Geochemistry and tectonic significance of Early Cretaceous granites in Highland 1248 of Daxing'anling

The Early Cretaceous granitic complex in Highland 1248 of Daxing'anling successively consists of intruded granodiorite,monzonite granite and syenite granite. Through test analysis on the major,trace and rare earth elements of the intrusive complex,this study focuses on the source characteristics and tectonic environment of the original magma of intrusive complex. The results show that the intrusive rocks in Highland 1248 are meta-aluminous-peraluminous rocks in calc-alkaline series with homologous characteristics in δEu negative anomalies; the complex is enriched in LILE( Rb,Cs and K) and depleted in HFSE( lanthanide,Sc,Y,U,Nb and Ta),displaying the geochemical characteristics of I-type granites in active continental-margin subduction zones. The complex also has the characteristics of granites after the collision of plate with rich aluminum and high potassium,but significantly depleted Nb,Ta,Ti,P and other elements,i. e. in the orogenic evolutionary stage. The zircon U-Pb SHRIMP isotopic apparent age of the complex in Highland 1248 is 140. 0--141. 0Ma,and the formation time is in Early Cretaceous.

Classification,metallogenesis and exploration of silver deposits in Daxing’anling of Inner Mongolia and its adjacent areas

By the end of 2020,83 silver deposits(or ore occurrences),including four super-large-scale deposits,nine large-scale deposits,33 medium-scale deposits and 37 small-scale deposits or ore occurrences,have been proved.The amount of silver metal exceeds 86000 t with average grade of 100 g/t,which makes Daxing’anling region one of the the most important silver ore belt in China.However,the metallogenic characteristics and metallogenesis need to be clarified.The silver deposits in the study area are classified into three main types,which are magmatic hydrothermal vein type,continental volcano-subvolcanic type and skarn type,respectively.The supergiant deposits include the Shuangjianzishan deposit(silver metal amount of 15214 t with average grade of 138 g/t),the Baiyinchagandongshan deposit(silver metal amount of 9446 t with average grade of 187 g/t),the Huaobaote deposit(silver metal amount of 6852 t with average grade of 170 g/t),and the Fuxingtun deposit(silver metal amount of 5240 t with average grade of 196 g/t).The silver deposits are mainly distributed in the central and south of the Daxing’anling area,and mainly formed in the Yanshanian period.The silver polymetallic deposits in the Daxinganling area are significantly controlled by regional faults and the junction zone of volcanic rock basins and their margins.The north-east trending deep faults are the most important ore-controlling structures in this area.The distribution of silver polymetallic deposits along the main faults is obvious,and the intersection area of multiple groups of faults often form important mine catchments.The Permian is the most important ore-bearing formation in this area,but some important silver polymetallic deposits occur in Mesozoic volcanic basins or pre-Mesozoic strata.The magmatic rocks related to mineralization are mainly intermediate acidic or acidic intrusions,intermediate acidic lavas,pyroclastic rocks,and small intrusions of ultra-shallow or shallow facies of the Yanshanian Period.The mineralization element combination is mainly determined by the elemental geochemical background of surrounding rocks or source layers.In addition,the type of deposit,the distance from the mineralization center,and the degree of differentiation of ore-forming rock mass are also important influence factors.The article analyzes the prospecting prospects of each silver deposit type in the study area,discusses the relationship between mineralization center and deep prospecting,and proposes that porphyry silver deposits should be paid attention to.In the prospecting and exploration of silver deposits,comprehensive evaluation and multi-target prospecting need to be strengthened because silver can coexist or be associated with a variety of metals.

