Geodetic and geophysical evidence for magma movement and dyke injection during the Krafla rifting episode in north Iceland

1989 ◽  
pp. 65-77 ◽  
Author(s):  
Wolfgang R. Jocoby ◽  
Hannsjörg Zdarsky ◽  
Uta Altmann
Keyword(s):  
Dyke Injection

Evidence of crustal drift from Icelandic geology

1965 ◽  
Vol 258 (1088) ◽  
pp. 199-204 ◽  
Keyword(s):  
Cross Section ◽  
Continental Drift ◽  
The Other ◽  
Oceanic Ridge ◽  
Dyke Injection ◽  
Made In

Iceland, the only substantial landmass astride a mid-oceanic ridge, supplies details of how the necessary dilation for continental drift could be accomplished. Two types of approach have been made. In one, the visible dilation—evidenced by gaping cracks and volcanic fissure eruptions—in the active volcanic zones crossing Iceland has been measured. It amounts to about 30 m in the last 3000 to 5000 yr. In the other, the dykes—dilation fissures infilled with once-fluid basalt— which fed the Tertiary lavas of the older parts of Iceland have been measured. It is found that a prism of basalt lavas with a cross-section of 80 km2 requires 3 to 6 km in thickness of dyke feeders. Extending these figures, for a prism of lavas 10 km thick with the present width of Iceland, a dilation of 200 to 400 km of dyke feeders is necessitated. While a dilation of this order is much less than the amount needed to separate America from Europe, it at least shows how substantial amounts of dilation could be achieved by dyke injection.

scholarly journals The propagation and seismicity of dyke injection, new experimental evidence

2016 ◽  
Vol 43 (5) ◽  
pp. 1876-1883 ◽  
Author(s):  
Richard R. Bakker ◽  
Marco Fazio ◽  
Philip M. Benson ◽  
Kai-Uwe Hess ◽  
Donald B. Dingwell
Keyword(s):  
Experimental Evidence ◽  
Dyke Injection

scholarly journals First direct age determinationfor the Kelseaa Dolerite Dyke, Bornholm, Denmark

2005 ◽  
Vol 52 ◽  
pp. 1-6 ◽  
Author(s):  
Paul M. Holm ◽  
L.E. Pedersen ◽  
L.M. Heaman
Keyword(s):  
Baltic Shield ◽  
Geochronological Data ◽  
Mafic Dykes ◽  
Dolerite Dyke ◽  
Southwestern Margin ◽  
Dyke Injection ◽  
The Baltic

The Danish island Bornholm on the southwestern margin of the Baltic Shield was subject to dyke injection during the Proterozoic. The dykes probably result from several magmatic events. We present U-Pb geochronological data for the largest of the dykes, the tholeiitic Kelseaa dyke. The resulting age, 1326 ±10 (2σ) Ma, places the dyke significantly earlier in the Proterozoic than previously assumed. No other dykes of this age have been reported from the western part of the Baltic Shield. The NE–SW strike of the Kelseaa dyke is evidence for extension oblique to the border of the Baltic Shield.The Kelseaa dyke is the first evidence for this event that was subsequent to the emplacement of theBornholm and Karlshamn (SE Sweden) granites and prior to the intrusion of the Central Scandinavian Dolerite Group, and possibly also the majority of mafic dykes on Bornholm.

scholarly journals Potassium-argon ages from Phanerozoic basic dykes in South-East Greenland

1978 ◽  
Vol 90 ◽  
pp. 141-146
Author(s):  
J.G Mitchell
Keyword(s):  
North Atlantic ◽  
East Coast ◽  
Dyke Swarm ◽  
The South ◽  
East Greenland ◽  
Break Up ◽  
Dyke Injection ◽  
General Period

Nine basaltic dykes were sampled by coring during geological reconnaissance of the south-east coast of Greenland (Bridgwater et al., 1977) between Angmagssalik (65°40') and Nordfjord (fig. 49). The samples were initially collected for palaeomagnetic investigations (Beckmann,1977). In the field it was assumed that all the fresh basic dykes in the region were Tertiary in age and represented a southern continuation of the coastal dyke swarm described by Wager & Deer (1938). The timing of dyke injection is very important as a possibie indication of the initial break-up of the original North Atlantic mass. Furthermore, it was assumed that the major coast-parallel dyke swarm (for example site 26 & 28, see fig. 49) was the continuation of the more intense Tertiary dyke swarm reported by Wager & Deer (1938) further north, while the more sporadic dykes with other trends were presumed also to belong to the same general period of injection. The preliminary palaeomagnetic studies by Beckmann (1977) showed no consistent differences between dykes grouped according to their trends.

