Geoscience

Progress on Metallogenic Research of Granite-related Uranium Deposits from Luzong Ore District in the Middle and Lower Reaches of Yangtze River Metallogenic Belt

ZHANG Shu, ZHANG Zanzan, HU Zhaoqi, SHI Lisheng, ZHOU Taofa, WU Ming'an, DU Jianguo

2023, 37(06): 1435-1448. DOI: 10.19657/j.geoscience.1000-8527.2023.083

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The Lujiang-Zongyang ore district is one of the most important ore cluster regiones in the Middle and Lower Reaches of the Yangtze River Metallogenic Belt, and is also an important uranium prospecting area in the South China Uranium Province.Systematic uranium metallogenic study would benefit the understanding of the regional metallogenic theory and uranium prospecting.In this paper, we provide a review of the geological features, uranium-bearing intrusions, magmatic and metallogenic ages, ore-forming fluids, and uranium sources of the typical uranium deposits in the Lujiang-Zongyang ore district.The uranium deposits along the NE-trending A-type granite belt are controlled by intrusive contact, faults, and interlayer structures.The uranium deposits were formed at 114-108 Ma, whereas the ore-bearing granites are A1-type and were formed at 127-123 Ma with 115-110 Ma alkali feldspar granitic stocks.The ore-forming materials were derived from the ore-bearing intrusions and wall-rocks.The ore-forming fluids were the mixture of magmatic water and meteoric water.The uranium was likely originated from the leaching of the ore-bearing intrusions during the fluid circulation, and deposited by changes in the physicochemical condition.The uranium mineralization in the Luzong basin was controlled by concealed syenite and was formed at 131-129 Ma.The ore-bearing intrusions, which provide the ore-material sources, are of shoshonitic and were formed at 131 Ma.The ore-forming fluids were mainly of magmatic water.The uranium was probably fractionated from the F-B-rich melt into the magmatic fluids, and uraniferous veins were formed as the pressure and/or temperature dropped.We suggest that the granite uranium fertility indicator, high-precision dating of uranium deposits, and the genetic link between mantle-derived material and uranium mineralization are important research topics in future.

Characteristics of Multiphase Mineralization of Jinzhuping Tungsten Deposit in Southern Jiangxi Province and Its Geological Significance

YANG Junfeng, ZHANG Juan, LIU Xinxing, QIU Jiawei, WANG Meng, CHENG Jiawei, LU Kexuan, WANG Yingxue

2023, 37(06): 1449-1466. DOI: 10.19657/j.geoscience.1000-8527.2023.068

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The Jinzhuping quartz vein-type tungsten deposit is located in the tungsten-polymetallic metallogenic belt in the eastern Nanling region, southern Jiangxi Province.The Yanshanian concealed granite is associated with the Tungsten mineralization, and the lithology is medium-coarse-grained (or porphyritic) biotite monzogranite.The early orebody was strongly affected by late hydrothermal metasomatism, showing multi-generational characteristics.At present, there is still a lack of precise chronology on the time of buried pluton and multi-stage mineralization.In this paper, zircon and wolframite LA-ICP-MS U-Pb dating methods are used to date the porphyrotic biotite monzolitic granite and three generations of wolframites in the deposit.Our data reveal the multistage metallogenic evolution, and we further discuss the mineralization process.The results show that porphyritic biotite monzogranite was formed at (155.2±0.7) Ma, whilst the three generationgs of wolframites were formed at (164.9±2.4) Ma, (157.4±1.0) Ma and (144.8±1.8) Ma.We considered that the concealed rock of Jinzhuping tungsten deposit was emplaced in 159-155 Ma, and the three stages of hydrothermal tungsten mineralization were formed in 164.9-144.8 Ma, which were the products of large-scale magmatism and mineralization in the Yanshanian Nanling tungsten-tin polymetallic metallogenic belt.The first two generations of tungsten mineralization age and granite emplacement age are within error, and is between the previously reported Middle to Late Jurassic for the Nanling metallogenic peak.Meanwhile, the tungsten mineralization age of the third generation is about 10 Ma later than the granite formation, which may represent the newfound Early Cretaceous tungsten mineralization after the Middle and Late Jurassic mineralization.

