基于改进Basin-Hopping Monte Carlo算法的Fe_n-Pt_m(5≤n+m≤24)合金团簇结构优化

合金纳米团簇可以充分利用多种金属的协同效应来实现材料的多功能特性,因而备受关注.本文利用改进的Basin-Hopping Monte Carlo算法研究了不同尺寸和不同比例下的Fe-Pt二元合金团簇的结构稳定性.为证明初始结构相关性,引入了相似函数来分析合金团簇稳定结构与其对应的单金属团簇结构之间的相似性,并分析了Fe-Pt合金团簇在稳定结构下的元素分布.研究结果表明:对于N≤24的Fe-Pt含金团簇,其结构并没有随原子数的增长呈现出明显的形状变化.但是就原子分布而言,对于相同尺寸下不同比例的原子结构,Fe元素趋向于分布在外层,而Pt元素更趋向于分布在内层;对于相同比例不同尺寸的原子结构也得到了同样的结论,并且在Fe原子比例越大的情况下,这种趋向的分布越明显.此外,通过计算合金团簇与单一金属团簇的结构相似函数,发现N≤24的Fe-Pt合金团簇在吸收Fe单金属和Pt单金属基态结构的基础上,随着元素比例的变化,发生了不同于单金属基态结构的变化,并且不同比例结构差异较大.最后,通过计算Fe-Pt合金团簇能量的二阶有限差分值,在Fe-Pt表现出分离结构状态时找到了相对稳定度最好的稳定结构.

Basin-and Mountain-Building Dynamic Model of “Ramping-Detachment-Compression” in the West Kunlun-Southern Tarim Basin Margin

Analysis of the deformation structures in the West Kunlun-Tarim basin-range junction belt indicates that sediments in the southwestern Tarim depression were mainly derived from the West Kunlun Mountains and that with time the region of sedimentation extended progressivdy toward the north. Three north-underthrusting （subducting）, steep-dipping, high-velocity zones （bodies） are recognized at depths, which correspond to the central West Kunlun junction belt （bounded by the Kiida-Kaxtax fault on the north and Bulungkol-Kangxiwar fault on the south）, Quanshuigou fault belt （whose eastward extension is the Jinshajiang fault belt） and Bangong Co-Nujiang fault belt. The geodynamic process of the basin-range junction belt generally proceeded as follows： centering around the magma source region （which largely corresponds with the Karatag terrane at the surface）, the deep-seated material flowed and extended from below upward and to all sides, resulting in strong deformation （mainly extension） in the overlying lithosphere and even the upper mantle, appearance of extensional stress perpendicular to the strike of the orogenic belt in the thermal uplift region or at the top of the mantle diapir and localized thickening of the sedimentary cover （thermal subsidence in the upper crust）. Three stages of the basin- and mountain-forming processes in the West Kunlun-southern Tarim basin margin may be summarized： （1） the stage of Late Jurassic-Early Cretaceous rampingrapid uplift and rapid subsidence, when north-directed thrust propagation and south-directed intracontinental subduction, was the dominant mechanism for basin- and mountain-building processes; （2） the stage of Late Cretaceous-Paleogene deep-level detachment-slow uplift and homogeneous subsidence, when the dominant mechanism for the basin- and mountain-forming processes was detachment （subhorizontal north-directed deep-level ductile shear） and its resulting lateral propagation of deep material; and （3） the stage of Neogene-present compression-rapid uplift and strong subsidence, when the basin- and mountain-forming processes were simultaneously controlled by north-vergent thrust propagation and compression. The authors summarize the processes as the “ramping-detachment-compression basin- and mountain-forming dynamic model”. The basin-range tectonics was initiated in the Late Jurassic, the Miocene-Pliocene were a major transition period for the basin- and mountain-forming mechanism and the terminal early Pleistocene tectonic movement in the main laid a foundation for the basin-and-mountain tectonic framework in the West Kunlun-southern Tarim basin margin.

