North Guangdong Research Articles

A Preliminary Review of Metallogenic Regularity of Tungsten Deposits in China

AbstractTungsten ore resources are abundant in China with relatively complete types of deposits. Skarn type and quartz vein type deposits are dominated in the tungsten resources, whereas quartz vein type wolframite deposits are most important in terms of exploitation and utilization. Skarn type tungsten deposits are concentratedly distributed in the central Nanling region, such as South Hunan, South Anhui and the eastern Qinling region, while quartz vein type tungsten deposits occur mainly in South China, such as West Fujian, South Jiangxi, North Guangdong and South Hunan. The most important metallogenic epoch of tungsten is the Mesozoic, while the metallogenic tectonic setting is featured by an intracontinental environment after orogeny with sever tectonic movements, deep‐seated faults and frequent magmatic activities, especially Mesozoic granitoids closely related to tungsten‐tin mineralization. 22 metallogenic series of ore deposits characterized by or significantly related to tungsten were defined based on precise statistic information of 1199 tungsten mining areas and thorough the summary of metallogenic regularities. Based on studies of the metallogenic regularity of tungsten deposits, skarn type (or greisen type), quartz vein type and massif‐type of tungsten deposits are thought to be the key prediction types. 65 tungsten‐forming belts and 22 key ore concentration areas were ascertained and a distribution map of tungsten‐forming belts of China was compiled, which provided a theoretical basis for evaluation and prediction of potential tungsten resources.

The Relationship between Radioactive Mineralization and Tungsten Mineralization in Shirenzhang Tungsten Deposit, North Guangdong

The Relationship between Radioactive Mineralization and Tungsten Mineralization in Shirenzhang Tungsten Deposit, North Guangdong

The formation of the Dabaoshan porphyry molybdenum deposit induced by slab rollback

Nanling is the largest W–Sn mineralization belt in the world, the formation of which remains obscure. In contrast to most other deposits in the Nanling region, Dabaoshan is a polymetallic deposit, located in north Guangdong province, southeastern China. Porphyry Mo deposit was found in 2008 in the north part of Dabaoshan ore district. Here we report zircon and molybdenite ages and geochemistry results of zircon and apatite. Zircon U–Pb LA–ICP-MS dating shows that the porphyry Mo deposit formed at 167.0±2.5Ma (2σ), which is identical to the molybdenite Re–Os age for the ore deposit (166±1Ma) within error. These ages are marginally older than the major W–Sn mineralization event in the Nanling region (160±5Ma). Zircon grains associated with the Dabaoshan porphyry Mo deposit have high Ce(IV)/Ce(III) values (356–1300), which indicate high oxygen fugacity, likely associated with plate subduction. Apatite from the Dabaoshan porphyry has high and varied F with low Cl concentrations, suggesting that it formed in a F-enriched environment with high F/Cl components in the magma source. This is consistent with abundant high-F granites in the Nanling region. Chlorine is highly mobile at the early stage of plate subduction. In contrast, F is mainly hosted by minerals that are fairly stable at shallow depths, e.g., apatite, phengite, such that is much less mobile than Cl before phengite decomposition. Therefore, the F/Cl ratio increases with increasing distance from the subduction zone. Compared to the Dexing porphyry deposit to the northeast, the Dabaoshan porphyry has lower Ce(IV)/Ce(III) and high F/Cl. It is also about 5Ma younger than the Dexing porphyry Cu deposits. All these phenomena can be plausibly interpreted by slab rollback of the obliquely subducted Pacific plate in the Jurassic. We propose that the subducting slab reached the Dabaoshan region before ~167Ma, through a “flat” subduction regime, resulted in high oxygen fugacity in the magmas, which is followed by abrupt slab rollback. The onset of slab rollback is the most favorable event that leads to decomposition of phengite in the subducting slab because of abruptly elevated temperatures, releases F and consequently increases F/Cl in magmas. The Ti-in-zircon temperatures of the mineralized porphyry range from 608 to 641°C, with an average of about 630±15°C, whereas average temperature of the barren granodiorite nearby is 700±9°C. Considering that the Mo porphyry deposit appears as an egg shell surrounding the granodiorite and the geochemical behavior of Mo, we propose that the mineralization was related to the assimilation of metamorphosed sedimentary rocks by the granodiorite.

