Specifics of the Caledonian Collision in the Ol’khon Region (Lake Baikal, Russia)

2021 ◽  
Vol 62 (4) ◽  
pp. 389-400
Author(s):  
V.A. Makrygina
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
Lake Baikal ◽  
Siberian Craton ◽  
Island Arc ◽  
Geophysical Data ◽  
Igneous Rocks ◽  
Fold Belt ◽  
Adjacent Part

Abstract —Analysis of geochemical, geochronological, and new geophysical data on metasedimentary and igneous rocks of the Ol’khon region has made it possible to substantiate: (1) the absence of products of the Caledonian suprasubduction magmatism from the adjacent part of the Siberian craton and (2) the presence of a product of this magmatism in the Anga–Talanchan island arc, namely, the Krestovsky massif with gabbro-diorite to granite phases. This suggests subduction of the Paleoasian oceanic crust under the island arc before the collision. The geophysical data showed a steep sinking of the Siberian craton margin. This sinking and the supposed contrary movement and rotation of the Siberian craton prevented the appearance of a subduction zone beneath the craton during the collision but caused the wide development of fault plates in the fold belt at the late collision stage. The residue of oceanic crust slab was pressed out along the fault planes near the surface and formed a row of gabbro-pyroxenite massifs of the Birkhin Complex in the fold belt, where syncollisional granitic melts (Sharanur Complex) formed at the same time. The interaction of two contrasting melts gave rise to the Tazheran and Budun alkaline syenite massifs and alkaline metasomatites of the Birkhin and Ulanganta gabbroid massifs.

Trace elements and tectonic relationships of basaltic rocks in the Ballantrae igneous complex, Ayrshire

1974 ◽  
Vol 111 (1) ◽  
pp. 35-41 ◽  
Author(s):  
J. M. Wilkinson ◽  
J. R. Cann
Keyword(s):  
Trace Elements ◽  
Subduction Zone ◽  
Oceanic Crust ◽  
Hot Spot ◽  
Island Arc ◽  
Igneous Complex ◽  
Basaltic Rocks ◽  
Genetic Groups ◽  
Tectonic Environment ◽  
Low Potassium

SummaryIn order to obtain further evidence for the tectonic environment of generation of the basaltic rocks of the Ballantrae igneous complex, specimens of pillow lavas, dolerites, glaucophane schists and amphibolites were analysed for Ti, Zr, Y and Nb. Using Ti–Zr–Y, Ti–Zr and Y/Nb diagrams, three different genetic groups have been distinguished – (i) hot-spot basalts round Downan Point, round Bennane Head as far N as Balcreuchan Port, and also within serpentinite around Lendalfoot, (ii) island arc low-potassium tholeiites between Balcreuchan Port and Gamesloup, and (iii) possible ocean floor basalts at Knockormal and Knocklaugh. The interrelationships of these groups are in doubt. The hot-spot basalts may have been erupted through oceanic crust, but they could have formed prior to, or subsequent to, the island arc activity. More likely, the hot-spot basalts formed (possibly on oceanic crust) at a considerable distance from the island arc, and the two were later brought together tectonically, probably at the subduction zone associated with the arc.

Geochemistry of the upper Snooks Arm Group basalts, Burlington Peninsula, Newfoundland: evidence against formation in an island arc

1980 ◽  
Vol 17 (7) ◽  
pp. 888-900 ◽  
Author(s):  
G. A. Jenner ◽  
B. J. Fryer
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
Sedimentary Rocks ◽  
Oceanic Islands ◽  
Oceanic Island ◽  
Island Arc ◽  
Geochemical Data ◽  
Basaltic Rocks ◽  
Arc Setting ◽  
Back Arc

