Hydrogeology in the Nordic Countries

Hydrogeology in the Nordic Countries is characterized by many types of aquifers and great differences in groundwater recharge. Fracture aquifers in crystalline, hard rocks are the most common type of aquifer with, in general, low fracture porosity and low well yields. The most productive crystalline rocks are the basalts in Iceland and the rapakivi granite in Finland. The fracture and fault zones have mostly high conductivity. Porous aquifers are found in various types of geology. The most porous ones are the lava-fields and the pyroclastic rocks in the active volcanic zone of Iceland, but glaciofluvial deposits such as eskers and deltas in Finland, Norway and Sweden, outwash plains in SW Denmark and sandurs in Iceland are also very porous and good aquifers, as are some sedimentary rocks in Denmark. The glacial till has, in general, low conductivity. Fractured porous aquifers in consolidated limestones and sandstones have high well yields in relatively young formations in Denmark and Scania in southern Sweden, but medium or low yields in older strata. Karst aquifers have limited extension, but there are some well developed ones in the Caledonian mountain range in Norway and Sweden. Geothermal water with a lot of springs and even geysers are common in Iceland and of great economic importance. The groundwater chemistry of the crystalline, hard rocks is notable for bacteria, brines and mixed water at great depths （more than 500 m） as well as high contents of arsenic, fluoride and radon in drilled wells in certain regions.     

On Continent-Continent Point-Collision and Ultrahigh-Pressure Metamorphism

Up to now it is known that almost all ultrahigh-pressure (UHP) metamorphism of non-impact origin occurred in continent-continent collisional orogenic belt, as has been evidenced by many outcrops in the eastern hemisphere. UHP metamorphic rocks are represented by coesite- and diamond-bearing eclogites and eclogite facies metamorphic rocks formed at 650-800℃ and 2.6-3.5 GPa, and most of the protoliths of UHP rocks are volcanic-sedimentary sequences of continental crust. From these it may be deduced that deep subduction of continental crust may have occurred. However, UHP rocks are exposed on the surface or occur near the surface now, which implies that they have been exhumed from great depths. The mechanism of deep subduction of continental crust and subsequent exhumation has been a hot topic of the research on continental dynamics, but there are divergent views. The focus of the dispute is how deep continental crust is subducted so that UHP rocks can be formed and what mechanism causes it to be subducte     

贵州梵净山基性-超基性岩地质、岩石特征及类型的初步探讨

The Fanjingshan group, located in the Mt. Fanjing Region, Guizhou Province, is a flysch formation with a thickness of over 10000 meters. Intrusive basic rocks, varying in thickness, consist mainly of layered gabbrodiabase and diabase. Hornstone, spotted slate and ,albite-quartz-slate are commonly recognized in hanging and foot wall rocks as a result of contact metamorphism. Spilite with pillow structure, averaging about 100 meters in thickness, is also widespread. Ultramafic rocks have relatively limited occurrence, accounting for only 13 percent of the total thickness of the intrusives. Alpine ultrabasic rocks have not been found as separate mass. Ultramafic products resulted from in-situ differentiation are noticed and can be assigned to the iron series of ultrabasie rocks. The intrusive basic rocks are classified as subvolcanics that intruded at shallow depth. They are considered to share a common source, to have emplaced into the same position and to be contemporaneous with the sea floor volcanic-spilite, ,and in accordance with its characters, should be assigned to oohidite suit.     

Estimation of Fracture Geometry Parameters and Characterization of Rock Mass Structure for the Beishan Area, China

The accurate estimation of fracture geometry parameters and the characterization of rock mass structure are two important topics in the geological disposal system of high-level radioactive waste (HLW). The Beishan area, as the current preselected area for China''s HLW disposal, has three subareas considered to be the key survey area at the stage of site selection. In this paper, a comprehensive survey method conducted on the outcrop is developed to estimate fracture geometry parameters. Results show that fracture occurrence obeys a Fisher distribution, fracture trace length obeys a normal distribution, and the distribution of spacing obeys a negative exponential distribution. An evaluation index, Rock Mass Structure Rating (RMSR), is proposed to characterize rock mass structure for the three subareas. The results show that the Xinchang area is more suitable to act as China’s HLW disposal repository site. At the same time, the index can also be applied to characterize surface rock mass structure and rock mass integrity at the site selection phase of HLW disposal.     

