Geochronological and geochemical constraints on the petrogenesis of alkaline ultramafic dykes from southwest Guizhou Province,SW China |
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| Authors: | Shen Liu Wenchao Su Ruizhong Hu Caixia Feng Shan Gao Ian M Coulson Tao Wang Guangying Feng Yan Tao Yong Xia |
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| Institution: | 1. Ecole et Observatoire des Sciences de la Terre, Université de Strasbourg (UdS-CNRS), F-67084 Strasbourg, France;2. School of Earth & Space Exploration, Arizona State University, Tempe, AZ 85287-1404, USA;3. Laboratoire d’Hydrologie et de Géochimie de Strasbourg, Université de Strasbourg (UdS-CNRS), F-67084 Strasbourg, France;4. CNRS, CEMHTI UPR3079, Université d''Orléans, F-45071 Orléans, France;5. SCK-CEN, Health, Environment and Safety Institute, B-2400 Mol, Belgium;1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China;2. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Geochronological, geochemical and whole-rock Sr–Nd isotopic analyses have been completed on a suite of alkaline ultramafic dykes from southwest (SW) Guizhou Province, China with the aim of characterising their petrogenesis. The Baiceng ultramafic dykes have a LA-ICP-MS zircon 206Pb/238U age of 88.1 ± 1.1 Ma (n = 8), whereas two phlogopites studied by 40Ar/39Ar dating methods give emplacement ages of 85.25 ± 0.57 Ma and 87.51 ± 0.45 Ma for ultramafic dykes from Yinhe and Lurong, respectively. In terms of composition, these Late Mesozoic ultramafic dykes belong to the alkaline magma series due to their high K2O (3.31–5.04 wt.%) contents. The dykes are characterised by enrichment of light rare earth element (LREE) and large-ion lithosphile elements (LILEs) (Rb and Ba), negative anomalies in high field strength elements (HFSEs), such as, Nb, Ta and Ti relative to primitive mantle, low initial 87Sr/86Sr ratios (0.7060–0.7063) and positive εNd(t) values (0.3–0.4). Such features suggest derivation from low degree (< 1%) partial melting of depleted asthenospheric mantle (garnet-lherzolite), and contamination to various degrees (～ 10%) by interaction with upper crustal materials. |
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