Ophiolite complexes are the suite of rocks that became the product of the spreading centers of plate boundaries. Ophiolites or “snake stones” are originally coined by Alexandre Brongniart in 1813 mainly because of its green rocks comprising of serpentine and diabase. Initially, geologists and paleontologists of the 1950s and 1960s hypothesized that oceanic crust emplacements and seafloor spreading might be the cause of ophiolite complexes.
According to Kearey and Vine (1996, 24), earlier propositions on ophiolite complexes are associated with (a) magnetic anomaly markings on the seafloor resembling to a stripe-like patterns, and (b) intrusions of magma and spreading of the oceanic ridges. As mentioned by Dilek and Newcomb (2003, 153) of the Geological Society of America, the understanding of ophiolite complexes are significant in understanding the concepts of continent collision since these complexes are believed to be the fragments of oceanic crusts and mantle formed at oceanic ridges subduction zone environments.
As these tectonic plates break away, the upwelling magma directs its way towards the oceanic crust fractures and eventually creating different formations of rock along its path. According to Kusky (2004, 35), ophiolites, such as Precambrian and Apennine types, provide an indicative representation of potential modern plate tectonism. Clearly, ophiolite complexes are generated by some type of sea-plate-spreading and fractures zones, seamounts and plateaus (Dilek and Newcomb, 2003 153).
The Term Paper on Sedimentary Rock 2
... of mantleperidotite and the metamorphic eclogites are exposed as ophiolite complexes. The newly erupted volcanic material is subject to rapid ... of the rock cycle as Plate tectonics became recognized as the driving force for the rock cycle. [edit]Spreading ridges The ... Fuca plate sinks below the North America plate at the Cascadia subduction zone. Main article: Subduction The new basaltic oceanic crust ...
The physical age of ophiolite creations is often quite close to the actual age of their emplacement into the continental plates.
Discussion Ophiolite complexes possess their distinctive layered compositions with thickened oceanic crusts (Mason, 1990 108).
According to Kearey and Vine (1996, 24), ophiolites commonly resembles snakeskin; hence, the name snake stones, and such rock formations are most often seen among collisional belts in the mountains and/or deep seas. These complexes are considered prime residues of the oceanic crusts and underlying oceanic mantle, which have been present under the continental crust.
According to the definitions stated by Dilek and Newcomb (2003, 153), “ophiolite complexes are the ordered sequences from harzburgite, through banded and then isotropic gabrro with trondhjemite, to sheeted dike complex, then pillow lava, and sediment. ” As supported by Valdiya (1998, 68), the severity of continental collisions directly affects the entire sedimentary assemblage present in the deep sea trenches and adjoining oceanic crusts, which eventually split or folded into a stack of mutually overlapping slices in the oceanic fracture.
Ophiolites are overlain by a sedimentary section that includes ribbon cherts, shale interbeds, podiform bodies of chromite, sodic felsic rocks and limestone formations that are most of the time minimally present (Carlson, 2005 114).
Due to certain degrees of tectonic processes (e. g. sharing of salient features, etc. ), these complexes trigger a passive margin ophiolite, which is usually made of two components namely (1) subcontinental lithospheric mantle (SCLM) and (2) aesthenospheric component (Kusky 2004, 35).
Carlson (2005, 115) adds that these ophiolite complexes might even be associated to the early phases of oceanization as supported by various structural and stratigraphical evidences of seafloor spreading in open ocean environment. Formations of ophiolite complexes have evolved according to many contributing factors, such as oceanic crust changes, sea salinity compositions, and most importantly, the phase of spreading ridges on major ocean basins and marginal seas (Hsu and Jenkyns, 1974 385).
The Term Paper on Continental Drift Earth Continents Plates
In the early 1960 s, the emergence of the theory of plate tectonics started a revolution in the earth sciences. Since then, scientists have verified and refined this theory, and now have a much better understanding of how our planet has been shaped by plate-tectonic processes. We now know that, directly or indirectly, plate tectonics influences nearly all geologic processes, past and present. ...
Ophiolite complexes are commonly brought by the progressive emplacement of mafic and ultramafic rocks that represent fragments of the oceanic crusts – (1) mid-ocean ridges, (2) supra-subductions and (3) back arc basins (Condie, 1997 70).
Initially, the forming of ophiolite complex starts with the suprasubduction-zone creating over the sinking slab and separating from the passive continental margin aided by a force exerted by the spreading centers. In the process, ophiolite formation halts in order to metamorphose basalt layers through the high lithospheric heat influx in the ridge crest, and eventually forming the passive-margin sediments.
In the next phase, the ophiolite is emplaced onto the passive continental margin, while the suprasubduction zone ophiolite complex forms over the sinking slab. Lastly, abyssal sediments and scrapes from volcanic rocks from the subducting oceanic plates accumulate forming the accretionary prism, which eventually continues to grow and thicken forming the edge of the ophiolite complex (Wright and Shervais, 2008 214).
Ideally, ophiolite complexes possess the following organized units, specifically (1) ultramafic tectonite (a. . a. harzburgites), (2) layered accumulation of gabbros with ultramafic rocks, (3) non-cumulate gabbros with diorites and plagiogranites, (4) sheeted diabase dykes, and lastly (5), pillowed basalts (Condie, 1997 70).
Surprisingly, the advent of ophiolite formations is somehow close to the age of emplacement of the continental crusts. Nevertheless, the formation of ophiolites sometimes varies according to the surrounding environment and activities utilized during its formation.
For example, ophiolite complexes, such as those found in the Platta Nappe do not possess sheeted complexes representing the possible partial melting of the subcontinental mantle. According to Kearey and Vine (1996, 25), ophiolites represent the lithosphere’s obduction under high temperature and usually involves activities in the marginal seas (e. g. Red Sea-type oceans, etc,), which are the common site of ophiolite formations. On the other hand, ophiolite complexes found in the Balkan and Greece’s Vourinos possess sheeted dike complexes with notable pindos and troughs (Dilek and Newcomb 2003, 155).
The Essay on The Formation of Rocks in Ireland
It is the most widespread type of intrusive igneous rock at the earth’s surface. Igneous rocks form when molten rock is erupted at a volcano and then cools and hardens to form solid rock (Holden, 2012). Granite rock is created when magma is forced between other rocks deep within the earths crust. The magma then cools due to the drop in temperature and crystallizes in caverns deep within the earth. ...
Ophiolite complexes found in the Semail Complex in Oman, Troodos Complex in Cyprus and New Guinea’s complexes are perfect representations of supra-subduction zone activities. According to Kusky (2004, 35), ophiolite complexes are indications of oceanic lithosphere formations in different plate tectonic settings, such as oceanic spreading ridges, island arcs, back arc basins, leaky transforms, nascent ocean basins, etc. Conclusion In conclusion, ophiolite complexes are significant formations brought by the lifting of oceanic crust and the subjacent upper mantle.
Ophiolite complexes are representations of the residues or remnants of the oceanic crusts under the mantle brought by spreading centers of plate boundaries. The formation of these complexes start with the suprasubduction-zone until its forms its different layered structure aided by the progressive lithosphere heat influx. Eventually, ophiolite formations accumulate layered structure of harzburgites, gabbros with ultramafic rocks, diorites and plagiogranites, diabase dykes, and pillowed basalts.