Formation Conditions and Distribution Regularities of Oil—gas Pools in Tertiary Volcanic Rocks in Western Huimin Depression,Shandong Province

The formation conditions and distribution regularities of oil-gas pools in volcanic rocks in western Huimin Depression have been studied in terms of geolgic,sesmic and well logging information,This paper discusses the types and lithofacies,development and distribution of Tertiary volcanic rocks in the area.The results demonstrate that volcanic activity occurred mainly during the period from the Sha-4 stage to the Guantao episode,i.e.,before the oil-generating period(before the end of the Guantao episode and the Minghuazhen episode).The activity did not destroy oil and gas formation and accumulation,but was favourable for the concentration of organic matter and its conversion to hydrocarbons;besides,volcanic rocks can serve as reservoir rocks and cap rocks,playing a role very similar to that of a syndepositional anticline,The volcanic rocks are distributed near the margins of the oil-generating depression;there are many secondary interstices in the rocks,which are connected with each other.These are the leading conditions for the formation of oil-generating period and their self-sealing or good combination with other cap rocks are important factors for forming volcanic rock-hosted oil and gas pools.The oil-gas pools associated with volcanic rocks in western Huimin are mainly distributed around the deep oil-generating depression,in the central up lift or the high structural levels on the margins of the depression.In particular,the sites where several faults cross are usually locatons where hith-yielding oil-gas pools in volcanic rocks are concentrated.     

Acid rain in China-Input-output budgets of major ions in four forested catchments

Acid rain is one of China＇s major environmental problems and emissions of sulphur and nitrogen are still increasing. The acid rain situation in China is somewhat different from what is seen in Europe and North America. Sulfur deposition is very high, but there is also very high deposition of calcium and other base cations. The sources of atmospheric Ca are not well understood, although it is important for understanding long term impacts of acid deposition. The fate of S, N and Ca^2＋ in the catchment is crucial for the future development of the acidification situation of soils and waters in China. Very few studies presenting catchment input-output ion budgets in Chinese natural environments exist and there are several unknown factors regarding processes. Here, we present annual input-output budgets for three years （2001-2003） for major ions for four forested catchments in China receiving different loads of acid deposition. For the two sites receiving the highest SO4^2- inputs, the input-output budget for the upper 50 cm of soil is approximately balanced. For the most remote site the soil is a net sink for SO4^2-, suggesting that the pool of adsorbed SO4^2- in the soil is building up. This is in agreement with the fact that the site so far has received only moderate SO4^2- inputs. For the southemmost, the subtropical site there is a loss of SO4^2- in the soil, which at least partly may be related to high uptake from the dense and highly productive forest at the site. The Ca^2＋ budgets for the upper 50 cm of soil show large variations both within and between sites. For most locations there is production of Ca^2＋ in the soil that can be explained by weathering, and variation between years related to hydrology that can be explained by ion exchange. However, at some plots at the site receiving very high inputs of both SO4^2- and Ca^2＋, there is an unknown sink of Ca^2＋ in the soil at some plots.     

