Journal of the Mineralogical Society of Korea (한국광물학회지)

The Mineralogical Society of Korea (한국광물학회)
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Gahnite-Sillimanite-Garnet Mineral Assemblage from the Host Rocks of the Cannington Deposit, North Queensland, Australia: Relationship between Metamorphism and Zn-Mineralization

호주 퀸즈랜드 주 캔닝턴 광상 모암의 아연-첨정석-규선석-석류석에 관한 연구 :변성작용과 아연-광화작용에 대해서

  • 김형수 (강원도 춘천시 강원대학교 지질학과)
  • Published : 2004.12.01
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Abstract

The Cannington Ag-Pb-Zn deposit, northwest Queensland, Australia developed around the host rocks composing banded and migmatitic gneisses, sillimanite-garnet schist and amphibolite. Three crystal habits of sillimanite, gahnite (Zn-spinel) and garnet porphyroblasts occurred on the host rocks of the Cannington deposit could be used to delineate metamorphism that closely associated with Zn-mineralization in the deposit. Linkages the metamorphism to Zinc-mineralization is determined in four chemical systems, KFMASH (K$_2$O-FeO-MgO-Al$_2$O$_3$-SiO$_2$-$H_2O$), KFMASHTO (K$_2$O-FeO-MgO-Al$_2$O$_3$-SiO$_2$-$H_2O$-TiO$_2$-Fe$_2$O$_3$), NCKFMASH (Na$_2$O-CaO-K$_2$O-FeO-MgO-AlO$_3$-SiO$_2$-$H_2O$) and MnNCK-FMASH (MnO-Na$_2$O-CaO-K$_2$O-FeO-MgO-AlO$_3$-SiO$_2$-$H_2O$), using THERMOCALC program (version 3.1; Powell and Holland 1988). Partial melting in MnNCKFMASH and NCKFMASH systems occurs at lower temperature than in the KFMASH and KFMASHTO systems. The partial melting temperature decreases with increasing of Na/(Na+Ca+K) of the bulk rock compositions in the MnNCKFMASH system. The host rocks have melted ca 15 vol.% in the MnNCKFMASH system at peak metamorphic conditions (634$\pm$62$^{\circ}C$ and 4.8$\pm$1.3 kbar), but partial melting have not occurred in KFMASHTO system. Based on calculations of sillimanite isograd in different systems and sillimanite modal pro-portion, prismatic and rhombic sillimanite and gahnite porphyroblasts including prismatic sillimanite inclusion probably have resulted from pressure and temperature increasing through partial melting (from 550～$600^{\circ}C$, 2.0～3.0 kbar to 700～75$0^{\circ}C$, 5.0～7.0 kbar), furthermore have experienced N-S then W-E crustal shortening during D$_1$ and D$_2$ deformation. Consequently, Zinc mineralization related to gahnite growth occurred during D$_2$ and was redistributed and upgraded by partial melting and retrograde metamorphism into structural and rheological sites during shearing in D$_3$.

연구는 호주 퀸즈랜드 주 북서부에 위치하는 은-납-아연 캔닝턴 광상은 호상편마암, 미그마타이트, 규선석-석류석 편암 그리고 각섬암으로 구성된 모암 주변부에서 발달해 있다. 모암에서 산출되는 규선석의 세 가지 다른 결정형태, 규선석을 포획광물로 함유한 아연-첨정석과 석류석 반상변정은 모암의 변성작용과 아연과 관련된 광화작용에 대한 지질학적 지시자로 사용되었다. 변성작용과 아연 광화작용과의 관계는 프로그램 THERMOCALC를 이용하여 KFMASH (K$_2$O-FeO-MgO-A1$_2$O$_3$-SiO$_2$- $H_2O$), KFMASHTO (K$_2$O-FeO-MgO-A1$_2$O$_3$-SiO$_2$-$H_2O$-TiO$_2$-Fe$_2$O$_3$), NCKFMASH ($Na_2$O-CaO-K$_2$O-FeO-MgO-Al$_2$O$_3$-SiO$_2$-$H_2O$) 그리고 MnNCKFMASH (MnO-$Na_2$O-CaO-K$_2$O-FeO-MgO-Al$_2$O$_3$-SiO$_2$-$H_2O$) 화학계에서 이들 세 가지 광물의 공생관계와 규선석-석류석-부분용융의 상평형 관계를 이용하여 결정하였다. MnNCKFMASH와 NCKFMASH계에서 부분 용융은 KFMASH와 KFMASHTO계에서 보다 낮은 온도에서 일어나며, MnNCKFMASH 계에서 용융 온도는 암석 화학 성분의 Na+Ca+K)의 비가 증가함에 따라 감소하는 경향을 보인다. 캔닝턴 광상의 모암은 MnNCKFMASH계의 경우 최고 온도와 압력 환경에서(634$\pm$62$^{\circ}C$, 4.8$\pm$1.3 kbar) 약 15% 용융되지만, KFMASHTO계하에서는 부분 용융이 일어나지 않는다. 규선석의 등변성도선과 모드 비의 변화를 근거로, 주상과 능면형의 규선석과 주상의 규선석을 포획하는 아연-첨정석 반상변정은 부분 용융을 포함하는 온도와 압력의 증가(약 550～$600^{\circ}C$, 2.0～3.0 kbar에서 700～75$0^{\circ}C$, 5.0～7.0 kbar)로 인한 것으로 생각된다. 또한 이와 같은 변성작용 동안의 최대 수축 변형 방향은 남-북 그 다음 동서 방향으로 주로 D$_1$과 D$_2$ 변형작용 동안에 형성되어졌다. 결론적으로 아연-첨정석의 성장과 관련된 아연 광화 작용은 D$_2$ 동안에 일어났고 그 후 부분 용융과 후기 변형/변성작용에 의해 재배치 또는 재농집 되어진 것으로 생각된다.

