Underplating of Mesozoic Mantle-derived Magmas in Tongling, Anhui Province: Evidence from Megacrysts and Xenoliths

Lithological observations and mineralogical analyses on pyroxene and hornblende megacrysts and pyroxene and hornblende cumulates in xenoliths in the Mesozoic plutons of the Tongling region, Anhui Province, provide evidence for the magmatic underplating of mantle-derived alkali-olivine basalt at circa 140 Ma. The pyroxene and hornblende megacrysts and cumulates were formed through the AFC process at depths ranging from 27 to 35 km.

Genetic Types and Metallogenic Model for the Polymetallic Copper–Gold Deposits in the Tongling Ore District, Anhui Province, Eastern China

The Tongling ore district is one of the most economically important ore areas in the Middle–Lower Yangtze River Metallogenic Belt, eastern China. It contains hundreds of polymetallic copper–gold deposits and occurrences. Those deposits are mainly clustered(from west to east) within the Tongguanshan, Shizishan, Xinqiao, Fenghuangshan, and Shatanjiao orefields. Until recently, the majority of these deposits were thought to be skarn-or porphyry–skarn-type deposits; however there have been recent discoveries of numerous vein-type Au, Ag, and Pb-Zn deposits that do not fall into either of these categories. This indicates that there is some uncertainty over this classification. Here, we present the results of several systematic geological studies of representative deposits in the Tongling ore district. From investigation of the ore-controlling structures, lithology of the host rock, mineral assemblages, and the characteristics of the mineralization and alteration within these deposits, three genetic types of deposits(skarn-, porphyry-, and vein-type deposits) have been identified. The spatial and temporal relationships between the orebodies and Yanshanian intrusions combined with the sources of the ore-forming fluids and metals, as well as the geodynamic setting of this ore district, indicate that all three deposit types are genetically related each other and constitute a magmatic–hydrothermal system. This study outlines a model that relates the polymetallic copper–gold porphyry-, skarn-, and vein-type deposits within the Tongling ore district. This model provides a theoretical basis to guide exploration for deep-seated and concealed porphyry-type Cu(–Mo, –Au) deposits as well as shallow vein-type Au, Ag, and Pb–Zn deposits in this area and elsewhere.

Study of the Emplacement Mechanism of the Fenghuangshan Granite Pluton and Related Cu-Au Mineralization in Tongling, Anhui Province

The Fenghuangshan Pluton is located in the Tongling polymineral-cluster district in the middle-lower section of the Yangtze metallogenic belt. In tectonic terms, it is in the middle of the Guichi-Fanchang faulted fold bundle of the lower Yangtze Platform fold belt between the Dabie Orogenic Belt and the Jiangnan Massif. Analyses of the structural deformation characteristics of both the contact zone and the interior of the pluton are used to explain its emplacement mechanism. The foliation and lineation of the pluton, consisting of the oriented distribution of dark minerals and xenoliths, mainly concentrate along the margin of the pluton. Toward the center of the pluton, the foliation structure becomes weak, showing intense compression formation at the margin, and reflecting the conformable intrusion of the pluton. The relatively gentle lineation is evidence of a rotatory emplacement mechanism. Relatively steep marginal foliation reflects compression expanding. Affected by the thermal power of the pluton, the metamorphism of the contact zone has zonation. Both the strike of the axial plane of fold at the contact zone and that of the flow cleavage of the ductile shear zone are consistent with the boundary of the pluton, which reflects the speciality of conformable intrusion. The hinges of the folds are mostly inclined and erect, reflecting both the rotation of the pluton and its upward spiraling emplacement mechanism. Boudins developed in both the contact zone and the steep strata indicate the emplacement characteristic of the ballon expanding. The surrounding rock of the contact zone shortens horizontally. The average percentage of shortening is 39.7%, which further proves the mechanism of the pluton expanding, and the space occupied by the active expanding intrusion was provided by the shortening of the surrounding rock. The left-lateral shear shown by the ductile shear zone and the rheomorphic fold reveals that the pluton emplacement and the deformation of surrounding rock are controlled by a NNE-striking left-lateral shear stress field. These characteristics of pluton structures provide a mechanism of emplacement. In the deep, the pluton apirally rose left lateral, and in the shallow, the one forcefully emplaced balloningly.

