Discovery and Significance of Quaternary Glacial Vestiges in the Hexigten Area of the Southern Da Hinggan Mountains, Inner Mongolia

The question whether there have been Quaternary glaciations in the Da Hinggan area has puzzled glacial geologists for many years because no sufficient glacial evidence has been found in this area. The study of Quaternary glaciers in the Da Hinggan area is also a key issue of the glaciology in China because of the special location of this area. In the past two years, a large number of complete and typical glacial vestiges have been found in Hexigten in the southern Da Hinggan Mountains, such as fossil cirque groups, horns, knife-edge crests, terminal moraines, glacial stepped stones. These landforms are located at a watershed, which are thus impossible to be formed due to tectonic processes, water or weathering, but can only be formed by glaciation. The calculated flat indexes of the fossil cirques in the Hexigten are 1.7-4.5, 4-5 and 1.3-5, which are within the range of 1.7-5 that is the flat index of real cirques. The typical and complete moraines have also been found in this area. All these glacial vestiges prove that the Quaternary glaciers did exist in the Da Hinggan Mountains of eastern China. Thus, it is of important scientific significance for the research on Chinese, even the global climatic and environmental evolution since the Quaternary.

Geology and Geochemistry of the Bianbianshan Au-Ag-Cu-Pb-Zn Deposit, Southern Da Hinggan Mountains, Northeastern China

The Bianbianshan deposit, the unique gold-polymetal （Au-Ag-Cu-Pb-Zn） veined deposit of the polymetal metallogenic belt of the southern segment of Da Hinggan Mountains mineral province, is located at the southern part of the Hercynian fold belt of the south segment of Da Hinggan Mountains mineral province, NE China. Ores at the Bianbianshan deposit occur within Cretaceous andesite and rhyolite in the form of gold-bearing quartz veins and veinlet groups containing native gold, electrum, pyrite, chalcopyrite, galena and sphalerite. The deposit is hosted by structurally controlled faults associated with intense hydrothermal alteration. The typical alteration assemblage is sericite ＋ chlorite ＋ calcite ＋ quartz, with an inner pyrite-sericite-quartz zone and an outer seicite - chlorite - calcite-epidote zone between orebodies and wall rocks. δ34 S values of 17 sulfides from ores changing from -1.67 to ＋0.49‰ with average of -0.49‰, are similar to δ34 S values of magmatic or igneous sulfide sulfur. 206Pb/204Pb, 207Pb/204Pb and 208Pb/ 204Pb data of sulfide from ores range within 17.66-17.75, 15.50-15.60, and 37.64-38.00, respectively. These sulfur and lead isotope compositions imply that ore-forming materials might mainly originate from deep sources. H and O isotope study of quartz from ore-bearing veins indicate a mixed source of deep-seated magmatic water and shallower meteoric water. The ore formations resulted from a combination of hydrothermal fluid mixing and a structural setting favoring gold-polymetal deposition. Fluid mixing was possibly the key factor resulting in Au-Ag-Cu-Pb-Zn deposition in the deposit. The metallogenesis of the Bianbianshan deposit may have a relationship with the Cretaceous volcanic-subvolcanic magmatic activity, and formed during the late stage of the crust thinning of North China.

Effects of Forest Roads on Habitat Pattern for Sables in Da Hinggan Mountains, Northeasten China

The anthropogenic managements of forest have created a network of roads resulting in the loss and alternation of habitat. To better understand road′s impact on animal habitats, we assessed the habitat pattern of sables(Martes zibellina), one of rodents within national first-class protected species, when roads are considered in Huzhong area in Da Hinggan Mountains, northeastern China. Employing published literatures about behavior ecology, aerial photographs and forest stand maps, we classified the study area into three habitat types including best-suitable, suitable and unsuitable habitats based on sable habitat requirements at the landscape scale including four variables derived from forest source map with attribute database. Results indicated the loss and significant fragmentation of best-suitable habitat and home range habitat when roads, especially 150 m avoidance distance of roads, were considered. The roads reduced and fragmented highly suitable habitats more significantly during earlier development period than the later development period. Additionally, the suitable area percentage increased with increasing distance to roads. This study helped to identify the suitable area for sables and location of sable population. Also, this study suggested the passage construction and road management involving road closure and removal will reduce the fragmentation functionally and benefit the sable population.