Landscape change on burned blanks in Daxing'an Mountains

Daxing抋n Mountains was one of the most important forest areas in China, but it was also an area which was prone to suffering forest fire. The catastrophic forest fire that occurred in Daxing抋n Mountains on May 6, 1987 devastated more than 1.33?06 hm2 of natural forests, which leaded to the formation of some mosaic areas with different burn intensities. Two forest farms of Tuqiang Forest Bureau (124?5-122?8E, 53?4-52?5N) were chosen as a typical area to analyze the post-fire landscape change by drawing and comparing the two digital forest stand maps of 1987 and 2000. The landscape lands of forest were classi-fied into 12 types: coniferous forest, broadleaf forest, needle-broadleaf mixed forest, shrub, nursery, harvested area, burned blanks, agricultural land, swamp, water, built-up, grass. The results showed that: 1) The burned blanks was almost restored, some of them mainly converted into broadleaf forest land during the process of natural restoration, and coniferous forest land by the artificial re-forestation, and the others almost changed into swamp or grass land; 2) The proportion of forest area increased from 47.6% in 1987 to 81.3% in 2002. Therefore, a few management countermeasures, such as the enhancing peoples consciousness of fire-proofing and constructing species diversity, were put forward for forest sustainable development.

Study of seasonal snow cover influencing the ground thermal regime on western flank of Da Xing'anling Mountains,northeastern China

Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of the soils in permafrost regions in the mid-latitudes and boreal regions, such as that on the westem flank of the Da Xing＇anling （Hinggan） Mountains, northeastern China. This paper gives a detailed analysis on meteorological data series from 2001 to 2010 provided by the Gen＇he Weather Station, which is located in a talik of discontinuous permafrost zone and with sparse meadow on the observation field. It is inferred that snow cover is important for the ground thermal regime in the middle Da Xing＇anling Mountains. Snow cover of 10-cm in thickness and five to six months in duration （generally November to next March） can reduce the heat loss from the ground to the atmosphere by 28%, and by 71% if the snow depth increases to 36 cm. Moreover, the occurrence of snow cover resulted in mean annual ground surface temperatures 4.7-8.2℃ higher than the mean annual air temperatures recorded at the Gen＇he Weather Station, The beginning date for stable snow cover establishment （SE date） and the initial snow depth （SDi） also had a great influences on the ground freezing process. Heavy snowfall before ground surface freeze-up could postpone and retard the freezing process in Gen＇he. As a result, the duration of ground freezing was shortened by at least 20 days and the maximum depth of frost penetration was as much as 90 cm shallower.

Site classification of the eastern forest region of Daxing'an Mountains

Based on the plot data from the investigation and the theory of forest ecology and ecological system,the site classification of the eastern forest region of Daxing’an Mountains was made by mean of mathematical method. The main factors were slope, thickness of soil layer, slope position and slope aspect. Grades of slope were used as the division standard for site type group. The slope aspect, slope position and thickness of soil layer were used as the division standards for site type. Altogether 7 site type groups and 15 main site types were determined the region. It provided reliable fundamental basis for the reasonable management and planting design in the area.

Spring habitat selection of sables in Daxing'an Mountains

This paper studies the habitat selection of sables (Martes. zibellina) in spring adopting radio-tracking and GPS (Global Positioning System) in Daxing’an Mountains of China. Sables liked mature and elder forest, but it avoided uncovered and young growth land. In spring sables had strong selection to medium cover-degree forest, but it avoided widen ground and especial high cover-degree forest. On the contrary sables didn’t have the strong selection to shrubs cover-degree, but strong selection to dominant tree species, slope degree and slope direction, especially sable liked medium and lower slope. At the same time, sables had the strong selection to the log’s density and the crown’s cover-degree. Generally it avoided high elevation and lower slope land.

Population Characteristics of Dendrolims Superans in Daxing'an Mountains

Dendrolims superans produced one generation every two years Large larvae and small larvae exist at the sametime. lt broke out in Daxiang an Mountains in 1990. and seriously destroyed growth of Larix gmelum Rupr In order to control D Superans.the population properties of D.superans were stedied from 1991 to 1992 including sex ratio.age distribution. pattern etc.. The sex ratio of D. superans population is The larvae age distrihution indicates that larvaeover 5 instar is less than younger larvae under 4 instar in Yongqing forest farm- but the younger larvae under 4 instar is morethan larvae over 5 instar in Hanjiayuanzi Forest Farm. The population of D. superans in Yongqing Farm has heen declining.and incrcasing in Hanjiayuanzi. Pupae and eggs are mainly distributed in middle and lower crowns layer of trees. respec-tively account for 66% and 59.5%, of total individuals. The pupae in higher cown layer is lightly regular distrihution. andclumping distribution middle and lower crowns layer of trees. The eggs in higher crown is light clumpin1g distribution. andrandom in middle and low crown of tree.

