Journal of Earth Science

Petrogenesis of Early Paleozoic Supracrustal Rocks in Southeastern Yunnan: Constraints on Intracontinental Orogeny in the South China Craton

Tao Jiang, Guoqing Wang, Yilong Li, Ke Wang, Haitian Zhang, Limin Zhao, Jiao Wang, Xiujuan Bai, Fraukje M. Brouwer

, Available online , doi: 10.1007/s12583-024-0133-x

[Abstract](33) [PDF 945KB](10)

Abstract:
Early Paleozoic sedimentary rocks and granitoids are widely distributed across the South China Craton, which provides crucial insights into crustal reconstitution. This study examines petrology, zircon U-Pb-Hf isotopes and whole-rock geochemistry of supracrustal rocks in southeastern Yunnan, China. Detrital zircons from the paraschists show ages of 2702-513 Ma, with two main peaks at 665 Ma and 517-514 Ma and a maximum protolith depositional age of ~514 Ma. The protoliths were deposited in a continental arc-related basin at the southwestern Yangtze Craton. The gneissic monzogranite, granodiorite and K-feldspar granite have zircon U-Pb ages of 436 ±3 Ma, 442 ±2 Ma and 441 ±2 Ma, respectively. All samples show A/CNK ratios greater than 1.1, negative εHf_(t) values of -4.87 to -0.38 and TDM2 model ages of 1738-1453 Ma, classifying them as peraluminous S-type granites. They were originated from the partial melting of Paleoproterozoic to Mesoproterozoic crustal materials within a collisional setting. Minor amphibolites and epidote-tremolite schists suggested that some mafic dikes intruded into the paraschists between 452-428 Ma. A 414-400 Ma tectono-thermal event led to the formation of widespread pegmatite veins. The crust in the southwestern South China Craton was thickened at 500-460 Ma to>50 km and remained stable at around 440-420 Ma with low temperatures below 800℃, indicating an early Paleozoic intracontinental orogeny in the South China Craton.

Can Geochemistry Distinguish Extracted Melt from Cumulate with Trapped Melt?

Ke Gao, C. Brenhin Keller, Changqian Ma

, Available online , doi: 10.1007/s12583-024-0128-7

[Abstract](51) [PDF 1587KB](8)

Abstract:
Volcanic and plutonic rocks are crucial to the formation and evolution of the Earth's continental crust, yet the relationship between these rock types remains a topic of ongoing scientific inquiry. A key question is whether crystal-liquid separation within magmatic reservoirs drives the formation of evolved volcanic rocks, with residual cumulates preserved in plutonic bodies. In this study, we test the hypothesis that approximately 30% of the residual melt, trapped within the terminal porosity of the plutonic residue during rhyolitic melt extraction, may obscure the geochemical signature of the cumulate. Using trace- and major-element geochemical modeling, we demonstrate that extracted melts are enriched in incompatible elements and depleted in compatible elements, while the opposite is observed in cumulate residues. Our modeling results show that the geochemical differences between extracted melts and cumulate residues remain distinguishable, even when accounting for the effects of interstitial melt. This suggests that while melt extraction may not be widespread, processes such as cumulate remobilization and other dynamic magmatic interactions could significantly reduce the compositional differences between volcanic and plutonic rocks. Our findings challenge the view that melt extraction is a predominant mechanism responsible for the differentiation of felsic magma on a global scale and highlight the complexity of magmatic processes in the Earth's crust.

Evapotranspiration and its components partitioning based on an improved hydrological model: historical attributions and future projections

Hong Du, Sidong Zeng, Yongyue Ji, Jun Xia

, Available online , doi: 10.1007/s12583-024-0097-x

[Abstract](67) [PDF 2618KB](36)

Abstract:
Estimation and attribution of evapotranspiration (ET) and its components under changing environment is still a challenge but is essential for understanding the mechanisms of water and energy transfer subsequently regional water resources management. In this study, an improved hydrological model is developed to estimate evapotranspiration and its components i.e., evaporation (E) and transpiration (T) by integrated the advantages of hydrological modeling constrained by water balance and the water-carbon close relationships. Results show that the improved hydrological model could captures ET and its components well in the study region. During the past years, annual ET and E increase obviously about 2.40mm/a and 1.42mm/a, particularly in spring and summer accounting for 90%. T shows less increasement and mainly increases in spring while it decreases in summer. Precipitation is the dominant factor and contributes 74.1% and 90.0% increases of annual ET and E, while the attribution of T changes is more complex by coupling of the positive effects of precipitation, rising temperature and interactive influences, the negative effects of solar diming and elevated CO₂. In the future, ET and its components tend to increase under most of the Shared Socioeconomic Pathways (SSP) scenarios except for T decreases under the very high emissions scenario (SSP5-8.5) based on the projections. From seasonal perspective, the changes of ET and the components are mainly in spring and summer accounting for 75%, while more slightly changes are found in autumn and winter. This study highlights the effectiveness of estimating ET and its components by improving hydrological model within water-carbon coupling relationships, and more complex mechanisms of transpiration changes than evapotranspiration and evaporation changes under the interactive effects of climate variability and vegetation dynamics. Besides, decision makers should pay attention to the more increases in the undesirable E than desirable T.

Tourmaline geochemistry as genetic evolution and metallogenic potential indicators of pegmatites: a case study from the Tugeman Be-Li deposit, Middle Altun

Hang Li, Xingwang Xu, Tao Hong, Qiang Ke, Yince Ma, Kai Kang, Zhiquan Yang, Changsheng Guo

, Available online , doi: 10.1007/s12583-024-0040-1

[Abstract](26) [PDF 3722KB](18)

Abstract:
Tourmaline is a common borosilicate mineral in granite and pegmatite, and it is also an important carrier to record the physicochemical evolution information of magmas. However, the genetic relationship between pegmatite-type rare metal mineralization potential and tourmaline-bearing pegmatites is not clear, and the tourmaline geochemical indication of the mineralization type of rare metals needs to be supplemented. In the middle Altun region, extensive tourmaline-bearing pegmatite dykes are prevalent within and surrounding the Tugeman complex. In this paper, the petrology and geochemical characteristics of tourmaline within the pegmatite of the Tugeman Be-Li deposit have been comprehensively analyzed. The research delves into the genetic evolution and metallogenic potential of the pegmatite, emphasizing the indicative role of tourmaline geochemistry in discerning mineralization types in the Tugeman Be-Li deposit. Major and trace element analysis of tourmaline reveals varying contents of FeO (9.37-17.10 wt%), Al₂O₃ (28.64-35.22% wt%), and MgO (0.13-2.47 wt%) in the Tugeman Be-Li pegmatite. Li, Zn, and Sn contents range from 204 ppm to 1590 ppm, 1143 ppm to 4089 ppm, and 74 ppm to 396 ppm, respectively. The tourmaline analyzed in this study is magmatic origin and belongs to schorl series, exhibits substitution relationships, including (Na, Fe²⁺)(^X□, Al)_-1, (Fe²⁺, Fe³⁺)(Mg, Al)_-1, (Al, ^X□)(R²⁺, Na)_-1, (Na, Mg)(^X□, Al)_-1 and ^X□NaR²⁺_-1. The trace element data of tourmaline show that lithium has four enrichment stages in different mineral crystallization phases. Notably, the tendency of tourmaline in the Tugeman Be-Li pegmatite to evolve towards elbaite implies a magmatic evolution sequence from low to high, transitioning through microcline-albite pegmatite, muscovite-microcline-albite pegmatite, albite pegmatite, and microcline pegmatite. Furthermore, we also propose that the Sc content in schorl can serve as an indicator of pegmatite mineralization type and the Tugeman Be-Li pegmatite has evolved to a beryllium-rich stage and has certain lithium enrichment potential.