Geochronological and Geochemical Characteristics of the Tianchitang Granodiorite in Southwestern Fujian Province: Indications for the Regional Metallogeny

ZHOU Yan, FAN Feipeng, KANG Congxuan, ZHAO Xilin, XIAO Fan, XU Mincheng, SHEN Mangting, ZHU Yiping

2023, 37(06): 1467-1481. DOI: 10.19657/j.geoscience.1000-8527.2023.001

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Granodiorite,emplaced at the transition of Early to Late Cretaceous,is the most important Cu-polymetallic metallogenic intrusion in southwestern Fujian province.The Tianchitang granodiorite,located in the transition zone between the Cretaceous Zijinshan volcanic basin and the Late Paleozoic SW Fujian depression,presents a Cu-Fe skarn affinity at the outer contact zone.LA-ICP-MS magmatic zircon U-Pb dating of the granodiorite has been conducted to understand the regional magmatic mineralization,yielding weighted average ²⁰⁶Pb /²³⁸U ages of (100.7±1.0) Ma and (99.6±0.7) Ma. The result indicate that the granodiorite was emplaced early Late Cretaceous.Petrogeochemistry shows the intrusion is metaluminous-peraluminous and high-K calc-alkaline.The rocks are enriched in LILEs(Rb,Th,Zr and Hf) and depleted in HFSEs(Nb,Ta,Sr,Ti and P) with a weak negative Eu anomaly.The comparison with ore-forming intrusions in the Zijinshan orefield indicates that all of these intrusions were simultaneously formed in an extensional tectonic setting,and were the products of mixing of the granitul magma by partial melting of crustal material and mantle-derived mafic magma modified/influenced by subduction components. The ca.100 Ma granodiorite could resultsin different forms of mineralization in various locations.Therefore,it is a critical factor for the mineralization and prospecting of Cu-polymetallic deposits in southwestern Fujian province.

Geological and Geochemical Characteristics of Ore-forming Granite Porphyry and Its Metallogenic Significance in the Zhalageamu Copper Deposit, Inner Mongolia

SONG Yanbo, WANG Jianping, SHEN Cunli, CHE Dong, YANG Wenhua, GUO Haijiao

2023, 37(06): 1482-1494. DOI: 10.19657/j.geoscience.1000-8527.2023.016

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The Zhalageamu copper deposit is located in the northeastern margin of the ancient Xilinhot Block, and is a recently discovered medium-sized hydrothermal copper deposit in the Zn-Pb-Ag metallogenic belt (western slope of the south-central Greater Khingan Range) in Inner Mongolia.Studies on its magmatic and metallogenic mechanism provides the theoretical basis for copper exploration and broadens the exploration direction.The granite porphyry is closely space-time associated with Cu mineralization of the Zhalageamu copper deposit.To clarify the formation age and source characteristics of the granite porphyry from Zhalageamu, and to address the magmatic-metallogenic relationship, the granite porphyry was collected for petrography and geochemical analysis, zircon U-Pb dating and Sr-Nd isotope analysis.The result shows that the granite porphyry from Zhalageamu is characterized by high SiO₂ and Al₂O₃, low MgO, and enrichments in Rb, K, La, and Th and depletions in Ta, Nb, Ti, and P.All of the samples are characterized by the enrichment of LREEs relative to HREEs, and weak negative Eu anomaly.This indicates that the granite porphyry belongs to high-K calc-alkaline I-type granite.The granite porphyry has ε_Nd(t)=2.1 to 3.3 and young Nd model age of 980-740 Ma, indicating that the primary magma of the granite porphyry is derved from the mixture of crust and mantle materials.The magmatic zircon age of the granite porphyry is 254.51± 2.13 Ma, indicating that the granite porphyry and relevant Cu mineralization generated in the Late Permian.A comprehensive analysis supports that the Zhalageamu copper deposit was formed in a Late Permian volcanic arc setting, which may be closely related to the subduction of the Hegenshan oceanic Plate.

Trace Elements Composition of Pyrites in the Cangshang Gold Deposit,Jiaodong: Implications for Source of Ore-forming Fluid and Material

RAN Xiaoyu, MA Yao, LIANG Yayun, LIU Xuefei

2023, 37(06): 1495-1508. DOI: 10.19657/j.geoscience.1000-8527.2023.070

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The Jiaodong gold province in North China Craton is one of the largest goldfields in China,with proven gold reserves over 5,000 tons.As an important gold deposit type in this region,disseminated ore has been widely studied for a long time,but the properties of ore-forming fluids and the sources of ore-forming materials are still controversial.Based on the LA-ICP-MS pyrite analysis on the typical disseminated gold ore (from the Cangshang gold deposit)in northwestern Jiaodong,we discussed the ore-forming fluid properties and material sources of the deposit,which provides new constraints for further understanding of the ore-forming process.The results show that the pyrite Se content of the Cangshang gold deposit is relatively low (mean 1.601×10^-6),indicating that the deposit may be mainly formed by sedimentary metamorphism.The Au/As ratio indicates that Au occurs in the form of lattice gold (Au⁺) in pyrite during the mineralization stages Ⅱ and Ⅲ.Combined with the published results on the Jiaodong ore-fluid properties,the relatively uniform Co/Ni ratios and the rise of the major pyrite Ag content at Cangshang indicate that the ore-forming fluid is mainly magmatic,with certain input of metamorphic water and meteoric water.The low Te content indicates that the ore-forming material was less likely mantle-derived.However,the low Co and Ni contents are significantly different from the magmatic pyrite characteristics,suggesting that the ore-forming material may be mixed with minor mantle components.Combined with the tectono-magmatic events of the Jiaodong metallogenic period (about 120 Ma),it is suggested that the gold and relevant ore-forming materials may have sourced from the Precambrian metamorphic basement remobilized by Mesozoic activation and mixed with minor mantle components.

