Early Devonian Post-collisional Granitic Magmatism in the North Qilian Orogenic Belt,Western China:Insights into Lithospheric Delamination and Orogenic Collapse

Post-collisional magmatism contains important clues for understanding the reworking and growth of continental crust,as well as lithospheric delamination and orogenic collapse.Early Devonian magmatism has been identified in the North Qilian Orogenic Belt(NQOB).This paper reports an integrated study of petrology,whole-rock geochemistry,Sm-Nd isotope and zircon U-Pb dating,as well as Lu-Hf isotopic data,for two Early Devonian intrusive plutons.The Yongchang and Chijin granites yield zircon U-Pb ages of 394-407 Ma and 414 Ma,respectively.Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium-rich minerals,LREE-enriched patterns with negative Eu anomalies and a negative correlation between P_(2)O_(5) and SiO_(2) contents,consistent with geochemical features of I-type granitoids.Zircons from the studied granites display negative to weak positive ε_(Hf)(t)values(−5.7 to 2.1),which agree well with those of negative ε_(Nd)(t)values(−6.4 to−2.9)for the whole-rock samples,indicating that they were derived from the partial melting of Mesoproterozoic crust.Furthermore,low Sr/Y ratios(1.13-21.28)and high zircon saturation temperatures(745℃ to 839℃,with the majority being>800℃)demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source.Taken together,the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle-derived magmas at high-temperature and low-pressure conditions during postcollisional extensional collapse.The data obtained in this study,when viewed in conjunction with previous studies,provides more information about the tectonic processes that followed the closure of the North Qilian Ocean.The tectonic transition from continental collision to post-collisional delamination could be constrained to~430 Ma,which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon ε_(Hf)(t)values for granitoids.A two-stage tectonic evolution model from continental collision to post-collisional extensional collapse for the NQOB includes(a)continental collision and crustal thickening during ca.455-430 Ma,characterized by granulite-facies metamorphism and widespread low-Mg adakitic magmatism;(b)post-collisional delamination of thickened continental crust and extensional collapse of orogen during ca.430-390 Ma,provided by coeval high-Mg adakitic magmatism,A-type granites and I-type granitoids with low Sr-Y ratios.

Temperature trends and its elevation-dependent warming over the Qilian Mountains

Understanding temperature variability especially elevation dependent warming(EDW)in high-elevation mountain regions is critical for assessing the impacts of climate change on water resources including glacier melt,degradation of soils,and active layer thickness.EDW means that temperature is warming faster with the increase of altitude.In this study,we used observed temperature data during 1979-2017 from 23 meteorological stations in the Qilian Mountains(QLM)to analyze temperature trend with Mann-Kendall(MK)test and Sen’s slope approach.Results showed that the warming trends for the annual temperature followed the order of T_min>T_mean>T_max and with a shift both occurred in 1997.Spring and summer temperature have a higher increasing trend than that in autumn and winter.T_mean shifts occurred in 1996 for spring and summer,in 1997 for autumn and winter.T_max shifts occurred in 1997 for spring and 1996 for summer.T_min shifts occurred in 1997 for spring,summer and winter as well as in 1999 for autumn.Annual mean diurnal temperature range(DTR)shows a significant decreasing trend(-0.18°C/10a)from 1979 to 2017.Summer mean DTR shows a significant decreasing trend(-0.26°C/10a)from 1979 to 2017 with a shift occurred in 2010.After removing longitude and latitude factors,we can learn that the warming enhancement rate of average annual temperature is 0.0673°C/km/10a,indicating that the temperature warming trend is accelerating with the continuous increase of altitude.The increase rate of elevation temperature is 0.0371°C/km/10a in spring,0.0457°C/km/10a in summer,0.0707°C/km/10a in autumn,and 0.0606°C/km/10a in winter,which indicates that there is a clear EDW in the QLM.The main causes of warming in the Qilian Mountains are human activities,cloudiness,ice-snow feedback and El Nino phenomenon.

Petrogenesis and tectonic implications of the Silurian adakitic granitoids in the eastern segment of the Qilian Orogenic Belt,Northwest China

Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.

