LA-ICP-MS zircon U-Pb dating of tuffites in the Sachakou Pb-Zn mining area, Karakorum, Xinjiang and its establishment of Early Triassic strata

1.Objective In the past decade,a group of medium to giant lead-zinc deposits,represented by Huoshaoyun,Sachakou,and Yuanbaoling,have been discovered in the Aksai Chin region of Karakoram,Xinjiang.They are all located in the Mesozoic carbonate and clastic rock formations.The Sachakou leadzinc mining area is adjacent to the northwest of the Huoshaoyun lead-zinc mining area and is in the same stratigraphic layer as Huoshaoyun.Although many scholars have been arguing about the type and age of Huoshaoyun lead-zinc mineralization,few scholars have paid attention to the classification of the ore-bearing strata in the area.The stratigraphy of the Lower Permian Shenxianwan Group to the Upper Cretaceous Tielongtan Group is exposed in the Sachakou area of Karakorum,Xinjiang,however,the Late Permian-Early Triassic stratigraphy is missing(Fig.1a).Due to the harsh natural conditions in the area and the low level of work,the stratigraphic delineation is not exhaustive,and the regional lithology is dominated by carbonates and clastic rocks,which makes it difficult to identify the age of the regional lithology and causes problems for the exploration and research of lead-zinc in the area.

Influence of confined water on the limit support pressure of tunnel face in weakly water-rich strata

In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.

Failure mechanism and safety control technology of a composite strata roadway in deep and soft rock masses:a case study

The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.

Types,composition and diagenetic evolution of authigenic clay minerals in argillaceous limestone of sepiolite-bearing strata:A case study of Mao-1 Member of Middle Permian Maokou Formation,eastern Sichuan Basin,SW China

The types,occurrence and composition of authigenic clay minerals in argillaceous limestone of sepiolite-bearing strata of the first member of the Middle Permian Maokou Formation(Mao-1 Member)in eastern Sichuan Basin were investigated through outcrop section measurement,core observation,thin section identification,argon ion polishing,X-ray diffraction,scanning electron microscope,energy spectrum analysis and laser ablation-inductively coupled plasma-mass spectrometry.The diagenetic evolution sequence of clay minerals was clarified,and the sedimentary-diagenetic evolution model of clay minerals was established.The results show that authigenic sepiolite minerals were precipitated in the Si4+and Mg2+-rich cool aragonite sea and sepiolite-bearing strata were formed in the Mao-1 Member.During burial diagenesis,authigenic clay minerals undergo two possible evolution sequences.First,from the early diagenetic stage A to the middle diagenetic stage A1,the sepiolite kept stable in the shallow-buried environment lack of Al3+.It began to transform into stevensite in the middle diagenetic stage A2,and then evolved into disordered talc in the middle diagenetic stage B1and finally into talc in the period from the middle diagenetic stage B2to the late diagenetic stage.Thus,the primary diagenetic evolution sequence of authigenic clay minerals,i.e.sepiolite-stevensite-disordered talc-talc,was formed in the Mao-1 Member.Second,in the early diagenetic stage A,as Al3+carried by the storm and upwelling currents was involved in the diagenetic process,trace of sepiolite started to evolve into smectite,and a part of smectite turned into chlorite.From the early diagenetic stage B to the middle diagenesis stage A1,a part of smectite evolved to illite/smectite mixed layer(I/S).The I/S evolved initially into illite from the middle diagenesis stage A2to the middle diagenesis stage B2,and then totally into illite in the late diagenesis stage.Thus,the secondary diagenetic evolution sequence of authigenic clay minerals,i.e.sepiolite-smectite-chlorite/illite,was formed in the Mao-1 Member.The types and evolution of authigenic clay minerals in argillaceous limestone of sepiolite-bearing strata are significant for petroleum geology in two aspects.First,sepiolite can adsorb and accumulate a large amount of organic matters,thereby effectively improving the quality and hydrocarbon generation potential of the source rocks of the Mao-1 Member.Second,the evolution from sepiolite to talc is accompanied by the formation of numerous organic matter pores and clay shrinkage pores/fractures,as well as the releasing of the Mg2+-rich diagenetic fluid,which allows for the dolomitization of limestone within or around the sag.As a result,the new assemblages of self-generation and self-accumulation,and lower/side source and upper/lateral reservoir,are created in the Middle Permian,enhancing the hydrocarbon accumulation efficiency.