Delicate Timescale of the Machangqing Porphyry Copper-Molybdenum Deposit in Sanjiang Tethyan Domain, SW China: Constraints from the Diffusion Chronology of Ti and Al in Quartz

ZHANG Liang, CHEN Qi, GAO Tian, LI Wen, QIAN Jinlong, LIU Lijun, WANG Changming

2023, 37(06): 1509-1523. DOI: 10.19657/j.geoscience.1000-8527.2023.033

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In recent years, studies on the porphyry metallogenic timescale have become more refined and diversified.By using high-precision isotope dating, element diffusion chronology and thermodynamic numerical simulation, the porphyry metallogenic timescale are precisely defined to be between tens to hundreds of thousands of years.Quartz is a chemically stable mineral in various mineralization stages, which can be utilized as an ideal object to explore episodic hydrothermal processes.Taking the Machangqing porphyry Cu-Mo deposit in the Sanjiang Tethyan Domain as the case study, and basing on the fine arrangement of the vein relationship and mineral assemblage at each stage, we used the diffusion chronology method of Ti and Al in quartz to constrain the timescale, and discussed the practical application of diffusion chronology.The Machangqing deposit contains multi-stage hydrothermal veins, which can be divided into multiple hydrothermal stages based on their crosscutting relationship and mineral composition.For the quartz in the early-ore A2 and main-ore B3 veins, our finding shows that the early-ore quartz samples have higher correlation between the CL intensity and Ti element, and its timescale defined by the Ti diffusion is 10.5-57.5 ka; for the main ore stage, the quartz CL intensity has a higher correlation with the Al element, and its timescale defined by the Al diffusion is 522.3 ka.Overall, we consider that using element diffusion chronology to constrain the porphyry metallogenic timescale may be affected by the temperature-pressure conditions, simulation location, analytical precision and accuracy.Therefore, it is necessary to construct a reasonable diffusion model based on the metallogenic conditions and mineral growth characteristics.

Genesis of Yangshan Fluorite Deposit in Western Henan Province: Fluorite REE Composition and Fluid Inclusion Thermomechanical Constraints

WANG Qibo, ZHANG Shouting, TANG Li, LI Junjun, SHENG Yuanming

2023, 37(06): 1524-1537. DOI: 10.19657/j.geoscience.1000-8527.2023.022

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The Yangshan fluorite deposit is located in Luanchuan County,Western Henan Province.The orebody is developed in the bottom of the Heyu granite,and is mainly controlled by NW- and NE-trending faults.Based on the study of rare earth elements and fluid inclusions of fluorite,the source of ore-forming materials,the ore-fluid properties and the ore genesis at Yangshan are discussed.The ΣREE content of stage Ⅱ fluorite ranges from 22.61×10^-6 to 287.94×10^-6,LREE/HREE is of 0.64 to 5.24,and there are negative Eu anomalies(δEu=0.50-0.92)and Ce anomalies(δCe=0.88-1.06).With depth increases,ΣREE decreases,whereas LREE/HREE and La_N/Yb_N increase,and δEu and δCe do not change significantly.This indicates that the overall metallogenic time sequence is from deep to shallow,and the vertical oxygen fugacity is relatively stable.From the purple fluorite to green fluorite,ΣREE increases,LREE/HREE and La_N/Yb_N decrease,and δEu and δCe increase,indicating that recrystallization evolves from purple fluorite to green fluorite.The fluid inclusions of fluorite are mainly gas-liquid two phases.The homogenization temperature and salinity of these inclusions are concentrated in the range of 80-155 ℃ and 0.3%-6.3%(NaCl_eqv.).Comprehensive analysis shows that the ore-forming fluid is mainly mixed with magmatic water and meteoric water,belonging to a low-temperature,low-salinity and low-density NaCl-H₂O system.Thus,Yangshan deposit is a low-temperature and low-salinity hydrothermal deposit.Comprehensive analysis of REEs and fluid inclusion characteristics of fluorite shows that the fluorite precipitation may have been controlled by water-rock reaction.