粤北山地常绿阔叶林自然干扰后冠层结构与林下光照动态

Natural disturbance is an important factor causing dynamic changes in forest canopies.An ice storm in southern China in 2008 was responsible for extensive damage to the forest ecosystem.The considerable distribution of canopy gaps created by the ice storm caused dynamic changes in the forest canopy.Therefore,studies to reveal the effects of the ice storm on forest regeneration and to monitor the restoration of damaged forest ecosystems will have significant implications for forestry research.Following the ice storm of 2008,a montane evergreen broad-leaved forest in Chebaling National Nature Reserve in northern Guangdong was investigated and a successive 3-year(2008—2010) community study of the 2 hm2 permanent plot was launched.We analyzed the changes in canopy structure(Canopy Openness and Leaf Area Index) and understory light(Transmitted Direct Solar Radiation,Transmitted Diffuse Solar Radiation and Transmitted Total Solar Radiation) in the forest following the ice storm using hemispherical photography to acquire canopy structure and understory light indexes.A quantitative study on the temporal and spatial variations in canopy structure and understory light as well as on environmental heterogeneity in the forest canopy is of considerable importance.Hemispherical photography is an example of optical remote sensing technology used to measure the parameters of canopy structure and understory light,and has now been widely recommended in the field of ecological research.The Kruskal-Wallis test(a non-parametric alternative to one-way ANOVA) and canonical correlation analysis were employed to analyze the changes in canopy structure and understory light.The main conclusions of this study are described in the following: 1) As the canopy openness shrank and the leaf area index increased,the understory light decreased in the forest during the recovery process following the ice storm;2) A highly significant difference(P0.0001) was detected in canopy structure and understory light during the 3 years,but between-year differences showed a tendency to decrease as the forest recovered from 2008 to 2010;3) In the first three years of forest recovery,transmitted direct solar radiation demonstrated a greater spatial-temporal fluctuation and provided a greater contribution to total solar radiation than did transmitted diffuse solar radiation;4) Canopy openness was more sensitive than leaf area index as an indicator of canopy structure change,while canopy structure had a greater influence on transmitted diffuse solar radiation than transmitted direct solar radiation.Initially,the trees in the ice storm damaged forest grew rapidly during the recovery period following the storm,but the growth slowed down gradually and stabilized.There was a gradual reduction in the understory light as the forest closed due to tree growth.Canopy openness is better for the evaluation of the dynamic effects of canopy structure.The spatial and temporal variations of transmitted direct solar radiation were more complex than transmitted diffuse solar radiation.Therefore,research to study the effects of an ice storm on canopy structure of a subtropical forest to reveal dynamics of canopy structure and understory light,and to monitor the restoration of a damaged forest ecosystem,will have significant implications for both theoretical and applied forest restoration efforts.

Spatial Heterogeneity Dynamics of Canopy Structure in a Montane Evergreen Broadleaved Forest Following a Natural Disturbance in North Guangdong

Spatial Heterogeneity Dynamics of Canopy Structure in a Montane Evergreen Broadleaved Forest Following a Natural Disturbance in North Guangdong

Identifying hotspots of endemic woody seed plant diversity in China

AbstractAim This study aimed to detect distribution patterns and identify diversity hotspots for Chinese endemic woody seed plant species (CEWSPS).Location China.Methods Presence of 6885 CEWSPS throughout China was mapped by taking the Chinese administrative county as the basic spatial analysis unit. The diversity was measured with five indices: endemic richness (ER), weighted endemism (WE), phylogenetic diversity (PD), phylogenetic endemism (PE) and biogeographically weighted evolutionary distinctiveness (BED). Three levels of area (i.e. 1, 5 and 10% of China’s total land area) were used to identify hotspots, but the 5% level was preferred when both the total area of the hotspots identified and the diversity of CEWSPS reached by the hotspots were considered.Results Distribution patterns of CEWSPS calculated with the five indices are consistent with each other over the national extent. However, the hotspots do not show a high degree of consistency among the results derived from the five indices. Those identified with ER and PD are very similar, and so are those with WE and BED. In total, 20 hotspots covering 7.9% of China’s total land area were identified, among which 11 were identified with all the five indices, including the Hengduan Mountains, Xishuangbanna Region, Hainan Island, and eight mountainous areas located in east Chongqing and west Hubei, in east Yunnan and west Guangxi, in north Guangxi, south‐east Guizhou and south‐west Hunan, in north Guangdong and south Hunan, in south‐east Tibet, and in south‐east Hubei and north‐west Jiangxi. Taiwan Island was also identified as a major hotspot with WE, PE and BED.Main conclusions Hotspots of CEWSPS were identified with five indices considering both distributional and phylogenetic information. They cover most of the key areas of biodiversity defined by previous researchers using other approaches. This further verifies the importance of these areas for China’s biodiversity conservation.

Organically geochemical characteristics of the Fankou Pb-Zn deposit in North Guangdong Province, China: Implication for Pb-Zn enrichment

The Fankou Pb-Zn deposit is a very important and famous deposit in China. The time of Pb-Zn enrichment has been debated for a long time in this deposit. A total of seventeen samples of three sections were taken from the Fankou mine for the study of mineralization time and the mechanism of ore formation. The samples were analyzed by microscope, Soxhlet-extract, GC, and GC/MS methods. The results indicated that organic bulk parameters vary with the Pb-Zn contents in different samples and clearly were influenced by ore sulfide formation. Organically geochemical parameters (MPI 1, CPI) indicate that the paleotemperatures in the Fankou deposit are lower than 80°C in all three sections. Sulfides in the wall rocks might occur mainly during synsedimentation or early diagenesis by BSR or partly by PR, rather than by TSR at such low temperatures, this stage may be the first mineralization stage. Sulfides near the faults might be formed by TSR after sedimentation, this stage may be the second mineralization stage.