Shield Excavation Analysis: Ground Settlement & Mechanical Responses in Complex Strata

This study delves into the effects of shield tunneling in complex coastal strata, focusing on how this constructionmethod impacts surface settlement, the mechanical properties of adjacent rock, and the deformation of tunnelsegments. It investigates the impact of shield construction on surface settlement, mechanical characteristics ofnearby rock, and segment deformation in complex coastal strata susceptible to construction disturbances. Utilizingthe Fuzhou Binhai express line as a case study, we developed a comprehensive numerical model using theABAQUS finite element software. The model incorporates factors such as face force, grouting pressure, jack force,and cutterhead torque. Its accuracy is validated against field monitoring data from engineering projects. Simulationswere conducted to analyze ground settlement and mechanical changes in adjacent rock and segments acrossfive soil layers. The results indicate that disturbances are most significant near the excavation zone of the shieldmachine, with a prominent settlement trough forming and stabilizing around 2.0–3.0 D from the excavation. Theexcavation face compresses the soil, inducing lateral expansion. As grouting pressure decreases, the segmentexperiences upward buoyancy. In mixed strata, softer layers witness increased cutting, intensifying disturbancesbut reducing segment floatation. These findings offer valuable insights for predicting settlements, ensuring segmentand rock safety, and optimizing tunneling parameters.

An intelligent automatic correlation method of oilbearing strata based on pattern constraints:An example of accretionary stratigraphy of Shishen 100 block in Shinan Oilfield of Bohai Bay Basin,East China

Aiming at the problem that the data-driven automatic correlation methods which are difficult to adapt to the automatic correlation of oil-bearing strata with large changes in lateral sedimentary facies and strata thickness,an intelligent automatic correlation method of oil-bearing strata based on pattern constraints is formed.We propose to introduce knowledge-driven in automatic correlation of oil-bearing strata,constraining the correlation process by stratigraphic sedimentary patterns and improving the similarity measuring machine and conditional constraint dynamic time warping algorithm to automate the correlation of marker layers and the interfaces of each stratum.The application in Shishen 100 block in the Shinan Oilfield of the Bohai Bay Basin shows that the coincidence rate of the marker layers identified by this method is over 95.00%,and the average coincidence rate of identified oil-bearing strata reaches 90.02% compared to artificial correlation results,which is about 17 percentage points higher than that of the existing automatic correlation methods.The accuracy of the automatic correlation of oil-bearing strata has been effectively improved.

Endogenic Au-Ag polymetallic ore deposits and ore-bearing potentiality of strata

The problem of ore-bearing potentiality of the strata involves metallogenic theory and ore-search orientation.Studies of the spatial distribution of endogenic Au-Ag polymetallic ore deposits in North Hebei indicated that the strata in which ore deposits occurred range in age from Paleozoic,Proterozoic to Mesozoic.In addition the ore deposits are characterized as being strata-bound in nature.The arise and establishment of "extracting" viewpoint may be attributed to the following three reasons:1) influence by the idea of "ore-source bed";2) limitation of analytical techniques in the 1980s'(especially gold element);and 3) a small number of samples(sampling locations were mostly disturbed by mineralization).Studies have shown that ore-forming materials would most probably come from the deep interior of the Earth.Deep-seated ore-bearing materials including Au-Ag polymetals were brought to the shallow levels by way of mantle plume-mantle sub-plume-mantle branch structure multi-stage evolution,finally leading to the formation of ore deposits.

冲击载荷下叠合岩层巷道围岩的应力演化数值模拟研究——基于岩层运动并行计算系统StrataKing

煤系地层属于典型的层状沉积岩层,这在传统连续介质模型中不能被较好反映。为了探究冲击载荷下叠合岩层巷道围岩的应力演化规律,采用以拉格朗日元与离散元耦合连续-非连续方法为基础发展的岩层运动并行计算系统StrataKing,基于理想化模型分析了巷道上表面附近应力波的叠加。阐明了应力波叠加导致顶板开裂机理,并且探讨了冲击载荷幅值的影响规律。研究发现:在原始压应力波传至巷道上表面附近测点后,该测点的最大主应力刚开始呈下降-上升-下降的变化趋势,这是由原始压、拉应力波不同时刻的叠加不同导致的;由于次级应力波的波长较原始应力波的小,次级压、拉应力波的单独作用更明显,它们的叠加使巷道上表面附近测点能产生更低和更高的最大主应力,甚至导致顶板开裂;冲击载荷幅值越大,近似阶梯增长阶段中拉裂纹平均发展速度越快,巷道围岩最终开裂范围越大,巷道围岩平衡越困难。