Detrital Mode and Geochemistry of the Shurijeh Formation (Late Jurassic-Early Cretaceous) in the Central and Western Parts of the Intracontinental Kopet-Dagh Basin, NE Iran: Implications for Provenance, Tectonic Setting and Weathering Processes

Petrographical and geochemical methods were combined to investigate the provenance, geodynamic and weathering history of the Shurijeh sandstones, Kopet-Dagh Basin. The point-counting method and XRF technique are used for modal and geochemical analyses. Based on petrographical examinations, it seems that the Shurijeh sandstones are mainly deposited in the craton interior and recycled orogen belts. In addition to petrographical investigation, geochemical analyses (major oxides and trace elements) of Late Jurassic-Early Cretaceous rocks reveal that the sedimentation processes are performed in a passive continental margin. Such interpretation is supported with geodynamic and paleogeographical studies of the Kopeh-Dagh basin during this time. The geochemical investigations suggested that the composition of probable source rocks mostly was acidic-intermediate with minor mafic igneous rocks. Based on the above, Paleo-Tethys remnants and their collision-related granitoids, in the south and west of Mashhad, may have been the source area for these rocks. CIA values, which range from 63.8 to 94.9 in samples, are suggesting a moderate to relatively high degree of alteration (weathering) in the source area. Therefore, petrographical and paleogeographical studies of siliciclastic rocks can be used for the provenance, tectonic setting and paleoweathering studies in the source area.     

History and Progress of the North American Soil Geochemical Landscapes Project,2001-2010

In 2007,the U.S.Geological Survey,the Geological Survey of Canada,and the Mexican Geological Survey initiated a low-density(1 site per 1600 km2,13323 sites) geochemical and mineralogical survey of North American soils(North American Soil Geochemical Landscapes Project).Sampling and analytical protocols were developed at a series of workshops in 2003-2004 and pilot studies were conducted from 2004-2007.The ideal sampling protocol at each site includes a sample from 0-5 cm depth,a composite of the soil A horizon,and a sample from the soil C horizon.The <2-mm fraction of each sample is analyzed for Al,Ca,Fe,K,Mg,Na,S,Ti,Ag,Ba,Be,Bi,Cd,Ce,Co,Cr,Cs,Cu,Ga,In,La,Li,Mn,Mo,Nb,Ni,P,Pb,Rb,Sb,Sc,Sn,Sr,Te,Th,Tl,U,V,W,Y,and Zn by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry following a near-total digestion in a mixture of HCl,HNO3,HClO4,and HF.Separate methods are used for As,Hg,Se,and total C on this same size fraction.The major mineralogical components are determined by a quantitative X-ray diffraction method.Sampling in the conterminous U.S.was completed in 2010(c.4800 sites) with chemical and mineralogical analysis currently underway.In Mexico,approximately 66% of the sampling(871 sites) had been done by the end of 2010 with completion expected in 2012.After completing sampling in the Maritime provinces and portions of other provinces(472 sites,7.6% of the total),Canada withdrew from the project in 2010.Preliminary results for a swath from the central U.S.to Florida clearly show the effects of soil parent material and climate on the chemical and mineralogical composition of soils.A sample archive will be established and made available for future investigations.     

GEOCHEMISTRY AND TECTONIC ENVIRONMENT AND RESERVOIR FORMATION OF MANTLE-DERIVED NATURAL GAS IN THE SONGLIAO BASIN, NORTHEASTERN CHINA

During several decades of exploration, a number of mantle-derived natural gas pools have been discovered in the vicinities of deep faults in the Songliao Basin, northeastern China. The natural gas in these pools has a δ 13C1 value of-16.5‰ to -24.2‰, a reversed arrangement in the amount of carbon isotopes in methane and its endogamous products (namely, Δ13c1 ＞Δ13c2 ＞Δ13c3 ＞Δ13c4 ), a 3He/4He value of 1.97 to 2.34× 10-6, and an 40Ar/36Ar value of 1063 to 1949. This indicates a mantle source for the natural gas. The trace elements Cd, In, Te and Re, never found in organic-sourced hydrocarbons, are highly enriched in certain crude oils from the Basin; respectively, concentrations of these elements were found to be 751, 28, 16 and 323 times the average crustal values in China, and this also supports a mantle-derived natural gas origin. The characteristics of mantled-derived magmatic rocks,hydrothermal fluids and gaseous fractions distributed in and near the deep Songliao Basin faults indicate that rifting tectonics is providing the mechanisms for this outgassing of the mantle. Deep extensional(normal) faults provide pathways for upward movement of these materials, and in the Songliao Basin,these deep riff fault zones are associated with reservoir occurrence and cap rock seals, forming good sites for accumulation of mantle-derived natural gas. Furthermore, a layer of low velocity, low density and high conductivity in the deep crust has been identified as a potential reservoir for mantle-derived natural gas.     

