We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
P-T-t Path of Garnetites in South Altyn Tagh, West China: A Complete Record of the Ultradeep Subduction and Exhumation of Continental Crust.
- Authors
Jie Dong; Chunjing Wei; Jing Chen; Jianxin Zhang
- Abstract
We report here a detailed investigation of mineral chemistry, phase modelling and geochronology for garnetites from the Bashiwake ultrahigh pressure (UHP) terrane, South Altyn Tagh, West China. Three generations of mineral assemblages including two stages of melting were identified. The first generation is represented by the zoning with decreasing grossular and increasing pyrope and multiphase inclusions in garnet core. It records an early-stage prograde evolution from amphibolite facies to eclogite facies (1.7-2.5 GPa/710-850 °C) where the first stage of melting occurs. The second generation is characterized by the zoning in garnet mantle with increasing grossular and nearly constant pyrope, defining a later-stage prograde evolution to UHP peak with the minimum condition of 6.5-7.0 GPa/990 °C. The pressure is consistent with that constrained from the pigeonite exsolution particularly along (401) planes in clinopyroxene. The third generation includes the presence of perthite, plagioclase along with amphibole, suggesting the decompression from eclogite facies to HP-ultrahigh-temperature (UHT) granulite facies (~3.3-1.2 GPa/960-1020 °C) coupled with the second stage of melting. It is for the first time to get two metamorphic ages about 500 Ma and 486 Ma using in situ SIMS zircon dating which represent the prograde eclogite facies and decompressional granulite facies stages, suggesting the rocks staying at mantle depths for ~14 million years. The garnetites have recorded a complete metamorphic P-T-t history of continental ultradeep subduction to mantle depths of ~200 km or more followed by diapiring exhumation to the crust bottom.
- Subjects
ALTUN Mountains (China); AMPHIBOLITES; CONTINENTAL crust; GEOLOGICAL time scales; EXHUMATION
- Publication
Journal of Geophysical Research. Solid Earth, 2020, Vol 125, Issue 2, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2019JB018881