Geochemical Characteristics and Tectonic Setting of the Laohushan Basalts, North Qilian Mountains

The Ordovician Laohushan ophiolite, located in the eastern part of the North Qilian Mountains, is mainly composed of meta-peridotites, gabbros and basalts alternating with sediments. The sediments are mainly turbidites, including sandstones, siltstones, cherts etc. Major elements show that the basalts are subalkaline tholeiites and may be analogous to ocean-floor basalts. Except a few N-MORBs, most of the basalts are E-MORBs as indicated by incompatible element ratios such as (La/Ce)N, La/Sm, Ce/Zr, Zr/Y and Zr/Nb. Negative Nb anomaly is common but negative Zr, Hf and Ti anomalies are quite rare. Based on the geochemical characteristics, it is suggested that the Laohushan basalts were formed in a back-arc basin. ENd (t) of the basalts ranges between +3.0 and +8.9 and (87Sr/86Sr), ranges between 0.7030 and 0.7060, indicating a depleted mantle source which was mixed with more or less enriched mantle components. Furthermore, the petrography of the sandstones and geochemistry of the cherts suggest that the sediments were deposited near a continental margin.

From Flysch to Molasse—Sedimentary and Tectonic Evolution of Late Caledonian -Early Hercynian Foreland Basin in North Qilian Mountains

The Late Caledonian to Early Hercynian North Qilian orogenic belt in no rthwestern China is an elongate tectonic unit situated between the North China p late in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to L ate Silurian shallow marine to tidal flat deposits and the Early and Middle Devo nian terrestrial molasse are developed along the corridor Nanshan. The shallowin g upward succession from subabyssal flysch, shallow marine, tidal flat to terre strial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stag e during the Silurian and Devonian time.

Rheological Properties of Mantle Peridotites at Yushigou in the North Qilian Mountains and Their Implicationsfor Plate Dynamics

Abstract: This paper discusses in detail the deformation textures, glide system, petrofabrics and olivine dislocation microstructures of mantle peridotites at Yushigou in the North Qilian Mountains, northwestern China. The peridotites have undergone high-pressure, high-temperature and low-strain rate plastic flow deformation. According to the dynamic recrystallized-grain size of olivine and the average spacing between the dislocation walls as well as the chemical composition of enstatite, the authors calculated the rheological parameters of the ancient upper mantle in the study area as follows: temperatures 1025–1093°C; pressures 3043–4278 MPa; depths 95–132 km; deviatoric stress 28–32 MPa; strain rates 0.2×10?14-2.13×10?14s?1 and equivalent viscosities 0.45×1020-4.65×1020 Pa ? s. These parameters suggest that the position where plastic flow took place was correspondent to the lowvelocity zone beneath the oceanic lithosphere and that oceanization characterized by middle-velocity (1–3 cm/a) sea-floor spreading took place in the North Qilian Mountains during the Early Palaeozoic.

U-Pb Zircon Dating of the Yeniutan Granitic Intrusion in the Western Sector of the North Qilian Mountains

Zircons from granodiorite and biotite granite in the Yeniutan granitic intrusion in the western North Qilian Mountains yielded a weighted mean 206Pb/238U apparent age of 460±3 Ma, suggesting that the intrusion originated during the late stage of plate subduction. Its related Ta'ergou and Xiaoliugou deposits are two of the few large tungsten deposits formed in the plate subduction environment in the world. The U-Pb dating of the zircons from the biotite granite gave a discordant lower intercept age of 183±4 Ma, which implies that the Yanshanian event was probably superimposed on the North Qilian region.

Zircon Geochronology and Trace Element Geochemistry from the Xiaozhen Copper Deposit, North Daba Mountain: Constraints on Albitites Petrogenesis

Albitite often accompanies with various metal and gem mineral deposits and a large number of occurrences have been reported globally, including the South Qinling orogen, China. The Xiaozhen copper deposit is a typical deposit in the North Daba Mountain area of the South Qinling orogen whose distribution is controlled by albitite veins and fractures. As there are few studies on the petrogenesis of albitite in Xiaozhen copper deposit, this paper focuses on the petrogenesis of albitite and its mineralization age. Detailed fieldwork and mineral microscopic observations initially suggest that albitite from the Xiaozhen copper deposit is igneous in origin. Further zircon trace element geochemistry studies indicate that these zircons have high Th/U ratios（〉0.5）, low La content, high（Sm/La）N and Ce/Ce＊values, and a strong negative Eu anomaly, which are commonly seen in magmatic zircons. The chondrite–normalized rare earth element（REE） patterns are consistent with magmatic zircons from throughout the world, and they fall within or near the field of magmatic zircons on discriminant diagrams. The calculated average apparent Ti–in–zircon temperature for young zircons is 780°C, consistent with magmatic zircon crystallization temperatures. Therefore, zircon geochemistry indicates that the albitite origin is magmatic. SIMS U–Pb dating on nine magmatic zircons yielded a concordia age of 154.8±2.2 Ma, which represents the formation of albitite and the metallogenic age. More importantly, it is consistent with the ages of Yanshanian magmatism and metallogenesis in the South Qinling orogen, so formation of the Xiaozhen copper deposit may be a closely related geological event.

