Geodynamically indicated targeting strategy for shale-hosted massive sulfide Pb-Zn-Ag mineralisation in the Western Fold Belt, Mt Isa terrane

Australian Journal of Earth Sciences

Volumn 49, Issue 6, 2002, Pages 985-1010

  Betts, P G ^a   Lister, G S ^a  

^a MONASH UNIVERSITY   (Australia)

Author keywords

Extension faults; Intracontinental basins; Lead; Massive sulfide deposits; Mt Isa; Silver; Zinc

Indexed keywords

EXTENSIONAL TECTONICS; INTRACRATONIC BASIN; MASSIVE SULFIDE; METALLOGENESIS; MINERALIZATION; ORE DEPOSIT; PROTEROZOIC;

AUSTRALIA;

EID: 0036917004     PISSN: 08120099     EISSN: None     Source Type: Journal    
DOI: 10.1046/j.1440-0952.2002.00965.x     Document Type: Article

References (96)

1. AMES C. 1995. Integrated three dimensional structural and geophysical modelling of the Isa Valley, Queensland, Australia. MSc thesis, Monash University, Melbourne (unpubl.).
2. ANDREWS S. J. 1998. Stratigraphy and depositional setting of the upper McNamara Group, Lawn Hills region, Northwest Queensland. Economic Geology 93, 1132-1152.
3. BAIN J. H. C., HEINRICH C. A. & HENDERSON G. A. M. 1992. Stratigraphy, structure and metasomatism of the Haslingden Group, East Moondarra area, Mount Isa: a deformed and mineralised Proterozoic multi-stage rift-sag sequence. In: Stewart A. J. & Blake D. H. eds. Detailed Studies of the Mount Isa Inlier, pp. 125-136. Australian Geological Survey Organisation Bulletin 243.
4. BATSON R. 1991. Stratigraphy and structure of the southern Myally Block, Mount Isa Inlier, Queensland. MSc thesis, Monash University, Melbourne (unpubl.).
5. BELL T. H. 1983. Thrusting and duplex formation at Mount Isa, Queensland, Australia. Nature 304, 493-497.
6. BETTS P. G. 1997. The Mount Isa Rift Event: an example of Middle Proterozoic intracontinental extension. PhD thesis, Monash University, Melbourne (unpubl.).
7. BETTS P. G. 1999. Palaeoproterozoic mid-basin inversion in the northern Mt Isa terrane, Queensland. Australian Journal of Earth Sciences 46, 735-748.
8. BETTS P. G. 2001. Three-dimensional structure along the inverted Palaeoproterozoic Fiery Creek Fault system, Mount Isa terrane, Australia. Journal of Structural Geology 23, 1953-1969.
9. BETTS P. G., AILLÈRES L., GILES D. & HOUGH M. 2000. Deformation history of the Hampden Synform in the Eastern Fold Belt of the Mt Isa terrane. Australian Journal of Earth Sciences 47, 1113-1125.
10. BETTS P. G. & GILES D. 2000. 1.8 to 1.1 Ga Evolution of the Australian Continent: a northern, central and eastern Australian perspective. Geological Society of Australia Abstracts 59, 34.
11. BETTS P. G. & LISTER G. S. 2001. Comparison of the 'strike-slip' versus the 'episodic rift-sag' models for the origin of the Isa Superbasin. Australian Journal of Earth Sciences 48, 265-280.
12. BETTS P. G., LISTER G. S. & O'DEA M. G. 1998. Asymmetric extension of the Middle Proterozoic lithosphere, Mount Isa terrane, Queensland, Australia. Tectonophysics 296, 293-316.
13. BETTS P. G., LISTER G. S. & POUND K. S. 1999. Architecture of a Palaeoproterozoic rift system: evidence from the Fiery Creek Dome region, Mt Isa terrane. Australian Journal of Earth Sciences 46, 533-554.
14. BLAKE D. H. 1987. Geology of the Mount Isa Inlier and environs, Queensland and Northern Territory. Bureau of Mineral Resources Bulletin 225.
15. BLAKE D. H. & STEWART A. J. 1992. Stratigraphic and tectonic framework, Mount Isa Inlier. In: Stewart A. J. & Blake D. H. eds. Detailed Studies of the Mount Isa Inlier, pp. 1-11. Australian Geological Survey Organisation Bulletin 243.
