青藏高原冈底斯当穹错-许如错-带新近纪—第四纪地堑的基本特征

新近纪以来，印度板块-欧亚板块碰撞期后和抬升阶段发育的新构造和“老构造”的活化，在青藏高原冈底斯-念青唐古拉板片中主要表现为一系列南北向展布的张性构造带和北东、北西向展布的走滑断层，尤以南北向张性构造带活动最为明显，也是现今仍具强烈活动特点的构造带。当穹错-许如错南北向断裂带就是其中之一，由其控制的当穹错-许如错新近纪-第四纪地堑，南北长约190km，东西宽5～25km，由当穹错、当惹雍错、许如错3个子盆地组成。盆缘断裂的形成始于新近纪，第四纪全新世仍有活动，由差异升降导致盆地沉积中心在地堑中自南往北具有由东→西→东的变化趋势，地震、地热等活动南强北弱。反映了青藏高原具整体有限隆升、局部差异升降、新构造活动南强北弱的特点。     

西藏冈底斯当惹雍错-许如错南北向地堑的特征及成因

当惹雍错-许如错南北向地堑位于青藏高原冈底斯中部, 由一组南北向高角度正断层与夹其中间的当穹错、当惹雍错、许如错等3个湖泊盆地构成.地堑发育于中新世晚期, 一直活动到全新世.沿着地堑边缘分布中新世碱性火山岩.白榴石响岩的K-Ar年龄为12.6Ma, 其岩石化学特征显示出陆内伸展构造环境.地堑内部发育晚更新世至全新世的湖相沉积物.当惹雍错-许如错地堑是在青藏高原板内构造隆升过程中, 层流加厚的下地壳热垫作用导致上地壳发生伸展作用, 随着青藏高原地壳物质的东流, 南北向伸展作用转向东西向伸展作用, 形成近南北走向的地堑.      

青藏高原东北缘新近纪晚期构造挤出：来自西秦岭地区安化-成县盆地的证据

西秦岭位于青藏高原东北缘由挤压走滑向走滑伸展构造的转换地带,成为研究青藏高原晚新生代构造扩展过程的重要构造部位。在西秦岭地区发育的一系列新近纪盆地作为高原物质向外扩展的载体,记录了扩展过程中不同阶段的构造活动和演化信息。文中选择位于成县-太白山断裂内的安化-成县盆地,通过对该盆地沉积过程与构造变形方面的详细研究,确定了盆地在新近纪晚期的两阶段构造演化历史。早期受迭部-白龙江、成县-太白山弧形断裂左行走滑的影响,在弧顶及以东位置发生走滑伸展,形成长条形的地堑半地堑盆地。同期沿青川断裂、西秦岭北缘断裂、礼县-罗家堡断裂以及西和断裂分别形成了汉中盆地、武山盆地、天水盆地以及西和盆地。这些走滑断裂向东扩展可能控制了渭河地堑约9 Ma以来的NWSE向伸展,并伴随华山、太白山以及西秦岭东段10~4 Ma的快速隆升。在4.2~2.5 Ma期间,受断裂运动学调整的影响,西秦岭地区新近纪盆地遭受挤压而发生构造反转。新近纪盆地的形成与反转历史清楚地记录了青藏高原东北缘新近纪晚期向东构造挤出的过程。     

西藏冈底斯东段南北向构造特征与成因

西藏冈底斯东段位于青藏高原冈底斯-念青唐古拉板片中段,限定于班公湖-怒江板块缝合带和雅鲁藏布江板块缝合带之间的中生代构造盆地.盆地南北向张性断裂带是板块超碰撞期活动最强烈的构造带.地震、地热和岩浆活动以及控制的线性地貌十分明显.南北向构造带的南北向延伸、东西向展布、切割深度、活动强度的规律性和差异性,充分反映了新构造活动期高原隆升过程中地壳褶缩叠覆、物质侧向滑移和弹滞应变的构造活动特点.     