Responses of Soil Fauna Structure and Leaf Litter Decomposition to Effective Microorganism Treatments in Da Hinggan Mountains,China

Microorganisms are nutritious resources for various soil fauna.Although soil fauna grazing affects microorganism composition and decomposition rate,the responses of soil fauna and leaf litter decomposition to added microorganism is little understood.In this study,in the coniferous and broad-leaved mixed forest of Tahe County in the northern Da Hinggan Mountains,China,three sampling sites(each has an area of 10 m2) were selected.The first two sites were sprinkled with 250 times(EM1) and 1000 times(EM2) diluted effective microorganism(EM) preparations evenly,and the third site was sprinkled with the same volume of water as a control site.The responses of soil fauna structure and leaf litter decomposition to EM treatment were conducted during three years.The results revealed that EM treatment resulted in significant increase of soil organic matter.The number of soil fauna in the EM1 and EM2 sites increased by 12.88% and 2.23% compared to the control site,and among them springtails and mites showed the highest increase.However,the groups of soil fauna in the EM1 and EM2 sites decreased by 6 and 9,respectively.And the changes in the diversity and evenness index were relatively complicated.EM treatment slowed the decomposition of broad-leaved litter,but accelerated the decomposition of coniferous litter.However,the decomposition rate of broad-leaved litter was still higher than that of coniferous litter.The results of this study suggested that the added microorganisms could help individual growth of soil fauna,and this method led to a change in the process of leaf litter decomposition.This paper did not analyze the activity of soil microorganisms,thus it is difficult to clearly explain the complex relationships among litter type,soil fauna and soil microorganisms.Further research on this subject is needed.

Fluid Inclusion Geochemistry of Metallic Ore Deposits in the South- Central Sector of theDa Hinggan Mountains in China

Physicochemical parameters of mineralization such as temperature, pressure, salinity, density, composition and boiling of ore fluids as well as pH, Eh, fo2 and reducing parameter in theprocess of mineralization of major ore deposits in the study district have been obtained by the authors through systematic observation and determination of characteristics and phase changes of fluid inclusions at different temperatures and analysis of gaseous and liquid phase compositions of the inclusions, thus providing a scientific basis for the division of mineralization-alteration stages, types of mineral deposits and minerogenetic series and the deepening of the knowledge about the ore-forming processes and mechanisms of mineral deposits. It is indicated that the deposits of the same type have similar fluid inclusion geochemical features and physicochemical parameters though they belong to different minerogenetic series, while the compositions of inclusions are not conditioned by deposit types but closely related to the minerogenetic series of deposits.

Dynamics of Soil Fauna in Da Hinggan Mountains, Northeast China

The dynamics of soil animals was studied in seven representative forest communities in the north of the Da Hinggan Mountains, Northeast China. The results indicate that it was distinctive in the changes of the numbers of soil animals and groups and diversity in relationship with seasons for macrofauna and meso-micro fauna in the study area. The numbers of the observed soil animals in different months were: October>August>June. Group number was larger in August and October, but smaller in June. The change of diversity index in different months was: August>June>Oc- tober. The biomass for macrofauna in different months was: October>June>August. The composition and number of each functional group was relatively stable. In the community of the predominant soil environment, the percentage of saprophagous animals was higher than carnivorous animals and herbivorous animals. The dynamics changes of sapro- phagous and carnivorous animals were distinctive, increasing from June to October, while the change of herbivorous animals was unremarkable.

