Ultrahigh Pressure Metamorphism and Tectonic Evolution of Southwestern Tianshan Orogenic Belt, China: A Comprehensive Review

Abstract

Recently, a huge ultrahigh‐pressure (UHP) metamorphic belt of oceanic‐type has been recognized in southwestern (SW) Tianshan, China. Petrological studies show that the UHP metamorphic rocks of SW Tianshan orogenic belt include mafic eclogites and blueschists, felsic garnet phengite schists, marbles and serpentinites. The well‐preserved coesite inclusions were commonly found in eclogites, garnet phengite schists and marbles. Ti‐clinohumite and Ti‐chondrodite have been identified in UHP metamorphic serpentinites. Based on the PT pseudosection calculation and combined U‐Pb zircon dating, the P‐T‐t path has been outlined as four stages: cold subduction to UHP conditions before ∼320 Ma whose peak ultrahigh pressure is about 30 kbar at 500oC, heating decompression from the Pmax to the Tmax stage before 305 Ma whose peak temperature is about 600oC at 22kbar, then the early cold exhumation from amphibolite eclogite facies to epidote‐amphibolite facies metamorphism characterized by ITD PT path before 220 Ma and the last tectonic exhumation from epidote amphibolite facies to greenschist facies metamorphism. Combining with the syn‐subduction arc‐like 333‐326 Ma granitic rocks and 280‐260 Ma S‐type granites in the coeval low‐pressure and high‐temperature (LP‐HT) metamorphic belt, the tectonic evolution of Tianshan UHP metamorphic belt during late Cambrian to early Triassic has been proposed.

Multistage CO2 sequestration in the subduction zone: Insights from exhumed carbonated serpentinites, SW Tianshan UHP belt, China

“…11; see Section 4.7.2 for calculation details) under variable P-T conditions along the retrograde path of the Tianshan (red arrow line in Fig. 10; Zhang et al, 2018). At temperatures of 600-400 °C along this P-T path, fluids in equilibrium with carbonate-bearing eclogite contain substantially higher total dissolved C concentration than those in equilibrium with ophidolomite (Fig.…”

“…The composition and speciation of fluids in equilibrium with ophidolomite and carbonate-bearing eclogite along the retrograde metamorphic P-T path of the Tianshan (Zhang et al, 2018) were calculated using the Deep Earth Water (DEW) aqueous database (revised version after Huang and Sverjensky, 2019) implemented with Perple_X . The attained fluid compositions correspond to those of the pervasively infiltrated fluids in overall equilibrium with ophidolomite in the Ca-Fe-Mg-Al-Si-C-O-H system (Sample C1518; Table 5) and carbonate-bearing eclogite in the Na-Ca-K-Fe-Mg-Al-Si-C-O-H system (Sample L0910 from .…”

The Exhumation of Subducted Oceanic‐Derived Eclogites: Insights From Phase Equilibrium and Thermomechanical Modeling

“…Moreover, the episodic exhumation also exists in the Rhodope Mountains (northern Greece) and the southwestern Massif Central (Variscan Belt, France; Bellot & Roig, ; Krohe & Mposkos, ). Recently, Zhang et al () found that it could take more than 60 Ma for the stagnation of Tianshan UHP eclogites in Moho and Conrad discontinuities. Besides, the Moho stagnation may have profound effects on the overprinting of eclogites during exhumation by granulite‐ or amphibolite‐facies retrograde metamorphism.…”

Diapir Melting of Subducted Mélange Generating Alkaline Arc Magmatism and Its Implications for Material Recycling at Subduction Zone Settings

“…The South Tianshan exposes an HP–UHP metamorphic belt named the Akesayi Metamorphic Complex (AMC) (Figure S1a in Supporting Information ). The AMC is made mainly of schistose meta‐volcanoclastic rocks hosting mafic metavolcanic rocks, marbles, and rare ultramafic rocks (Bayet et al., 2020; Klemd et al., 2015; Zhang et al., 2018). Bayet et al.…”