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https://hdl.handle.net/2440/116344
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Type: | Journal article |
Title: | Early Silurian to Early Carboniferous ridge subduction in NW Junggar: evidence from geochronological, geochemical, and Sr-Nd-Hf isotopic data on alkali granites and adakites |
Author: | Zhang, C. Santosh, M. Liu, L. Luo, Q. Zhang, X. Liu, D. |
Citation: | Lithos, 2018; 300-301:314-329 |
Publisher: | Elsevier |
Issue Date: | 2018 |
ISSN: | 0024-4937 1872-6143 |
Statement of Responsibility: | Chen Zhang, M.Santosh, Luofu Liu, Qun Luo, Xin Zhang, Dongdong Liu |
Abstract: | The Central Asian Orogenic Belt (CAOB) evolved through a long-lived orogeny involving multiple episodes of subduction and accretion marking a major phase of continental growth during the Paleozoic. The northern part of the Western Junggar region (NW Junggar) offers a window into these processes, particularly to constrain the timing of closure of the Paleo-Asian Ocean. Here we report geochemical, geochronological, and isotopic data from K-feldspar granites and adakitic rocks from the NW Junggar region. Zircon U-Pb ages suggest that the granites were emplaced during Early Silurian to the Early Carboniferous (434–328 Ma). The granites show geochemical characteristics similar to those of A-type granites, with high SiO2 (71.13–76.72 wt%), Na2O + K2O (8.00–9.59 wt%), and Al2O3 (12.28–14.08 wt%), but depleted Sr, Nb, Ta and Eu. They display moderate to high positive εNd(t) and εHf(t) values (4.26–8.21 and 7.69–14.60, respectively) and young Nd and Hf model ages (T2DM-Nd = 489–740 Ma and T2DM-Hf = 471–845 Ma), suggesting magma derivation through partial melting of lower crust in the Boshchekul-Chingiz and Zharma-Saur arcs. The adakites are characterized by high Sr content (406.5–751.6 ppm), and low Y (13.8–16.4 ppm) and Yb (1.5–1.8 ppm) content, yielding relatively high Sr/Y ratios (25.38–49.41) similar to those of modern adakites. They have high positive εNd(t) and εHf(t) values (7.85–8.25 and 13.23–15.97, respectively) and young Nd and Hf model ages (T2DM-Nd = 429–535 Ma and T2DM-Hf = 355–550 Ma), indicating that their source magmas were likely derived from partial melting of the oceanic crust beneath the Boshchekul-Chingiz arc. The petrogenesis and distribution of the A-type granites and adakites, as well as the tectonic architecture of the region, suggest that a ridge subduction event might have occurred during the Early Silurian to Early Carboniferous. In combination with previous studies in the Chinese Altai, we suggest a two-sided ridge subduction model for the Junggar-Altai region. |
Keywords: | Granites; Two-sided ridge subduction; geochemistry and zircon geochronology; Sr-Nd-Hf isotopes; Central Asian Orogenic Belt |
Rights: | © 2017 Elsevier B.V. All rights reserved. |
DOI: | 10.1016/j.lithos.2017.12.010 |
Published version: | http://dx.doi.org/10.1016/j.lithos.2017.12.010 |
Appears in Collections: | Aurora harvest 3 Geology & Geophysics publications |
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