Unique sodic–calcic skarn hosted by ultramafic rocks and albitite at the Ulsan skarn deposit, Gyeongsang Basin, South Korea

Jieun Seo, Seon–Gyu G. Choi, Ji Won Kim, In–Chang C. Ryu

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


The Ulsan Fe–W skarn deposit is located within the Cretaceous Gyeongsang Basin in the southeastern part of the Korean Peninsula. The skarn and mineralization formed along contacts between the Paleogene Gadaeri granite, limestone, partially serpentinized ultramafic rocks (dunite and harzburgite), and hornfelsed volcanic and siliciclastic rocks. These various country rock types produced a system with multiple types of skarn. Typically, skarn within limestone occurs as clinopyroxene–magnetite skarn, clinopyroxene–garnet skarn, and garnet skarn, but the unique host rocks (ultramafic rocks + albitite) at Ulsan also produced unusual skarn types such as a sodic–calcic skarn system. Na–Ca skarn formed by chemical interactions between albitized granites and adjacent ultramafic rocks. This Na–Ca skarn contains unusual Na-rich clinopyroxene (acmite), Na-rich amphiboles, Cr-rich clinopyroxene, Cr-rich amphiboles, Sr-bearing plagioclase, and Ba-bearing K-feldspar. Clinopyroxene and amphibole have Na 2 O concentrations up to 6.5 wt%, and these minerals contain up to 12.1 and 2.5 wt% Cr 2 O 3 , respectively. Na was derived from albitite, and the formation of Cr-bearing acmite (kosmochlor) and Na-amphibole (richterite) appears to have been related to the release of Cr into the fluid phase by the breakdown of chromite in ultramafic rocks during prograde skarn formation. K-feldspar K–Ar dating yields an age of 50.3 ± 1.7 Ma for the prograde garnet skarn. The related Gadaeri granite exhibits a high-K calc-alkaline signature and a weakly metaluminous to peraluminous I-type affinity with a total alkalinity (Na 2 O + K 2 O) of 8.5–8.8 wt%. The Gadaeri granite shows an enriched REE pattern compared with albitite, as well as negative Eu anomalies, which together with the K/Rb values (200–500) are suggestive of a highly evolved magma from a continental-margin setting.

Original languageEnglish
Pages (from-to)537-550
Number of pages14
JournalOre Geology Reviews
Publication statusPublished - 2019 Feb

Bibliographical note

Funding Information:
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1D1A3B03931481). This study is supported by the Korea Meteorological Administration Research and Development Program (KMI2017-9090 for I.-C. Ryu). We thank anonymous reviewers for the critical review and comments.

Publisher Copyright:
© 2019 Elsevier B.V.


  • Albitite
  • Korea
  • Kosmochlor
  • Na–Ca skarn
  • Ulsan Fe–W skarn deposit
  • Ultramafic skarn

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology
  • Economic Geology


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