孕震系统中的1/f噪声行为

根据自组织临界现象理论,研究7海城、唐山等7个大地震前、后中小地震的活动特征,计算了不同孕震时期地震活动的功率谱特征.初步结果表明描述地震活动的谱幂律指数p值在大震发生前有明显的增高倾向.主震前一年及主震当年,p值一般落在闪变噪声的谱域,其他时间一般很小.最后讨论了地震孕育的物理过程及孕震系统的稳定性.     

广东莲花山斑岩型钨-金矿床蚀变矿化特征及分带模式

莲花山斑岩型钨－金矿床蚀变类型可以分作钾化、云英岩化、绢云母化、绿泥石化和青盘岩化。矿化表现为黑钨矿化、白钨矿－硫化物矿化、多金属硫化物矿化及黄铁矿化。蚀变在水平和垂向上具有分带性。由内向外由钾化向云英岩化、叠加蚀变带、绿泥石化＋绢云母化、青盘岩化转化。由浅向深，钾化增强，云英岩化减弱，被叠加蚀变带和绿泥石化及绢云母化所代替。矿化由内向外表现为由黑钨矿化向白钨矿化、多金属硫化物矿化、黄铁矿化转变，由浅向深由钨矿化转变为金矿化及多金属硫化物矿化。与典型斑岩型矿床蚀变分带对比，莲花山斑岩型矿床不同原岩类型蚀变特征变化较大，矿化则表现出富钨、金贫铜及钨金共同产出的特征。     

陕西省区域环境地球化学分区

为了利用地壳元素分布特征与动植物微量元素含量间的关系,指导生态环境综合治理,借助已有的基础地球化学资料,进行陕西省地球化学分区,确定各分区的环境背景值、污染起始值、缺乏临界值、过剩值临界值,并将陕西省分为陕北、关中、陕南3个地球化学区,圈定了1个元素贫化区和2个元素富集区。提出应该在元素的缺乏和过剩的异常区内进行生物体内微量元素含量的定期检测。做到对地球化学疾病及时发现及时寻找对策,以保证人类生存环境的安全,提高生存质量。     

Mantle Xenoliths from the Southeastern Slave Craton: Evidence for Chemical Zonation in a Thick, Cold Lithosphere

We present the first data on the petrology of the mantle lithosphereof the Southeastern (SE) Slave craton, Canada. These are basedon petrographic, mineralogical and geochemical studies of mantlexenoliths in Pipe 5034 of the Cambrian Gahcho Kué kimberlitecluster. Major types of mantle xenoliths include altered eclogite,coarse garnet or spinel peridotite, and deformed garnet peridotite.The peridotites belong to the low-temperature suite and formedat T=600–1300°C and P= 25–80 kbar in a thick(at least 220–250 km), cool lithosphere. The SE Slavemantle is cooler than the mantle of other Archaean cratons andthat below other terranes of the Slave craton. The thick lithosphereand the relatively cool thermal regime provide favourable conditionsfor formation and preservation of diamonds beneath the SE Slaveterrane. Similar to average Archaean mantle worldwide, the SESlave peridotite is depleted in magmaphile major elements andcontains olivine with forsterite content of 91–93·5.With respect to olivine composition and mode, all terranes ofthe Slave mantle show broadly similar compositions and are relativelyorthopyroxene-poor compared with those of the Kaapvaal and Siberiancratons. The SE Slave spinel peridotite is poorer in Al, Caand Fe, and richer in Mg than deeper garnet peridotite. Thegreater chemical depletion of the shallow upper mantle is typicalof all terranes of the Slave craton and may be common for thesubcontinental lithospheric peridotitic mantle in general. Peridotiticxenoliths of the SE Slave craton were impregnated by kimberliticfluids that caused late-stage recrystallization of primary clinopyroxene,spinel, olivine and spinel-facies orthopyroxene, and formationof interstitial clinopyroxene. This kimberlite-related recrystallizationdepleted primary pyroxenes and spinel in Al. The kimberliticfluid was oxidizing, Ti-, Fe- and K-rich, and Na-poor, and introducedserpentine, chlorite, phlogopite and spinel into peridotitesat P < 35 kbar. KEY WORDS: kimberlite xenolith; lithosphere; mantle terrane; chemical zoning; thermobarometry; Slave craton     

昆明市东川区泥石流信息系统的建立及其应用

根据东川区泥石流的成因、泥石流灾害信息源、各类数据的表达方式及泥石流信息系统的应用等，对东川区泥石流信息系统进行了系统分析，在此基础上利用3S技术，在ARCVIEW的AVENUE开发语言支持下，集成各类数据，建立东川区泥石流信息系统，最后讨论了该系统在泥石流危险度区划及灾害趋势分析中的应用。     

Application of Characteristics of Seismogenic Structures in the Determination of Parameter of Potential Seismic Source Areas

INTRODUCTIONThe method of probabilistic seismic risk analysis was proposed by Cornell in1968(Cornell,1968).After more than30years development,it has become the main method for seismic riskassessment of engineering sites and seismic zonation,and has been u…     

