Afiqah Ismail , Ahmad Safuan A Rashid , Ali Dehghanbanadaki , Rafiuddin Hakim Roslan , Mohd Firdaus Md Dan @ Azlan , Abd Wahid Rasib , Radzuan Saari , Mushairry Mustaffar , Azman Kassim , Rini Asnida Abdullah , Khairul Hazman Padil , Norbazlan Mohd Yusof , Norisam Abd Rahaman
The prediction of slope stability is a complex nonlinear problem. This paper proposes a new method based on the random forest (RF) algorithm to study the rocky slopes stability. Taking the Bukit Merah, Perak and Twin Peak (Kuala Lumpur) as the study area, the slope characteristics of geometrical parameters are obtained from a multidisciplinary approach (consisting of geological, geotechnical, and remote sensing analyses). 18 factors, including rock strength, rock quality designation (RQD), joint spacing, continuity, openness, roughness, filling, weathering, water seepage, temperature, vegetation index, water index, and orientation, are selected to construct model input variables while the factor of safety (FOS) functions as an output. The area under the curve (AUC) value of the receiver operating characteristic (ROC) curve is obtained with precision and accuracy and used to analyse the predictive model ability. With a large training set and predicted parameters, an area under the ROC curve (the AUC) of 0.95 is achieved. A precision score of 0.88 is obtained, indicating that the model has a low false positive rate and correctly identifies a substantial number of true positives. The findings emphasise the importance of using a variety of terrain characteristics and different approaches to characterise the rock slope.
{"title":"Enhancing rock slope stability prediction using random forest machine learning: A case study","authors":"Afiqah Ismail , Ahmad Safuan A Rashid , Ali Dehghanbanadaki , Rafiuddin Hakim Roslan , Mohd Firdaus Md Dan @ Azlan , Abd Wahid Rasib , Radzuan Saari , Mushairry Mustaffar , Azman Kassim , Rini Asnida Abdullah , Khairul Hazman Padil , Norbazlan Mohd Yusof , Norisam Abd Rahaman","doi":"10.31035/cg2023102","DOIUrl":"10.31035/cg2023102","url":null,"abstract":"<div><div>The prediction of slope stability is a complex nonlinear problem. This paper proposes a new method based on the random forest (RF) algorithm to study the rocky slopes stability. Taking the Bukit Merah, Perak and Twin Peak (Kuala Lumpur) as the study area, the slope characteristics of geometrical parameters are obtained from a multidisciplinary approach (consisting of geological, geotechnical, and remote sensing analyses). 18 factors, including rock strength, rock quality designation (RQD), joint spacing, continuity, openness, roughness, filling, weathering, water seepage, temperature, vegetation index, water index, and orientation, are selected to construct model input variables while the factor of safety (FOS) functions as an output. The area under the curve (AUC) value of the receiver operating characteristic (ROC) curve is obtained with precision and accuracy and used to analyse the predictive model ability. With a large training set and predicted parameters, an area under the ROC curve (the AUC) of 0.95 is achieved. A precision score of 0.88 is obtained, indicating that the model has a low false positive rate and correctly identifies a substantial number of true positives. The findings emphasise the importance of using a variety of terrain characteristics and different approaches to characterise the rock slope.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 691-706"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537192","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}
Jie Dai , Xiao-dong Pan , Tong Wang , Guo-wu Li , Guan Wang , Shang-ke Xie , Jing Ren , Kun-yang Wang , Ting Li , Tao Wang , Jia-le He , Jin-sha Xu , Gan-fu Shen
Lishiite, (Ca2□)Sr3(CO3)5, is a new mineral species from Shaxiongdong, Hubei Province, China. It mainly occours as conchoidal crystals and with combination of hexagonal prism and pyramid and is associated with calcite, K-feldspar, albite, aegirine, apatite, and ancylite-(Ce)(?) and strontianite etc. Lishiite is brittle with conchiform fracture and has a Mohs hardness of approximately 4 and none cleavages were observed. The Vickers microhardness (VHN10) is 197.42 kg/mm2 (range: 166.88 kg/mm2 to 214.58 kg/mm2), and the calculated density of lishiite is 3.696 g/cm3 . Hand specimen of lishiite are yellow-brown. The empirical chemical formula of the lishiite is A(Ca1.18Sr0.25Na0.19□1.38)Σ3.00B[Sr2.17(Ce0.42La0.24Nd0.09Eu0.01)Σ0.76 Ba0.07]Σ3.00 (C5.05O15). As a member of the burbankite group, the general formula of lishiite follows the general formula A3B3(CO3)5, where A=Na, Ca, or and B=Sr, Ba, REE, or Ca. Its crystal structure is hexagonal (space group P63mc) with unit cell parameters a=10.4898(5) Å, c=6.4167(5) Å, and V=611.47(6) Å3, characterized by layers of AO8 and BO10 polyhedra connected to [CO3]3− groups. The discovery of lishiite provides new insights into the evolutionary history of rare earth element (REE) carbonate deposit formation.