Differential response of radial growth and δ^(13)C in Qinghai spruce(Picea crassifolia) to climate change on the southern and northern slopes of the Qilian Mountains in Northwest China

Tree radial growth can have significantly differ-ent responses to climate change depending on the environ-ment.To elucidate the effects of climate on radial growth and stable carbon isotope(δ^(13)C)fractionation of Qing-hai spruce(Picea crassifolia),a widely distributed native conifer in northwestern China in different environments,we developed chronologies for tree-ring widths and δ^(13)C in trees on the southern and northern slopes of the Qilian Mountains,and analysed the relationship between these tree-ring variables and major climatic factors.Tree-ring widths were strongly influenced by climatic factors early in the growing season,and the radial growth in trees on the northern slopes was more sensitive to climate than in trees on the southern.Tree-ring δ^(13)C was more sensitive to climate than radial growth.δ^(13)C fractionation was mainly influenced by summer temperature and precipitation early in the growing season.Stomatal conductance more strongly limited stable carbon isotope fractionation in tree rings than photosynthetic rate did.The response between tree rings and climate in mountains gradually weakened as climate warmed.Changes in radial growth and stable carbon isotope fractionation of P.crassifolia in response to climate in the Qilian Mountains may be further complicated by continued climate change.

Soil microbial community diversity and distribution characteristics under three vegetation types in the Qilian Mountains, China

Qilian Mountains in Northwest China is a significant ecological security barrier due to its distinctive geographic setting,which has significant biological resource and gene pool.In order to assess the soil quality and ecosystem health in this area,we identified the structural characteristics and functional groups of soil microbial communities.This study focused on Amidongsuo,a typical watershed of the Qilian Mountains,and researched the vertical distribution and dominant populations of soil microorganisms in different habitats,and the relationship between soil microorganisms and environmental factors.Soil microorganisms from three grassland plots,five shrubland plots,and five forest plots in Amidongsuo were studied using high-throughput sequencing.The Venn diagram showed that the types of bacteria were fewer than those of fungi in Amidongsuo.Soil bacteria Acidobacteriota,Proteobacteria,and Methylomirabilota as well as fungi Basidiomycota,Ascomycota,and Mortierellomycota played dominant roles in Amidongsuo,according to the LEfSe(linear discriminant analysis(LDA)effect size)and community structure analyses.According to the ANOSIM(analysis of similarities)result,for both bacteria and fungi,R values of grassland and shrubland were small(R^(2)=0.045 and R^(2)=0.256,respectively),indicating little difference between these two ecosystems.RDA(redundancy analysis)showed a closer relationship between soil nutrients and fungi,and a gradually decreasing correlation between soil nutrients and microorganisms with increasing soil depth.Bacteria were mainly affected by pH,nitrogen(N),and potassium(K),while fungi were mainly affected by K.Overall,fungi had more effect on soil quality than bacteria.Therefore,adjustment of soil K content might improve the soil environment of Amidongsuo in the Qilian Mountains.

Soil seed bank is affected by transferred soil thickness and properties in the reclaimed coal mine in the Qilian Mountains, China

Reclamation of lands abandoned after mining in mountain areas is critical to erosion control,safety from landslides,and ecological protection of mountain ecosystems.However,little is known about alpine coal mine reclamation using the soil seed bank as a potential source for revegetation.We collected samples of persistent soil seed bank for germination experiments from nine reclaimed sites with different soil cover thicknesses and from six control sites in the Qilian Mountains of China.Soil properties of each site were determined(including soil water content,soil available potassium,soil available phosphorus,soil total nitrogen,pH,soil organic matter,soil total phosphorus,and soil total potassium,and soil alkali-hydrolyzable nitrogen),and the relationships of the characteristics of the soil seed bank with soil cover thickness and soil properties were examined.The results showed that the density,number of species,and diversity of the topsoil seed bank were significantly correlated with soil cover thickness,and all increased with the increment of soil cover thickness.Soil cover thickness controlled the soil seed bank by influencing soil properties.With the increase in soil cover thickness,soil properties(e.g.,soil organic matter,soil total nitrogen,etc.)content increased while soil pH decreased.The soil seed bank had the potential to restored the pre-mining habitat at reclaimed sites with approximately 20-cm soil cover thickness.Soil properties of reclaimed sites were lower than that of natural sites.The relationship between the soil seed bank and soil cover thickness determined in this study provides a foundation for improving reclamation measures used in coal mines,as well as for the management and monitoring of reclaimed areas.