Keywords

References

  1. Beardsmore, T.J., Newbery, S.P., and Laing, W.P. (1988) The Maronan Supergroup - An inferred early volcanosedimentary rift sequence in the Mt lsa Inlier, and its implications for ensialic rifting in the middle Proterozoic of northwest Queensland. Precam. Res., 40, 487-508.
  2. Bell, T.H., Forde, A., and Wang, J. (1995) A new indicator of movement direction during orogenesis: measurement technique and application to the Alps. Tcrra Nova, 7, 500-508.
  3. Bell, T.H., Hickey, K.A., and Upton, G.J.G. (1998) Distinguishing and correlating multiple phases of metamorphism across a multiply deformed region using the axes of spiral, staircase and sigmoidally curvcd inclusion trails in garnet. Jour. Meta. Geol., 16, 767-794.
  4. Chapman, L.H. and Williarns, P.J. (1998) Evolution of pyroxene-pyroxenoid-garnet alteration at the Cannington Ag-Pb-Zn deposit, Cloneurry district, Queensland, Australia. Econ. Geol., 93, 1390-1405.
  5. Cihan, M. (2004) The drawbacks of sectioning rocks relative to fabric orientations in the matrix: A case study from the Robertson River Metamorphics (Northern Queensland, Australia). Jour. Struc. Geol., 26, 2157-2174.
  6. Giles, D. (2000) Geodynamic setting of Broken Hill Type Mineralisation: the Cannington perspective, unpublished PhD thesis, Monash University, 233 p.
  7. Gray, D.R. (1994) Structural report on the Cannington Pb-An-Ag deposit, Mount Isa Inlier. Unpublished RepOlt to BHP Minerals.
  8. Hill, E.J., Loosveld, R.J.H., and Page, R.W. (1992) Structure and geochronology of the Tommy Creek Block, Mount Isa Inlier. In: Stewart A.J. and Blake D.H. (eds.), Australian Geol. Survey Organisation, Bull., 243, 329-348.
  9. Kim, H.S. (2001) A new approach to distinguishing multiple phases of metamorphism and deformation: Application to the Northeastern Appalachian. Geo. Jour., 5, 65-84.
  10. Kim H.S. and Bell T.H. (2004) Combining compositional zoning and foliation interseetion axes (FIAs) in garnet to quantitatively determine early P-T-t paths in multiply deformed and metamorphosed schist: north central Massachusetts, USA. Contri. Mineral. Petrol., in press.
  11. Kretz, R. (1983) Symbols for rock-fonning minerals. Amer. Mineral., 68, 277-279.
  12. Loosveld, R.J.H. (1989) The synchronism of crustal thickening and high T/low P metamorphism in the MOWIt Isa Inlier, Australia: An example, the central Soldiers Cap belt. Tectono., 158, 173-190.
  13. Mark, G.M. (1993) Pegmatite and partial melting at thc Cannington deposit. Unpublished BSc. Honours thesis, Townsville, JanIes Cook University, 131 p.
  14. Mark, G.M., Philipd, G.N., and Pollard, PJ. (1998) Highly selective pmtial melting of pelitic gneiss at Cannington, (loncurry District, Quccnsland. Austr. Jour. Earth Sci., 45, 169-176.
  15. McLelland, J., Goldstein, A., Cunnungham, B., Olson, C., and Orrell, S. (2002) Structural evolution of quartz-sillimanitc vein and nodule complex in a late-to post-tectonic leucogranite, Western Adirondack Highlands, New York. Jour. Struc. GeoL, 24, 1157-1170.
  16. Musumeci, G. (2002) Sillimanite-bearing shear zones in syntcctonic lcucogranitc: fluid-assitcd brittle-ductile defonnation under amphibolite fades conditions. Jour. Struc. Geol., 24, 1491-1505.
