Plate tectonics and island arcs

1990 ◽  
pp. 113-138
Author(s):  
WARREN B. HAMILTON
Keyword(s):  
Plate Tectonics ◽  
Island Arcs

scholarly journals Archaean Plate Tectonics in the North Atlantic Craton of West Greenland Revealed by Well-Exposed Horizontal Crustal Tectonics, Island Arcs and Tonalite-Trondhjemite-Granodiorite Complexes

2020 ◽  
Vol 8 ◽  
Author(s):  
Adam Andreas Garde ◽  
Brian Frederick Windley ◽  
Thomas Find Kokfelt ◽  
Nynke Keulen
Keyword(s):  
North Atlantic ◽  
Plate Tectonics ◽  
Plate Tectonic ◽  
Island Arcs ◽  
West Greenland ◽  
Structural Style ◽  
Modern Style ◽  
Greenstone Belts ◽  
Lower Crustal ◽  
North Atlantic Craton

The 700 km-long North Atlantic Craton (NAC) in West Greenland is arguably the best exposed and most continuous section of Eo-to Neoarchaean crust on Earth. This allows a close and essential correlation between geochemical and isotopic data and primary, well-defined and well-studied geological relationships. The NAC is therefore an excellent and unsurpassed stage for the ongoing controversial discussion about uniformitarian versus non-uniformitarian crustal evolution in the Archaean. The latest research on the geochemistry, structural style, and Hf isotope geochemistry of tonalite-trondhjemite-granodiorite (TTG) complexes and their intercalated mafic to intermediate volcanic belts strongly supports previous conclusions that the NAC formed by modern-style plate tectonic processes with slab melting of wet basaltic oceanic crust in island arcs and active continental margins. New studies of the lateral tectonic convergence and collision between juvenile belts in the NAC corroborate this interpretation. Nevertheless, it has repeatedly been hypothesised that the Earth’s crust did not develop by modern-style, subhorizontal plate tectonics before 3.0 Ga, but by vertical processes such as crustal sinking and sagduction, and granitic diapirism with associated dome-and-keel structures. Many of these models are based on supposed inverted crustal density relations, with upper Archaean crust dominated by heavy mafic ridge-lavas and island arcs, and lower Archaean crust mostly consisting of felsic, supposedly buoyant TTGs. Some of them stem from older investigations of upper-crustal Archaean greenstone belts particularly in the Dharwar craton, the Slave and Superior provinces and the Barberton belt. These interpreted interactions between these upper and lower crustal rocks are based on the apparent down-dragged greenstone belts that wrap around diapiric granites. However, in the lower crustal section of the NAC, there is no evidence of any low-density granitic diapirs or heavy, downsagged or sagducted greenstone belts. Instead, the NAC contains well-exposed belts of upper crustal, arc-dominant greenstone belts imbricated and intercalated by well-defined thrusts with the protoliths of the now high-grade TTG gneisses, followed by crustal shortening mainly by folding. This shows us that the upper and lower Archaean crustal components did not interact by vertical diapirism, but by subhorizontal inter-thrusting and folding in an ambient, mainly convergent plate tectonic regime.

Plate Tectonics Now and in the Past

2004 ◽  
Author(s):  
John J. W. Rogers ◽  
M. Santosh
Keyword(s):  
Plate Tectonics ◽  
Oceanic Lithosphere ◽  
Continental Margins ◽  
Island Arcs ◽  
Low Velocity ◽  
S Waves ◽  
Ocean Ridges ◽  
1960S And 1970S ◽  
Tectonic Contact ◽  
The 1960S

The concepts known as plate tectonics that began to develop in the 1960s built on a foundation of information that included: • The earth’s mantle is rigid enough to transmit seismic P and S waves, but it is mobile to long-term stresses. • The earth’s temperature gradient is so high that convective overturn must occur in the mantle. • The top of the mobile part of the mantle is a zone of relatively low velocity at depths of about 100 to 200 km. This zone separates an underlying asthenosphere from a rigid lithosphere, which includes rigid upper mantle and crust. • Seismic activity, commonly accompanied by volcanism, occurs along narrow, relatively linear, zones in oceans and along some continental margins. • The zones of instability surround large areas of comparative stability. • Ocean lithosphere is continually generated along mid-ocean ridges and destroyed where it descends under the margins of continents and island arcs. This causes oceans to become larger, but shrinkage of oceans can occur where lithosphere is destroyed around ocean margins faster than it is formed within the basin. • Some of the belts of instability are faults with lateral offsets of hundreds of kilometers. • Some continental margins are unstable (Pacific type), but others are attached to oceanic lithosphere without any apparent tectonic contact (Atlantic type). • Different areas containing continents and attached oceanic lithosphere move around the earth independently of each other. Most of this chapter consists of a summary of plate tectonics in the present earth, including processes along plate margins and the types of rocks formed there (readers who want more detailed information are referred to Rogers, 1993a; Kearey, 1996; and Condie, 1999). We also briefly discuss plumes and then finish with a word of caution about interpreting the history of the ancient and hotter earth with the principles of modern plate tectonics. Starting from the body of continually expanding information summarized above, numerous earth scientists in the 1960s and 1970s began to establish a conceptual framework that would organize scientific thinking about the earth’s tectonic processes. This required a new terminology, and it arrived rapidly (Oreskes, 2002). Geologists decided to call the stable areas “plates” and the unstable zones around them “plate margins.” Thus, the concept became known as “plate tectonics.” Plates are essentially broad regions of lithosphere, although the failure to detect low-velocity zones under many continents leaves unresolved questions.