Spatio-temporal variation of water conservation and its impact factors on the southern slope of Qilian Mountains

The ecology of Qilian Mountains has been seriously threatened by uncontrolled grazing and wasteland reclamation. This study examined the ecological changes on the southern slope of Qilian Mountains in China from the perspective of water conservation by classifying different clusters of water conservation functional areas to efficiently use limited human resources to tackle the water conservation protection problem. In this study, we used Integrate Valuation of Ecosystem Services and Tradeoffs(InVEST) model to estimate water conservation and analyzed the factors that influence the function. The results of this study include:(1) from 2000 to 2015, the water conservation of the southern slope of Qilian Mountains generally showed an increasing trend, and the total water conservation in 2015 increased by 42.18% compared with that in 2000.(2) Rainfall, fractional vegetation cover(FVC), and evapotranspiration have the most significant influence on the water conservation of the study area. Among them, water conservation is positively correlated with rainfall and FVC(P<0.05) and negatively correlated with evapotranspiration(P<0.05).(3) The importance level of water conservation functional areas gradually increases from northwest to southeast, and the region surrounding Menyuan Hui Autonomous County in the southeast of the southern slope of Qilian Mountains is the core water conservation functional area. And(4) the study area was divided into five clusters(Cluster Ⅰ–Cluster Ⅴ) of water conservation, with the areas of Clusters Ⅰ through Ⅴ accounting for 0.58%, 13.74%, 41.23%, 32.43%, and 12.01% of the whole study area, respectively.

Heterogeneity and non-linearity of ecosystem responses to climate change in the Qilian Mountains National Park, China

Ecosystem responses to climate change,particularly in arid environments,is an understudied topic.This study conducted a spatial analysis of ecosystem responses to short-term variability in temperature,precipitation,and solar radiation in the Qilian Mountains National Park,an arid mountainous region in Northwest China.We collected precipitation and temperature data from the National Science and Technology Infrastructure Platform,solar radiation data from the China Meteorological Forcing Dataset,and vegetation cover remote-sensing data from the Moderate Resolution Imaging Spectroradiometer.We used the vegetation sensitivity index to identify areas sensitive to climate change and to determine which climatic factors were significant in this regard.The findings revealed a high degree of heterogeneity and non-linearity of ecosystem responses to climate change.Four types of heterogeneity were identified:longitude,altitude,ecosystem,and climate disturbance.Furthermore,the characteristics of nonlinear ecosystem responses to climate change included:(1)inconsistency in the controlling climatic factors for the same ecosystems in different geographical settings;(2)the interaction between different climatic factors results in varying weights that affect ecosystem stability and makes them difficult to determine;and(3)the hysteresis effect of vegetation increases the uncertainty of ecosystem responses to climate change.The findings are significant because they highlight the complexity of ecosystem responses to climate change.Furthermore,the identification of areas that are particularly sensitive to climate change and the influencing factors has important implications for predicting and managing the impacts of climate change on ecosystems,which can help protect the stability of ecosystems in the Qilian Mountains National Park.

Early Cretaceous Thrust and Nappe Tectonics in North Qilian Shan,Northern Tibetan Plateau:Evidence from Field Mapping,Geochronology,and Deep Structural Analysis

The North Qilian Shan fold and thrust belt,located at the northern Tibetan Plateau and southern margin of the Hexi Corridor,is a key tectonic unit to decode the formation and expansion of the plateau.Previous studies emphasize the Cenozoic deformation due to the far-field response to the Indo-Asian collision,but the Mesozoic deformations are poorly constrained in this area.We conducted detailed field mapping,structural analysis,geochronology,and structural interpretation of deep seismic reflectional profiling and magnetotelluric(MT)sounding,to address the superposed results of the Mesozoic and Cenozoic deformation.The results recognized the North Qilian thrust and nappe system(NQTS),the root and the frontal belt are the North Qilian thrust(NQT),and the Yumu Shan klippe(YK),respectively.The middle belt is located between the NQT and the YK.Monzonitic granite zircon U-Pb dating from the middle belt yields an age of ca.415 Ma,which is similar to south NQT.The thrusting displacement is estimated at ca.48 km by structural interpretation of deep profiles.The timing is constrained in the early stage of the Early Cretaceous by the formation of simultaneous growth strata.We suggest that the NQTS has resulted from the far-field effect of the Lhasa-Qiangtang collision,and the Yumu Shan is uplifted by the superposed Cenozoic deformation.