Polyphase Tectonic Events and Cenozoic Basin-Range Coupling in the Tianshan Belt,Northwestern China

Studies show that the Tianshan orogenic belt was built in the late stage of the Paleozoic, as evidenced by the Permian red molasses and foreland basins, which are distributed in parallel with the Tianshan belt, indicating that an intense folding and uplifting event took place. During the Triassic, this orogenic belt was strongly eroded, and basins were further developed. Starting from the Jurassic, a within-plate regional extension occurred, forming a series of Jurassic-Paleogene extensional basins in the peneplaned Tianshan region. Since the Neogene, a collision event between the Indian and the Eurasian plates that took place on the southern side of the Tianshan belt has caused a strong intra-continental orogeny, which is characterized by thrusting and folding. Extremely thick coarse conglomerate and sandy conglomerate of the Xiyu Formation of Neogene System were accumulated unconformably on the Tianshan piedmont. Studies have revealed that the strong compression caused by the Indian-Eurasian collision had a profound influence over the orogenic belt in the hinterland, and MesozoiC-Cenozoic brittle deformed structures superposed on the ductile deformed Paleozoic rocks. The Mesozoic extensional basins were converted into Cenozoic compressional basins. The deformation in the basins is featured by step thrusts and fault-related folds. Statistics of joints show that the principal compressive stress since the Neogene is in a N-S direction. Meanwhile, owing to the underthrusting of the basin toward the orogenic belt, the Paleozoic strata were thrust on the Meso-Cenozoic rocks as tectonic slices, revealing distinct kinematic features in different geologic units. The basin-range coupling zones are characterized by intensive compression, folding and thrusting, accompanied by local sub-E-W-trending strike-slip faults. In the Tianshan region, Cenozoic thrusting is the most common basin-range coupling mode. The folding and faulting of Mesozoic sedimentary rocks, spontaneous combustion of Jurassic coal layers and formation of sintered rocks, the Cenozoic earthquakes and active faulting, and the unique mosaic pattern of basin-range framework of Xinjiang are all products of tectonism since the Neogene.

On the Origin of One Basin-Multiple Mountain Couplings in the Mesozoic-Cenozoic Basin-Range Area in Eastern North China

The basin-range coupling relation is a leading subject of the modern geology. In geometry, relations of this type include couplings between stretched orogenic belt and down-faulted basin, compressional orogenic belt and foreland basin, strike-slip orogenic belt and strike-slip basin and so on. Fault chains are the key for these couplings and there are typical examples for all these cases. The North China down-faulted basin is coupled west with the Taihang uplift, east with the Jiao-Liao Mountains, north with the Yanshan orogenic belt and south with the Dabie orogenic belt, that is to say, the central down-faulted basin and the surrounding orogenic belts bear a coupling relation within a uniform dynamistic system. Study shows that the central down-faulted basin and the North China mantle sub-plume structure have a close relation during their formation. Owing to intensive mantle sub-plume uplifting, the bottom of the lithosphere suffered from resistance, which caused the lithosphere of the eastern North China to be heated, thinned and fault-depressed. Meanwhile, mantle rocks that were detached outwards in the shape of mushroom was dissected by surrounding ductile shearing zones, which lead to decompression and unloading to generate hypomagmas, and a series of mantle-branch structures were formed around the down-faulted basin. There is an obvious comparability among these mantle branch structures (orogenic belts), and they have basin-range coupling relations with the central down-faulted basins.

Numerical Modeling of Basin-Range Tectonics Related to Continent-Continent Collision

Continent-continent collision is the most important driving mechanism for the occurrence of various geological processes in the continental lithosphere. How to recognize and determine continent-continent collision, especially its four-dimensional temporal-spatial evolution, is a subject that geological communities have long been concerned about and studied. Continent-continent collision is mainly manifested by strong underthrusting (subduction) of the underlying block along an intracontinental subduction zone and continuous obduction (thrusting propagation) of the overlying block along the intracontinental subduction zone, the occurrence of a basin-range tectonic framework in a direction perpendicular to the subduction zone and the flexure and disruption of the Moho. On the basis of numerical modeling, the authors discuss in detail the couplings between various amounts and rates of displacement caused by basin subsidence, mountain uplift and Moho updoming and downflexure during obduction (thrusting propagation) and subduction and the migration pattern of basin centers. They are probably indications or criteria for judgment or determination of continent-continent collision.