Mobilization of fluidized sediment during sill emplacement, western Dronning Maud Land, East Antarctica

2003 ◽  
Vol 15 (3) ◽  
pp. 393-398 ◽  
Author(s):  
MICHAEL L. CURTIS ◽  
TEAL R. RILEY
Keyword(s):  
East Antarctica ◽  
Show Evidence ◽  
Dronning Maud Land ◽  
Flame Structures ◽  
Dyke Injection ◽  
Clastic Sedimentary ◽  
Physical Features

Large mafic sills in the Ahlmannryggen region of western Dronning Maud Land were intruded into partially lithified sediments of the mid-Proterozoic Ritscherflya Supergroup. Clastic sedimentary dykes intruding the thick mafic sills have been identified, and show evidence for fluidization of the partially lithified sediments. Previous work had demonstrated in situ fluidization and localized anatectic melting. This study demonstrates mobilization of the fluidized sediments, with penetration at least 50 m into the fractured, intruding sill. Physical features within the clastic dykes (e.g. sediment balls, flame structures) suggest that the sediments were largely unconsolidated, or at most only partially lithified. The presence of a thin zone of anatectic melt along the dyke—sill contact suggests that the mafic sill was still hot (c. 700°C) at the time of sedimentary dyke injection.

Mechanism of emplacement and crystallisation history of the northern margin and centre of the Galway Granite, western Ireland

2006 ◽  
Vol 97 (1) ◽  
pp. 1-23 ◽  
Author(s):  
Bernard Elgey Leake
Keyword(s):  
Country Rock ◽  
Late Phase ◽  
Main Phase ◽  
Mixing Zone ◽  
Northern Margin ◽  
Fractionation Scheme ◽  
History Of ◽  
Magma Pulses ◽  
Dyke Injection ◽  
Western Ireland

ABSTRACTThe main phase (∼400 Ma) emplacement of the central and northern part of the reversely zoned Galway Granite was incremental by progressive northward marginal dyke injection and stoping of the 470–467 Ma Connemara metagabbro-gneiss country rock. The space was provided by the synchronous ESE-opening, along the strike of the country rocks, of extensional fractures generated successively northward by a releasing bend in the sinistrally moving Skird Rocks Fault or an equivalent Galway Bay Fault. This fault is a prolongation of the Antrim–Galway (a splay off the Highland Boundary Fault) and Southern Upland Faults. The ESE-strike of the spalled-off rocks controlled the resultant ESE-elongated shape of the batholith. The magma pulses (∼5–30 m in thickness) were progressively more fractionated towards the northern margin so that the coarse Porphyritic (or Megacrystic) Granite (GP; technically granodiorite) in the centre was followed outwards by finer grained, drier and more siliceous granite, until the movements opening the fractures ceased and the magma became too viscous to intrude. ‘Out-of-sequence’ pulses of more basic diorite-granodiorite (including the Mingling–Mixing Zone) and late main phase, more acid, coarse but Aphyric Granite, into the centre of the batholith, complicated the outward fractionation scheme. The outward expansion, caused by the intrusions into the centre, caused a foliation and flattening of cognate xenoliths within the partly crystallised northern marginal granite and in the Mingling–Mixing Zone to the south.Late phase (∼380 Ma) central intrusions of the newly-discovered aphyric Shannapheasteen Finegrained Granite (technically granodiorite), the Knock, the Lurgan and the Costello Murvey Granites, all more siliceous and less dense than the GP, were emplaced by pushing up the already solid and jointed GP along marginal faults. This concentration of lighter granites plus compression shown in thrusting, caused overall fault uplift of the Central Block of the Galway batholith so that the originally deepest part of the GP is exposed where there is the most late phase granite. Chemical analyses show the main and late phase magmas, including late dykes, were very similar, with repetition of the same fractionation except that the late phase magmas were drier and more quickly cooled, giving finer grained rocks.

scholarly journals Mapping and evaluating kinematics and stress/strain field at active faults and fissures: a comparison between field and drone data at NE Rift, Mt Etna (Italy)

2021 ◽  
Author(s):  
Alessandro Tibaldi ◽  
Noemi Corti ◽  
Emanuela De Beni ◽  
Fabio Luca Bonali ◽  
Susanna Falsaperla ◽  
...  
Keyword(s):  
Stress Field ◽  
Best Practice ◽  
Ground Deformation ◽  
Active Faults ◽  
Normal Faults ◽  
Extension Rate ◽  
North East ◽  
The North ◽  
Mt Etna ◽  
Dyke Injection

Abstract. We collected drone data to quantify the kinematics at extensional fractures and normal faults, integrated this information with seismological data to reconstruct the stress field, and critically compared the results with previous fieldwork to assess the best practice. As key site, we analysed a sector of the North-East Rift of Mt Etna, an area affected by continuous ground deformation linked to gravity sliding of the volcano's eastern flank and dyke injection. The studied sector is characterized also by the existence of eruptive craters and fissures and lava flows. This work shows that this rift segment is affected by a series of NE-striking, parallel extensional fractures characterized by an opening mode along an average N105.7° vector. Normal faults strike parallel to the extensional fractures, although they tend to bend slightly when crossing topographic highs corresponding to pyroclastic cones. The extensional strain obtained by cumulating the net offset at extensional fractures with the fault heave gives a stretching ratio of 1.003 in the northeastern part of the study area and 1.005 in the southwestern part. Given a maximum age of 1614 yr AD for the offset lavas, we obtained an extension rate of 1.9 cm/yr for the last 406 yr. The stress field is characterised by a σHmin trending NW-SE. Results indicate that Structure-from-Motion photogrammetry applied to drone surveys allows to collect large amounts of data with a resolution of 2–3 cm, a detail comparable to field surveys. In the same amount of time, drone survey can allow to collect more data than classical fieldwork, especially in logistically difficult rough terrains.

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