Petrogenesis and tectonic significance of the Eocene adakite-like rocks in western Yunnan, southeastern Tibetan Plateau
作者： Huixia Ding , Qingye Hou , Zeming Zhang , None
DOI: 10.1016/J.LITHOS.2015.09.024
关键词: Petrology 、 Mafic 、 Zircon 、 Geochemistry 、 Petrogenesis 、 Crust 、 Partial melting 、 Geology 、 Adakite 、 Plateau 、 Back-arc basin
摘要: Abstract Eocene magmatic rocks are widespread in western Yunnan, southeastern Tibetan Plateau. However, their petrogenesis and tectonic significance remain controversial. In this paper, we report geochemical geochronological data of adakite-like from the eastern part Yunnan. Zircon U–Pb dating reveals that they were emplaced at ca. 35 Ma. A study shows these have high SiO2 (68.97–72.44 wt.%), K2O (4.35–5.87 wt.%) low MgO (0.61–1.16 wt.%), Y (6.65–12.6 ppm) Yb (0.58–1.02 ppm) contents as well Sr/Y (74–228) La/Yb (59–131) values, belonging to high-K calc-alkaline shoshonitic rocks. These (87Sr/86Sr)i (0.70623–0.70653), eNd(t) (− 4.5 − 7.5) slightly radiogenic Pb isotopic compositions with (206Pb/204Pb)i = 18.042–18.179. Zircons show eHf(t) values ranging − 6.3 + 1.2 model ages (TDM2) 1513–1035 Ma. The characteristics indicate Yunnan derived partial melting Neoproterozoic mafic underplated lower crust margin Yangtze Plate input mantle-derived potassic–ultrapotassic melt. Integration published clearly zircon whole-rock whole exhibit a trend westward increase. We infer late Paleozoic–Mesozoic formed continental arc during eastward subduction Paleo-Tethyan Ocean, generated removal thickened lithosphere triggered by India Asia collision.
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