Geological Journal of China Universities

Sedimentology and Carbon Isotope Records of Latest Early Permian Carbonate Platform Drowning Event in Lower Yangtze Region

ZHANG Xiaoji, HU Xiumian, LI Juan, XU Yiwei

2024, 30(04): 379-396. DOI: 10.16108/j.issn1006-7493.2023030

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The Lower Yangtze region in South China plate was located near the equator during the Early Permian, where the shallow-water carbonates of the Qixia Fornation widely developed. The latter were subsequently replaced by the black shale and siliceous rocks of the Gufeng Formation, representing a carbonate platform drowning event at the end of Early Permian. In this study, the carbonate microfacies and carbon isotopic stratigraphy of the Qixia and Gufeng formations were systematically studied in the Pingdingshan section of Chaohu, Anhui Province and Zhengpanshan section of Jurong, Jiangsu Province in order to explore the mechanism of this depositional event. Microfacies data shows that the uppermost of the Qixia Formation can be divided into 9 microfacies, belonging to the inner ramp to middle ramp environment. The lowermost of the Gufeng Formation can be divided into 5 lithofacies, indicating a deep-water basin environment. The depositional environment and paleo-water depth at the boundary between the Qixia and Gufeng formations changed obviously, representing the drowning event of the carbonate platform during the Latest Early Permian. At the same place, sudden drop in the content of calcium carbonate, negative carbon isotope excursion and obviously positive carbon isotope of organic excursion indicate the suddenness and eventuality of carbonate platform drowning. The results show that there is a mirror image relationship between δ13Ccarb of carbon isotope and δ13Corg of organic matter. Carbon isotopes of carbonate and organic matter show decoupling changes of negative and positive excursions, respectively, which may be the result of terrigenous organic matter input. We suggest that the drowning of carbonate platform may be caused by relative sea level rise.

Detrital Zircon U-Pb Geochronology and Geological Significance of the Triassic Strata from Aolaoshan Area, in the West Section of North#br# Qaidam Basin

WANG Bo, WU Zhixiong, HU Junjie, MA Licheng, MA Yinsheng, SHI Hui

2024, 30(04): 397-408. DOI: 10.16108/j.issn1006-7493.2023038

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A dispute whether there was Triassic sedimentation or not in Qaidam Basin and its later evolution are continuous as yet. Via systematic analysis of detrital zircon geochronometry, rock assemblages and regional stratigraphic correlation on the Triassic
strata from Aolaoshan area, in the west section of north Qaidam Basin, this study aiming at providing evidence for the Triassic stratigraphic framework in the northern margin of Qaidam. The average age of young zircons in the lower part of Tb Triassic Formation is 248 Ma. Considering paleontological data from the underlying Ta strata, the deposition time limit of the Aolaoshan Triassic deposits was Early to Middle Triassic. The detrital zircon U-Pb ages were between 243-260 Ma, 414-538 Ma, 678-857 Ma, 1064-1642 Ma and 1700-2836 Ma. Respectively, indicating that the sedimentary materials may derived from Indosinian magmatic rocks, Upper Devonian recycle material, North Qaidam tectonic belt, Shaliuhe Group and Dakendaban Group. The study area has the same sedimentary characteristics as the Triassic in the Huaitousala area, and they both are markedly different from the Triassic stratigraphic division in Qilian and West Qinling areas. It is suggested that a series of continuous or intermittent sedimentary strata were developed in the northern margin of the Qaidam Basin during the Triassic period. In the early Triassic, influenced by the subduction of the Zongmurong Ocean to the south, the northern margin of the Qaidam Basin began to uplift rapidly. Several sets of sedimentary strata and crystalline basement in the early period were rapidly denudated, and the sedimentary strata dominated by alluvial and alluvial facies were formed near the source fault depression. In the Middle Triassic, the activity intensity of the peripheral tectonic belt tended to be stable on the whole, and the northern margin of the Qaidam basin was in the shallow sea shelf platform sedimentary system with thick-bedded limestone as the main deposits. Until the late Triassic, with the strong continental collision between East Kunlun and Qaidam terrane, the whole Qaidam Basin was rapidly uplifted, and the weakly consolidated Triassic in the basin was large-scale denudated. Some of the weakly consolidated Triassic in the basin was transported eastward to Gonghe Basin, and only part of the depressions were preserved.