{"title":"Lishiite, (Ca2□)Sr3(CO3)5, a new burbankite mineral from carbonatite-syenite complex in Shaxiongdong, Hubei, China","authors":"Jie Dai , Xiao-dong Pan , Tong Wang , Guo-wu Li , Guan Wang , Shang-ke Xie , Jing Ren , Kun-yang Wang , Ting Li , Tao Wang , Jia-le He , Jin-sha Xu , Gan-fu Shen","doi":"10.31035/cg2025163","DOIUrl":"10.31035/cg2025163","url":null,"abstract":"<div><div>Lishiite, (Ca<sub>2</sub>□)Sr<sub>3</sub>(CO<sub>3</sub>)<sub>5</sub>, is a new mineral species from Shaxiongdong, Hubei Province, China. It mainly occours as conchoidal crystals and with combination of hexagonal prism and pyramid and is associated with calcite, K-feldspar, albite, aegirine, apatite, and ancylite-(Ce)(?) and strontianite etc. Lishiite is brittle with conchiform fracture and has a Mohs hardness of approximately 4 and none cleavages were observed. The Vickers microhardness (VHN10) is 197.42 kg/mm<sup>2</sup> (range: 166.88 kg/mm<sup>2</sup> to 214.58 kg/mm<sup>2</sup>), and the calculated density of lishiite is 3.696 g/cm<sup>3 .</sup> Hand specimen of lishiite are yellow-brown. The empirical chemical formula of the lishiite is <sup><em>A</em></sup>(Ca<sub>1.18</sub>Sr<sub>0.25</sub>Na<sub>0.19</sub>□<sub>1.38</sub>)<sub>Σ3.00</sub> <sup><em>B</em></sup>[Sr<sub>2.17</sub>(Ce<sub>0.42</sub>La<sub>0.24</sub>Nd<sub>0.09</sub>Eu<sub>0.01</sub>)<sub>Σ0.76</sub> Ba<sub>0.07</sub>]<sub>Σ3.00</sub> (C<sub>5.05</sub>O<sub>15</sub>). As a member of the burbankite group, the general formula of lishiite follows the general formula <em>A</em><sub>3</sub><em>B</em><sub>3</sub>(CO<sub>3</sub>)<sub>5</sub>, where <em>A</em>=Na, Ca, or and <em>B</em>=Sr, Ba, <em>REE</em>, or Ca. Its crystal structure is hexagonal (space group <em>P</em>6<sub>3</sub><em>mc</em>) with unit cell parameters a=10.4898(5) Å, c=6.4167(5) Å, and V=611.47(6) Å<sup>3</sup>, characterized by layers of <em>A</em>O<sub>8</sub> and <em>B</em>O<sub>10</sub> polyhedra connected to [CO<sub>3</sub>]<sup>3−</sup> groups. The discovery of lishiite provides new insights into the evolutionary history of rare earth element (REE) carbonate deposit formation.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 797-805"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537179","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}
Xiao-xu Liu , Guang-hui Wu , Li-xin Chen , Bing-shan Ma , Zhou Su , Bo Yang , Xia Wang , Bin Zhao
The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×109 t, the fault-related fractures are important for hydrocarbon accumulation. In this paper, the basic parameters such as density and width of fractures are counted and classified, and the effects of fractures on reservoirs are analyzed. The results show that: (1) Structural fractures and stylolite were widely developed in Halahatang area and experienced at least three stages of activity based on the infilling materials and crosscutting relationship. (2) Fracture density, width, aperture, and dip angle vary in different wells, but the relationship between the above parameters and the distance to the fault core indicates the fracture differences in the fault damage zone and further provides a method to divide the inner units in the fault damage zone. In addition, oil and gas wells with high production mainly concentrate in the inner unit. (3) The infilling materials and degree of fractures vary. Fractures formed in the early stage are more filled and less open, while the fractures formed in the late stage are relatively less filled and more open. (4) Fractures improve porosity to a certain extent but greatly increase permeability, especially in the inner zone of fault damage zone with large quantity, multiple inclinations, less filling and large width. These features contribute to the formation of a higher-quality reservoir, further improving oil and gas production. This paper provides a quantitative characterization method for the study of strike-slip fault-related fracture-caved reservoirs, and points out that fault damage zone, especially the inner zone of the fault damage zone, is the potential goal for oil and gas exploration.