岩层运动并行计算系统StrataKing及云平台StrataKing.UniXDE参数确定原则及应用

StrataKing(SK)及StrataKing.UniXDE(SK.U)是针对采动诱发岩层运动的首款GPU并行计算系统和云平台。介绍了主要参数的确定原则。单元尺寸的选取应综合考虑GPU的性能和计算精度。准静力计算时,局部自适应阻尼系数尽量接近上限取。通过浅埋厚煤层岩层运动模拟,展示了SK的大规模计算能力、丰富功能和鲜明矿业特色。对本文结果与相似材料模拟实验结果的异同进行了分析。对已经处于试用阶段的SK.U的使用进行了介绍。

LA-ICP-MS U-Pb Zircon Geochronology,Geochemistry and Kinetics of Wenquan Ore-Bearing Granites from Western Qinling,China

As we know there is a famous East Qinling-Dabie molybdenum belt in china,where many molybdenum deposits located such as super giant Jinduicheng,Sandaozhuang,Shangfanggou and Nannihu molybdenum deposits(Li,2008) ;The molybdenum mineralization in the East Qinling-Dabie belt clusters into three groups or mineralization pulses:233-221,148-138 and 131-112 Ma(Mao et al,2008).

Ore-bearing Formations and Mineral Resource Prospects of the Peripheral Areas of the Tarim Block

The tectonic development of the Tarim block has experienced four stages, i. e. Earth's core accretion and block formation in the Precambrian, margin splitting, opening-closing and piecing up in the Early Palaeozoic, rift formation and plate unification in the Late Palaeozoic, and basin-mountain coupling and landform shaping in the Meso-Cenozoic, forming six ore-bearing formations and ore deposits of various genetic types in the Tianshan Mountains, Kunlun Mountains and Altun Mountains. In the peripheral areas of Tarim there are four giant intercontinental metallogenic belts passing through, the Central Tianshan and southwestern Tianshan belts in the former USSR and the Qinling-Qilian-Kunlun and Palaeo-Tethys belts in China. According to the macro-analysis on the nearly one thousand known deposits (occurrences) and geophysical-geochemical anomalies, and the information from reconnaissance in some areas, the region has very good prospects for mineral resources. Some of the metallogenic belts may well become the reserve bases for exploration of mineral resources in China.

Ore-Bearing Formations of the Precambrian in South China and Their Prospects

In the Precambrian System of the Yangtze and Cathaysian plates six ore-bearing formations can be identified: the Cu-Pb-Zn-bearing formations in volcanic rocks of marine facies of the Neoarchean-Paleoproterozoic, Cu-Au-bearing formations and Pb-Zn-bearing formations in volcanic rocks of marine facies of the Mesoproterozoic, Pb-Zn-bearing formations in volcaniclastic rock and carbonate rock of the Neoproterozoic, Fe-Mn-bearing formations in the volcaniclastic rock of the Neoproterozoic, and Ni-Cr-serpentine-bearing formations in ophiolite and ultrabasic rock of the Meso- and Neoproterozoic. They were mostly formed in the marginal rift valleys of the Yangtze and Cathaysian plates, where occur stratabound and stratiform ore deposits, thermal deposits and porphyry polymetallic deposits. The six regions with ore-bearing formations have good prospects for ore deposits.

New Zircon U-Pb Age of the Ore-bearing Porphyry from the Kuga Copper Deposit in the Eastern Bangongco–Nujiang Matallogenic Belt, Tibet

Objective As the third most important copper polymetallic metallogenic belt in Tibet, the Bangongco-Nujiang metallogenic belt （BNMB） has attracted much attention among geoscientists all over the world （Lin Bin et al., 2017a）. There are two ore clusters in the westem of BNMB, the Duolong giant porphyry-epitherrnal Cu （Au, Ag） ore cluster and the Ga＇erqiong-Galalelarge porphyry- skarn Cu （Au） ore cluster （Lin Bin et al., 2017a; 2017b）. Now, the latest exploration advances show that the Kuga project is the first economic porphyry-skam copper deposit in the eastern of BNMB, with over 0.4 Mt melt copper （333＋334） @ 0.9%. However, the Kuga deposit is poorly studied about its diagenetic age. In this study, we present a zircon U-Pb LA-ICP-MS dating of ore-bearing biotite granite, in order to identify the time of the ore- related magmatism and reveal the relationship with the westem of BNMB.