Trace element immobilization by uranyl minerals in granite-hosted uranium ores: Evidences from the Xiazhuang ore field of Guangdong province, China

The oxidative alteration of uraninite and the fate of trace elements (Y, LREE, Zr, and Th) in a granite-hosted uranium ore deposit in north Guangdong province, China, were investigated to understand the geochemical behavior of spent UO2fuel and associated fission products and transuranium elements under oxidizing conditions. In light of the paragenetic relationship of the alteration products, two alteration series of uraninite were identified: one is the silicate series with a mineral paragenesis of uraninite → uranyl oxide hydrates → Si-rich uranyl phase → uranophane (Ca[(UO2)(SiO3OH)]2(H2O)5), and the other is the phosphate series with a mineral paragenesis of uraninite → uranyl oxide hydrates → autunite (Ca[(UO2)(PO4)]2(H2O)6) → yingjiangite ((K2,Ca)(UO2)7(PO4)4(OH)6(H2O)6). In contrast to the wide distribution and abundance of uranophane and the uranyl phosphate minerals, uranyl oxides were only occasionally found in the ore samples, suggesting that the uranyl silicates and phosphates should be the predominant alteration products of UO2under oxidizing conditions, although uranyl oxide hydrates would be the solubility-limiting phase of uranium in the very early stage of alteration. Furthermore, the interlayer cation of the uranyl phases in the Xiazhuang uranium ore field is dominated by Ca2+, indicating that the release of uranium and other radionuclides will be limited mainly by uranophane and autunite during the oxidative alteration of spent UO2fuel in underground repositories where enhanced calcium concentration is expected due to cement/water reactions.Compositionally, the cation atomic ratios in uranyl phases often deviate considerably from their respective stoichiometric values as indicated by the nominal formulae, but the compositional variation does not result in significant structural change as indicated by X-ray diffraction patterns. This observation indicates that the structure of U6+minerals may easily be adjusted to accommodate impurity elements including crystallographically compatible radionuclides. Compared with the primary uraninites, the secondary minerals are slightly enriched in light REE, but significantly depleted in Y3+probably due to its cation-radius mismatch with interlayer Ca2+. The apparent enrichment of Zr4+in uranophane and uranyl phosphates relative to uraninite may result from the coupled substitutions: Zr4+↔ U6+and REE3+↔ Ca2+(K+). Because an adequate charge-balance mechanism and significant distortion of the coordination polyhedra are required for the substitution An4+↔ U6+, this type of substitution may not be common.

Geochemistry of cretaceous mafic dykes in North Guangdong, China

Geochemistry of cretaceous mafic dykes in North Guangdong, China

Fractal and Multifractal Properties of Geochemical Fields

A fractal model, introduced by De Wijs to study the distribution, redistribution, or enrichment/depletion of element concentrations in a region, has become widely accepted. This paper uses it to simulate various geochemical fields for element concentration values. The frequency distribution and spatial pattern of the simulated values or “concentrations” are analyzed by the method of moments and the concentration–area (C–A) model. The spatial pattern of the original De Wijs model is shown to be intrinsically characterized by ∩-shaped and symmetrical multifractal spectrum curves, whose center and width change systematically with the enrichment factors set in the simulation. The corresponding frequency distribution pattern on the log–log plot of frequency versus concentrations is called simple continuous multifractal (SCM) by the authors. In other experiments, when a De Wijs model is locally superimposed by another De Wijs model of different enrichment factors, the symmetry of the multifractal spectrum graph is broken and a different pattern of frequency distribution is found. It is referred to as highly accumulated continuous multifractals (HACM). Concentrations of 12 elements in 1448 rock samples from Shaoguan district, North Guangdong Province, South China, and 12 oil/gas indexes in surface soils from Sangtamu region, Tarim Basin, Northwest China, have been applied. The real geochemical fields, both metallic and oil/gas, are found to be remarkably compatible to those simulated patterns of De Wijs models with backgrounds of various enrichment and different degrees of superimposition, indicating that the frequency and spatial distribution patterns revealed by the authors are most possibly universal features of geochemical fields. It is particularly interesting to note that the major geochemical indicators of oil/gas geochemical fields are closer to the results of De Wijs models with a small enrichment factor, either with or without local superimposition, whereas those of the metallic geochemical field correspond more closely to De Wijs models with a background field of larger enrichment factors. The results obtained herein potentially have important implications in mineral and oil/gas resource assessment.

