湘西沃溪W-Sb-Au矿床白钨矿Nd-Sr-Pb同位素对成矿流体的示踪

本文对湘西沃溪W-Sb-Au矿床白钨矿进行了系统的Nd-Sr-Pb同位素分析。结果表明,白钨矿的Sm、Nd含量较低,147Sm/144Nd(0.64~1.27)值和Sm/Nd值(1.11~2.22)变化较大,其εNd(t=199Ma)值也很低,平均为-25.5(n=9);白钨矿的87Sr/86Sr值(0.7476~0.7504)高,平均为0.74961(n=11),代表白钨矿形成时的初始87Sr/86Sr(t=199Ma)值;逐级分离Pb同位素分析结果显示白钨矿的206Pb/204Pb、207Pb/204Pb、208Pb/204Pb值变化范围小,平均依次分别为18.11、15.61、38.6,与含金石英脉中黄铁矿、蚀变围岩及区域板溪群板岩等的相应Pb同位素比值基本一致。白钨矿Nd-Sr-Pb同位素组成和闪锌矿等其他矿物的Sr同位素特征指示成矿流体来自板溪群下伏成熟陆壳、深部花岗质岩浆、浅部赋矿围岩等源区。成矿流体是这些来自不同源区的流体相作用而形成的混合流体。成矿作用则是这些不同源区的流体混合作用并演化的结果。且成矿流体演化早期是来自下伏成熟陆壳的流体与来自赋矿围岩的流体混合,导致早期W成矿;晚期是来自深部花岗质岩浆的流体与浅部赋矿围岩的流体混合作用,导致晚期Sb-Au成矿。W-Sb-Au成矿则是中生代陆内碰撞造山体制下不同期次的流体演化和叠加作用的结果。     

藏东缘昌都大型复合盆地喜马拉雅期陆内造山与成矿作用

研究藏东缘大型复合盆地喜山期陆内造山与成矿作用的目的,在于建立横断山型陆内碰撞造山构造模式、成岩成矿模式。根据地层接触关系、构造变形特征、矿床分布规律的研究,证实盖层褶皱推覆运动发生在早喜马拉雅期;盆地内的推覆(滑覆)构造圈闭、走滑断裂构造圈闭、走滑推覆脆-韧性剪切带圈闭、与造山带走向近直交的横向构造圈闭是主要的成岩、成矿空间。通过横断山型陆内造山动力学和喜山期成矿作用研究,分别建立了“横断山型”陆内碰撞造山模式和藏东缘大型复合盆地的成岩成矿模式。     

藏南拆离系锑金成矿特征与成因模式

藏南拆离系是一条重要的锑、金成矿带,呈东西向平行于变质核杂岩带展布。通过对典型矿床成矿特征的研究,识别出3种主要矿床类型:1沙拉岗式锑矿床:受南北向正断层和东西向层间断层控制,矿体为石英-辉锑矿脉,围岩蚀变较弱;2马扎拉式锑-金矿床:主要受间断层控制,局部与南北向断层相关,矿体主要由含金石英-辉锑矿脉体群组成,硅化、绢云母化、绿泥石化和碳酸盐化等围岩蚀变发育;3浪卡子式金矿床:位于变质核杂岩周缘,受剥离断层和正断层控制,矿体呈石英细脉和蚀变岩构成的透镜体,硅化、绿泥石化和绢云母化蚀变强烈。石英流体包裹体测温表明,流体主要为低温和低盐度流体。氢、氧、硫同位素研究显示,沙拉岗式锑矿床具有西藏地热水的特征(δD值为-140‰~-166‰),而马扎拉式锑-金矿床为岩浆水与大气降水的混合,两者的硫同位素大多具有岩浆硫的特征。矿床的形成与变质核杂岩驱动的地热系统密切相关,在变质核杂岩附近形成浪卡子式金矿床,向外形成马扎拉式锑-金矿床,远离核杂岩形成沙拉岗式锑矿床。     

地质灾害卫星遥感监测系统建设方案

地质灾害防治的信息化,是社会发展的必然趋势。如何利用以往的经验积累,并结合最新的科学技术,实现地质灾害防治信息化监测,是社会需要解决的现实问题。笔者根据实际工作经历与掌握的资料,认为通过整合卫星遥感、地质、物化探、地震、地温、深部构造、区域变异、地壳升降等信息,通过计算机技术,可以达到对地质灾害的预测、预报。     

鱼潭水电站地下厂房裂隙层状围岩的变形特征

通过分析鱼潭水电站地下厂房围岩松动圈、块体塌滑,应力变化和收敛位移等特征,揭示了本工程裂隙层状围岩变形破坏的一般规律。     

~(40)Ar/~(39)Ar Thermochronological Constraints on the Timingof Collisional Orogeny in the Mian-Lite Collision Belt,Southern Qinling Mountains