  17. Newberry, S.P. (1990) The middle of Proterozoic Maranoan Supcrgroup, Soldiers Cap Belt, Eastern Mount Isa Inliner; A rationalization of the geology and mineralization of a complexly defonued and metamorphosed ten'ane. Ph.D. thesis, Jmnes Cook University.
  18. Parr, J.M. and P1imer, J.R. (1993) Model for Broken Hill-type lead-zinc-silver deposits, in Kirkham, R.V, Sinclair, W.D., Thorpe, R.I., and Duke, J.M., eds., Mineral Deposit Modeling, Geological Association of Canada Special Paper, 40. 778-790.
  19. Powell R. and Holland, T.J.B. (1988) An internally consistent dataset with uncertainties and correlation; 3, Applications to geobarometry, worked examples and a computcr program. Jour. Meta. Geol., 6, 173-204.
  20. Powell R., Holland T.J.B., and Worley B. (1998) Calculating phase diagrams involving solid solutions via non-linear equations, with examples using TIIERMOCALC. Jour. Meta. Geol., 16, 577-588.
  21. Richmond, J.M., Chapman, L.H., and Williams, P.J. (1996) Two phases of gamet alteration at the Cannington Ag-Pb-Zn deposit, NW Qeenslamd: Jamnes Cook Univcrsity of North Qccnsland Economic Geology Research Unit, Contribution 55. 113-117.
  22. Roache, T.J. (2004) Shear zone versus fold geometries at the Cannington Ag-Pb-Zn deposit: implications for the genesis of BHT deposit. Jour. Struc. Geol., 26, 1215-1230.
  23. Rubenach, M.J. and Barker, A.J. (1998) Metamorphic and metasomatic evolution of the Snake Creek Anticline, Eastern Succession, Mount Isa Inlier. Australian Journal Earth Sciences, 45, 363-372.
  24. Waltcrs, S.G. (1998) Brokcn Hill-type deposit. AGSO Journal of Australian Geology and Geophysics. 17, 229-237.
  25. Walters, S.G. and Bailey, A. (1998) Geology and mineralization of the Cannington Ag-Pb-Zn deposit: an example of Broken Hill-type mineralization in the Eastem succession, Mount Isa Inlier. Econ. Geol., 93, 1307-1329.
  26. White, R.W., Powell, R., and Clarke, G.L. (2002) The interpretation of reaction textures in Fe-rich metapelitic granulite of the Musgrave Block, central Australia: constraints from mineral equilibria calculations in the system $K_2O\;FeO\;MgO – Ah_2O_3 – SiO_2 – H_2O – TiO_2 – Fe_2O_3$. Jour. Meta. Geol., 20, 41-55.
  27. White, R.W., Powell, R., and Ilolland, T.J.B. (2001) Calculation of partial melting equilibria in the system $Na_2O\; CaO – K_2O\; FeO MgO – Al_2O_3 – SiO_2 – H_2O$ (NCKFMASH). Jour. Meta. Geol., 19, 139-154.
  28. White, R.W., Powell, R., Holland, T.J.B., and Worley, B.A. (2000) The elIecl or $TiO_2$, and $Fe_2O_3$ on metapelitic assemblages at greenschist to amphibolites facics conditions: mineral equilibria calculations in the system $K_2O\;FeO\;MgO – Ah_2O_3 – SiO_2 – H_2O – TiO_2 – Fe_2O_3$. Jour. Meta. Geol., 18, 497-511.
  29. Williams, P.J., Chapman, L.H., Richmond, I., Baker, T., Ileinemann, M., and Prendergast, W.J. (1996). Significance of Late Orogenic Metasomatism in the Broken Hill-Type deposits of the Cloncurry District, NW Queensland. In, Pongratz, J. and Davidson, G..I., eds., New Developments in Broken Hill Type deposits. CODES Special Publication 1, Centre for Ore Deposit and Exploration Studies, Hobart, 119-132.