Plate Tectonic Evolution Research Articles

Hypothesis on the plate tectonic evolution of the Carpatho-Balkan arcs

We propose a plate-tectonic model for evolution of the Dinaric-Carpathian and Hellenic-Balkan systems since the Upper Jurassic/Lower Cretaceous. Initially, an oceanic area lying between the African and European continents was being consumed in north-dipping subduction zones situated close to the European margin. This process gave rise to Lower Cretaceous calc-alkaline magmatism occurring in the Vardar zone, and to Upper Cretaceous/Lower Eocene calc-alkaline and K-alkaline magmatism (Banatitic igneous activity) of the Apuseni-Timok-Srednogora alignment. A back-arc thrust belt (in the meaning of Dickinson) developed behind the Hellenic-Balkan system, while a marginal basin was opened up behind the Dinaric-Carpathian system. In Lower Miocene times an important evolutionary change reversed the subduction polarity in the Dinaric-Carpathian system, causing the closure of the previous marginal basin, and the formation of the Neogene Carpathian arc and the Pannonian and Transylvanian ensialic marginal basins; in the Hellenic-Balkan system, a southward migration of the arc-trench system occurred. This change was almost contemporaneous with complex changes in the western Mediterranean and with the re-arrangement of plate movements in Atlantic, Pacific and Indian areas.

A Discussion on volcanism and the structure of the Earth - Cenozoic volcanism and plate-tectonic evolution of the Western United States. I. Early and middle cenozoic

Variations in Cenozoic volcanism in the Western United States correlate rather closely with changes in tectonic setting: intermediate-composition rocks and their associated differentiates were erupted through orogenic or fairly stable crust, whereas basaltic or bimodal basalt-rhyolite suites were erupted later— concurrently with crustal extension and normal faulting. Lower and middle Cenozoic continental lavas, erupted onto postorogenic terranes, are predominantly intermediate types (andesite to rhyodacite), commonly with closely associated more silicic ashflow sheets. Compositional zonations in individual ash-flow sheets, from rhyolite upward into quartz latite, record magmatic differentiation in underlying batholithic source chambers. The intermediate lavas probably represent the greater part of these batholiths and the ash-flow tuffs their differentiated tops. Continental volcanic activity of this type was most voluminous in the northwestern United States in Eocene time, but shifted southward in the Oligocene; contemporaneous sea-floor basalts occur in the Oregon-Washington coast ranges. Largely intermediate-composition calc-alkalic igneous suites, that become more alkalic toward the continental interior, are characteristic of most of the North and South American cordilleran belt. Similar volcanic associations are forming now around most of the Pacific margin where continental plates override oceanic crust along active subduction systems, marked by Benioff seismic zones and oceanic trenches. A similar subduction mechanism probably operated in the Western United States until late Cenozoic time. Analogy with chemical variations across active island arcs suggest that early and middle Cenozoic subduction occurred along two subparallel imbricate zones that dipped about 20° eastward. The western zone emerged at the continental margin, but the eastern zone was entirely beneath the continental plate, partly coupled to the western zone below the low-velocity layer. Predominantly intermediate-composition volcanism persisted throughout the Western United States until the initial intersection of North America with the East Pacific rise started the progressive destruction of the subduction system

A Discussion on volcanism and the structure of the Earth - Cenozoic volcanism and plate-tectonic evolution of the Western United States. II. Late cenozoic

A major change in volcanic associations and their tectonic settings occurred in much of the Western United States during late Cenozoic time. Where this volcano-tectonic transition can be documented, an earlier orogenic and post-orogenic association of predominantly calc-alkalic andesitic rocks typical of circum-Pacific continental margin and island arcs was succeeded by fundamentally basaltic volcamsm which accompanied regional normal and strike-slip faulting. The igneous fields regarded here as fundamentally basaltic include: (1) basaltic fields, (2) alkalic fields in which differentiated igneous series commonly can be related to alkali-basaltic parent magmas, and (3) bimodal associations of mafic and silicic rocks, generally basalts and high-silica rhyolites. Similar igneous fields occur in other regions of the world characterized by tectonic extension. The nature and timing of the late Genozoic volcano-tectonic transition in various areas of the Western United States are documented from published references. The transition began in the southeastern part of the region in latest Oligocene time and moved northwestward through Miocene, Pliocene, and Quaternary time. The inception of basaltic, alkalic, or bimodal volcanism and associated regional extension of inland areas appears to date the times at which plate-tectonic boundaries between North America and two Pacific plates underwent drastic changes. These changes resulted from collision of the East Pacific Rise with a mid-Tertiary continental-margin trench and resulting direct contact of the American and western Pacific plates along a right-lateral transform fault system. These platetectonic interactions have evolved continuously and have determined the volcanic and tectonic evolution of the Western United States for the last 30 million years.

