A 3D Geological Model Constrained by Gravity and Magnetic Inversion and its Exploration Implications for the World-class Zhuxi Tungsten Deposit, South China

The Zhuxi tungsten deposit in Jiangxi Province,South China,contains a total W reserve of about 2.86 Mt at an average grade of 0.54 wt%WO3,representing the largest W deposit in the world.Numerous studies on the metallogeny of the deposit have included its timing,the ore-controlling structures and sedimentary host rocks and their implications for mineral exploration.However,the deep nappe structural style of Taqian-Fuchun metallogenic belt that hosts the W deposit,and the spatial shape and scale of deeply concealed intrusions and their sedimentary host rocks are still poorly defined,which seriously restricts the discovery of new deposits at depth and in surrounding areas of the W deposit.Modern 3 D geological modeling is an important tool for the exploration of concealed orebodies,especially in brownfield environments.There are obvious density contrast and weak magnetic contrast in the ore-controlling strata and granite at the periphery of the deposit,which lays a physical foundation for solving the 3 D spatial problems of the ore-controlling geological body in the deep part of the study area through gravity and magnetic modeling.Gravity data(1:50000)and aeromagnetic data(1:50000)from the latest geophysical surveys of 2016-2018 have been used,firstly,to carry out a potential field separation to obtain residual anomalies for gravity and magnetic interactive inversion.Then,on the basis of the analysis of the relationship between physical properties and lithology,under the constraints of surface geology and borehole data,human-computer interactive gravity and magnetic inversion for 18 cross-sections were completed.Finally,the 3 D geological model of the Zhuxi tungsten deposit and its periphery have been established through these 18 sections,and the spatial shape of the intrusions and strata with a depth of 5 km underground were obtained,initially realizing―transparency‖for ore-controlling bodies.According the analysis of the geophysical,geochemical,and geological characteristics of the Zhuxi tungsten deposit,we discern three principles for prospecting and prediction in the research area,and propose five new exploration targets in its periphery.

Real-time forward modeling and inversion of logging-while-drilling electromagnetic measurements in horizontal wells

Based on the pseudo-analytical equation of electromagnetic log for layered formation,an optimal boundary match method is proposed to adaptively truncate the encountered formation structures.An efficient integral method is put forward to significantly accelerate the convergence of Sommerfeld integral.By asymptotically approximating and subtracting the first reflection/transmission waves from the scattered field,the new Sommerfeld integral method has addressed difficulties encountered by the traditional digital filtering method,such as low computational precision and limited operating range,and realized the acceleration of the computation speed of logging-while-drilling electromagnetic measurements(LWD EM).By making use of the priori information from the offset/pilot wells and interactively adjusting the formation model,the optimum initial guesses of the inversion model is determined in order to predict the nearby formation boundaries.The gradient optimization algorithm is developed and an interactive inversion system for the LWD EM data from the horizontal wells is established.The inverted results of field data demonstrated that the real-time interactive inversion method is capable of providing the accurate boundaries of layers around the wellbore from the LWD EM,and it will benefit the wellbore trajectory optimization and reservoir interpretation.

Fine-tuning inverse metal-support interaction boosts electrochemical transformation of methanol into formaldehyde based on density functional theory

Different from traditional metal-support heterogenous catalysts,inverse heterogeneous catalysts,in which the surface of metal is decorated by metal oxide,have recently attracted increasing interests owing to the unique interracial effect and electronic structure.However,a deep insight into the effect of metaloxide interaction on the catalytic performance still remains a great challenge.In our work,an inverse hematite/palladium(Fe_(2) O_(3)/Pd) hybrid nanostructure,i.e.,the active Fe_(2) O_(3) ultrathin oxide layers partially covering on the surface of Pd nanoparticles(NPs),exhibited superior electrocatalytic performance towards methanol oxidation reaction(MOR) as compared to the bare Pd NPs based on density functional theory calculation.The charge could transfer from Pd to Fe_(2) O_(3) driven by the built-in potential at the interface of Pd and Fe_(2) O_(3),which favors the downshift of d band center of Pd.With the assistance of interfacial hydroxyl OH*,the cleavage of O—H and C—H in CH_(3) OH could take place much easily with lower barrier ene rgy on Fe_(2) O_(3)/Pd than that on pure Pd via two electrons transferring reaction pathways.Our results highlight that the syne rgy of Pd and Fe_(2) O_(3) at the interface could facilitate the electrochemical transformation of methanol into formaldehyde assisted with interfacial hydroxyl OH*.