LI Shu-guang1,2

1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;

2. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China

Abstract：Tracing deep carbon recycling researches by using Mg isotopes have had some significant progresses during the last calendar year(2015-2016). Those progresses may include Mg isotopic compositions of altered oceanic crust, sediments, abyssal peridotites and recycled eclogites, origins of low δ26Mg basalts with EM-I or HIMU isotopic features, melting p-t conditions of low δ26Mg basalts constrained by Mg-Sr isotopes, carbonated mantle metasomatism in continental lithosphere revealed by Mg isotopes, deep carbon recycling induced by subduction of the Tethys oceanic plate and Mg isotopes fractionation in Na-rich carbonate magma. However, several important questions remain, including: (1)How to distinguish the effects on mantle Mg isotope compositions by recycled sedimentary carbonates or by recycled carbonated eclogites?(2)What is Mg isotopic behavior during slab subduction and why do island arc basalts have no low δ26Mg feature?(3)Where is the recycled carbon stored in the mantle and its residence time?(4)How do Mg isotopes fractionate in normal carbonatite magma?(5)How to trace the recycled carbonates that contain little Mg, such as calcite, aragonite or siderite? To answer these questions are important in the future research.

Key words：deep carbon Mg isotopes altered oceanic crust sediments basalts lithosphere mantle Tethys tectonic zone carbonate magma

Bulletin of Mineralogy, Petrology and Geochemistry Vol.36, No.2, 2017, page 197-203