Discovery of Volcanic Clay-type Lithium Deposit in Region of Volcanic Rocks Along the Southeastern Coast of China

SHAO Xiaoyang, DENG Fei, ZHANG Zhongjin, WANG Rucheng, LU Xiancai, CHE Xudong

2024, 30(04): 409-417. DOI: 10.16108/j.issn1006-7493.2024031

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We report the lithium enrichment in the late Cretaceous Yetang Formation, located in the Shirenbei Basin, northeast of Guangdong Province. The Li2O content is greater than 0.2%, and can be a target for extracting lithium. Comprehensive crosssections of the Shirenbei Basin, geochemical analyses and lithofacies interpretation suggest that the lithium-enriched layers occur in shale, mudstone and siltstone, located in Middle-Upper Yetang Formation; lithium is mainly stored in clay minerals, whose formation is closely related to volcanic activities. It was initially interpreted as a volcanic-type lithium-rich clay deposit. The basin structure provides the environment for sedimentation and concentration of lithium. The layers containing enriched lithium are approximately 226 meters thick in total, and are in great potential for extracting lithium deposit. This discovery provides fclues on investigating large-scale lithium-rich clay deposits related to volcanic activities along the southeast coast of China.

Geochemical Characteristics and Source Analysis of Late Permian Rare Earth Earth-Rich Rock Series in the Qixi Area of Western Guizhou

LUO Xiangjian, QIN Ying, LU Shufan, ZHANG Jiawei, HUANG Qin, WANG Biao, GONG Daxin, TIAN Enyuan, LIU Guodong

2024, 30(04): 418-430. DOI: 10.16108/j.issn1006-7493.2023035

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Geochemical characteristics and sources of ore-forming material of different lithological sections of the rare earth element (REE)-rich rock series at the base of the first member of the Late Permian Xuanwei Formation in the western Guizhou region are still unclear. This study conducts geochemical analyses of major, trace, and REEs of typical profiles in the western Guizhou and Qixi regions, and explores the geochemical characteristics and sources of ore-forming material of different lithological sections of REE-rich rock series. The results show that the REE-rich rock series can be divided into iron rock section, aluminum rock section, and clastic rock section from bottom to top. Among them, the aluminum clay rock section shows the highest rare earth content, up to 0.76%. The REE-rich rock series is mainly composed of SiO2, Al2O3, FexOy, and TiO2 with a total content of 83.93% to 87.24%; Large ion lithophile elements such as Cs, Rb, Ba, V are depleted, while high-field strength elements such as Zr, Hf, Nb, Ta are stable; The REE distribution patterns are all displayed as right dipping with different lithological sections being characterized by moderate differentiation of light and heavy REEs in the iron rock section, no δCe anomalies, and weak negative δEu anomalies; The degree of differentiation between light and heavy REEs in the aluminum rock section is significant, showing negative δCe and δ Eu anomalies; The light and heavy REE fractionation in the clastic rock section is moderate with a weak positive δCe anomaly and a negative δ Eu anomaly. Based on the ICV values of the samples, La/Sc-Co/Th diagrams, and REE distribution patterns, it is determined that the main sources of the aluminum clay rock section and the clastic rock section are moderately acidic volcanic rocks (not volcanic ash) that were eroded, transported, and deposited, while the source of the iron rock section is nearby basalts.

