Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the eff...Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events.展开更多
We report here U-Pb age and in situ Hf isotopic results for detrital and magmatic zircons from one conglomerate and four tuffite samples from the Late Triassic Nadigangri Formation across the North Qiangtang depressio...We report here U-Pb age and in situ Hf isotopic results for detrital and magmatic zircons from one conglomerate and four tuffite samples from the Late Triassic Nadigangri Formation across the North Qiangtang depression, Tibet. Coupled with previously published data in the region, this paper proposes new insights into the geochronological framework for the Nadigangri Formation. The deposition ages of tuffite from top to bottom in the Woruo Mountain, Quem Co and Dongqu River, are 203 Ma, 226 Ma, 221.5 Ma and 221.1 Ma, respectively. The detrital zircons yield a younger cluster of ages of 201.5–225 Ma from the conglomerate of the Quem Co Formation. The Late Triassic Nadigangri Formation defines a temporal range approximately between 201 and 225 Ma(Norian-Rhaetian), including three predominant groups of 220–225 Ma, 210–217 Ma and 201–205 Ma, which correspond with the three main rifting episodes of initial rifting, further rifting and final rifting. Positive εHf(t) value and low model ages in younger detrital zircons suggests a juvenile character. However, the Hf isotopes of magmatic zircons display the presence of reworked ancient crust with 1.1–1.8 Ga. These results provide strong constraints not only on the temporal range of the Late Triassic Nadigangri Formation, but also on the onset of the Qiangtang Mesozoic rift basin.展开更多
Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of ...Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of the Precambrian evolution of the Tarim Basin. In this paper, we studied the petrology, geochemistry, zircon LA-ICPMS U-Pb chronology and zircon Hf isotope of Daxigou anorthosite(DA) which is located at the northern margin of Tarim craton and discussed the rock formation, tectonic and geological significance. Zircons from the intrusions display oscillatory zoning and high Th/U ratios(0.39–1.35), implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that they formed during the Paleoproterozoic age with the weighted 206Pb/238 U average age of 1818±9 Ma, which is significantly different from former's Neoproterozoic age, and is coincidentally identical with its associated syenite granite age within the error range. Studies on petrogeochemistry suggest that DA belongs to medium-sodium peraluminous alkaline type, rich in Pb, La, Th and LILE, and poor in HFSE(Gd, Nd, and Ta). The chondrite-normalized REE pattern is slightly to the right form. The average ∑REE is 317.2×10-6; HREE show moderate fractionation [average LREE/HREE is 14.71, average(La/Yb)N is 24.77; average(La/Sm)N is 3.85, and average(Gd/Yb)N is 3.46]; and the δEu and δCe are not obvious. Their initial Hf isotope ratios and Hf two-stage model ages range from-6.6 to-4.43 and 2.63 to 2.74 Ga, respectively. Taken together, it is suggested that Daxigou anorthosite is a typical volcanic anorthosite and its primary magma could be contaminated by the partial melt Neoarchaean crust and mainly formed in the arc environment, which recoded the tectonic-magma activities response of the Tarim refers to the amalgamation of the supercontinent Columbia.展开更多
This study aims to understand the particle size distribution and depositional styles of glacierassociated deposits in the Moxi basin in southwest China. Based on field surveys, 28 samples from glacier-associated depos...This study aims to understand the particle size distribution and depositional styles of glacierassociated deposits in the Moxi basin in southwest China. Based on field surveys, 28 samples from glacier-associated deposits(including glacial till,fluvioglacial, debris flow, river and lake deposits)were collected and tested in the laboratory. The results showed that the glacier-associated deposits can be differentiated based on particle gradation,particle size distribution and accumulated percentages. We evaluated the evolution of a former dammed lake in the Moxi basin based on glacierassociated deposits. The results of this study also indicated that the Moxi Platform was not formed by a single depositional process but is composed of both fluvioglacial and debris flow deposits. This research shows that the depositional style analysis is useful in identifying different glacier-associated deposits in high mountain regions. Moreover, the evaluation of the differences in particle sizes of the glacierassociated deposits is useful in reconstructing geohazard events in periglacial regions, and this information can help in identifying and reducing the potential risks associated with geo-hazards.展开更多
The Dahutang tungsten polymetallic ore field is located north of the Nanling W-Sn polymetallic metallogenic belt and south of the Middle—Lower Yangtze River Valley Cu-Mo-Au-Fe porphyry-skarn belt.It is a newly discov...The Dahutang tungsten polymetallic ore field is located north of the Nanling W-Sn polymetallic metallogenic belt and south of the Middle—Lower Yangtze River Valley Cu-Mo-Au-Fe porphyry-skarn belt.It is a newly discovered ore field,and probably represents the largest tungsten mineralization district in the world.The Shimensi deposit is one of the mineral deposits in the Dahutang ore field,and is associated with Yanshanian granites intruding into a Neoproterozoic granodiorite batholith.On the basis of geologic studies,this paper presents new petrographic,microthermometric,laser Raman spectroscopic and hydrogen and oxygen isotopic studies of fluid inclusions from the Shimensi deposit.The results show that there are three types of fluid inclusions in quartz from various mineralization stages:liquid-rich two-phase fluid inclusions,vapor-rich two-phase fluid inclusions,and three-phase fluid inclusions containing a solid crystal,with the vast majority being liquid-rich two-phase fluid inclusions.In