Heterogeneous characteristics of various lamina assemblage in shale of Shahejie Formation of the Zhanhua Sag, Bohai Bay Basin, eastern China

Xiaolin Wang, Xiaomin Zhu, Jin Lai, Xingyue Lin, Yushan Du, Yurui Zhu

, Available online , doi: 10.1007/s12583-024-0054-8

[Abstract](102) [PDF 2273KB](52)

Abstract:
The Eocene Shahejie Formation in the Zhanhua Sag of the Bohai Bay Basin has abundant shale oil resources. However, lacustrine shale is heterogeneous in mineralogy, sedimentary structure, organic matter, pore structure, paleoenvironment, and oil content. Therefore, the laminae assemblages are divided into laminated (lamina thickness of < 0.01 m), layered (0.01~0.1 m) and massive (no layer or layer spacing of > 0.1 m) types shale to investigate the core, X-ray diffraction (XRD), thin section, field emission-scanning electron microscopy (FE-SEM), mercury injection capillary pressure (MICP), N₂ adsorption and geochemical experiments. The results show that the oil shale of Shahejie Formation in Zhanhua Sag is abundant in calcite. The TOC content ranges between 1.35% and 5.55%. Rock-Eval S₁ and S₂ values range from 0.30 to 2.56 mg/g and 0.97~15.47 mg/g, respectively. Variable kinds of nanopores, micropores, and microfractures are commonly observed. The connectivity of pores in laminated and layered shale samples is relatively better than massive shale. The massive shale was formed in a sedimentary environment with warm and humid climate, moderate salinity, weak reduction conditions, high productivity, and paleo-setting rate. Organic matter is derived from lower bacteria, algae, and terrigenous plants. Laminated and layered shale are formed in an arid and cold environment with high salinity, strong reducibility, low paleo-setting rate. Laminated shale is located on a gentle slope at the basin margin, which is the focus of shale oil exploration because of their higher hydrocarbon generation potential, reservoir quality, and advantaged horizontal fracturing conditions. The above results have implication for the sweet spots prediction in shales with similar geological setting.

A Study on the Genetic Dynamics and Development Characteristics of Granitic Rock Avalanches in the Northern Qinling Mountains, China

Yan Lyu, Ruixia Ma, Zuopeng Wang, Jianbing Peng, Tianzhuo Gu

, Available online , doi: 10.1007/s12583-024-0016-1

[Abstract](137) [PDF 2288KB](52)

Abstract:
Massive granitic rock avalanches are extensively developed in the middle section of the northern Qinling Mountains (NQM), China. The current consensus is that their formation could have been connected with seismic events that occurred in the NQM. However, there is a lack of systematic discussion on the genetic dynamics of these rock avalanches. Hence, taking Earth system scientific research as a starting point, this paper systematically summarizes and discusses development characteristics, formation times and genetic dynamic mechanisms of granitic rock avalanches in the NQM based on geological investigations, high-precision remote sensing interpretations, geomorphological dating, geophysical exploration, and a large-scale shaking table model test. We identified 53 granitic rock avalanches in this area, with a single collapse area ranging from 0.01×10⁶ to 1.71×10⁶ m². Their development time can be divided into six stages, namely, 107297~106289 years BP, 11870-11950 years BP, 11666~10279 years BP, 2260-2320 years BP, 1788-1925 years BP, and 1392~1661 years BP, which were closely related to multiple prehistoric or ancient earthquakes. We suggest that long-term coupling of internal and external earth dynamics was responsible for the granitic rock avalanches in the NQM; the internal dynamics were mainly related to subduction, collision and extrusion of different plates under the Qinling terrane, leading to the formation and tectonic uplift of the Qinling orogenic belt; and the external dynamics were closely associated with climate changes resulting in mountain denudation, freeze‒thaw cycles and isostatic balance uplift. In this process, the formation and evolution of the Qinling orogenic belt play a geohazard-pregnant role, structural planes, including faults and joints, play a geohazard-controlled role, and earthquakes play a geohazard-induced role, which jointly results in the occurrence of large-scale granitic rock avalanches in the NQM. This research can not only decipher the genetic dynamic mechanism of large hard granitic rock avalanches but also reveal temporal and spatial patterns of the evolution of breeding and the generation of large-scale rock avalanches in the margins of orogenic belts.

Surveying organic matter, thermal maturity level, and paleo-environmental conditions by considering biomarker and stable carbon isotopic analysis

Meysam Hemmati, Yaser Ahmadi, Behzad Vaferi, Ali Hosin Alibak, David A. Wood

, Available online , doi: 10.1007/s12583-024-1984-x

[Abstract](206) [PDF 1351KB](95)

Abstract:
Biomarker and stable carbon isotope analyses are presented for the Garau formation of the Cretaceous age, an important source rock in western Iran, to reveal its potential as an oil-prone source rock. The C₂₈/C₂₉sterane ratio value range (0.72 to 0.83) of bitumen samples from the formation suggests that they were likely formed during phytoplankton blooms. Sterane, hopane, and isoprenoid/n-alkane ratios indicate that the formation's organic matter predominantly consists of algae, and bacteria, accompanied by some reworked material derived from higher plants. Due to the predominance of anoxic conditions and the actions of sulfate-reducing bacteria, the bitumen present is enriched with sulfur compounds. The percentages of saturates, aromatics, and nitrogen-sulfur-oxygen (NSO) fractions in the bitumen samples classify them as naphthenic oils. Isotope analysis reveals that biodegradation and water-washing have reduced the concentrations of some volatile saturates and low molecular weight aromatics in the bitumen samples. These actions have resulted in distinctive δ¹³C values for the formation's kerogen and bitumen fractions. The formation's organic matter has been subjected to high-temperature thermal regimes and has entered the oil-generation window at the sampled localities, with vitrinite reflectance (%R_C) varying between 0.7 % and 0.75 %.

A potentially new early Ediacaran glaciation

Zhongwu Lan, Magdalena H. Huyskens, Rong Ren, Qing-Zhu Yin

, Available online , doi: 10.1007/s12583-024-1979-7

[Abstract](239) [PDF 1423KB](89)

Abstract:

Multiple episodes of Neoproterozoic glaciation, namely the Beiyixi, Altungol, Tereeken and Hankalchough glaciations, are recorded in the Kuruktag area of northeastern Tarim Craton, NW China. The Tereeken glaciation was previously correlated with the global Marinoan glaciation based on sedimentary and chemostratigraphic features recorded in the cap dolostone immediately overlying the glaciogenic diamictite, as well as less precise radiometric age constraints. In this study, we obtained chemical-abrasion isotope dilution isotope ratio mass spectrometry (CA-ID-IRMS) U-Pb age of 624.03 ± 0.1 Ma from zircons extracted from a tuff lava interbeded within the diamictite of the Tereeken Formation, which suggests an early Ediacaran age for the Tereeken glaciation. Such newly discovered early Ediacaran glaciation in the Tarim region could have induced the negative δ¹³C_carb excursions between 625-605 Ma by providing oxygen and other oxidants to invoke remineralization of a deep ocean dissolved organic carbon (DOC) reservoir.

Detrital zircon U-Pb age analysis of Late Pliocene deposits from the lower Yangtze River, South China: Implications for sedimentary provenance and evolution of the Yangtze River

Xu Lin, Chang’an Li, Jing Liu-Zeng, Jovliet Marc, Haijin Liu, Lingling Li, Chengwei Hu, Xiaokang Chen, Jixin Chen

, Available online , doi: 10.1007/s12583-023-1961-9

[Abstract](447) [PDF 5297KB](124)

Abstract:
The Yangtze River, with a length of approximately 6,300 km, holds the distinction of being the largest river in East Asia that empties into the Pacific Ocean. Its formation is intricately linked to regional tectonic activity and climate fluctuations. However, the exact timeline for the formation of the Yangtze River remains elusive. This study investigates the provenance of the late Cenozoic strata in the Wangjiang Basin, situated in the lower Yangtze River, through the application of detrital zircon U-Pb dating. A total of seven sand samples were analyzed, leading to the identification of new U-Pb detrital zircon ages (n = 577). Our study reveals that the sand materials found in the Pliocene gravel beds of the Anqing Formation originate predominantly from the Yangtze River. The findings of our study, along with the provenance tracing of boreholes in the Yangtze River Basin and the shelf sea in East China, provide compelling evidence for the continuous presence of the Yangtze River throughout the Pliocene period. The development of the Yangtze River during the Pliocene is intricately connected to both the tectonic adjustments occurring at the southeastern margin of the Tibetan Plateau and the intensification of the Asian Monsoon.