Growth behavior and resource potential evaluation of gas hydrate in core fractures in Qilian Mountain permafrost area, Qinghai-Tibet Plateau

The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment,due to its well-developed fractures and abundant gas sources.Understanding the formation and distribution of multi-component gas hydrates in fractures is crucial in accurately evaluating the hydrate reservoir resources in this area.The hydrate formation experiments were carried out using the core samples drilled from hydrate-bearing sediments in Qilian Mountain permafrost area and the multi-component gas with similar composition to natural gas hydrates in Qilian Mountain permafrost area.The formation and distribution characteristics of multi-component gas hydrates in core samples were observed in situ by X-ray Computed Tomography(X-CT)under high pressure and low temperature conditions.Results show that hydrates are mainly formed and distributed in the fractures with good connectivity.The ratios of volume of hydrates formed in fractures to the volume of fractures are about 96.8%and 60.67%in two different core samples.This indicates that the fracture surface may act as a favorable reaction site for hydrate formation in core samples.Based on the field geological data and the experimental results,it is preliminarily estimated that the inventory of methane stored in the fractured gas hydrate in Qilian Mountain permafrost area is about 8.67×1013 m3,with a resource abundance of 8.67×108 m3/km2.This study demonstrates the great resource potential of fractured gas hydrate and also provides a new way to further understand the prospect of natural gas hydrate and other oil and gas resources in Qilian Mountain permafrost area.

Long-term improvements in water conservation functions at Qilian Mountain National Park, northwest China

Water conservation is one of the most important ecosystem functions.This study uses the InVEST model to examine the water conservation function of the Qilian Mountain National Park(QMNP),an important water supply area in northwest China.We analyzed the spatiotemporal water conservation patterns of QMNP from 1988 to 2019.It showed that the water conservation capacity in QMNP has increased over the past 32 years,reaching a peak of 6.495×108 m3 in 2019.The area with an increased water conservation capacity is 12 times larger than the area with a reduced capacity.We also examined how climatic,land-use,vegetation coverage,and topographical factors influence water conservation functions.We found that precipitation is the main climatic factor in water conservation.The water conservation function also varies with land-cover type,with forests having the highest capacity,followed by grasslands.Lastly,topographical factors,including altitude and slope,also shape the spatial patterns of water conservation functions in QMNP.

北祁连冷龙岭地区上奥陶统扣门子组的时代归属——来自牙形石的证据

本文首次报道了北祁连冷龙岭地区上奥陶统扣门子组牙形石,共识别鉴定出牙形石5属,9种,其中3个未定种,根据牙形石的分布规律,建立了1个牙形石组合:Aphelognathus grandis-Panderodus gracilis组合。笔者通过对研究区牙形石组合与国内外其他地区相同层位的牙形石带对比,并结合扣门子组其它古生物化石资料,将北祁连冷龙岭地区扣门子组的时代重新厘定为晚奥陶世桑比期—赫南特期中期,相当于中国地层年表的艾家山期晚期—钱塘江期中期。

祁连山北坡沙尘天气气溶胶特征的飞机观测

了解沙尘天气下气溶胶的垂直分布特征对于进一步认识气溶胶-云相互作用及其天气、气候效应至关重要。基于2023年9月6日沙尘天气下的飞机观测数据,分析祁连山北坡沙尘气溶胶的垂直分布特征。结果表明:此次沙尘天气是在高空锋区及地面冷高压的共同作用下形成。受沙尘天气影响,气溶胶粒径谱宽增宽;气溶胶数浓度较背景可上升约2~3倍,且气溶胶数浓度大值区呈悬垂状态分布,粒子数浓度大值层位于4000~4500 m和3000~4000 m高度;对沙尘气溶胶数浓度贡献最大的细粒子和粗粒子粒径分别为1.2~1.8μm和6.5~16.6μm,且气溶胶数浓度的增大在粗粒子段更为明显。气溶胶来源及输送层、以及气象要素垂直分布演变在气溶胶垂直分布及谱分布中发挥了重要作用。

