Abstract
Adakite[1] is an igneous rock generated by the partial melting of subducting ocean slab in an island arc setting. Meanwhile, residuals of the slab-melting are transformed to eclogite or garnet-amphibolite during a slab subduction process. This note reports the adakite-type grey gneisses discovered in the North Dabie Mountain. These adakitic rocks are characterized by high Al2O3,(14.97%–17.56%), Sr (545–941 gm/g), Sr/Y (44.71–218.98), La/Yb (16.70–97.50), and low Y (3.32–12.19 μg/g), Yb (0.31–1.34 μg/g), Sc (0.92–4.2 μg/g), as well as positive Sr anomaly but absent or positive Eu anomaly. They are different from the low aluminum grey gneisses with low Al2O3 (13.73%–14.38%), Sr (262–409 μg/g), Sr/Y (6.46–15.97) and La/Yb (1.90–22.60), high Y(21.79–36.24 μg/g), Yb (2.00–5.59 μg/g), Sc (8.30%–12.70%), and negative Sr, Eu anomaly in the North Dabie Mountain. The adakite-type grey gneisses in the North Dabie Mountain were most probably formed by the partial melting of subducting ocean slab before the Indo-Chinese epoch. We suggest that the subducting of an ocean slab took place prior to the incorporation between the Yangtze and North China plates in the Indo-Chinese epoch, resulting in formation of adakite-type igneous rocks and some ultrahigh pressure eclogites related to the subducted ocean slab. Therefore, besides the ultrahigh pressure metamorphism of the Indo-Chinese epoch, some ultrahigh pressure ecoglits were most likely formed prior to the Indo-Chinese epoch in the Dabie Mountain. In addition, the adakite-type grey gneisses with arc origin occur in the North Dabie Mountain, inferring that the Yangtze plate subducted down below the North China plate and the main suture zone between the two plates was likely along the southern side to the North Dabie Mountain.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call