When continents rift to form new ocean basins, the rifting is sometimes accompanied by massive igneous activity. We show that production of magmatically active rifted margins and effusion flood basalts onto adjacent can be explained a simple model above thermal anomaly in underlying mantle. The rocks are generated decompression melting hot asthenospheric mantle as it rises passively beneath stretched thinned lithosphere. Mantle plumes generate regions lithosphere typically 2000 km diameter...

Journal Article The Volume and Composition of Melt Generated by Extension the Lithosphere Get access D. McKENZIE, McKENZIE Department Earth Sciences, Bullard LaboratoriesMadingley Road, Cambridge CB3 0EZ Search for other works this author on: Oxford Academic Google Scholar M. J. BICKLE Petrology, 29, Issue 3, June 1988, Pages 625–679, https://doi.org/10.1093/petrology/29.3.625 Published: 01 1988 history Received: 21 July 1987 Accepted: 14 January

Examination of more than 100 fault plane solutions for earthquakes within the Alpide belt between Mid-Atlantic ridge and Eastern Iran shows that deformation at present occurring is result small continental plates moving away from Turkey Western Iran. This pattern movement avoids thickening crust over much by consuming Mediterranean sea floor instead. The rates relative motion two involved, Aegean Turkish plates, are estimated, but only perhaps 50 per cent true values. These estimates then...

Journal Article Partial Melt Distributions from Inversion of Rare Earth Element Concentrations Get access DAN McKENZIE, McKENZIE Institute Theoretical Geophysics, Bullard Laboratories, Department SciencesMadingley Road, Cambridge CB3 OEZ, UK Search for other works by this author on: Oxford Academic Google Scholar R. K. O'NIONS Petrology, Volume 32, Issue 5, October 1991, Pages 1021–1091, https://doi.org/10.1093/petrology/32.5.1021 Published: 01 1991 history Received: 10 August 1990 Accepted: 20 March

Journal Article The Generation and Compaction of Partially Molten Rock Get access DAN McKENZIE Bullard Laboratories the Department Earth Sciences, Madingley RiseMadingley Road, Cambridge CB3 OEZ, U.K. Search for other works by this author on: Oxford Academic Google Scholar Petrology, Volume 25, Issue 3, August 1984, Pages 713–765, https://doi.org/10.1093/petrology/25.3.713 Published: 01 1984 history Received: 09 September 1983 Revision received: 16 March

New fault plane solutions, Landsat photographs, and seismic refraction records show that rapid extension is now taking place in the northern eastern parts of Aegean sea region. The southern part has also been deformed by normal faulting but relatively inactive. In northwestern Greece Albania there a band thrusting near western coasts adjacent to further east. pre-Miocene geology islands closely resembles Turkey, yet shows crust only about 30 km thick beneath sea, compared with nearly 50...

Seismic refraction results show that the igneous section of oceanic crust averages 7.1±0.8 km thick away from anomalous regions such as fracture zones and hot‐spots, with extremal bounds 5.0–8.5 km. Rare earth element inversions melt distribution in mantle source region suggest sufficient is generated under normal spreading centers to produce an 8.3±1.5 crust. The difference between thickness estimates seismics rare not significant given uncertainties composition, though it magnitude would...

Over 80 new fault plane solutions, combined with satellite imagery as well both modern and historical observations of earthquake faulting, are used to investigate the active tectonics Middle East between western Turkey Pakistan. The deformation part this region is dominated by movement continental material laterally away from Lake Van in eastern Turkey. This helps avoid crustal thickening region, allows some shortening Arabia Eurasia be taken up thrusting over oceanic-type basement southern...

Plate theory has successfully related sea floor spreading to the focal mechanisms of earthquakes and deep structure island arcs. It is used here calculate temperature distribution in lithosphere thrust beneath arcs, determine flow stress elsewhere mantle. Comparison with observations demonstrates that are restricted those regions mantle which colder than a definite temperature. The heating can maintain high heat anomaly observed behind also suggests new approach convection problem. most...

When crust thickens during crustal shortening, the underlying mantle lithosphere must shorten and thicken also, causing submersion of cold, dense material into surrounding asthenosphere. For a range physical parameters thickened boundary layer that forms transition from strong to convecting asthenosphere may become unstable, detach, sink asthenosphere, be replaced by hotter asthenospheric material. We have studied instability for (Rayleigh number), amounts thickening, conditions. In all...

In this paper we examine the connection between westward motion of Turkey relative to Europe and extension in around Aegean Sea. The principal new data available since last attempt synthesize tectonics region by McKenzie (1978) are much improved focal mechanisms earthquakes, constrained P SH body wave modelling as well first motions. These show that faulting western part is mostly extensional nature, on normal faults with a NW WNW strike slip vectors directed NNW NNE. There evidence from...

This paper is concerned with the relationship between overall motion across a zone of distributed continental deformation and seismic moment tensors earthquakes that occur within it. The in described by gradient tensor L, which may be split into symmetric part, S, an antisymmetric A. S strain tensor, can always determined from sum tensors, following result Kostrov (1974). A corresponds to rigid body rotation, principle unobservable seismically: contain no information about A, regardless...

Summary All available ship and aeroplane tracks across the Indian Ocean were searched for identifiable magnetic anomalies transform faults, hence age direction of motion at time formation about two-thirds floor ocean established. The lineations show that India moved away from Antarctica 18 cm/y 20 My in Early Tertiary. This rapid ceased Eocene was followed by a period which little or no spreading took place west Ninety East Ridge. Australia separated during this period. present episode began...

Plate tectonics provides a remarkably accurate kinematic description of the motion earth's crust but fully dynamical theory requires an understanding convection in mantle. Thus properties plates and mantle must be related to systematic study convection. This paper reviews both geophysical information fluid dynamics Boussinesq infinite Prandtl number. Numerical experiments have been carried out on several simple two-dimensional models, which is driven by imposed horizontal temperature...

abstract The stresses involved in shallow earthquakes and their occurrence along fault planes suggest that they occur by failure on weak planes, rather than brittle fracture of a homogeneous material. Possible orientations the stress tensor are examined to determine what limits plane solutions can place orientation greatest principal stress. For general case triaxial stress, only restriction is this direction must lie quadrant containing P, but may be at right angles P direction. Thus impose...

We discuss the geological, geophysical, and petrological observations that constrain nature of mantle convection in plumes, show how theoretical models plumes have developed over past three decades. The large volumes lava emplaced geologically short periods as flood basalts are generated mainly by decompression melting abnormally hot brought to base lithosphere plumes. present new results from application McKenzieand O'Nions' (1991) rare earth element inversion scheme geochemistry infer...