RS AND GIS-BASED FOREST FIRE RISK ZONE MAPPING IN DA HINGGAN MOUNTAINS

The Da Hinggan Mountains is one of the most important forest areas in China, but forest fire there is also of high frequency. So it is completely necessary to map forest fire risk zones in order to effectively manage and protect the forest resources. Two forest farms of Tuqiang Forest Bureau (53 degrees 34'-52 degrees 15'N,124 degrees 05'-122 degrees 18'E) were chosen as typical areas in this study. Remote sensing (RS) and Geographic Information System (GIS) play a vital role and can be used effectively to obtain and combine different forest-fire-causing factors for demarcating the forest fire risk zone map. Forest fire risk zones were described by assigning subjective weights to the classes of all the coverage layers according to their sensitivity to fire, using the ARC/INFO GIS software. Four classes of forest fire risk ranging from low to extremely high were generated automatically in ARC/INFO. The results showed that about 60.33% of the study area were predicted to be upper moderate risk zones, indicating that the forest fire management task in this area is super onerous. The RS and GIS-based forest fire risk model of the study area was found to be highly compatible with the actual fire-affected sites in 1987. Therefore the forest fire risk zone map can be used for guidance of forest fire management, and as basis for fire prevention strategies.

Latest Zircon U-Pb Age of the Baiyingaolao Formation Volcanic Rocks in the Keyihe Area of North-Central Da Hinggan Mountains

Objective Mesozoic volcanic rocks are mainly distributed in the Da Hinggan Mountains.The Baiyingaolao Formation is the main stratum in this area and has been considered to be formed in the Late Jurassic.Many scholars have researched these Mesozoic volcanic rocks in this area,which have been much debatable（Zhang Xiangxin et al.,2017）.A series of studies focusing on the Baiyingaolao Formation volcanic rocks in the middle-south section of

Value Assessment of Wetland Ecosystem Services in the Da Hinggan Mountains, China

This study examined regional differences in ecosystem services for the Da Hinggan Mountains(DHM),China.A correction index was constructed based on ten-year average net primary productivity(NPP)data.A new equivalent factor table that was suitable for the assessment of wetlands in the DHM was formed by using the expert weight determination method(EWDM).An evaluation model was established for evaluating the ecosystem service value(ESV)of wetlands in the DHM.The results show that in 2020,the total ESV of wetlands reached 93361×10^(6) USD,with the forest swamp and marsh ecosystems contributing the most.From the perspective of value composition,regulating services and supporting services are the main service functions of wetlands in the DHM.From 2010 to2020,ESV provided by wetlands increased by 4337×10^(6) USD/yr in the DHM.The value of forest swamp and peatland ecosystems increased by 18.6%and 12.7%,respectively,whereas the value of swamp,shrub swamp,and marsh decreased.The research results are of significance for contributing to local government performance evaluation and determining financial compensation for the provision of wetland ecosystem services.

New Zircon U-Pb Ages of Granitic Rocks in Northeastern Jiagedaqi of the Da Hinggan Mountains and their Significance

Objective The research area is located in the north of the Xing＇an block and within the Ali River-Zhalantun granite belt in the eastern part of the Xingmeng orogenic belt. The geotectonic setting and geological evolution history of this area are complex with strong magmatic activity and extremely developed granite rocks. Since predecessors have not obtained accurate dating result, there is much controversy over the formation of granitic rocks. Therefore, this work conducted zircon U-Ph dating on alkali-feldspar granite and granite porphyry in the northeast of Jiagedaqi to provide age constraint. The age data shows that the forming age is the Early Cretaceous and provides age basis for the tectonic evolution of the Da Hinggan Mountains.