Surface Indicators for Deep Mineralization in the Lutangba-Axizhai Area of Gejiu, Yunnan Province: Implications from Tectonic Alteration and Primary Geochemical Halos

CHANG Huacheng, JIAO Qianqian, JIANG Xiaojun, FAN Zhuguo, LU Lei, RUAN Banlang, DENG Mei

2023, 37(06): 1538-1552. DOI: 10.19657/j.geoscience.1000-8527.2023.057

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Interlayer oxidized tin ore is a significant mineralization type in the Gaosong orefield at Gejiu. Enhancing the study and exploration for this type of tin mineralization is important to relieve resource crisis and increase the reserve for exhausting mines. We study the surface tectonic alteration and primary geochemical halo in the Lutangba-Axizhai area which shows beneficial mineralization conditions for interlayer oxidized deposits, to provide a new basis for their exploration. Field geological survey exhabits that the surface mineralization/alteration is mainly composed of iron alteration, argillization and calcite veins. It is commonly controlled by faults, especially at the intersection of NE- and EW-trending ones. The integrated analysis of 13 key elements in the altered rocks and wallrocks suggests that Cd, As, Sb, Pb and Zn are potential indicators for Sn orebody. The integrated anomaly distribution of primary geochemical halos in combination with the characteristics of structural alteration zones delineate four metallogenic target zones (Ⅰ to Ⅳ). Comparation and analysis on the front-, near- and rear-halo element combination characteristics of primary geochemical halos in each target area shows that target zone Ⅰ and Ⅱ seem to have deep interlayer oxidized tin ore prospecting potential; target zone Ⅲ with the oxidized ore is probably eroded on the surface, and have deep sulfide ore potential; target zone Ⅳ likely has small amount of uneroded remnant orebodies at depth.

Soil Geochemical Characteristics in the Naqu Area,Chongzuo City, Guangxi,and Their Mineral Prospecting Applications

LUO Haiyi, LUO Xianrong, LIU Panfeng, MA Mingliang, LU Xiansheng, JIANG Xiaoming, BAO Guangui, JIANG Yuxiong

2023, 37(06): 1553-1566. DOI: 10.19657/j.geoscience.1000-8527.2023.048

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The Naqu area has significant potential for uranium mineralization,and the molybdenum ore found in association with uranium has considerable value for comprehensive utilization.However,there has been a lack of systematic exploration work on the molybdenum occurrence in this area,hampering the regional molybdenum ore prospecting.To facilitate regional molybdenum ore prospecting,we conducted a 1:10,000 soil geochemical survey.In the survey,we systematic collected 3,295 soil samples,which were analyzed for 10 elements,including Au,Ag,As,Bi,Hg,W,Mo,Cu,V,and Ti.Multi-variant analysis indicates that Mo is a significant ore-forming element in the study area.The original data were conducted to R-type cluster analysis and R-type factor analysis using the SPSS 22 statistical software.The results yield five ore-forming element assemblages: Ag-Cu-V,Bi-Ti-W,As-Mo,Au,and Hg.The contrast anomaly method was utilized to determine the anomalous lower limit of each individual element and their assemblage.Subsequently,the contrast data of each ore-forming element assemblage were processed with the Geochem Studio 3.5 software,which created an anomaly map.Basing on the geological conditions,we proposed three potential prospecting targets,which were then delineated for further investigation.Engineering verification was conducted on the No.1 target through trenching and drilling,revealing the presence of an industrial-grade molybdenum deposit with a Mo grade of 0.11%-0.15%(average 0.112%).Verification of trench engineering was performed in the No.2 target,and analysis of sampled trenches indicates the presence of mineralized molybdenum grade.These findings point to a substantial molybdenum mineralization potential in the Naqu region.

Soil Geochemical Characteristics and Ore Prospecting Prediction in Gaojianzi Area, Northern Hebei Province

LIANG Ming, GAO Wen, LUO Xianrong, WANG Xiaodong, LIU Xiujuan, CHEN Hao, LIU Panfeng, ZHU Feng, LI Wei

2023, 37(06): 1567-1579. DOI: 10.19657/j.geoscience.1000-8527.2023.051

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The Gaojianzi area is located in the Inner Mongolia-Great Khingan fold system within the Qipanshan middle depressional tectonic units, and is an important metallogenic area in northern Hebei Province.Quaternary sediments in the area are relatively thick, and previous exploration work is rare.To extract mineralization information and apply it to the optimization and delineation of prospecting targets, we conducted a 1:10,000 soil geochemical survey in the area, and statistical analysis on the composition of nine representative ore-related elements, i.e., Au, Ag, Bi, Cu, Pb, Zn, Sb, Mo, and Mn.Our results show that Au, Ag, and Mo are favorable for local mineralization.The R-type cluster analysis was applied to classify the nine elements, and four element assemblages, i.e., Cu-Zn-Mn, Au-Pb-Bi, Sb-Mo and Ag, were classified.The cumulative frequency method is used to calculate the lower limit of single element anomaly and map the single element anomaly.The normalized areal productivity is used to evaluate the characteristics of single element anomaly parameters, and four anomaly targets and two key anomaly verification areas are delineated.In the anomaly target, the soil geochemical profile is used to verify the anomaly and delineate two favorable mineralization locations.Four gold and silver orebodies were found through the verification of trenching engineering.We suggest that useful prospecting information can be extracted from the study area with soil geochemical survey.

