滇黔桂晚海西—中印支伸展裂谷海盆地的演化

在详细研究各类喾体积的相序构成和沉积演化过程的基础上，采用动态成因及地层分析的方法，恢复了已曹受严重构造破坏的滇黔桂伸展裂谷海盆地的地层格架，根据各类等时地层界面的性质和地层序列划分出了５个沉积幕，详细解剖了各沉积幕的三维空间构成。同时以沉积体系或为单位，恢复了各沉积幕中相应阶段的构造古地理环境，将伸展裂谷盆地的演化历史划分为陆壳初始裂陷和洋壳化阶段，盆地伸展扩张阶段、洋壳俯冲和盆地分化段以及盆地     

Evolution of the Extensional Rifted Yunnan-Guizhou-Guangxi Oceanic Basin During the Late Hercynian to Middle Indosinian Stage

On the basis of exhaustive researches on the facies sequences and depositlonal evolutionary process of various depositional systems, the genetic stratigraphic framework of the extensional rifted oceanic basin, which has undergone strong structural destruction, has been reconstructed by means of dynamic genetic stratigraphic analysis. Five depositional episodes have been distinguished from various isochronous stratigraphic boundaries and stratigraphic sequences with the three-dimensional structure of each depositional episode analysed in detail. The tectonic paleogeographic environment corresponding to different stages of each depositional episode has been reconstructed for individual depositional system tracts. And the evolution history of this rifted basin has been divided into four stages' initial rifting and oceanization of continental crust, stretching and spreading of the basin, subduction and basin differentiation, and convergence and collision. A NNE-trending intracontinental soft collision sutur     

Lithosphere formation in the central Slave Craton (Canada): plume subcretion or lithosphere accretion?

Major-element compositions of minerals in peridotite xenoliths from the Lac de Gras kimberlites provide constraints on the mode of lithosphere formation beneath the central Slave Craton, Canada. Magnesia contents of reconstructed whole rocks correlate positively with NiO and negatively with CaO contents, consistent with variable partial melt extraction. Alumina and Cr₂O₃ contents are broadly positively correlated, suggestive of melt depletion in the absence of a Cr–Al phase. Garnet modes are high at a given Al₂O₃ content (a proxy for melt depletion), falling about a 7 GPa melt depletion model. These observations, combined with high olivine Mg# and major-element relationships of FeO-poor peridotites (<7.5 wt%) indicative of melt loss at pressures >3 GPa (residual FeO content being a sensitive indicator of melt extraction pressure), and similar high pressures of last equilibration (∼4.2 to 5.8 GPa), provide multiple lines of evidence that the mantle beneath the central Slave Craton has originated as a residue from high-pressure melting, possibly during plume subcretion. Apparent low melt depletion pressures for high-FeO peridotites (>7.5 wt%) could suggest formation in an oceanic setting, followed by subduction to their depth of entrainment. However, these rocks, which are characterised by low SiO₂ contents (<43 wt%), are more likely to be the result of post-melting FeO-addition, leading to spuriously low estimates of melt extraction pressures. They may have reacted with a silica-undersaturated melt that dissolved orthopyroxene, or experienced olivine injection by crystallising melts. A secular FeO-enrichment of parts of the deep mantle lithosphere is supported by lower average Mg# in xenolithic olivine (91.7) compared to olivine inclusions in diamond (92.6).     

Triassic mid-oceanic sedimentation in Panthalassa Ocean: Sambosan accretionary complex, Japan

Abstract   The Sambosan accretionary complex of southwest Japan was formed during the uppermost Jurassic to lowermost Cretaceous and consists of basaltic rocks, carbonates and siliceous rocks. The Sambosan oceanic rocks were grouped into four stratigraphic successions: (i) Middle Upper Triassic basaltic rock; (ii) Upper Triassic shallow-water limestone; (iii) limestone breccia; and (iv) Middle Middle Triassic to lower Upper Jurassic siliceous rock successions. The basaltic rocks have a geochemical affinity with oceanic island basalt of a normal hotspot origin. The shallow-water limestone, limestone breccia, and siliceous rock successions are interpreted to be sediments on the seamount-top, upper seamount-flank and surrounding ocean floor, respectively. Deposition of the radiolarian chert of the siliceous rock succession took place on the ocean floor in Late Anisian and continued until Middle Jurassic. Oceanic island basalt was erupted to form a seamount by an intraplate volcanism in Late Carnian. Late Triassic shallow-water carbonate sedimentation occurred at the top of this seamount. Accumulation of the radiolarian chert was temporally replaced by Late Carnian to Early Norian deep-water pelagic carbonate sedimentation. Biotic association and lithologic properties of the pelagic carbonates suggest that an enormous production and accumulation of calcareous planktonic biotas occurred in an open-ocean realm of the Panthalassa Ocean in Late Carnian through Early Norian. Upper Norian ribbon chert of the siliceous rock succession contains thin beds of limestone breccia displaced from the shallow-water buildup resting upon the seamount. The shallow-water limestone and siliceous rock successions are nearly coeval with one another and are laterally linked by displaced carbonates in the siliceous rock succession.     

海潮负荷对自由核章动参数拟合的影响

基于武汉基准台超导重力仪重力潮汐观测资料 ,利用根据不同海潮模型获得的负荷重力改正值对观测数据作海潮改正 ,拟合了地球自由核章动 ( FCN)共振参数。结果表明 FCN的本征周期为 435 .2恒星日 ,品质因子为 4730 ,复共振强度为 ( - 6.34× 1 0 - 4,- 0 .0 9× 1 0 - 4)°/h。不同的海潮模型对 FCN本征周期和共振强度实部计算结果的影响很小 ,差异分别不超过± 1 .6%和± 7.7% ,对品质因子 Q值和共振强度虚部拟合结果的影响非常显著。基于 Ori96全球海潮模型得到的重力改正值可以很好地解释武汉基准台周日重力潮汐观测残差。     

岩石层流变学的研究现状及存在问题

岩石层的流变学是一门综合性的学科，它不仅包括高温高压岩力学实验，而且还包括岩石圈的地质构造，物质组成和温度场特性的研究，70年代以来岩石力学实验和地质热研究的成果推动了岩石层流变学的发展，目前，人们应用已有的实验结果建立了岩石层流变学的剖面，并以此为基础讨论了许多大地构造现象，但是，人们对流变机制的转换，水对岩石层流变性的影响等问题尚不清楚，因此，为了深入的了解岩石层流变性质在岩石层运动学和动力学中的应用，必须开展岩石层流变机制的理论和实验研究，以便建立流变性质的三维分布，本文主要分析了岩石层的流变性质随深度变化的研究结果及其在实际中的应用，讨论了确定岩石层粘度或流变强度的主要因素并对岩石层的流变学研究方向提供了一些看法。