{"title":"Characteristics of strike-slip fault-related fractures and their controls on reservoir in Halahatang area, northern Tarim Basin","authors":"Xiao-xu Liu , Guang-hui Wu , Li-xin Chen , Bing-shan Ma , Zhou Su , Bo Yang , Xia Wang , Bin Zhao","doi":"10.31035/cg2023085","DOIUrl":"10.31035/cg2023085","url":null,"abstract":"<div><div>The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×10<sup>9</sup> t, the fault-related fractures are important for hydrocarbon accumulation. In this paper, the basic parameters such as density and width of fractures are counted and classified, and the effects of fractures on reservoirs are analyzed. The results show that: (1) Structural fractures and stylolite were widely developed in Halahatang area and experienced at least three stages of activity based on the infilling materials and crosscutting relationship. (2) Fracture density, width, aperture, and dip angle vary in different wells, but the relationship between the above parameters and the distance to the fault core indicates the fracture differences in the fault damage zone and further provides a method to divide the inner units in the fault damage zone. In addition, oil and gas wells with high production mainly concentrate in the inner unit. (3) The infilling materials and degree of fractures vary. Fractures formed in the early stage are more filled and less open, while the fractures formed in the late stage are relatively less filled and more open. (4) Fractures improve porosity to a certain extent but greatly increase permeability, especially in the inner zone of fault damage zone with large quantity, multiple inclinations, less filling and large width. These features contribute to the formation of a higher-quality reservoir, further improving oil and gas production. This paper provides a quantitative characterization method for the study of strike-slip fault-related fracture-caved reservoirs, and points out that fault damage zone, especially the inner zone of the fault damage zone, is the potential goal for oil and gas exploration.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 740-753"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537195","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}
Jia-wei Zhang , Chang-ling Liu , Yong-chao Zhang , Le-le Liu , Yun-kai Ji
Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources, however, its application to gas hydrate reservoirs has been rarely studied. Currently, there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs, as well as the stress interference patterns between fractures. This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluid-solid coupling discrete element method (DEM), and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance. The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30% and that fracture pressure increases with saturation. The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance. The distribution uniformity index (DUI) reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time, with fracturing efficiency depending on the spacing between injection points and the distance between wells. This work may provide reference for the commercial exploitation of natural gas hydrates.