Discovery of Pyrrhotite-Chalcopyrite Bearing Amphibole Megacrysts in Tongling Area, Anhui Province

Some pyrrhotite-chalcopyrite-bearing amphibole megacrysts (including pyroxene megacrysts) were discovered in Mesozoic augite diorite-porphyrite at Caoshan in Tongling area, Anhui Province. The amphibole megacrysts,belonging mainly to pargasite and magnesiohastingsite, are characteristic of the amphibole composition derived from mantle and crystallized in lower crust. In general, the aggregates of pyrrhotite-chalcopyrite take the shapes of cylinder and sphere. Three occurrences have been recognized in the amphibole megacrysts: parallel linear, bunchy and scattered. The unique cylinder-like shape of the aggregates and remarkable Ni-poor sulfides in Caoshan are distinctively different from the spherical Ni-rich sulfides in pyroxene megacrysts and any other kinds of megacrysts. In terms of composition, the amphibole megacrysts and their sulfides in Caoshan are similar to those in the pyroxenite xenoliths in Qilin, Guangdong Province. In terms of origin, the pyrrhotite-chalcopyrites as exsolution products resulted from the subsolidus re-equilibration of sulfide solid solution within amphibole megacrysts. Such pyrrhotite-chalcopyrite-bearing amphibole megacrysts were first discovered inside and outside China. This discovery is important for the study of regional magma evolution and its associated mineralizations and ore sources as well.

Lead Isotope Studies of Massive Surphur-Iron-Gold Deposits in the Tongling Area, Anhui Province

Pb isotope ratios and their variation have been measured and explained on ores of massive S-Fe-Au depos-its hosted in the Middle-Upper Carboniferous, on feldspars from diorite bodies closely related tomineralization and on whole rocks from ore-hosting strata (carbonate rocks) in the Tongling area, Anhui Prov-ince. Through a comparison of Pb isotope features of these geological bodies, it has been suggested that oresubstances of the deposits were derived from ore-hosting strata. In the meanwhile, the measurement of ore Pbisotopes of different mineralization types of the same deposit indicates that different mineralization types havedistinct Pb isotope characteristics, showing the potentiality of the Pb isotopic method used in mineral explora-tion.

Geology, Geochemistry, and Geochronology of the Fenghuangshan Skarn-type Copper Deposit in the Tongling Ore Cluster, Anhui Province, East China

The Fenghuangshan skarn-type Cu deposit, Tongling Ore Cluster, Anhui Province, is an important component in the Middle-Lower Yangtze River ore-forming belt. To better understand magmatism and its relationship to mineralization, we investigated geochemical features, ore-forming fluids, and geochronology of the Xinwuli intrusion and the related Fenghuangshan Cu deposit. Lithogeochemical characteristics show that the Xinwuli quartz monzodiorite is formed by mixing magma derived from upper mantle alkaline basalt that has been contaminated by crust materials. C, H and O isotopes indicate that ore-forming fluids mainly come from the magma, with minor amounts of meteoric fluids involved at the late stage. S and Pb isotopic components indicate that ore-forming materials are derived from the mantle. Molybdenite Re-Os isotopic dating yields Re-Os model ages ranging from 139.1±2.4 Ma to 142.0±2.2 Ma, with an isochronal age of 141.1±1.4 Ma, which is consistent with sensitive, high-resolution ion microprobe （SHRIMP） zircon U-Pb ages of quartz monzodiorite and granodiorite in the mining area. Dating analysis yields ages from 136.0±2.0 Ma to 143.0±2.4 Ma for the quartz monzodiorite （a weighted average of 139.4±1.2 Ma） and ages from 136.7±2.0 Ma to 145.3±2.4 Ma for granodiorite （a weighted average of 141.0±1.1 Ma）.