Epidemiologic Survey on Kawasaki Disease in South China, 1995-1999

Objective: The objective of this paper is to describe the epidemiological and clinical characteristics of Kawasaki disease(KD) in Guangdong Province, China during 5 year-period from January 1995 to December 1999.Methods: A province-wide epidemiological survey on Kawasaki disease was made by the Sino-Japan Kawasaki Disease Study Group. The questionnaire form and the diagnostic criteria of KD were sent to the departments of pediatrics of all the hospitals of county level. All the patients diagnosed in 1995 to 1999 were required to be reported. Results: A total of 111(71.2%) hospitals responded and 537 cases of KD were confirmed. The incidence rate was 5.93 per 100,000 children < 5 Yrs. old in Guangdong province. Of total patients reported, 51.8% were younger than 2 years old and 75.6% were younger than 4 years old with male to female ratio of 2.23:1. The number of patients was higher during April to June every year and lower during October to December. Areas of the highest incidence rate were found in Shenzhen and Zhuhai and next were Guangzhou and pearl river delta, the incidence rate in the North Guangdong was the lowest. The proportion of patients with cardiac sequelae was 75 cases (14%). There were 1 fatal case with a fatality rate of 0.2%.Conclusions: The incidence rate of KD in Guangdong was higher than that in Jiangsu and Shanxi and obviously lower than that in Japan. As similar to Japan, Jiangsu and Shanxi in epidemiologic patterns and distribution feature. Areas of the highest incidence rate were found in good economic status and the incidence rate in difficult economic status was lower.

An expert system for flow routing in a river network

Flow routing in a river network is one of the most important parts in the domain of water resources and hydrology. There are different characteristics in the different river networks. The mathematical models adopted to deal with the flow routing have their own advantages respectively. Thus a suitable model should be selected to solve the problem of flow routing on a specially appointed river network. But this selection is very difficult and requires highly specialized knowledge and expertise about the models. It is not easy and not appropriate for a civil engineer to spend much time in learning how to select a suitable model and how to manipulate it. Recent developments in mathematical model of flow routing and artificial intelligence have rendered it possible to construct an expert system to help civil engineers make this kind of decision. An expert system is addressed to handle this decision-making in this paper. The way for manipulation of the selected model and whether or not the interbasin rainfall-runoff should be considered are integrated into the system too. VP-Expert is employed as the shell of this expert system. The expert system has been tested on the Changtan watershed, north Guangdong province of China.

Response of subterranean clover (Trifolium subterraneum) to lime, magnesium, and boron on acid infertile soil in subtropical China

Severe symptoms observed in clover pastures sown in north Guangdong Province, China, warranted study of the response to Mg fertilizer, and possible interactions with lime and B fertilizer. Subterranean clover (Trifolium subterraneum) was sown in a 2 × 2 × 2 factorial pot experiment with Mg, lime, and B treatments and four replications. The highly acid soil collected from Lechang Model Cattle Farm was low in exchangeable Mg (0.06 meq 100 g−1). Mg fertilizer doubled exchangeable Mg, increased Mg saturation to > 3% and raised the Mg/K ratio to > 1.0, but A1 saturation remained above 75%. Lime application doubled exchangeable Ca and reduced A1 saturation to < 1%, but did not affect exchangeable Mg or K levels.

Evolutionary characteristics of the U-Pb isotopic system in a certain uranium deposit in North Guangdong—A discussion on the model for its genesis

Based on the evolutionary theory of U-Pb isotopic system, we have studied the genetic model for a uranium deposit occurring in carbonate-silicolite-pelite. The data show that the U-deposit is characterized by a multi-stage evolution with respect to its U-Pb isotopic system, and the mechanism of its genesis can be explained by later repeated superimposition of mine-ralization which took place at about 200±10m. y., 100±10m. y., 60±10m. y. and 11±1m. y. ago. These mineralization stages are closely related to regional tectonic activities.

The Effect of Cold Weather on Success in Trapping Feral Coypus (Myocastor coypus)

By the methods of geostatistics, this paper studied the spatial pattern of Fruhstorferiola tonkinensis nymphs in mulberry fields of north Guangdong. The results showed that the semivariogram of F. tonkinensis nymphs at all development stages could be described by spherical model, implying an aggregative distribution, and the range of their spatial correlation was 1. 973, 1. 968, 2. 169, 2. 302 and 4. 307 m from 1st to 5th instars. Based on the information obtained from investigation site, the isoclines maps of the instars were created by the geostatistical software Surfer 8. 0 with Kriging interpolation, and the resulting maps gave a clear indication about the spatial patterns of the instars. Unlike other locusts, the younger instars of F. tonkinensis had an aggregative distribution, while the elder ones were dispersive in distribution.