南祁连党河南山地区拐杖山岩群玄武岩年代学、地球化学及其构造环境

【研究目的】前人在南祁连志留纪巴龙贡噶尔组中解体出新元古代拐杖山岩群,对该群中玄武岩的年龄、成因与成岩构造环境的研究是厘清南祁连地区构造演化的重要手段。【研究方法】本文基于LA-ICP-MS锆石U-Pb年龄和全岩地球化学分析等方法研究拐杖山岩群火山岩的形成年代、地球化学特征及地质意义。【研究结果】锆石U-Pb定年结果显示,玄武岩喷发年龄为(786.6±5.8)Ma,表明拐杖山岩群形成于新元古代早期。岩石地球化学分析结果表明,玄武岩SiO_(2)含量在48.09%~50.97%,高TiO_(2)(1.34%~2.55%),低MgO(5.78%~7.11%),显示亚碱性拉斑玄武岩特征。岩石轻、重稀土分异明显((La/Yb)_(N)=3.76~4.51),无明显Eu异常(δEu=0.80~1.05),大离子亲石元素Ba、Th、U相对富集,Pb强富集,亏损Nb、Ta、Ti等高场强元素。【结论】岩石地球化学特征暗示拐杖山岩群玄武岩是遭受陆壳物质混染的地幔源区玄武岩,该火山岩形成于大陆裂谷环境,响应了全球新元古代Rodinia超大陆裂解事件。

青海门源M6.9级地震地表破裂特征及区域地震活动趋势分析

据中国地震台网正式测定,2022年1月8日1时45分青海海北州门源县发生6.9级地震,震源深度10 km。此次地震是2016年门源M6.4级地震之后冷龙岭地区再次发生强震活动。此次地震的宏观震中位于距门源县城浩门镇西北50 km的冷龙岭硫磺沟地区,并在硫磺沟—大西沟一带形成规模大且连续性较好的地表破裂。地表调查显示,同震地表破裂的总长度约为23 km,整体走向N40°~85°W,地表破裂主要由雁列的地震鼓包、张裂缝、剪切裂缝等形式组合而成,而且地表伴生了较多规模不等的滑坡、崩塌等次生地质灾害。根据地表破裂的规模、走向及破裂特点等,可将其分为3段:东段(硫磺沟段),长约10 km,走向N40°~60°W,破裂规模较小,以伴有重力作用的拉张裂缝为主;中段(道沟段),长约9 km,走向N70°W,破裂规模较大,以发育规模较大的地震鼓包和剪切裂缝为主,而且左旋位移较大;西段(大西沟段),长约4 km,走向N85°W,此段规模最小,以雁列的拉张裂缝为主。其中—东段一起组成了该破裂带的东支,而西段构成了西支,两者都具有明显的左旋走滑特征,并自东向西破裂整体呈左阶展布,在G227国道以东形成了具有拉张特征的左阶阶区。综合分析表明,此次,地震发生在祁连山块体的祁连-海原活动构造带,发震断裂应为海原左旋走滑断裂带的冷龙岭-托莱山断裂段。结合对祁连-海原构造带1900年以来强地震序列及托莱山断裂的初步研究认为,该构造带的历史地震活动整体具有不断向西发展的趋势,但在哈拉湖和托莱山之间存在较明显的地震空区,因而推断托莱山断裂未来的强震危险性有增强的可能。

祁连山典型植被土壤有机碳分布特征及其影响因素

探讨祁连山典型植被土壤有机碳空间分布特征及其影响因素,可为评估该地区森林土壤固碳效应提供科学依据。以退耕地为对照,以草地、天然乔木(青海云杉、祁连圆柏)、人工乔木(落叶松)和灌木5种典型植被为研究对象,测定0~100 cm深度土壤有机碳含量、有机碳密度、土壤粒度、pH、电导率、全氮、全钾和全磷含量,比较分析不同植被土壤有机碳组分的分布差异及其主要影响因素。结果表明:1)不同植被类型平均土壤有机碳含量排序为青海云杉(5.99 g/kg)>祁连圆柏(5.59 g/kg)>落叶松(2.91 g/kg)>灌木(1.83 g/kg)>草地(1.66 g/kg)>退耕地(1.16 g/kg);平均土壤有机碳密度排序为青海云杉(3.43 kg/m^(2))>祁连圆柏(2.76 kg/m^(2))>落叶松(2.16 kg/m^(2))>灌木(2.08 kg/m^(2))>草地(2.00 kg/m^(2))>退耕地(1.33 kg/m^(2))。2)随着土层的加深,不同植被土壤有机碳含量整体上呈减小的趋势,土壤有机碳密度呈先增后减的趋势。3)不同植被类型土壤C/N为9.30~15.73,均值表现为青海云杉(14.96)>草地(11.66)>退耕地(11.54)>灌木(10.83)>落叶松(10.69)>祁连圆柏(10.63)。4)不同植被类型土壤有机碳和全氮含量均呈极显著正相关(P<0.01),有机碳与全磷、黏粒、粉粒呈极显著或显著正相关(P<0.01,P<0.05),有机碳与砂粒含量呈极显著或显著负相关(P<0.01,P<0.05),有机碳与pH均呈显著负相关(P<0.05)。祁连山自然生长的乔木土壤有机碳固持能力较好,在建设碳汇林时应充分考虑土壤有机碳的影响,优先选择乔木植被。