{"title":"Investigation on the fracture propagation for horizontal wells in hydrate reservoirs using a fluid-solid coupling discrete element method","authors":"Jia-wei Zhang , Chang-ling Liu , Yong-chao Zhang , Le-le Liu , Yun-kai Ji","doi":"10.31035/cg2024031","DOIUrl":"10.31035/cg2024031","url":null,"abstract":"<div><div>Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources, however, its application to gas hydrate reservoirs has been rarely studied. Currently, there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs, as well as the stress interference patterns between fractures. This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluid-solid coupling discrete element method (DEM), and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance. The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30% and that fracture pressure increases with saturation. The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance. The distribution uniformity index (DUI) reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time, with fracturing efficiency depending on the spacing between injection points and the distance between wells. This work may provide reference for the commercial exploitation of natural gas hydrates.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 765-778"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537110","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}
Hong-chao Zhang , Hong-bing Zhou , Bo Yan , Chong-bo Sun , Yue-zhong Wang , Yun-chuan Zhao , Yao Wen , Ren-liang Cao , Yang Qin , Hong-qi Tan
{"title":"Zircon U-Pb dating of metagabbro masses from the Liwu Group Complex within the Taka dome: Geochronological constraints on the Indosinian–Yanshanian tectonic events in western Sichuan, China","authors":"Hong-chao Zhang , Hong-bing Zhou , Bo Yan , Chong-bo Sun , Yue-zhong Wang , Yun-chuan Zhao , Yao Wen , Ren-liang Cao , Yang Qin , Hong-qi Tan","doi":"10.31035/cg2023126","DOIUrl":"10.31035/cg2023126","url":null,"abstract":"","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 865-868"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537188","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}
Jun-wei Bo , Zheng-jiang Ding , Jun Deng , Feng-yue Sun , Kun-feng Qiu , Ming-chun Song
Since the first discovery of gold deposits on the northeastern margin of the Jiaolai Basin in Shandong Province at the end of the 20th century, seven medium-sized to large/super-large gold deposits have been identified in this region, with cumulative proven gold resources of 223 t. This study reviewed the metallogenic and geochemical characteristics of various gold deposits in this region, examined the sources of their ore-forming fluids and materials, as well as their gold metallogenic epochs and processes, and developed a gold metallogenic model. The gold deposits in this region are governed by both dense fractures and detachment structural systems along basin margins, primarily categorized into the altered rock type and the pyrite-bearing carbonate vein type. The latter type, a recently discovered mineralization type in the Jiaodong Peninsula, enjoys high gold grade, a large scale, and high gold mineral fineness, suggesting considerable prospecting potential. Both types of gold deposits show metallogenic epochs ranging from 116 Ma to 119 Ma. Their ore-forming fluids are identified as a CO2-NaCl-H2O fluid system characterized by moderate to low temperatures, moderate to low salinity, and low density, with the pyrite-bearing carbonate vein-type gold deposits manifesting slightly higher salinity. The C-H-O, S, and Pb isotopes of hydrothermal minerals reveal that the ore-forming fluids and materials are characteristic of crust-mantle mixing. Specifically, they were derived from mantle fluids in the early stages, mixed with stratum water and meteoric water in the later stages for mineralization. The gold metallogenic process is identified as follows: During the Early Cretaceous, the subduction of the Pacific Plate and the destruction of the North China Craton led to asthenospheric upwelling. The resulting fluids, after metasomatizing the enriched mantle, differentiated and evolved into C-H-O ore-bearing fluids, which were then mixed with crustal fluids. The mixed fluids migrated to the shallow crust, where they mingled with stratum water and meteoric water. Then, the fluids underwent unloading and final mineralization in detachment fault tectonic systems on basin margins. Due to differences in mixed crustal materials or the surrounding rocks involved in water-rock interactions, altered rock- and pyrite-bearing carbonate vein-type gold deposits were formed in acidic and alkaline fluid environments, respectively.
