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 in- truded 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 environ- ment 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 subduc- tion 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 evolu- tionary stage． The zircon U-Pb SHＲIMP isotopic apparent age of the complex in Highland 1248 is 140． 0--141. 0 Ma,and the formation time is in Early Cretaceous．     

Geochronology,geochemistry and geological significance of Early Cretaceous volcanic rocks from Niangniangshan Formation,Ningwu Basin,middle and lower reaches of the Yangtze River

Ningwu Basin is one of the Mesozoic continental volcanic basins in the middle and lower reaches of the Yangtze River.The volcanic rocks of the Longwangshan,dawangshan,Gushan and Niangniangshan formations,as well as the homologous subvolcanic rocks or small intrusions,are developed from old to new in the Ningwu Basin.Zircon U-Pb dating results show the latialite phonolite of Niangniangshan Formation was erupted at 128±1 Ma(i.e.,Early Cretaceous).The latialite phonolite contains moderate SiO2 contents(57.28%-60.96%)with high Na 2O+K 2O contents,belonging to shoshonite series.The samples have high REE contents,and display right-inclined REE distribution pattern.They are characterized by enrichment in some large ion lithophile elements(e.g.,LILEs,Rb,K),and depletion in some high field strength elements(e.g.,HFSEs,Nb,Ta,Ti).All volcanic samples have relatively depleted Nd isotopic compositions(ISr=0.707197--0.707878;εNd(t)=-0.5--0.9),indicating no genetic relationship with the lower crust of Yangtze plate,but a drift trend towards the EMII.The geochemical data suggest that the Early Cretaceous latialite phonolite was derived from the partial melting of an enriched lithospheric mantle metasomatized by subduction-related fluids in an arc-related setting.Based on the temporal and spatial distribution and geochemical variation characteristics of the regional volcanic rocks,it is suggested that the tectonic system within the study area changed from a subduction-related compression to an extensional environment in the early Early Cretaceous,which was caused by the ridge subduction of the Paleo-Pacific Ocean.     

Active tectonics and erosional unloading at the eastern margin of the Tibetan Plateau

Introduction The eastern margin of the Tibetan Plateau, adjacent to the Sichuan Basin (Figure 1), has become a testing ground for a variety of models that contrast mechanisms of extrusion and crustal thickening associated with the India-Asia collision (Avouac and Tapponnier 1993, England and Houseman 1986),but that also address the extent to which the upper crust and upper mantle are coupled (Royden et al. 1997, Holt 2000). The margin is characterized by topographic relief of over 5 km an…     

Geochemical characteristics and sedimentary environment significance of carbonate rocks in Nanfen Formation of Qingbaikou System in Tonghua,Jilin Province

In order to reveal the sedimentary environment of carbonate rocks in Nanfen Formation of Qingbaikou System in Tonghua, Jilin Province, the mineral composition and petrochemistry of carbonate rocks in Nanfen Formation were analyzed. The mineral compositions of five carbonate rock samples in Nanfen Formation mainly consist of calcite, with minor clay minerals and quartz, and the rock type is siliceous marlite. The Mn/Sr va-lues range from 1.52 to 4.08, with an average of 2.64, indicating that the carbonate rocks experienced weak diagenesis; the Sr/Ba values range from 1.26 to 2.51, with an average of 1.93, indicating marine environment; the ratio of Mg/Al ranges from 35.33 to 86.34, with an average of 62.95, indicating the seawater environment, which is consistent with the result from Sr/Ba; the MgO/CaO values range from 0.01 to 0.04, with an average of 0.02, indicating humid environment; the values of V/(V+Ni) range from 0.63 to 0.73, with an average of 0.70, indicating anoxic environment. In summary, geochemical analyses show that the Nanfen Formation carbonate rocks are marine deposits, in a warm, humid, anoxic environment with poor flow of seawater, and subsequently underwent weak diagenetic alteration.     