青藏公路边坡防护试验研究

The results brought out in the trials of slope protection along Qinghai-Tibet Highway are presented in this paper. The trials were carried out simultaneously at 5 sites in Qinghai-Tibet Plateau from 2000 to 2002. Altitudes at the experimental sites range between 4 240 m and 5 040 m. 4 sites are in permafrost area, and 1 site is in seasonally frozen ground. According to the trials of slope protection, vegetation is preferred to protect slopes along Qinghai-Tibet Highway. Road-GoodR, a chemical stabilizer, is proved as a good material for slope protection, and soil engineering system, combined with vegetative component and grade stabilization structures is proved as the best slope protection measure in these are as. The results showed that high-altitude areas at an altitude lower than 5 040 m, annual average temperatures higher than -5.6 ℃ and annual rainfall more than 262.2 mm, slopes can be protected using vegetative components.Trials for plant species selection proved that cold resistant grasses, Elymus nutans and Elymus sibiricus can be used for vegetation recovery along Qinghai-Tibet Highway. The results demonstrated that high-altitude areas at an altitude lower than 5 040 m, annual average temperatures higher than -5.6 ℃ and annual rainfall more than 262.2 mm, could be replanted. Hydroseeding proved to be a good planting technique, and mulch materials benefited vegetation recovery in such area.The experiment also proved that planting could improve slope stability, protect the ecological environment, and improve the roadside landscape.     

Improved reliability in the interpretation of geochemical measurements by the quantification of uncertainty from sampling

All geochemical measurements require the taking of field samples, but the uncertainty that this process causes is often ignored when assessing the reliability of the interpretation, of the geochemistry or the health implications. Recently devised methods for the estimation, optimisation and reduction of this uncertainty have been evaluated by their application to the investigation of contaminated land. Uncertainty of measurement caused by primary sampling has been estimated for a range of six different contaminated land site investigations, using an increasingly recognized procedure. These site investigations were selected to reflect a wide range of different sizes, contaminants （organic and metals）, previous land uses （e.g. tin mining, railway sidings and gas works）, intended future use （housing to nature reserves） and routinely applied sampling methods. The results showed that the uncertainty on measurements was substantial, ranging from 25% to 186% of the concentration values at the different sites. Sampling was identified as the dominant source of the uncertainty （〉70% of measurement uncertainty） in most cases. The fitness-for-purpose of the measurements was judged using the optimized contaminated land investigation （OCLI） method. This identifies the optimal level of uncertainty that reduces to overall financial loss caused by the measurement procedures and the misclassification of the contamination, caused by the uncertainty. Generally the uncertainty of the actual measurements made in these different site investigations was found to be sub-optimal, and too large by a factor of approximately two. The uncertainty is usually limited by the sampling, but this can be reduced by increasing the sample mass by a factor of 4 （predicted by sampling theory）. It is concluded that knowing the value of the uncertainty enables the interpretation to be made more reliable, and that sampling is the main factor limiting most investigations. This new approach quantifies this problem for the first time, and allows sampling procedures to be critically evaluated, and modified, to improve the reliability of the geochemical assessment.     