The Gravity Flow on a Shelf-Edge-Slope-Basin-Floor Complex in Qiongdongnan Basin,Northern South China Sea

The Qiongdongnan Basin lies in the west part of the northern South China Sea.To the west the basin is bound by the Red River Fault and the Yinggehai Basin,to the east by the Pearl River Mouth Basin,and to the south by the Xisha Rise.In this study,the sequence stratigraphic framework was set up and 11 third-order sequences were distinguished.Based

ANALYSIS OF STRUCTURAL STYLES OF THE BASIN-RANGE SYSTEMS IN THE CENTRAL CHINA OROGENIC CHAIN OF YANGTZE VALLEY AND THE DYNAMIC MECHANISM

Basin and orogenic belt belong to the same tectonic system which has close connections in spatial distribution and dynamic mechanism.Structural styles analysis of basin－ range system， not only may rebuild basin－ range coupling process and landscape evolution of orogenic belt and its adjacent basin， but also become the foundation in exploring how orogenesis controls landform,climate,resources,energy and environment etc.In the light of geodynamic mechanism,three main types of basin－ range system may be classified,namely,stretch,compression and strike－ slip.In combination with their geotectonic settings and plate movement phases, a comprehensive classification scheme may be educed for structural styles of basin－ range system.Natural disasters and geo－ ecological environment in the Yangtze Valley have been restricted and impressed by crustal movement and Qinling－ Dabie etc.orogenesis since the Mesozoic and Cenozoic.In terms of collocating relation and contacting basin prototype and orogenic belt around the basin for cause of formation, typical structural styles of basin－ range system on the central orogenic chain within the Yangtze Valley consist of coupling Tongbo－ Dabie orogenic belt and Jianghan－ Dongtin fault basin on the northern margin of the central Yangtze landmass， and coupling Qinling－ Daba mountain margin thrust－ faulted orogenic belt and Sichuan foreland basin on the northern margin of upper－ Yangtze landmass.The paper analyzes evolutionary features of two typical structural styles of basin－ range system during syn－ orogenic, late－ orogenic and post－ orogenic stages,and probes into their dynamic mechanism.It is emphasized that,in different stages of basin－ range system of different properties and basin－ mountain transformation process,different structural styles may be formed;and different associations of structural styles can form different types of natural disasters complex and eco－ environment systems.

Study on Basin-Filling and Reservoir Sedimentology of Zhu Ⅲ Depression of Pearl River Mouth Basin,South China Sea

Through basin-filling analysis, one coarsening-upward and two fining-upward sequences have been identified in Zhu Ⅲ depression. In accondance with the general model proposed by Ravnas and Steel (1998), the basin-filling has two large cycles—rift (sediment-balanced and -overfilled) and postrift (sedimentunderfilled and starved). During the rifting process, the rifted lake developed through three stages: early, climax and late. The sedimentary characteristics of reservoir rocks show that barrier bar, lagoon and tidal channel facies well developed in Zhuhai Formation; offshore, tidal and barrier bar well developed in Zhujiang Formation. Neighborly, Shenhu, Wenchang and Enping formations deposited in rifted lakes during Paleogene time; Zhujiang Formation deposited in bay, lagoon and shoreface in late Paleogene. Zhujiang and other formations deposited in offshore and open shallow sea to shelf.