Multifractal Analysis of Element Distribution in Skarn-type Deposits in the Shizishan Orefield,Tongling Area,Anhui Province,China

A series of element concentrations sampled from four drill cores with a length about 1000 m into different skarn-type deposits were selected from the Shizishan orefield, central Tongling, southeastern part of Anhui Province. Using the multifractal method, the distribution and migration characteristics of the major and trace elements are analyzed. The multifractal spectrum of the major elements is left-skewed, whereas the spectrum of the trace elements is right-skewed, which shows that in the process of skarn formation, the trace elements were enriched only locally, and major elements transported within a much larger range. The correlation coefficients of the multifractal parameters Aa （width of the multifractal spectrum） of the four drill cores are relatively low, but the correlation coefficients of the multifractal parameters R （spectrum symmetry parameter） and Af are relatively higher, indicating that although the non-homogeneous intensity of the distribution of elements is inconsistent, their spatial accumulation patterns are almost the same during the ore-forming process. The statistics of the mnltifractal parameters of various elements in the different locations show that the ore-forming processes and element migration pattern in the Shizishan orefield are consistent, and that the migrations of trace elements and major elements exhibit some differences.

Contrast in Fluid M etallogeny between the Tianmashan Au-S Deposit and the Datuanshan Cu Deposit in Tongling,Anhui Province

A comprehensive contrast of ore-forming geological background and ore-forming fluid features, especially fluid ore-forming processes, has been performed between the Tianmashan and the Datuanshan ore deposits in Tongling, Anhui Province. The major reasons for the formation of the stratabound skarn Au-S ore deposit in Tianmashan and the stratabound skarn Cu ore deposit in Datuanshan are analyzed in accordance with this contrast. The magmatic pluton in Tianmashan is rich in Au and poor in Cu, but that in Datuanshan is rich in Cu and Au. The wallrock strata in Tianmashan contain Au-bearing pyrite layers with some organic substance but those in Datuanshan contain no such layers. Moreover, the ore-forming fluids in Tianmashan are dominantly magmatic ones at the oxide and sulfide stages, but those with high content of Cu in Datuanshan are mainly groundwater fluids. In addition, differences in compositional evolution and physicochemical condition variation of the ore-forming fluids result in gradual dispersion

Spatio-temporal Variations of Evapotranspiration in Anhui Province Based on MOD16 Products

Based on the MOD16 remote sensing product provided by NASA, the temporal and spatial distribution characteristics of evapotranspiration in Anhui Province from 2000 to 2014 were analyzed statistically with the support of ENVI remote sensing image processing system and ARCGIS .geographic information system. The results showed that： （1） The annual average ET in Anhui Province was 694.9 mm from 2000 to 2014, less than half of PET, indicating that Anhui Province as a whole was in dry climate and water shortage, particularly significant in 2011-2014, with the maximum value of 730.6 mm occurring in 2003, and the minimum value of 647.6 mm occurring in 2011. The monthly average ET and PET showed a single peak distribution pattern, ET peak appearing in August, and PET peak appearing in May. （2） Linear regression analysis of ET and PET showed that there was a signif- icant decrease trend in ET in Anhui Province from October to March of the following year, and in addition, there was also a decreasing trend in the summer from June to July, but PET for the whole year demonstrated an increasing trend. The change trends of both illustrated that drought in Anhui Province was becoming more and more serious. （3） The spatial distribution of ET and PET showed that Anhui Province had obvious characteristics of high in south and low in north, and the north had large yearly and monthly changes, while the south had relatively stable changes. （4） The evapotranspiration of different land use types showed different an- nual and monthly variation characteristics, and the overall expression of annual evapotranspiration was in the order of forest 〉 grassland 〉 farmland. In terms of the monthly change, monthly evapotranspiration was manifested as winter grassland larger than the forest, forest evapotranspiration gradually exceeding the grass, and the evapotranspiration gap among the three widening continuously until the peak appearing in July or August. Due to the seasonality of crop plantation and under the common action of temperature, precipitation and other sensitive factors, the monthly evapotranspiration of forest and grassland was of single peak distribution with the maximum appearing in July, and the monthly evapotranspiration of farmland showed double peak distribution, appearing respectively in May and August, the former being weaker than the latter in strength