{"title":"Metallogenic characteristics and mineralization of supergiant gold deposits (223 t) in the northeastern margin of the Jiaolai Basin, Shandong Province: A review","authors":"Jun-wei Bo , Zheng-jiang Ding , Jun Deng , Feng-yue Sun , Kun-feng Qiu , Ming-chun Song","doi":"10.31035/cg2023122","DOIUrl":"10.31035/cg2023122","url":null,"abstract":"<div><div>Since the first discovery of gold deposits on the northeastern margin of the Jiaolai Basin in Shandong Province at the end of the 20<sup>th</sup> century, seven medium-sized to large/super-large gold deposits have been identified in this region, with cumulative proven gold resources of 223 t. This study reviewed the metallogenic and geochemical characteristics of various gold deposits in this region, examined the sources of their ore-forming fluids and materials, as well as their gold metallogenic epochs and processes, and developed a gold metallogenic model. The gold deposits in this region are governed by both dense fractures and detachment structural systems along basin margins, primarily categorized into the altered rock type and the pyrite-bearing carbonate vein type. The latter type, a recently discovered mineralization type in the Jiaodong Peninsula, enjoys high gold grade, a large scale, and high gold mineral fineness, suggesting considerable prospecting potential. Both types of gold deposits show metallogenic epochs ranging from 116 Ma to 119 Ma. Their ore-forming fluids are identified as a CO<sub>2</sub>-NaCl-H<sub>2</sub>O fluid system characterized by moderate to low temperatures, moderate to low salinity, and low density, with the pyrite-bearing carbonate vein-type gold deposits manifesting slightly higher salinity. The C-H-O, S, and Pb isotopes of hydrothermal minerals reveal that the ore-forming fluids and materials are characteristic of crust-mantle mixing. Specifically, they were derived from mantle fluids in the early stages, mixed with stratum water and meteoric water in the later stages for mineralization. The gold metallogenic process is identified as follows: During the Early Cretaceous, the subduction of the Pacific Plate and the destruction of the North China Craton led to asthenospheric upwelling. The resulting fluids, after metasomatizing the enriched mantle, differentiated and evolved into C-H-O ore-bearing fluids, which were then mixed with crustal fluids. The mixed fluids migrated to the shallow crust, where they mingled with stratum water and meteoric water. Then, the fluids underwent unloading and final mineralization in detachment fault tectonic systems on basin margins. Due to differences in mixed crustal materials or the surrounding rocks involved in water-rock interactions, altered rock- and pyrite-bearing carbonate vein-type gold deposits were formed in acidic and alkaline fluid environments, respectively.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 806-842"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537185","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}
Hao Cheng , Wei Hong , Zhen-kai Zhang , Zeng-lin Hong , Zi-yao Wang , Yu-xuan Dong
This study investigated the impacts of random negative training datasets (NTDs) on the uncertainty of machine learning models for geologic hazard susceptibility assessment of the Loess Plateau, northern Shaanxi Province, China. Based on randomly generated 40 NTDs, the study developed models for the geologic hazard susceptibility assessment using the random forest algorithm and evaluated their performances using the area under the receiver operating characteristic curve (AUC). Specifically, the means and standard deviations of the AUC values from all models were then utilized to assess the overall spatial correlation between the conditioning factors and the susceptibility assessment, as well as the uncertainty introduced by the NTDs. A risk and return methodology was thus employed to quantify and mitigate the uncertainty, with log odds ratios used to characterize the susceptibility assessment levels. The risk and return values were calculated based on the standard deviations and means of the log odds ratios of various locations. After the mean log odds ratios were converted into probability values, the final susceptibility map was plotted, which accounts for the uncertainty induced by random NTDs. The results indicate that the AUC values of the models ranged from 0.810 to 0.963, with an average of 0.852 and a standard deviation of 0.035, indicating encouraging prediction effects and certain uncertainty. The risk and return analysis reveals that low- risk and high-return areas suggest lower standard deviations and higher means across multiple model-derived assessments. Overall, this study introduces a new framework for quantifying the uncertainty of multiple training and evaluation models, aimed at improving their robustness and reliability. Additionally, by identifying low-risk and high-return areas, resource allocation for geologic hazard prevention and control can be optimized, thus ensuring that limited resources are directed toward the most effective prevention and control measures.