中国东部陆缘中区中-新生代区域断裂系统时空分布特征、迁移规律及成因类型

中国东部陆缘中区中-新生代深大断裂十分发育.根据断裂的时空分布规律,可划分出4个断裂系:燕山造山带断裂系、秦岭-大别-苏鲁造山带断裂系、郯庐断裂系及东海陆架盆地-冲绳海槽断裂系.4个断裂系具有各自不同的断裂迁移规律:燕山造山带印支-燕山期断裂具有从早至晚从EW→NE→NNE向偏转迁移规律;秦岭-大别造山带北麓逆冲推覆作用的强度在印支-燕山早期表现出南强北弱、东强西弱和东断西褶趋势,同时具有由东向西由早到晚穿时迁移演化特征,燕山末期-喜山早期则相反,表现出北强南弱、西强东弱的构造特征;郯庐断裂系的活动对盆地的控制作用具有由早到晚由西向东、由南向北迁移规律;东海陆架盆地-冲绳海槽断裂的形成时代具有明显的从西向东越来越新的迁移规律.4个断裂系及构造迁移规律分别是板块碰撞-陆内俯冲、陆内造山、走滑、板块俯冲后退4种不同地球动力学背景中的产物.     

青藏高原与南北向地堑相关的火成岩:对地堑成因的制约

南北向地堑(或称裂谷、正断层系)是青藏高原最显著的地貌特征之一,在高原南部可见有六条代表性的近南北向的地堑,其从两向东依次是亚热裂谷、塔口拉-隆格尔裂谷、当若雍错-许如错裂谷(古错-文部裂谷)、定结-申扎裂谷、亚东-羊八井裂谷和错那裂谷等,已有的研究显示,这些南北向地堑的形成从18 Ma(最早可能23 Ma?)延续到现代.     

西藏冈底斯东段南北向构造特征与成因

西藏冈底斯东段位于青藏高原冈底斯－念青唐古拉板片中段，限定于班公湖－怒江板块缝合带和雅鲁藏布江板块缝合带之间的中生代构造盆地。盆地南北向张性断裂带是板块超碰撞期活动最强烈的构造带。地震、地热和岩浆活动以及控制的线性地貌十分明显。南北向构造带的南北向延伸、东西向展布、切割深度、活动强度的规律性和差异性，充分反映了新构造活动期高原隆升过程中地壳褶缩叠覆、物质侧向滑移和弹滞应变的构造活动特点。     

北黄海盆地构造变形及动力学演化过程

以北黄海盆地构造几何学、运动学特征为基础,探讨了北黄海盆地的构造变形样式及动力学演化过程。研究表明,北黄海盆地的构造变形包括伸展构造变形、挤压构造变形、扭动构造变形以及反转构造变形等,北黄海盆地发育的区域动力学背景即是以区域拉伸作用为主、且叠加有水平挤压作用以及相关的扭动作用,并由此导致了北黄海盆地是以一系列地堑、半地堑式坳陷组成的拉张断陷盆地;北黄海盆地的伸展、挤压与升降作用受控于板块相互作用引起的区域引张与挤压应力场并辅以深部软流圈的微弱上拱隆起作用,其动力学演化过程包括晚侏罗世—早白垩世伸展断陷、晚白垩世—古新世热隆、始新世—渐新世裂陷、渐新世末期—新近纪早期构造反转以及新近纪热沉降等5个阶段。     

西秦岭北缘构造带的新生代构造活动——兼论对青藏高原东北缘形成过程的指示意义

西秦岭北缘构造带是青藏高原东北部一条重要的北西西向构造带,它由一组近于平行的断裂组成,中部发育活动的左旋走滑断裂,两侧发育向外扩展的多条逆冲断裂,剖面上呈向北偏心的花状构造。自古近纪中晚期以来西秦岭北缘构造带成为青藏高原早期的北东边界,其新生代构造活动控制了两侧的新生代盆地沉积演化和构造变形。在构造带南侧滩歌盆地自古近纪中晚期堆积了一套厚度较大的砾岩和砂岩地层,但未见新近纪地层;沿西秦岭北缘构造带中部在中新世形成具有剪切拉张性质的武山—漳县盆地,沉积了厚度超过千米的砾岩、砂岩和泥岩序列;在构造带北侧陇西盆地从古近纪中晚期至中新世晚期一直处于前陆盆地发育阶段,沉积了连续的新生代地层序列。在中新世晚期以后,整个构造带遭受挤压变形,逆冲活动强烈,中部的武山—漳县盆地和北侧的陇西盆地相继消亡,新生代地层发生强烈构造变形,位于构造带南侧的滩歌盆地也同时发生轻微缩短变形。第四纪晚期以来西秦岭北缘构造带断裂活动主要表现为左旋走滑运动方式,而逆冲断裂活动则迁移到了北东方向的海原断裂和香山—天景山断裂(又称中卫—同心断裂)等构造带之上,实现了大区域范围内的应变分配。     