Petrogenesis and Tectonic Implications of Granite Porphyry in the Beidashan Area,Alxa Block: Constraints from Geochemistry, Zircon U-Pb Geochronology and Hf Isotopes

SU Hui, ZENG Renyu, GAN Debin, YAN Jie

2023, 37(06): 1580-1596. DOI: 10.19657/j.geoscience.1000-8527.2023.063

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The Beidashan Complex is located in the Beidashan area of the Alxa block,and represents an Early Precambrian metamorphic basement.These magmatic-metamorphic events are of great significance for studying the tectonic evolution and tectonic affinity of the Early Precambrian Alxa block.Here,we studied the petrography,geochemistry,zircon geochronology and Hf isotopes of the Cijingzi granite porphyry in the Beidashan area.The geochemical data shows that Cijingzi granite porphyry is characterized by high SiO₂(73.85%-75.41%),Al₂O₃(13.40%-14.19%) and K₂O(3.83%-4.80%),and low Na₂O(2.10%-3.31%) and $\mathrm{Fe}_{2} \mathrm{O}_{3}{ }^{\mathrm{T}}$(0.93%-1.33%).The rocks have obvious negative Eu anomalies(δEu=0.15-0.29),with obvious enrichment of light rare earth elements(LREE)and depletion in heavy rare earth elements(HREE)in the chondrite-normalized REE patterns.It is also depleted in Nb, Ta,Ti and other high field strength elements(HFSEs)in the primitive mantle-normalized trace element patterns,similar to highly fractional I-type granite.LA-ICP-MS zircon U-Pb dating of the Cijingzi granite porphyry yielded an emplacement age of 2,035.6±8.4 Ma.The Cijingzi granite porphyry has ε_Hf(t)=0.48-7.04 and Hf model age=2,627-2,222 Ma,indicating that the characteristics of the mixing of crust-derived magmas with mantle-derived ones.Combined with the previous studies,the magmatic event at Ca.2.0 Ga in the Alxa block exhibits the bimodal volcanic assemblage,and the felsic rocks are mostly of A-type,which were formed in an extensional environment.Zircon ages and Hf isotope compositions shows that the Alxa block and the Khondalite belt of the North China Craton have clear affinity in the Paleoproterozoic.

Genesis and Tectonic Significance of Early Jurassic Cuiluan A-type Granite in the Lesser Hinggan Mountains

YANG Yuanjiang, DENG Changzhou, LI Chenglu, YANG Wenpeng, FU Anzong, ZHENG Bo, YUAN Maowen, ZHANG Lidong

2023, 37(06): 1597-1608. DOI: 10.19657/j.geoscience.1000-8527.2023.050

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The Cuiluan area (Yichun) in the Lesser Hinggan Mountains is located at a critical location for land-sea transition, and is also affected by both the Paleo-Asian Ocean and Pacific tectonic domains.Hence, it has become an important part of the study of regional tectonic evolution.There are different viewpoints on the tectonic setting and geodynamic mechanism for the regional Mesozoic granite emplacement.This constrains the reconstruction of regional tectonic evolution, and hinder the advance of regional prospecting.Basing on the study in geochronology, lithogeochemistry and Hf isotope of the Early Jurassic Cuiluan alkali feldspar granite, we discussed the granitic genesis and its geological significance, which provides a new chronological constraint for better understanding the Early Jurassic regional tectonic evolution.Zircon U-Pb dating results show that the intrusive age of alkali feldspar granite is (189.1± 1.6) Ma (Early Jurassic).The granitic rock is rich in Si, K, and Na and poor in Ca and Mg.It is enriched in Th, Zr, Hf, Ce and Y, but depleted in Ba, Sr, Eu, Nb, Ta and Ti.The zircon saturation temperature is high (804-810 ℃).The total REE content is high (ΣREE=192.60×10^-6-232.80×10^-6).These characteristics show that the granite is A-type, with crustal source affinity. The zircon ε_Hf(t) ranges from +1.46 to + 2.27, with the corresponding crustal model age $T_{\mathrm{DM}}{ }^{\mathrm{C}}$=1133-1088 Ma, indicating that the magma source consists mainly of the juvenile Mesoproterozoic crustal material.On the basis of previous works, we consider that the Early Jurassic magmatic activity at Yichun was closely related to the Paleo-Pacific subduction and attendant tectonic extension of the supra-subduction plate.