西秦岭糜署岭岩浆混合花岗岩地球化学特征及构造意义

西秦岭糜署岭岩体是壳幔岩浆混合的产物。从寄主岩石和基性端元暗色微细粒镁铁质包体的主要元素、稀土元素岩石地球化学研究入手，深入探讨了糜署岭岩体是壳源和幔源两类岩浆混合形成的混浆花岗岩，其岩石地球化学特征介于壳源和幔源两个端元之间并有显著的过渡特征，表明二者在岩浆侵位过程中发生过不同程度地物质成分交换。这对研究西秦岭中生代壳幔混合作用和地壳增生有重要意义。     

Zircon U-Pb geochronology,geochemistry and tectonic implication of volcanic rocks from Manketouebo Formation in Keyihe area of northern Great Xing'an Range

Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite, rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area, in order to constrain their genesis and tectonic significance. Zircon LA-ICP-MS U-Pb data indicate that the rhyolite and rhyolitic lithic crystal tuff were formed during 137±5 Ma and 143±1 Ma,respectively. These volcanic rocks have high SiO₂(70.03%–76.46%) and K₂O+Na₂O(8....     

Discovery of Late Permian Jianshanzi volcanic rocks in Qinghe valley of northern Liaoning and its geologic significance

Jianshanzi volcanic rocks at Qinghe valley in the northern Liaoning were considered belonging to Early Proterozoie Gaojiayu Formation of Liaohe Group, or to Early Cambrian Beidagou Formation of Qinghezhen Group, or Middle-Late Proterozoic Shenjiapu Formation-Complex of Kaiyuan Group-complex. Dating the zircons from the dacite with schistosity is 2 506 Ma in method of U-Pb （SHRIMP）. This evidence indicates the rocks may be referred to Late Permian in age. Discovery of the rocks is significant to re-recognize stratigraphic property of ＂Liaohe Group＂, regional geoteetonie location and revolution of orogenic zone in Qinghe valley of the northern Liaoning.     

Discovery of Late Permian Jianshanzi volcanic rocks in Qinghe valley of northern Liaoning and its geologic significance

Jianshanzi volcanic rocks at Qinghe valley in the northern Liaoning were considered belonging to Early Proterozoic Gaojiayu Formation of Liaohe Group, or to Early Cambrian Beidagou Formation of Qinghezhen Group, or Middle-Late Proterozoic Shenjiapu Formation-Complex of Kaiyuan Group-complex. Dating the zircons from the dacite with schistosity is 2 506 Ma in method of U-Pb (SHRIMP). This evidence indicates the rocks may be referred to Late Permian in age. Discovery of the rocks is significant to re-recognize stratigraphic property of "Liaohe Group", regional geotectonic location and revolution of orogenic zone in Qinghe valley of the northern Liaoning.     

Geochemistry of Neoproterozoic mixosedimentite in northern Anhui and its geological significance

Major oxides,as well as trace elements (including rare earth elements) compositions have been analyzed for the mixosedimentites from Neoproterozoic Jiayuan Formation in northern Anhui,China.The results show that the concentrations of elements are closely related to the relative proportions of carbonates and terrigenous detritus (varying from 2/3 to 1/9 based on petrographic study).The ratios between some immobile elements (e.g.La,Th,Zr and Sc) are constant and then can be used as tracers for the discrimination of provenance and tectonic setting of terrigenous detritus.The results indicate that the terrigenous detritus mainly came from the felsic volcanics related to continental arc,with minor contribution from the old basement.Combined with recent research progresses,these mixosedimentites imply that the Neoproterozoic sedimentation in northern Anhui was probably taken place in a back arc basin during the convergence of Rodinia super continent between 1.0 and 0.8 Ga.     

Petrogenesis of high-Mg# Cenozoic volcanic rocks of southern Qiangtang area,Tibetan Plateau: geochemical and Sr-Nd isotopic evidence

The Nadingcuo volcanic rock suite is the most voluminous Cenozoic volcanic suite in the southern Qiangtang area of the northern Tibetan Plateau. These high-K calc-alkaline volcanic rocks were formed between36 and 34 Ma,characterized by high Mg#values,high concentrations of Ti O2 and P2O5,87 Sr /86 Sr ratios of0. 704682--0. 706 112,and εNd( t) values of- 1. 2 to 1. 6. There is a lack of reasonable explanations for sourcing and origin of magmas that formed the rocks with high Mg#values and Ti O2 and P2O5enrichments,which makes the previous research results still controversial. This study reviews the geochemical characteristics of Nadingcuo volcanic rocks and the data we have newly found in our fieldwork. We give some new interpretation to the magmatic evolution of the basaltic magmas in the discussed area dominated by fractional crystallization.The geochemistry of trachyandesite and trachyte units in the studied area is indicative of formation from mantlederived magmas that mixed with crustal materials. The high values of Mg#and Ti O2 and P2O5enrichment in these units are evident to show the mixing between mantle-derived magmas with ~ 30--40 wt.% rhyolitic melt or assimilation of a similar amount of felsic rocks. The geochemistry of basaltic rocks in the area also suggests that the Nadingcuo basalts may have been derived from an ocean island basalt( OIB)-type source that contained and was mixed with ancient mantle wedge derived material,indicating that a 36--34 Ma asthenospheric upwelling event in the Qiangtang area may relate to the northward subduction of Indian lithospheric mantle and the southward subduction of Asian lithospheric mantle. This upwelling of asthenospheric material was centered in the southern Qiangtang area between 36 and 34 Ma,while the northward movement of the Indian Craton caused this upwelling mantle flow to continuously migrate northward,resulting in the current centering of this upwelling in the Hoh Xil-Kunlun region.     