塔里木盆地阿瓦提凹陷周缘的晚新生代张扭性断层带

塔里木盆地西北部的阿瓦提凹陷周缘发育晚新生代正断层,其中第四纪的正断层活动是塔里木盆地构造地质研究的新发现。这些正断层受先存基底断裂控制,平面上沿沙井子断裂带、阿恰断裂带和吐木休克断裂带右阶式雁列状分布,构成右阶左旋张扭性正断层带。剖面上,向下断达下古生界后不清楚,向上断至第四系上部,构成阶梯状或小型地堑(或负花状构造)构造。生长系数计算结果表明,正断层带形成于新近纪末,第四纪早-中期持续活动,到第四纪晚期停止活动。这些张扭性正断层带的成因是阿瓦提地块相对于周边地质体的顺时针旋转而致,其动力学来源于印度板块与欧亚板块陆-陆碰撞,在晚喜马拉雅山期依然持续作用而导致的远程效应。     

Quaternary Lake Deposits of Nam Co, Tibet, with a Discussion of the Connection of Nam Co with Ring Co-Jiuru Co

Shorelines are widespread and lake deposits and lake geomorphology are well developed on the northern Tibetan Plateau. Through field observations of lacustrine deposits of Nam Co-the highest and largest Quaternary lake in Tibet, the authors found four-step shore terraces composed of sands and clays with well-developed horizontal bedding and 3-12 m, 15-22 m, 25-30 m and 35-45 m higher than the lake surface respectively, lacustrine deposits resting on the bedrocks and 60-150 m higher than the lake surface, and up to -50 levees composed of oblate lakeshore gravels. Moreover they found lacustrine and lakeshore deposits making up the terraces and levees on the bottoms of wide dividing valleys connecting Nam Co with the Rencoyuema, Rencogongma and Jiuru Co northwest of Nam Co (the valley bottoms are 20 m, 90 m and 60 m higher than the above-mentioned three lakes) and on slopes north of it, i.e. terraces II and III of Nam Co. Thus they confirm that Nam Co and Ring Co-Jiuru Co had connected with each other seve     

西藏纳木错与仁错-久如错连通的地质记录

西藏是我国湖泊最多的省区。藏北内流区则集中了西藏最多的湖泊和大湖。其中,位于藏北内流区东南部的纳木错,则是西藏面积最大(1920ｋｍ₂)和海拔最高(4718ｍ)的大湖。前人仅少量报道过该湖的湖岸阶地与古湖岸线,并推论该湖在青藏高原的“大湖期”(40000～28000ａＢ.Ｐ.或40000～25000ａＢ.Ｐ.)时,有可能是以河道通过仁错(海拔4648ｍ)而与色林错相通的外流湖。2000年夏,作者在纳木错沿岸的考察中发现:在作曲卡下游、夺玛半岛东南岬角、玛尔北岸、塔吉古日西北坡、昂崩与昂千南麓等地的湖滨平原上,分布着     

西藏佩古错湖盆区旅游资源特征

在希夏邦马峰地区，到处白雪皑皑，山下广阔的茵茵草原和明镜船湖群及其生态系统中蕴含着世所少见的自然景观和生态景观，目前大部份仍为未开拓的处女地，且世人知之甚少。本文简介了雪山冰川景观、水生生态系统和草原生态系统景观，据本区生态平衡脆弱性特点，提出了开发的同时要保护的具体措施。     

Glacio-dynamic structures from the Blackwater Formation, Co. Wexford, Ireland

A series of large-scale glacio-dynamic structures exposed in 10 km of coastal cliff cut through the Screen Hills kame-morainc, Co. Wexford. Ireland, is descrihed. The structures range from simple ovcrfolds to complex multiple thrusts, have a consistent structural trend, and result from marginal deformation by an ice-sheet moving from the NE. The relationship between the structures and other, gcomorphic and stratigraphic components is resolved into a simple model of repeated ice-marginal oscillation during a phase of overall glacial retreat.     