Geochronology,Geochemistry and Tectonic Implications of Early Neoproterozoic Tuyaodong Intrusive Rocks in the East Kunlun Orogen in Xinjiang

XI Zhen, MA Decheng, LI Huan, GAO Guangming, XIANG Xianan

2023, 37(06): 1609-1623. DOI: 10.19657/j.geoscience.1000-8527.2023.010

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The western section of the East Kunlun Orogen(EKO) developed Proterozoic granites,and the magmatic timeframe and tectonic setting remain controversial,which restricts our understandings of the Proterozoic EKO tectonic evolution.Here,we investigate the regional tectonic evolution via LA-ICP-MS zircon U-Pb dating and whole-rock elemental analysis of the Tuyaodong granitoids in the western EKO.The monzonite and syenogranite show gneissic structure and have Al-rich minerals such as muscovite.The rocks have high contents of SiO₂(67.37%-76.35%),Al₂O₃(12%-14.25%),and K₂O(1.59%-6.01%),but low TiO₂(0.16%-0.56%),Na₂O(2.13%-3.86%),and CaO(0.9%-4.25%),with average A/CNK=1.02 and A/NK=1.47.The chondrite-normalized REE patterns and primitive mantle-normalized spider-diagram of the monzonite and syenogranite are similar,which are enriched in LREE ((La/Yb)_N=5.04-16.76)and have obvious negative Eu anomaly(average δEu=0.47).The primitive mantle-normalized trace element diagrams show that the rocks are enriched in Rb,K and Th,depleted in Nb,Ba,Sr,P and Ti,and have high CaO/Na₂O ratios(0.35 to 1.41).The zircon ²⁰⁶Pb/²³⁸U weighted average age of the granite is (932.7± 2.4) Ma,indicating that the rock was formed in the Early Neoproterozoic.Comprehensive analysis suggests that the Tuyaodong monzonite and syenogranite belong to S-type and their magmas were originated from melting of clastic sediments with minor muddy components in the upper crust.They may have formed in the same collisional extrusion setting, which is in response to the Rodinia supercontinent assembly in the EKO.

New Discovery of the Middle Devonian I-Type Xiwuqi Quartz Diorite in Inner Mongolia and Its Geological Significance

CHENG Tianshe, YANG Wenjing, TENG Chao, ZHANG Xuebin, YANG Xinjie, LAI Lin, WU Rongze, ZHOU Changhong

2023, 37(06): 1624-1633. DOI: 10.19657/j.geoscience.1000-8527.2020.051

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The Xiwuqi area,situated in the southern section of the Paleozoic Hegenshan suture zone,is a key tectonic unit for revealing the evolution of the Paleozoic Hegenshan ocean,a branch of the Paleo-Asian Ocean.There are a few Devonian magmatic rocks in this area,and the evolution of the Devonian Hegenshan ocean is not well studied.In the regional geological survey,a quartz diorite body was newly discovered at Uhelchulu and Xiwuqi.Here,we studied the petrography,zircon U-Pb chronology and geochemistry of the quartz diorite samples.LA-ICP-MS zircon U-Pb dating obtained the weighted average ²⁰⁶Pb/²³⁸U age of 395.8±7.5 Ma (MSWD=1.4, n=8),indicating an Early Devonian pluton emplacement.Geochemistry of the quartz diorite indicates that it is calc-alkaline,characterized by high Si and Na and metaluminous.The pluton is enriched in LILEs(e.g.,Rb,Ba,Th,U,Pb,and Sr) and depleted in HFSEs(e.g.,Zr,Hf,Nb,Ta,and Ti).The ΣREE content is relatively low with moderate LREE/HREE fractionation and weak negative Eu anomalies.Basing on this study and published data,we considered the quartz diorite to be I-type.The Y-Nb and(Y+Nb)-Rb granite discrimination diagrams suggest that the pluton was formed in the volcanic arc setting related to oceanic plate subduction.The discovery of the quartz diorite indicates that the Hegenshan ocean basin probably had existed in the Early Devonian,and it undergone southward subduction beneath the Xilinhot micro-continent.This new finding is different from the conventional understanding that the Hegenshan ocean has only subducted northward.