16. BROADBENT G. C., MYERS R. E. & WRIGHT J. V. 1998. Geology and origin of shale-hosted Zn-Pb-Ag mineralization at the Century Deposit, Northwest Queensland, Australia. Economic Geology 93, 1264-1294.
17. BULL S. W. 1998. Sedimentology of the Palaeoproterozoic Barney Creek Formation in DDH BMR McArthur 2, southern McArthur Basin, Northern Territory. Australian Journal of Earth Sciences 45, 21-31.
18. BULL S. W. & ROGERS J. R. 1996. Recognition and significance of an early compressional deformational event in the Tawallah Group, McArthur Basin, NT. In: Baker T., Rotherham J., Richmond J., Mark G. & Williams P. eds. New Developments in Metallogenic Research: the Mcarthur, Mount Isa, Cloncurry Minerals Province. pp. 28-32. James Cook University, Economic Geology Research Unit Contribution 55.
19. CARR G. R. 1981. The mineralogy, petrology and geochemistry of the zinc-lead-silver ores and host sedimentary rocks at Lady Loretta, northwest Queensland. PhD thesis, University of Wollongong, Wollongong (unpubl.).
20. COLLINS W. J. & SHAW R. D. 1995. Geochronological constraints on orogenic events in the Arunta Inlier: a review. Precambrian Research 71, 315-346.
21. COOKE D. R., BULL S. W., LARGE R. R. & MCGOLDRICK P. J. 2000. The importance of oxidized brines for the formation of Australian Proterozoic stratiform sediment-hosted Pb-Zn-Ag (sedex) deposits. Economic Geology 95, 1-17.
22. COWARD M. P. 1986. Heterogeneous stretching and basin development. Earth and Planetary Science Letters 18, 325-336.
23. CUREWITZ D. & KARSON J. A. 1997. Structural settings of hydrothermal outflow: fracture permeability maintained by fault propagation and interaction. Journal of Volcanology and Geothermal Research 79, 149-168.
24. DERRICK G. M. 1982. A Proterozoic rift zone at Mount Isa, Queensland, and implications for mineralisation. BMR Journal of Australian Geology & Geophysics 7, 81-92.
25. DERRICK G. M. 1996. The 'geophysical' approach to metallogeny of the Mt Isa Inlier: what sort of orebody do you want? In: Jones H. ed. Diversity: the Key to Prosperity, pp. 349-366. Australasian Institute of Mining and Metallurgy Publication Series 1/96.
26. DERRICK G. M., WILSON I. H. & SWEET I. P. 1980. The Quilalar and Surprise Creek Formations-new Proterozoic units from the Mount Isa Inlier: their regional sedimentology and application to regional correlation. BMR Journal of Australian Geology & Geophysics 5, 215-223.
27. DUFFETT M. L. 1998. Gravity, magnetic and radiometric evidence for the geological setting of the Lady Loretta Pb-Zn-Ag deposit: a qualitative appraisal. Economic Geology 93, 1295-1306.
28. ELDRIDGE C. S., WILLIAMS N. & WALSHE J. L. 1993. Sulfur isotope variability in sediment-hosted massive sulfide deposits as determined using the ion microprobe SHRIMP: II, A study of the H.Y.C. Deposit at McArthur River, Northern Territory, Australia. Economic Geology 88, 1-26.
29. ERIKSSON K. A., SIMPSON E. L. & JACKSON M. J. 1993. Stratigraphical evolution of a Proterozoic syn-rift to post-rift basin: constraints on nature of lithospheric extension in the Mount Isa Inlier, Australia. In: Frostick L. E. & Steel R. J. eds. Tectonic Controls and Signatures in Sedimentary Successions, pp. 203-221. International Association of Sedimentologists Special Publication 20.
30. ETHERIDGE M. A., RUTLAND R. W. R. & WYBORN L. A. I. 1987. Orogenesis and tectonic process in the Early to Middle Proterozoic of northern Australia. In: Kroner A. ed. Proterozoic Lithosphere Evolution, pp. 131-147. American Geophysical Union Geodynamic Series 1.
31. ETHERIDGE M. A. & WALL V. J. 1994. Tectonic and structural evolution of the Australian Proterozoic. Geological Society of Australia Abstracts 37, 102-103.