Quantitative dynamics on stimulating regeneration and sowing seedlings of Larix gmelinii in Daxing'an Mountains

To understand the quantitative dynamics and death reason of stimulating regeneration seedlings is significant for stimulating the natural regeneration ofLarix gmelinii and implement of conservation project of natural forest. This paper summarized location observations and directly-seeding simulation experiments of six permanent sample plots that were set up after the seed bumper harvest year ofLarix gmelinii in 1989. The study showed that stimulating natural regeneration seedlings had a large mortality in the first three years, especially in the first year of seedling emergence. After three years seedlings died less and stepped into the stable regeneration stage. A large number of seedlings died of sunscald as the primary death reason. For those areas of good site conditions and rich soil, damping-off would cause seedlings to death in large quantities. The task of stimulating regeneration is mainly to get rid of the litter (forest floor) on burned areas. By means of promoting measures, emergence rate of sown seeds would be several times and dozens of times higher than that of seed shedding on the condition of retention of forest floor. Promoting the regeneration need to select the suitable site against great slope and low-lying lands; at the same time, be careful of the avoidance of frost heaving by depression water.

基于Landsat时间序列数据的火烧迹地识别与恢复效果评价

为研究大兴安岭地区火烧迹地识别和火后植被恢复状况,基于2006—2020年Landsat TM遥感影像,利用Google Earth Engine编写代码,以2006年大兴安岭地区松岭区那源林场森林火灾为研究背景,以差分归一化燃烧指数(dNBR)为基础数据进行火烧迹地识别,并对火烧烈度进行轻度、中度、重度和极重的等级划分;基于火烧迹地的增强型植被指数(EVI)值,采用一元线性回归分析、用于气候诊断与预测的Mann-Kendall突变检验法和用于做趋势分析的Theil-Sen median趋势分析等方法分析火烧迹地2006—2020年的植被恢复特征,探究大兴安岭地区火烧迹地植被恢复进程。结果表明,1)基于dNBR得到研究区过火面积为2488.7 hm^(2),其中轻度、中度、重度和极重火烧迹地面积占比分别为23.5%、9.6%、35.2%和31.7%,重度和极重过火区分布于火烧迹地西部和东部,过火强度从中部向南部和北部逐渐降低,其EVI值与火烧前相比分别下降了约30%、40%、58%和67%;2)不同烈度林地火烧迹地EVI恢复速率由大到小表现为极重、重度、中度、轻度,植被恢复过程中,迹地EVI值逐渐增加,其中,轻度和中度火烧迹地可在火后6~8 a恢复,而重度火烧迹地的恢复则需14 a;3)火烧迹地恢复过程中,林地EVI突变点较灌草地少,说明森林生态系统较灌草地稳定性强。不同烈度林地火烧迹地的突变情况也存在一定差异,且对照区的突变时间点滞后于火烧迹地。

大兴安岭沿麓黑土区翻耕农田微立垡覆盖阻风减蚀技术创新与应用

大兴安岭沿麓是我国重要的农畜产品生产基地,由于长期过度耕作和单一翻耕等不合理的耕作方式,加速了该地区农田风蚀退化、质量下降和产能降低,因此,减少土壤风蚀、提升农田地力和作物产量是农业可持续发展亟待解决的问题。文章综述了不同类型生态区传统翻耕、长期免耕、合理轮耕技术及其应用效果,论述了翻耕地微立垡覆盖阻风减蚀核心技术的内容及其对土壤风蚀、蓄水保墒、作物生长与产量等方面的影响,明确了微立垡覆盖是大兴安岭沿麓黑土区翻耕地冬春季风蚀防控的关键技术和途径。翻耕地微立垡覆盖阻风减蚀技术大面积应用效果显著,破解了长期以来翻耕农田裸露风蚀重、水土流失损失大导致农田逐步退化的科技难题,为大兴安岭沿麓及其生态类型相似区翻耕农田风蚀防控研究提供了重要支撑。

