Global tectonic relations—a project for the future

Global tectonic relations—a project for the future

OLR (1986)33 (12) D. SubmarineGeologyand Geophysics of Linosa where volcanic activity is related to structures paralleling the Lampedusa trend. In t...

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OLR (1986)33 (12)

D. SubmarineGeologyand Geophysics

of Linosa where volcanic activity is related to structures paralleling the Lampedusa trend. In the central Mediterranean area, NW-SE trending structures are characterized by normal faulting and are found from SE Sicily to central Tunisia. A second NNW-SSE trending fault pattern reveals evidence of sinistral motion commencing in Upper Miocene and continuing to Recent time. The movements associated with the two fault trends are consistent with a northwestward maximal horizontal compressive stress. Ist. Sci. della Terra, Univ. di Catania, Corso Italia 55, 95129 Catania, Italy. 86:6944 Ishida, Mizuho, 1986. The configuration of the Philippine Sea and Pacific plates as estimated from the high-resolution microearthquake hypocenters in the Kanto-Tokai District, Japan.

Rept natn. Res. Cent. Disaster Prevent., Tokyo, 36:1-19. (In Japanese, English abstract.) Microearthquake distributions are used to delineate the Philippine Sea and Pacific plates. The upper surfaces (beneath the Eurasian Plate) of the subducting slabs are 10 to 20 km shallower than previously estimated, based on an estimate of slab surface ca. 10 km above the inclined seismic zone. The Pacific Plate slab configuration offered no surprises; the Philippine Sea Plate showed some differences from previously published results. Natl. Res. Center for Disaster Prevention, Japan. (slr) 86:6945 Page, R.A. et al., 1986. Accretion and subduction tectonics in the Chugach Mountains and Copper River Basin, Alaska: initial results of the TransAlaska Crustal Transect. Geology, geol. Soc. Am., 14(6):501-505. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA. 86:6946 Reuther, C.D., 1984. Tectonics of the Maltese Islands. CENTRO, 1(1):1-20. Geol. Inst., Univ. Karlsruhe, Kaiserstrasse, 12,6500 Karlsruhe FRG. 86:6947 Searle, R.C. and J. Francheteau, 1986. Morphology and tectonics of the Galapagos Triple Junction [of the Pacific, Cocos, and Nazca plates]. Mar. geophys. Res., 8(2):95-129. All three plate boundaries change character as the triple junction is approached: the fast-spreading EPR develops the morphology of a medium-spreading rise, and the medium-spreading Cocos-Nazca Rise takes on the appearance of a slow-spreading ridge. The EPR axis was continuous throughout the

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survey area, where it runs along the 102°05"W meridian. The Cocos-Nazca axis, however, fails to meet it, leaving a 20-km-wide band of apparently normal EPR crust between its tip and the EPR axis, implying considerable intra-plate deformation within the Cocos and Nazca plates. True sea-floor spreading on the Cocos-Nazca axis apparently does not begin until 60 km east of the EPR axis. We present a model involving intermittent rifting, rift propagation, and sea-floor spreading, to explain these observations. Includes 4-color outfold: Topography of the Galapagos Triple Junction. Inst. of Oceanogr. Sci., Brook Rd., Wormley, Godalming, Surrey GU8 5UB, UK. 86:6948 Srimal, Neptune, 1986. India-Asia collision: implications from the geology of the eastern Karakoram [NW India]. Geology, geol. Soc. Am., 14(6):523-527. Dept. of Geol. Sci., Univ. of Rochester, NY 14627, USA. 86:6949 Utkin, V.P., 1985. The geodynamics of crustal spreading in the transition zone from the Asian continent to the Pacific Ocean. Geotectonics (a translation of Geotektonika), 19(1):51-63. The tectonomagmatic processes of the transition zone are regarded as a reflection of lateral displacements of the articulated Asian and Pacific Ocean blocks of tectonosphere. Crustal spreading of the transition zone is a result of wrench activation of deep-seated faults; spreading along the northeastern system of wrench faults led during Late Cretaceous time to large-scale release of deep-seated energy and material with the development of the East Asian volcanic belt. During Cenozoic time, wrench activation was responsible for the development of the continental basins and marginal seas. Far Eastern Geol. Inst., Acad. of Sci., USSR. 86:6950 Zolotarev, V.G., 1986. Geodynamic characteristics of the Mricano-Sicilian sill. Okeanologiia, 26(2): 261-266. (In Russian, English abstract.)