Geochronology and geochemistry of the ore-bearing intrusion in the Longgen Lead-Zinc deposit in Tibet and its geological significance

1 Introduction The Longgen Lead-Zinc deposit is located in the southern Gangdise-Nyainqentantanglha plate and belongs to the western section of the Nyainqentantanglha copper-lead-zinc-silver metallogenic belt.In this paper,

岩层运动并行计算系统StrataKing及应用

为了克服国外串行商业软件的功能有限、计算规模小和计算效率低的问题,历时10余年,自主研发了拉格朗日元与离散元耦合的岩层运动GPU并行计算系统StrataKing。介绍了Strata-King的计算流程、基本原理和功能,各计算模块均在GPU上执行。通过模拟三点弯梁的开裂过程,检验了StrataKing的正确性。在静水压力条件下,当单元数目较多时,巷道围岩的裂纹以更加弯曲、柔美而非突兀、生硬状向围岩深部发展,这与塑性力学中圆环形的各处均破坏的塑性区有所不同。在采动条件下,工作面煤壁超前支承压力和水平应力均具有峰值,后者与岩层之间的黏结作用有关,这与基于连续介质假定的厚壁筒径向应力特征有所不同。由此,StrataKing的大规模计算能力、丰富的功能和行业鲜明特色得到了进一步呈现。

Evaluation and prediction of earth pressure balance shield performance in complex rock strata:A case study in Dalian,China

This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.

Numerical modeling of destress blasting for strata separation

Destress blasting(DB)implemented along the perimeter of safety pillars is a special application of destressing in coal longwall mining.The goal is to separate relatively more deformed mined areas from safety pillars,such as shaft pillars or cross-cut pillars,to reduce the transfer of high stresses to the protective pillar.This case study aims to numerically simulate selected destress blasts in the Czech part of the Upper Silesian Coal Basin and examine its impact on stress transfer to the safety pillar area.To separate the area between the protective pillar and the longwall(LW),two fans of five 93-mm blast holes(length of 93e100 m)were drilled from the gate roads into the overburden strata.Each set of blast holes was fired separately in two stages without time delay.The explosive charge(gelatin-type of explosive)of each stage is 3450 kg.The two DB stages were fired when the longwall face was approximately 158 m and 152 m away from the blast.A 3D mine-wide model is built and validated with in situ stress measured with hydrofracturing.Mining and destressing in three 5-m thick coal seams are simulated in the region.Numerical modeling of DB is successfully conducted using a rock fragmentation factor a of 0.05 and a stress reduction/dissipation factor β of 0.95.Buffering of transfer of additional stress from the mining area into the safety pillar is evaluated by comparison of yielding volume before and after DB.It is shown that yielding volume drops after DB by nearly 80%in the area of the destressing panel and near the safety shaft pillar.

GEOTECTONIC BACKGROUND OF PYROPHYLLITE MINERALIZATION AND ORE-BEARING VOLCANIC FORMATION IN SOUTHEASTERN COASTAL AREAS,CHINA

The volcanic gas-liguid type of pyrophyllite deposits in the SoutheasternCoastal areas, China are the product of tectono-magama-volcanism in Diwa regions. The pyro-phyllite ore-bearing volcanic formation were formed in the maximum-mobility period of Diwa, which are mainly the Late Jurassic strata and are secondly the Early Cretaceous volcanic-sedi-mentary rock series strata. The lithology of the host rock is mainly rhyolitic crystal-vitric tuff, and the chemical composition is characterized by high silicon rich alumium and low iron, be-longing to the acid-intermediate-acid rock and the kalicalc-calc-alkalic series and the rhyo-lite-rhyodacite assemblage. They play an important role in the pyrophyllite mineralization.

Sedimentology and Paleoenvironmental Characteristics of Fine-grained Sediments in Coal-bearing Strata in the Eastern Ordos Basin:A Case Study of the Exploratory Well in the Zizhou Area

The continuously collected cores from the Permo-Carboniferous coal-bearing strata of the eastern Ordos Basin are essential for studying the hydrocarbon potential in this region.This study adopted sedimentological and geochemical methods to analyze the sedimentary environment,material composition,and geochemical characteristics of the coal-bearing strata.The differences in depositional and paleoclimatic conditions were compared;and the factors influencing the organic matter content of fine-grained sediments were explored.The depositional environment of the Benxi and Jinci formations was lagoon to tidal flat with weakly reduced waters with low salinity and dry-hot paleoclimatic conditions;while that of the Taiyuan Formation was a carbonate platform and shallow water delta front,where the water was highly reductive.The xerothermic climate alternated with the warm and humid climate.The period of maximum transgression in the Permo-Carboniferous has the highest water salinity.The Shanxi Formation was deposited in a shallow water delta front with a brackish and fresh water environment and alternative weak reductiveness.And the paleoclimate condition is dry-hot.The TOC content in fine-grained samples was averaging 1.52%.The main controlling mechanism of organic matter in this area was the input conditions according to the analysis on input and preservation of organic matter.