Plate Tectonics

2021 ◽  
pp. 114-136
Author(s):  
Elisabeth Ervin-Blankenheim
Keyword(s):  
Plate Tectonics ◽  
Plastic Material ◽  
Convergent Margins ◽  
Island Arcs ◽  
Mountain Ranges ◽  
Ocean Ridges ◽  
Rock Types ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Many

Plate tectonics, the grand unifying theory of geology, and its relation to the Earth is explained in this chapter. The planet transforms through time by means of the movement of rigid plates carrying the continents riding on the plastic material in the Earth’s upper mantle. Three major plate boundaries are divergent margins, where new ocean floor is being created along mid-ocean ridges and plates separate from one another; convergent margins, where the material is subducted and consumed as different types of plates collide, creating trenches, island arcs or mountain ranges, and transform boundaries; and where plates slide past one another. Besides the three predominant boundaries, hot spots caused by mantle plumes and diffuse boundaries make up additional dynamic forces in tectonics. Beyond these categories, geologists still are learning about tectonics; some boundaries are unknown or speculative. Plate tectonics explains why many of the Earth’s hazards are found where there are. Earthquakes trace many plate margins, as do volcanoes. The area around the Pacific Ocean is called the “Ring of Fire” because of the many volcanoes related to subducting plates. Tectonics accounts for why certain rocks are located where they are; for example, all rock types are found at convergent margins. The theory also predicts where valuable mineral and economic deposits are located.

Plate tectonics through geological time

1981 ◽  
Vol 301 (1461) ◽  
pp. 207-215 ◽  
Keyword(s):  
Plate Tectonics ◽  
Space Distribution ◽  
Island Arcs ◽  
Geological Time ◽  
Polar Wander ◽  
Crustal Rocks ◽  
Geological Processes ◽  
Time Space ◽  
Progressive Growth ◽  
Metamorphic Terranes

Geological processes controlled by plate tectonics govern the time-space distribution of key rock assemblages. Stratal components of geosynclinal prisms, igneous provinces of orogenic belts, and regional facies of metamorphic terranes all display patterns controlled by inferred plate motions. Similarities between most Precambrian rock assemblages and Phanerozoic counterparts, coupled with analogies between Precambrian and Phanerozoic apparent polar wander paths, suggest that most surviving crustal rocks of all ages owe their origins to plate-tectonic processes. Archaean crustal blocks resemble collages of oceanic island arcs and volcanic archipelagoes whose tectonic juxtaposition to form cratonic nuclei was probably accomplished by subduction and crustal collision. Thereafter, similar Proterozoic oceanic elements were gradually accreted to growing continental margins and eventually crushed between colliding continental blocks of progressively larger size. Meanwhile, Archaean terranes within the interiors of cratons were generally shielded from further deformation, with their oceanic aspects largely preserved. In time, Phanerozoic oceanic terranes will systematically be destroyed by subduction or modified by incorporation into consolidated continental blocks. Differences between Precambrian and Phanerozoic plate tectonics and related assemblages reflect secular decline in global heat flux of radiogenic origin and progressive growth in the dimensions of cratonic blocks of continental crust.

Southeastern Atlantic Canada, Northwestern Africa, and Continental Drift

1971 ◽  
Vol 8 (10) ◽  
pp. 1218-1251 ◽  
Author(s):  
Paul E. Schenk
Keyword(s):  
North Atlantic ◽  
Plate Tectonics ◽  
Continental Drift ◽  
Continental Collision ◽  
Atlantic Canada ◽  
Island Arcs ◽  
Late Precambrian ◽  
The North ◽  
Northwestern Africa ◽  
Southeastern Atlantic