Characteristics of Energy Accumulation and Release of Seismogenic Tectonics and Seismic Risk Analysis in Some Areas in the Tianshan Mountains, Xinjiang1

INTRODUCTIONHowtocombinethestudyofseismogenictectonicswithearthquakepredictionisanurgentscientificdifficulty .Thereexistbiggapsbetweenstudymethodsandcurrentknowledgeonseismogenitectonics ,earthquakeprediction ,seismogenesisandthephysicsofearthquakeoccurre…     

Chemical and textural equilibration of garnet during amphibolite facies metamorphism: The influence of coupled dissolution–reprecipitation

Metamorphic equilibration requires chemical communication between minerals and may be inhibited through sluggish volume diffusion and or slow rates of dissolution in a fluid phase. Relatively slow diffusion and the perceived robust nature of chemical growth zoning may preclude garnet porphyroblasts from readily participating in low‐temperature amphibolite facies metamorphic reactions. Garnet is widely assumed to be a reactant in staurolite‐isograd reactions, and the evidence for this has been assessed in the Late Proterozoic Dalradian pelitic schists of the Scottish Highlands. The 3D imaging of garnet porphyroblasts in staurolite‐bearing schists reveals a good crystal shape and little evidence of marginal dissolution; however, there is also lack of evidence for the involvement of either chlorite or chloritoid in the reaction. Staurolite forms directly adjacent to the garnet, and its nucleation is strongly associated with deformation of the muscovite‐rich fabrics around the porphyroblasts. “Cloudy” fluid inclusion‐rich garnet forms in both marginal and internal parts of the garnet porphyroblast and is linked both to the production of staurolite and to the introduction of abundant quartz inclusions within the garnet. Such cloudy garnet typically has a Mg‐rich, Mn‐poor composition and is interpreted to have formed during a coupled dissolution–reprecipitation process, triggered by a local influx of fluid. All garnet in the muscovite‐bearing schists present in this area is potentially reactive, irrespective of the garnet composition, but very few of the schists contain staurolite. The staurolite‐producing reaction appears to be substantially overstepped during the relatively high‐pressure Barrovian regional metamorphism reflecting the limited permeability of the schists in peak metamorphic conditions. Fluid influx and hence reaction progress appear to be strongly controlled by subtle differences in deformation history. The remaining garnet fails to achieve chemical equilibrium during the reaction creating distinctive patchy compositional zoning. Such zoning in metamorphic garnet created during coupled dissolution–reprecipitation reactions may be difficult to recognize in higher grade pelites due to subsequent diffusive re‐equilibration. Fundamental assumptions about metamorphic processes are questioned by the lack of chemical equilibrium during this reaction and the restricted permeability of the regional metamorphic pelitic schists. In addition, the partial loss of prograde chemical and textural information from the garnet porphyroblasts cautions against their routine use as a reliable monitor of metamorphic history. However, the partial re‐equilibration of the porphyroblasts during coupled dissolution–reprecipitation opens possibilities of mapping reaction progress in garnet as a means of assessing fluid access during peak metamorphic conditions.     

Controls on metamorphic equilibration: the importance of intergranular solubilities mediated by fluid composition

A dramatic demonstration of the role of intergranular solubility in promoting chemical equilibration during metamorphism is found in the unusual zoning of garnet in pelitic schist exposed at Harpswell Neck, Maine, USA. Many garnet crystals have irregular, patchy distributions of Mn, Cr, Fe and Mg in their inclusion‐rich interiors, transitioning to smooth, concentric zoning in their inclusion‐poor outer rims; in contrast, zoning of Ca and Y is comparatively smooth and concentric throughout. We re‐assess the disputed origin of these zoning features by examining garnet growth in the context of the thermal and structural history of the rocks, and by evaluating the record of fluid–rock interaction revealed in outcrop‐scale veining and fluid‐inclusion assemblages. The transition in the character of garnet zoning correlates with the onset of a synkinematic, simple‐shear‐dominated phase of garnet growth and with a shift in the composition of the intergranular fluid from CO₂‐rich to H₂O‐rich. Compositional variations in garnet are therefore best explained by a two‐stage growth history in which intergranular diffusive fluxes reflect differences in the concentration of dissolved species in these two contrasting fluids. Interiors of garnet crystals grew in the presence of a CO₂‐rich fluid, in which limited solubility for Mn and Cr (and perhaps Fe and Mg) produced patchy disequilibrium overprint zoning, while appreciable solubility for Ca and Y permitted their rock‐wide equilibration. Rims grew in the presence of an H₂O‐rich fluid, in which high intergranular concentrations for all elements except Cr enabled diffusion over length scales sufficient for rock‐wide equilibration. This striking example of partial chemical equilibrium during reaction and porphyroblast growth implies that thermal effects may commonly be subsidiary in importance to solubilities in the intergranular medium as determinants of length scales for metamorphic equilibration.