A subduction channel model for exhumation of oceanic-type high-pressure to ultrahigh-pressure eclogite-facies metamorphic rocks in SW Tianshan, China
A subduction channel model for exhumation of oceanic-type high-pressure to ultrahigh-pressure eclogite-facies metamorphic rocks in SW Tianshan, China
复制标题
西南天山大洋型高压至超高压榴辉岩相变质岩折返俯冲水道模型
DOI：
10.1007/s11430-016-5103-7
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发表时间：
2016-11
期刊：
影响因子：
--
通讯作者：
Wang Xin-Shui
中科院分区：
文献类型：
--
作者：
Li Ji-Lei;Gao Jun;Wang Xin-Shui
High-pressure (HP) and ultrahigh-pressure (UHP) eclogites exposed in collisional orogens are widely regarded to record the history of crustal rocks that were subducted to mantle depths and exhumed back to the surface. Insight into subduction and exhumation processes plays an important role in understanding the nature and evolution of subduction zones, geodynamics and plate tectonics. In contrast to continental-type HPto UHPmetamorphic rocks that are dominated by felsic lithology, oceanic-type HPto UHPmetamorphic rocks are dominated by mafic eclogites and thus have greater density, and their exhumation needs to overcome large barriers and may involve complicated tectonic processes. The exhumation of HPto UHProcks is mainly influenced by the internal buoyancy, however, the external tectonic forces (such as channel flow) also act as effective exhumation drivers; in addition, effects of tectonic settings (such as slab rollback and breakoff) should take into account. The HP-UHPmetamorphic terrane in Southwestern Tianshan, which mainly comprises of metasediments with interlayered metamafic lenses and blocks, represents a typical accretionary mélange associated with deep subduction of oceanic crust. However, the exhumation mechanisms of these once deeply buried HP-UHProcks are still under discussion. Based on the field occurrences, petrographic features, peak metamorphicP-Tconditions and ages of the eclogites/blueschists and their metasedimentary country rocks, a “sediment-type subduction channel” model is advocated in this study to appraise/decipher the formation and evolution of Southwestern Tianshan HP-UHPmetamorphic belt. Poly-cyclic metamorphic eclogites record the multistage burial-exhumation cycling manipulated by convective flow in a channel-like interface between the plates, giving robust evidence for the presence of a subduction channel. In addition, this study summarizes some remaining geotectonic problems and research perspectives concerning the Southwestern Tianshan HP-UHPmetamorphic belt.
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