32. FLOTTMANN T. & JAMES P. 1999. Influences of basin/basement structures on the development of fold-thrust belts. Geological Society of Australia Abstracts 53, 65.
33. 39Ar thermochronology and post-orogenic events in the Mount Isa Inlier. Australian Crustal Research Centre Technical Publication 46, 37-38.
34. GARVEN G. & FREEZE R. A. 1984. Theoretical analysis of the role of groundwater flow in the genesis of stratabound ore deposits 1: Mathematical and numerical model. American Journal of Science 284, 1084-1124.
35. GILES D. & BETTS P. G. 2000. The Early to Middle Proterozoic configuration of Australia and its implications for Australian-US relations. Geological Society of Australia Abstracts 59, 174.
36. GILES D., BETTS P. G. & LISTER G. S. 2001. A continental back-arc setting for Early to Middle Proterozoic basins of north-eastern Australia. Geological Society of Australia Abstracts 64, 55-56.
37. GOODFELLOW W. D., LYNDON J. W. & TURNER R. J. W. 1993. Geology and genesis of stratiform sediment-hosted (SEDEX) zinc-lead-silver sulphide deposits. In: Kirkham R. V., Sinclair W. D., Thorpe R. I. & Duke J. M. eds. Mineral Deposit Modelling, pp. 201-251. Geological Association of Canada Special Paper 40.
38. HANCOCK M. C. & PURVIS A. H. 1990. Lady Loretta silver-lead-zinc deposit. In: Hughes F. E. ed. Geology of the Mineral Deposits of Australia and Papua New Guinea, pp. 943-948. Australasian Institute of Mining and Metallurgy Monograph Series 14.
39. HOBBS B. E., ORD A., ARCHIBALD N. J., WALSHE J. L., ZHANG Y., BROWN M. & ZHAO C. 2000. Geodynamic modelling as an exploration tool. In: After 2000-the Future of Mining, pp. 34-48. AUSIMM Annual Conference Proceedings 2000.
40. HUTTON L., DERRICK G. M. & GALLAGHER J. 1985. Geology of the Mammoth Mines Region 1:100 000 Geological Series, Sheet 6758. Bureau of Mineral Resources, Canberra.
41. JACKSON M. J., SCOTT D. L. & RAWLINGS D. J. 2000. Stratigraphic framework for the Leichhardt and Calvert Superbasins: review and correlations of the pre-1700 Ma successions between Mt Isa and McArthur River. Australian Journal of Earth Sciences 47, 381-404.
42. JACKSON M. J., SIMPSON E. L. & ERIKSSON K. A. 1990. Facies and sequence stratigraphic analysis in a thermal relaxation basin: the early Proterozoic, lower Quilalar Formation and Ballara Quartzite, Mount Isa Inlier, Australia. Sedimentology 37, 1053-1078.
43. JAQUES A. L., BLAKE D. H. & DONCHAK P. J. T. 1982. Regional metamorphism in the Selwyn Range Area, north west Queensland. BMR Journal of Australian Geology & Geophysics 7, 181-196.
44. KERRICH R. 1986. Fluid infiltration into fault zones: chemical, isotopic, and mechanical effects. Pure and Applied Geophysics 124, 225-268.
45. KRASSAY A. A., BRADSHAW B. E., DOMAGALA J. & JACKSON M. J. 2000a. Siliciclastic shoreline to growth-faulted turbiditic sub-basins: the Proterozoic River Supersequence of the upper McNamara Group on the Lawn Hill Platform, northern Australia. Australian Journal of Earth Sciences 47, 533-562.
46. KRASSAY A. A., DOMAGALA J., BRADSHAW B. E. & SOUTHGATE P. N. 2000b. Lowstand ramps, fans and deep-water Palaeoproterozoic and Mesoproterozoic facies of the Lawn Hill Platform: the Term, Lawn, Wide and Doom Supersequences of the Isa Superbasin, northern Australia. Australian Journal of Earth Sciences 47, 563-598.
47. LARGE D. E. 1983. Sediment-hosted massive sulphide lead-zinc deposits: an empirical model. In: Sangster D. F. ed. Sediment-hosted Lead-Zinc Deposits, pp. 1-30. Mineralogical Association of Canada Short Course Handbook 8.
