面波波形反演中的模拟退火法

采用求解非线性全局优化问题的模拟退火法作为反演手段 ,对面波波形进行反演 ,研究青藏高原地壳上地幔速度结构。通过青藏高原的面波波形振幅谱显示出在周期为 2 0 s和4 0 s时存在两个极小值 ,这可能是由地壳中存在低速层引起的。面波波形反演得到的速度模型也证实了青藏高原在 2 0 km深度左右普遍存在低速层 ;喜马拉雅山造山带在 6 0 km深度附近也存在一低速层。壳内低速层是青藏高原变形及隆升过程最重要的动力学边界条件之一     

国产海底地震探测装备技术研发与应用

为研究深部壳幔结构、海底地震活动性和实现地震海啸预警,需要在海底布设海底地震仪开展地震观测。深海海底地震仪因涉及地震传感器、深水水听计、声学换能器与耐压封装等先进国际技术,我国高性能深海海底地震仪长期是空白。对此,中国科学院地质与地球物理研究所通过多年持续核心技术攻关和多次深海试验验证,解决了数字调零宽带地震传感技术、全海深陶瓷压电水听传感技术、软硬协同优化低功耗采集技术和万米高可靠性释放回收技术等关键技术难题,自主成功研发了包括便携式海底地震仪、宽频带海底地震仪与实时海底地震仪等系列海底地震探测装备（统称为IGG-OBS）。实验结果表明：自主研发的IGG-OBS仪器装备达国际先进水平;近年来在多个科考航次中发挥支撑作用,总计投放达1400余台次,综合回收率大于90%;通过在洋中脊、海山、俯冲带等多种复杂海底区的实际观测,数据质量合格率>98%,具备复杂构造成像能力,已进入实质性应用阶段,为我国深海科考、大洋调查及近海灾害预警监测等提供了关键技术支撑。     

壳幔混染成矿机制的流体包裹体证据—以滇西老王寨金矿为例*

深部地质过程的流体包裹体示踪显示,老王寨金矿床含矿石英中Na Cl-H2O包裹体和CO2-H2O包裹体发育,含矿热液从成矿前阶段→成矿阶段→成矿后阶段,其均一温度、成矿压力、盐度与侵位深度变化依次表现为226.2~374.9℃→173.1~251.1℃→107.2~170.9℃、(827~1 084)×105Pa→(711~736)×105Pa→(410~460)×105Pa、9.208%~9.857%→4.496%~4.651%→2.736%~4.651%和3.19~4.18 km→2.74~2.84 km→1.59~1.78 km。综合研究表明,矿区初始含矿流体主要为含CO2的地幔流体,随着成矿作用的进行,含矿热液温度、压力、盐度和侵位深度不断降低,导致成矿流体由高温熔浆性质向低温热液性质演变,从而表现出壳幔混染特征。这一深部地质演化过程反映,高温高压的含矿地幔流体,在参与成矿过程中,与地壳岩石相互作用,引发交代蚀变及壳幔物质混染叠加成矿。     

金伯利岩与金刚石

本文简要介绍了自然界分布极少,来源最深的一种火成岩 — 金伯利岩、其中的地幔捕虏体以及金刚石的特征,他们三者有着密切成因联系。金伯利岩岩浆来自深达200 km的地幔,地幔内部在高温、高压及低氧逸度的环境下可以结晶出金刚石,当岩浆快速上升时携带了地幔捕虏体及其解体矿物,金刚石也是被携带的矿物之一。除了碳的微粒通过固体扩散形成金刚石外,流体及熔体对金刚石生长过程所起的作用也不可忽视。     

Growth and reworking of cratonic lithosphere

To study the thinning of cratonic lithosphere in North China has been the hot subject of basic research in the fields of solid earth science in China. This paper presents an overview on the formation and evolution of continental crust, and outlines the mechanisms of forming the lithospheric mantle. It is suggested that the thinning of cratonic lithosphere principally proceeds in two ways, one by subduction erosion （e.g., North China）, and the other by a combination of subduction erosion and underplating degistion （e.g., Yangtze）.     