Formation blockage risk analysis of geothermal water reinjection:Rock property analysis,pumping and reinjection tests,and long-term reinjection prediction

The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new drilled geothermal well in Xining basin China is taken as an example to investigate the formation blockage risk due to the movable clay and sand particles in pores.The physical properties of the reservoir rocks were analyzed,a series of pumping and reinjection tests were conducted,and the longterm reinjection performance of the well was predicted by numerical simulation based on the test fitting.The results show that the geothermal reservoir rocks are argillaceous and weakly cemented sandstones with a content of movable clay and sand particles up to 0.18–23.42 wt.%.The well presented a high productivity of 935–2186 m3?d-1 at a pressure difference of 0.7–1.62 MPa in the pumping tests associated with a large amount of clay and sand particles produced out,while in the reinjection test,only a low injectivity of 240–480 m3?d-1 was observed at an injection pressure of 0.2–0.6 MPa with the clay and sand particles near the wellbore move into deep.According to the prediction,under conditions of a blockage risk,the injectivity of the well will start to decline after 100 days of injection,and in the third year,it will decrease by 59.00%–77.09%.The influence of invasion of pretreated suspended particles and scale particles can be neglected.Under conditions of a high blockage risk,the injectivity of the well will decrease significantly in the first 20–30 days,with a decline of 75.39%–78.96%.Generally,the higher the injection pressure or rate,the greater the decrease in injectivity of the well caused by particle blockage.Pump lifting is an effective measure to remove the well blockage which can be used regularly.     

岩石化学系列和元素演化周期性

Continental crust rocks can be grouped into three petrochemical, systems, i.e.,oxygen-poor, transitional, and oxygen-rich system, which are intimately related to the intensity of crustal movement. Stable areas in the crust are characterized by rocks of oxygen-poor system, while rocks of oxygen-rich system are typical of active regions.Rocks of the transitional system form all gradations between the two systems Parallel to the orogenic cycle in crustal movement an evolutionary cycle from low to high oxygen content can always be recognized with respect to rocks in each system. On the other hand, with regard to rocks of the same type in the same petrochemical system, apart from the influence of crustal movement intensity, a tendency of increasing oxygen content with decreasing orogenic age is noticeable. As a region changes from active into gradational geologically, oxygen content is found decreasing for rocks of the same type,or vice versa. In this context, new implications may be attached to studies on petrochemical system : (1) A“family tree” can be established for rocks, thus sheding light on their evolutionary hlstoryand geneses (2)To provide information on the intensity of crustal movement, i.e., the tectonic nature for the studied area at the time of magma generation, and (3) To aid in determining petrogenetie age of magmatic rocks and in making geological divisions.     

碳酸盐岩生油岩的有机地球化学、岩石学特征

Features of oil-generating carbonate rocks are studied in terms of petrology and organic geochemistry of fluorescent materials in rocks. It is postulated by the authors that the organic carbon content in oil-generatlng carbonate rocks is necessarily lower than that in shales, and the possible cause of this observation is discussed. The quality of oil-ganerating carbonate rocks may be judged by aromatic structure index,amino acid, pigment index, and DTA data on organic matter. However, the application of presently available organic geochemical criteria to non-oil-generating reservoir rocks may always give misleading results. To circumvent this difficulty, it is necessary first to make distinction between primary and secondary organic matter by cxamining the fluorescent materials under a fluorescence microscope. Measurementof radical content of the organic substances and DTA are useful techniques to determine the degree of maturation. The maturation of organic substances proceeds at a lower rate in carbonate rocks than in shales. It is likely, therefore, that some older carbonate strata can also be promising areas for petroleum exploration. Oil-generating carbonate rocks consist mainly of mierite limestones rich in organic matter and are thought to be formed under low-encrgy environment. Consequently, petrological(especially mierolithofacies) studies are very important in evaluating carbonate source rocks.     

