Both vpm and nvpm form during rifting, when a continent rifts to form a new ocean basin. Instead of intrusive magmatic structures, the transitional cru. Nvpm are different from vpm because of a lack of volcanism. It outlines the geological, geophysical and petrological observations that characterize extensional systems, and how such observations can guide and constrain dynamic and kinematic models of continental lithosphere extension, breakup and the inception of.
Continental rifts and rifted margins rifts provide a unique window into the geodynamic system of our planet and the processes that shape the surface of the earth. Volcanic passive margins also are marked by numerous dykes and igneous intrusions within the subsided continental crust. In this context, the margin segment from the outer exmouth plateau to the gascoyne abyssal plain has been repeatedly studied as an example of volcanic margin. The newfoundlandiberia conjugate margins are among the beststudied magmapoor rifted margins in the world. We solve the equations of thermal convection for a nonnewtonian viscous fluid using an extended version of citcom3,18,19.
Pdf nonvolcanic rifted margins, continental breakup and the. Whitmarsh rb 2003 magmatism at the west iberia nonvolcanic rifted continental. Students will use geomapapp to create a topographic and bathymetric contour map, and to draw a bathymetric profile across the red sea. The presence or absence of thick mafic igneous sequences on the one hand and mantle serpentinites on the other may play a crucial role in the way rifted margins respond to convergence. Uniform lithospheric extension 1 predicts basic properties of nonvolcanic rifted margins but fails to explain other important characteristics 2,3. Froitzheim propagation of continental breakup in the southwestern south china sea p.
New models for evolution of magmapoor rifted margins based. Implications for volcanic rifted margins jeffrey a. The scs margin shows similarities to the hyperextended iberianewfoundland margins, possibly including exhumed and serpentinized mantle within the. Atlantic rifted margin crustal thickness and oct location from satellite gravity inversion incorporating a lithosphere thermal gravity anomaly correction. Mantle exhumation at nonvolcanic rifted margins due to melt suppression during continental breakup and seafloor spreading initiation european geosciences union, egu200, a04206 northern n.
Compared to nonvolcanic ones, volcanic passive margins mark continental breakup over a hotter mantle, probably subject to smallscale convection. Karson department of earth sciences syracuse university, syracuse ny 2441070 abstract rifting near hotspots results in mantle melting to create thick, mafic igneous crust at volcanic rifted margins vrms. Rifting, lithosphere breakup and volcanism franke 2012 1 rifting, lithosphere breakup and volcanism. The interpretation addresses the nature of the lower crust beneath nonvolcanic passive margins, the origin of ophicalcites, the probable time gap. Reston tj, morgan jp 2001 serpentinization and magmatism during extension at nonvolcanic margins. Crustal accretion of thick, mafic crust in iceland. Rifts and rifted margins worldwide show a large structural variety as a result of the interaction of rock rheology, tectonics, magmatism, deformation rates, inherited. Volcanic processes and deposits on rifted margins and in. They may form up to 30 per cent of passive margins around the world. Depthdependent extension, twostage breakup and cratonic.
Nonvolcanic rifted margins, continental breakup and the onset of. The bathymetry of rifted margins lab microsoft word 2007. Nonvolcanic rifted margins exhibit very little evidence of synrift magmatism, even where the continental crust has been thinned to such an extent that the mantle has been exhumed across a. Volcanic processes and deposits may have a strong impact on the structure and geodynamic development of continental margins and associated sedimentary basins. Many lips can be linked to regionalscale uplift, continental rifting and breakup, and climatic shifts. Rifted margins develop by the splitting apart of continents and form the trailing edges of ocean basins, to be incorporated into collision. Geological survey of denmark and greenland bulletin 24, 96 pp. New models for evolution of magmapoor rifted margins. While the iberia margin became the archetype of a nonvolcanic margin whitmarsh et al. Nonvolcanic passive margins nvpm constitute one end member of the transitional crustal. Fissiontrack dating has been applied to many volcanic rifted margins and, whereas young, hot volcanic rifted margins e. A comparison of evidence from land and sea, geological society special publication 187, geological society.
Noncontinental margins lack thick lavas that are generated as continental crust thins immediately prior to the onset of seafloor spreading. Reston tj, mcdermott kg, successive detachment faults and mantle unroofing at magmapoor rifted margins, geology. Expert petroleum geologists david roberts and albert bally bring you regional geology and tectonics. Menzies and others crust and upper mantle structure in east africa. South china sea rifted margin eco posted on october 12. Crustal structure of a nonvolcanic rifted margin east of.
Its key focus is on both volcanic and nonvolcanic passive margins, and the importance of salt and shale driven by sedimentary. Nature of the continentocean transition on the non. They present distinctive genetic and structural features. Crustal structure of the central nova scotia margin off. Wilson and others nonvolcanic rifted margins, continental breakup and the onset of seafloor spreading. Phanerozoic passive margins, cratonic basins and global tectonic maps, volume three in a threevolume series covering phanerozoic regional geology and tectonics. Volcanic passive margins vpm and nonvolcanic passive margins are the two forms of transitional crust that lie beneath passive continental margins that occur on earth as the result of the formation of ocean basins via continental rifting. Compared to nonvolcanic ones, volcanic passive margins mark continental. Consult the references below if you want the full story. Wilson and others non volcanic rifted margins, continental breakup and the onset of seafloor spreading. The identification of volcanic deposits and the evaluation of their impact on the margin history are thus two important aspects of the petroleum exploration on continental rifted margins. The case for depthdependent extension, earth and planetary science letters on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Bathymetry of rifted margins mini lesson collection 2014. Conjugate volcanic rifted margins, seafloor spreading, and.