Textural and chemical zoning in garnets related to mantle metasomatism and deformation processes

A few texturally-zoned garnets were found in a polymict peridotite (JJG1414) from the Cretaceous kimberlite, Kimberley, South Africa. The systematic analyses of electron and ion microprobe as well as laser fluorination technique reveal the existencal of marked elemental and oxygen isotopic zonation in these garnets, corresponding to the textural zonation. The rims are normally enriched in Ca, Ti, Cr, LREE, Sr, Nb, and depleted in Mg, Al and¹⁸O. It is demonstrated that these garnets were infiltrated by melts/fluids, probably representing the disequilibrated products of fluid-assisted mantle deformation.     

Uppermost mantle structure of the North China Craton: Constraints from interstation Pn travel time difference tomography

The uppermost mantle is the key area for exchange of heat flux and material convection between the crust and lithospheric mantle. Spatial variations of lithospheric thinning and dynamic processes in the North China Craton could inevitably induce the velocity heterogeneity in the uppermost mantle. In this study, we used Pn arrivals from permanent seismic stations in North China and surrounding regions to construct a tomographic image of the North China Craton. The tomographic method with Pn travel time difference data were used to study the velocity variations in the uppermost mantle. Pn velocities in the uppermost mantle varied significantly in the Eastern, Central and Western blocks of the North China Craton. This suggests that the lithosphere beneath different blocks of the North China Craton have experienced distinct tectonic evolutions and dynamic processes since the Paleozoic. The current uppermost mantle has been imprinted by these tectonic and dynamic processes. Fast Pn velocities are prominent beneath the Bohai Bay Basin in the Eastern Block of the North China Craton, suggesting residuals of the Archean lithospheric mantle. Beneath the Tanlu Fault Zone and Bohai Sea, slow Pn velocities are present in the uppermost mantle, which can be attributed to significant lithospheric thinning and asthenospheric upwelling. The newly formed lithospheric mantle beneath Yanshan Mountain may be the dominant reason for the existence of slow Pn velocities in this region. Conversely, the ancient lower crust and lithospheric mantle already have been delaminated. In the Central Block, significant slow Pn velocities are present in Taihangshan Mountain, which also extends northward to the Yinchuan-Hetao Rift on the northern margin of the Ordos Block and Yinshan Orogen. This characteristic probably is a result of hot asthenospheric upwelling along the active tectonic boundary on the margin of the Western Block. The protracted thermal erosion and underplating of hot asthenospheric upwelling may induce lithospheric thinning and significant slow velocities in the uppermost mantle. Fast velocities beneath the Western Block suggest that the thick, cold and refractory Archean lithospheric keel of craton still is retained without apparent destruction.     

地幔的窗口：金刚石

从经济价值而言，金刚石是最昂贵的宝石饰品；从科学意义而言，它还是直接可以提供地幔的物理状态与化学组成的窗口。笔者简要介绍了金刚石在自然界的产状、形成条件、不纯净组分、各类包裹体的特征以及成因模型。金刚石最主要的寄主岩为地幔橄榄岩和榴辉岩。金刚石中的同生包裹体可以为其形成时的寄主岩组成、温压条件、在地幔中的存留年龄提供重要的依据。近20多年来在金刚石中发现了深达下地幔的超深矿物包裹体，它又成为了认识全部地幔物质组成的唯一窗口。     

新元矿井主斜井穿越表土层的施工方法--斜井施工穿过沁水煤田寿阳地区表土段问题的探讨

文章介绍了新元矿井主斜井表土层的施工方法，对寿阳地区今后矿井井筒施工具有一定的参考价值。     

吕梁山区五台群顶部地层的Sm-Nd年龄——兼论岩浆源区地幔的特殊性

本文根据Sm-Nd同位素工作结果,给出五台群的顶界年龄为2470Ma,属太古代地层。华北地台基底的太古代地层中几处出现世界上同时代的其它构造单元中尚未发现过的高∈~Nd(T)值,表明当时地幔的局部不均匀性已很可观。岩石的既往亏损史与Nd相对富集的情况相矛盾,可能是由于深部地幔去气流体的补入或形成时间不长的地壳物质的混染。