Dynamic Field Division of Hydrocarbon Migration,Accumulation and Hydrocarbon Enrichment Rules in Sedimentary Basins

Hydrocarbon distribution rules in the deep and shallow parts of sedimentary basins are considerably different, particularly in the following four aspects. First, the critical porosity for hydrocarbon migration is much lower in the deep parts of basins: at a depth of 7000 m, hydrocarbons can accumulate only in rocks with porosity less than 5%. However, in the shallow parts of basins (i.e., depths of around 1000 m), hydrocarbon can accumulate in rocks only when porosity is over 20%. Second, hydrocarbon reservoirs tend to exhibit negative pressures after hydrocarbon accumulation at depth, with a pressure coefficient less than 0.7. However, hydrocarbon reservoirs at shallow depths tend to exhibit high pressure after hydrocarbon accumulation. Third, deep reservoirs tend to exhibit characteristics of oil (–gas)–water inversion, indicating that the oil (gas) accumulated under the water. However, the oil (gas) tends to accumulate over water in shallow reservoirs. Fourth, continuous unconventional tight hydrocarbon reservoirs are distributed widely in deep reservoirs, where the buoyancy force is not the primary dynamic force and the caprock is not involved during the process of hydrocarbon accumulation. Conversely, the majority of hydrocarbons in shallow regions accumulate in traps with complex structures. The results of this study indicate that two dynamic boundary conditions are primarily responsible for the above phenomena: a lower limit to the buoyancy force and the lower limit of hydrocarbon accumulation overall, corresponding to about 10%–12% porosity and irreducible water saturation of 100%, respectively.     

Campaign-style U-Pb titanite petrochronology:Along-strike variations in timing of metamorphism in the Himalayan metamorphic core

Present-day along-strike heterogeneities within the Himalayan orogen are seen at many scales, from variations within the deep architecture of the lithospheric mantle, to differences in geomorphologic surface processes. Here, we present an internally consistent petrochronologic dataset from the Himalayan metamorphic core(HMC), in order to document and investigate the causes of along-strike variations in its Oligocene-Miocene tectonic history. Laser ablation split-stream analysis was used to date and characterise the geochemistry of titanite from 47 calc-silicate rocks across >2000 km along the Himalaya.This combined U-Pb-REE-Zr single mineral dataset circumvents uncertainties associated with interpretations based on data compilations from different studies, mineral systems and laboratories, and allows for direct along-strike comparisons in the timing of metamorphic processes. Titanite dates range from ～30 Ma to 12 Ma, recording(re-)crystallization between 625 ℃ and 815 ℃. Titanite T-t data overlap with previously published P-T-t paths from interleaved peltic rocks, demonstrating the usefulness of titanite petrochronology for recording the metamorphic history in lithologies not traditionally used for thermobarometry. Overall, the data indicate a broad eastward-younging trend along the orogen.Disparities in the duration and timing of metamorphism within the HMC are best explained by alongstrike variations in the position of ramps on the basal detachment controlling a two-stage process of preferential ductile accretion at depth followed by the formation of later upper-crust brittle duplexes.These processes, coupled with variable erosion, resulted in the asymmetric exhumation of a younger,thicker crystalline core in the eastern Himalaya.     

Low-Temperature Plasticity of Naturally Deformed Calcite Rocks

Optical, cathodoluminescence and transmission electron microscope (TEM) analyses were conducted on four groups of calcite fault rocks, a cataclastic limestone, cataclastic coarse-grained marbles from two fault zones, and a fractured mylonite. These fault rocks show similar microstructural characteristics and give clues to similar processes of rock deformation. They are characterized by the structural contrast between macroscopic cataclastic (brittle) and microscopic mylonitic (ductile) microstructures. Intragranular deformation microstructures (i.e. deformation twins, kink bands and microfractures) are well preserved in the deformed grains in clasts or in primary rocks. The matrix materials are of extremely fine grains with diffusive features. Dislocation microstructures for co-existing brittle deformation and crystalline plasticity were revealed using TEM. Tangled dislocations are often preserved at the cores of highly deformed clasts, while dislocation walls form in the transitions to the fine-grained     

Measurement and Analysis of Thermal Conductivity of Rocks in the Tarim Basin, Northwest China

