ultramafic rocks are known as ophiolites. Many geologists believe that ophiolites formed at oceanic ridges were emplaced by tectonic forces at convergent plate boundaries and then became exposed in highly deformed orogenic (mountain) belts.

Where does ophiolite occur?

An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks.

Why is an ophiolite important?

Since scientists have never drilled deep enough into the Earth to observe the mantle, ophiolites are important because they are places where geologists can observe large sections of mantle rocks directly. ... Since then, many more mantle exposures have been discovered, particularly on the ocean floor.

What is ophiolite sequence?

Ophiolite sequences are indicators of sea-floor spreading where the oceanic crust is thinned by the forces of plate tectonics, and magma rises to the sea's floor and generates new crust.

What are the 3 main layers in an ophiolite?

Sediments (layer 1) Volcanic Crust (layer 2) Plutonic Crust (layer 3) Mantle Harzburgite (layer 4) 4 layers distinguished from Geophysics: Typical Ophiolite: 1.

Ch4 Ophiolites

What is ophiolite where is it located in the Philippines?

Abstract. The Zambales Ophiolite Complex (ZOC) in the western portion of Luzon Island, Philippines represents a typical exposure of an emplaced crust-upper mantle section of an ancient lithosphere.

What is an ophiolite rock?

Ophiolite is thrust sheets of ancient oceanic crust and upper part of mantle rocks that have been uplifted and exposed above sea level and often emplaced on top of the continental lithosphere.

How is serpentinite rock formed?

The serpentinite is formed by the hydrous alteration and low-temperature metamorphic alteration of igneous ultramafic rocks. These rocks are composed of olivine and pyroxene in different ratios to form peridotite and pyroxenite.

What is an ophiolite quizlet?

An ophiolite is a section of oceanic crust and upper mantle (oceanic lithosphere) that has been transported along thrust faults and uplifted and emplaced on the margins of a continent or other land mass.

What is the ophiolite complex?

Ophiolite is a stratified igneous rock complex composed of upper basalt member, middle gabbro member and lower peridotite member (Fig. 1). Some large complexes measure more than 10 km thick, 100 km wide and 500 km long. The term "ophiolite" means "snake stone" in Greek.

Where do the ophiolite suite of rocks occur in India?

In IMR the ophiolitic rocks occur in two parallel belts (Eastern belt and Western belt) along the eastern margin of the Indian plate. The Eastern belt passes through central Myanmar, Sumatra, and Java whereas the Western belt passes through Nagaland, Manipur, western Myanmar, and Andaman.

What does an Obduction mean?

: an act or instance of drawing or laying something (as a covering) over.

Where is the ophiolite complex located?

The Baie Verte Lineament, located in the Burlington Peninsula, northwest Newfoundland, is a steeply-dipping linear belt 90 km long by 1 to 5 km wide containing a variably disrupted ophiolite suite and other mainly mafic volcaniclastic and volcanic rocks that originally overlay the ophiolite complex.

How is an accretionary wedge formed?

An accretionary wedge or accretionary prism forms from sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary. ... Accretionary complexes are typically made up of a mix of turbidites of terrestrial material, basalts from the ocean floor, and pelagic and hemipelagic sediments.

What rocks are included in an ophiolite sequence list them stratigraphically from bottom to top?

The stratigraphic sequence observed in an ophiolite corresponds to layered oceanic crust: from top to bottom, an upper layer of oceanic sediment (siliceous or carbonate ooze); a layer of pillow basalt; a layer of sheeted near-vertical dykes; layers of gabbro and plagioclase and mafic cumulates; and a basal layer of “ ...

What are the rock type members of an ophiolite sequence?

Franciscan ophiolites consist of fragments of peridotite, gabbro and basaltic rocks, representing fragments of a mid-ocean ridge setting. The igneous rocks are associated with pelagic chert and limestone.

What is an ophiolite sequence quizlet?

Ophiolite suite. A sequence of rocks consisting of deep-sea marine sediments overlying (from top to bottom) pillow basalts, sheeted dikes, gabbro, dunite, and peridotite.

Why is serpentinite an important rock where plates move?

Serpentine rock, so called because the pattern of the rock surface resembles a serpent's skin, is actually a rock type originally formed from ultramafic rock. ... Ultramafic rock migrates across the ocean floor along with the crust. A process called plate tectonics drives crustal movement.

What is serpentinite made out of?

Serpentinite rocks are almost exclusively made of serpentine minerals. The most common serpentine mineral in Franciscan rocks is antigorite. This mineral gives the serpentinite its characteristic light to dark green color.

Why is it called serpentinite?

Serpentinite is a rock composed of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. ... The mineral alteration is particularly important at the sea floor at tectonic plate boundaries.

Where is eclogite found?

The eclogites have a relatively small presence and share of the metamorphic rocks in the Earth's crust but are the main ingredients with peridotite of Earth layer (Section 5.1). Eclogite is a rare and significant rock formed only by conditions typically found in the mantle or the lowermost part of the thickened crust.

What types of rocks make up an ophiolite?

An ophiolite is a section of the Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level. The rocks which make up ophiolites are an altered form of basalt. The rocks are often green.

Where can I find igneous rocks in the Philippines?

1. Kapurpurawan Rock Formations – Ilocos Norte. ...
2. Biri Rock Formations – Northern Samar. ...
3. Nakabuang Arch – Sabtang Island, Batanes. ...
4. Alapad Rock Formation – Batan, Batanes. ...
5. Animasola Island – Masbate.

Where is basalt commonly found in the Philippines?

Normal (N)-MORB-like basalts were found at DSDP Sites 290 and 447 near the Central Basin Fault to the SW of Site 1201D, and enriched (E)-MORB-like basalts were found at DSDP Site 291 in the southern West Philippine Basin. OIB-like basalts were found at DSDP Sites 292, 294 and 446 (Fig. 1).

How was Zambales mountains formed?

Volcanoes. Although the mountains are volcanic in origin, Mount Pinatubo is the only active volcano in the mountain range. Its eruption on June 15, 1991, was the second most powerful volcanic eruption of the 20th century after the 1912 eruption of Novarupta in Alaska.