POST-PLATFORM MOUNTAIN-AND BASIN-MAKING MODEL IN HAINAN ISLAND OF CHINA:GEOCHEMICAL CONSTRAINTS FROM IGNEOUS ROCKS

Since the late Hercynian episode the crust in Hainan has entered the post-platform activation or the diwa stage in which it has undergone a process from compressive (collision) orogeny and up1ifting during the late Hercynian-Indosinian movements to block-faulting type mountain- and basin-making during the Yanshanian-Himalayan movements. It has been shown through researches of igneous rocks that a post-platform orogenic belt being of a greatly thickened continental crust was once formed in the Hainan area during the late Hercynian-lndosinian cyc1e. The taphrogeny starting in the late Yanshanian episode was a product at the stage of late orogenic extension under conditions of the mountain root with a thickness of about 60 km retained. At 1ast, the lower lithospheric delamination and the crustal de-rooting of the orogen caused Hainan and its neighboring areas to transform from the continenta1 type crustobody to the continental-margin-spreading type crustobody.

BASIN-RANGE SYSTEM EVOLUTION OF QINLING-DABIE OROGENIC BELT AND ITS IMPACT ON REGIONAL ENVIRONMENT

As the structural body related to temporal-spatial evolution and tectonic dynamic system, the orogenic belt and basin are not only dependent on each other in space but also closely related with each other in terms of infrastructure, matter transference and dynamic mechanisms. By using apatite fission-track method, the authors firstly analyze the uplift and denudation ratios of the Qinling-Dabie orogenic belt, and by using tectonically deformed combination analysis and tectonic-thermal simulation the main geological occurrences are also illustrated. It is found that there must have had multi-phase differential uplift and denudation phenomena in the Qinling-Dabie orogenic belt during the Mesozoic-Cenozoic. Then, the regional evolution pattern of qualitative and quantitative denudation process is obtained during the post-orogenic period. On the basis of summarizing evolution process of the basin-range system in the Qinling-Dabie orogenic belt during the Mesozoic-Cenozoic and its effects on regional environment, the influence of evolution process on geomorphologic landscapes change, water system vicissitude, eco-environment succession and drainage basin system evolution is discussed.

Early Mesozoic Basin-Mountain Coupling Mechanism and Basin Geodynamics of East China

arly Mesozoic flexural basins developed in East China include flexural basin with foredeep, compressive flexural basin, transpressional flexural basin and so on. Late Triassic collision between Gondwana and Eurasian continents led to the formation of large flexural basins with foredeep. Jurassic Tethys geotectonic domain and western Pacific active continental margin activated, resulting in the formation of Early-Middle Jurassic large flexural basins and Late Jurassic small foreland basins. These basins and their marginal orogenic belts were arranged as weakly constrained lateral extrusion structures and constrained lateral extrusion structures, which show a genetic coupling relationship between the orogenic belts and the basins.

BASIN-RANGE TRANSITION AND GENETIC TYPES OF SEQUENCE BOUNDARY OF THE QIANGTANG BASIN IN NORTHERN TIBET

The surface of sequence boundary is a negative record. Its recognition largely depends on the physics of the sediments below and above the boundaries, or on the different sedimentary structures are synthetic marks for the sedimentation and tectonic movements in the sedimentary basin. The Qiangtang Basin that is in 5000m above the sea level is located in Northern Tibet. The Lazhulung—Jinshajiang suture zone now bound it to the north and the Bangong—Nujiang suture zone to the south. Three second\|order tectonic units have been distinguished, i.e. North Qiangtang depression, Central rise and South Qiangtang depression from north to south.The Upper Permian Riejuichaka Formation is built up of mudstone and mud\|limestone, which is represented by sediments in seamarsh. The Lower Triassic Kuanglu Formation, which exhibits the structure unconformable contact with the overlying Upper Permian strata, is characterized by terrigenous clastic rocks in the lower area and is carbonate rocks in the upwarding area and the Middle Triassic Kuangnan Formation. The Upper Triassic Xiachaka Formation consisting of terrigenous clastic rocks, carbonates rocks and mixed sediments, is confined to the uplift zones. The lower Jurassic volcanic rocks are deposited in continental rift. The middle and Upper Jurassic Yangshiping Group are conformable contact and assembled by the gypsum\|bearing terrigenous clastic rock formations and carbonate rock formation. The Middle Cretaceous and the Paleocene strata is built up of the terrigenous clastic rock formations.