addition,melt and melt-fluid inclusions were also found in quartz from pegmatoid bodies in the margin of the Yanshanian intrusion.The homogenization temperatures of liquid-rich two-phase fluid inclusions in quartz range from 162 to 363℃ and salinities are 0.5wt%-9.5wt%NaCI equivalent.From the early to late mineralization stages,with the decreasing of the homogenization temperature,the salinity also shows a decreasing trend.The ore-forming fluids can be approximated by a NaCl-H_2O fluid system,with small amounts of volatile components including CO_2,CH_4 and N_2,as suggested by Laser Raman spectroscopic analyses.The hydrogen and oxygen isotope data show that δ5D_(V-smow) values of bulk fluid inclusions in quartz from various mineralization stages vary from-63.8‰ to-108.4‰,and the δ^(18)O_(H2O) values calculated from the δ^(18)O_(V-)smow values of quartz vary from-2.28‰ to 7.21‰.These H-O isotopic data are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water in the early stage,and meteoric water was added and participated in mineralization in the late stage.Integrating the geological characteristics and analytical data,we propose that the ore-forming fluids of the Shimensi deposit were mainly derived from Yanshanian granitic magma,the evolution of which resulted in highly differentiated melt,as recorded by melt and melt-fluid inclusions in pegmatoid quartz,and high concentrations of metals in the fluids.Cooling of the ore-forming fluids and mixing with meteoric water may be the key factors that led to mineralization in the Dahutang tungsten polymetallic ore field.展开更多
Mississippi-Valley’s carbonate-type(MVT)lead-zinc deposits are the most important type of lead-zinc deposits in the southwest of China.In 2013,China Geologica Survey Bureau deployed a project
The Shanmen deposit, located in the Siping area of Jilin Province, is one of large-scale silver deposits in Northeast(NE) China. Due to its high Ag grade, associated gold resources and special tectonic location, this ...The Shanmen deposit, located in the Siping area of Jilin Province, is one of large-scale silver deposits in Northeast(NE) China. Due to its high Ag grade, associated gold resources and special tectonic location, this deposit has important theoretical and ore-prospecting significance. To present new data on the ore genesis, mineralization time and tectonic settings, the relationship between silver mineralization and intrusions in this deposit has been studied and some analyses have been carried out, including LA-ICP-MS zircon U-Pb dating, whole-rock major and trace element analysis and Sr-Nd-Pb isotope analysis of the granitoids associated with silver mineralization. Studies on deposit geology indicate that the ore-hosting granodiorite and monzogranite have intimate genetic relationships with silver mineralization. LA-ICP-MS zircon U-Pb dating results of the both intrusions are 167.6 ± 1.9 Ma and 167.0 ± 1.5 Ma, respectively, implying that the two intrusions and associated silver mineralization in the Shanmen deposit formed during the Middle Jurassic. Major element analytical data suggest that the two intrusions are high-K calc–alkaline series I-type granites and belong to metaluminous and peraluminous rocks. Both intrusions have similar REE characteristics with regard to the relative enrichment of LREEs, depletion of HREEs, obvious fractionation of LREEs and HREEs(ΣLREE/ΣHREE = 8.68–14.09,(La/Yb)_N = 12.51–21.96), moderately negative Eu anomalies as well as weakly negative Ce anomalies(δEu = 0.56–0.71, δCe = 0.93–1.09). Moreover, the samples are generally enriched in LILEs and depleted in HFSEs. The rock assemblages and geochemical characteristics of granitoids in the Shanmen deposit suggest that they formed in an active continental margin associated with the Paleo-Pacific plate subduction. The Sr-Nd-Pb isotope compositions show that both the granodiorite and monzogranite have low Sr initial ratios and high Sm/Nd initial ratios. The ε_(Nd)(t) values and young Nd-model ages are-3.2 to-1.7 and 990 Ma to 1110 Ma, respectively. Considering the Sr-Nd isotope compositions, in conjunction with the relatively high ~(206)Pb, ~(207)Pb and ~(208)Pb, alongside the relatively low ~(204)Pb, it can be concluded that the Middle Jurassic intermediate-acidic magma represented by the studied monzogranite and granodiorite in the Shanmen deposit, was derived from the partial melting of juvenile lower crust enriched in mantle-derived materials and affected by the mixing of ancient crustal materials during the ascension and intrusion processes.展开更多
Ceratodus is a form genus of ceratodontid lungfishes.Until now,only 14 specimens have been reported from the Mesozoic of China.Detailed measurements and characteristic comparisons based on 15 well-preserved lungfish t...Ceratodus is a form genus of ceratodontid lungfishes.Until now,only 14 specimens have been reported from the Mesozoic of China.Detailed measurements and characteristic comparisons based on 15 well-preserved lungfish tooth plates of Ceratodus type,uncovered from the upper member of the Upper Jurassic Shaximiao Formation at Luojiashan,Qianfeng District,Guang'an,Sichuan Province in 2019,allow us to establish a new species,Ceratodus guanganensis sp.nov.,on the basis of its small swollen irregular triangular tooth plate with four low and swollen radial crests on the occlusal surface without denticles.Other specimens from the same locality can be referred to C.szechuanensis and C.youngi.This is the first discovery of Ceratodus in the Guang'an region and represents the fifth Ceratodus fossil site in the Sichuan Basin.The discovery indicates that the climate was hot and arid in the Sichuan Basin during the Late Jurassic,and reveals a tectonic paleogeographic relationship between the Yangtze block in southwestern China and the Kola Basin in northern Thailand.展开更多
