Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (3): 191-201.DOI: 10.13745/j.esf.sf.2020.1.1

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Garnet trace elemental geochemistry and its application in sedimentary provenance analysis

HONG Dongming,JIAN Xing,HUANG Xin,ZHANG Wei,MA Jinge   

  1. 1. State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
    2. CAS Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
  • Received:2018-05-28 Revised:2019-01-02 Online:2020-05-20 Published:2020-05-20

Abstract:

Garnet is a common heavy mineral in sediments. It can come from a variety of rocks and shows a variety of geochemistry compositions in different parent-rocks. Therefore, geochemical analysis of detrital garnet is widely used in sedimentary provenance research. The elemental geochemistry of single detrital mineral is easily obtained by electron microprobe and applied to the provenance analysis. However, there are certain limitations. For instance, the major elemental compositions of garnet in both intermediate-acid igneous rocks and metasedimentary rocks are usually characterized by high Fe and Mn. Here, we systematically investigated trace elemental geochemical data of garnet from different types of rocks and attempted establishing some useful trace elemental proxies for detrital garnet provenance analysis. The main conclusions are: (1) Rare earth elements and yttrium can be employed to distinguish detrital garnets from intermediate-acid igneous and metasedimentary rocks; (2) Garnets from basic rocks (peridotite, pyroxenite) and the corresponding meta-basic rocks (eclogite) had fairly consistent major and trace elemental geochemistry, but some garnets from peridotite rocks had unique praseodymium/holmium (PrN/HoN) values and total heavy rare earth elements (ΣHREE), which can be applied to sedimentary provenance analysis with basic rock-dominanted backgrounds; (3) Garnet in skarn was characterized by overwhelmingly high Ca, but rare earth element compositions were diverse, which can be interpreted as magma type (indicating rich iron and oxidation environment) or contact metasomatic type (reflecting rich aluminum and reducing environment). Collectively, the trace elemental geochemistry of garnet can be effectively used in sedimentary provenance analysis, which is an important supplement to the major element-based provenance analysis.

Key words:  garnet, major elements, trace elements, provenance analysis

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