48. LARGE R. R., BULL S. W., COOKE D. R. & MCGOLDRICK P. J. 1998. A genetic model for the H.Y.C. Deposit, Australia: based on regional sedimentology, geochemistry, and sulfide-sediment relationships. Economic Geology 93, 1345-1368.
49. LARGE R. R., MCGOLDRICK P. J., BERRY R. F. & YOUNG C. H. 1988. A tightly folded, gold-rich, massive sulfide deposit; Que River Mine, Tasmania. Economic Geology 83, 681-693.
50. LEACH D. L. & SANGSTER D. F. 1993. Mississippi valley-type lead-zinc deposits. In: Kirkham R. V., Sinclair W. D., Thorpe R. I. & Duke J. M. eds. Mineral Deposit Modelling, pp. 289-314. Geological Association of Canada Special Paper 40.
51. LEAMAN D. E. 1991. Geophysical constraints on structure and alteration of the Eastern Creek Volcanics, Mt Isa, Queensland. Australian Journal of Earth Sciences 38, 457-472.
52. LEAMAN D. E. 1996. A thick volcanic pile concealed in North Australian Proterozoic basins. Exploration Geophysics 27, 13-20.
53. LISTER G. S. & ETHERIDGE M. A. 1989. Detachment models for the uplift and volcanism in the eastern Highlands. In: Johnson R. W., Knutson J. & Taylor S. R. eds. Intraplate Volcanism in Eastern Australia, pp. 297-313. Cambridge University Press, Cambridge.
54. LISTER G. S., ETHERIDGE M. A. & SYMONDS P. A. 1991. Detachment models for the formation of passive continental margins. Tectonics 10, 1038-1064.
55. LISTER G. S., O'DEA M. G. and SOMAIA I. 1999. A tale of two synclines: rifting, inversion and transpressional popouts at Lake Julius, northwestern Mt Isa terrane, Queensland. Australian Journal of Earth Sciences 46, 233-250.
56. LYDON J. W. 1983. Chemical parameters controlling the origin and deposition of sediment-hosted stratiform lead-zinc deposits. In: Sangster D. F. eds. Sediment-hosted Lead-Zinc Deposits, pp. 175-250. Mineralogical Association of Canada Short Course Handbook 8.
57. MCCONACHIE B. A. & DUNSTER J. N. 1996. Sequence stratigraphy of the Bowthorn Block in the northern Mount Isa Basin, Australia: implications for the base-metal mineralization process. Geology 24,155-158.
58. MACCREADY T., GOLEBY B. R., GONCHAROV A., DRUMMOND B. J. & LISTER G. S. 1998. A framework of overprinting orogens based on interpretation of the Mount Isa deep seismic transect. Economic Geology 93, 1422-1434.
59. MCGOLDRICK P. J. & KEAYS R. R. 1990. Mount Isa copper and lead-zinc-silver ores: coincidence or cogenesis? Economic Geology 285, 641-650.
60. MCLAREN S., SANDIFORD M. & HAND M. 1999. High radiogenic heat-producing granites and metamorphism: an example from the western Mount Isa Inlier, Australia. Geology 27, 679-682.
61. MYERS R. E., CEREMUGA C., CLARK D., MCSKIMMING D., PRICE S., TUESLEY M. & WILKINSON D. 1996. Mount Isa lead-zinc mineralisation- what controversy? In: Baker T., Rotherham J., Richmond J., Mark G. & Williams P. eds. New Developments in Metallogenic Research: the Mcarthur; Mount Isa, Cloncurry Minerals Province, pp. 85-89. James Cook University, Economic Geology Research Unit Contribution 55.
62. NEUDERT M. K. & RUSSELI R. E. 1982. Shallow water and hypersaline features from the middle Proterozoic Mt Isa Sequence. Nature 293, 284-286.
63. NIJMAN W., VAN LOCHEM J. H., SPLIETHOFF H. & FEIJTH J. 1992. Deformation model and sedimentation patterns of the Proterozoic of the Paroo Range, Mount Isa Inlier, Queensland, Australia. In: Stewart A. J. & Blake D. H. eds. Detailed Studies of the Mount Isa Inlier, pp. 29-73. Australian Geological Survey Organisation Bulletin 243.
64. O'DEA M. G. 1996. Geometry and structural evolution of the Leichhardt River Fault Trough, Mount Isa terrain, Australia. PhD thesis, Monash University, Melbourne (unpubl).