{"title":"Impacts of random negative training datasets on machine learning-based geologic hazard susceptibility assessment","authors":"Hao Cheng , Wei Hong , Zhen-kai Zhang , Zeng-lin Hong , Zi-yao Wang , Yu-xuan Dong","doi":"10.31035/cg2024094","DOIUrl":"10.31035/cg2024094","url":null,"abstract":"<div><div>This study investigated the impacts of random negative training datasets (NTDs) on the uncertainty of machine learning models for geologic hazard susceptibility assessment of the Loess Plateau, northern Shaanxi Province, China. Based on randomly generated 40 NTDs, the study developed models for the geologic hazard susceptibility assessment using the random forest algorithm and evaluated their performances using the area under the receiver operating characteristic curve (AUC). Specifically, the means and standard deviations of the AUC values from all models were then utilized to assess the overall spatial correlation between the conditioning factors and the susceptibility assessment, as well as the uncertainty introduced by the NTDs. A <em>risk</em> and <em>return</em> methodology was thus employed to quantify and mitigate the uncertainty, with log odds ratios used to characterize the susceptibility assessment levels. The <em>risk</em> and <em>return</em> values were calculated based on the standard deviations and means of the log odds ratios of various locations. After the mean log odds ratios were converted into probability values, the final susceptibility map was plotted, which accounts for the uncertainty induced by random NTDs. The results indicate that the AUC values of the models ranged from 0.810 to 0.963, with an average of 0.852 and a standard deviation of 0.035, indicating encouraging prediction effects and certain uncertainty. The <em>risk</em> and <em>return</em> analysis reveals that low- <em>risk</em> and high-<em>return</em> areas suggest lower standard deviations and higher means across multiple model-derived assessments. Overall, this study introduces a new framework for quantifying the uncertainty of multiple training and evaluation models, aimed at improving their robustness and reliability. Additionally, by identifying low-<em>risk</em> and high-<em>return</em> areas, resource allocation for geologic hazard prevention and control can be optimized, thus ensuring that limited resources are directed toward the most effective prevention and control measures.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 676-690"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537191","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}
Yu-mao Pang , Zhao-meng Wei , Xing-wei Guo , Chuan-sheng Yang , Rui-shan Ma , Xun-hua Zhang
Shale gas is abundant in the Paleozoic of the Yangtze Platform, and several high-yield shale gas fields have been built in the Upper Yangtze Platform, China. The Permian of the South Yellow Sea Basin (SYSB) in the Lower Yangtze area is considered a potential target for shale gas exploration; however, the fundamental geological conditions of shale gas have not been studied. Based on the first whole-cored scientific drilling borehole (CSDP-2) in the SYSB, detailed tests involving petrology, organic geochemistry, and reservoir physical properties were conducted to evaluate the shale gas potential of the Lower Permian. The Lower Permian is dominated by organic-rich siliceous, clay, and clay-mixed shales. The average total organic carbon content is 5.99%, and the organic matter is mainly type II1−II2, which has entered the high-over mature evolution stage. The pore types of organic-rich shales mainly include organic pores, dissolution pores, and intergranular pores, of which the meso-/macropores are well developed. The average porosity is 3.04%, and the total specific surface area and pore volume are 3.47 m2/g and 7.21×10−3 cm3/g, respectively. The average Langmuir volume obtained from the methane adsorption isotherms is 2.70 cm3/g, and methane is mainly adsorbed in the meso-/macropores. The lower Permian shales are rich in methane as indicated by gas logging results, with an average content of 7.3%, which can reach up to 65.9%. A comparison of the study area with typical shale gas fields shows that the Lower Permian is brittle and shallowly buried and has a high potential for shale gas exploration and low-cost development. The depression areas of the SYSB are overlain by thick Mesozoic–Cenozoic sediments, show higher organic matter maturity, and may have greater shale gas potential. The shale gas exploration breakthrough of the study area is of great significance to ensure the energy supply of economically developed areas on the east China.