青藏高原冬季植被变化与南亚夏季风关系分析

利用1982年1月-2001年12月青藏高原植被归一化指数(NDVI)和NCEP/NCAR再分析月平均资料,应用相关分析、奇异值分解(SVD)和经验正交分解(EOF)的方法,分析了青藏高原冬季的NDVI变化与南亚夏季风的关系.通过分析表明,高原植被与南亚地区850hPa纬向风场和纬向风垂直切变(U850hPa-U200hPa)有比较好的正相关关系.用纬向风垂直切变EOF分析的第一特征向量对应的时间系数定义一个南亚夏季风指数(EOFI),该系数与高原冬季NDVI相关较好,而且能较好地反映南亚夏季风的变化.     

阿拉善地块南缘构造活动特征与青藏高原东北缘向外扩展的最新边界

青藏高原向北东方向扩展的方式及最新扩展边界的位置,是目前青藏高原东北缘构造变形研究的热点.基于近年来对阿拉善地块南缘及邻区活动构造运动特征调查和定量研究结果,重点总结了阿拉善地块南缘活动断裂几何图像及运动特征,指出以前普遍认为的稳定阿拉善地块内部在新生代晚期发育了一系列规模不等、运动性质各异的活动断裂,这些活动断裂是青...     

Seasonal and Spatial Variability of Microparticles in Snowpits on the Tibetan Plateau, China

The work presents microparticle concentrations in snowpits from the East Rongbuk Glacier on Mt. Qomolangma (Everest) (ER) (28.02°N, 86.96°E, 6536 m a.s.l.), the Zhadang Glacier on Mt. Nyainqentanglha (NQ) (30.47°N, 90.65°E, 5800m a.s.l.), and the Guoqu Glacier on Mt. Geladaindong (GL) (33.95°N, 91.28°E, 5823m a.s.l.) over the Tibetan Plateau (TP). Variations of microparticle and major ions (e.g. Mg2+, Ca2+) concentrations in snowpits show that the values of the microparticles and ions in the non-monsoon seasons are much higher than those in the monsoon seasons. Annual flux of microparticle deposition at ER is lower than those at NQ and GL, which could be attributed to the long distance away from the possible dust source regions as well as the elevation for ER higher than the others. Compared with other remote areas, microparticle concentrations in the southern TP are much lower than those in the northern TP, but still much higher than those in Greenland and Antarctica. The seasonal and spatial microparticle variations are clearly related to the variations of atmospheric circulation according to the air mass 5-day backward trajectory analyses of HYSPLIT Model. Resultingly, the high microparticle values in snow are mainly attributed to the westerlies and the strong dust storm outbreaks on the TP, while the monsoon circulation brings great amount of precipitation from the Indian Ocean, thus reducing in the aerosol concentrations.     

青藏高原城镇化格局的时空分异特征及影响因素

研究青藏高原城镇化格局的时空分异及其影响因素,有利于推动青藏高原现代人类活动时空过程的认知,对青藏高原就地就近城镇化及可持续发展具有参考意义。根据历次人口普查数据,本研究构建青藏高原县市尺度城镇化空间数据集,参考城镇化发展阶段,采用LISA空间类型划分法和空间计量回归模型,系统分析1990-2010年青藏高原内部城镇化格局的时空分异特征及影响因素。主要结论包括：① 青藏高原整体城镇化水平偏低,2017年底,青藏高原主体部分青海省和西藏自治区的常住人口城镇化水平分别为53.07%和30.8%,低于全国同期水平的58.52%,但青藏高原内不乏高水平城镇化地区,而且各地区间城镇化水平的空间差异缩小;② 青海西部柴达木盆地是高水平城镇化集聚区,羌塘地区是低水平城镇化集聚区,地级行政中心所在县市多呈现自身高、周边低的城镇化格局;③ 与内地相似,第二、三产业从业机会是推动青藏高原城镇化发展重要因素,社会公共服务资源对城镇化拉动作用开始凸显。研究结果可以为青藏高原人类活动研究和青藏高原就地就近城镇化可持续发展政策提供参考。     