Paleosubmarine Volcanism and Mineralization from North Qilian Mountains

This paper summarizes the history of tectono magmatic evolution, the types and backgrounds of mineralization prior to the orogenic period of North Qilian Mountains. It points out that: during the process of Paleozoic ocean basin opening and closing, the large scale marine volcanism and massive sulfide deposits controlled by sea floor hydrothermal circulation systems are the two sharpest features in the geological developing history of the orogenic belt, which are also the most two important aspects related to each other and should be given a special attention in the geological studies in the region.

Geochronology and Geochemistry of the Middle Proterozoic Aoyougou Ophiolite in the North Qilian Mountains,Northwestern China

The Aoyougou ophiolite lies in an early Palaeozoic orogenic belt of the western North Qilian Mountains, near the Aoyougou valley in Gansu Province, northwestern China. It consists of serpentinite, a cumulate sequence of gabbro and diorite, pillow and massive lavas, diabase and chert. Ages of 1840±2 Ma, 1783±2 Ma and 1784±2 Ma on three zircons from diabase, indicate an early Middle Proterozoic age. The diabases and basalts show light rare-earth element enrichment and have relatively high TiO2 contents, characteristic of ocean island basalts. All of the lavas have low MgO, Cr, Ni contents and Mg numbers indicating a more evolved character. They are believed to have been derived from a more mafic parental magma by fractionation of olivine, Cr-spinel and minor plagioclase. Based on the lava geochemistry and regional geology, the Aoyougou ophiolite was probably believed to have formed at a spreading centre in a small marginal basin. Subduction of the newly formed oceanic lithosphere in the Middle Proterozoic produced a trench-arc-basin system, which is preserved in the North Qilian Mountains.

Geochemistry of Rare Earth Elements of Mesozoic-Cenozoic Sandstones in North Margin of Dabie Mountains and Adjacent Areas: Constraints to Source Rocks

Based on the study of REE in Mesozoic-Cenozoic sandstones, the paper indicates that Jurassic Fanghushan and Yuantongshan Formations and Lower Cretaceous Zhougongshan Formation have ∑REE of 157 μg·g^(-1), δ_(Eu) of 0.69 and (La/Yb)_N of 11.1, which are similar to the Foziling and Luzhenguan Groups, and it implies that the latter may be the source rocks of the former. The Sanjianpu and Heishidu Formations have high REE concentrations (∑REE=264.8 μg·g^(-1), 328.2 μg·g^(-1) respectively), high Eu anomaly (δ_(Eu)=0.57, 0.67 respectively) and lower Eu/Sm ratios (0.18～0.19), which differs from existent metamorphic rocks in the Dabie Mountains, so where their source rocks came from remains to be studied. The REE features of the Zhengyangguan Formation can be comparable to the Dabie complex and Luzhenguan Group, which shows that the Dabie complex had suffered unroofing in Neocene and constituted the source rocks. Mesozoic sandstones in Huainan area have lower REE concentrations (∑REE=80.9 μg·g^(-1)), high Eu anomaly (δ_(Eu)=0.66) and (La/Yb)_N of 5.7, and it indicates that their source rocks may not come from the Dabie Mountains.

Slope runoff study in situ using rainfall simulator in mountainous area of North China

Simulated rainfall is a valid tool to examine the runoff generation on the slope.13 simulated rainfall experiments with different rainfall intensities and durations are completed in a 5 m ×10 m experimental plot in mountainous area of North China.Simultaneously,rainfall,surface runoff,soil-layer flow,mantel-layer flow and soil moisture are monitored respectively.From the results,it is found that the hydrographs in all layers have the characteristics of rapid rise and fall.The recessions of surface flow and soil-layer flow are much faster than that of mantel-layer flow.Surface flow,the main contributor,makes up more than 60% of the total runoff in the study area.It even exceeds 90% in the cases of high intensity rainfall events.Runoff coefficient(ratio of total runoff to rainfall amount) is mainly influenced by rainfall amount,rainfall intensity and antecedent soil moisture,and the relationship can be well expressed by a multiple linear regression function α = 0.002P + 0.182i + 4.88Wa-0.821.The relation between the rainfall intensity and the lag time of three flows(surface runoff,soil-layer flow and mantel-layer flow) is shown to be exponential.Then,the result also shows that the recession constant is 0.75 for surface runoff,is 0.94 for soil-layer and mantel-layer flow in this area.In this study area,the dominant infiltration excess runoff is simulated by Horton model.About 0.10 mm/min percolation is observed under the condition of different rainfall intensities,therefore the value is regarded as the steady infiltration rate of the study area.