The Tiegelongnan Cu(Au,Ag)deposit in central Tibet contains more than 10 Mt of copper ranking 29 th in the world.It is characterized by typical porphyry-epithermal alteration and mineralization.In order to improve the...The Tiegelongnan Cu(Au,Ag)deposit in central Tibet contains more than 10 Mt of copper ranking 29 th in the world.It is characterized by typical porphyry-epithermal alteration and mineralization.In order to improve the understanding of porphyry-epithermal copper deposit in Tibet,new zircon U-Pb age and sulfur isotope data along with published data in the Tiegelongnan are presented to investigate the formation and preservation mechanism.Ore-related intrusive rocks in the Tiegelongnan including Early Cretaceous(about 120 Ma)granodiorite porphyry and diorite porphyry are closely related to the northward subduction of Bangongco-Nujiang ocean.Sulfur mainly comes from deep magma,and ore-forming fluid is affected by both magmatic and meteoric water.The metallogenic setting of Tiegelongnan is consistent with those of Andean porphyry copper deposits in South America.The cover of the Meiriqiecuo Formation volcanic rocks,Lhasa-Qiangtang collision and India-Eurasian collision have significance in the preservation and uplift of the deposit.The formation,preservation and discovery of Tiegelongnan play an important role in exploration of ancient porphyry-epithermal deposits in Tibet.展开更多
The Haizi diabase-granite porphyry composite rock mass is located in the Wuding-Yanjing taphrogenic trough within the Paleoproterozoic Kangdian fault-uplift zone. According to field observations, the diabase is divide...The Haizi diabase-granite porphyry composite rock mass is located in the Wuding-Yanjing taphrogenic trough within the Paleoproterozoic Kangdian fault-uplift zone. According to field observations, the diabase is divided into two types: central facies and marginal facies;the granite porphyry directly contacts the central facies of diabase without transitional intermediate rock. In order to disclose its geological and petrological significances, this paper carried out the LA-ICP-MS zircon U-Pb dating and geochemical investigation on both masses of Haizi diabase and granite porphyry. The results showed that the207Pb/206Pb weighted average age of granite porphyry is 1764 ± 18 Ma and diabase 1765 ± 5.4 Ma. The geochemical investigations revealed that the Haizi diabase is a kind of high-potassium alkaline basalt and the granite porphyry a kind of low-potassium rhyolite, both enriched with high field intensity elements and depleted in large-ion lithophile elements;there is obvious component intermittence between the diabase and the granite porphyry, both being bimodal and showing characteristics of continental rift valley magmatite. The?in situ?Hf isotope of dating zircon showed that mantle materials participated in the formation and emplacement of Haizi granite porphyry and crust materials participated in the formation of diabase. This meant that crustal remelting and accretion of new crust occurred in this region in the 1.7 Ga period. It can be therefore inferred that the Haizi bimodal intrusive rock came into being due to the breakup of Kunyang rift valley and rapid ascent of mantle materials in the 1.7 Ga period, which echoed the global Columbia supercontinent breakup and was the first petrological record of that breakup found at the southwest margin of Yangtze platform.展开更多
Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle...Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme.As one of the typical Sturtian-Marinoan interglacial deposits,the Datangpo Formation was widely distributed in South China with shales continuously deposited.The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval.Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province.Based on measured episodicδ^(13)C_(org) perturbations,three positive shifts and three negative excursions are identified.Aδ^(13)C_(org)-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally.Meanwhile,theδ^(13)C_(org) vertical gradients changed dynamically throughout the formation.This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation,coinciding with the potential oxygenation.展开更多
Predicting the failure time of a landslide is considered as challenging work in the field of landslide research,and inverse velocity is proved to be an effective and convenient method.The onset of acceleration(OOA)has...Predicting the failure time of a landslide is considered as challenging work in the field of landslide research,and inverse velocity is proved to be an effective and convenient method.The onset of acceleration(OOA)has a crucial effect on the prediction failure time from the inverse velocity method.However,a simple method to identify OOA points is lacked,and most of the identifications rely on expert experience.Therefore,this study presents an application of a simple framework developed to identify the OOA by analyzing monitoring velocity data in three steps,including selection of the absolute value of velocity,reliable area identification and OOA identification.A new parameter based on exponential moving average(EMA)is developed to identify the landslide OOA.The framework is applied to three historical case studies to test its practicability and effectiveness.The forecasting results show a good correspondence between the accuracy rate and the coefficient of determination(R2).The predicted failure time according to the linear extrapolation starting from the identified OOA points is acceptable with a high R2 and high accuracy.展开更多
Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sic...Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sichuan Province, and are influenced by slope structure, which can be divided into open, lock, strip, and dumbbell types, as well as soil type and meso-structure, which can be classified as layered rock–soil aggregate, block-soil, and grainsoil. In this study, the evolution of four types of structures, such as layered-dumbbell, block-soil lock, banded block-soil, and block-soil open types, were analyzed by field surveys, surface and deep displacement monitoring, and Flac3 D. It was found that the Danba reach of the Dadu River showed incised valley through the evolution from wide to slow valley affected by internal and external geological processes since the Quaternary Glaciation. In the layered-dumbbell rock–soil aggregate, the main sliding pattern is multi-stage sliding at different depths. Circular sliding in the trailing edge and plane sliding along the bedrock in the front edge body occurin the block-soil-lock type aggregate. Large-scale multi-level and circular sliding over long distances occur in the banded block-soil aggregate. The blocksoil open type is stable, with only circular sliding occurring in local and shallow surfaces of the body. The monitoring and numerical simulation results further show that slope structure and regularity have diversified with RSALs. The results provide a basis for analyzing the stability mechanism of RSALs and preventing RSALs in deeply incised valleys.展开更多
High/ultrahigh-pressure(HP/UHP)metamorphic complexes,such as eclogite and blueschist,are generally regarded as significant signature of paleo-subduction zones and paleo-suture zones.Glaucophane eclogites have been rec...High/ultrahigh-pressure(HP/UHP)metamorphic complexes,such as eclogite and blueschist,are generally regarded as significant signature of paleo-subduction zones and paleo-suture zones.Glaucophane eclogites have been recently identified within the Lancang Group characterized by accretionary mélange in the Changning-Menglian suture zone,at Bangbing in the Shuangjiang area of southeastern Tibetan Plateau.The authors report the result of petrological,mineralogical and metamorphism investigations of these rocks,and discuss their tectonic implications.The eclogites are located within the Suyi blueschist belt and occur as tectonic lenses in coarse-grained garnet muscovite schists.The major mineral assemblage of the eclogites includes garnet,omphacite,glaucophane,phengite,clinozoisite and rutile.Eclogitic garnet contains numerous inclusions,such as omphacite,glaucophane,rutile,and quartz with radial cracks around.Glaucophane and clinozoisite in the matrix have apparent optical and compositional zonation.Four stages of metamorphic evolution can be determined:The prograde blueschist facies(M_(1)),the peak eclogite facies(M_(2)),the decompression blueschist facies(M_(3))and retrograde greenschist facies(M_(4)).Using the Grt-Omp-Phn geothermobarometer,a peak eclogite facies metamorphic P-T condition of 3000–3270 MPa and 617–658℃ was determined,which is typical of low-temperature ultrahigh-pressure metamorphism.The comparison of the geological characteristics of the Bangbing glaucophane eclogites and the Mengku lawsonite-bearing retrograde eclogites indicates that two suites of eclogites may have formed from significantly different depths or localities to create the tectonic mélange in a subduction channel during subduction of the Triassic Changning-Menglian Ocean.The discovery of the Bangbing glaucophane eclogites may represent a new oceanic HP/UHP metamorphic belt in the Changning-Menglian suture zone.展开更多
The interpretation of regional gravity and magnetic data,especially the extracted information about concealed targets and structures,provide important evidence for geological structure research,oil-gas resource assess...The interpretation of regional gravity and magnetic data,especially the extracted information about concealed targets and structures,provide important evidence for geological structure research,oil-gas resource assessment,mineral potential forecast and prospective area delineation.Several interpretation methods have展开更多
The Ailao Mountain is one of the most important metallogenic belts of polymetallic deposits in the Sanjiang region,southwestern China.Located in the southern segment of this metallogenic belt,the newly-discovered Chan...The Ailao Mountain is one of the most important metallogenic belts of polymetallic deposits in the Sanjiang region,southwestern China.Located in the southern segment of this metallogenic belt,the newly-discovered Chang’an gold deposit is large in scale(Fig.1A),and has attracted much attention among geologists.The展开更多
Objective Lhasa terrane has recorded the geologic history concerning the formation and evolution of Paleo-Tethys and the intra-continental convergence in Qinghai–Tibet Plateau(Yin and Harrison,2000).Previous investig...Objective Lhasa terrane has recorded the geologic history concerning the formation and evolution of Paleo-Tethys and the intra-continental convergence in Qinghai–Tibet Plateau(Yin and Harrison,2000).Previous investigations have focused on the initial timing of the India-Asia collision and the Cretaceous–Cenozoic magmatism and sedimentation(Wang Tianyang et al.,2017),however,展开更多
The newly-discovered Xiyi lead-zinc deposit is a large deposit located in the north central Baoshan block of the southern Sanjiang metallogenic belt section,Southwest China.The surface of the deposit is mainly covered
The Wumeng Mountain area is located at the juncture of Sichuan,Guizhou,and Yunnan provinces in China.In terms of geotectonic setting,it lies in the suture part of two giant tectonic domains,namely the Tethys-Himalayan...The Wumeng Mountain area is located at the juncture of Sichuan,Guizhou,and Yunnan provinces in China.In terms of geotectonic setting,it lies in the suture part of two giant tectonic domains,namely the Tethys-Himalayan sedimentary zone and Circum-Pacific Ocean tectonic domain.There are 38 counties in the Wumeng Mountain area(Fig.1),with a total area of 107×10^3 km^2 and a population of about 23×10^6.The maximum altitude in this area is 4017 m,with the elevation difference between various landforms being up to more than 2000 m.This area suffers frequently occurring natural disasters,severe rocky desertification,unevenly distributed water resources,rare agricultural land per capita,and fragile ecological environment.As a result,it has long been a difficult problem for the local poverty-stricken people to get rich.展开更多
基金supported by the project of the China Geological Survey(No.DD20221746)the National Natural Science Foundation of China(Grant Nos.41101086)。
文摘Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events.
