How are melanges formed?

Although melanges are typical of accretionary prisms, they are formed by several different processes and occur in different tectonic environments (Lash, 1987). Tectonic melanges are produced by compressive forces along the upper part of descending slabs at shallow depths.

What is mélange zone in geology?

Mélange. A body of rock characterized by a lack of internal continuity of contacts or strata and by the inclusion of fragments and blocks of all sizes, both exotic and native, embedded in a fragmental matrix of finer-grained material. This category is also used for Melange.

What is mélange geography?

In geology, a mélange is a large-scale breccia, a mappable body of rock characterized by a lack of continuous bedding and the inclusion of fragments of rock of all sizes, contained in a fine-grained deformed matrix. A mélange is formed in the accretionary wedge above a subduction zone.

What type of rock is mélange?

Mélange (spelled melange in much English-language literature) describes heterogeneous rock units that contain blocks, typically of hard or structurally competent lithologies, surrounded and supported by a fine-grained matrix of shale, slate, or serpentinite.

How are melanges formed in a tectonic system?

Mélanges interpreted to have formed by tectonic processes are sometimes called tectonosomes. It is clear that mélanges form under conditions of low temperature, because the metamorphic grade is low and because some mélanges are dominated by brittle fracturing – both extensional and shear fractures are present.

What kind of rock is a melange made of?

Melange from Narooma, Australia. In geology, a mélange is a large-scale breccia, a mappable body of rock characterized by a lack of continuous bedding and the inclusion of fragments of rock of all sizes, contained in a fine-grained deformed matrix.

How are melanges related to the subduction zone?

Blocks include blueschists. The mélange dates from a time when plate reconstructions now show there was subduction of the Farallon Plate along the continental margin. Hence mélanges became associated very rapidly with deformation in trenches and subduction zones. Mélange is defined on the basis of the following criteria

Where does a melange occur in an orogenic belt?

Mélange occurrences are associated with thrust faulted terranes in orogenic belts. A mélange is formed in the accretionary wedge above a subduction zone. The ultramafic ophiolite sequences which have been obducted onto continental crust are typically underlain by a mélange.