A Petrographic Atlas of Ophiolite ebook is available to be downloaded here now.
- Title: A Petrographic Atlas of Ophiolite – An example from the eastern India-Asia collision zone.
- Authors: Naresh Chandra Ghose, Nilanjan Chatterjee, Fareeduddin
- Publisher: Springer
- Pages: 231
The basic tenet of the plate tectonic paradigm is that a newly generated oceanic plate is subducted at a trench. However, it is widely accepted today that some material is not subducted, but is accreted to form an accretionary wedge or prism, within which there may be a preserved section of the oceanic crust/mantle, known as an ophiolite. And many detailed studies now reveal that there are many types of ophiolites that may have formed, in e.g. a mid-oceanic ridge, close to a continental margin, and (the majority) in a suprasubduction zone.
Ophiolites commonly retain evidence of the low-temperature conditions of the ocean floor, and a few are closely associated with blueschists and eclogites, the metamorphic petrology of which provides information on the depths to which the material was subducted and exhumed. An associated accretionary wedge may contain relicts of ocean plate stratigraphy that records the travel history of the ocean floor as it moved laterally from ridge to trench. Most important are structures (e.g. extensional faults, thrusts, folds, lineations, kinematic indicators and S-C fabrics), which can only be obtained from detailed field work that will tell us if the ophiolite was rooted, for example in a ridge or an oceanic transform fault, and if it went through transpres sional or orthogonal shear during accretion.
Following that, and most importantly, microstructures related to textural relations and mineralogy of structurally oriented samples give us information about the physicochemical conditions during the magmatic and metamorphic history.
However, it seems to be accepted today that most papers on ophiolites provide just a brief list of the rock types, and then concentrate on the trace element rock chemistry, the mineral chemistry, the isotopic systematics and the zircon age, but with little petrographic information. But if we are to understand the origin and evolution of this key component of the Wilson Cycle, we need more information on the petrography and mineralogy, because it is that which relates the magmatic development to the metamorphic and structural history.
And above all, the non-ophiolite specialist, who is keen to understand the general nature of an ophiolite and how the petrology and mineralogy provide the key knowledge to work out the magmatic-metamorphic-structural history, increasingly requires innovative syntheses of such relations in different ophiolites, and such reviews are rare.