Geochronology and Geochemistry of the Early Paleozoic Ore-host Volcanic Sequence in the Kalatag Area,East Tianshan,NW China:Implications for the Tectonic Evolution

The East Tianshan contains many late Paleozoic magmatic and polymetallic deposits.Recent studies demonstrate that the early Paleozoic volcanic rocks discovered in the northern region of East Tianshan can be subdivided into the Daliugou,Hongliuxia and Kalatag formations.Here,we report zircon U-Pb ages of volcanic rocks and quartz diorite porphyry,together with whole-rock geochemical and Sr-Nd isotope data of early Paleozoic volcanic rocks,in order to investigate their petrogenesis and geodynamic setting.Zircon U-Pb analyses of the rocks suggest that the Kalatag Formation formed at ca.438-413 Ma.Geochemical characteristics of the early Paleozoic volcanic rocks exhibit typical subduction-related features.They have high Mg^(#)(44-75),positiveε_(Nd)(t)values(0.25-7.88),low^(87)Sr/^(86)Sr ratios(0.70457 to 0.70588)and young two-stage Hf isotope model ages(551-446 Ma),consistent with a depleted mantle origin with limited crustal contamination.The basaltic andesite and andesite have relatively high MgO contents(6.1-9.4 wt%),suggesting that they belong to high-magnesian andesites.They were most likely derived from the partial melting of mantle peridotite caused by the addition of fluids released by subducted oceanic slab.Based on regional geology,geochemical characteristics and previous studies,we infer that the southward subduction of the Junggar Ocean slab resulted in the generation of early Paleozoic volcanic rocks and arc setting-related metallogenic systems in the Kalatag area.

Discussion of reasonable drilling parameters in impregnated diamond bit drilling

The impregnated diamond(ID)bit drilling is one of the main rotary drilling methods in hard rock drilling and it is widely used in mineral exploration,oil and gas exploration,mining,and construction industries.In this study,the quadratic polynomial model in ID bit drilling process was proposed as a function of controllable mechanical operating parameters,such as weight on bit(WOB)and revolutions per minute(RPM).Also,artificial neural networks(ANN)model for predicting the rate of penetration(ROP)was developed using datasets acquired during the drilling operation.The relationships among mechanical operating parameters(WOB and RPM)and ROP in ID bit drilling were analyzed using estimated quadratic polynomial model and trained ANN model.The results show that ROP has an exponential relationship with WOB,whereas ROP has linear relationship with RPM.Finally,the optimal regime of mechanical drilling parameters to achieve high ROP was confirmed using proposed model in combination with rock breaking principal.

Antiplane response of two scalene triangular hills and a semi-cylindrical canyon by incident SH-waves

Antiplane response of two scalene triangular hills and a semi-cylindrical canyon by SH-waves is studied using wave function expansion and complex function method. Firstly, the analytical model is divided into three parts, and the displacement solutions of wave fields are constructed based on boundary conditions in the three regions. Three domains are then conjoined to satisfy the ＂conjunction＂ condition at shared boundary. In addition, combined with the zero-stress condition of semi-cylindrical canyon, a series of infinite algebraic equations for the problem are derived. Finally, numerical examples are provided and the influence of different parameters on ground motion is discussed.

Effect of the lenticles on moisture migration in capillary zone of tailings dam

Small-particle interlayers(lenticles)show some characteristic hydraulic properties and can affect the movement of unsaturated water.In this study,we developed a novel online capillary-water-absorption monitoring device and conducted three groups of comparison tests to simulate lenticle positions and thicknesses with respect to the capillary rise.The results show that the characteristic wetting front exhibits a fast rise in the early stage,a slow rise in the middle stage,and stability in the later stage.The motion of the capillary water in the lenticle is mainly transversal,with the upward curve being"flat,"and the longer is"flat,"the longer is the time needed for the water to move.The interlayer can form a capillary stagnation zone with moisture content close to saturation.The high interlayer may form a discontinuous corrugated capillary zone.Thus,when the wetting front reaches the"coarse-grain(lower)-fine-grain(upper)"interface,the"anti-capillary barrier effect"results in more moisture in the upper layer.Thus,when the wetting front of the capillary water reaches the"fine-grain(upper)-coarse-grain(lower)"interface,the"capillary barrier effect"causes the moisture content of the upper tailings to decreases sharply because of the horizontal movement of the water in the fine medium.It is clear that the presence of lenticles can retard the rise of capillary water by storing water.