The model applies plate-tectonics to explain the geologic evolution of southeastern Atlantic Canada and northwestern Africa. The North Atlantic may have opened and closed several times from the middle Cryptozoic to the present. Closings of the ocean caused collisions between continents and also island arcs. Openings were ragged so that parts of one continent were transposed to the other, and sialic fragments became offshore micro-continents. Africa has progressively lost increments of continental crust to North America.Precambrian blocks of southeastern Atlantic Canada may be remnants of an African shelf. which was crumpled during a billion-year old continental collision (Grenville orogeny). After ragged rifting during the Late Precambrian these fragmentary blocks were carried eastward as micro-continents off Africa. Both early (Danakil Alps of the Red Sea) and late-stage (Canary Islands) recent analogues appear valid. The micro-continents ponded turbidites, which formed rise-complexes off Africa. Continental glaciations in the Late Precambrian and Late Ordovician not only make excellent inter-regional chronostratigraphic units in almost unfossiliferous strata. but also may confirm the African origin of Nova Scotia. Subducting plate-margins increased offshore volcanism and narrowed the Paleozoic Atlantic. Late Paleozoic continental collision again between Africa and North America sandwiched the micro-continent, telescoped the sedimentary/volcanic complexes, and flooded the sutured area with granodiorite. Middle Carboniferous carbonates and sulfates record vestiges of the Paleozoic Atlantic, and mixing of the Euro-African fauna with that of the western Paleozoic Atlantic of the northwestern Appalachians. The Atlantic was closed at least along the latitude of Atlantic Canada and Morocco. During the Mesozoic, an accreting margin uplifted this area, quickened redbed deposition and volcanism, initiated restricted marine sedimentation, and inaugurated the present North Atlantic east of the African remnant of southeastern Atlantic Canada.

Volcanism and plate tectonics in the Indonesian island arcs

1975 ◽  
Vol 26 (3-4) ◽  
pp. 165-188 ◽  
Author(s):  
John A. Katili
Keyword(s):  
Plate Tectonics ◽  
Island Arcs

scholarly journals Titanium isotopes as a tracer for the plume or island arc affinity of felsic rocks

2019 ◽  
Vol 116 (4) ◽  
pp. 1132-1135 ◽  
Author(s):  
Zhengbin Deng ◽  
Marc Chaussidon ◽  
Paul Savage ◽  
François Robert ◽  
Raphaël Pik ◽  
...  
Keyword(s):  
Continental Crust ◽  
Plate Tectonics ◽  
Indirect Evidence ◽  
Island Arc ◽  
Island Arcs ◽  
Calc Alkaline ◽  
Magma Differentiation ◽  
Isotopic Signatures ◽  
Crustal Rocks ◽  
Felsic Rocks

Indirect evidence for the presence of a felsic continental crust, such as the elevated 49Ti/47Ti ratios in Archean shales, has been used to argue for ongoing subduction at that time and therefore plate tectonics. However, rocks of intermediate to felsic compositions can be produced in both plume and island arc settings. The fact that Ti behaves differently during magma differentiation in these two geological settings might result in contrasting isotopic signatures. Here, we demonstrate that, at a given SiO2 content, evolved plume rocks (tholeiitic) are more isotopically fractionated in Ti than differentiated island arc rocks (mainly calc-alkaline). We also show that the erosion of crustal rocks from whether plumes (mafic in average) or island arcs (intermediate in average) can all produce sediments having quite constant 49Ti/47Ti ratios being 0.1–0.3 per mille heavier than that of the mantle. This suggests that Ti isotopes are not a direct tracer for the SiO2 contents of crustal rocks. Ti isotopes in crustal sediments are still a potential proxy to identify the geodynamical settings for the formation of the crust but only if combined with additional SiO2 information.

On crustal plates

1975 ◽  
Vol 65 (5) ◽  
pp. 1495-1500
Author(s):  
Don Tocher
Keyword(s):  
Plate Tectonics ◽  
Seismic Waves ◽  
Continental Drift ◽  
Active Regions ◽  
Continental Margins ◽  
Island Arcs ◽  
Low Velocity ◽  
Transform Faults ◽  
Sea Floor Spreading ◽  
Velocity Layer

Abstract During the decade just past, developments in Seismology have played an active and central role in the development of the concept of Plate Tectonics. Observational Seismology has provided support for and verification of a number of the dynamic aspects of the hypotheses of continental drift, sea-floor spreading, transform faults and the underthrusting of the lithosphere at island arcs and some continental margins. Those types of seismological evidence which bear on the question of the thickness of the lithosphere are either indirect or circumstantial, or both. As early as 1926, Gutenberg postulated the existence of a layer at a depth of 80 to 150 or 200 km, probably worldwide in extent, in which the velocities of seismic waves are slightly lower than in the immediately overlying layers. Some plate tectonics workers equate this low-velocity layer to the relatively-weak asthenosphere required by Plate Tectonics to underlie the stronger, more brittle lithosphere. In this review, several lines of evidence are marshalled in support of a plate model of the continental crust in seismically active regions in which a layer of decoupling of an upper, lithospheric layer from the weaker substrate may lie in the crust itself at a depth of perhaps 10 to 15 km.

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