{"title":"Shale gas prospect of the Lower Permian in the South Yellow Sea Basin of the Lower Yangtze area: Insights from the whole-cored CSDP-2 borehole","authors":"Yu-mao Pang , Zhao-meng Wei , Xing-wei Guo , Chuan-sheng Yang , Rui-shan Ma , Xun-hua Zhang","doi":"10.31035/cg2023153","DOIUrl":"10.31035/cg2023153","url":null,"abstract":"<div><div>Shale gas is abundant in the Paleozoic of the Yangtze Platform, and several high-yield shale gas fields have been built in the Upper Yangtze Platform, China. The Permian of the South Yellow Sea Basin (SYSB) in the Lower Yangtze area is considered a potential target for shale gas exploration; however, the fundamental geological conditions of shale gas have not been studied. Based on the first whole-cored scientific drilling borehole (CSDP-2) in the SYSB, detailed tests involving petrology, organic geochemistry, and reservoir physical properties were conducted to evaluate the shale gas potential of the Lower Permian. The Lower Permian is dominated by organic-rich siliceous, clay, and clay-mixed shales. The average total organic carbon content is 5.99%, and the organic matter is mainly type II<sub>1</sub>−II<sub>2</sub>, which has entered the high-over mature evolution stage. The pore types of organic-rich shales mainly include organic pores, dissolution pores, and intergranular pores, of which the meso-/macropores are well developed. The average porosity is 3.04%, and the total specific surface area and pore volume are 3.47 m<sup>2</sup>/g and 7.21×10<sup>−3</sup> cm<sup>3</sup>/g, respectively. The average Langmuir volume obtained from the methane adsorption isotherms is 2.70 cm<sup>3</sup>/g, and methane is mainly adsorbed in the meso-/macropores. The lower Permian shales are rich in methane as indicated by gas logging results, with an average content of 7.3%, which can reach up to 65.9%. A comparison of the study area with typical shale gas fields shows that the Lower Permian is brittle and shallowly buried and has a high potential for shale gas exploration and low-cost development. The depression areas of the SYSB are overlain by thick Mesozoic–Cenozoic sediments, show higher organic matter maturity, and may have greater shale gas potential. The shale gas exploration breakthrough of the study area is of great significance to ensure the energy supply of economically developed areas on the east China.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 707-724"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537194","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}
Renat Shakirov , Vladimir Luchin , Evgeniya Petrova , Neng-you Wu , Yi-zhao Wan
This study was used oceanographic database in the Sea of Okhotsk between the period from 1929 to 2020 (131286 stations). The paper used gas hydrate dissociation parameters for the “pure methane-seawater” system obtained in the study by Dickens GR and Quinby-Hunt MS. The results have elucidated the spatiotemporal variability of distribution of such parameters at the upper boundary of the gas hydrate stability zone (GHSZ) as water temperature, salinity, and top depth of the stability zone. As the study has shown (based on average long-term spatial distributions), the minimum temperature and depth values of the GHSZ upper boundary in the Sea of Okhotsk occur off the western and southwestern parts of the water area. The maximum temperature and depth values of the GHSZ upper boundary are typical of the southeastern sea area and over the Kamchatka Peninsula slope. This study has also identified an area, where there are no thermobaric conditions for the emergence and stable existence of methane hydrates in the water column. The results presented agree well with the materials of observations conducted during expeditions and the previous data of predictive simulations for the Sea of Okhotsk.
{"title":"Spatial and temporal variations in parameters at the upper boundary of gas hydrate stability zone of the Sea of Okhotsk","authors":"Renat Shakirov , Vladimir Luchin , Evgeniya Petrova , Neng-you Wu , Yi-zhao Wan","doi":"10.31035/cg2024087","DOIUrl":"10.31035/cg2024087","url":null,"abstract":"<div><div>This study was used oceanographic database in the Sea of Okhotsk between the period from 1929 to 2020 (131286 stations). The paper used gas hydrate dissociation parameters for the “pure methane-seawater” system obtained in the study by Dickens GR and Quinby-Hunt MS. The results have elucidated the spatiotemporal variability of distribution of such parameters at the upper boundary of the gas hydrate stability zone (GHSZ) as water temperature, salinity, and top depth of the stability zone. As the study has shown (based on average long-term spatial distributions), the minimum temperature and depth values of the GHSZ upper boundary in the Sea of Okhotsk occur off the western and southwestern parts of the water area. The maximum temperature and depth values of the GHSZ upper boundary are typical of the southeastern sea area and over the Kamchatka Peninsula slope. This study has also identified an area, where there are no thermobaric conditions for the emergence and stable existence of methane hydrates in the water column. The results presented agree well with the materials of observations conducted during expeditions and the previous data of predictive simulations for the Sea of Okhotsk.</div></div>","PeriodicalId":45329,"journal":{"name":"China Geology","volume":"8 4","pages":"Pages 754-764"},"PeriodicalIF":4.7,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145537196","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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