The Stability of Minerals in Foraminifera Tests under Early Diagenetic Conditions: Implications from Simulation Experiments

KAN Libo, ZHOU Yuefei, LI Xiaosong, WANG Jiayu, XU Liang, XIE Qiaoqin, CHEN Tianhu

2024, 30(04): 431-441. DOI: 10.16108/j.issn1006-7493.2023024

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In order to investigate the stability of carbonates in foraminifera tests under early diagenetic conditions, this study
designed simulation experiments to analyze changes in morphology, structure, and chemical composition of the tests of Nonionella decora (CF1), Ammonia aomoriensis (CF2), and Ammonia tepida (CF3) after being eroded by dissolved S^2-, dissimilatory-iron reducing bacterium (DIRB), and sulfate-reducing bacterium (SRB). Results showed that calcite in the tests of CF1 and CF2 can be dissolved by S^2- when its concentration is above 64 mmol/L; while calcite in the test of CF3 can be dissolved only when S^2- concentration is above 128 mmol/L. The dissolution occurred mainly at the place where cogwheel structure is well-developed. DIRB strongly promoted the dissolution of calcite; while such promotion was not obvious in SRB experiments. Dissolved S^2- did not change the Raman spectroscopy characteristics of calcite in foraminifera tests; while DIRB and SRB led to systematic shifts of 5~7 cm-1. Dissolved S^2-, DIRB, and SRB can promote the dissolution of carbonates in the tests and the homogenization of Mg. Besides, DIRB and SRB can promote the formation of Mg-enriched carbonates in the tests. The results suggest that DIRB is much stronger than dissolved S^2-and SRB to change the composition and structure of foraminifera tests under early diagenetic conditions. However, the effects of SRB cannot be ignored from a long-term perspective.

Sensitivity Analysis of Controlling Factors for Earth Fissures in Aquifer Systems with Abrupt Thickness Changes

ZHANG Huolian, HE Shenlin, ZHANG Yongwei, YU Dejie, GONG Xulong, YE Shujun

2024, 30(04): 442-450. DOI: 10.16108/j.issn1006-7493.2023041

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The “groundwater pumping type” earth fissure disasters caused by excessive exploitation of groundwater widely occur worldwide. Their developments are contributed by both excessive exploitation of groundwater and complex geological and
hydrogeological conditions. The type of earth fissure in aquifer system with abrupt thickness change is a general type of earth fissures. In order to achieve a deeper understanding of the mechanism of this type of earth fissures, the paper designs a numerical experimental test in which earth fissure developes in an aquifer system with abrupt thickness change. Firstly, the finite element method is used to calculate the stress-strain distribution of the aquifer system, and the interface element method is used to calculate rupture development. Then the Sobol global sensitivity analysis method is applied to quantify the impact of four control factors, including aquifer thicknesses ratio, changes in pore water pressure, compression coefficient, and cohesion, on the depth of earth fissure development. The results of numerical test indicate that during the process of pumping groundwater, due to the decrease of pore water pressure, differential compaction and shear stress concentrate continuously increase at the location with abrupt changes in aquifer thickness, which leads to the formation of earth fissure on the ground and further downward expansion. The sensitivity analysis results indicate that the aquifer thicknesses ratio is the most sensitive control factor for the development of earth fissures, the sensitivity of pore water pressure changes is second, the sensitivity of compression coefficient is weak, and cohesion is an insensitive control factor. There is an obvious collaboration between the thicknesses ratio and the changes in pore water pressure. The greater the difference in thickness between aquifers, combined with the greater decrease in pore water pressure, the deeper the development of earth fissures.