内蒙古大兴安岭林火时空动态的变化特征

内蒙古大兴安岭森林火灾频发,研究其季节性变化趋势及空间动态分布特征,对今后该地区森林防火期划分和防火资源的合理分配具有重要意义。利用Mann-Kendall趋势检验法、滑动t检验法对1981—2018年内蒙古大兴安岭森林火灾数据进行趋势和突变分析,使用分位数回归法研究影响森林火灾过火面积的时间与空间因素,得出内蒙古大兴安岭森林火灾在时间和空间上的动态变化特征。结果表明:内蒙古大兴安岭森林火灾整体呈先下降(1981—1999年)再上升(2000—2007年)又下降(2008—2018年)的趋势。森林火灾主要发生在春、夏、秋三季,春季森林火灾变化较复杂,波动明显,在1991年发生突变;秋季森林火灾波动较平缓,但在1994年发生突变;2004—2011年期间夏季森林火灾明显增长,火险期向夏季发生偏移和延长;冬季发生火灾较少。森林火灾过火面积与火灾持续时间呈正相关,尤其在高分位点处,正相关性更加显著。内蒙古大兴安岭森林火灾主要发生在鄂伦春自治旗等地,从空间横向动态变化来看,整体呈现由西南向东北递增的趋势;从空间纵向动态变化来看,海拔对森林火灾过火面积的影响并不显著。建议应加强内蒙古大兴安岭东北地区及春、夏两季的林火监测和防火宣传,适当调整森林防火期和防火资源时空分配,将有助于减少内蒙古大兴安岭森林火灾的发生。

大兴安岭东部林区天然林主要树种胸径生长模型构建

预测大兴安岭地区天然林主要树种胸径生长对未来该地区森林动态监测和规划管理具有重要意义。本研究以大兴安岭东部林区全区1034块三期连续清查数据为研究对象,使用5种常见的模型形式作为基础模型,对8个天然树种调查数据进行拟合,最终构建了8个天然主要树种的胸径预测模型。使用总相对误差(R_(S)),决定系数(R~2)、平均相对误差(■)、预估精度(P)、L值(L)5个指标对8种天然林主要树种的5个拟合模型的拟合效果进行评估。最终结果表明M1模型是樟子松、山杨和黑桦的最优胸径预测模型,M5模型是兴安落叶松、河岸杨柳、云杉、白桦和柞木的最优胸径预测模型。本研究所构建的大兴安岭地区天然林8个主要树种的胸径生长模型拟合效果较好,能有效为未来森林生长动态预测提供支持。

呼中林业局乔木林碳储量及碳密度研究

依据呼中林业局2017年森林资源二类调查数据,在分树种、起源、龄组的基础上,采用生物量扩展因子法,对呼中林业局乔木林碳储量、碳密度进行估算和分析。结果显示,呼中林业局乔木林资源总碳储量为29371948.3 t,平均碳密度为39.98 t/hm^(2);天然林碳储量占乔木林碳储量的99.4%,处于绝对优势;兴安落叶松和白桦碳储量占乔木林总碳储量的96.6%,中龄组碳储量最大,占比接近乔木林碳储量的1/2;樟子松林平均碳密度远高于其他树种。

Zircon SHRIMP U-Pb Dating and Geochemical Characteristics of Late Variscan Granites of the Daitongshan Copper Deposit and Lamahanshan Polymetallic-Silver Deposit, Southern Daxing'anling, China

