我国首次发现原生—自然硅

本文对自然硅进行了矿相学，矿物学研究，该矿物产于福建某地矽卡岩型硫，多金属矿床中，自然硅呈亮灰银白色、强金属光泽。性脆。镜下呈浑圆粒状、乳滴状，均质。实测比重ｄ＝２．３６８。硬度ＨＭ＝６．７６。反射率Ｒ：４７０ｎｍ３７０８；５４６ｎｍ３１．２７；６５０ｎｍ２９．９６。经扫描电镜能谱分析、电子探针分析，Ｓｉ９９．８７％～９９．９４％。含少许Ａｌ，Ｃａ，Ｆｅ机械混入物，Ｘ射线粉晶分析，主要Ｘ射线粉晶谱     

Neogene Through Quaternary Tectonic Reactivation of SW Iberian Passive Margin

Southwest Portugal, the Gulf of Cadiz and Morocco are under the potential threat of natural hazards linked to seismicity and tsunami generation. We report the results of two multi-channel seismic (MCS) surveys carried out in 1992 and 1998 along the continental margin and oceanic crust of SW Iberia. This MCS data set shows the evidence of the compressional deformation which involves both the continental and the oceanic crust of the study area. The area of deformation extends from the southern border of the Tagus Abyssal Plain to the Seine Abyssal Plain, encompassing the continental margin of SW Portugal. Most of the structures observed are probably related to a Mid-Miocene phase of Africa-Europe plate convergence. In this paper we discuss the recent advances on the identification of the tectonic structures that are still active and that may generate great earthquakes and tsunamis. The tectonic structures identified are located respectively at the Guadalquivir Bank, along the eastern border of the Horseshoe Abyssal Plain and along the southern continental slope of SW Portugal.BIGSETS Team: L. Mendes Victor, C. Corela, A. Ribeiro, D. Cordoba, J. J. Danobeitia, E. Grácia, R. Bartolomé, R. Nicolich, G. Pellis, B. DellaVedova, R. Sartori, L. Torelli, A. Correggiari, L. Vigliotti.     

四川大渡河金矿田成矿流体来源的氦氩硫氢氧同位素示踪

四川大渡河金矿田位于扬子地台西缘金成矿带北段,受大渡河剪切带控制。本文以该矿田黄金坪、白金台子、黑金台子金矿为例,根据对黄铁矿流体包裹体氦氩同位素、黄铁矿硫同位素以及与黄铁矿共生的石英流体包裹体的氢氧同位素组成测定,讨论了大渡河金矿田成矿流体的来源。结果显示,该金矿田黄铁矿流体包裹体中的~3He/~4He变化较小,为0.16～0.86Ra,而~(40)Ar/~(36)Ar的变化较大,为298～3288;而黄铁矿δ~(34)S同位素变化范围较窄,一般为0.7‰～4.2‰,集中于2.5‰～3‰,显示硫地幔来源的特点;石英流体包裹体的氢、氧同位素分别为-2.6‰～ 3.64‰和-39.13‰～-108.23‰,说明成矿流体为岩浆水和大气降水的混合流体。本文认为大渡河金矿田成矿流体是地幔流体与地壳流体的混合作用的结果,而以地壳流体占主导地位。其中,地幔流体为与下伏隐伏岩体有关的岩浆水,而地壳流体端元则是含有一定放射成因Ar的大气降水,并且温度小于200℃。     

