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Non‐subduction origin for 3.2 Ga high‐pressure metamorphic rocks in the Barberton granitoid‐greenstone terrane, South Africa
Author(s) -
Wang Hao,
Yang JinHui,
Kröner Alfred,
Zhu YuSheng,
Li Rui
Publication year - 2019
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/ter.12397
Subject(s) - terrane , geology , metamorphism , magmatism , geochemistry , greenstone belt , metamorphic rock , zircon , subduction , archean , continental crust , fibrous joint , petrology , titanite , crust , seismology , tectonics , medicine , anatomy
The occurrence of high‐pressure ( HP ) garnet‐bearing metamorphic rocks in the southern Barberton granitoid–greenstone terrane ( BGGT ), South Africa, has been proposed as a key indicator of the onset of modern plate tectonics at ca. 3.2 Ga. Here, we report new zircon/titanite U–Pb ages of garnet‐bearing HP metamorphic rocks and associated granitoids in the BGGT that argue against such an interpretation. The results show that HP metamorphism occurred synchronously with granitoid magmatism in the Stolzburg domain, the supposed subducted plate, during two episodes at 3.4 and 3.2 Ga, and that these two episodes of magmatism occurred on both sides of the assumed suture zone, a feature that cannot easily be explained by the subduction model. In contrast, the coupled magmatism and metamorphism probably resulted from partial convective overturn ( PCO ), another viable mechanism for production and differentiation of continental crust during early Archean.