Cumulative Coulomb Failure Stress Change in the Basin- range Region of West Beijing and Its Effect on Strong Earthquakes

Since 231 B. C.,a total of 15 M6.0 - 7.5 earthquakes have been recorded in the west Beijing basin-range tectonic region( 38.3°- 41.5° E,112°- 116.2° N),a region mainly under the action of tensional normal faulting. In this paper,we calculate the Coulomb stress change of each earthquake and the cumulative Coulomb stress change,and on this basis we analyze the stress triggering of strong earthquakes. The research shows that there are 10 of 14 earthquakes that occurred in the trigger zones,in which the Coulomb stress change is positive,and the trigger rate is 71%. The positive areas of cumulative Coulomb stress change caused by these 15 earthquakes are: middle of northern Liulengshan fault,Northern Huaizhuo basin fault,Xinbaoan-Shacheng fault,Sangganhe fault and Southern Yuxian basin fault. This necessarily increases the seismic risk of these faults and can be used as a reference for future seismic risk analysis in this area.

Climate Influenced Challenges of Accessibility to Water by Households Downstream of the Upper Benue River Basin-Nigeria

The study examined climate influenced challenges of accessibility to water by households downstream of the Upper Benue River Basin, Nigeria. Literatures related to the topic being investigated were reviewed. The study adopted a descriptive survey design. The population of the study consisted of communities in Adamawa, Gombe, Bauchi and Taraba states. Eight different communities, two in each local government were sampled for the study. Simple random and purposive samplings were used for the study. A total of 351 respondents were selected for the study using Krejcie and Morgan sample size determination. Data analysis was done using frequency tables percentages and mean statistics. The findings of the study showed that climate variability has great impact on water stress and threats to households’ downstream in Upper Benue River basin represented with a mean 3.85 (decrease in the quality and quantity of surface water) as well as 3.43 (drying up of rivers and lakes). The study also revealed that water stress induced by climate variability has a significant effect on household livelihoods represented by 87% of the respondents in the study area. It was also revealed that that households downstream the basin are vulnerable to climate change and households in the study area have development strategies to contend with water stress so as to better their livelihood among which is surface water harvesting (2.78), reducing the number of times dishes are washed (2.96), reducing the quantity of water used for bathing (3.0) among others. The study recommended that stakeholders and the government should make proactive efforts to ensuring that alternative water sources are established in the study area to reduce water stress among the rural populace.

陆相坳陷湖盆细粒沉积岩岩相类型及成因——以松辽盆地晚白垩世青山口组为例

页岩油是目前非常规油气研究的热点与难点。细粒沉积岩岩相类型及成因分析是页岩油“源储”特征研究及“甜点”预测的有效途径。松辽盆地青山口组细粒沉积广泛发育,是页岩油富集的有效层段。本文通过岩性、矿物成分、有机质丰度与沉积构造4个参数,将松辽盆地青山口组细粒沉积岩划分为6种岩相:高有机质泥纹层黏土质页岩(A)、中高有机质含细粉砂纹层长英质页岩(B)、中低有机质含粗粉砂纹层长英质页岩(C)、低有机质层状粉砂岩(D)、低有机质层状介形虫灰岩(E)和低有机质层状白云岩(F)。进一步从水动力学与有机质富集方面探讨了不同岩相类型的成因,并建立了相应的沉积模式。具体为:在风暴浪基面之下的静水、咸水环境、高湖泊生产力背景中,浮游藻类与黏土絮状物均匀悬浮沉降,形成贫富有机质黏土质纹层,沉积A岩相;在正常浪基面之下的相对静水(浪基面附近局部动荡)、半咸水环境、高湖泊生产力背景中,三角洲径流与洪流带来的细粉砂颗粒继续向湖盆中央搬运,经均匀悬浮沉降形成长英质纹层,间歇期悬浮沉降形成黏土质纹层,形成B岩相;正常浪基面之下,洪水携带粉砂级颗粒,顺着水下分流河道搬运至外前缘,以稳定性浊流的形式进入前三角洲,随流速逐渐降低,分异形成粗粉砂—细粉砂纹层,间歇期悬浮沉降形成黏土质纹层,形成C岩相;正常浪基面之下,三角洲前缘早期沉积物在阵发性浊流的作用下,滑塌至较深水区,形成D和E岩相;于正常浪基面与风暴浪基面之间,在相对干燥的气候背景下的咸水环境中,形成F岩相。