东营凹陷沙河街组湖相烃源岩的组合特征

古近系沙河街组是东营凹陷最重要的成藏组合。在前人研究基础上 ,系统采集该组 6 0 0余块烃源岩样品和 30个油田 186个原油样品 ,分别进行了多项有机地球化学测试。结合其沉积序列和地球化学分析结果 ,将沙河街组烃源岩划分为咸水湖相 (沙四段上部 )、半咸水深湖相 (沙三段下部 )和淡水湖相 -三角洲 (沙三段中部 )三种成因类型 ,它们分别对应欠充填、平衡充填和过充填的湖泊类型 ,代表了陆相断陷盆地烃源岩三种最基本的成因模式 ;并发现沙河街组烃源岩存在强烈的非均质性 ,尤其在平衡充填过程中表现更为突出 ,这种非均质性与湖平面的升降变化密切相关 ,据此提出了波动湖相沉积。通过深入的油 -源对比工作 ,确立了咸水湖相和半咸水深湖相烃源岩为东营凹陷的主力源岩。还探讨了有机质的赋存状态和油气运移方式 ,指出咸水湖相烃源岩形成的油气以侧向运移为主 ,形成的油气藏分布在盆地的边缘 ;半咸水深湖相烃源岩形成的油气以垂向运移为主 ,形成的油气藏主要分布在盆地的中心 ,油藏类型主要为隐蔽性油气藏     

东海西湖凹陷新生界主要不整合面地层剥蚀厚度恢复

综合地质对比法、声波时差法以及不连续镜质体反射率法得到西湖凹陷新生界T2^0、T2^4、T3^0三个重要的不整合面上地层的剥蚀厚度。剥蚀量的宏观分布与主要构造带的走向基本一致，局部构造的剥蚀与其特定的构造位置有关。T2反射界面为斜坡-褶皱型地层剥蚀模式，剥蚀量主要分布在中央背斜构造带，沿龙井一井-东海一井-花港一井-玉泉二井-残雪一井一线附近的地层剥蚀量最大，可达2000m以上；西部斜坡区次之。T2^4反射界面地层剥蚀模式为过渡型剥蚀模式，地层剥蚀量在凹陷东部边缘较大，最大可达800m以上；中央背斜带的东海一井构造带、龙井一井构造带、花港一井构造带、玉泉一井构造带、玉泉二井构造带、残雪一井构造带、春晓构造带等有局部剥蚀，一般在400～600m以内。T3^0反射界面为断块-斜坡地层剥蚀模式，地层剥蚀量以西部斜坡最大，中央背斜局部构造有剥蚀。西部斜坡带剥蚀量一般在200～800m之间，中央构造带的龙井二井构造带、花港一井构造带、玉泉二井构造带、天外天一井构造带以及东缘构造带有较少剥蚀，一般在200～400m以下。     

Lithospheric structure of the Tornquist Zone resolved by nonlinear P and S teleseismic tomography along the TOR array

The main aim of the TOR project is to study the lithospheric–asthenospheric boundary structure under the Sorgenfrei–Tornquist Zone, across northern Germany, Denmark and southern Sweden. Relative arrival-time residuals of teleseismic P and S phases from 51 earthquakes, recorded by 150 seismic stations along the TOR array, were used to delineate the transition zone in the studied area. The effects of crustal structures were investigated by correcting the teleseismic residuals for travel-time variations in the crust based on a 3D crustal model derived from other data. The inversion was carried out for S phases. The results were then compared with the corresponding P-wave models. As expected, the derived models show that the relatively old and cold Baltic Shield has higher velocity at depth than the younger lithosphere farther South. The models show two sharp and distinct increases in depth to velocities which are low compared to our reference model, as we move from South to North. The location and sharpness of these boundaries suggests that the features resolved are, at least partially, compositional in origin, presumably related to mantle depletion. A sharp and steep subcrustal boundary is found roughly coincident with the southern edge of Sweden. This is below where the edge of the Baltic Shield is usually placed, based on surface geological evidence (the Sorgenfrei–Tornquist Zone). Another less significant transition is recognised more or less beneath the Elbe-lineament. Relatively high d(V_p / V_s) ratios under the central part of the profile (Denmark) indicate relatively low S-velocity in an area where a gravity high supports the hypothesis of extensive mafic intrusions.     

"磁暴基础数据库"项目成果介绍

本文详细介绍了“磁暴基础数据库”项目的立项背景、目标、所开展的主要工作、取得的成果、研究成果的社会效益和对该领域研究未来工作的展望。