Characteristics of crustal variation and extensional break-up in the Western Pacific back-arc region based on a wide-angle seismic profile

The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.

Surveying on two-zone height of sublevel strip mining

The site drilling packer permeability test and TEM to the 2100 workface in Gucheng coalmine determined the two-zone height under sublevel strip mining.The conclusion considers that the lying strata deterioration law of the strip mining is similar to that of the sublevel mining.Thus, against that the actually measured data lacked, it is feasible to refer to the reservation of the waterproof coal pillar in the neighbor coalmine under sublevel situation.However, it is necessary to further launch the research on lying strata deterioration law under sublevel striping mining for the purpose of providing the right foundation for the layout of the workface not mined so far and the reservation of the waterproof coal pillar in the mining area.

Application of the Third Theory of Quantification in Screening Sensitive Geological Factors Influencing Coal and Gas Outburst

The principles of the third theory of quantification were discussed. The concept and calculation method of reaction degree were put forward, which have extended the applying range and scientificalness of the primary reaction. Taking the Zhongmacun mine as an example, the geological factors affecting coal and gas outburst were researched. Eight sensitive factors for the outburst of coal and gas were screened out from 11 geological factors using the method of unit classification and the third theory of quantification. On the basis of this, the Zhongmacun coal mine was classified into several divisions. The practice shows that it is feasible to apply the third theory of quantification to gas geology, which offers a new thought to screen the sensitive geological factors of gas outburst forecast.

Analysis of effects of operating parameters on rate of penetration in drilling process with air down-the-hole hammer

Air down-the-hole(DTH)hammer drilling has long been recognized to have the potential of drilling faster than conventional rotary drill,especially in some hard rocks such as granite,sandstone,limestone,dolomite,etc.with the same weight on bit(WOB)and rotations per minute(RPM).So,it has been widely used in many drilling fields including mineral resource exploration drilling,oil and gas drilling and geothermal drilling.In order to reduce drilling cost by selecting optimal drilling parameters,rate of penetration(ROP)should be estimated accurately and the effects of different factors on ROP should be analyzed.In this research,ANN model with several multi-layer perception back propagation(BP)networks for predicting ROP of air DTH hammer drilling was developed using controllable parameters such as impact energy,impact frequency,WOB,RPM and bit operating time for the formations with a certain drillability index of rock.Several BP neural networks with the different neurons in hidden layers were developed and compared for selecting optimal architecture of ANN.The effects of the drilling parameters such as impact energy,impacting frequency,WOB,RPM and bit operating time on the ROP of air DTH hammer drilling were investigated by trained ANN.From the analyses,the optimum range of drilling parameters for providing high ROP were determined and analyzed for a formation with a certain drillability index of rock.The methodology proposed in this study can be used in many mathematical problems for optimization of drilling process with air DTH hammer.

Information Entropy of Palaeocommunity in Geological History

As an ecosystem in geological history, palaeocommunity has the essence of thermodynamics. This paper introduces the concept of entropy into the study of the evolution of palaeo-community, and proposes four parameters to represent the structure feature of palaeo-community. This theory is used to calculate the evolution mode of branchipod community of Maokou formation in Liziya area, Huaying Moumtain, Sichuan.

Method for predicting cuttings transport using artificial neural networks in foam drilling

Foam is used widely in underbalanced drilling for oil and gas exploration to improve well perfor-mance.Accurate prediction of the cutting transport and pressure loss in the foam drilling is an important way to prevent stuck pipe,lost circulation and to increase the rate of penetration(ROP).In foam drilling,the cuttings transport quality may be defined in terms of cuttings consistency and downhole pressure loss,which are controlled by many factors.Therefore,it is very difficult to establish the mathematical equation that reflects nonlinear relationship among various factors.The field and experimental measurements of these parameters are time consuming and costly.In this study,the authors suggest a cuttings transport mathematical modeling using BPN(back propagation network),RBFN(radial basis function network)and GRNN(general regression neural network)based on various experiment data of cuttings transport of previous researchers and compared the result with experiment data.Results of this study show that the GRNN has a correlation coefficient of 0.99962 and an average error of 0.15 in training datasets,and a correlation coefficient of 0.99881 and an average error of 0.612 in testing datasets,which has higher accuracy and faster training velocity than the BP network or RBFN network.GRNN can be used in many mathematical problems for accurate estimation of cuttings consistency and downhole pressure loss instead of field and experimental measurements for hydraulic design in foam drilling operation.