准噶尔盆地东部石钱滩凹陷石炭系石钱滩组烃源岩特征及其生烃潜力分析

石钱滩组烃源岩为准噶尔盆地石钱滩凹陷石炭系的主力生烃层位。在充分调研其空间展布的基础上,选取最新发现的双井子地质探槽剖面及石钱1井、石钱2井与钱1井进行系统的烃源岩总有机碳、热解、族组分组成、有机显微组分、镜质体反射率及饱和烃色质等有机地球化学分析测试。结果表明,石钱滩组烃源岩为一套典型的海湾泻湖相沉积,呈NW–SE向展布于石钱滩凹陷,局部地区厚度巨大,可达370 m,沉积厚度中心位于凹陷东南隅。富有机质层段主要集中在石钱滩组下部,次为上部。整体具有较高的有机质丰度,可达到好等级及以上,有机质类型以Ⅱ2-Ⅲ为主,且已进入到高成熟生气阶段。综合研究认为,石炭系石钱滩组烃源岩具有良好的生烃条件,能够为石钱滩凹陷提供充足的油气源。

四川盆地下寒武统筇竹寺组海相页岩气高产井突破与富集模式

多年来下寒武统筇竹寺组页岩气勘探开发进展缓慢,资201井获高产气流大大增加了该套页岩气规模商业化开发的信心,不同区域及层段富集规律差异及下一步勘探开发方向是筇竹寺组页岩开发面临的首要问题。以四川盆地57口钻井资料为基础,对多口重点井的古生物、沉积、储层等特征进行分析,详细剖析资201井的部署理论依据、筇竹寺组页岩气富集条件及下一步勘探开发方向。从地层研究入手,建立了筇竹寺组地层划分标准,明确筇竹寺组主体发育4套深水陆棚相的富有机质页岩(①至④号层段),其分布受裂陷槽发育控制,裂陷槽内厚度最大。分析了页岩储层发育特征,指出储层压力、孔隙度、含气饱和度从下向上、从裂陷槽外到内呈现增大趋势,储层超压对页岩孔隙保存起到重要作用;基于此结合保存条件等建立了“多层异相、超压保孔”的页岩气超压差异富集模式,指出远离散失通道的超压孔隙发育区(层段)是页岩气富集有利区(层段)。文章指出资201井及周边是未来筇竹寺组页岩气增储上产的主要区域,资源量为8.06×10^(12)m^(3);川西地区具有相当的开发潜力,资源量为0.72×10^(12)m^(3);川南长宁及黔北一带受石墨化及构造活动影响,以寻找远离风化壳及地表露头的超压孔隙发育区为主。

柴达木盆地南八仙地区渐新世浅水三角洲物源及沉积演化

以古近系渐新统下干柴沟组上段(E23)为研究对象,在精细岩芯观察和钻(测)井资料综合分析的基础上,结合重矿物组合、ZTR指数、砂岩碎屑组分、粒度累积概率图和砂地比等参数综合分析结果,对柴达木盆地南八仙地区E23湖盆扩张期弱退积型浅水三角洲物源方向、砂体展布规律和沉积微相发育演化进行了深入研究。结果表明:①南八仙地区E23沉积时期物源主要来自南祁连山中酸性岩浆岩和中高级变质岩发育区,物源方向为近北东—南西向,稳定重矿物(磁铁矿、石榴子石、白钛矿和锆石)含量高(质量分数介于81.0%~99.9%)、不稳定重矿物(绿帘石和角闪石)含量低。②南八仙地区E23沉积时期为浅水三角洲—滨浅湖沉积环境,主要发育水下分流河道砂体,岩性主要为岩屑长石砂岩,其次为长石岩屑砂岩,砂体的成分成熟度一般中等—较差、分选磨圆度中等—较差,粒度概率图以反映河流作用的一跳跃一悬浮式为主;沉积构造类型多样,主要发育块状层理、正粒序层理、平行层理和槽状交错层理。③E23沉积时期,南八仙地区继承性发育3条北东—南西向呈条带状展布的砂体富集带(砂地比值介于35%~65%之间),早期到中期砂体发育程度增强,呈进积式;中期到晚期砂体发育程度有所减弱,呈弱退积式。④E23沉积时期,南八仙地区处于浅水三角洲前缘亚相沉积环境,持续发育3个呈北东—南西向展布的沉积朵叶体,主要发育水下分流河道微相,其次为水下分流间湾微相,早期到中期浅水三角洲前缘发育规模增大,中期到晚期发育规模减小。