SHRIMP U-Pb Zircon Geochronology of the Xiaotongguanshan and Shatanjiao Intrusions and Its Petrological Implications in the Tongling Area, Anhui

This paper determines the crystallization ages of the Xiaotongguanshan quartz monzodiorite and Shatanjiao quartz monzonitc porphyry from the Tongling area using the SHRIMP zircon U-Pb method. The crystallization age of the former is 142.8±1.8 Ma; that of the latter is 151.8±2.6 Ma. These data indicate that they were formed during the Late Jurassic （142.8 to 151.8 Ma）. Zoned magma chamber was formed because of double diffusive convection. Therefore, the intrusive sequence of magma is generally from quartz monzonite through quartz monzodiorite to pyroxene monzodiorite, i.e. an inverted sequence.

Risk Assessment of Hail Disaster on Cotton——A Case Study in Anhui Province

[Objective] The aim was to reveal the pattern of hail disaster risk for cotton in Anhui Province. [Method] Based on database of risk evaluation on hail disaster for cotton in Anhui Province, statistical inference and comprehensive indices measurement were made use of for extraction of disastrous index of hail （H） and loss rate of cotton （L）. Hail vulnerability curves in four stages （seedling, bud, boll and boll opening stages） of cotton were fitted by Matlab and SPSS software. Risk evaluation on hail disaster of cotton in Anhui Province was conducted and the related map was drawn on basis of yearly model of loss rate （by hail disaster）, as follows： Sa=n∑i=1Si-a∏i=1Si=1-（1-Si） [Result] In Anhui Province, high risk area by hail concentrates in northeast regions and mountainous regions in west of Anhui, and lower risk area is distributed in middle and down streams of Yangtze River and mountainous area in south of Anhui. [Conclusion] The research explored evaluation methods on hail risks based on the limited information, and could provide references for risk evaluation on hail disaster in other regions.

Hamatophyton from the Late Devonian of Anhui Province,South China and Evolution of Sphenophyllales

Well-preserved specimens of Hamatophyton verticillatum collected from the Upper Devonian （Famennian） Wutong Formation of Chaohu district, Anhui Province, South China, display more complete fertile axes in three orders and multiple divisions. Comparisons indicate that Hamatophyton possibly does not have palmate planate sterile leaves but hook-like linear ones with rare divisions. We propose seven definitive characters of Sphenophyllales： （1） completely whorled lateral organs; （2） sterile leaves; （3） strobili; （4） ＂sporangiophores＂ or stalks with reflexed tips bearing sporangia; （5） three- or four-ribbed primary xylem; （6） exarch maturation of primary xylem; and （7） secondary xylem. The Sphenophyllales probably originated from the Iridopteridales based on similarities in whorled lateral organs, ribbed primary xylem and peripheral protoxylem strands. In transition from Iridopteridales to Sphenophyllales, morphological changes involve partially whorled to completely whorled lateral organs, sterile ultimate appendages to leaves, and fertile ultimate appendages to ＂sporangiophores＂/stalks with bracts; anatomical modifications include configuration and maturation of primary xylem, and presence of secondary xylem.

