Introduction to the structures and processes of subduction zones

• Published in: Journal of Asian earth sciences 2017-09, Vol.145, p.1-15
• Main Authors: Zheng, Yong-Fei, Zhao, Zi-Fu
• Format: Article
• Language: English
• Subjects: Crustal metasomatism; Extreme metamorphism; Interplate magmatism; Intraplate magmatism; Rifting orogeny; Subduction channel; Subduction factory
• ISSN: 1367-9120; 1878-5786
• DOI: 10.1016/j.jseaes.2017.06.034

[Display omitted] •Subduction zones are different in their geometric, geological and thermal structures.•Subduction zones processes include metamorphic dehydration, partial melting and crustal metasomatism.•Subduction zone fluids serve as metasomatic agents for crust-mantle interaction in subduction channels.•The composition of metasomatic agents is primarily dictated by the thermal structure of subduction zones.•Plate tectonics develops from interplate compression by subduction to intraplate extension by rifting. Subduction zones have been the focus of many studies since the advent of plate tectonics in 1960s. Workings within subduction zones beneath volcanic arcs have been of particular interest because they prime the source of arc magmas. The results from magmatic products have been used to decipher the structures and processes of subduction zones. In doing so, many progresses have been made on modern oceanic subduction zones, but less progresses on ancient oceanic subduction zones. On the other hand, continental subduction zones have been studied since findings of coesite in metamorphic rocks of supracrustal origin in 1980s. It turns out that high-pressure to ultrahigh-pressure metamorphic rocks in collisional orogens provide a direct target to investigate the tectonism of subduction zones, whereas oceanic and continental arc volcanic rocks in accretionary orogens provide an indirect target to investigate the geochemistry of subduction zones. Nevertheless, metamorphic dehydration and partial melting at high-pressure to ultrahigh-pressure conditions are tectonically applicable to subduction zone processes at forearc to subarc depths, and crustal metasomatism is the physicochemical mechanism for geochemical transfer from the slab to the mantle in subduction channels. Taken together, these provide us with an excellent opportunity to find how the metamorphic, metasomatic and magmatic products are a function of the structures and processes in both oceanic and continental subduction zones. Because of the change in the thermal structures of subduction zones, different styles of metamorphism, metasomatism and magmatism are produced at convergent plate margins. In addition, juvenile and ancient crustal rocks have often suffered reworking in episodes independent of either accretionary or collisional orogeny, leading to continental rifting metamorphism and thus rifting orogeny for mountain building in intracontinental settings. This brings complexity to distingui