D250. Plate and global tectonics 86:6951 Bath, Markus, 1985. Global tectonic relations--a project for the future. Rept seism. Inst., Uppsala, 4-85:32pp. During the 48-year period 1927-74, earthquake activities in Greece and the Kurile Islands are

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D. Submarine Geology and Geophysics

significantly correlated to each other, which could indicate direct or indirect connections between the respective tectonic motions. In combination with earlier examples of significant correlations between the seismic activities in Sweden and the world as well as in Greece and the world, the present result may suggest that global tectonic relations are a physical reality. Seismol. Dept., Uppsala Univ., Sweden.

86:6952 Nedoma, J., 1986. On the geodynamic model of the Earth and the plate tectonic hypothesis. Part I. The geodynamic model and fundamental equations. Gerl. Beitr. Geophys., 95(I):36-62. The aim of the present paper is to build a geodynamic model of the Earth in a form applicable to all geophysical fields, and to find a general system of valid equations. Gen. Comp. Centre, Acad. Sci., 182 07 Praha, 8-Liben, Czechoslovakia.

86:6953 Weijermars, Ruud, 1986. Slow but not fast global expansion may explain the surface dichotomy of Earth. Phys. Earth planet. Interiors, 43(1):67-89. Various fast and slow Earth expansion hypotheses are reviewed. Inward migration of the core-mantle boundary due to the differentiation and progressive solidification of the liquid outer core might have caused expansion of the Earth's radius at a 'slow' mean rate of 0.5 mm a ~. A slowly expanding Earth could explain why two distinct types of lithosphere exist: oceanic and continental. The Hans Ramberg Tectonic Lab., Uppsala Univ., Box 555, S-75122 Uppsala, Sweden.

OLR (1986) 33 (12)

86:6955 Papadopoulos, G.A., 1986. Large intermediate depth shocks and volcanic eruptions in the Hellenic Arc during 1800-1985. Phys. Earth planet. Interiors, 43(1):47-55.98 Mavromichali str., 11472 Athens, Greece. 86:6956 Poreda, R., J.-G. Schilling and H. Craig, 1986. Helium and hydrogen isotopes in ocean-ridge basalts north and south of Iceland. Earth planet. Sci. Lefts, 78(1):1-17. Observations of 'plume type' 3He/4He ratios (R greater than 8 RA) show that the effect of the Icelandic mantle plume on He isotope ratios is observable along the Reykjanes Ridge and to 70°N on the Kolbeinsey Ridge. These ridges are unique among all MOR segments studied to date in possessing high He isotopic ratios along their entire lengths. North of 70°N, Jan Mayen province basalts have He ratios somewhat lower than 6.8-8.0 R A. The He distributions do not correspond in detail to trace element variations; the concentration and H isotopic composition of water in these basalts reveal a good positive correlation with trace element data. Between 61°-63°N on the Reykjanes Ridge, the concentration of water in basalts is high and the water is enriched in deuterium; south of 61°N the concentration and isotopic composition of water exhibit normal MORB values. The Mohns Ridge basalts have elevated water concentrations and an isotopic composition (-44 to -66 ppt) unique among MOR basalts. Isotope Lab., Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA.

D280. Volcanism, magmatism

D290. Crust, mantle, core

86:6954 Marty, Bernard and Minoru Ozima, 1986. Noble gas distribution in oceanic basalt glasses. Geochim. cosmoehim. Acta, 50(6): 1093-1097.

86:6957 Belousov, V.V. and N.I. Pavlenkova, 1985. Types of the crust of the Earth. Geotectonics (a translation of Geotektonika), 19(1): 1-9.

Experiments indicate a strong noble gas partitioning into CO2-filled vesicles. An inhomogeneous distribution of argon isotopes within individual glasses is observed in several cases, believed to result from the combined effects of the deep-seated component partitioning into vesicles and contamination of the residual component dissolved in the glass by atmospheric noble gases. Using a mixing diagram, we are able to discriminate against atmospheric contamination and estimate the Ar partition coefficients (in qualitative agreement with the Henry's law constant for silicate melts). I M R G / B R G M BP6009, 45060 Orleans Cedex, France.

Six types of crust are identified from certain structural parameters in order to work out methods of generalized mapping of the Earth's deep structure. These parameters are thickness of the crust, thickness of the sedimentary mantle, and the mean seismic velocity in the consolidated part of the crust. O.Yu. Schmidt Inst. of the Phys. of the Earth, USSR.

86:6958 Garfunkel, Z., C.A. Anderson and G. Schubert, 1986. Mantle circulation and the lateral migration of subducted slabs. J. geophys. Res., 91(B7):72057223.