کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5784270 1638635 2017 32 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Garnet effect on Nd-Hf isotope decoupling: Evidence from the Jinfosi batholith, Northern Tibetan Plateau
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Garnet effect on Nd-Hf isotope decoupling: Evidence from the Jinfosi batholith, Northern Tibetan Plateau
چکیده انگلیسی
The initial Nd and Hf isotope ratios of a 420 Ma post-collisional dioritic-granitic batholith from the Northern Tibetan plateau define a negative trend above and orthogonal to the ԐHf(t)-ԐNd(t) terrestrial array. This uncommon trend offers an insight into the origin of the puzzling Nd-Hf isotope decoupling in the crustal rocks. On this trend, samples depleted in heavy rare earth elements (HREEs, i.e., [Dy/Yb]N ≫ 1) deviate most from the terrestrial array whereas samples with flat HREEs (i.e., [Dy/Yb]N ≥ 1) deviate less or plot within the terrestrial array, pointing to the controlling effect of garnet in the magma source. Ancient garnet-bearing residues after melt extraction will have elevated Lu/Hf ratios and can evolve with time to produce high ԐHf(t) at a low ԐNd(t) value. Mixing of melts derived from such source lithologies (high Lu/Hf) with melts possessing a within-terrestrial array Nd-Hf isotopic composition (low Lu/Hf) best explains the observed trend orthogonal to the terrestrial array. The samples from the Jinfosi batholith with the most decoupled Nd-Hf isotope compositions require a larger degree (> 40%) and ancient (i.e., ≥ 1.8 Gyr) previous melt extraction from their source. It follows that the ancient melts with depleted HREEs complementary to those garnet-bearing residues should have low ԐHf values and plot below the terrestrial array, which is indeed shown by some Archean/Paleoproterozic TTGs.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volumes 274–275, March 2017, Pages 31-38
نویسندگان
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