Multi-scale structural geological model and quantification of stability evaluation for a high-steep fractured rock slope

Jia Wang, Wen Zhang, Donghui Chen, Han Yin, Junqi Chen

, Available online , doi: 10.1007/s12583-023-1953-9

[Abstract](189) [PDF 20246KB](67)

Abstract:
This study aims to evaluate the stability of a high-steep fractured rock slope on the right bank of Dongcuo River, Southeast Tibetan Plateau by establishing a multi-scale structural geological model. Multi-scale discontinuity information was first identified via the unmanned aerial vehicle photogrammetry. The multi-scale structural geological model for the cross section of the slope was established by multi-scale discontinuity processing. In particular, large-scale discontinuities were directly embedded into the model, medium-scale discontinuities were realized via discrete fracture network simulation technology, and small-scale discontinuities were implicitly considered in the equivalent rock parameter calculation. A staged scheme for searching the shortest paths of the multi-scale structural geological model via Dijkstra's algorithm was established. The searched shortest path with the largest discontinuity persistence passes the most fractures and processes the lowest shear strength, which can represent the critical slip surface (CSS). Three potential CSSs were selected for the quantification of the factor of safety (FOS) using the transfer coefficient method. Modified Jennings' criteria were proposed to estimate the equivalent shear strength of the CSS composed by rock bridges and discontinuities. Finally, FOS is calculated as 3.81, implying that the studied rock slope remains stable

Investigation of oil content in lacustrine shale-oil systems: Insights from two different pyrolysis

YUPING WU, Chinglin Liu, Fujie Jiang, Tao Hu, Chenxi Zhang, Jiahao Lv, Renda Huang, Meiling Hu, Guanyun Wu, Rizwan Sarwar Awan

, Available online , doi: 10.1007/s12583-023-1814-6

[Abstract](979) [PDF 1935KB](86)

Abstract:
This research has investigated the oil content of lacustrine shale-oil systems from the Junggar Basin. Twenty-eight samples are used for different pyrolysis experiments to study the characteristics of shale oil occurrence and the difference between various evaluation methods. Additionally, the factors affecting the physical states of shale oil are discussed. Compared with the standard Rock-Eval, the two-step pyrolysis and multi-step pyrolysis can eliminate the influence of the carryover effect. Therefore, these two types of pyrolysis are used to obtain the total, free, and adsorbed oil yield of the shale. The results demonstrate that the total oil yield acquired by multi-step pyrolysis is quite similar to that obtained by two-step pyrolysis. Both of them can prevent the retained oil yield from being underestimated by more than 50%. However, the free oil yield obtained by multi-step pyrolysis is significantly higher than that obtained by two-step pyrolysis. The multi-step pyrolysis can easily exaggerate the real free oil yield in resource evaluation. Therefore, this article suggests using the two-step pyrolysis to evaluate the characteristics of petroleum in shales. Furthermore, the amount of hydrocarbons within shales is related to organic matter properties. The higher the organic matter richness, the higher the total/adsorbed oil yield within the shale before reaching the adsorption saturation. The better the kerogen type, the higher the amount of liquid hydrocarbons within shales. As the thermal evolution of shales increases, the free oil proportion and the mobility of petroleum increase. This study compared different pyrolysis methods, which provided new insight for obtaining the oil content of shales, a key parameter of shale oil resource evaluation.

Application of unmanned aerial vehicle remote sensing on dangerous rock mass identification and deformation analysis: case study of a high-steep slope in an open pit mine

Wenjie Du, Qian Sheng, Xiaodong Fu, Jian Chen, Jingyu Kang, Xin Pang, Daochun Wan, Wei Yuan

, Available online , doi: 10.1007/s12583-023-1813-7

[Abstract](445) [PDF 4237KB](120)

Abstract:
Source identification and deformation analysis of disaster bodies are the main contents of high-steep slope risk assessment, the establishment of high-precision model and the quantification of the fine geometric features of the slope are the prerequisites for the above work. In this study, based on the UAV remote sensing technology in acquiring refined model and quantitative parameters, a semi-automatic dangerous rock identification method based on multi-source data is proposed; In terms of the periodicity UAV-based deformation monitoring, the monitoring accuracy is defined according to the relative accuracy of multi-temporal point cloud. Taking a high-steep slope as research object, the UAV equipped with special sensors was used to obtain multi-source and multi-temporal data, including high-precision DOM and multi-temporal 3D point clouds. The geometric features of the outcrop were extracted and superimposed with DOM images to carry out semi-automatic identification of dangerous rock mass, realizes the closed-loop of identification and accuracy verification; changing detection of multi-temporal 3D point clouds was conducted to capture deformation of slope with centimeter accuracy. The results show that the multi-source data-based semi-automatic dangerous rock identification method can complement each other to improve the efficiency and accuracy of identification, and the UAV-based multi-temporal monitoring can reveal the near real-time deformation state of slopes.

Organic matter occurrence and its effects on pore structure and methane adsorption capacity capacity: A case study of the Niutitang black shale in Guizhou, China

Peng Xia, Fang Hao, Jinqiang Tian, Yong Fu, Chuan Guo, Zhen Yang, Yuliang Mou, Ke Wang

, Available online , doi: 10.1007/s12583-022-1688-z

[Abstract](1259) [PDF 5313KB](99)

Abstract:
The black shale samples from the Niutitang Formation in the Yangtze Block were sequentially treated using organic solvent extraction and wet chemical oxidation. The organic matter (OM) in the shales includes physically mobile OM (PmOM), chemically mobile OM (CmOM), and stable OM (StOM). The CmOM has the strongest CH4 adsorption capacity because it has the largest volume of micropores and mesopores. In contrast, the PmOM has a very negative effect on the CH4 adsorption because it is poreless. The XD shale is a siliceous shale, in which the quartz particles wrap partly OM, preventing extraction and oxidation. The SL shale is an argillaceous shale, in which most of the OM is combined with clay minerals to form organo-clay composites. In both the SL and XD shales, the OM that is extractable via organic solvents is distributed among the mineral particles and is interconnected. The conceptual model of marine black shale in different environments needs to be perfected in the future because quantitative and qualitative methods should be combined to clarify the relationship between the known OM types (e.g., pyrobitumen, solid bitumen, and solid kerogen) and the OM types identified in this study.

Spatial and temporal evolution of lithospheric mantle beneath the eastern North China Craton: Constraints from mineral chemistry of peridotite xenoliths from the Miocene Qingyuan basalts and a regional synthesis

Jian-Fang Guo, Qiang Ma, Jianping Zheng, Yuping Su

, Available online , doi: 10.1007/s12583-022-1691-4

[Abstract](220) [PDF 5165KB](71)

Abstract:
Mineralogical data are presented for the peridotite xenoliths from Miocene (~19Ma) Qingyuan basalts in the eastern North China Craton (NCC), with the aim of constraining on property of the sub-continental lithospheric mantle (SCLM) beneath the northern Tan-Lu Fault zone (TLFZ) during the Cenozoic. The Qingyuan peridotites are dominated by spinel lherzolites with moderate-Mg# olivines (89.4 to 91.2), suggesting that the regional SCLM is mainly transitional and fertile. Light rare earth element (LREE)-depleted, slightly depleted and enriched clinopyroxenes (Cpx) are identified in different peridotites. Chemical compositions of the LREE-enriched Cpx and the presence of phlogopite suggest that the Qingyuan SCLM has experienced silicate-related metasomatism. The synthesis of available mineral chemical data of the mantle xenoliths across the NCC confirms the SCLM beneath the NCC is highly heterogeneous in time and space. The Mesozoic-Cenozoic SCLM beneath the TLFZ and neighboring regions are more fertile and thinner than that beneath the region away from the fault zone. The fertile and refractory peridotite xenoliths experienced varying degrees of silicate and carbonatite metasomatism, respectively. The spatial-temporal lithospheric mantle heterogeneity in composition, age and thickness suggest that the trans-lithosphere fault zone played an important role in heterogeneous replacement of refractory cratonic lithospheric mantle.

Limitation of the Application of Heat Tracer in Investigating Groundwater and River Interactions under Dynamic Flow Conditions

Mengyan Ge, Rui Ma, Ziyong Sun

, Available online , doi: 10.1007/s12583-022-1683-4

[Abstract](171) [PDF 3970KB](29)

Abstract:
The groundwater (GW) in the floodplain riparian area frequently interacts intensely with surface water (SW). Heat as a tracer is one of the hot research fields in investigating GW-SW interactions, and analytical approaches have been proposed for the calculation of exchange flow velocity. However, few studies have considered the effects of very dynamic flow conditions and monitoring instrumentation on the calculation with field measured data. Herein, taking the middle reaches of the Heihe River as the study area, different types of monitoring wells were constructed under the riverbed and near the river, and multiple methods (Darcy’s law, heat tracing, and isotopic mixing methods) were employed to trace the exchanges between the river and groundwater. The results indicate that different methods demonstrate diverse information with obvious unevenly distributed flux along the vertical direction. And the combination of multiple methods has an important role in studying the interaction between GW and SW. Fully screened wells produce intraborehole flow and disturb the heat transport, which is relevant to flow velocity, and further affects the temperature distribution, impacting the temperature-based flow velocity calculation. Dynamic flow conditions aggravate riverbed sediment disturbances, e.g., scour and deposition, and additionally affect the interaction and monitoring data.