The Analysis on the Temporal and Spatial Variation of Strong Precipitation Caused Flood and Agricultural Disaster Loss in Huaihe River Basin of Anhui Province during Meiyu Period of 2007

[Objective] The research aimed to analyze temporal and spatial variation of strong precipitation caused flood and agricultural disaster loss in Huaihe River basin of Anhui Province during Meiyu period of 2007.[Method] On the basis of rainfalls of each station in Huaihe River basin of Anhui,rainfall data during Meiyu period of 2007 and flood disaster data in the same period,the temporal and spatial distribution characteristics of strong precipitation caused flood during Meiyu period of 2007 and its harm on agriculture were analyzed.The variation rule,distribution characteristics of strong precipitation during Meiyu period in Huaihe River basin of Anhui and its relationship with agricultural disaster loss were discussed.[Result] During Meiyu period of 2007 in Huaihe River basin of Anhui,the rainstorm was more,and the rainfall was large.The precipitation variation showed 'three-peak' trend.Rainfall in Huaihe River basin during Meiyu period of 2007 was greatly more than that homochronously in Yangtze River basin.The rain area over 400.0 mm during Meiyu period mainly located in Huaihe River basin,and the rain area over 600.0 mm mainly located from area along Huaihe River to central Huaibei.The rainfall during Meiyu period gradually decreased toward south and north by the north bank of Huaihe River as the symmetry axis.The rainfall in area along Huaihe River showed wavy distribution in east-west direction.The flood disaster loss index and disaster area of crops in Huaihe River basin of Anhui both increased as rainfall in Meiyu period.[Conclusion] The research provided theoretical basis for flood prevention,disaster reduction and agricultural flood-avoiding development in Huaihe River basin.

Classification and Development Laws of Karst Landform in Suzhou Area, North Anhui Province of China

Suzhou area in north Anhui Province is a low hilly area on the Huaibei Plain where carbonate rocks and karstification are widely distributed, and karst landscapes form major physical contours of the bedrock outcrops. Through field investigation, karst landscapes of Suzhou area were divided into two categories based on their morphological characteristics: macro-geomorphologic landscapes including normal hills, dry valleys, karst springs and caves, and micro-corrosion landscapes including corrosion pits, dissolved pores, dissolution traces, corrosion cracks, clints and karrens. Distribution, development and scale of karst landscapes in this region are controlled by climate, rock type, structure, topography and other factors. It was suggested that karst landscapes in the study area could be used as a representative of karst landforms in North China.

Study on Tourism Development in Inferior Tourism Regions of Anhui Province

This study aims to summarize the characteristics of 3 types of inferior tourism regions,so as to contribute to the local tourism development and provide references for the tourism development of other inferior tourism regions.With Anhui Province as an example,this study classifies different types of inferior tourism regions,and figures out the definite counties (cities) to assess their richness of tourism resources and regional development levels by utilizing SPSS and fully analyzing the data after calculating the economic development levels of these counties (cities).For I-class inferior tourism regions,regional cooperation model and brand management model should be adopted to improve their competitiveness,for II-class inferior tourism regions,poverty alleviation model should be adopted and moderate development strategy for III-class inferior tourism regions.

VARIATION IN FLOW AND SEDIMENT OF DASHA RIVER AND INFLUENCE OF HUMAN ACTIVITIES ON IT IN SOUTHWEST REGION OF ANHUI PROVINCE

Soil and water loss is now a major environmental problem in many areas of China, especially in the area of the Dabie Mountain, Anhui Province, which results in environmental degradation and does harm to the people＇s life and production there. Based on the observational records from the Dasha River, the authors analyze the character of the variation in flow and sediment in different flood and dry seasons from 1970 to 2000. The result shows that human activities had significantly reduced the sediment discharge and sediment module, and increased the runoff in low-water seasons since the 1980s. The average contribution rate ofhnman activities to decreasing sediment was 65.67%, and at the same period the contribution rate of runoff and rainfall was about 34.33%. Therefore, it is necessary to take the biological and engineering measures to solve the problem of soil and water loss in the Dasha River watershed.

A Study of Chondrules in the Boxian Meteorite from Anhui Province, China

The types of chondrules in the Boxian meteorite have been determined Electron microprobe nalvsis ofvarious textural types of chondrules in the meteorite has revealed the composition ofglassy chondrules and oftheir glassy matrix,Also presented in this paper are the related explanations.In addition.the genesis,texturaldiversity and evolution of the chondrules as well as the olivine girdles observed in the chondrules arediscussed.