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The Fengtai Pb–Zn metallogenic deposits located in China's western region have good minerogenetic conditions and exploration potential. However, the Fengtai mining area passed through complex orogenic process zones, such as subduction, collision, and integration between the Yangtze Plate and the North China Plate. Existing geological research and drilling results showed that the ore bodies of large‐scale Pb–Zn deposits in the ore‐gathering area were steeply inclined, and the detection depths of the majority of the metal deposits were generally less than 300 m. Deep ore‐controlling structures at approximately 500–1,000 m are not well understood. Therefore, high‐precision and large‐depth geophysical detection techniques are necessary to achieve the required accurate detection results. This study revealed that the resistivity values of the ore and host rocks were quite different, which is essential for effective and efficient geophysical prospecting. Based on the petrophysical result, the grounded‐wire transient electromagnetic method system has been found to be one of the better choices for the deep prospecting of the metal deposits and was applied to detect Pb–Zn deposits in the Bafangshan‐Erlihe area. First, the grounded‐wire transient electromagnetic method's effectiveness was verified using results from survey line 1 at a known ore deposit verified by the drilling result. Then, the technique was used to identify deposits in an unexplored area. A deep anticline and ore body were successfully imaged. Most lead‐zinc ore bodies are controlled by the hinge and two wings of the tight anticline, and distributed in the contact zone between limestone and phyllite. The results provide a critical basis for deep prospecting and drilling design. [ABSTRACT FROM AUTHOR]

China is facing many challenges in the area of high‐precision exploration for deep mineral resources, and also in environmental and engineering fields. It has become an urgent task to realize geophysical explorations with high precision and high efficiency in complex environments. It has been found that the traditional transient electromagnetic method (TEM) had a series of problems related to theory, method, and instrument, as well as data interpretation. Based on the reviews of present TEM achievements, three new improved measurements are introduced. The central‐loop system was improved by a large fixed‐loop system; the long‐offset system was changed to the short‐offset one; the resistivity profile was transformed into a virtual wave‐field profile. Finally, this paper points out that the future research direction of the TEM method is in terms of equipment, data processing, and big data information. [ABSTRACT FROM AUTHOR]

The North China-type coalfield is the most important coalfield in China. With the development of Chinese economy, shallow coal resources (<600 m) have been exhausted and large-depth detection is being conducted. Water-inrush is disastrous for coal mining. However, large-depth (600-1200 m) detection of water-filled zones in the North China-type coalfield is a difficult geophysical task due to its low-resistivity coverage. The traditional loop-source transient electromagnetic method (TEM) cannot realize large-depth detection. On the other hand, high-resolution detection of LOTEM is limited by the problem of recording points and large volume effect. To explore the large-depth targets with high-resolution, Short-offset grounded TEM (SOTEM) was applied in the North China-type coalfield. SOTEM is one branch of grounded-wire TEM. The response of SOTEM is calculated using superposing-dipole method rather than the direct-dipole approximation, which is used in the calculation of the response of LOTEM. This paper analyzes the comparison of the resolution and detection depth between SOTEM and loop-source TEM at first. Compared to the loop-source TEM with frequently used parameters, the detection depth of SOTEM with the usual setup parameters is about twice of magnitude, and the resolution capability of SOTEM at large depth is higher than that of loop-source TEM. Then, the resolution capability and detection depth between LOTEM and SOTEM are analyzed. For the grounded-wire TEM, offsets are strictly related to the detection depth. So, the detection depth of LOTEM with larger receiver-transmitter offset will be greater. However, at the depth of 600-1200 m, the resolution capability to conductive targets of SOTEM is higher than that of LOTEM. At last, SOTEM with a 1000-m long source and 1000-2000 m offset is applied to the 1200 m-depth exploration of water-filled zones in the North China-type coalfield. The induced voltage is observed and transformed into magnetic field. Then, the data is inverted using the least mean fourth algorithm. The distribution of water on the top and bottom surface of the large-depth No. 4 coal seam is given, and is verified by the drilling result. [ABSTRACT FROM AUTHOR]

