Neoproterozoic subduction along the Ailaoshan zone, South China : geochronological and geochemical evidence from amphibolite
Abstract
Lenses of amphibolites occur along the Ailaoshan suture zone at the southwestern margin of the Yangtze Block, South China. Petrological, geochemical and zircon U-Pb geochronological data indicate that they are divisible into two coeval groups. Group 1, represented by the Jinping amphibolite, has mg-number of 71-76 and (La/Yb)cn ratios of 7.2-7.7, and displays a geochemical affinity to island arc volcanic rocks. Group 2 amphibolites occur at Yuanyang and are characterized by high Nb contents (14.3-18.4 ppm), resembling Nb-enriched basalts. The epsilon(Nd)(t) values for Group 1 range from -3.45 to -2.04 and for Group 2 from +4.08 to +4.39. A representative sample for Group 1 yields a U-Pb zircon age of 803 7 Ma, whereas two samples for Group 2 give U-Pb zircon ages of 813 +/- 11 Ma and 814 +/- 12 Ma. Petrogenetic analysis suggests that Group 1 originated from an orthopyroxene-rich source and Group 2 from a mantle wedge modified by slab-derived melt. In combination with other geological observations, these amphibolites are inferred to constitute part of an early Neoproterozoic (similar to 815-800 Ma) arc-back-arc basin system. The Neoproterozoic amphibolites and related rocks along the Ailaoshan zone may be the southward extension of the Neoproterozoic supra-subduction zone that developed along the western margin of the Yangtze Block. (C) 2014 Elsevier B.V. All rights reserved.
Citation
Cai , Y , Wang , Y , Cawood , P A , Fan , W , Liu , H , Xing , X & Zhang , Y 2014 , ' Neoproterozoic subduction along the Ailaoshan zone, South China : geochronological and geochemical evidence from amphibolite ' , Precambrian Research , vol. 245 , pp. 13-28 . https://doi.org/10.1016/j.precamres.2014.01.009
Publication
Precambrian Research
Status
Peer reviewed
ISSN
0301-9268Type
Journal article
Description
This study was supported by China Natural Science Foundation (41190073 and 41372198), National Basic Research Program of China (2014CB440901) and Natural Environment Research Council (grant NE/J021822/1).Collections
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