Geochemical Modeling of Fluid–Rock Interactions in Shallow buried Carbonate Reservoirs based on the Water Bath Instrument

Jiayi Ma, Anjiang Shen, Shuyun Xie, Min She, Huayun Tang, Emmanuel M. CARRANZA, Tianfu Zhang

, Available online , doi: 10.1007/s12583-022-1690-5

[Abstract](218) [PDF 2439KB](34)

Abstract:
Fluid–rock interaction plays a critical function in physical and chemical processes associated with the formation and evolution of oil and gas reservoir space. In the diagenetic stage of shallow burial, the dissolution of carbonate rocks by acidic fluids is conducive to the development of secondary pore space in reservoirs. In contrast, the free drift experiment based on water bath instrument can simulate the dissolution process of carbonate rocks in shallow burial environment effectively. In order to study the shallow burial dissolution mechanism of carbonate rocks in different acid solutions, 14 samples of typical carbonate rocks of Sinian, Cambrian, Ordovician, Permian and Triassic ages in the Tarim and Sichuan Basins, China were used. The dissolution experiments on carbonate rocks in sulfuric acid, acetic acid, hydrochloric acid, silicic acid and carbonic acid at shallow burial temperature (30℃≤T≤90℃) were carried out using a water bath instrument. The PHREEQC software was used to simulate the dissolution of carbonate minerals, in order to compare the results of constant temperature water bath experiment. The results show that acid solutions have significant dissolution effect on shallow burial carbonate rocks when T = 50–60℃, which corresponds to the burial depth of 1500–2000 m in the Tarim Basin and 1110–1480 m in the Sichuan Basin. However, there were obvious differences in the dissolution and reformation of carbonate rocks in different acids. In particular, sulfuric acid solution produced by thermochemical sulfate reduction can significantly promote the dissolution of carbonate rocks, especially dolomitic limestone. Moreover, the dissolution of limestone reservoirs is stronger than that of dolomite reservoirs in shallow burial. The results will provide new insights into the study of dissolution laws and influencing factors of carbonate reservoir space and the evaluation and prediction of carbonate reservoir in China.

Chronology, geochemistry and isotopic compositions of the Cretaceous Zhangjiakou diabase: Magmatic derivation and geodynamic implications

peng li, Dazhao Wang, guanzhong shi

, Available online , doi: 10.1007/s12583-022-1684-3

[Abstract](190) [PDF 6259KB](32)

Abstract:
Zircon U–Pb ages, major and trace elements and Sr–Nd–Hf isotope data of the diabase in the Zhangjiakou district were studied to investigate its derivation and tectonic implications. Zircon U–Pb ages indicate that the diabase was emplaced at ~130 Ma or younger, and captured zircons cluster at ~147 Ma, ~240 Ma, ~430 Ma and ~465 Ma. The diabase is characterized by minor variations in SiO2 (49.35–52.10 wt.%), TiO2 (1.65–1.77 wt.%), Al2O3 (17.00–18.26 wt.%), MgO (4.28–4.93 wt.%), CaO (6.69–7.90 wt.%) and Mg# (48–54). It has no significant Eu anomaly and displays enrichment in large ion lithophile elements (Rb, Ba and Sr) and depletion in high field strength elements (Nb, Ta, P and Ti). The diabase exhibits homogeneous Sr ((87Sr/86Sr)i = 0.70606–0.70701) and Nd (εNd(t) =–13.6 to –13.2) isotopic compositions. These features suggest that the parental magma was derived from partial melting of the ancient lower crust, relating to mantle upwelling that triggered by stagnant slabs or lithospheric detachment associated with the westward subduction of the Paleo-Pacific Plate. The Early Paleozoic inherited igneous zircons in the diabase suggest that the northern margin of the North China Craton (NCC) likely underwent southward subduction of the Paleo-Asian Ocean.

Characteristics of connected pores and evaluation of shale oil mobility in the Qianjiang Formation, Qianjiang Sag, Jianghan Basin,China

SUN Zhongliang, LI Zhiming, HE Chencheng, ZHU Feng, SHEN Baojian, LU Longfei

, Available online , doi: 10.1007/s12583-022-1699-9

[Abstract](426) [PDF 2527KB](40)

Abstract:
The connectivity of shale pores and the occurrence of movable oil in shales have long been a focus of research. In this paper, samples from Wells BX7 and BYY2 in the Eq34-10 cyclothem of Qianjiang Formation in the Qianjiang Depression, were analyzed. A double mercury injection method was used to distinguish between invalid and effective connected pores. The pore characteristics for occurrence of retained hydrocarbons and movable shale oil were distinguished based on comparison of pore changes in low temperature nitrogen adsorption and high pressure mercury injection experiments before and after extraction and the change in the mercury injection amounts in the pores between two separate mercury injections.. The results show that less than 50% of the total connected pores in the Eq34-10 cyclothem samples are effective. The development of effective connected pores affects the mobility of shale oil but varies with different lithofacies. The main factor limiting shale oil mobility in Well BX7 is the presence of pores with throat sizes less than 15nm. In Well BYY2, residual mercury in injection testing of lamellar dolomitic mudstone facies was mainly concentrated in pores with throats of 10~200 nm, and in bulk argillaceous dolomite facies it was mainly concentrated at 60~300nm. The throats of hydrocarbon-retaining pores can be 5nm or even smaller, but pores with movable shale oil in the well were found to have have throat sizes greater than 40nm. Excluding the influence of differences in wettability, the moveability of shale oil is mainly affected by differences in lithofacies, the degree of pore deformation caused by diagenesis, the complexity of pore structures, and the connectivity of pore throats. Dissolution and reprecipitation of halite also inhibit the mobility of shale oil.

Contrasting behavior for Li-Mg isotopes during subduction: Insights from garnet in the Yardoi schists, Tibet

Xing Li, Yilin Xiao, Olivier Nadeau, Dongyong Li, Haiyang Liu, Zhang Zeming, Zhenhui Hou

, Available online , doi: 10.1007/s12583-022-1697-y

[Abstract](277) [PDF 4022KB](76)

Abstract:
It has long been recognized that garnet has the capacity to preserve the trace element and isotopic signature of distinct metamorphic growth zones because of its high closure temperature. Combined with the large size of certain garnet porphyroblast, this allows investigating variations in metamorphic conditions such as pressure, temperature, deviatoric stress, and fluid composition, which occur during subduction-related metamorphism. Here, one garnet porphyroblast of 6 cm diameter was sampled from the Yardoi schists of Tibet, and the major-, trace-, and Li-Mg isotopic compositions of distinct growth zones were determined in situ. The δ7Li values range from +6.0 ‰ to +4.1 ‰ and follow ‘S-shape’ patterns on both sides of the garnet’s core, revealing a two-stage growth process corresponding to the fluid-assisted sequential recrystallization of chlorite and micas during prograde metamorphism. By contrast, once corrected for the overprinting by retrograde metamorphism, the δ26Mg values vary monotonously from -1.73 ‰ in the core to -1.32 ‰ in the outer rim, reflecting a single-step process interpreted to result from increasing temperature and the solid-state recrystallization of chlorite-biotite during prograde metamorphism. This different behavior of Li and Mg isotopes is interpreted to result from the fact that Li is more fluid-mobile than the major element Mg.

Characteristics and formation analysis of earth fissure in Anren area in Wei River Basin, China

Jianwei Qiao, Zhenjiang Meng, Yuyun Xia, Cong Liu, Quanzhong Lu, Feiyong Wang, Yuanqiang Zhou, Haiyuan Zhao

, Available online , doi: 10.1007/s12583-022-1653-x

[Abstract](337) [PDF 3547KB](27)

Abstract:
Since the 1950’s, 212 earth fissures have been discovered in the Wei River Basin. During a field survey in 2016, an additional 48 earth fissures were discovered in Anren area, northeast of the Wei River Basin. The characteristics and formation mechanisms of these fissures were studied through field investigations, measurements, trench excavation, and drilling. On-site investigations indicated that these earth fissures were distributed along a fault-controlled geomorphic boundary. Fissures trended at 60°–80° NE and were divided into five groups. Trenches revealed multiple secondary fissures, exposing severe soil ruptures in the shallow earth surfaces. Drilling profiles revealed that earth fissures dislocated several strata, and resembled synsedimentary faults. Seismic reflection profiles revealed buried faults beneath the earth fissures. The Anren area fissures formed in the following three stages: regional extension that initially generated multiple buried faults; seismic activity rupturing multiple strata, resulting in multiple buried fractures; and finally, erosion processes that propagated the buried fractures to the surface, forming the current earth fissures.

