a Carlin-like Au deposit. Nevertheless, the hematite-rich rather than pyrite-rich ore assemblages indicate an ore-forming environment that was more oxidized than that of typical Carlin-type deposits.
{"title":"U-Pb ages of apatite, sulfur isotopes of sulfides and possible origin of the Dashui hematite-rich, sulfide-deficient gold deposit in the West Qinling orogen, Central China","authors":"Liang Fan , Jia Chang , Jian-Wei Li , Ji-Xiang Sui , Shi-Guang Du , Long-Hui Huang","doi":"10.1016/j.jseaes.2024.106432","DOIUrl":"10.1016/j.jseaes.2024.106432","url":null,"abstract":"<div><div>The Dashui gold (Au) deposit is one of the largest Au deposits in West Qinling orogenic belt and unique in that its metallic minerals are dominated by hematite but sulfides are extremely scarce. The age and genesis of the Dashui Au deposit, however, remain poorly constrained. To resolve these issues, here we present robust apatite U-Pb dating results under the context of detailed textural and compositional studies. The ore mineral assemblages at Dashui consist of fine-grained quartz, hematite, kaolinite, apatite, native Au, and trace amounts of pyrite. The presence of hematite and gold as inclusions fully enclosed in quartz and apatite suggests that the former minerals are of primary origin rather than, as generally considered, a product of supergene oxidation of Au-bearing pyrite. Cathodoluminescence imaging reveals that the ores contain two types of apatite. CL-bright apatite was likely inherited from the magmatic wall rocks, whereas CL-dark apatite precipitated coevally with the ore minerals. <em>In-situ</em> LA-ICP-MS U-Pb isotope analysis of the CL-dark apatite suggests that the Dashui deposit formed at 217.2 ± 4.1 Ma, contemporaneously with the main stage of regional Au mineralization in the West Qinling orogenic belt that formed under the Triassic subduction-collisional tectonic setting. Given than Au mineralization at Dashui is temporarily and spatially associated with intermediate to felsic porphyry intrusions, and that the ore sulfides have S isotopes consistent with a magmatic-hydrothermal origin, the deposit can be broadly classified as a Carlin-like Au deposit. Nevertheless, the hematite-rich rather than pyrite-rich ore assemblages indicate an ore-forming environment that was more oxidized than that of typical Carlin-type deposits.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106432"},"PeriodicalIF":2.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-11-30DOI: 10.1016/j.jseaes.2024.106431
Chikondi Chisenga , Jianguo Yan , Brave Manda , Hakim Saibi , Mohamed Amrouche
Geodynamics of the Arabian Peninsula is less understood as crustal structures are not well delineated due to uneven distribution and lack of seismic measurements and ground based geophysical data in the Arabian interior. To address this, we delineated crustal structures in the Arabian Peninsula through the creation of a crustal thickness model from the inversion of GOCO60s gravity field model, which revealed details on the underlying crustal structures. Our model revealed strong crustal thickness variations in the Zagros fold belt that indicates high deformational history and crustal reworked, which also reflect directional collisional events between the Arabian and Eurasian Plates, similar to the Himalaya type as the result of mantle processes. The resolved crustal structures also reveal a relatively slow rifting process on the southern end of the Red Sea than at the northern end, which resulted in the bulging of crust in the southern part of Zagros Fold Mountains. Further, folding and bulging of crustal structures is more intense near the Arabian Platform and slower on the Eurasian side, which could indicate a relatively stable Eurasian plate compared to the geodynamically active Arabian Plate. Overall improvement in our high-resolution crustal thickness model yields an improved representation of crustal structures over previously derived models of the Arabian Peninsula and the Surrounding plates that indicates a variation in the Proterozoic crust in Arabian Plate, possibly indicating a secular variation in the crustal structure.
{"title":"New insights into the crustal structures of the Arabian Plate and surrounding plates unveiled from the crustal thickness model and its implications for geodynamics","authors":"Chikondi Chisenga , Jianguo Yan , Brave Manda , Hakim Saibi , Mohamed Amrouche","doi":"10.1016/j.jseaes.2024.106431","DOIUrl":"10.1016/j.jseaes.2024.106431","url":null,"abstract":"<div><div>Geodynamics of the Arabian Peninsula is less understood as crustal structures are not well delineated due to uneven distribution and lack of seismic measurements and ground based geophysical data in the Arabian interior. To address this, we delineated crustal structures in the Arabian Peninsula through the creation of a crustal thickness model from the inversion of GOCO60s gravity field model, which revealed details on the underlying crustal structures. Our model revealed strong crustal thickness variations in the Zagros fold belt that indicates high deformational history and crustal reworked, which also reflect directional collisional events between the Arabian and Eurasian Plates, similar to the Himalaya type as the result of mantle processes. The resolved crustal structures also reveal a relatively slow rifting process on the southern end of the Red Sea than at the northern end, which resulted in the bulging of crust in the southern part of Zagros Fold Mountains. Further, folding and bulging of crustal structures is more intense near the Arabian Platform and slower on the Eurasian side, which could indicate a relatively stable Eurasian plate compared to the geodynamically active Arabian Plate. Overall improvement in our high-resolution crustal thickness model yields an improved representation of crustal structures over previously derived models of the Arabian Peninsula and the Surrounding plates that indicates a variation in the Proterozoic crust in Arabian Plate, possibly indicating a secular variation in the crustal structure.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"279 ","pages":"Article 106431"},"PeriodicalIF":2.7,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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