基金funded by the National Natural Science Foundation of China(Grant No.41502112 and 41702119)a project program under China Geological Survey(No.DD20160159)
文摘We report here U-Pb age and in situ Hf isotopic results for detrital and magmatic zircons from one conglomerate and four tuffite samples from the Late Triassic Nadigangri Formation across the North Qiangtang depression, Tibet. Coupled with previously published data in the region, this paper proposes new insights into the geochronological framework for the Nadigangri Formation. The deposition ages of tuffite from top to bottom in the Woruo Mountain, Quem Co and Dongqu River, are 203 Ma, 226 Ma, 221.5 Ma and 221.1 Ma, respectively. The detrital zircons yield a younger cluster of ages of 201.5–225 Ma from the conglomerate of the Quem Co Formation. The Late Triassic Nadigangri Formation defines a temporal range approximately between 201 and 225 Ma(Norian-Rhaetian), including three predominant groups of 220–225 Ma, 210–217 Ma and 201–205 Ma, which correspond with the three main rifting episodes of initial rifting, further rifting and final rifting. Positive εHf(t) value and low model ages in younger detrital zircons suggests a juvenile character. However, the Hf isotopes of magmatic zircons display the presence of reworked ancient crust with 1.1–1.8 Ga. These results provide strong constraints not only on the temporal range of the Late Triassic Nadigangri Formation, but also on the onset of the Qiangtang Mesozoic rift basin.
基金founded by the 305 Project of State Science and Technology Support Program(Grant No.2011BAB06B04-05)the China Postdoctoral Science Foundation Funded Project(Grant No.2012M521492 and 2013T60758)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(Grant No.CUG120840,CUG120702 and CUGL120296)
文摘Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of the Precambrian evolution of the Tarim Basin. In this paper, we studied the petrology, geochemistry, zircon LA-ICPMS U-Pb chronology and zircon Hf isotope of Daxigou anorthosite(DA) which is located at the northern margin of Tarim craton and discussed the rock formation, tectonic and geological significance. Zircons from the intrusions display oscillatory zoning and high Th/U ratios(0.39–1.35), implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that they formed during the Paleoproterozoic age with the weighted 206Pb/238 U average age of 1818±9 Ma, which is significantly different from former's Neoproterozoic age, and is coincidentally identical with its associated syenite granite age within the error range. Studies on petrogeochemistry suggest that DA belongs to medium-sodium peraluminous alkaline type, rich in Pb, La, Th and LILE, and poor in HFSE(Gd, Nd, and Ta). The chondrite-normalized REE pattern is slightly to the right form. The average ∑REE is 317.2×10-6; HREE show moderate fractionation [average LREE/HREE is 14.71, average(La/Yb)N is 24.77; average(La/Sm)N is 3.85, and average(Gd/Yb)N is 3.46]; and the δEu and δCe are not obvious. Their initial Hf isotope ratios and Hf two-stage model ages range from-6.6 to-4.43 and 2.63 to 2.74 Ga, respectively. Taken together, it is suggested that Daxigou anorthosite is a typical volcanic anorthosite and its primary magma could be contaminated by the partial melt Neoarchaean crust and mainly formed in the arc environment, which recoded the tectonic-magma activities response of the Tarim refers to the amalgamation of the supercontinent Columbia.
基金funded by The China Geological Survey (Grant No. 12120113010200)Ministry of Science and Technology of the People’s Republic of China (Grant No. 2011FY110100-5)The National Natural Science Foundation of China (Grant No. 41101086)
文摘This study aims to understand the particle size distribution and depositional styles of glacierassociated deposits in the Moxi basin in southwest China. Based on field surveys, 28 samples from glacier-associated deposits(including glacial till,fluvioglacial, debris flow, river and lake deposits)were collected and tested in the laboratory. The results showed that the glacier-associated deposits can be differentiated based on particle gradation,particle size distribution and accumulated percentages. We evaluated the evolution of a former dammed lake in the Moxi basin based on glacierassociated deposits. The results of this study also indicated that the Moxi Platform was not formed by a single depositional process but is composed of both fluvioglacial and debris flow deposits. This research shows that the depositional style analysis is useful in identifying different glacier-associated deposits in high mountain regions. Moreover, the evaluation of the differences in particle sizes of the glacierassociated deposits is useful in reconstructing geohazard events in periglacial regions, and this information can help in identifying and reducing the potential risks associated with geo-hazards.