Geochronology and geochemistry of Permian Dashizhai Basin in Xing’an–Inner Mongolia Orogen: Implications for the evolution of the Paleo-Asian Ocean

Chi Zhang, Guosheng Wang, Zhiguang Zhou, Shen Gao, Neng Zhang, Liudong Wang, Erqiang Bo

, Available online , doi: 10.1007/s12583-022-1651-z

[Abstract](190) [PDF 21807KB](33)

Abstract:
The Xing’an–Inner Mongolia Orogen is a critical tectonic unit for constraining the evolution of the Paleo-Asian Ocean. However, the location and time for the closure of the Paleo-Asian Ocean are still debated. Here, we select a representative basin in Dashizhai in northeastern China, using U-Pb zircon geochronology and geochemistry to analyze the sedimentary facies, depositional ages, and provenance. The results show that the age of the Dashizhai Formation range from 400 to 347 Ma, the Shoushangou Formation range from 400 to 348 Ma, the Zhesi Formation range from 307 to 252 Ma, and the Linxi Formation range from 299 to 241 Ma. The Dashizhai Formation is composed of metamorphic andesite and clastic rocks. The Shoushangou Formation comprises siltstone, rhyolite, and argillaceous siltstone. The Zhesi and Linxi Formations are composed of mudstone and argillaceous siltstone. Geochemical data shows that these rocks are enriched in light rare earth elements and depleted in Eu with various La/Sc, Th/Sc, and La/Co ratios. The Permian Dashizhai Basin is from Permian volcanic and felsic igneous rocks from the Ergun, Xing’an, and Songliao blocks. The absence of the Late Carboniferous strata in the Dashizhai Basin indicates an extension setting during this period. Furthermore, we suggest the Xing’an–Inner Mongolia Orogen was an uplifting process associated with evolution the Paleo-Asian Ocean during the Late Permian.

Late Miocene elevated horizontal karst caves and landform evolution as a response to tectonic uplift along with regional integration of fluvial drainage in Southwestern China

Min Zhai, Xinggong Kong, Yuanhai Zhang, Philip Rowsell, Zhijun Zhao, Baojian Huang, Jing Zhang

, Available online , doi: 10.1007/s12583-022-1656-7

[Abstract](328) [PDF 14363KB](26)

Abstract:
In Southwestern China, the development of karst landforms and the planation surfaces is closely related to local tectonics, fluvial incision and base level change, as well as climate change. While researches on when these karst landforms and planation surfaces formed and how they evolved along drainage development are scarce. Fortunately, horizontal caves with numerous fluvial deposits in high karst mountains can be used as time markers in landform evolution. Here we select large horizontal caves to perform studies of geomorphology, sedimentology and geochronology. Field work shows that more than 25 km long horizontal cave passages are perched 1500 m higher than the local base level, but filled with several phases of fluvial sediments and breakdown slabs. The first phase of fluvial gravels and related cave drainage were dated back to 6.4 Ma using cosmogenic nuclide burial dating, and the stalagmite covering the cave collapse was dated by the U-Pb method , older than 1.56 Ma. These results show that the continuous horizontal cave drainage system and the planation surface were developed prior to the Late Miocene. The lowering process of the base level as a result of the sharp fluvial incision and water level lowering, along with the regional uplift, led to the abandonment of the horizontal cave and the elevated planation surface at the Late Miocene . After that, the phase of cave collapse , thick fluvial sand and clay sediments in the caves from the recharge of the cave deposited at around 1.6 Ma and during the Middle Pleistocene, respectively. Subsequently, speleothems widely deposited on the collapse and clay sediment during the period from 600 to 90 ka ,whereas the deposition of cave fluvial sediments terminated suddenly. The tectonic could control the denudation of surface caprock and the development of karst conduits prior to the Late Miocene, whereas the river incision acted as the main driver for the base level lowering and the destruction of the horizontal cave drainage at high altitude. In addition, the rapid incision and the retreat of Silurian gorges finally caused the formation of karst mesa in the Middle Pleistocene.

Source-to-sink relationships between the Qaidam Basin (North Tibet) and its surrounding mountain ranges: New insights from detrital zircon U–Pb ages in modern river sediments

Xu Zhang, Bowen Song, Tinglu Yang, Yafei Hou, Yibo Yang, Keke Ai, Jiaxuan Wang, Zhang Kexin

, Available online , doi: 10.1007/s12583-022-1666-5

[Abstract](330) [PDF 7269KB](52)

Abstract:
The Cenozoic source-to-sink history of the Qaidam Basin is crucial for understanding of the basin-filling architecture, mountain-building processes and even the dynamics of the Tibetan plateau growth. However, the provenance history of Cenozoic strata in the Qaidam Basin remains ambiguous, especially in the northern Qaidam Basin. This controversy highlights the importance of obtaining the spatial source-to-sink relationships between the Qaidam Basin and its surrounding mountain ranges. In this study, we investigated the detrital zircon U–Pb ages of modern fluvial systems draining the Eastern Kunlun Shan. Their detrital zircon age distributions fall into five age groups: 300-190, 530-360, 1000-560, 2000-1100 and 2650-2000 Ma. The dominant age groups are 530-360 and 300-190 Ma, which represent the successive subduction of the Proto-Tethys and Paleo-Tethys Oceans and the subsequent continental collisions, respectively. Combining these new detrital zircon U–Pb ages with available age datasets, we finally obtained complete detrital zircon age information for modern fluvial systems in the whole Qaidam Basin. The U–Pb age distributions of modern river sands reveal that the zircon age signature of basement rocks in the Eastern Kunlun Shan is significantly different from that in the South Qilian Shan but is similar to that in the Altyn Tagh Shan. Moreover, these zircon age observations were confirmed by the significant difference in the Nd isotopic signature of modern river sands, which reveals a significant difference between the Eastern Kunlun Shan and South Qilian Shan in the formation and evolution process.

Karst trough control of solute transport processes at two karst groundwater flow systems, Western Hubei, Central China

Yi'an Wang, Ruichao Zhao, Lin Ding, Shuai Xiong, Yin Li, Jianwei Bu, Wei Chen, Hong Zhou, Wei Liu

, Available online , doi: 10.1007/s12583-022-1665-6

[Abstract](405) [PDF 3313KB](69)

Abstract:
To investigate groundwater flow and solute transport characteristics of the karst trough zone in China, tracer experiments were conducted at two adjacent typical karst groundwater flow systems (Yuquandong (YQD) and Migongquan (MGQ)) in Sixi valley, western Hubei, China. High-resolution continuous monitoring was utilized to obtain breakthrough curves (BTCs), which were then analyzed using the multi-dispersion model (MDM) and the two-region nonequilibrium model (2RNE) with basic parameters calculated by CXTFIT and QTRACER2. Results showed that: (1) YQD flow system had a complex infiltration matrix with overland flow, conduit flow and fracture flow, while the MGQ flow system was dominated by conduit flow with fast flow transport velocity, but also small amount of fracture flow there; (2) they were well fitted based on the MDM (R2=0.928) and 2RNE (R2=0.947) models, indicating that they had strong adaptability in the karst trough zone; (3) conceptual models for YQD and MGQ groundwater systems were generalized. In YQD system, the solute was transported via overland flow during intense rainfall, while some infiltrated down into fissures and conduits. In MGQ system, most were directly transported to spring outlet in the fissure-conduit network.

Effect of the tectonic inversion on the Source-to-sink system evolution in a lacustrine rift basin, a case study of South Yellow Sea Basin, East China.

Xue Fan, Chao Fu, Shengli Li, Shunli Li

, Available online , doi: 10.1007/s12583-022-1664-7

[Abstract](180) [PDF 10495KB](39)

Abstract:
The complex plate collision process led the South Yellow Sea Basin (SYSB) to go through an intensity tectonic inversion during the early Cenozoic, which led to a regional unconformity surface development. As a petroliferous basin, SYSB saw intensity denudation and deposition process, making it hard to characterize their source-to-sink system(S2S), and this study provided a new sight to reveal them quantitatively. According to the seismic interpretation, it was found that two types of tectonic inversion led to the strata shortening process, which was classified according to their difference in planar movements, dip-slip faults, and strike-slip ones. As for dip-slip faults, the inversion structure was primarily formed by the dip-slip movement and many fault-related folds developed, which mainly developed in the North Depression Zone of the SYSB. The strike-slip ones, accompanying developed with some negative flower structures, are dominated in the South Depression Zone of the SYSB. Then, to reveal its source-to-sink system in the tectonic inversion basin, we speculated the sediments’ provenance area and their migration distance, referring to the zircon U-Pb data and heavy mineral assemblage. As for the North Depression Zone, it is shown that fewer distal sediments from the West Sulu Orogenic Belt are infilled, and proximal slump or fan delta are prominently developed during the tectonic inversion stage. The provenance rebuild in the South Depression Zone shows increasing sediments from the proximal area (Central Uplift Zone in SYSB and Wunansha Uplift) and the prograding delta long-axis parallel to these boundary faults during the tectonic inversion stage. Calculations were conducted on the coarse sediments content, faults displacements, catchment relief, sediments migration distance, and discussions about the impact factors to the Source-to-sink system developed in various strata shortening patterns with a statistical method. It was found that, within the dip-slip faults-dominated zone, the volume of the sediment routing system and the ratio of coarse-grained sediments merely has a relationship with the amount of sediment supply and average faults broken displacement. Compared with the strike-slip faults-dominated zone, the source-to-sink system shows a lower level of sandy sediment influx, and its coarse-grained content is mainly determined by the average faults broken displacement.