Re-Os Geochronology of Porphyry Molybdenum Deposit in South Segment of Da Hinggan Mountains,Northeast China

The ages for porphyry Mo deposits in south segment of Da Hinggan Mountains, Northeast China, are not well known. Five molyhdenite samples from the Aolunhua （奥伦花） porphyry Mo deposit, five molybdenite samples from the Yangchang （羊场） porphyry-quartz vein Mo deposit and two molybdenite samples from the Banlashan （半拉山） porphyry Mo deposit were selected for Re-Os dating. Three deposits are spatial-temporally associated with the granite porphyry stock. Re-Os isochron age of 131.2±1.9 Ma was obtained for the Aolunhua porphyry Mo deposit. The Yangchang Mo deposit provides isochron age of 138.5±4.5 Ma for two groups of molybdenite （within porphyry ore and within quartz vein）. The Banlashan porphyry Mo deposit provides model ages of 140.5±2.4 and 143±2.2 Ma. All of these Re-Os ages are consistent presumed Yanshanian ages for granite intrusions, formed in crust thinning setting in Cretaceous in North China.

Symbiosis of Marshes and Permafrost in Da and Xiao Hinggan Mountains in Northeastern China

Recently, the degradation of permafrost and marsh environments in the Da and Xiao Hinggan Mountains has become a great concern as more human activities and pronounced climate warming were observed during the past 30 years and projected for the near future. The distr/bution patterns and development mechanisms of the permafrost and marshes have been examined both in theories and in field observations, in order to better understand the symbiosis of permafrost and marshes. The permafrost and marshes in the Da and Xiao Hinggan Mountains display discernible zonations in latitude and elevation. The marsh vegetation canopy, litter and peat soil have good thermal insulation properties for the underlying permafrost, resulting in a thermal offset of 3 ℃ to 4℃ and subsequently suppressing soil temperature. In addition, the much higher thermal conductivity of frozen and ice-rich peat in the active layer is conducive to the development or in favor of the protection of permafrost due to the semi-conductor properties of the soils overlying the permafrost. On the other hand, because permafrost is almost impervious, the osmosis of water in marsh soils can be effectively reduced, timely providing water supplies for helophytes growth or germination in spring. In the Da and Xiao Hinggan Mountains, the permafrost degradation has been accelerating due to the marked climate warming, ever increasing human activities, and the resultant eco-environmental changes. Since the permafrost and marsh environments are symbiotic and interdependent, they need to be managed or protected in a well-coordinated and integrated way.

LA-ICP-MS zircon U-Pb age of rhyolitic lithic-crystal tuffs in Erdaohezi lead-zinc deposit,Inner Mongolia

Erdaohezi lead-zinc deposit belongs to the Derbugan metallogenic belt lying on the northwestern Hailaer-Genhe Mesozoic volcanic basin, located on the western slope of the Da Hinggan Mountains. The deposit is considered as one of the hypabyssal low-temprature hydrothermal lead-zinc deposits associated with volca- nism. In order to lay the foundation on studying its diagenesis and mineralization ages, the detailed studies were carried out by dating the host rocks （i. e. rhyolitic lithic-crystal tufts） using zircon LA-ICP-MS U-Pb method. The dating results show three groups ot! ages. The first group is the captured zircons （the weighted mean ^206pb/238U age as 175.6± 2.3 Ma, MSWD = 0.70, n = 3）. The second group can be regarded as the rock- forming age （the weighted mean ^206pb/238U age as 165.3± 1.9 Ma, MSWD = 2.40, n = 14）. The third group should represent the late stage of the magmatic evolution （the weighted mean ^206pb/238U age as 161.0 ± 3.1 Ma, MSWD = 0.86, n = 4）. According to the ages and the crystal form or CL image characteristics of zircons, it is determined that the diagenesis occurred in the late Middle Jurassic. Based on the regional geology and geo- chronological research, the acidic pyroclastic rocks are space accompaniment and time connection with the Tamu- langou Formation intermediate-mafic volcanic rocks. Both of them constitute the host rocks of the deposit together. The rock combination also provides favorable conditions for large-scale silver, lead and zinc mineralization in this area.