Study on Soil Suction Measurement Method Using PSYPRO Dew Point Water Potential Technique

ZHANG Dazhan, TANG Chaosheng, XU Jinjian

2024, 30(04): 451-459. DOI: 10.16108/j.issn1006-7493.2023020

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Soil suction measurement is crucial for the stability assessment of geotechnical engineering, real-time and accurate measurement of suction changes in soil from saturated to dry state has always been a hot topic and challenge in the field of unsaturated soil mechanics. Dew point water potential technique is a novel measurement method of soil suction. This paper detailly introduces the working principle of the PSYPRO dew point water potential meter and the significance of the required debugging parameters, and combines the calibration test and the evaporation test to give the optimal time parameter setting recommendations for the PSYPRO dew point water potential meter to measure different soil suction intervals. In this paper, the PST-55 psychrometer was firstly calibrated with different concentrations of NaCl solutions and the correction coefficient was obtained, and then the laboratory soil evaporation test was carried out, the PST-55 psychrometer and ML3 soil moisture sensor were used to measure the drying process. The changes in soil suction and water content verified the feasibility and accuracy of dew point water potential technique for real-time continuous monitoring of soil suction.

Heat Flow and Deep Temperature Distribution in Kuqa Foreland Basin, Northwestern China

FENG Guanzhong, LIU Shaowen, ZHU Chuangqing, LI Xianglan

2024, 30(04): 460-475. DOI: 10.16108/j.issn1006- 7493.2023021

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Geothermal regime of the sedimentary basins is key for understanding the formation and evolution of the basins and assessing hydrocarbon and geothermal energy, and has attracted much attention from the academia and industrial circles. Kuqa Foreland Basin, located between the Tarim Basin and Southern Tianshan Mountain, is one of major hydrocarbon exploration targets in China, and accurate knowledge of geothermal regime of this basin is beneficial for hydrocarbon potential assessment. Here we integrate updated steady-state temperature logs and oil testing temperature, with thermal properties data, to decipher the thermal characterization of the Kuqa Foreland Basin. The geothermal gradient of the basin ranges from 17.3 to 25.7 ℃ /km, with an average of 21.5±2.6 ℃ /km; while the heat flow varies from 27.4 to 57.9 mW/m2, with a mean of 40.9±7.2 mW/m2. The range and average of estimated formation temperatures at 1000-6000 m in the basin are 26-49 ℃ (36±4.6 ℃ ), 42-82 ℃ (59±7.5 ℃ ), 64-113 ℃ (82±10.3 ℃ ), 85-127 ℃ (102±11.6 ℃ ), 98-140 ℃ (119±12.8 ℃ ) and 110-155 ℃ (133±13.9 ℃ ), respectively. Generally, the present-day thermal state of the Kuqa Foreland Basin is relatively low and the thermal pattern is characterized by hot in the north and east, cold in the south and west, which is attributed to the east-west differences in the thickness of the Cenozoic sediments and the lateral variations in the intensity of active deformation associated with the far field effects of the Indo-Asian continental collision. The large thickness of the sediments in the western part of the basin, which forms the thermal blanketing effects owing to their low thermal conductivities, preventing the transport of heat from the deep to the surface. In addition, the active deformation in the eastern part of the basin is more intense, and the friction heating effect of fault movements is obvious. These two factors are combined to account for the observed present-day geothermal field pattern of Kuqa Foreland Basin.

pH Swing-Evaluation of Economic Potential of Mineralized Carbon Fixation Process of Steel Slag