Mechanism of interaction between anchored slide-resistant piles and landslides with weak-hard interbedded bedrock：model tests and theoretical interpretation

Guihua Wang, Changdong Li, Xin He, Taijiang Chen, Jie Meng, Wenmin Yao, Yongquan Zhang, HUAWEI ZHANG

, Available online , doi: 10.1007/s12583-022-1663-8

[Abstract](383) [PDF 3551KB](22)

Abstract:
Interactions between anchored slide-resistant piles and landslides with weak-hard interbedded bedrock have not yet been systematically studied. Physical models of landslides reinforced by anchored slide-resistant piles are investigated based upon the self-developed testing system. The landslide system evolution with increasing loading force is revealed; the internal force and deformation of anchored slide-resistant piles in weak-hard interbedded bedrock are analyzed. A single anchored pile in weak-hard interbedded bedrock is analyzed theoretically, and an optimized calculation method for the axial force of the anchor cable is proposed. The results show that (1) The landslide system evolves through four stages: creeping, coordinated deformation, uncoordinated deformation, and failure. (2) The thrust sharing ratio of the pile-anchor first increases, then decreases slightly, and finally stabilizes; the maximum thrust sharing ratio is 12.22. (3) The anchoring force provided by weak-hard interbedded bedrock is between those of homogeneous hard and homogeneous weak rocks. The horizontal displacement of the pile in homogeneous hard rock is small, but more thrust is borne by the pile, and vice versa. (4) The theoretical value for a single anchored pile calculated by the optimized method is close to the measured value. These findings provide a scientific basis for landslide control projects in areas with weak-hard interbedded bedrock.

Applications of deep learning in mineral discrimination: a case study of quartz, biotite and K-feldspar from granite

Wei Lou, Dexian zhang

, Available online , doi: 10.1007/s12583-022-1672-7

[Abstract](173) [PDF 5838KB](40)

Abstract:
Mineral recognition and discrimination play a significant role in geological study. Intelligent mineral discrimination based on deep learning has the advantages of automation, low cost, less time consuming and low error rate. In this manuscript, characteristics of quartz, biotite and K-feldspar from granite thin sections under cross-polarized light were studied for mineral images intelligent classification by Inception-v3 deep learning convolutional neural network (CNN), and transfer learning method. Dynamic images from multi-angles were employed to enhance the accuracy and reproducibility in the process of mineral discrimination. Test results show that the average discrimination accuracies of quartz, biotite and K-feldspar are 100.00%, 96.88% and 90.63%. Results of this study prove the feasibility and reliability of the application of convolution neural network in mineral images classification. This study could have a significant impact in explorations of complicated mineral intelligent discrimination using deep learning methods and it will provide a new perspective for the development of more professional and practical mineral intelligent discrimination tools.

Origin of burrow-associated dolomites and its reservoir implications: A case study from the Lower-Middle Ordovician carbonates of Tarim Basin (NW China)

Chuan Guo, Daizhao Chen, Yong Fu, Xiqiang Zhou, Cunge Liu

, Available online , doi: 10.1007/s12583-022-1673-6

[Abstract](102) [PDF 11140KB](45)

Abstract:
The Yingshan Formation of the Lower-Middle Ordovician in the Tarim Basin (NW China) was mainly deposited in a shallow platform, which was intensely bioturbated with burrows filled with both dolomites and calcites. This study aims to figure out the controls on the dolomitization of burrow infills and the effects on petroleum reservoir quality based on petrographic examination, fluid inclusion microthermometry, and isotopic (C-O-Sr) geochemical analyses. The differentiation of burrow-associated carbonates (dolomites and calcites) was likely controlled by the interactions of sea-level oscillations of variable orders and depositional environments. The burrow-associated dolomites (BADs) were precipitated in a relatively restricted (i.e., lagoon) depositional environment during the lowstand of long-term sea level. In contrast, the burrow-associated calcites (BACs) were formed in a water circulation-improved lagoonal environment during the transgression of long-term sea level. Isotopic geochemical data indicate that the BADs in the Yingshan Formation were formed from slightly saline (i.e., mesosaline to penesaline) seawater, whereas the BACs were precipitated from nearly normal seawater. In addition to the anoxic condition, the presence of marine-sourced organic matter and sulfate-reducing bacteria, and a sufficient supply of dolomitizing fluids enriched in magnesium ions (Mg2+) and their Mg2+ concentration may have played a critical role in the formation of BADs. In the more permeable and disturbed burrow sediments as a result of burrowing, penetrating fluids with higher salinities and higher Mg2+ concentration relative to seawater favored dolomite precipitation. The fluids with seawater-like Mg2+ concentration, however, would lead to calcite precipitation. The progressive dolomitization of these burrowed sediments could have propagated the dolomitizing fronts and extended into ambient limestones, leading to the development of extensive dolomites. This dolomitization process can improve the petrophysical properties (porosity and permeability) and the potential as hydrocarbon reservoirs during the emplacement of hydrocarbons from underlying source rocks of the Cambrian to Lower Ordovician.

U-Pb ages and europium anomalies of detrital zircons from sediments in the West Kunlun Orogenic Belt: implications for the Proto-Tethys Ocean evolution

Yinggang Zhang, Xizhu Yao, Jin Wang, Wenqing Pan, Yongquan Chen, Baoshou Zhang, Tao Yang

, Available online , doi: 10.1007/s12583-022-1671-8

[Abstract](367) [PDF 5722KB](59)

Abstract:
The ocean crust remnants of the Proto-Tethys were preserved as the Kudi ophiolites in the West Kunlun Orogenic Belt (WKOB), and its evolutionary history was mainly constructed by research on igneous or metamorphic rocks in the WKOB. Sedimentary rocks in the WKOB received little attention in the past; however, they could provide important constraints on the evolution of the oceanic lithosphere. Here, a series of shales and greywackes found in the Kudi area of WKOB were studied to constrain their depositional ages and explore their significance in the evolution of the Proto-Tethys oceanic crust. U-Pb dating and europium anomaly (Eu/Eu*) were analyzed for detrital zircons from greywackes interlayers, while bulk rare earth elements and yttrium (REY) of the shales were measured. Detrital zircons U-Pb ages yielded a maximum depositional age of 436 Ma for the greywackes and black shales, while the REY distribution patterns of the black shales are similar to those of the Tarim Ordovician Saergan shales. Accordingly, the studied WKOB black shales were deposited in the Proto-Tethys Ocean during the Late Ordovician-Early Silurian period. The maximum depositional age at 436 Ma may represent a minimum closure time of the Proto-Tethys Ocean, which is also supported by the absence of increases in Eu/Eu* values during the Late Ordovician-Early Silurian. Besides, our Eu/Eu* values in detrital zircons indicate diminished orogenesis during the Archean to Mesoproterozoic, subduction-related accretion at the margins of the supercontinent Rodinia during the Neoproterozoic.

stochastic modeling of folded structures in scarce data scenarios using transiogram with locally varying anisotropy

yabo zhao, weihua hua, guoxiong chen, liang dong, zhipeng liu, xiuguo liu

, Available online , doi: 10.1007/s12583-022-1646-9

[Abstract](183) [PDF 3963KB](9)

Abstract:
sampling is usually scarce in geological modeling, and hence, complex and continuous geological phenomena are difficult to simulate when anisotropy changes locally. the current study aimed to present a method for modeling folded structures using transiogram with locally varying anisotropy in scarce data scenarios. based on the direction fields of locally varying anisotropy, a pathline-based algorithm was proposed to simulate the folds that are flattened and calculate the relative position of any two random points thereafter. compared to the traditional two-point spatial continuity measures (such as the variogram), the locally varying anisotropy transiogram could not only describe the high order markovian of the spatial distribution of geological bodies, but also do so with explicable physical implication. the report revealed that the locally varying anisotropy transiogram of horizontal strata can be directly obtained if the stratigraphic sequence and stratum thickness are known. in the case study, only one geological map was used in a real complex-fold area to successfully simulate the 3-d stratigraphic model.