Experimental Study on Fluid Inclusion Synthesis in Plagioclase

DU Jun, LIU Hongwei, CHANG Honglun

2023, 37(06): 1634-1643. DOI: 10.19657/j.geoscience.1000-8527.2023.036

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Natural fluid inclusions hosted by plagioclase are widely used to reveal mechanism under various geo-logical processes and phenomena.However, the capturing mechanism and subsequent changes, as well as geothermobarometer of such inclusions require validation or modification based on the study of artificially synthesized fluid inclusions in plagioclase.There are no available reports on the technology for fluid inclusion synthesis with host mineral like plagioclase.According to the conventional host mineral fracture healing method, the fluid inclusions were successfully synthesized in host plagioclase through improving the pretreatment of the plagioclase, and capsule assembly in experiments simulating the devolatilization reaction of basaltic crust in the subduction zone under 1-1.5 GPa and 800-900 ℃.Detailed petrographic observations, laser Raman spectroscopic analysis, microthermometric analysis, and preliminary laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of individual fluid inclusions were performed on the synthesized inclusions.We revealed that the plagioclase captured two-phase fluid inclusions with a carbon-rich liquid phase and a water-rich liquid phase at room temperature.The captured fluids have compositions of H₂O+CO₂±CH₄±N₂, with varying salinity depending on the initial fluid used.Additionally, elements such as Cu and Mo were activated and entered the fluid.The plagioclase-based synthesis technology was demonstrated by the successful application in the high-temperature and high-pressure simulation experiments of silica-undersaturated systems.We suggest that the technology of fluid inclusion synthesis in plagioclase bear broad applications in geoscience fields such as geo-fluids and experimental geochemistry in future.

Differentiation Mechanism of Se Concentration in Soil Covering the Jurassic Strata in Chongqing: Case Studies from Jiangjin and Shizhu Regions

LIU Yonglin, ZHAO Jiayu, LIU Yi, WU Mei, XIAO Huixian, LIU Dinghui, TIAN Xinglei

2023, 37(06): 1644-1654. DOI: 10.19657/j.geoscience.1000-8527.2023.062

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The differentiation mechanism of selenium (Se), and its bioavailability in soils developed from same pedogenic rocks in a similar geological environment remains elusive.To further explore the above issue, the surface soil samples above the Jurassic continental red beds were collected from the Jiangjin district (Se-rich) and Shizhu County (Se-poor) of Chongqing, and their chemical compositions were analyzed.This study provides an important reference to reveal the soil Se enrichment mechanism, and shows that the total soil Se content (TSe) at Jiangjin (0.32×10^-6, arithmetic mean) is much higher than that of the Shizhu County (0.21×10^-6).The proportion of Se-rich soil is 46% at Jiangjin and 21% at Shizhu.The phosphate extractable Se (ASe) content and ASe/TSe ratio at Jiangjin are significantly higher than those at Shizhu (0.02×10^-6 and 9.9%, respectively).A stronger positive correlation between the TSe and ASe and organic matter (SOM) in the soil at Jiangjin than at Shizhu are revealed.It is concluded that the soil Se content and its bioavailability are very different from those developed on the Jurassic red beds in the Mesozoic Sichuan foreland basin, and this difference may be caused by the differences in soil physicochemical properties (such as the soil organic matter content), which affected the soil Se migration and enrichment.

Soil Heavy Metal Pollution and Potential Risk Assessment Based on Different Ways of Land Use: A Case Study of Integrated Protection and Restoration Project of Mountains, Rivers, Forests, Fields, Lakes, Grass and Sand in the Liaohe River Basin (Huntai River System)

LI Nan, CAO Mingjie, HAO Zhe, HOU Yongli, CHEN Hongdan, ZHANG Ying

2023, 37(06): 1655-1664. DOI: 10.19657/j.geoscience.1000-8527.2023.034

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In the project “Liaohe River Basin (Huntai River system) mountain, water, forest, farmland, lake, grass and sand integrated protection and restoration project”, basing on soil monitoring data of construction land and agricultural land in restoration area of upper reaches of Huntai River system, we established a soil heavy metal pollution assessment system.The system integrates correlation analysis, single factor index, compound index, potential ecological risk index, and the inverse distance weight interpolation method.The results show that the elements including arsenic, mercury, lead, nickel, cadmium and zinc in agricultural land have similar pollution source, while arsenic, mercury and lead in construction land have similar pollution source.Soil environmental quality was comprehensively assessed by combining the single factor index and composite index.Agricultural land contains cadmium, copper, nickel, zinc and chromium pollution, while construction land has only lead pollution.Ranking of heavy metal pollution area shows chromium>lead>copper>zinc>nickel>cadmium; Ranking of composite pollution type area shows pollution-free>single-element pollution>two-element pollution>three-element pollution. Composite level area ranking shows clean>alert>light pollution.According to the potential ecological risk index, the potential ecological risk levels of single heavy metal on construction land and agricultural land are determined to be of minor hazard level.The comprehensive potential ecological risk index of construction land is 2.13 to 15.23, and that of agricultural land is 5.79 to 41.99, both are within the minor ecological hazard range.Our results can accurately determine the type, location and area of heavy metal pollution, which can provide a basis for soil environmental control in the upper reaches of Huntai River system, and the established research system can also provide references for soil environmental assessment in other basins.

