甘肃北山地区晚第四纪构造变形特征及演化趋势

通过对甘肃北山地区ETM影像的细致分析和初步野外考察,对北山地区晚第四纪以来断裂活动时代和运动性质进行了研究。结合附近地区天山构造带、青藏高原北部边缘断裂的演化过程和区域构造应力场状态,对北山地区晚第四纪以来变形机制和演化趋势进行了研究。认为北山地区现今构造格局是在印度板块与欧亚板块相碰撞形成的北东向挤压构造应力场的作用下,重新激活东西向的晚古生代、中生代断裂,并产生北东向新生断裂而形成。晚第四纪以来,北山地区构造变形以南北向缩短为主,伴随有东西向伸展。随着印度板块的向北运移,北山地区的构造变形将进一步增强,即南北向缩短和东西向的扩展将进一步增强。     

西昆仑--喀喇昆仑及其邻区岩石圈结构、演化中几个问题的探讨

西昆仑-喀喇昆仑位于西藏高原西北,西构造结(Western Syntaxis)的东侧,是当前国际地学界关注的热点地区之一.本文不准备对该地区岩石圈结构、演化及其多重效应作全面论述,仅以近年青藏高原项目实施中涉及的几个较重要问题作探讨;经过对已获得的地震深探测和地质、地球化学资料的分析研究,提出青藏高原西北缘不存在塔里木向西昆仑山作长距离的"A型俯冲",晚新生代以来岩石圈"面对面水平挤压-拆沉作用"是形成西昆仑陆-陆碰撞造山带的主要原因.对众所关注的库地蛇绿岩形成时代,提出了新的SHRIMP-Ⅱ,U-Pb锆石测年年龄,上限为510±4Ma;对原特提斯大洋、康西瓦大型走滑断裂带的形成、演化作了探讨.     

Relaxation of protostellar accretion shocks using the smoothed particle hydrodynamics

It is believed that protostellar accretion disks are formed from nearly ballistic infall of molecular matter in rotating core collapse. Collisions of this infalling matter leads to formation of strong supersonic shocks, which if they cool rapidly, result in accumulation of that material in a thin structure in the equatorial plane. Here, we investigate the relaxation time of the protostellar accretion post‐shock gas using the smoothed particle hydrodynamics (SPH). For this purpose, a one‐dimensional head‐on collision of two molecular sheets is considered, and the time evolution of the temperature and density of the post‐shock region simulated. The results show that in strong supersonic shocks, the temperature of the post‐shock gas quickly increases proportional to square of the Mach number, and then gradually decreases according to the cooling processes. Using a suitable cooling function shows that in appropriate time‐scale, the center of the collision, which is at the equatorial plane of the core, is converted to a thin dense molecular disk, together with atomic and ionized gases around it. This structure for accretion disks may justify the suitable conditions for grain growth and formation of proto‐planetary entities (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐shooting Herbig Ae/Be stars: Accretion probed by near‐infrared He I emission

The Herbig Ae/Be stars are intermediate mass pre‐main sequence stars that bridge the gap between the low mass T Tauri stars and the Massive Young Stellar Objects. In this mass range, the acting star forming mechanism switches from magnetically controlled accretion to an as yet unknown mechanism, but which is likely to be direct disk accretion onto the star. We observed a large sample of Herbig Ae/Be stars with X‐shooter to address this issue from a multi‐wavelength perspective. It is the largest such study to date, not only because of the number of objects involved, but also because of the large wavelength coverage from the blue to the near‐infrared. This allows many accretion diagnostics to be studied simultaneously. By correlating the various properties with mass, temperature and age, we aim to determine where and whether the magnetically controlled mass accretion mechanism halts and the proposed direct disk accretion takes over. Here, we will give an overview of the background, present some observations and discuss our initial results. We will introduce a new accretion diagnostic for the research of Herbig Ae/Be stars, the HeI 1.083 μm line (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Accurate GPS measurement of the location and orientation of a floating platform

Abstract

This article describes the design and initial tests of the GPS portion of a system for making seafloor geodesy measurements. In the planned system, GPS antennas on a floating platform will be used to measure the location of an acoustic transducer, attached below the platform, which interrogates an array of transponders on the seafloor. Since the GPS antennas are necessarily some distance above the transducer, a short‐baseline GPS interferometer consisting of three antennas is used to measure the platform's orientation.

A preliminary test of several crucial elements of the system was performed at the Scripps Institution of Oceanography (SIO) in December 1989. The test involved a fixed antenna on the pier and a second antenna floating on a buoy about 80 m away. GPS measurements of the vertical component of this baseline, analyzed independently by two groups using different software, agree with each other and with an independent measurement within a centimeter.