Daxing＇anling （大兴安岭） area is one of the regions that Phanerozoic granites are extremely developed in NW China. At present, the Hercynian granitoid research lags behind the Mesozoic granitoid research. In this article, we have taken systematic petrochemistry and geochronology researches on the Hercynian granitoids in Daitongshan （代铜山） copper deposit and Lamahanshan （喇嘛罕山） silver poly- metallic deposit, which were located at southern section of Daxing＇anling metallogenic belt. Zircon SHRIMP U-Pb dating results show that, the granite aplites in Daitongshan and the gneissic granites inLamahanshan were formed at （265±5）-（268±9） Ma and （252±2）-（252.6±3.4） Ma, respectively, which were both the products of late Herynian tectonic-magmatic events. Samples from Lama- hanshan are characterized by high SiO2 （69.72 wt.%-74.65 wt.%）, high potassium （3.53 wt.%-4.55 wt.%） and low P205 （0.03 wt.%0.12 wt.%）, aluminum saturation index （A/CNK） range from 0.95 to 0.98, Rb, Nd and K are en- riched, whereas the elements such as Nb, Ta, P and Ti are depleted, which belong to I-type grani- toids. Characteristics of samples from Daitong- shan are similar to H-type granitoids. The magmasource may be mostly originated from the lithospheric mantle component which were transformated or affected by the subduction components, and its formation may be closely related with the subduction and orogenesis of the Paleo-Asian Ocean.

大兴安岭南段锡的成矿作用:以黄岗-甘珠尔庙地区为例

大兴安岭南段是我国重要的锡多金属成矿集中区,为促进区域锡多金属找矿突破,以在黄岗-甘珠尔庙地区多年的野外调查研究工作为基础,运用年代学测试、化学分析及地质模型等方法,分析了区域锡的成矿作用。认为二叠统基底地层及锡林郭勒杂岩是成矿物质的初始来源,经历的变质过程具有进一步富集的作用,大部分锡矿均遭受了多期次的火山-岩浆活动,最终决定锡多金属成矿的是燕山期酸性岩浆-热液成矿作用。同时成矿作用还受到控岩控矿构造、围岩性质、氧化-还原条件、开放-封闭环境的制约,认为在氧化性花岗岩浆侵入钙质地层条件下成矿作用以铁锡为主;还原性岩浆在侵入具开放性特征的围岩时,成矿作用以花岗岩外带围岩中的热液型脉状锡矿为主,而在侵入具封闭性特征的围岩时,成矿作用以花岗岩内带岩浆凸起部位的花岗岩型锡矿为主。因此,建议将主攻矿种由铅锌调整为锡银,部署重砂及化探方法圈定异常,针对硫化矿体部署电法,针对隐伏岩体部署磁法与重力,还可部署烃、汞、氧气测量等非常规化探方法预测隐伏岩体。

大兴安岭呼中林业局森林景观格局变化及其驱动力

以大兴安岭呼中林业局为研究区,利用TM数据、森林资源清查数据和采伐统计资料,结合野外调查,以GIS为技术手段,剖析研究区1989～2000年景观变化,结果表明该区主要景观类型为针叶林、针阔混交林和阔叶林,这3种类型面积总比例达90%以上,其他景观类型面积比例小于10%,主要有荒草地、火烧迹地、采伐迹地、沼泽、居民点和道路.10a间景观由原有的大面积连续的针叶林为基质、小面积的阔叶林和针阔混交林斑块散布其中的格局,转变成大面积针阔混交林为基质的格局.研究区1989年是成过熟林、高公顷蓄积量、高郁闭度占优势的景观,2000年中幼龄林、低公顷蓄积量和低郁闭度森林面积增大,并趋于连续,形成低质量的相对均质化的景观.最后,结合历史资料,通过比较分析火烧、人工更新、土地利用和人为采伐活动这几种主要驱动力的特征,论证了采伐活动在该地区景观变化中所发挥的主导作用.