Controlling Factors and Types of Geomorphologic Landscapes in Danxiashan UNESCO Global Geopark of China

GUO Fusheng, LING Yuanyuan, CHEN Liuqin, ZHOU Wanpeng, LI Hongwei, CHENG Liangkai, WU Zhichun, LI Guangrong, GUO Zhen, LI Bin

2023, 37(06): 1665-1679. DOI: 10.19657/j.geoscience.1000-8527.2023.099

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Danxiashan UNESCO Global Geopark is characterized by well-developed Danxia landscape in humid climate of South China, where geomorphologic features and genetic analysis of individual landforms have received much attention in previous studies. However, the controlling factors of landscape development across the Danxia Basin remain poorly understood, and the relationship between fault systems and peaks is yet to be well recognized. In this study, methods such as field survey, rock hardness measurement, remote sensing interpretation of liner structures, and experimental analysis of rock samples were used to illustrate the roles of lithology, depositional facies, and tectonic uplift and dissection in shaping the landscape evolution and to propose a gene-tic and morphologic classification of Danxia landscape. The Upper Cretaceous continental red beds in the Danxia Basin consist of the Changba and Danxia formations. The Changba Formation has a larger outcrop area, forming gentle low hills, while the Danxia Formation is concentrated and characterized by well development of cliffs, representing the typical Danxia landscape. The Danxia Formation is composed of coarse clastic rocks of alluvial fans and eolian sandstones, and is featured by having great thickness, tight cementation, high density and hardness, and being resistant to weathering. In contrast, the Changba Formation consists dominantly of fine-grained muddy clastic rocks deposited in river and lake environments, which are less resistant to weathering and cannot support Danxia landscape with cliffs. The Himalayan tectonic movement likely caused the overall uplift of the Danxia Basin, which resulted in the formation of a series of NE-trending faults and NNE-, NW-, and nearly EW-trending joints. The fracture surfaces may have facilitated subsequent weathering and erosion, producing prominent cliffs, reticulated valleys, and peculiar peaks and rocks. The Danxiashan area is in a subtropical humid climate, where weathering, collapse, water erosion, and karst processes are the main landscape-shaping external forces. Accordingly, the genesis of Danxia landscape is classified into five categories, i.e., collapse-scour, collapse-accumulation, weathering-denudation, river erosion, and dissolution-sedimentation types. The cliff development is a key element of Danxia landscape, and the different combinations of cliff quantities and types formed hills and gorges. Based on these features, the morphological types of Danxia landscape in Danxia-shan are divided into six major categories and twenty-two specific types. This paper has theoretical significance and practical values because it provides a better understanding of the formation processes of Danxia landscape in humid climate, and foundational materials for construction of national park, scientific mountain, and geoscience study travel.

New Perspectives of the Features, Formation, and Evolution of the Special Danxia Landscape in Chenzhou, Hunan

HUANG Leqing, WU Chihua, ZHOU Liyun, JIN Ni, PENG Shiliang, HU Nengyong, YANG Changming, CHEN Jie

2023, 37(06): 1680-1694. DOI: 10.19657/j.geoscience.1000-8527.2023.118

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The Feitianshan-Gaoyiling area in Chenzhou (Hunan Province) is a prominent attraction in South China, known for its distinctive Danxia landform. Unlike typical Danxia landscapes, this area features distinct dome mounds. However, despite its social popularity and scientific value of its unique geomorphology, detailed studies on its geomorphological features, internal genetic mechanism, and evolution have long been overlooked. Through field investigations, we discovered that the Danxia landform in the Feitianshan-Gaoyiling area has seven geomorphological subtypes, including stone village, rock mound, Chibi, stone column, stone wall, cave, and linear trench. Notably, the eastern and western sides of the study area display distinct differences in the Danxia landscape. The eastern side is dominated by dome mounds and stone villages, where the structural strata comprise of eolian desert-facies sandstone, characterized by significant eolian sedimentary structures such as giant staggered bedding, small-scale granular flow layers, and corrugated layers. Meanwhile, the western side of the area features a “top slope, steep slope, foot gentle” peak forest-type Danxia landscape, primarily composed of alluvial fan massive conglomerates. The variations in lithofacies types between the eastern and western sides are the main factors contributing to the diverse geomorphological forms, developed through multistage tectonic transformation, water erosion, weathering, and collapse in the Himalayan period. Using the analysis of the area elevation integral model (HI), we determined that the local Danxia landform is in the early residual hill stage of old age. Accordingly, we propose a three-stage landscape model of “sedimentation pregnant landscape-tectonic uplift landscaping-surface force carving landscape”, to analyze the Danxia landform origin and enhance the brand connotation of Danxia scenic landforms. We aim to better understanding in the distinctive landscape of rock-like Danxia in the humid South China climatic region, and to provide scientific guidance and reference for the development and utilization of Cretaceous Danxia landform geological heritage in South China.

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