Dynamic Response of Tunnel Structures in Inhomogeneous Medium Under SHWave:Shear Modulus in Quadratic Functional Form

The task of thiswork is to study the scattering of SHwaves by homogeneous tunnel structures in an unbounded inhomogeneous medium.The shear modulus is assumed to be a function of coordinates(x,y).Atwo-dimensional scattering model is established.Selecting different inhomogeneous parameters,the medium has different properties,expressed as a rigid variation.The stress concentration phenomenon of the structure is analyzed for material design.Based on the complex function theory,the expressions of wave field in the tunnel are derived.The stress concentration phenomenon on the tunnel is discussed with numerical examples.The distribution of dynamic stress concentration factor on the inner and outer boundaries is analyzed under different influencing factors.Finally,it is found that the distribution of dynamic stress concentration factor is significantly affected by the inhomogeneous parameters and reference wave numbers of the medium.

Crustal velocity structure of the Northwest Sub-basin of the South China Sea based on seismic data reprocessing

The deep crustal structure of the Northwest Sub-basin(NWSB)of the South China Sea(SCS)is of great importance for understanding the tectonic nature of the continent-ocean transition(COT)and magmatism in this oceanic basin.The 2-D wide-angle reflection/refraction seismic profile OBS2006-2 is almost parallel to the extinct spreading ridge(ESR)of the NWSB.In addition to the original data,we added the data of two reprocessed OBS stations,and carried out seismic phase re-picking and travel-time imaging to obtain the crustal velocity structure along this profile.Resolution tests demonstrate that the newly acquired velocity structure is more reliable than the prior interpretation.The depth of the Moho(23.5–11.8 km)and crustal thickness(20.5–6.5 km)systematically changes from continental crust of the Xisha Block to the oceanic crust within the NWSB.The COT zone has a width of^20 km and the depth of the Moho decreases from 15.0 to 11.0 km,corresponding to a^4 km decrease in crustal thickness(6–10 km).A high velocity layer(HVL,7.2–7.4 km s–1)exists at the bottom of the crust at the location where the sharp lateral transition of the continental crust to the oceanic crust occurs.Age dating shows that the Doublepeak Seamount was formed at^23 Ma,after the cessation of the NWSB seafloor spreading(~32–25 Ma).The crust beneath the Double-peak Seamount is oceanic with a thickness of 9 km.We infer that this oceanic crust was formed by magmatic upwelling and decompression melting along a pre-existing zone of weakness.

An object detection method for bayberry trees based on an improved YOLO algorithm

To quickly detect and count the number of bayberry trees,this paper improves the YOLO-v4 model and proposes an optimal YOLO-v4 method for detecting bayberry trees based on UAV images.We used the Leaky_ReLU activation function to accelerate the model extraction speed and used the DIoU NMS to retain the most accurate prediction boxes.In order to increase the recall rate of the object detection and construct the optimal YOLO-v4 model,the K-Means clustering method was embedded into DIoU NMS.We trained the model using UAV images of bayberry trees,it was determined that the optimal YOLO-v4 model threshold was 0.25,which had the best extraction effect.The optimal YOLO-v4 model had a detection accuracy of up to 97.78%and a recall rate of up to 98.16%on the dataset.The optimal YOLO-v4 model was compared with YOLO-v4,YOLO-v4 tiny,the YOLO-v3 model,and the Faster R-CNN model.With guaranteed accuracy,the recall rate was higher,up to 97.45%,and the detection of bayberry trees was better in different contexts.The result shows that the optimal YOLO-v4 model can accurately achieve the rapid detection and statistics of the number of bayberry trees in large-area orchards.

Changhsingian sea level changes and brachiopod diversity in the upper Yangtze region

Sedimentary environment and distribution of brachiopods during the Changhsingian in Xingwen, Si-chuan Province of the upper Yangtze region, are statistically analyzed. Changing regularity in diversity of brachiopod is synthetically investigated based on qualitative and quantitative analysis of transgres-sion-regression cycles. The results show that the diversity of brachiopods in this region in the trans-gression (aggradation) sequence is higher than that in the regression (progradation) sequence. The brachiopods in this area began to diversify in the early Changhsingian. And the species diversity had four peak stages which are respectively in the middle Early Changhsingian, late Early Changhsingian, early Late Changhsingian and late Late Changhsingian. The species diversity reached its highest in the late Late Changhsingian but this is followed by a sharp decrease at the end-hanghsingian, indicating the mass extinction of most brachiopod species which were prosperous in the Late Paleozoic.