Silurian, Devonian and Carboniferous geological bodies in the Mianxian-Lueyang (Mian-Lue) collisional belt (MLB) and its neighbouring areas, southern Qinling Mountains, China, show similar characteristics of having undergone deformation of two stages. The earlier one, which is inferred to be related to collisional orogeny between the Yangtze and Sino-Korean palaeocontinents based on previous geological data, is responsible for large-scale, north-verging recumbent folds and overthrusts, and associated with low greenschist fades metamorphism. 40Ar/39Ar dating of three muscovite samples taken from different localities yields plateau ages of 226.9±0.9 and 219.5±1.4 Ma and an apparent age of 194.5±3.0 Ma. Thus, the late Triassic collision between the Yangtze and Sino-Korean palaeocontinents has been constrained.     

Kinematic History and Changes in the Tectonic StressRegime during the Cenozoic along the Qinling andSouthern Tanlu Fault Zones

Since the mid-late Eocene, North China has been subjected to extensional stress, resulting in the formation and development of basins. The dynamic origin of this crustal extension has long been an issue of debate. This paper presents the results of kinematic analyses of faults obtained from two seperated areas in North China. In the Weihe graben situated on the southernmost margin of the Ordos block, analyses of fault kinematics were coupled with an analysis of the basin's subsidence history. Three successive extensional tectonic phases accompaning the basin's formation and development have been distinguished. The Palaeogene extension was oriented in a WNW-ESE direction; the Neogene extension in a NE-SW direction and the Pliocene-Quaternary extension in a NW-SE direction. Such changes have also been recorded by fault kinematics along the southern Tanlu fault zone. This has been demonstrated by three successive sets of fault striations indicating normal dip slip resulting from NW-SE extension, then left-     

Characteristics of Upper Mantle Activity in the South China Sea Region and the Indochina Mantle Plume

According to computed results of the mantle traction field beneath the lithosphere based on satellite-modelled gravity anomalies of different degrees, it has been revealed that the three types of mantle convection on different scales existing in the South China Sea region is the key factor controlling the geodynamics. The mantle convection models on large and middle scales have been proved by natural seismic S-wave tomographic data and interpreted by using the present mantle plume concept In consideration of other relevant geological and geophysical data, the authors put emphasis on discussing the expression form, origin and age of the Indochina mantle plume and its important effect on the conversion of organic matter and hydrocarbon accumulation in Cenozoic basins.     

Micro-area Chemical Composition and Preserved P-T Evolution Trace of Phengite in Albite Gneiss from the Donghai Ultrahigh-Pressure Metamorphic Area, East China

Study of micro-area chemical compositions indicates that phengite in albite gneiss from hole ZK2304 of the Donghai region has evident compositional zoning. SiO2 and tetrahedrally coordinated Si contents decrease, and Al2O3, AlIV and AlVI contents increase gradually from core to rim. However, K2O, MgO and FeO contents basically remain unchanged from core to rim. According to P-T estimates obtained from geothermometers and barometers, combined with previous experimental data, the core belt (micro-area I) of phengite was formed at T=637-672℃ and P=1.55-1.73 GPa, and the transitional belt (micro-area II) of the phengite were formed at r=594-654℃ and P=1.35-1.45 GPa. Towards the rim belt (micro-area III), the temperature decreased slightly, but the pressure decreased rapidly with r=542-630℃ and P=1.12-1.19 GPa. The P-T evolution path recorded by the compositional zoning of phengite is characterized by significant near-isothermal decompression, revealing that the gneiss has. undergone high-pressure-ultrahi     

Geological Features of the Eastern Sector of the Bangong Co-Nujiang River Suture Zone: Tethyan Evolution

According to an analysis of the geological features in the eastern sector of the Bangong Co-Nujiang River suture zone, the Tethyan evolution can be divided into three stages. (1) The Embryo-Tethyan stage (Pz1): An immature volcanic arc developed in Taniantaweng (Tanen Taunggyi) Range, indicating the existence of an Embryo-Tethyan ocean. (2) The Palaeo-Tethyan stage (C-T2): During the Carboniferous the northern side of the Taniantaweng Range was the main domain of the Pa-laeo-Tethyan ocean, in which developed flysch sediments intercalated with bimodal volcanic rocks and oceanic tholeiite, and Pemian-Early Triassic arc granites were superimposed on the Taniantaweng magmatic arc; on the southern side the Dengqen-Nujiang zone started secondary extension during the Carboniferous, in which the Nujiang ophiolite developed, and the Palaeo-Tethyan ocean closed before the Middle Triassic. (3) The Neo-Tethyan stage (T3-E): During the Late Triassic the Dengqen zone developed into a relatively matural ocean basin, i