Petrogenesis and Significance of the Jebel Dumbier Alkaline-Carbonatite Complex from North Margin of Nuba Mountains, Sudan

1 Introduction Scientific study of the geology and mineral resources in Sudan is rather limited.Jebel Dumbier is the first identified carbonatite-bearing alkaline complex in Sudanby El Sharkawi&El Raba’a in 1973.It is located in Northern Kordofan Province on the northeastern margin of the Nuba Mountains.The complex exposed as small

北天山西段库松木楔克山山前断层新活动特征初探

库松木楔克山山前断层是位于北天山西段再生造山带北缘一条重要的边界断层，是本次新发现和确定的一条活动断层。断层分为东、中、西三段：东段主要由4条断层斜列组合而成，单条断层长度为9～13km，在晚更新世～全新世仍在强烈活动，晚更新世以来的垂直错动量为3～4m，垂直活动速率为0．23～0．33mm／a，全新世以来的垂直错动量为0．5～0．8m；中段断层活动错断了中更新世至全新世地貌，形成多级断层陡坎和长约8～10km的地震形变带，晚更新世以来垂直活动速率为0．5mm／a；西段自晚更新以来无活动显示。

天山北坡2次暴雪过程机理分析

利用FNL及常规资料,对比分析了2010年2月22—24日(过程Ⅰ)和2015年12月10—13日(过程Ⅱ)天山北坡2次暴雪过程。结果表明,暴雪区上空θse锋区陡立和条件性对称不稳定及次级环流是形成暴雪的主要机制。不同点是:过程Ⅰ暴雪产生在西西伯利亚低涡底部强锋区上,南北支短波槽汇合的区域,冷高压为西北路径;过程Ⅱ是乌拉尔山大槽东移北收,冷高压为偏西路径;2次过程在温压的时间演变上有显著的区别。在高低空配置上也有明显的区别:过程Ⅰ 500 hPa以下为暖平流,以上为冷平流,低层为暖湿结构;过程Ⅱ 700 hPa以下为冷平流,700—600 hPa为暖平流,低层有湿冷空气锲入。过程Ⅰ暴雪区位于θse锋区上,锋区低层强,中高层弱;过程Ⅱ暴雪区位于θse锋区中后部,锋区低层弱,中高层强。水汽输送和输入量及比湿过程Ⅰ大于过程Ⅱ。

北部山前带致密砂岩气层识别方法研究

致密砂岩气是吐哈油田未来油气增长的主攻领域之一,吐哈盆地致密砂岩气勘探的优势是点多、面广、厚度大,勘探前景十分广阔;但是物性普遍偏差、非均质性强、埋深较大;尤其是电性特征复杂,气层的准确识别比较困难。采用非电法的技术手段开展致密砂岩气层识别,能够避免岩性及孔隙结构的影响,应用中子-密度(声波)重叠法和偶极声波测井处理得到的纵波、泊松比等资料,结合地质及录井信息开展北部山前带致密砂岩气层判别,提高了解释符合率,取得了良好的效果。

吐哈盆地致密砂岩气勘探前景与关键问题讨论

吐哈盆地北部山前带柯柯亚地区的巴喀下侏罗统气藏具有储层致密、基质孔隙储气、气层厚度大、连片广、"甜点"与构造裂缝和沉积微相密切相关等致密砂岩气典型特征。吐哈聚煤盆地烃源岩条件优越,发育与煤系源岩间互的大型沉积砂体,台北凹陷主体持续沉降,烃源岩持续演化排烃,有利于源内大型致密砂岩气藏的形成。进一步总结认识致密砂岩气高产富集规律,整体评价全盆地致密砂岩气资源潜力,攻关突破"甜点"预测描述技术,是下一步勘探需要解决的关键问题。

论新疆深大断裂特征与地震的关系(3)

北天山山前地带是构造运动十分强烈的地区,褶皱断裂等构造现象十分发育,这里曾发生过多次中强破坏性地震。由于受区域构造长期作用的影响,在北天山山前地区逐步发育形成了多排褶皱背斜及活动断裂,且运动方式具有独特性。该区域作为推覆逆冲的典型地区,其研究成果具有代表性和普遍性。

东满反日游击队与抗日义勇军的关系探析

东满延吉、汪清、珲春、和龙四县反日游击队在党的领导下,积极贯彻抗日统一战线政策,联合并团结东满抗日救国军、山林队等义勇军部队共同抗日,并在建立统一战线过程中,因地制宜地针对情况各异的义勇军采取不同的策略,并在义勇军部队中建立党组织,使广大义勇军部队逐步接受党的领导。

