Short Note

Econ. Environ. Geol. 2017; 50(5): 375-387

Published online October 31, 2017

https://doi.org/10.9719/EEG.2017.50.5.375

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

A Preliminary Study on the Igneous Layering and Concentration of Fe-Ti Oxide Minerals within Amphibolite in Soyeonpyeong Island

Eui-Jun Kim*

Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea

Correspondence to : euijun.kim@kigam.re.kr

Received: October 9, 2017; Revised: October 27, 2017; Accepted: October 30, 2017

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

Amphibolite-hosted Fe-Ti mineralization at the Soyeonpyeong Island, located in central western part of the Korean Peninsula is a typical orthomagmatic Fe-Ti oxide deposit in South Korea. The amphibolite intruded into NW-SE trending Precambrian metasedimentary rocks. Lower amphibolite is characterized by igneous layering, consisting of feldspar-dominant and amphibole-Fe-Ti oxide-dominant layers. The igneous layering shows complicated and/or sharp contact. In contrast, upper amphibolite has a more complicated lithofacies (garnet-bearing, coarser, and schistose), and massive Fe-Ti oxide ore alternates with schistose amphibolite. NS- and EW-trending fault systems lead to redistribute upper amphibolite-hosted Fe-Ti orebody and igneous layering of lower amphibolite, respectively. The whole-rock compositions of amphibolite and Fe-Ti oxide ore reflect their constituent minerals. Amphibolite shows significantly positive Eu anomalies whereas Fe-Ti oxide ore has weak negative Eu anomalies. Plagioclase (Andesine to oligoclase) and Fe-Ti oxide minerals have constant composition regardless of their distribution. Amphibole has a compositionally variable but it doesn’t reflect the chemical evolution. Mineral compositions within individual layers and successive layers are relatively constant not showing any stratigraphic evolution. This suggests that there are no successive injections of Fe-rich magma or assimilation with Fe-rich country rocks. Contrasting Eu anomalies between amphibolite and Fe-Ti oxide ore also suggest that extensive plagioclase fractionation during early crystallization stage cause increase in Fe2O3/FeO ratio and overall Fe contents in the residual magma. Thus, Fe-rich residual liquids may migrate at the upper amphibolite by filter pressing mechanism and then produce sheeted massive Fe-Ti mineralization during late fractional crystallization.

Keywords Amphibolite, orthomagmatic Fe-Ti deposit, igneous layering, plagioclase fractionation, filter pressing

소연평도 각섬암 내 화성기원 층상구조와 Fe-Ti 산화광물의 농집에 관한 예비연구

김의준*

한국지질자원연구원 광물자원연구본부

요 약

Article

Short Note

Econ. Environ. Geol. 2017; 50(5): 375-387

Published online October 31, 2017 https://doi.org/10.9719/EEG.2017.50.5.375

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

A Preliminary Study on the Igneous Layering and Concentration of Fe-Ti Oxide Minerals within Amphibolite in Soyeonpyeong Island

Eui-Jun Kim*

Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea

Correspondence to:euijun.kim@kigam.re.kr

Received: October 9, 2017; Revised: October 27, 2017; Accepted: October 30, 2017

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

Amphibolite-hosted Fe-Ti mineralization at the Soyeonpyeong Island, located in central western part of the Korean Peninsula is a typical orthomagmatic Fe-Ti oxide deposit in South Korea. The amphibolite intruded into NW-SE trending Precambrian metasedimentary rocks. Lower amphibolite is characterized by igneous layering, consisting of feldspar-dominant and amphibole-Fe-Ti oxide-dominant layers. The igneous layering shows complicated and/or sharp contact. In contrast, upper amphibolite has a more complicated lithofacies (garnet-bearing, coarser, and schistose), and massive Fe-Ti oxide ore alternates with schistose amphibolite. NS- and EW-trending fault systems lead to redistribute upper amphibolite-hosted Fe-Ti orebody and igneous layering of lower amphibolite, respectively. The whole-rock compositions of amphibolite and Fe-Ti oxide ore reflect their constituent minerals. Amphibolite shows significantly positive Eu anomalies whereas Fe-Ti oxide ore has weak negative Eu anomalies. Plagioclase (Andesine to oligoclase) and Fe-Ti oxide minerals have constant composition regardless of their distribution. Amphibole has a compositionally variable but it doesn’t reflect the chemical evolution. Mineral compositions within individual layers and successive layers are relatively constant not showing any stratigraphic evolution. This suggests that there are no successive injections of Fe-rich magma or assimilation with Fe-rich country rocks. Contrasting Eu anomalies between amphibolite and Fe-Ti oxide ore also suggest that extensive plagioclase fractionation during early crystallization stage cause increase in Fe2O3/FeO ratio and overall Fe contents in the residual magma. Thus, Fe-rich residual liquids may migrate at the upper amphibolite by filter pressing mechanism and then produce sheeted massive Fe-Ti mineralization during late fractional crystallization.

Keywords Amphibolite, orthomagmatic Fe-Ti deposit, igneous layering, plagioclase fractionation, filter pressing

소연평도 각섬암 내 화성기원 층상구조와 Fe-Ti 산화광물의 농집에 관한 예비연구

김의준*

한국지질자원연구원 광물자원연구본부

Received: October 9, 2017; Revised: October 27, 2017; Accepted: October 30, 2017

요 약

    KSEEG
    Jun 30, 2024 Vol.57 No.3, pp. 281~352

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