65. O'DEA M. G., BETTS P. G., MACCREADY T. & AILLÈRES L. 1997c. Sequential development of a mid-crustal fold-thrust complex in the eastern Mount Isa Inlier, Australia. Australian Crustal Research Centre Technical Publication 47, 1-28.
66. O'DEA M. G. & LISTER G. S. 1995. The role of ductility contrast and basement architecture in the structural evolution of the Crystal Creek Block, Mount Isa Inlier, Australia. Journal of Structural Geology 17, 949-960.
67. O'DEA M. G., LISTER G. S., BETTS P. G. & POUND K. S. 1997b. A shortened intraplate rift system in the Proterozoic Mount Isa terrain, NW Queensland, Australia. Tectonics 16, 425-441.
68. O'DEA M. G., LISTER G. S., MACCREADY T., BETTS P. G., OLIVER N. H. S., POUND K. S., HUANG W. & VALENTA R. K. 1997a. Geodynamic evolution of the Proterozoic Mount Isa Terrain. In: Burg J. P. & Ford M. eds. Orogeny Through Time, pp. 99-122. Geological Society of London Special Publication 121.
69. PAGE R. W. 1983. Timing of superposed volcanism in the Proterozoic Mount Isa Inlier, Australia. Precambrian Research 21, 223-245.
70. PAGE R. W., JACKSON M. J. & KRASSAY A. A. 2000. Constraining sequence stratigraphy in north Australian basins: SHRIMP U-Pb zircon geochronology between Mt Isa and McArthur River. Australian Journal of Earth Sciences 47, 431-460.
71. PAGE R. W. & SUN S-S. 1998. Aspects of geochronology and crustal evolution in the Eastern Fold Belt, Mt Isa Inlier. Australian Journal of Earth Sciences 45, 343-361.
72. PAGE R. W., SUN S-S. & CARR G. 1994. Proterozoic sediment-hosted lead- zinc-silver deposits in northern Australia-U-Pb zircon and Pb isotope studies. Geological Society of Australia Abstracts 37, 334-335.
73. PAGE R. W. & SWEET I. H. 1998. Geochronology of basin phases in the western Mount Isa Inlier, and correlation with the McArthur Basin. Australian Journal of Earth Sciences 45, 219-232.
74. PAINTER M. G. M., HANNAN K. W. & GOLDING S. D. 1996. Sulphur isotopic constraints on the formation of 'fine grained pyrite' at Mount Isa and its relationship to base metal mineralisation. In: Baker T., Rotherham J., Richmond J., Mark G. & Williams P. eds. New Developments in Metallogenic Research: the Mcarthur, Mount Isa, Cloncurry Minerals Province, pp. 99-103. James Cook University, Economic Geology Research Unit Contribution 55.
75. PERKINS W. G. & BELL T. H. 1998. Stratiform replacement lead-zinc deposits: a comparison between Mount Isa, Hilton and McArthur River. Economic Geology 93, 1190-1212.
76. POTMA W. A. 1996. The structure of the Mitakoodi Culmination, Eastern Mount Isa Inlier, Queensland, Australia. MSc thesis, Monash University, Melbourne (unpubl.).
77. ROHRLACH B. D., FU M. & CLARKE J. D. A. 1998. Geological setting, paragenesis and fluid history of the Walford Creek Zn-Pb-Cu-Ag prospect, Mt Isa Basin, Australia. Australian Journal of Earth Sciences 45, 63-81.
78. RUBENACH M. J. 1992. Proterozoic low-pressure/high-temperature metamorphism and an anticlockwise P-T-t path for the Hazeldene area, Mount Isa Inlier, Queensland, Australia. Journal of Metamorphic Geology 10, 333-346.
79. RUBENACH M. J. & BARKER A. J. 1998. Metamorphic and metasomatic evolution of the Snake Creek Anticline, Eastern Succession, Mt Isa Inlier. Australian Journal of Earth Sciences 45, 363-372.
80. RUSSELL M. J., SOLOMON M. & WALSHE J. L. 1981. The genesis of sediment-hosted, exhalative zinc + lead deposits. Mineralium Deposita 16, 113-127.
