Application of wide-field electromagnetic method in shale gas survey in Eastern Kunlun,Qinghai province,China

In order to study the distribution of shale gas reservoir in the Babaoshan Basin of Eastern Kunlun,the wide-field electromagnetic(WFEM)survey was carried out to obtain the spatial distribution characteristics of the underground electrical volume resistivity based on the delineation of the scope of the Babaoshan Basin by regional gravity data.The basic characteristics of the basement,basin framework,and extension,vertical change,burial depth of dark mud shale in this area were identified,and the electrical distribution of the Babaoshan mud shale horizon was revealed,which has been proved to be a good geological effect by drilling.The exploration results show that the WFEM has significant effects on the exploration of shale gas occurrence strata,which meets the needs of investigation and evaluation of multi-layered and large-scale shale gas,and plays a good demonstration role in the follow-up shale gas exploration.

Research on the Application of Electromagnetic Method in the Exploration of Altered Rock-type Gold Deposits in the East Kunlun Metallogenic Belt

Introduction The East Kunlun Orogenic Belt is located in the northeastern part of the Qinghai–Tibet Plateau(Li et al.,2007),stretching from the East Kunlun to the Elashan area in an east–west direction(Guo et al.,2018).It is an important part of the Central Orogenic Belt(Xiong et al.,2023).It is considered one of the important gold mineralization regions in the Tethys tectonic domain(Norbu et al.,2023)and an essential potential base for mineral resources in China.Wulonggou and Gouli gold mines have been discovered successively,earning the reputation of the"Golden Belt of Qinghai Province"(Feng et al.,2004;He et al.,2023).

An Overview on the Composition and Age of Upper Crust of Proto-Tethyan Lajishan Intra-oceanic Arc,NE Tibet Plateau

Identification and anatomy of oceanic arcs within ancient orogenic belt are significant for better understanding the tectonic framework and closure process of paleo-ocean basin.This article summarizes the geological,geochemical,and geochronological characteristics of upper crust of Proto-Tethyan Lajishan intra-oceanic arc and provides new data to constrain the subduction evolution of the South Qilian Ocean.The intra-oceanic arc volcanic rocks,including intermediate-mafic lava,breccia,tuff,and minor felsic rocks,are distributed along southern part of the Lajishan ophiolite belt.Geochemical and isotopic compositions indicate that the intermediate-mafic lava were originated from depleted mantle contaminated by sediment melts or hydrous fluids,whereas the felsic rocks were likely generated by partial melting of juvenile mafic crust in intra-oceanic arc setting.Zircons from felsic rocks yield consistent and concordant ages ranging from 506 to 523 Ma,suggesting these volcanic rocks represent the relicts of upper crust of the Cambrian intra-oceanic arc.Combined with the Cambrian forearc ophiolite and accretionary complex,we suggest that the Cambrian intra-oceanic arc in the Lajishan ophiolite belt is belonging to the intra-oceanic arc system which was generated by south-directed subduction in the South Qilian Ocean at a relatively short interval between approximately 530 and 480 Ma.

Early Permian–Late Triassic Magmatism in the Tuotuohe Region of the Qinghai–Tibet Plateau: Constraints on the Tectonic evolution of the Western Segment of the Jinshajiang Suture

In this paper we present new zircon U-Pb ages,whole-rock major and trace element analyses,and zircon Hf isotopic data for magmatic rocks in the Tuotuohe region of the western segment of the Jinshajiang suture.Our aim is to constrain the Early Permian-Late Triassic tectonic evolution of the region.Zircons from the magmatic rocks of the Tuotuohe region are euhedralsubhedral in shape and display fine-scale oscillatory zoning as well as high Th/U ratios （0.4-4.6）,indicating a magmatic origin.The zircon U-Pb ages obtained using LA-ICP-MS are 281 ± 1 Ma,258 ± 1 Ma,244 ± 1 Ma,and 216 ± 1 Ma,which indicate magmatism in the Early Permian-Late Triassic.A diorite from Bashihubei （BSHN） has SiO2 =57.18-59.97 wt％,Al2O3=15.70-16.53 wt％,and total alkalis （Na2O ＋ K2O） =4.46-6.34 wt％,typical of calc-alkaline and metaluminous series.A gabbro from Bashibadaoban （BSBDB） belongs to the alkaline series,and is poor in SiO2 （45.46-54.03 wt％） but rich in Al2O3 （16.19-17.39 wt％） and total alkalis （Na2O ＋ K2O =5.48-6.26 wt％）.The BSHN diorite and the BSBDB gabbro both display an enrichment of LREEs and LILEs and depletion of HFSEs,and they have no obvious Eu anomaly; they have relatively low MgO contents （2.54-4.93 wt％）,Mg# values of 43 to 52,and low Cr and Ni contents （8.07-33.6 ppm and 4.41-14.2 ppm,respectively）,indicating they differentiated from primitive mantle magmas.They have low Nb/U,Ta/ U,and Ce/Pb ratios （1.3-9.6,0.2-0.8,and 0.1-18.1,respectively）,and their initial Hf isotopic ratios range from ＋9.6 to ＋16.9 （BSHN diorite） and ＋6.5 to ＋12.6 （BSBDB gabbro）,suggesting their primary magmas were derived mainly from the partial melting of a mantle wedge that had been metasomatized by subduction fluids.Taking all the new data together,we conclude that the western and eastern segment of the Jinshajiang suture regions underwent identical processes of evolution in the Early Permian-Late Triassic：oceanic crust subduction before the Early Permian,continental collision during the Early-Middle Triassic,and post-collisional extension from the Late Triassic.