青藏高原东南缘碰撞造山结构与物质组成:来自岩石地球化学和地球物理的联合约束

青藏高原东南缘位于印度板块与欧亚板块侧向汇聚部位,是检验碰撞造山动力学模型的理想场所。尽可能全面收集该区已有地球物理和新生代岩浆岩数据,探讨这些资料对碰撞造山带结构和物质组成的指示。结果表明:青藏高原东南缘不同部位的壳幔结构和组成存在较大差异。兰坪—思茅地块、保山地块和腾冲地块等的中地壳(15~30 km深度)普遍发育低速层,表明富水层或者部分熔融物质的存在,为青藏高原物质向东南流动提供了可能。部分熔融产物以大型剪切带内具有高Sr、低Nd同位素特征的淡色花岗岩脉为代表。但是,扬子板块同等深度下却发育高速层,其组成很可能是峨眉山玄武岩,它的存在阻隔了碰撞带物质向东流动。扬子板块和兰坪—思茅地块下地壳底部均出现呈条带状展布的高速体。根据新生代具有高Sr、低Y的岩石显示的下地壳源区特征,结合该区地质演化历史,将上述两套呈条带状展布的高速体分别解释为新元古代铁镁质弧岩浆岩和二叠纪—三叠纪铁镁质弧岩浆岩。青藏高原东南缘地幔各向异性存在明显南、北分区特征,在26°N以北表现为SN向,在26°N以南表现为近EW向。这一差异跟俯冲的印度板片撕裂有密切关系。该撕裂在综合地球物理剖面上显示为突变的印度板片俯冲角度,在地表表现为苦橄岩、煌斑岩、埃达克岩以及淡色花岗岩等的集中出露。这一新模型明显区别于前人的岩石圈拆沉和对流减薄等作用。     

Monitoring glacier and supra-glacier lakes from space in Mt. Qomolangma region of the Himalayas on the Tibetan Plateau in China

Because of the large number and remoteness, satellite data, including microwave data and optical imagery, have commonly been used in alpine glaciers surveys. Using remote sensing and Geographical Information System （GIS） techniques, the paper presents the results of a multitemporal satellite glacier extent mapping and glacier changes by glacier sizes in the Mt. Qomolangma region at the northern slopes of the middle Himalayas over the Tibetan Plateau. Glaciers in this region have both retreated and advanced in the past 35 years, with retreat dominating. The glacier retreat area was 3.23 km2 （or o.75 km^2 yr^-1 during 1974 and 1976, 8.68 km^2 （or 0.36 km^2 yr^-1 during 1976 and 1992, 1.44 km^2 （or 0.12 km^2 yr^-1） during 1992-2ooo. 1.14 km^2 （or 0.22 km^2 yr^-1 during 2000-2003, and 0.52 km^2 （or 0.07 km^2 yr^-1 during 2003-2008, respectively. While supra-glacier lakes on the debris-terminus of the Rongbuk Glacier were enlarged dramatically at the same time, from 0.05 km^2 in 1974 increased to 0.71 km^2 in 2008, which was more than 13 times larger in the last 35 years. In addition, glacier changes also showed spatial differences, for example, glacier retreat rate was the fastest at glacier termini between 5400 and 5700 m a.s.l than at other elevations. The result also shows that glaciers in the middle Himalayas retreat almost at a same pace with those in the western Himalayas.     

青藏高原旅游经济与生态环境协调效应测度及交互胁迫关系验证

青藏高原地区壮美的自然风光、神奇的人文景观和独特的民族文化,使其成为国内外旅游者倾心向往的世外桃源,亟需进一步探究其旅游经济与生态环境之间的交互耦合关系。本文创建青藏高原旅游经济与生态环境综合评价指标体系,采用青海省和西藏自治区15个地市州2000-2017年面板数据探究旅游经济与生态环境协调效应及交互胁迫关系。结果显示： ① 2000-2017年青藏高原仅有拉萨和西宁旅游经济指数呈现快速增长趋势,其余地市州均呈现缓慢增长趋势,生态环境指数整体较高,仅有西宁和海东呈现波动增长趋势,其余地市州变化平缓;② 青藏高原旅游经济与生态环境复合系统协调度时序上呈现波动增长趋势,空间上呈现南高北低、东高西低的分布格局;青海呈现以西宁为核心,逐层向外递减的核心-边缘空间格局;西藏呈现以拉萨为中心,南高北低的空间格局;③ 青藏高原复合系统协同效应子类型主要是旅游经济滞后型,西宁和拉萨呈现“旅游经济滞后-系统均衡发展-生态环境滞后”的变化趋势;④ 基于双指数模型证实了青藏高原旅游经济与生态环境之间具有交互胁迫关系。     