Evolution of the Cordilleran Fold Belt

The geotectonic development of the Cordilleran fold belt in western North America during Phanerozoic time took place in three principal phases: (I) an initial orthogeosynclinal phase, (II) an orogenic–late geosynclinal phase, and (III) an orogenic-postgeosynclinal phase. These phases developed over a span of more than 500 m.y. and parallel comparable phases in the evolution of other major geosynclinal zones such as the Appalachian, Caledonian, and Andean. The orthogeosynclinal phase (I) resulted in accumulation of offshore–deep-water (eugeosynclinal) slope (transitional) and shelf (miogeosynclinal) facies along the western continental margin. This phase was terminated by the Antler orogeny (IIa) in Late Devonian through Middle Pennsylvanian time. Clastic debris from the Antler belt was shed westward during late Paleozoic time into flanking eugeosynclinal troughs and eastward into epicontinental troughs; deposition in the western trough was terminated by the Sonoma orogeny (IIb) of Late Permian and Early Triassic age. The orogenic–late geosynclinal phase culminated in Jurassic (Nevadan and Sevier) orogeny (IIc), which coincided with early stage development of plate tectonics along the western continental margin. Depositional events of the postgeosynclinal phase (III) during Mesozoic and Tertiary time were characterized by orogenic and postorogenic flysch and molasse sedimentation in troughs and basins along the continental margin. These events were accompanied by andesitic volcanism and were related to plate tectonics. Mesozoic and Tertiary continental margins in North America have been classified into two major types: Atlantic type, characterized by prograding clastic wedges, and Cordilleran type, by underthrusting along continental margins. A third type, orthogeosynclinal, which is characterized by long-continued sedimentation and volcanism of major Paleozoic geosynclines, is proposed here. Orogenic mechanisms for continental margins recently have been discussed principally in terms of ocean-floor spreading and plate tectonics. Orogenic activity within the interiors of continents requires other mechanisms; these may include subcrustal phase changes and thermal expansion related to loading and subsidence. It is even possible that such phase changes and thermal expansion may play a significant role in orogenic activity along continental margins.

Plate Tectonics of Southeast Asia and Indonesia: ABSTRACT

The plate-tectonic evolution of a region can be deduced by following the assumptions that (1) subduction zones are characterized by ophiolite, melange, wildflysch, and blueschist; (2) intermediate and silicic calc-alkaline igneous rocks form above Benioff zones; and (3) truncations of orogenic belts indicate rifting. Interrelations provide cross checks, as do marine geophysical data. Southeast Asia and Sundaland are an aggregate of small continental fragments. Late Paleozoic subduction westward beneath Malaya and Thailand (recorded by granites in eastern Malaya, and by melanges in western Laos and Cambodia) ended when Indochina collided with them. Early and Middle Triassic subduction was eastward, beneath the west side of the aggregate. Late Triassic and Jurassic subduction from the north ended in collision of the aggregate with China. Early Cretaceous subduction was also from the west. Late Cretaceous subduction was beneath the east side of the aggregate and followed continental rifting there. Cenozoic subduction, from the west once more, ended in the north when the aggregate collided with India, but subduction still continues in the south. Borneo similarly ref ects changing subduction patterns. The Philippines, Sulawesi, and Halmahera consist wholly of upper Mesozoic(?) and Cenozoic island-arc subduction and magmatic complexes and lack old continental foundations. The scrambled fragments of the Philippines came from several arc systems, including 2 extending to Borneo. Sulawesi and Halmahera record primarily subduction from the east and may be rifted and contorted fragments initially continuous with southeast Borneo and central Java. In the early Tertiary, Australia and New Guinea, which then had a stable-shelf northern margin, moved northward until they collided with a southward-migrating island arc, behind which had formed the Caroline oceanic plate. Late Cenozoic tectonics in New Guinea have been dominated by southward subduction of the Caroline oceanic plate beneath the Australian-New Guinea continent, and by left-lateral strike-slip faulting. Such faulting tore the Sula Islands from northwest New Guinea and carried them to Sulawesi. The islands of the outer Banda arc are formed of melanges of the shallow-water sediments of the New Guinea and Australian continental shelf, which is now disappearing beneath the active arc. End_of_Article - Last_Page 621------------

A Model for Plate Tectonic Evolution of Mantle Layers

In plate tectonic theory, lithosphere that descends into the mantle has a largely derivative composition, because it is produced as a refractory residue by partial melting, and cannot be resorbed readily by the parent mantle. We suggest that lithosphere sinks through the asthenosphere, or outer mantle, and accumulates progressively beneath to form an accretionary mesosphere, or inner mantle. According to this model, there is an irreversible physicochemical evolution of the mantle and its layers. We make the key assumption that the rate at which mass has been transferred from the lithosphere to the mesosphere is proportional to the rate of radiogenic heat production. Calculations of mass transfer with time demonstrate that the entire mass of the present mesosphere could have been produced in geologically reasonable times (3 x 10(9) to 4.5 x 10(9) years). The model is consistent with the generation of the continental crust during the last 3 x 1O(9) years and predicts an end to plate tectonic behavior within the next 10(9) years.

Plate Tectonic Evolution of Caribbean–Gulf of Mexico Region

A geotectonic history of the American Mediterranean is presented in terms of plate tectonics. The development of this region is presented as seven time sequence reconstructions from past Palaeozoic to present times.