The first test of an integrated GPS/acoustic system took place in the Santa Cruz Basin off the coast of southern California in May 1990. In this test a much larger buoy, designed and built at SIO, was equipped with three GPS antennas and an acoustic transducer that interrogated a transponder on the ocean floor. Preliminary analysis indicates that the horizontal position of the transponder can be determined with a precision of about a centimeter. Further analysis will be required to investigate the magnitude of systematic errors.     

西沙周缘新生代构造演化与盆地充填响应特征

利用南海西沙周缘地震资料,进行了地震相研究,并结合邻区地质资料,进行了南海西沙周缘新生代沉积相分析,讨论了盆地的充填演化历史。研究认为,南海西沙周缘盆地充填断陷期以陆相和海陆过渡相沉积为主;坳陷期以海陆过渡相和海相沉积为主,自下而上充填了一套冲积相-湖相(始新统)-海陆交替相(渐新统)-滨浅海台地相(中-下中新统)-浅海、半深海相(上新统-第四系)沉积序列,盆地的充填历史反映了南海西沙周缘沉积环境由陆相向海相逐渐过渡的过程。通过对油气地质条件分析,认为始新世-渐新世早期是重要的烃源岩发育期;渐新世晚期-中新世中期是储层发育期;中新世晚期后是区域该层发育时期。     

成矿元素的离子结构及其在花岗岩成矿过程中的 行为

研究表明,不同类型岩石的形成导致不同类型元素的富集成矿,而后者与元素的自身结构密切相关:具惰性气体型离子结构的元素亲沉积岩,具过渡型或铜型离子结构的元素亲岩浆岩。进一步研究发现,陆壳大规模熔融 固结,亦即花岗岩的形成过程,不但导致不同类型元素在上陆壳及其上层圈重新分配:亲氧(造岩)元素占据壳内熔融(岩浆)层的位置,亲硫(成矿)元素迁移到岩浆层上覆盖层且其中副族成矿元素按离子半径增大的顺序沉淀析出,亲水元素迁移到水圈而亲气元素则回归大气圈;同时揭示了与陆壳地质结构相适应的陆壳元素地球化学结构,体现了自然界微观和宏观的协调与和谐。     

Application of Gravitational Methods to Prospecting Salt(Potash) Rocks in the Kuqa Depression

正The Kuqa depression deposited thick rock salt,which has a lower density than surrounding rocks.When salt bodies form a certain scale,obvious negative gravity anomalies can be detected in the surface.Therefore,gravitational method can quickly obtain the shape,plane distribution of deep-seated salt bodies and overall tectonic morphology of the basin.     

蒙古国东方省海塔盆地塔南凹陷断裂特征及其油气意义

以三维地震资料解释为基础,通过编制相关构造图件揭示了海塔盆地塔南凹陷的断裂构造特征和构造演化过程,分析了构造活动对沉积作用的控制以及对烃源岩发育、圈闭形成和油气运移聚集条件的影响。塔南凹陷白垩纪经历了叠合断陷期(铜钵庙组—南屯组沉积时期）、叠合断拗期(大磨拐河组沉积时期）和反转拗陷期(伊敏组—青元岗组沉积时期）共3期演化,发育伸展和走滑—伸展两套断裂系统。受断裂活动影响,不同时期各次凹的沉降中心发生了明显的分异与迁移。断陷期沉降中心沿断陷边界断层上盘分布,断拗期沉降中心向凹陷中心迁移。断陷期结构样式及主干断裂活动强度控制着沉积相的分布,也影响油气成藏。     

华北板块北缘东段中元古代造山带地质特征及构造演化

研究区内的中元古代魏家沟岩群原岩为一套碳酸盐岩、陆缘碎屑岩及火山岩建造,形成于大陆裂谷-活动大陆边缘阶段,并于1036 Ma左右遭受变质变形.通过岩浆岩形成构造环境的判别,研究区中元古代岩浆活动贯穿于板块碰撞前、同碰撞及碰撞后.伴随着造山带的演化,本区中元古代经历了3期韧性变形,分别形成于大陆裂谷、活动大陆边缘及碰撞造山阶段.通过上述研究,确定了本区中元古代造山带的存在,并经历了大陆裂谷-被动大陆边缘-活动大陆边缘-碰撞造山的地质演化过程,证实了格林维尔造山运动在华北板块北缘的存在和对中元古代末期Rodinia超大陆拼合的响应.