XIE Kui, ZHAO Liang, ZHU Chen, FENG Henan, SUN Jiajia, ZHOU Yiyang

2024, 30(04): 476-484. DOI: 10.16108/j.issn1006-7493.2023034

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The CO2 mineral sequestration-based ammonium slag recycling carbon sequestration process has promising economic potential and CO2 emission reduction benefits, which can help steel companies achieve high-value comprehensive utilization of steel slag solid waste and waste resources containing CO2 flue gas. Raw material loss, reaction time and impurity ion behavior directly affect the operation cost and product quality of the process, and ultimately determine its application value. In this study, the economic potential of the steel slag ammonium salt recycling carbon fixation process was evaluated through laboratory scale test data, and suggestions were made for process parameter determination and optimization directions from the cost control perspective. The results show that the freshness of the solution remains basically unchanged during 10 cycles of leaching solution, and the main reason for the loss of raw materials is the loss of solution volume; the precipitation process CO2 flow rate reaches 15-20 L/min when the precipitation time drops to 20-30 min, at this time the precipitation process is not a limiting factor of the process operation rate; no obvious enrichment of impurity ions is seen in the circulating solution, and the precipitated calcium carbonate products of ten rounds of reactions are in line with industry standards; the CO2 reduction factor of this process to produce precipitated calcium carbonate is 1.543; the profit of this process to reduce 1 ton of CO2 is 1325.25 RMB, and the profit can reach 1654.74 RMB by reducing the solution loss, which has significant economy.

Prediction of Heavy Metal Content through Fusion of Spatial and Environmental Factors in Machine Learning Models:#br# A Case Study of Naozhou Island

JIA Lili, HU Feiyue, LI Tingting, ZHU Xin, YI Longke

2024, 30(04): 485-495. DOI: 10.16108/j.issn1006-7493.2023033

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Conventional assessment methods of soil heavy metal contamination predominantly depend on spatial interpolation analyses, conducted with data derived from a restricted number of sampling points, thereby often overlooking the influence exerted by environmental covariates such as geological backdrop, human activities, and geographical features on the heavy metal distribution. Predictions based solely on environmental covariates tend to fall short in adequately reflecting the spatial aggregation effects associated with heavy metal dispersion. As such, this paper introduces a novel approach that amalgamates spatial and environmental factors as covariates, employing three models: Random Forest (RF), Extreme Gradient Boosting (XGboost), and Deep Learning Neural Network (DNN), designed to predict the spatial distributions of heavy metals in Naozhou Island. The results underscore the substantial improvement in predictive performance achieved through the integration of spatial elements into the model. To test and enhance the robustness of the improved model, data splitting and external data validation techniques are utilized in this study, and the most optimal model for prediction is selected. Following the prediction results, correlation and clustering analyses were conducted on the heavy metal elements at the data feature level, and a LISA spatial clustering analysis at the spatial distribution level. The analyses reveal that geological factors predominantly dictate the dispersion of Cu, Ni, Cr, and Zn elements within the island, while human activities primarily govern the distribution of Pb, As, Hg. Moreover, the distribution of Cd element is ascertained to be influenced by a combination of human activities and geological background.

The Characteristics of Sandy Conglomerate Reservoir in Mazhong Area of the Junggar Basin and A Nonlinear Inversion Method be Used to Predict It

ZHANG Xiaoshuan, ZHANG Xin, LIAO Qiping, FAN Yafei, LIU jinming, WEI Dongtao

2024, 30(04): 496-504. DOI: 10.16108/j.issn1006- 7493.2023042

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With the discovery of more and more reservoirs in the Lower Triassic Baikouquan Formation sandy conglomerate reservoirs in the slope area of Mahu Depression in recent years, prediction techniques for high-quality sandy conglomerate reservoirs have also attracted the attention of many scholars. This article analyzes the rock casting thin sections, mineral composition analysis, and helium gas porosity measurement results of sandy conglomerate reservoirs in the study area. It is found that the content of plastic debris has a significant impact on the porosity and permeability of the rock. As the content of plastic debris in the rock increases, the porosity and permeability of the rock will decrease. At the same time, sensitive parameter optimization of high-quality reservoirs was carried out using logging data. High quality reservoirs exhibited low natural gamma and high resistivity characteristics on conventional logging curves, and a characteristic curve was constructed to characterize the content of plastic debris. This curve can effectively identify high-quality reservoirs in the study area. In this paper, a nonlinear inversion method using artificial intelligence inversion will be introduced, and we will use this method to predicate the characteristic curve in the study area. When the value of the characteristic curve is less than 0.3, we can have a the area is considered have high-quality reservoir.

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