: As a parameter that describes heat transmission properties of rocks, thermal conductivity is indispensable for studying the thermal regime of sedimentary basins, and retrieving high-quality data of thermal conductivity is the basis for geothermal related studies. The optical scanning method is used here to measure the thermal conductivity of 745 drill-core samples from the Tarim basin, the largest intermontane basin with abundant hydrocarbon potential in China, and water saturation correction is made for clastic rock samples that are of variable porosity. All the measured values, combined with previously published data in this area, are integrated to discuss the distribution characteristics and major controlling factors that affect the thermal conductivity of rocks in the basin. Our results show that the values of thermal conductivity of rocks generally range from 1.500 to 3.000 W/m·K with a mean of 2.304 W/m·K. Thermal conductivity differs considerably between lithological types: the value of a coal sample is found to be the lowest as being only 0.249 W/m·K, while the values for salt rock samples are the highest with a mean of 4.620 W/m·K. Additionally, it is also found that the thermal conductivity of the same or similar lithologic types shows considerable differences, suggesting that thermal conductivity cannot be used for distinguishing the rock types. The thermal conductivity values of mudstone and sandstone generally increase with increasing burial depth and geological age of the formation, reflecting the effect of porosity of rocks on thermal conductivity. In general, the mineral composition, fabric and porosity of rocks are the main factors that affect the thermal conductivity. The research also reveals that the obvious contrast in thermal conductivity of coal and salt rock with other common sedimentary rocks can induce subsurface temperature anomalies in the overlying and underlying formations, which can modify the thermal evolution and maturity of the source rocks concerned. This finding is very important for oil and gas resources assessment and exploration and needs further study in detail. The results reported here are representative of the latest and most complete dataset of thermal conductivity of rocks in the Tarim basin, and will provide a solid foundation for geothermal studies in future.     

Petrological and Mineralogical Study of Enclaves in Plutons in the Typical Mining Districts of Tongling,Anhui and Its Bearing on the Process of Magmatism—Metallogeny

Two types of enclaves occur in magmatic plutons in Tongling,Anhui.Enclaves of the first type are residuals of metamorphic rocks of high amphibolite facies,and those of the other type are magmatic rocks ranging from monzonitic to dioritic in composition. A combined petrological and mineralogical study has been carried out on the two types of enclaves in order to estimate their forming conditions and analyze their relations to their hosts.so as to have an insight into the material sources of magmatic rocks and associated mineral deposits and give a clue to better understanding the mechanism of magmatism-metallogeny.This leads us to propose a new metallogenic model for strats-bound skarn-type ore deposits associated with a syntectic type of magmatic rocks.The new model can be simply summarized as partial melting of old metamorphic basement rocks at depth and accumulating,differentiating and positioning of magmas to form deep-level and shallow-level magma chambers,follower by mixing of different magmas associated with their crypto-explosion,migration of gas-bearing ore fluids and precipitation of metals in fluids within the magmas.     

Heavy metal content in untreated forest soils in Southwest China

The rapid industrial development in China has caused a range of environmental problems. Along with emissions of ＂conventional＂ air pollutants, such as sulfur and nitrogen oxides, there are also increasing emissions of heavy metals to the atmosphere. Little information is available on metal contamination due to atmospheric deposition in forest soils in China. In order to get an overview of the extent of the problem, we conducted analyses of metal content in soil samples from three forested research catchments in Southwest China [Tieshanping （TSP） in Chongqing, Liuchongguan （LCG） and Leigongshan （LGS） in Guizhou]. Total concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, Sn and Zn were determined by Inductively Coupled Plasma-Mass Spectrometry after microwave digestion. The Hg content was determined using a Direct Mercury Analyzer. The concentrations of most of the analyzed metals were below the National Grade A standard limits in China for most samples, except for Cd and Pb where the limits were slightly exceeded at some of the sampling sites. In general, there were small differences between the different sites, although Cd and Co show a tendency to be higher at the most remote site （Leigongshan）. This site receives the lowest deposition of conventional air pollutants among the sites and the higher metals concentrations are possibly related to higher content in the soil parent material. There is no apparent general gradient in metal concentrations with proximity to cities, major air pollution emission sources, nor with sulphur deposition loads.