gastropod fauna of the zuodeng permian-triassic boundary section in the nanpanjiang basin and its geometric-based morphological disparity analysis

xin sun, li tian, xincheng qiu, kaiping guan, erik tihelka, haijun song, jinnan tong, hao yang

, Available online , doi: 10.1007/s12583-022-1645-x

[Abstract](168) [PDF 4539KB](20)

Abstract:
gastropods, as one of the most common invertebrates in shallow marine environments, were heavily impacted by the permian-triassic mass extinction (ptme), with severe loss of diversity and remarkable dwarfism of body size. here, we report a new gastropod fauna from the permian‒triassic carbonates of zuodeng, guangxi province, south china. five species belonging to five genera and two indeterminate taxa are identified. the zuodeng fauna is dominated by paleozoic holdover taxa, including holopea teres, protostylus sp., and wannerispira shangganensis although most of them are found in the basal triassic microbialites. three gastropod communities have been recognized by cluster analysis. further morphological analyses show that the changing pattern of disparity, with diversity decreasing from community ⅱ to ⅲ, fits the interior-reduction model. in addition, the morphospace of community in microbialites is higher than those in non-microbialite bearing beds at zuodeng, shedding new light on the ecological role of microbialites during the permian-triassic environmental stress.

susceptibility mapping of ground collapse caused by anthropogenic activities

zhongmin mao, yuyong jiao, fei tan, xin qi, cong zeng

, Available online , doi: 10.1007/s12583-022-1644-y

[Abstract](130) [PDF 4967KB](3)

Abstract:
frequent ground collapses resulted by anthropogenic activities occur due to rapid urbanization. accurate susceptibility mapping is critical for disaster prevention and control. in this study, 1198 ground collapse cases were collected from 2017 to 2020 in shenzhen. after multicollinearity testing, eight effective factors (elevation, relief, clay proportion, average annual precipitation, distance from water, land use type, building density, and road density) were selected to construct an evaluation index system. ground collapse susceptibility was analyzed and mapped using the normalized frequency ratio (nfr), logistic regression (lr), and nfr-lr coupling models. finally, the rationality and performance of the three models were compared using the frequency ratio (fr) and receiver operating characteristic (roc) curve, respectively. all three models could effectively evaluate the ground collapse susceptibility (area under the roc curve (auc) > 0.7), though the result of nfr-lr model was more rational and had the highest performance (auc = 0.791) among the three models. shenzhen possessed ground collapses mainly in built-up areas, the greater the intensity of anthropogenic activity in a location, the higher the likelihood of a disaster. the high and very high susceptibility zones covered a total area of 546.76 km2 and involved the nanshan, luohu, and futian districts, as well as some areas of the baoan, guangming, and longgang districts.

Protoconodonts and Paraconodonts from the Machari Formation (upper Series 3 and Furongian) in the Eodungol Section, Yeongwol, Korea

Byung-su LEE

, Available online

[Abstract](357) [PDF 2509KB](37)

Abstract:
The Machari Formation ranges from the “upper Series 3” (Middle Cambrian) to Furongian (Upper Cambrian) in the Yeongwol area, Korea. It has been known to yield relatively diverse invertebrate fossils. Particularly trilobite biozones of the formation have been well defined. On the other hand, little has hitherto been studied on conodont microfossils for the formation. This paper reports a diverse and well preserved protoconodonts and paraconodonts of Series 3 from the formation in the Eodungol section, exposed along a southern mountain trail of Mt. Sambangsan, Yeongwol, Korea. Five of the thirteen samples collected for conodont contain a rich protoconodont and paraconodont assemblage and numerous shelly fossils including trilobites, brachiopods, sponge spicules, hyolithids and incertae sedis. Sample Eo5 is extremely fossiliferous (465 elements, 96.5 % of total collection), and the most abundant species was Phakelodus elongatus (236 elements, 62 % of the Eo5 collection). The preservation is relatively good, but some specimens are corroded and fragmentary. Some of protoconodonts are exfoliated. Relatively larger ones were commonly preserved as phosphatized internal molds, particularly in specimens of Furnishina bigeminata, Furnishina leei n. sp., Muellerodus pomeranensis, Nogamiconus sinensis and westergaardodids. Phakelodids were commonly preserved as clusters. Among twenty species referable to nine genera, Furnishina bigeminata, Furnishina leei n. sp., Nogamiconus sinensis, Huayuanodontus tricornis, Proscandodus obliquus, and Westergaardodina grandidens were previously undescribed species in Korea. This assemblage is named herein as the Westergaardodina matsushitai Zone, which is new biozonal name replacing the old one i.e., Gapparodus bisulcatus-Westergaardodina matsushitai-Westergaardodina moessebergensis Assemblage. The W. matsushitai Zone corresponds to the Lejopyge armata trilobite Zone, and is well correlated with the upper Series 3 conodont biozones of the Westergaardodina matsushitai-Westergaardodina grandidens Zone of South China, and the Westergaardodina matsushitai Zone of North China, respectively. The present data allow a useful correlation to China and Baltica in relation to new subdivision of the Cambrian. Furnishina leei n. sp. is newly described.

Uranium Isotope Variations (²³⁴U/²³⁸U and ²³⁸U/²³⁵U) and Behavior of U-Pb Isotope System in the Vershinnoe SandstoneType Uranium Deposit, Vitim Uranium Ore District, Russia

V. N. Golubev, I. V. Chernyshev, B. T. Kochkin, N. N. Tarasov, G. V. Ochirova, A. V. Chugaev

, Available online , doi: doi.org/10.1007/s12583-021-1436-9

[Abstract](34) [PDF 5507KB](21)

Abstract:
The U-Pb isotope system and uranium isotope composition (²³⁵U/²³⁸U and ²³⁴U/²³⁸U) were studied in a number of samples from the vertical section of the uranium ore body at the Vershinnoe sandstone-type deposit, Vitim uranium ore district, Russia. These parameters were determined to broadly vary. Deviations of the ²³⁴U/²³⁸U ratio from the equilibrium value indicate that the uranium ore was not completely conserved during the postore stage, and uranium was determined to continue mi‐grating at the deposit. Comparison of the U-Pb isotope age value and ²³⁴U/²³⁸U isotope ratio provides an insight into the migrate direction of uranium in the ore body. The broad variations (137.377–137.772) in the ²³⁸U/²³⁵U ratio over the vertical section of the ore body can be explained by the different settings of the samples relative to the ore deposition front and changes in the redox conditions when this front shifted. The fact that the δ²³⁸U and K_234/238 values are correlated indicates that the transfer of the ²³⁴U iso‐tope into the aqueous phase may have been coupled with isotope fractionation in the ²³⁸U-²³⁵U system during the postformation uranium migration within the orebody.

Association of Sandstone-Type Uranium Mineralization in the Northern China with Tectonic Movements and Hydrocarbons

Yin Chen, Peisen Miao, Jianguo Li, Ruoshi Jin, Hualei Zhao, Lulu Chen, CongWang, Haoyu Yu, Xiaoru Zhang

, Available online , doi: doi.org/10.1007/s12583-021-1493-0

[Abstract](77) [PDF 50719KB](31)

Abstract:
In the continental basins of Northern China (NC), a series of energy resources commonly co-exist in the same basin. As the three typical superimposed basins of different genesis in the NC, the Junggar, Ordos, and Songliao basins were chosen as the research objects. The favorable uraniumbearing structures are generally shown as a basin-margin slope or transition belt of uplifts with the de‐velopment of faults, which are conducive to a fluid circulation system. The Hercynian, Indosinian, and Yanshanian movements resulted in the development of uranium-rich intrusions which acted as the sig‐nificant uranium sources. The main hydrocarbon source rocks are developed in the Carboniferous, Permian, Jurassic and Cretaceous. The mature stage of source rocks is concentrated in the Jurassic–Cretaceous, followed by the multi-stage expulsion events. Influenced by the India-Eurasian collision and the subduction of the Pacific Plate, the tectonic transformation in the Late Yanshanian and Himala‐yan periods significantly influenced the sandstone-type uranium mineralization. The hydrocarbon reser‐voirs are spatially consistent with sandstone-type uranium deposits, while the hydrocarbon expulsionevents occur in sequence with sandstone-type uranium mineralization. In the periphery of the faults or the uplifts, both fluids met and formed uranium concentration. The regional tectonic movements moti‐vate the migration of hydrocarbon fluids and uranium mineralization, especially the Himalayan move‐ment.

