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140 results on '"Blundell, D. J."'

12. Evidence for early Proterozoic plate tectonics from seismic reflection profiles in the Baltic shield

Author

Hobbs, R. W., Klemperer, S. L., Matthews, D. H., Snyder, D. B., Long, R., Blundell, D. J., Palm, H., Roberts, R. G., Elming, S. A., Heikkinen, P., Korhonen, H., Luosto, U., Hjelt, S. E., Komminaho, K., Yliniemi, J., Meissner, R., Sadowiak, P., Wever, Th, Dickmann, T., Flueh, E. R., Thybo, H., Balling, N., and Nørmark, E.

Subjects
Paleontology, Tectonics, Plate tectonics, Multidisciplinary, Proterozoic, Reflection (physics), Baltic Shield, Geology
Abstract

Plate tectonics provides the linking framework for all tectonic and magmatic activity seen today, but it is not known when plate tectonics first developed on Earth. New deep seismic reflection and coincident refraction profiles across an exposed, 1.89-Gyr-old volcanic arc complex show a 10-km-thick offset in the Moho and bivergent reflectors in the crust, which were most probably created by plate convergence, subduction and accretion during the Early Proterozoic. Hence, plate tectonic models seem to be applicable for at least the second half of Earth's history.

Published
1990

15. Deep seismic survey images crustal structure of Tornquist Zone beneath southern Baltic Sea

Author

Sadowiak, P., Thomas, S., Wever, T., Dickmann, T., Flüh, E., Berthelsen, A., Thybo, H., Dahl-Jensen, T., Balling, N., Nørmark, E., Hobbs, R. W., Klemperer, L., Matthews, D. H., Snyder, D. B., Long, R., Graham, D., Matthews, T., Blundell, D. J., Lund, C., Palm, H., Pedersen, L., Roberts, R., Elming, S. E., Heikkinen, P., Korhonen, H., Luosto, U., Hjelt, S. E., Komminaho, K., and Yliniemi, J.

Subjects
Geophysics, General Earth and Planetary Sciences
Abstract

The Tornquist Zone is Europe's longest tectonic lineament and bisects the continent in a NW‐SE direction from the North Sea (off NW Denmark) to the Black Sea. New deep seismic reflection and coincident refraction data have been collected across its 50km wide, intensely faulted and inverted NW part. The marine reflection profile in the area north of Bornholm Island shows a tilted block structure in the rigid upper crust, whereas the lower crust seems to be more gently uplifted. A complex transition from the highly reflective lower crust to the mantle is indicated by mantle reflections and a curious wide‐angle event recorded by a landstation on Bornholm Island. We suggest that deep‐reaching inversion tectonics, induced by Alpine and Carpathian orogeny, were responsible for the development of the gross crust‐mantle structure of the Tornquist Zone in our study area, which seems to be similar to that in Poland.

Published
1991

36. SCIENTIFIC COMMUNICATIONS.

Author

Blundell, D. J., Karnkowski, P. H., Alderton, D. H. M., Oszczepalski, S., and Kucha, H.

Subjects
COPPER, STRATIGRAPHIC geology, MINERAL industries, EOLIAN processes, GEOMORPHOLOGY
Abstract

Fluid flow models previously proposed have been unable to account for the 350 Mt of copper metal associated with the Kupferschiefer shales in the southwest part of the Polish basin without an unreasonably high concentration of Cu in the brine transport system. A new conceptual model is presented, on the basis of more detailed knowledge of the structural, stratigraphic and thermal evolution of the Polish basin, that involves a localized high heat flow anomaly present at the time of the main phase of mineralization in the Early Triassic. The mechanism proposed involved injection of hot brine from a deep-seated basement fault-fracture system into Rotliegend eolian sandstone and then updip flow through this porous formation to the Lubin area, where chemical conditions in the immediately overlying Kupferschiefer shale allowed precipitation of the metals from the brine. The copper mineralization of the Lubin area is suggested to have resulted from a large number of short pulses of fluid, and flow was triggered by coseismic strain associated with normal faulting. It is proposed that, within the basement, a network of fractures with high aspect ratios opened within each interseismic period under lateral tension and filled with brine. At the time of a normal-fault-related earthquake, when fault rupture occurred, coseismic strain resulted in the closure of fractures in the vicinity of the fault and brine was expelled. Calculations suggest that, with fluid pressure generated by the coseismic strain close to lithostatic, the force from hot brine injected into the Rotliegend sandstone was sufficient to drive the brine through the aquifer at up to 63 m/yr to the site of copper deposition in the Kupferschiefer shale. If flow from each earthquake lasted, on average, for just over a year, then approximately 0.07 km³ of fluid would have been discharged. If earthquakes and normal faulting occurred at 100- to 200-yr intervals, averaging 7,000/m.y., then 6,000 km³ of... [ABSTRACT FROM AUTHOR]

Published
2003

38. General discussion.

Author

Kléman, M., Coles, H. J., Meyer, R. B., Berry, G. C., Singer, L. S., Flory, P. J., Krigbaum, W. R., Wissbrun, K. F., Mitchell, G. R., Mackley, M. R., Blundell, D. J., Griffin, B., Windle, A. H., Keller, A., Thomas, E. L., and Zentel, R.

Published
1985
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49. Critical Role of Diffraction Simulation in Establishing the Crystal and Molecular Structures of Poly(biaryl ether ketone)s

Author

Aldred, P. L., Colquhoun, H. M., Williams, D. J., and Blundell, D. J.

Abstract

Molecular modeling and diffraction simulation studies of the biphenyl-based poly(ether ketone)s [O−Ar−Ar−O−Ar−CO−Ar−Ar−CO−Ar−]n (3) and [−O−Ar−Ar−CO−Ar−]n (4, Ar = 1,4-phenylene), coupled with data obtained from an oligomer single-crystal study, have enabled their crystal and molecular structures to be determined from X-ray powder data. A crystallographically disordered structure in which the ether and ketone linkages are distributed randomly over the bridging positions of the polymer chain is potentially available to both polymers and undoubtedly occurs in their random 1:2 copolymer (5). The disordered structure is monoclinic (rather than orthorhombic as has previously been proposed), in space group P21/b, with two chains per unit cell. Rietveld refinement of this structure for polymers 3 and 4, based on X-ray powder data, gave final agreement factors (Rwp) of 5.7% and 6.6%, respectively. Analysis of X-ray fiber data by diffraction simulation methods suggests that the disordered structure always predominates for 3 but that a partially ordered arrangement of ether and ketone linkages is present in oriented samples of polymer 4.

Published
2002
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