The geological society of london nonvolcanic rifting of. These large igneous provinces lips are best preserved in the mesozoic and cenozoic where they occur as continental flood basalts, volcanic rifted margins, oceanic plateaus, and ocean basin flood basalts. Demonstrated, using a mesozoic analogue from the western australian margin, that volcanic rifted margins can survive in collisional orogens. Nonvolcanic continental margins may form up to 30% of all presentday passive margins, and remnants of them are preserved in mountain belts. Volcanic margins are characterized by seaward dipping reflections sdr in the basement and thick underplated igneous rocks in the lower part of the thinned continental crust and initial oceanic crust, such as the us east coast margins. Hazards related to earthquakes and volcanic eruptions in active rift zones are discussed along with submarine slope failures and landslide. The final rifting evolution at deep magmapoor passive margins from iberianewfoundland. Rifted continental margins typically are classified into two major categories, volcanic and non volcanic. Characteristics of volcanic rifted margins martin a.
Highrate extension of the lithosphere is associated with catastrophic mantle melting responsible for the accretion of a thick igneous crust. The formation of nonvolcanic rifted margins by the progressive. Comparison of magmapoor and volcanic rifted margins dieter franke abstract traditionally active rifts are thought to evolve in response to thermal upwelling of the. The compilation of circumantarctic margin characteristics indicates that only a quarter 3400 km of the rifted margins subduction to ridge collisions. The generation of volcanic continental margins and flood basalts robert white and dan mckenzie bullard laboratories, department of earth sciences, cambridge, enyland when continents rift to form new ocean basins, the riftingis sometimes accompanied by mas sive igneous activity. Two major types of passive margins are recognized, i. Gsa penrose conference report volcanic rifted margins. The papers in this volume demonstrate the benefits of integrating offshore and onshore studies, and illustrate the range of information obtained at different scales when comparing evidence from land and sea.
Thanks to improvements in offshore imaging and modeling techniques, rifted margins are not examined within an endmember classification volcanic nonvolcanic anymore, but in light of a gradual change in processes new observations new vocabulary. There are typically a lot of dykes formed perpendicular to the seawarddipping lava. At least 3 types of continental margin have now been recognised. Nonvolcanic rifted margin nonvolcanic margins are formed when extension is accompanied by little mantle melting and volcanism. The formation of nonvolcanic rifted margins by the. In order to understand what controls the transition from volcanic margins to nonvolcanic margins, the smart scotian margin transects refraction seismic experiment fig. Initiation of igneous processes associated with volcanic passive margins occurs before andor during the rifting process depending on the cause of rifting. Nonvolcanic margins such as the west iberian margin exhibit certain characteristics, such as a deficit of synrift igneous rock, a zone of exhumed subcontinental mantle in the continentocean transition and an apparent extension discrepancy. Conjugate volcanic rifted margins, seafloor spreading, and microcontinent. This book summarizes our present understanding of the formation of passive continental margins and their oceancontinent transitions. Sayers, j, symonds, pa, direen, ng and bernadel, g 2001, nature of the continentocean transition on the nonvolcanic rifted margin of the central great australian bight, in rcl wilson and rb whitmarsh and b taylor and n froitzheim eds. Part of the nato asi series book series asic, volume 463. Nonvolcanic margins such as the west iberian margin exhibit certain characteristics, such as a deficit of synrift igneous rock, a zone of exhumed. The formation of nonvolcanic rifted margins by the progressive extension of the lithosphere.
Special emphasis is placed on the structure and evolution of various atlantic margins. The interpretation addresses the nature of the lower crust beneath nonvolcanic passive margins, the origin of ophicalcites, the probable time gap between syn or postrift crystallization of. Volcanic rifted margins 2002, hardcover for sale online. Extension discrepancy at north atlantic nonvolcanic rifted margins. At the time of publication, this 600 ma east gondwana rifted margin segment was the oldest known rifted margin documented on the globe. Role of subaerial volcanic rocks and mantle plumes in. Volcanic and nonvolcanic rifted margins of the red sea and gulf of. The final rifting evolution at deep magmapoor passive. Because of the asymmetry, the continental margins on the two sides of an opening ocean may have very different profiles. This volume contains papers examining an active margin, fossil margins that border present day oceans, and remnants of margins exposed today in the alps. This expression of a transitional phase of extension, occurring before the onset of normal seafloor spreading and presumably above rising oceanic asthenosphere, may be a common feature on nonvolcanic rifted margins.
Characterization of sills associated with the u reflection. Students are asked to work in pairs with each partner creating hisher. A detailed seismic refraction study was undertaken of the rifted continental margin southeast of the grand banks of newfoundland, along a. Nonvolcanic transitional crust consists of stretched and thinned continental crust. New apatite fission track aft data from the southern red sea volcanic and the gulf of aden nonvolcanic margins provide important constraints on the timing of. Implications for the origin of cenozoic rifting and volcanism and the formation of magmatic rifted margins authors andrew a. Volcanic passive margins represent one endmember transitional crust type, the other endmember amagmatic type is the rifted passive margin.
Proceedings of the nato advanced research workshop, mallorca, spain, 1114 may 1994 rifted oceancontinent boundaries covers a wide range of topics, from quantitative modelling to current knowledge of the structure and evolution of specific margins around the world. Nyblade development of the lebombo rifted volcanic margin of southeast africa m. Nonvolcanic rifted margins, continental breakup and the onset of seafloor spreading. Australias western continental margin formed during gondwana breakup between australia antarctica and india, leaving behind an evolving plate boundary with significant new magmatic crust accreted to the continental fragments. Here i show that at those nonvolcanic margins where the velocity structure is well known, the upper and lower crust appear to thin equally toward.
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