大兴安岭东部林区植被蓄水潜力与价值的评估

以中国植被1∶100万植被图为基础,收集了各种植被类型冠层降水截留量、枯落物现存量和土壤非毛管孔隙度的数据和资料,将大兴安岭东部林区主要植被类型归并为9类,对这些主要植被类型对降水的分配和贮存进行了综合评价,并研究了大兴安岭地区植被蓄水潜力及其价值的空间分布特征。结果表明:大兴安岭原生植被中,以蒙古栎为优势种的落叶阔叶林、云冷杉林和兴安落叶松林具有较强的持水能力。兴安落叶松林分布面积广,蓄水潜力占全区水源涵养价值的58.4%。从区域分布来看,水源涵养能力强的植被主要分布在该区的东南部。为了防止本区植被水源涵养能力的衰退,需要控制采伐,加强天然林保护,同时要加强护林防火工作,防止森林向山地杨桦林、疏林和低效林退化。

大兴安岭天然沼泽湿地生态系统碳储量

采用碳/氮分析仪测定法与标准木解析法,研究大兴安岭5种典型天然沼泽湿地(草丛沼泽、灌丛沼泽、毛赤杨沼泽、白桦沼泽和落叶松沼泽)的生态系统碳储量(植被和土壤)、净初级生产力、植被年净固碳量及其沿沼泽至森林方向过渡带水分环境梯度的分布格局,揭示其空间变异规律性,并定量评价寒温带5种典型天然沼泽湿地的碳储量与固碳能力及其长期碳汇作用。结果表明:①5种天然沼泽湿地的植被碳储量分布在(0.48±0.08)—(8.33±0.66)kgC/m2之间,沿过渡带环境梯度呈递增趋势;②土壤碳储量分布在(19.21±6.17)—(38.28±4.86)kgC/m2之间,沿过渡带环境梯度却呈递减趋势;③生态系统碳储量分布在(27.54±7.16)—(38.76±4.58)kgC/m2之间,沿过渡带环境梯度基本呈恒定分布规律性,且以湿地土壤碳储量占优势地位(69.8%—98.8%);④植被净初级生产力分布在(0.68±0.10)—(1.08±0.12)kg.m-.2a-1之间,毛赤杨沼泽最高,草丛沼泽、灌丛沼泽、白桦沼泽居中,落叶松沼泽最低,且总体上低于温带森林湿地而高于寒温带天然落叶松林;⑤植被年净固碳量分布在(0.32±0.09)—(0.51±0.06)kgC.m-.2a-1,毛赤杨沼泽最高(高于全球植被平均年净固碳量)、灌丛沼泽和白桦沼泽居中(达到或接近全球平均值)、草丛沼泽和落叶松沼泽最低(略低于全球平均值),故这5种沼泽湿地均属于碳汇功能相对较强的湿地植被类型。

1987年特大火灾后不同树种种植比例对大兴安岭森林景观的长期影响

应用空间直观景观模型(LANDIS)模拟了1987年大兴安岭北坡图强林业局特大森林火灾后在目前种植强度下,不同落叶松和樟子松种植比例(100%落叶松(P1)、70%落叶松和30%樟子松(P2)、50%落叶松和50%樟子松(P3)、30%落叶松和70%樟子松(P4)、100%樟子松(P5))以及完全依靠天然更新(P0)条件下森林景观的长期动态变化.结果表明,在演替的前期、中期和后期,不同种植比例均对落叶松、樟子松和白桦有显著影响;落叶松所占的面积百分比随时间的推移均呈上升趋势,而樟子松则相反;在各种植预案下,落叶松和樟子松的面积百分比均高于天然更新预案的比例,随着落叶松种植比例的增加,落叶松的多度也相应增加;樟子松在该区所占的面积百分比也随其种植比例的增大而增加.白桦在天然更新预案下所占的面积百分比明显高于种植预案下所占的比例;而不同落叶松和樟子松种植比例也对白桦面积有较大影响,樟子松种植的比例越大,白桦所占的面积百分比越高,说明落叶松比樟子松有更强的竞争能力.但P2、P3和P4预案下,落叶松和樟子松的面积所占比例相差不大,但要高于完全种植落叶松(P1)或樟子松(P)所占的比例.