西藏聂拉木亚汝雄拉晚中新世化石及其古环境意义

西藏聂拉木亚汝雄拉南坡保存有较厚的新生代达涕古湖盆沉积物,并产出晚中新世晚期福氏(垂鼻)三趾马(Hipparion(Cremohipparion)forstenae)化石,是研究青藏高原喜马拉雅地区新生代隆升与环境变迁的重要区域之一。目前对喜马拉雅山脉代表性新生代沉积盆地的地层与古脊椎动物化石的研究工作主要集中在札达和吉隆盆地,对达涕古湖盆的研究程度仍很低。2020年,由中国科学院古脊椎动物与古人类研究所组织的第二次青藏高原综合科学考察研究古生物分队,对聂拉木亚汝雄拉地区开展中-新生代地层与古生物调查,在新近纪地层中采集到一小批脊椎动物化石,包括鲤科咽齿、犀类、有蹄类和鼠兔类。其中,鼠兔类化石归属于艾氏拟美兔(Bellatonoides eroli),这是该属在青藏高原地区的首次发现,指示其产出层位的生物地层年代不会晚于晚中新世早期(灞河期)。根据哺乳动物化石,目前可从亚汝雄拉剖面中识别出两个不同的层位和年代,即上部湖滨相地层产福氏(垂鼻)三趾马,其年代为晚中新世晚期(保德期);下部湖相地层产艾氏拟美兔,其年代可能为晚中新世早期(灞河期)。此前艾氏拟美兔发现于土耳其安卡拉(Ankara)和我国内蒙古中部地区中中新世晚期-晚中新世早期的地层中,通常与灵长类及其他森林型哺乳动物共同出现;福氏(垂鼻)三趾马分布于西藏吉隆和山西保德晚中新世晚期地层中,被认为适应于开阔生境,海拔分布不超过2900m。化石证据显示聂拉木达涕古湖盆在晚中新世早期至晚期的古海拔可能比现代高度低了近2000m,古植被类型存在从晚中新世早期的森林到晚中新世晚期的森林草原环境的转变,整体上晚中新世亚汝雄拉的古环境远比现代要适宜得多。

右江盆地卡林型金矿成矿年代学研究进展

右江盆地是全球仅次于美国内华达地区的第二大卡林型金矿床集中分布区。由于成矿时代的不确定性,盆地内卡林型金矿床的成矿动力学背景一直不清。为准确确定这些金矿床的成矿时代,近四十年来国内外矿床学家进行了孜孜不倦的探索,从早期以石英裂变径迹和流体包裹体Rb-Sr等时线法为代表的定年,到中期以硫化物Re-Os等时线法为代表的单矿物溶样法定年,再到最新以热液金红石、独居石和磷灰石U-Th-Pb法为代表的微区原位定年,其定年对象和方法见证了同位素地质年代学的发展历程。现已基本明确,右江盆地主要发育两期卡林型金矿成矿作用,分别为215~200 Ma和155~140 Ma,相当于印支期和燕山期,其动力学背景分别对应于印支-华南-华北地块碰撞后的印支期陆内造山过程以及燕山期软流圈上涌诱发的岩石圈伸展作用。