基金supported by the Old Mine Prospecting Technology Innovation and Demonstration Projects of China Geological Survey(No.1212011220737)
文摘The Dahutang tungsten polymetallic ore field is located north of the Nanling W-Sn polymetallic metallogenic belt and south of the Middle—Lower Yangtze River Valley Cu-Mo-Au-Fe porphyry-skarn belt.It is a newly discovered ore field,and probably represents the largest tungsten mineralization district in the world.The Shimensi deposit is one of the mineral deposits in the Dahutang ore field,and is associated with Yanshanian granites intruding into a Neoproterozoic granodiorite batholith.On the basis of geologic studies,this paper presents new petrographic,microthermometric,laser Raman spectroscopic and hydrogen and oxygen isotopic studies of fluid inclusions from the Shimensi deposit.The results show that there are three types of fluid inclusions in quartz from various mineralization stages:liquid-rich two-phase fluid inclusions,vapor-rich two-phase fluid inclusions,and three-phase fluid inclusions containing a solid crystal,with the vast majority being liquid-rich two-phase fluid inclusions.In addition,melt and melt-fluid inclusions were also found in quartz from pegmatoid bodies in the margin of the Yanshanian intrusion.The homogenization temperatures of liquid-rich two-phase fluid inclusions in quartz range from 162 to 363℃ and salinities are 0.5wt%-9.5wt%NaCI equivalent.From the early to late mineralization stages,with the decreasing of the homogenization temperature,the salinity also shows a decreasing trend.The ore-forming fluids can be approximated by a NaCl-H_2O fluid system,with small amounts of volatile components including CO_2,CH_4 and N_2,as suggested by Laser Raman spectroscopic analyses.The hydrogen and oxygen isotope data show that δ5D_(V-smow) values of bulk fluid inclusions in quartz from various mineralization stages vary from-63.8‰ to-108.4‰,and the δ^(18)O_(H2O) values calculated from the δ^(18)O_(V-)smow values of quartz vary from-2.28‰ to 7.21‰.These H-O isotopic data are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water in the early stage,and meteoric water was added and participated in mineralization in the late stage.Integrating the geological characteristics and analytical data,we propose that the ore-forming fluids of the Shimensi deposit were mainly derived from Yanshanian granitic magma,the evolution of which resulted in highly differentiated melt,as recorded by melt and melt-fluid inclusions in pegmatoid quartz,and high concentrations of metals in the fluids.Cooling of the ore-forming fluids and mixing with meteoric water may be the key factors that led to mineralization in the Dahutang tungsten polymetallic ore field.
基金granted by the China State Mineral Resources Investigation Program (Grant No.12120113050700)
文摘Mississippi-Valley’s carbonate-type(MVT)lead-zinc deposits are the most important type of lead-zinc deposits in the southwest of China.In 2013,China Geologica Survey Bureau deployed a project
基金financially supported by the National Key R&D Program of China (No. 2017YFC0601304)。
文摘The Shanmen deposit, located in the Siping area of Jilin Province, is one of large-scale silver deposits in Northeast(NE) China. Due to its high Ag grade, associated gold resources and special tectonic location, this deposit has important theoretical and ore-prospecting significance. To present new data on the ore genesis, mineralization time and tectonic settings, the relationship between silver mineralization and intrusions in this deposit has been studied and some analyses have been carried out, including LA-ICP-MS zircon U-Pb dating, whole-rock major and trace element analysis and Sr-Nd-Pb isotope analysis of the granitoids associated with silver mineralization. Studies on deposit geology indicate that the ore-hosting granodiorite and monzogranite have intimate genetic relationships with silver mineralization. LA-ICP-MS zircon U-Pb dating results of the both intrusions are 167.6 ± 1.9 Ma and 167.0 ± 1.5 Ma, respectively, implying that the two intrusions and associated silver mineralization in the Shanmen deposit formed during the Middle Jurassic. Major element analytical data suggest that the two intrusions are high-K calc–alkaline series I-type granites and belong to metaluminous and peraluminous rocks. Both intrusions have similar REE characteristics with regard to the relative enrichment of LREEs, depletion of HREEs, obvious fractionation of LREEs and HREEs(ΣLREE/ΣHREE = 8.68–14.09,(La/Yb)_N = 12.51–21.96), moderately negative Eu anomalies as well as weakly negative Ce anomalies(δEu = 0.56–0.71, δCe = 0.93–1.09). Moreover, the samples are generally enriched in LILEs and depleted in HFSEs. The rock assemblages and geochemical characteristics of granitoids in the Shanmen deposit suggest that they formed in an active continental margin associated with the Paleo-Pacific plate subduction. The Sr-Nd-Pb isotope compositions show that both the granodiorite and monzogranite have low Sr initial ratios and high Sm/Nd initial ratios. The ε_(Nd)(t) values and young Nd-model ages are-3.2 to-1.7 and 990 Ma to 1110 Ma, respectively. Considering the Sr-Nd isotope compositions, in conjunction with the relatively high ~(206)Pb, ~(207)Pb and ~(208)Pb, alongside the relatively low ~(204)Pb, it can be concluded that the Middle Jurassic intermediate-acidic magma represented by the studied monzogranite and granodiorite in the Shanmen deposit, was derived from the partial melting of juvenile lower crust enriched in mantle-derived materials and affected by the mixing of ancient crustal materials during the ascension and intrusion processes.
基金This work has been funded by the Land and Resources survey project(Grant No.DD20221690 and DD20190524).
文摘Ceratodus is a form genus of ceratodontid lungfishes.Until now,only 14 specimens have been reported from the Mesozoic of China.Detailed measurements and characteristic comparisons based on 15 well-preserved lungfish tooth plates of Ceratodus type,uncovered from the upper member of the Upper Jurassic Shaximiao Formation at Luojiashan,Qianfeng District,Guang'an,Sichuan Province in 2019,allow us to establish a new species,Ceratodus guanganensis sp.nov.,on the basis of its small swollen irregular triangular tooth plate with four low and swollen radial crests on the occlusal surface without denticles.Other specimens from the same locality can be referred to C.szechuanensis and C.youngi.This is the first discovery of Ceratodus in the Guang'an region and represents the fifth Ceratodus fossil site in the Sichuan Basin.The discovery indicates that the climate was hot and arid in the Sichuan Basin during the Late Jurassic,and reveals a tectonic paleogeographic relationship between the Yangtze block in southwestern China and the Kola Basin in northern Thailand.