348-YEAR PRECIPITATION RECONSTRUCTION FROM TREE-RINGS FOR THE NORTH SLOPE OF THE MIDDLE TIANSHAN MOUNTAINS

Correlation census shows that the correlation between the tree-ring chronologies in the Urumqi River Basin and precipitation during July in the last year to February in the concurrent year is significant,and the best single correlation coefficient is 0.74,with significance level of 0.0001. Using two residual chronologies collected from west Baiyanggou and Boerqingou,precipitation for 348 years can be reconstructed in the North Slope of middle Tianshan Mountains,its explained variance is 62%.According to much verification from independent precipitation data,historical climate records,glacier and other data.it shows that the reconstructed precipitation series of 348 years is reliable.Analysis of precipitation features indicates that there were three wet periods occurring during 1671(?)—1692,1716—1794 and 1825—1866 and three dry periods during 1693 —1715,1795—1824 and 1867—1969.Two wet periods,during 1716—1794 and 1825—1866, correspond to the times of the second and the third glacial terminal moraine formation,which is in front of No.1 glacier in Urumqi River source.According to computation,corresponding annual precipitation amounts are 59mm and 30mm more than now.The reconstructed precipitation series has a significant drying trend from 1716 to 1969.and has better representativeness to the precipitation of Urumqi and Changji Prefecture on the North Slope of Tianshan Mountains.

Apatite Fission Track Constraints on the Pattern of Faulting in the North Qilian Mountain

The Qilian （祁连） Mountain is an active orogenic belt located at the northeastern margin of the Tibetan Plateau. During the process of continuous convergence between Indian and Eurasian plates, the Qilian Mountain grow correspondingly by means of reaction of old faults and generation of new ones. Here we present apatite fission-track data along a river profile crossing three minor fault （the Minle （民乐）-Damaying （大马营） fault, the Huangcheng （皇城）-Taerzhuang （塔尔庄） fault and the Kangningqiao （唐宁桥） fault） which compose the North Qilian fault （NQF） to test the timing and pat- terns of the fault activities. Apatite fission-track （AFT） results indicate that these minor faults expe- rienced two active phases in the Cretaceous and the Oligocene-Miocene. Further research indicate that the initiation timing of faulting became younger northward in both active periods and the later phase probably more active than the former phase. These tectonic activities might be highly related to the docking of the Lhasa Block to the south in the Cretaceous and uplift and expansion of the Tibetan Pla- teau in the Cenozoic.

Spatio-temporal correlation between human activity intensity and land surface temperature on the north slope of Tianshan Mountains

Research on the spatio-temporal correlation between the intensity of human activities and the temperature of earth surfaces is of great significance in many aspects,including fully understanding the causes and mechanisms of climate change,actively adapting to climate change,pursuing rational development,and protecting the ecological environment.Taking the north slope of Tianshan Mountains,located in the arid area of northwestern China and extremely sensitive to climate change,as the research area,this study retrieves the surface temperature of the mountain based on MODIS data,while characterizing the intensity of human activities thereby data on the night light,population distribution and land use.The evolution characteristics of human activity intensity and surface temperature in the study area from 2000 to 2018 were analyzed,and the spatio-temporal correlation between them was further explored.It is found that:(1)The average human activity intensity(0.11)in the research area has kept relatively low since this century,and the overall trend has been slowly rising in a stepwise manner(0.0024·a-1);in addition,the increase in human activity intensity has lagged behind that in construction land and population by 1-2 years.(2)The annual average surface temperature in the area is 7.18℃with a pronounced growth.The rate of change(0.02℃·a-1)is about 2.33 times that of the world.The striking boost in spring(0.068℃·a-1)contributes the most to the overall warming trend.Spatially,the surface temperature is low in the south and high in the north,due to the prominent influence of the underlying surface characteristics,such as elevation and vegetation coverage.(3)The intensity of human activity and the surface temperature are remarkably positively correlated in the human activity areas there,showing a strong distribution in the east section and a weak one in the west section.The expression of its spatial differentiation and correlation is comprehensively affected by such factors as scopes of human activities,manifestations,and land-use changes.Vegetation-related human interventions,such as agriculture and forestry planting,urban greening,and afforestation,can effectively reduce the surface warming caused by human activities.This study not only puts forward new ideas to finely portray the intensity of human activities but also offers a scientific reference for regional human-land coordination and overall development.

北天山山前地带垂直形变特征及其与地震的关系

根据垂直形变资料分析，北天山山前地带的垂直形变具有继承性运动特征，天山山体继续上升，盆地继续下降，在空间上具有统一性，在时间上具有同步性。１９８０年天山北缘石河子南５．８级地震，震前的正向加速形变转为反向形变，为预报北天山地震带的强震提供了时间依据；反向形变异常最大的地段，是未来发生强震的可能地点。