[Display omitted] The resistivities between 1,000 and 2,400 m along line H2 are generally higher than 280 Ωm, while those between 2,600 and 5,000 m are commonly less than 240 Ωm. Therefore, the presence of a fault beneath the area near 2,400 m was inferred. A formation with resistivity values greater than 280 Ωm is also present in the 400–600 m depth range. Along the profile, a 260-Ωm contour is present between the 1,000 and 2,400 m interval. The resistivity values increase as the elevation decreases, and this can serve as the basis for stratigraphic division. Elevations of the relatively low resistivity layers also varied, and these were restricted between 200 and 400 m. The low-resistivity anomalies between 1,000 and 2,400 m along the profile correspond to the low-density section of Zone A3. The TEM investigations in the study area confirmed the existence of Ordovician limestone depressions in the ore-hosting areas delineated by gravity anomalies. Therefore, depths of the limestone surfaces were considered similar to those obtained from the gravity data. The consistency of interpretations based on the two methods utilized in the present study enhanced the reliability of the ore deposits prediction and evaluation in the study area. • Gravity method enables the identification of interfaces related to mineralization. • TEM method can accurately detect the burial depth and location of an interface. • Ore enrichment sites were identified by joint gravity and TEM methods. In this study, a proposed method integrating gravity and transient electromagnetic (TEM) surveys was used for bauxite prospection in Shaanxi Province, China. Although the gravity method enables the identification of interfaces related to mineralization, it is unsuitable for determining the location and burial depth of such an interface. Conversely, the TEM method can accurately detect the burial depth and location of an interface, and thus, its integration with the gravity method can enable the determination of burial depth and shape for interfaces related to the mineralization of bauxite ore bodies. To verify the effectiveness of the integrated approach, gravity and TEM surveys were first conducted in an area in Puxian County, Shaanxi Province, China, which hosts known bauxite deposits. Next, Ordovician limestones associated with depressions were delineated using high-precision gravity survey, and interfaces likely to be related to mineralization were identified. These potential regions were verified using TEM data, and their locations were evaluated. Bauxite ore was identified on the interfaces between limestone and the basal surface of overlying strata, and this was validated using drilling results. This integrated approach was then extended to an unexplored area in Heyang County, Shaanxi Province, and could be applicable to other sedimentary bauxite deposits in the North China Craton. [ABSTRACT FROM AUTHOR]

• FDCSEM has high signal-to-noise ratio and greatly improved exploration resolution. • Detectibility of the ore-forming rock masses is realized by 3D forward modeling. • The inversion results are coincided with the borehole results. • The research idea points out a new prospecting direction for sulfide deposits. Several magmatic Ni-Cu deposits associated with Permian-Triassic mafic-ultramafic intrusions have been discovered during the last three decades in the southern part of the Central Asian Orogenic Belt, the northeastern margin of Tarim, and the margin of the North China Craton. The accurate delineations of the large resistive rock masses are crucial for locating potential ore bodies when they are located beneath rock masse. The controlled-source electromagnetic method (CSEM) is an important tool for investigating resistivity contrast in earth subsurface. In this study, we present a comprehensive example of using frequency domain CSEM survey to delineate the resistive rock masses that are related to the forming of orebody. The horizontal electric field, which is more sensitive to resistive target than the other components, is used in our study. We first built a geophysical model of the survey area based on prior confirmed geophysical and geological information. Then, both forward and inverse modeling were performed in order to assess the detectability of the resistive ore-forming rock masses in the model. Finally, this study acquired field data in the Kalatongke Ni-Cu Deposit, which is located in the Kalatongke District of the southern section of the Central Asian Orogenic Belt, and is specifically part of China's southern Altai Orogenic Belt. The resistive ore-forming rock masses were successfully identified during the survey process and further verified by the drilling results. It was observed that both the synthetic and field examples indicated that the adopted frequency domain CSEM method successfully measured the electrical fields, and could be utilized to explore deeply buried resistive targets in future prospecting activities. [ABSTRACT FROM AUTHOR]

We surveyed influenza activity in a live poultry market in Central China for 16 months, isolating viruses from 1% of 6360 fecal samples. We obtained multiple H3N6, H9N2, H2N9, H3N3, and H4N6 isolates and single H1N1 and H3N2 isolates. Two distinct H3 molecules were identified; other hemagglutinin subtypes were phylogenetically homogeneous. The H3N6 viruses (9 genotypes) and H9N2 viruses (4 genotypes) were genetically heterogeneous, whereas the H2N9, H3N3 and H4N6 viruses had single genotypes. Thirteen representative viruses were tested for their ability to replicate in quail and chickens. All tested viruses replicated in the respiratory tract of quail. Only nine of the viruses were shed in detectable levels in infected chickens, and four of these were detected in less than 50% of infected birds. A single H4N6 isolate caused disease and systemic spread in chickens. These findings show that quail are broadly susceptible to different subtypes of influenza A virus. [Copyright &y& Elsevier]