The Snooks Arm Group of the Newfoundland Appalachians, which includes the Betts Cove ophiolite at its base, has been interpreted as oceanic crust overlain by island arc volcanic and sedimentary rocks. The limited geochemical data available on the upper Snooks Arm Group basalts have been used as evidence for and against their formation in an island arc environment.Reinvestigation of the chemistry of the basaltic rocks of the upper Snooks Arm Group establishes them as large ion lithophile enriched tholeiites. Similar basalts have been found in oceanic islands, on aseismic ridges, and possibly in back-arc basins. Chemically analogous rocks are notably lacking from island arc settings.The geochemistry and geology of the upper Snooks Arm Group suggest that these rocks may have formed in either an oceanic island setting or, as recently suggested by Upadhyay and Neale, as part of a marginal basin. It is not possible to distinguish between these alternate models, although the most similar basaltic rocks occur in the former environment. It is most unlikely that these rocks formed in an early island arc setting and indeed there may be no need for them to be associated with a major subduction zone.

STRUCTURE OF ISLAND ARCS BOUNDING THE AUSTRALIAN CONTINENTAL PLATE

1972 ◽  
Vol 12 (2) ◽  
pp. 74
Author(s):  
P.G. Temple
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
New Caledonia ◽  
Island Arc ◽  
Island Arcs ◽  
North East ◽  
Continental Plate ◽  
Sequence Of Events ◽  
Australian Plate ◽  
Northern Edge

The New Global Tectonic theory is proving exceedingly valuable to understanding the geological history of large parts of the world's surface. However, in island arc areas, such as those bounding the Australian Continental Plate, the theory is meeting with certain difficulties. These might be due to (a) the theory itself not being valid here, or (b) it needs modification.Certain spectacular aspects of the geology of Timor, New Guinea, New Caledonia and Northland New Zealand suggest that a good case could be made for modification. Large areas of each of these islands are covered by thick chaotic masses of layered ultrabasic igneous rock, radiolarian chert, shale and other sediments of a pelagic nature normally associated with oceanic regimes. Moreover, this sequence of rocks appears to have been tectonically emplaced from an oceanward direction on to sediments of a continental shelf environment. Emplacement seems to have occurred at approximately the same time and to have involved rocks of approximately the same age in all areas.A logical way to account for the observations above in terms of the New Global Tectonic theory is as follows:In Late Cretaceous to Early Tertiary time the northern and eastern edge of the Australian continental plate was dragged down and began to underthrust the oceanic mantle along a north to north-east dipping subduction zone (the Tethian subduction zone, which is still active along the western edge of the Indonesian Arc).From Early to Middle Tertiary time, light continental crust could no longer be subducted under heavier mantle and subduction ceased. Isostatic re-adjustment occurred, raising the northern edge of the Australian plate which still carried large remnants of oceanic crust that had been emplaced above it.At about the same time, and continuing to the present, a new pattern of south to east dipping subduction formed. Edges of the Australian plate were torn away and migrated eastward, leaving areas of new oceanic crust behind.If the sequence of events above is essentially a true picture, it leads not only to some interesting modifications of the New Global Tectonic theory, but also to certain implications as to mineral and petroleum prospects within island arc areas.

Tectonic structure and evolution of the southern part of the Central sector of the Indian ocean

2020 ◽  
pp. 3-11
Author(s):  
E. P. Dubinin ◽  
A. V. Kokhan ◽  
G. L. Leitchenkov ◽  
A. A. Shaikhullina
Keyword(s):  
Indian Ocean ◽  
Oceanic Crust ◽  
Geophysical Data ◽  
Digital Models ◽  
Tectonic Structure ◽  
Ocean Study ◽  
The Indian Ocean

The article is dedicated to review of structural and evolutionary peculiarities of the southern part of central sector of the Indian ocean. Study is based on analyses of global digital models, distribution of fractures, global and regional lithosphere evolution models and published geological and geophysical data. As a result of study, tectonic regionalization of oceanic crust of the area is presented and main evolution stages of the region are distinguished.

Sign in / Sign up

Export Citation Format

Share Document