Rare-earth elements,Co, Sc and Hf in the Steens Mountain basalts

The concentrations of the rare-earth elements (REE) in 52 of 70 consecutive lava flows from Steens Mountain, Oregon, are reported. The concentrations of Co, Sc and Hf were measured in 17 of the flows. Logarithmic partitioning theory is used to correlate the concentrations of the trace elements with the major element and mineralogical compositions of the samples.Production of the basalts by partial melting requires a parent material that has concentrations of the REE that are several times those of chondrites. Those samples enriched in alumina have positive Eu anomalies compared to chondrites and those depleted in alumina have negative Eu anomalies. Production of these samples by partial melting is unlikely because the Eu anomalies would require that plagioclase was stable under the conditions of melting.All of the samples can be related to a single parent magma by fractional crystallization processes. The concentrations of the trace elements are controlled by the addition or removal of plagioclase and the removal of clinopyroxene. Samples with high concentrations of alumina are interpreted as plagioclase cumulates while those with low concentrations of alumina are residual liquids produced by crystallization of plagioclase. During fractional crystallization, the concentrations of the light REE are increased selectively in the residual liquid. The material that must be crystallized and removed during fractional crystallization has characteristics that are similar to those reported for gabbros.     

Successive deformation episodes along the Lungmu Co zone, west-central Tibet

Field study, thermochronology and geochemistry of the east Lungmu Co (LMC) range highlight some of the geological events that shaped western Tibet. The LMC fault zone has long been interpreted as the boundary between the Tianshuihai terrane of Laurasian affinity and the Qiangtang block of Gondwanian affinity. In the LMC range, the Paleozoic series is intruded by the Mangtsa leucogranite whose zircon have a U/Pb age of 116.9 ± 1 Ma and by mafic rocks with U/Pb zircon ages ranging from 116.9 ± 1 to 95.1 ± 1.7 Ma. Geochemistry of the mafic rocks indicates that they have been emplaced in a supra-subduction zone setting, probably the north dipping Nujiang suture zone. ⁴⁰Ar/³⁹Ar micas ages of the granite indicate that cooling below ~ 350 °C occurred between 105 and 85 Ma. ⁴⁰Ar/³⁹Ar K-feldspar data suggest a fast cooling event at 60-55 Ma, which we relate to the reactivation of the LMC suture zone as a thrust at the onset of the India-Eurasia collision. The last, and still active, deformation event corresponds to left-lateral strike-slip faulting along the ENE-WSW LMC fault.     

白山市大横路铜钴矿区稀土元素地球化学特征

本文主要从稀土元素的地球化学特征所反映的地球化学信息,研究变质岩原岩的沉积环境,变质阶段稀土元素的变化规律,成矿物质的迁移规律,变质环境等.     

Strong site preference of Co2+ in olivine,Co1.10Mg0.90SiO4

The crystal structure and site preference of Co²⁺ in a synthetic Co_1.10Mg_0.90SiO₄ olivine have been determined from single crystal X-ray diffraction data collected on an automatic diffractometer. The R factor is 0.044 for 612 reflections. The site occupancies are: Ml site: Co 0.730±0.006; Mg 0.270; M2 site: Co 0.370, Mg 0.630. The Gibbs free energy change, ΔG° for the ion-exchange reaction between M1 and M2 sites is ?4.06 kcals/mole, assuming ideal mixing at each set of sites. This energy may be called ‘site preference energy’ of Co²⁺ in olivine. The strong preference of Co²⁺ for the M1 site can be quantitatively explained by two competing forces: preference of ions larger than Mg²⁺ for the M2 site and stronger covalent bonding of transition metal ions at the M1 site. For Fe²⁺, Mg²⁺, these two effects nearly neutralize each other, explaining the lack of considerable cation-ordering in Fe-Mg olivines.