81. SCOTT D. L., BRADSHAW B. E. & TARLOWSKI C. Z. 1998. The tectonostratigraphic history of the Proterozoic northern Lawn Hill Platform, Australia: an integrated intracontinental basin analysis. Tectonophysics 300, 329-358.
82. SCOTT D. L., RAWLINGS D. J., PAGE R. W., TARLOWSKI C. Z., IDNURM M., JACKSON M. J. & SOUTHGATE P. N. 2000. Basement framework and geodynamic evolution of the Palaeoproterozoic superbasins of north central Australia: an integrated review of geochemical, geochronological and geophysical data. Australian Journal of Earth Sciences 47, 341-380.
83. SIBSON R. H. 1987. Earthquake rupturing as a mineralizing agent in hydrothermal systems. Geology 15, 701-704.
84. SOUTHGATE P. N., BRADSHAW B. E., DOMAGALA J., JACKSON M. J., IDNURM M., KRASSAY A. A., PAGE R. W., SAMI T. T., SCOTT D. L., LINDSAY J. F., MCCONACHIE B. M. & TARLOWSKI C. 2000a. Chronostratigraphic basin framework for Palaeoproterozoic rocks (1730-1575 Ma) in northern Australia and implications for base- metal mineralisation. Australian Journal of Earth Sciences 47, 461-484.
85. SOUTHGATE P. N., SCOTT D. L., SAMI T. T., DOMAGALA J., JACKSON M. J., JAMES N. P. & KYSER T. K. 2000b. Basin shape and sediment architecture in the Gun Supersequence: a strike-slip model for Pb-Zn-Ag ore genesis at Mt Isa. Australian Journal of Earth Sciences 47, 509-532.
86. STEWART A. J. & BLAKE D. H. (Editors) 1992. Detailed studies of the Mount Isa Inlier. Australian Geological Survey Organisation Bulletin 243.
87. SWEET I. P., HUTTON L. J., MIFSUD J. M., STIRZAKER J. F. & RETTER A. J. 1982. Geology of the Lawn Hill Region. 1:100 000 Geological Series, Sheet 6660. Bureau of Mineral Resources, Canberra.
88. WELBON A. I. & BUTLER R. W. H. 1992. Structural analysis in thrust belts developed through rift basins: a view from the western Alps. In: Larsen R. M., Brekke H., Larsen B. T. & Talleraas E. eds. Structural and Tectonic Modelling and its Application to Petroleum Geology, pp. 469-479. Norwegian Petroleum Foundation Special Publication 1.
89. WELLMAN P. 1992. Structure of the Mount Isa region inferred from gravity and magnetic anomalies. In: Stewart A. J. & Blake D. H. eds. Detailed Studies of the Mount Isa Inlier, pp. 15-27. Australian Geological Survey Organisation Bulletin 243.
90. WERNICKE B., SPENCER J. E., BURCHFIEL L. B. C. & GUTH P. L. 1982. Magnitude of crustal extension in the southern Great Basin. Geology 10, 499-502.
91. WILLIAMS G. D., POWELL C. McA. & COOPER M. A. 1989. Geometry and kinematics of inversion tectonics. In: Cooper M. A. & Williams D. G. eds. Inversion Tectonics, pp. 3-15. Geological Society of London Special Publication 44.
92. WILLIAMS N. 1974. Epigenetic processes in the stratiform lead-zinc deposits at Mcarthur River, Northern Territory, Australia. Economic Geology 69, 1188.
93. WINSOR C. N. 1986. Intermittent folding and faulting in the Lake Moondarra area, Mount Isa, Queensland. Australian Journal of Earth Sciences 33, 27-42.
94. WYBORN L. A. I. 1998. Younger ca 1500 Ma granites of the Williams and Naraku Batholiths. Cloncurry District, eastern Mt Isa Inlier: geochemistry, origin, metallogenic significance and exploration indicators. Australian Journal of Earth Sciences 45, 397-411.
95. WYBORN L. A. I., PAGE R. W. & MCCULLOCH M. T. 1988. Petrology, geochronology and isotope geochemistry of the post-1820 Ma granites of the Mount Isa Inlier: mechanism for the generation of Proterozoic anorogenic granites. Precambrian Research 40/41, 509-541.
96. ZHAO J-X. & MCCULLOCH M. T. 1995. Geochemistry and Nd isotopic systematics of granites from the Arunta Inlier, central Australia: implications for Proterozoic crustal evolution. Precambrian Research 71, 265-299.