Sedimentary environment of Middle Permian Zhesi Formation in Solon area of Inner Mongolia

Through a sampling analysis of trace elements and REE in the section of Middle Permian Zhesi For- mation in Solon area of Inner Mongolia, it is found that the overall sandstone and mudstone samples are charac- terized by LREE-enrichment. By analysis of the discriminant index of the sedimentary environment, the tectonic setting of Zhesi Formation is determined to be a continental island arc environment. Meanwhile, according to the sedimentary structure and lithology combination, Zhesi Formation is divided into the neritic-bathyal reten- tion-reduction environment as well as the delta front and prodelta sedimentary systems.     

3种土壤冻融判别算法在青藏高原的分类精度评价

本文比较了基于AMSR-E被动微波数据的3种土壤冻融判别算法在青藏高原相关地区的分类精度。3种算法分别是：双指标算法、决策树算法、判别函数算法。本文选取了来自青藏高原那曲、玛曲、阿里3个地区土壤温湿度观测网的地表温度数据,并结合AMSR-E被动亮温数据,对上述算法在以上地区的分类精度分别进行了比较评价。结果表明：不论是白天还是夜间,相较于干旱区微波信号来自深层土壤的难以准确探测,在青藏高原半湿润半干旱区算法可取得相对较好的判别准确率;双指标算法相较于其他2种算法,在观测区具有较高的分类精度,且夜间分类精度高于白天;实测数据存在资料代表性不普遍即网格所包含站点信息量不够的问题,这也是后续工作中提高分类精度值得关注的着手点。     

安徽南陵—宣城地区岩浆岩锆石U-Pb年龄及元素地球化学特征

安徽南陵-宣城地区是一个中-新生代火山-沉积盆地,位于长江中下游构造-岩浆-成矿带东北段的东南翼。对该区发育的岩浆岩开展了较为系统的LA-ICP-MS锆石U-Pb定年及岩石主量、微量和稀土元素分析,并与长江中下游构造-岩浆-成矿带其他地区岩浆岩进行对比,旨在确定岩浆岩的成岩时代、探讨岩浆岩成因及其与成矿的关系。南陵-宣城地区岩浆岩一部分侵入于盆地基底中,另一部分喷发形成盆地盖层,还有一部分产于盆地之上的推覆构造(体)中。侵入岩的岩性主要为花岗岩、花岗闪长岩、石英闪长岩、辉石闪长岩等,火山岩主要为英安质火山碎屑岩和熔岩。获得的侵入岩锆石U-Pb年龄主要为138~135 Ma,火山岩年龄均小于134 Ma,表明岩浆作用发生于晚中生代(燕山晚期)早白垩世。岩浆岩主量元素显示高Si、K的特征,为亚碱性高钾钙碱性系列岩石;微量元素组成显示岩浆岩富集Rb、Th、U、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,火山岩比侵入岩较为亏损Sr和P;球粒陨石标准化稀土元素配分模式均表现为富集轻稀土元素的右倾模式和较弱的Eu负异常。元素地球化学特征指示区内岩浆岩具有壳幔混源且以幔源为主的特征。南陵-宣城地区既发育与长江中下游构造-岩浆-成矿带隆起区(如铜陵地区)同位素地质年龄和地球化学特征基本一致的侵入岩,又发育与凹陷区(如庐枞、宁芜等盆地)同位素地质年龄和地球化学特征基本一致的火山-次火山岩,显示该区晚中生代岩浆作用具有长江中下游构造-岩浆-成矿带隆起区和凹陷区的双重特征。岩浆作用的双重特征暗示与其有关的成矿作用也可能具有双重性,即既可能发育与隆起区侵入岩浆作用有关的斑岩型、矽卡岩型和脉型铜金等多金属矿床,也可能发育与凹陷区火山-次火山岩有关的玢岩型铁(硫)矿床。