Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
권호 표지
DOI QR코드

DOI QR Code

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

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

  • Kim, Eui-Jun (Korea Institute of Geoscience and Mineral Resources)
  • 김의준 (한국지질자원연구원 광물자원연구본부)
  • Received : 2017.10.09
  • Accepted : 2017.10.30
  • Published : 2017.10.28
Download PDF
⟨ Previous Next ⟩

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 $Fe_2O_3/FeO$ 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.

한반도의 중서부에 위치한 소연평도의 각섬암 내 Fe-Ti 광화작용은 우리나라의 대표적인 정마그마형 Fe-Ti 광상중 하나이다. 각섬암은 북서-남동방향의 선캠브리아기 변성퇴적암류를 평행하게 관입하고 있다. 각섬암의 하부는 장석-우세 우백질과 각섬석-Fe-Ti 산화광물-우세 우흑질 각섬암이 교호하는 화성기원 층상구조(igneous layering)의 발달이 특징이다. 우백질과 우흑질 각섬암은 서로 혼재되어 있거나, 뚜렷한 경계면을 보인다. 반면에 상부 각섬암은 하부 각섬암에 비해 더 복잡한 산상(함석류석 각섬암, 조립질 각섬암, 편상 각섬암)으로 산출되고, 괴상의 Fe-Ti 광체가 우흑질의 편상 각석암과 교호하고 있다. 남북과 동서방향의 단층작용은 상부 각섬암의 Fe-Ti 광체와 하부 각섬암의 층상구조를 각각 변이 시켰다. 우백질과 우흑질 각섬암 및 Fe-Ti 광석의 조성은 각 암상을 구성하고 있는 광물조합을 잘 반영하고 있다. 각섬암은 강한 정(+)의 Eu 이상(anomaly)을 보이나, Fe-Ti 광석은 미약한 음(-)의 Eu 이상을 보이고 있다. 각섬암을 구성하고 있는 장석(안데신-올리고클레이스)과 Fe-Ti 산화광물들은 각섬암 전반에 걸쳐 일정한 조성을 가진다. 반면에 각섬석은 상대적으로 넓은 범위의 조성을 가지나, 화학적 분화특성을 반영하지는 않는다. 하부 각섬암 내 화성기원 층상구조는 단일 층상구조 내 혹은 층상구조 간 광물조성 변화가 관찰되지 않는다. 이것은 심부에서 지속적인 새 마그마의 공급이나 주변암과의 동화작용에 의해 Fe가 공급되지 않았음을 지시한다. 각섬암과 Fe-Ti 광석의 상반된 Eu 이상은 각섬암의 초기 분별정출작용 동안 사장석의 정출에 의해 잔류 유체 내 Fe의 부화가 진행되었을 가능성을 지시한다. 따라서 각섬암의 후기 분별정출작용 단계에서 Fe-부화 잔류 유체는 유체 주입(filter pressing)에 의해 상부 각섬암 내로 상승 및 층상의 괴상 Fe-Ti 광화작용을 야기한 것으로 간주된다.

