Showing papers in "Tectonophysics in 1973"

TL;DR: In this paper, the authors used the theory of bending a stack of thin elastic plates to study the deformation of host rocks during the growth of a laccolithic intrusion.

TL;DR: The shape of sills and laccolithic intrusions and associated host rock deformation were studied at several locations on the flanks of the Henry Mountains Diorite sills range from 05 to 10 m in thickness, are less than 1 km2 in areal extent, and have blunt terminations.

TL;DR: A detailed examination of methods of representing the geometric form of folds in profile section is made in two parts, one dealing with the forms of single layers and the other with the shapes of individual surfaces.

TL;DR: In this article, a two-dimensional model for sheet intrusion propagation based on the elastic deformation around a pressurized elliptical hole is derived, where the deformation is concentrated at the intrusion termination, the site of large principal stress differences and large stress gradients.

TL;DR: In this paper, it is suggested that convection plumes may be rising from the lower mantle to spread out in the asthenosphere and drive lithospheric plates about and thus possibly provide the primary mechanism which governs the behavior of the earth's surface.

TL;DR: In this article, deformation paths arising from tectonic deformation with progressive volume loss superposed on previously compacted material are computed, and these lead to predicted deformation fields which accord well with much of the data available on natural deformation field.

TL;DR: In this article, the origin of fold axes oblique to the regional attitude is interpreted in terms of rotation of the axes due to stretching within the axial plane of the folds.

TL;DR: In this paper, the authors compare natural assemblages with experimentally determined phase equilibria and oxygen isotopic analyses to obtain an upper bound on the geothermal gradient in the range 150-500°C at fluid pressures on the order of 3-8 + kbar.

TL;DR: In this paper, the development of folds in single viscous layers embedded in a less viscous matrix, shortened parallel to the layering under conditions of plane strain and pure shear was studied.

TL;DR: Partial melting experiments on spinel-lherzolite, a rock which probably occurs in relatively shallow parts of the oceanic upper mantle, demonstrate that alkali basaltic melt is formed at depths of at least 20 kbar whereas tholeiitic melts are formed at lower pressures as discussed by the authors.

TL;DR: In this paper, a critical review of high-temperature flow mechanisms in ceramics and their relation to empirical flow laws is presented, and the authors conclude that these fine-grained materials creep primarily by a quasi-viscous grain-boundary sliding mechanism which is unlikely to predominate in the deep interior.

TL;DR: In this paper, the effect of viscosity ratios, thickness ratios and applied stresses on boudinage initiation is examined by considering the theoretical stress distribution in a homogeneously deformed plane strain model, which consists of welded, rhythmically layered units with different viscosities.

TL;DR: The existence in the Carpathian area of two linear zones with basic and ultrabasic rocks and of intermediate-composition intrusive rocks and volcanics situated in zones more or less parallel to the first ones, in accordance with the age of their formation, allow of the supposition of the existence of two intracontinental basins with oceanic-type floor which were active from the Triassic to the Cretaceous as mentioned in this paper.

TL;DR: In this paper, the authors present a review of the results of experiments conducted in experimental petrology and geochemistry to evaluate contamination of basic magmas, anatexis of sialic crust, differentiation of basaltic magmas and anatroxis of wet peridotite mantle.

TL;DR: In this article, the formation of the melts which produce intrusions of the granite family are considered to result from the partial fusion of high-grade metamorphic rocks, and the melting behaviour of such materials is considered.

TL;DR: In this paper, the strain tensor theory was generalized to the case of planar angular distributions, where the tensor tensor is replaced by the transposed inverse of the tensors.

TL;DR: The pyrolite model composition provides a satisfactory source composition for mantle-derived magmas insofar as major elements and compatible trace elements are concerned but there is evidence for mantle inhomogeneity in the abundances of “incompatible” minor and trace elements (e.g., K, Ti, P, Rb, Sr, light rare earth elements etc.). as mentioned in this paper.

TL;DR: In this paper, a new theory for single-layer buckling was developed, where the layer is not parallel to the principal stresses, and it is shown that stress refraction is a necessary condition for this system, and an expression is derived for its value in terms of η, η 1 and θ.

TL;DR: A pair of paired metamorphic belts is composed of two contrasting belts running parallel: a high-pressure metmorphic belt which probably formed beneath a trench zone, and a low-pressure meta-metamorphic belt that probably formed under a volcanic chain in the adjacent island arc or continental margin this paper.

TL;DR: In this article, two types of relationship between the shallow and deep seismic activities in island-arc regions are described: 1) a great shallow earthquake in a region is preceded and sometimes followed by the marked increase of deep seismic activity in the same down-dip seismic zone perpendicular to the trend of an arc structure.

TL;DR: In this paper, the authors examined the progressive development of folds by buckling in single isolated viscous layers compressed parallel to the layering and embedded in a less viscous host.

TL;DR: In this paper, the eugeosynclinal ophiolites are reconstructed in the orogenic belt of Central Asia and a structural-magmatic zonal pattern appears to be governed by the ancient Benioff zone along which energy and light lithophile substance ascended as mantle diapir.

TL;DR: In this paper, the changes in quartz microfabric, which includes microstructure and c-axis patterns of preferred orientation, are examined in a prograde regional metamorphic sequence of pure quartzites.

TL;DR: The results of radiometric dating of granitic rocks around Kotanopan near the west coast of Central Sumatra indicate an average age of 45 million years as discussed by the authors, which can be used for a fresh analysis of the geological evolution of Indonesia based on the plate-tectonics concept.

TL;DR: The new global tectonics provides a convenient tectonic framework for igneous and metamorphic petrology in the five environments: oceanic plates, continental plates, divergent plate boundaries, convergent plate boundary, and transform plate boundaries.

TL;DR: In this article, the authors studied the crustal structure of the Hawaiian Archipelago, northern Melanesia, and parts of the Central Pacific Basin using seismic refraction methods and found that the systematic variation found in crustal thickness in the Hawaiian Islands is explainable by a hypothesis of differential subsidence.

TL;DR: The sialic basement of New Caledonia is a Permian-Jurassic greywacke sequence which was folded and metamorphosed to prehnite-pumpellyite or low-grade greenschist facies by the Late Jurassic.

TL;DR: In this article, a series of minor folds developed in the Moine rocks of Monar, Scotland, have been studied in detail using various geometrical methods of analysis and are interpreted as having formed by a process involving both buckling and uniform shortening.

TL;DR: In this paper, an axial growth of en-echelon cleavage cracks, inclined at angles smaller than 45°, was observed in feldspar during deformation of a pegmatite having a mineralogy and texture similar to granite.

TL;DR: In this article, a plate-tectonics model was used to compute radial temperature profiles for various spreading velocities for the region bounded by the bottom of oceanic layer two, the top of the lowvelocity zone, the center of the ridge, and a vertical plane at 1000 km away from the ridge centre.