An investigation of dislocation in olivine phenocrysts from the Hawaiian basalts

Zhuo-Yue Li, Da-Peng Wen, Yong-Feng Wang, Xiang-Wen Liu

, Available online , doi: 10.1007/s12583-020-1030-6

[Abstract](2089) [PDF 7048KB](159)

Abstract:
Intracrystalline distortions (like undulose extinction, dislocations, and subgrain boundaries) in olivine from naturally-deformed peridotites is generally taken as a sign of dislocation creep. However, similar features in olivine phenocrysts that were found in basaltic magmas are still not well understood. In particular, whether subgrain boundaries in olivine phenocrysts arise from plastic deformation or grain growth is still debated (In the latter case, they are essentially grain boundaries but not subgrain boundaries. Therefore, we used hereinafter subgrain-boundary-like structures instead of subgrain boundaries to name this kind of intracrystalline distortion). Here we carried out a detailed study on dislocations and subgrain-boundary-like (SG-like) structures in olivine phenocrysts from two Hawaiian basaltic lavas by means of petrographic microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). Abundant and complex dislocation substructures (free dislocations, dislocation walls, and dislocation tangles) were observed in the decorated olivine grains, similar to those in olivine from peridotite xenoliths entrained by the Hawaiian basalts. The measured average dislocation density is 2.9 ± 1.3 × 1011 m-2, and is three to five orders of magnitude higher than that in laboratory-synthesized, undeformed olivine. TEM observations on samples cut across the SG-like structures by FIB (focused ion beam) demonstrated that this kind of structures is made of an array of dislocations. These observations clearly indicate that these structures are real subgrain boundaries rather than grain boundaries. These facts suggested that the observed high dislocation densities and subgrain boundaries were not resulted from crystal crystallization/growth, but were formed by plastic deformation. These deformation features do not prove that the olivine phenocrysts (and implicitly mantle xenoliths) were deformed after their capture by the basaltic magmas, but can be ascribed to a former deformation event in a dunitic cumulate, which was formed by magmatic fractionation, then plastically deformed, and finally disaggregated and captured by the basaltic magma that brought them to the surface.

Central Asia––A Global Model for the Formation of Epigenetic Deposits in a Platform Sedimentary Cover

Igor Pechenkin, Vladislav Petrov

, Available online , doi: doi.org/10.1007/s12583-021-1581-1

[Abstract](11) [PDF 8469KB](7)

Abstract:
Metallogenic specialization of sedimentary cover in Central Asia is determined by its tec‐tonic setting that governs the hydrodynamic regime (exfiltrational or infiltrational) and as a consequence, the hydrogeochemical zonality (type of water and its gaseous and microcomponent composition). Hydro‐dynamic conditions (distribution of recharge and discharge areas) determine the direction of stratal water flow and location of mineralization resulted from the change in geochemical, thermodynamic, litholog‐ical, structural and other conditions. The exfiltrational regime suggests a dependence of the epigenetic mineralization upon the distribution and degree of preservation of hydrocarbon occurrences. Often, hy‐drocarbon matter serves as a reducing barrier and ore-concentrating factor during the formation of polymineral concentrations related to stratal oxidation zone. The supergene epigenetic ore-forming pro‐cesses are induced by the interaction between the Earth’s sedimentary cover and hydrosphere. Sedimen‐tary rocks themselves commonly serve as a source of ore materials. The ore deposition zones on geochemi‐cal barriers and ore material source are often located significantly apart from each other. The trend of these processes is determined by the position of ore-bearing depressions in large tectonic blocks.

Theoretical System of Sandstone-Type Uranium Deposits in Northern China

Ruoshi Jin, Huajian Liu, Xiaoguang Li

, Available online , doi: doi.org/10.1007/s12583-021-1449-4

[Abstract](56) [PDF 19090KB](22)

Abstract:
Many theoretical results on sandstone-type uranium mineralization in northern China obtained by the uranium research team of the Tianjin Center of Geological Survey in recent years are presented. From the source sink system of uranium-producing basins, sedimentary environment of uranium-bearing rock series, ore-forming fluid information, evolution of tectonic events, basin forma‐tion and development, we redefine and classify uranium orebodies, redox zoning, and ore-controlling structural styles. We then systematically propose a theoretical system of sandstone-type uranium depos‐its in northern China. We conclude that sandstone-type uranium deposits in northern China are main‐ly found in sedimentary environments such as rivers, deltas, and alluvial fans in the Mesozoic and Cenozoic lowstand systems tract and in gray sandstone layers in the vertical redox zoning. The orebodies are controlled by the tectonic slope belt, which is in the shape of a strip on the plane, and spreads in a layer or plate on the section. Vertical (ups and downs) tectonic movement triggers large-scale phreatic flow in the basin, which is the real driving force for controlling the ore-forming fluid. The theoretical system of sandstone-type uranium deposits in northern China should be based on global tectonic move‐ment and environmental changes and take into account factors such as basins as a unit to study miner‐alization background, ore concentration areas as objects to study mineralization, and the correlation between regional tectonic movement and metallogenic process as a breakthrough point to study tecton‐ic events and metallogenic events. It should also be based on different basin types to establish metallo‐genic models. The innovative research results and ideas are summarized with the aim of promoting the continuous improvement of sandstone-type uranium mineralization theory in northern China.

U-Blacks Mineralization in Sandstone Uranium Deposits

Olga A. Doynikova

, Available online , doi: doi.org/10.1007/s12583-021-1451-x

[Abstract](20) [PDF 18000KB](14)

Abstract:
Ores of infiltration sandstone-hosted uranium deposits in the sedimentary cover are ubiquitous composed of dispersed soot powder mineralization of black, brownish-black colour. Longterm studies of such loose U-ores by analytical transmission electron microscopy (ATEM) proved their polymineral nature. Uranium blacks are composed by at least three different U-mineral forms: oxide (uraninite), silicate (coffinite) and phosphate (ningyoite) which are present in various proportions of ore compositions. Such high dispersed friable uranium formations are difficult to diagnose by tradition‐al mineralogical methods (optical, XRD, IR and X-ray spectroscopy, etc.) which analyze total sample composition (phases mixture); their results characterize the dominant sample phase, omitting both sharply subordinate and X-ray amorphous phases. All research results are based on ATEM methods (SAED+EDS), which are optimal for crystallochemical diagnostics in the mineralogical study of such uranium ores. The article presents the diagnostic characteristics under electron microscope (EM) of uranous minerals from different sandstone deposits with their origin being discussed.

Classification of Sandstone-Related Uranium Deposits

Michel Cuney, Julien Mercadier, Christophe Bonnetti

, Available online , doi: doi.org/10.1007/s12583-021-1532-x

[Abstract](111) [PDF 1583KB](28)

Abstract:
Sandstone type deposits are the most common type of uranium deposits in the world. A large variety of sub-types have been defined, based either on the morphology of the deposits (e.g., tabu‐lar, roll front, etc), or on the sedimentological setting (e.g., paleovalley, paleochannel, unconformity), or on tectonic or lithologic controls (e.g., tectonolithologic, mafic dykes/sills), or still on a variety of others characteristics (phreatic oxidation type, interlayer permeable type, multi-element stratabound infiltra‐tional, solution front limb deposit, humate type, etc.), reflecting the diversity of the characteristics of these deposits, but making it difficult to have a clear overview of these deposits. Moreover, uranium de‐posits occurring in the same sedimentological setting (e.g., paleochannel), presenting similar morpholo‐gies (e.g., tabular), may result from different genetic mechanisms and thus can be misleading for explora‐tion strategies. The aim of the present paper is to propose a new view on sandstone-related uranium de-posits combining both genetic and descriptive criteria. The dual view is indeed of primordial importance because all the critical characteristics of each deposit type, not limited to the morphology/geometry of the ore bodies and their relationships with depositional environments of the sandstone, have to be taken into account to propose a comprehensive classification of uranium deposits. In this respect, several key ore-forming processes, like the physical-chemical characteristics of the mineralizing fluid, have to be used to integrate genetic aspects in the classification. Although a succession of concentration steps, potentially temporally-disconnected, are involved in the genesis of some uranium mineralization, the classification here proposed will focus on the main mechanisms responsible for the formation and/or the location of ore deposits. The objective of this paper is also to propose a robust and widely usable ter‐minology to define and categorize sandstone uranium deposits, considering the diversity of their origin and morphologies, and will be primarily based on the temperature of the mineralizing fluid considered as having played the critical role in the transportation of the uranium, starting from synsedimentary ura‐nium deposits to those related to higher temperature fluids.

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