基金funded by the National Natural Science Foundation of China(42002103)the Technical Service for Quality Monitoring of Mineral Exploration in Tiegelongnan Mining Area,Duolong Ore district,Gaize County,Tibet(XZJL-JS-2021-004)+1 种基金the Chinese Geological Survey(DD20190167)the Basal Research Fund of Chinese Academy of Geological Sciences(KK2017)。
文摘The Tiegelongnan Cu(Au,Ag)deposit in central Tibet contains more than 10 Mt of copper ranking 29 th in the world.It is characterized by typical porphyry-epithermal alteration and mineralization.In order to improve the understanding of porphyry-epithermal copper deposit in Tibet,new zircon U-Pb age and sulfur isotope data along with published data in the Tiegelongnan are presented to investigate the formation and preservation mechanism.Ore-related intrusive rocks in the Tiegelongnan including Early Cretaceous(about 120 Ma)granodiorite porphyry and diorite porphyry are closely related to the northward subduction of Bangongco-Nujiang ocean.Sulfur mainly comes from deep magma,and ore-forming fluid is affected by both magmatic and meteoric water.The metallogenic setting of Tiegelongnan is consistent with those of Andean porphyry copper deposits in South America.The cover of the Meiriqiecuo Formation volcanic rocks,Lhasa-Qiangtang collision and India-Eurasian collision have significance in the preservation and uplift of the deposit.The formation,preservation and discovery of Tiegelongnan play an important role in exploration of ancient porphyry-epithermal deposits in Tibet.
文摘The Haizi diabase-granite porphyry composite rock mass is located in the Wuding-Yanjing taphrogenic trough within the Paleoproterozoic Kangdian fault-uplift zone. According to field observations, the diabase is divided into two types: central facies and marginal facies;the granite porphyry directly contacts the central facies of diabase without transitional intermediate rock. In order to disclose its geological and petrological significances, this paper carried out the LA-ICP-MS zircon U-Pb dating and geochemical investigation on both masses of Haizi diabase and granite porphyry. The results showed that the207Pb/206Pb weighted average age of granite porphyry is 1764 ± 18 Ma and diabase 1765 ± 5.4 Ma. The geochemical investigations revealed that the Haizi diabase is a kind of high-potassium alkaline basalt and the granite porphyry a kind of low-potassium rhyolite, both enriched with high field intensity elements and depleted in large-ion lithophile elements;there is obvious component intermittence between the diabase and the granite porphyry, both being bimodal and showing characteristics of continental rift valley magmatite. The?in situ?Hf isotope of dating zircon showed that mantle materials participated in the formation and emplacement of Haizi granite porphyry and crust materials participated in the formation of diabase. This meant that crustal remelting and accretion of new crust occurred in this region in the 1.7 Ga period. It can be therefore inferred that the Haizi bimodal intrusive rock came into being due to the breakup of Kunyang rift valley and rapid ascent of mantle materials in the 1.7 Ga period, which echoed the global Columbia supercontinent breakup and was the first petrological record of that breakup found at the southwest margin of Yangtze platform.
基金Special thanks to Erik Tihelka for improving the English.This study was supported by the National Natural Science Foundation of China(41602126)the China Geological Survey(DD20160018,DD20221661)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0706)Liu Bao-jun Academician Research Funds subsidized by Chengdu Center of China Geological Survey.
文摘Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme.As one of the typical Sturtian-Marinoan interglacial deposits,the Datangpo Formation was widely distributed in South China with shales continuously deposited.The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval.Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province.Based on measured episodicδ^(13)C_(org) perturbations,three positive shifts and three negative excursions are identified.Aδ^(13)C_(org)-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally.Meanwhile,theδ^(13)C_(org) vertical gradients changed dynamically throughout the formation.This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation,coinciding with the potential oxygenation.
基金funded by the National Natural Science Foundation of China(Grant NO.41772324)the Open Foundation of Chengdu Center of China Geological Survey。
文摘Predicting the failure time of a landslide is considered as challenging work in the field of landslide research,and inverse velocity is proved to be an effective and convenient method.The onset of acceleration(OOA)has a crucial effect on the prediction failure time from the inverse velocity method.However,a simple method to identify OOA points is lacked,and most of the identifications rely on expert experience.Therefore,this study presents an application of a simple framework developed to identify the OOA by analyzing monitoring velocity data in three steps,including selection of the absolute value of velocity,reliable area identification and OOA identification.A new parameter based on exponential moving average(EMA)is developed to identify the landslide OOA.The framework is applied to three historical case studies to test its practicability and effectiveness.The forecasting results show a good correspondence between the accuracy rate and the coefficient of determination(R2).The predicted failure time according to the linear extrapolation starting from the identified OOA points is acceptable with a high R2 and high accuracy.