中祁连西段余石山铌钽矿含矿地层重新厘定及意义

余石山变粒岩型铌钽矿是近年在中祁连西段发现大型铌钽矿,但对铌钽矿含矿地层归属厘定不清,在梳理前人研究成果基础上,通过野外精细调研和区域对比,重新厘定了这套地层,建议将其从长城纪熬油沟组中解体出来,建立新的岩石地层单位,即新元古代余石山岩组;同时,分析余石山岩组原始层序,总结其形成过程。研究成果为中祁连地块西段地层对比和研究提供了新材料,也为中祁连西段变粒岩型铌钽矿找矿和成矿研究提供了基础。

祁连山中段夏季降雨与对流特征分析

祁连山中段夏季降雨特征研究可为地形云人工增雨提供天气背景依据支撑。基于2015—2017年地面观测资料和FY-2G卫星红外黑体亮度温度(Temperature of Black Body, TBB)逐时资料,分析祁连山中段夏季降雨与对流特征及降雨日变化与局地环流的关系。结果表明:祁连山中段海拔低于3.5 km的气象站降雨量随海拔呈线性递增变化,东部(99.2°E以东)降雨量随海拔的变化较西部剧烈。位于山谷的野牛沟和祁连站山谷风环流和降雨日变化较青海湖畔的刚察站明显,两站降雨最大值和次峰值分别在傍晚和清晨,分别对应该地区两类主要地形云(积雨云和层积云)高频时段,平均雨强分别为2.0~2.3、1.0~1.3 mm·h^(-1)。与河西走廊张掖站相比,在雨强小于1.5 mm·h^(-1)和大于等于1.5 mm·h^(-1)条件下,祁连、野牛沟和刚察站的TBB概率分布峰值从-22~-12℃转为-32~-22℃;在使用TBB<-32℃的降雨云识别阈值时,祁连山地区降雨云的覆盖率低于河西走廊地区;TBB<-22℃阈值更适宜祁连山地区弱对流降雨云的识别。研究区内深对流与浅对流的高值区分别呈现南北向、西北—东南向分布,基于TBB资料的浅对流频率日变化等可反映该地区降雨日变化的部分特征。

天然热释光测量技术在多年冻土区天然气水合物勘查中的应用

冻土区天然气水合物形成机理复杂,成因多源,发展多种捕捉微渗漏信息技术,提高勘查成功率是亟需解决的难题。本文首次把天然热释光测量技术应用于冻土区天然气水合物勘查中,利用RGD-6型热释光剂量仪测试了祁连山冻土区土壤样品热释光强度,总结出适用于木里冻土区天然气水合物勘查的加热程序,以及样品取样粒级。试验结果表明,祁连山冻土区土壤样品最佳取样粒级为-60~100目,最佳升温速率应设置为5℃/s,最佳升温区间为50~400℃。根据祁连山冻土区土壤天然热释光强度异常特征,圈定了天然气水合物在地表的异常边界,天然热释光强度异常模式为顶部异常,与烃类异常模式存在良好的对应关系。土壤天然热释光不受微生物的影响,灵敏度高,是一种很有前景的寻找天然气水合物的方法,在今后的冻土区天然气水合物资源勘查过程中可以将这种技术加以推广。

祁连山国家公园肃南片区生态敏感性评价

生态敏感性评价是反映国家公园生态问题与保护利用关系的重要手段,对国家公园规划建设具有一定的理论和实践指导意义。文章以祁连山国家公园肃南片区为例,基于现存主要生态问题,采用层次分析法(AHP)确定评价因子权重,并运用ArcGIS空间分析方法完成了肃南片区的生态敏感性综合评价。结果表明,祁连山国家公园肃南片区的综合生态敏感性总体处于中等偏高的水平,中等敏感性以上地区占总面积的78.90%;空间分布呈现由东北至西南逐渐增加的趋势。根据祁连山国家公园肃南片区综合生态敏感性评价结果,针对不同敏感性级别的区域提出了差异化的保护管理模式。