Keywords

References

  1. Bai, Z.J., Aiiong, H., Naldrett, A.J., Ziiu, W.G. and Xu, G.W. (2012) Whole-rock and mineral composition constraints on the genesis of the Giant Hongge Fe-Ti-V oxide deposit in the Emeishan large igneous province, Southwest China. Econ. Geol., v.107, p.507-524. https://doi.org/10.2113/econgeo.107.3.507
  2. Barbey, P. (2009) Layering and schlieren in granitoids: a record of interactions between magma emplacement, crystallization, and deformation in growing plutons. Geol. Gelg., v.12, p.109-133.
  3. Cawthorn, R.G. and Ashwal, L.D. (2009) Origin of anorthosite and magnetite layers in the Bushveld complex, constrained by major element compositions of plagioclase. J. Petrol., v.50, p.1607-1637. https://doi.org/10.1093/petrology/egp042
  4. Chang, H.W., Yum, B.W. and Park, N.Y. (1987) Petrochemical study on the alkaline gabbroic host rocks of titaniferous magnetite deposits in Gonamsan, Yeoncheon-Gun, South Korea. J. Korean Inst. Mining Geol., v.20, p.85-95.
  5. Charlier, B., Namur, O., Toplis, M.J., Schiano, P., Cluzel, N., Higgins, M.D. and Vanver Auwera, J. (2011) Largescale silicate liquid immiscibility during differentiation of tholeiitic basalt to granite and the origin of the Daly gap. Geology, v.39, p.907-910. https://doi.org/10.1130/G32091.1
  6. Das, S.K. and Mukherjee, S. (2001) Mineralogy geochemistry of V-Ti magnetite deposits of Mayurbhanj basic igneous complex, Orisssa. Indian Mineralogist, v.35, p.134-150.
  7. Hodson, M.E. (1998) The origin of igneous layering in the Nunarssuit Syenite, South Greenland. Mineral. Mag., v.62, p.9-27. https://doi.org/10.1180/002646198547431
  8. Irvine, T.N. (1975) Crystallization sequences in the Muskox intrusion and other layered intrusions-II. Origin of chromitite layers and similar deposits of other magmatic ores. Geochim Cosmochim Acta, v.39, p.991-1020. https://doi.org/10.1016/0016-7037(75)90043-5
  9. Irvine, T.N., Andersen, J.C.O. and Brooks, C.K. (1998) Included blocks (and blocks within blocks) in the Skaergaard intrusion: geologic relations and the origins of rhythmic modally graded layers. Geol. Soc. Am. Bull., v.110, p.1398-1447. https://doi.org/10.1130/0016-7606(1998)110<1398:IBABWB>2.3.CO;2
  10. Kim, K.H. and Hwang, S.J. (2000) Mineralogical and geochemical studies of titaniferous iron ores and ultramafic to mafic rocks from the Boreumdo iron ore deposits, South Korea. Econ. Environ. Geol., v.33, p.1-18.
  11. Kim, K.H. and Lee, J.E. (1994) Petochemisty of the Soyeonpyeong titaniferous iron ore deposits, South Korea. Econ. Environ. Geol., v.27, p.345-362.
  12. Klemm, D.D., Henckel, J., Dehm, R. and Von Gruenewaldt, G. (1985) The geochemistry of titanomagnetite in magnetite layers and their host rocks of the Eastern Bushveld complex. Econ. Geol., v.80, p.1075-1088. https://doi.org/10.2113/gsecongeo.80.4.1075
  13. Leake, B.E. (1978) Nomenclature of amphiboles. American Mineralogists, v.63, p.1023-1058.
  14. Lee, C.H. and Lee, S.H. (1989) Petrological studies on the genesis of the Hongcheon iron deposits, Korea. J. Geol. Soc. Korea, v.25, p.239-258.
  15. Lee, I.G., Jun, Y. and Choi, S.H. (2017) Ore mineralization of the Hadong Fe-Ti-bearing ore bodies in the Hadong-Sancheong anorthosite complex. Econ. Environ. Geol., v.50, p.35-44. https://doi.org/10.9719/EEG.2017.50.1.35
  16. Lee, J.H., Park, N.Y. and Oh, I.S. (1965) Report on the Soyeonpyong-do titaniferous magnetite deposits. Technical report on geological survey 8, Korea Institute of Geoscience and Mineral Resources, p.5-40.
  17. Lister, G.F. (1966) The composition and origin of selected iron-titanium deposits. Econ. Geol., v.61, p.275-310. https://doi.org/10.2113/gsecongeo.61.2.275
  18. Naslund, H.R. and McBirney, A.R. (1996) Mechanism of formation of igneous layering. In: Cawthorn RG (ed.) Layered intrusions. Elsevier, Amsterdam, pp.1-43.
  19. Pang, K.N., Zhou, M.F., Lindsley, D., Zhao, D. and Malpas, J. (2008) Origin of Fe-Ti oxide ores in mafic intrusions: evidence from the Panzhihua intrusion, SW China. J. Petrol., v.49, p.295-313.
  20. Parsons, I. (1979) The Klokken gabbro-syenite complex, South Greenland: cryptic variation and origin of inversely-graded layering. J. Petrol., v.20, p.653-694. https://doi.org/10.1093/petrology/20.4.653
  21. Reynolds, I. (1985) The nature and origin of titaniferous magnetite-rich layers in the upper zone of the Bushveld complex: a review and synthesis. Econ. Geol., v.80, p.1089-1108. https://doi.org/10.2113/gsecongeo.80.4.1089
  22. So, C.S. (1977) Origin of the strata-bound magnetite ore from the Pocheon iron mine, Korea. J. Korean Inst. Mining Geol., v.13, p.249-262.
  23. So, C.S., Kim, S.M. and Son, D.S. (1975) Origin of the magnetite-bearing amphibolite from the Yangyang iron mine, Korea: New geochemical data and interpretation. J. Korean Inst. Mining Geol., v.8, p.175-182.
  24. Wager, L.R. and Brown, G.M. (1968) Layered Igneous Rock. Oliver and Boyd, Edingurgh, p. 588.
  25. Zhou, M.F., Robinson, P.T., Leshcer, C.M., Keays, R.R., Zhang, C.J. and Malpas, J. (2005) Geochemistry, petrogenesis, and metallogenesis of the Panzhihua gabbroic layered intrusion and associated Fe-Ti-V oxide deposits, Sichuan province, SW China. J. Petrol., v.46, p.2253-2280. https://doi.org/10.1093/petrology/egi054