OSL chronology and paleoclimatic implications of paleodunes in the middle and southwestern Qaidam Basin, Qinghai-Tibetan Plateau

Aeolian sediments are widely distributed in the Qaidam Basin, northeastern Qinghai-Ti^tan Plateau （QTP）. The pale（xiunes are mainly located at the southeastern, middle and southwestem Qaidam Basin. However, ages ofpaleodunes in the middle and southwestern Qaidam Basin have not been well studied, although they are close to and might connect to the evolution of salt lakes in the cenWal basin. In this study, we use single aliquot regeneration （SAR） protocol of Optically Stimulated Luminescence （OSL） to date the dune sand in these two regions. The results show that： （1） Sand accumulation in these regions started at ca. 4-3 ka and lasted to ca. 0.5 ka when they were stabilized, due to the arid climate in the late Holocene. （2） The underlying fluvial sand was fomaed during deghcialion at 12.6±0.8 ka. （3） The stabilization pe- riods of the paleodunes correspond to stages of glacier advance in the northeastem QTP, during which lower temperatures caused the decrease of evapomlion and increase of the effective moisttwe, leading to an increase of vegetation cover and stabilizalion of the dunes.

Offering the win-win solutions between ecological conservation and livelihood development:National parks in Qinghai, China

National parks as protected areas have been on the spotlight because they are essential in achieving ecological civilization in China.Despite the profound achievements of national parks to conserve nature,the benefits of national parks for local residents remain lacking.Under the theory of harmonious coexistence between human and nature,this study focused on the development of local people’s livelihood in Qinghai’s national parks.We systematically explored the establishment of the national parks in Qinghai Province,analyzed the current prob-lems,and provided the main measures for developing people’s livelihood in protected areas in Qinghai.This study put forward the viewpoint that national parks should set a long-term goal,and gradually advance based on the environmental conditions and appropriately prioritize the improvement of local people’s wellbeing in the future.

Deformation of the Zhangjiazhuang high-speed railway tunnel: an analysis of causal mechanisms using geomorphological surveys and D-InSAR monitoring

On 18 January 2016,the Zhangjiazhuang high-speed railway tunnel in Ledu,Qinghai Province,China,underwent serious deformation and structural damage.A crack formed at the top of the tunnel and the concrete on the crown peeled off.As a result,the tunnel could not be operated for three months.In order to determine the types and spatial distribution of the landslides in the region and the surface deformation characteristics associated with the tunnel deformation,we used field geological and geomorphological surveys,unmanned aerial vehicle image interpretation and differential interferometric synthetic aperture radar(D-In SAR) surface deformation monitoring.Nine ancient and old landslides were identified and analysed in the study area.Surface deformation monitoring and investigation of buildings in several villages on the slope front showed that the tunnel deformation was not related to deep-seated gravitational slope deformation.However,surface deformation monitoring revealed an active NEE–SWW fault in the area intersecting the tunnel at the location of the tunnel rupture.This constitutes a plausible mechanism for the deformation of the tunnel.Our study highlights the need for detailed engineering geomorphological investigations to better predict the occurrence of tunnel deformation events in the future.

Geochemistry and Zircon U-Pb and Hf Isotopes of Early Devonian Hardawu Granites in the Eastern Segment of the Ultrahigh-Pressure Metamorphic Belt, Northern Qaidam Basin

The Hardawu granites in the eastern segment of the ultrahigh-pressure metamorphic belt,the northern Qaidam Basin,were studied by whole-rock major and trace elements and in-situ zircon U-Pb geochronology and Hf isotopes to discuss the petrogenesis and tectonic evolution.Geochronological results show that the granites have a crystallization age of 401±3 Ma,suggesting that they were formed in the Early Devonian.The granites have SiO2 contents of 75.32 wt.%-76.05 wt.%,total alkali contents of 8.23 wt.%-8.36 wt.%,and K2O/Na2O ratios of 1.62-1.91.They were rich in K2O,poor in TiO2,MnO,MgO,and P2O5,and have A/CNK values of 1.05-1.07,Rittmann indexδvalues of 2.05-2.14,and differentiation index(DI)values of 92.85-94.18.They are high potassium calc-alkaline,weakperaluminum,and highly differentiated I-type granites.The granites also show enrichment of large ion lithophile elements(LILE)such as Rb,Ba,and Th,and depletion of high field strength elements(HFSE)such as Nb,Ta,and Ti.The total REE concentrations range from 169 ppm to 232 ppm,with enrichments of light rare earth elements and negative Eu anomalies(δEu=0.39-0.55).The zirconεHf(t)values range from-0.65 to-2.29,and the two-stage model ages(tDM2)changed within a small range of 1.44 to 1.54 Ga,indicating that the magma of the Hardawu granites was originated from the partial melting of Mesoproterozoic lower crustal materials.Combined with previous studies,we suggest that the Hardawu granites were formed in the extensional tectonic setting after the collision between the Qaidam Block and the central and southern Qilian Block in the Early Devonian.