基金funded by the National Science Foundation of China(Grant Nos.41702374,4177020938,2018YFC1505406)China Geological Survey projects(Grant Nos.DD20190640,20190505)
文摘Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sichuan Province, and are influenced by slope structure, which can be divided into open, lock, strip, and dumbbell types, as well as soil type and meso-structure, which can be classified as layered rock–soil aggregate, block-soil, and grainsoil. In this study, the evolution of four types of structures, such as layered-dumbbell, block-soil lock, banded block-soil, and block-soil open types, were analyzed by field surveys, surface and deep displacement monitoring, and Flac3 D. It was found that the Danba reach of the Dadu River showed incised valley through the evolution from wide to slow valley affected by internal and external geological processes since the Quaternary Glaciation. In the layered-dumbbell rock–soil aggregate, the main sliding pattern is multi-stage sliding at different depths. Circular sliding in the trailing edge and plane sliding along the bedrock in the front edge body occurin the block-soil-lock type aggregate. Large-scale multi-level and circular sliding over long distances occur in the banded block-soil aggregate. The blocksoil open type is stable, with only circular sliding occurring in local and shallow surfaces of the body. The monitoring and numerical simulation results further show that slope structure and regularity have diversified with RSALs. The results provide a basis for analyzing the stability mechanism of RSALs and preventing RSALs in deeply incised valleys.
基金supported by the National Natural Science Foundation of China(92055314 and 41602091)the geological survey project of China Geological Survey(DD20160016).
文摘High/ultrahigh-pressure(HP/UHP)metamorphic complexes,such as eclogite and blueschist,are generally regarded as significant signature of paleo-subduction zones and paleo-suture zones.Glaucophane eclogites have been recently identified within the Lancang Group characterized by accretionary mélange in the Changning-Menglian suture zone,at Bangbing in the Shuangjiang area of southeastern Tibetan Plateau.The authors report the result of petrological,mineralogical and metamorphism investigations of these rocks,and discuss their tectonic implications.The eclogites are located within the Suyi blueschist belt and occur as tectonic lenses in coarse-grained garnet muscovite schists.The major mineral assemblage of the eclogites includes garnet,omphacite,glaucophane,phengite,clinozoisite and rutile.Eclogitic garnet contains numerous inclusions,such as omphacite,glaucophane,rutile,and quartz with radial cracks around.Glaucophane and clinozoisite in the matrix have apparent optical and compositional zonation.Four stages of metamorphic evolution can be determined:The prograde blueschist facies(M_(1)),the peak eclogite facies(M_(2)),the decompression blueschist facies(M_(3))and retrograde greenschist facies(M_(4)).Using the Grt-Omp-Phn geothermobarometer,a peak eclogite facies metamorphic P-T condition of 3000–3270 MPa and 617–658℃ was determined,which is typical of low-temperature ultrahigh-pressure metamorphism.The comparison of the geological characteristics of the Bangbing glaucophane eclogites and the Mengku lawsonite-bearing retrograde eclogites indicates that two suites of eclogites may have formed from significantly different depths or localities to create the tectonic mélange in a subduction channel during subduction of the Triassic Changning-Menglian Ocean.The discovery of the Bangbing glaucophane eclogites may represent a new oceanic HP/UHP metamorphic belt in the Changning-Menglian suture zone.
文摘The interpretation of regional gravity and magnetic data,especially the extracted information about concealed targets and structures,provide important evidence for geological structure research,oil-gas resource assessment,mineral potential forecast and prospective area delineation.Several interpretation methods have
基金supported by China Geological Survey (Grant No.1212010633901, 12120115024601)
文摘The Ailao Mountain is one of the most important metallogenic belts of polymetallic deposits in the Sanjiang region,southwestern China.Located in the southern segment of this metallogenic belt,the newly-discovered Chang’an gold deposit is large in scale(Fig.1A),and has attracted much attention among geologists.The
基金financially supported by the National Natural Science Foundation of China(grant No.41502079)China Geological Survey(grants No.[2012]03-002-055 and [2014]01-028-042)
文摘Objective Lhasa terrane has recorded the geologic history concerning the formation and evolution of Paleo-Tethys and the intra-continental convergence in Qinghai–Tibet Plateau(Yin and Harrison,2000).Previous investigations have focused on the initial timing of the India-Asia collision and the Cretaceous–Cenozoic magmatism and sedimentation(Wang Tianyang et al.,2017),however,
文摘The newly-discovered Xiyi lead-zinc deposit is a large deposit located in the north central Baoshan block of the southern Sanjiang metallogenic belt section,Southwest China.The surface of the deposit is mainly covered
文摘The Wumeng Mountain area is located at the juncture of Sichuan,Guizhou,and Yunnan provinces in China.In terms of geotectonic setting,it lies in the suture part of two giant tectonic domains,namely the Tethys-Himalayan sedimentary zone and Circum-Pacific Ocean tectonic domain.There are 38 counties in the Wumeng Mountain area(Fig.1),with a total area of 107×10^3 km^2 and a population of about 23×10^6.The maximum altitude in this area is 4017 m,with the elevation difference between various landforms being up to more than 2000 m.This area suffers frequently occurring natural disasters,severe rocky desertification,unevenly distributed water resources,rare agricultural land per capita,and fragile ecological environment.As a result,it has long been a difficult problem for the local poverty-stricken people to get rich.
