Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (18) Citing Articles via Google Scholar Google Scholar Articles by Breeding, C. M. Articles by Ague, J. J. Search for Related Content GeoRef GeoRef Citation

Slab-derived fluids and quartz-vein formation in an accretionary prism, Otago Schist, New Zealand

¹ Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, Connecticut 06520-8109, USA

Regional quartz-vein formation and the fluxes, flow paths, and sources of metamorphic fluids were investigated in the Mesozoic accretionary prism of New Zealand by using a new chemical mass-balance analysis of outcrops. Samples were collected at meter or submeter intervals along outcrop-length traverses and combined to obtain average chemical compositions of whole outcrops. Mass-balance analysis used Zr as an immobile reference frame and as a monitor of sedimentary sorting processes. SiO₂-Zr systematics produced by sedimentary processes differ greatly from those caused by metasomatic mass transfer of silica, allowing evaluation of vein-formation mechanisms. Relatively undeformed metasedimentary outcrops of low metamorphic grade (mostly prehnite-pumpellyite facies) are nearly unveined and characterized by sedimentary compositional trends. More deformed outcrops of higher metamorphic grade (mostly greenschist facies) contain 10–30 vol% quartz veins. These outcrops underwent mass addition of externally derived silica into quartz veins, accompanied by addition of Na and removal of K and W. Average silica additions suggest a time-integrated fluid flux of 10⁴–10⁵ m³_(fluid)/m²_(rock) for fluids ascending through the prism. Dehydration of spilitized oceanic crust subducting beneath the prism is the most probable source for this large fluid flux and could also have caused the Na-K metasomatism. The W removed from deep levels of the prism may have been deposited in focused, retrograde Au-W-quartz veins at shallow levels by ascending fluids. Transfer of SiO₂ from subducting slabs into accretionary prisms is a plausible mechanism for long-term bulk silica enrichment of the continents beyond that possible by magmatic differentiation.

Key Words: fluid flow • quartz veins • accretionary prism • Otago Schist • New Zealand • Au-W mineralization

This article has been cited by other articles:

				T. Lyubetskaya and J. J. Ague Modeling the Magnitudes and Directions of Regional Metamorphic Fluid Flow in Collisional Orogens J. Petrology, August 1, 2009; 50(8): 1505 - 1531. [Abstract] [Full Text] [PDF]

				B. W.D. Yardley The role of water in the evolution of the continental crust Journal of the Geological Society, July 1, 2009; 166(4): 585 - 600. [Abstract] [Full Text] [PDF]

				S. Dasgupta, S. Chakraborty, and S. Neogi Petrology of an inverted Barrovian sequence of metapelites in Sikkim Himalaya, India: Constraints on the tectonics of inversion Am J Sci, January 1, 2009; 309(1): 43 - 84. [Abstract] [Full Text] [PDF]

				S. C. Penniston-Dorland and J. M. Ferry Element mobility and scale of mass transport in the formation of quartz veins during regional metamorphism of the Waits River Formation, east-central Vermont American Mineralogist, January 1, 2008; 93(1): 7 - 21. [Abstract] [Full Text] [PDF]

				C. J. Carson and J. J. Ague Early Palaeozoic metasomatism of the Archaean Napier Complex, East Antarctica Geological Society, London, Special Publications, January 1, 2008; 308(1): 283 - 316. [Abstract] [Full Text] [PDF]

				B. A. Wing and J. M. Ferry Magnitude and geometry of reactive fluid flow from direct inversion of spatial patterns of geochemical alteration Am J Sci, May 1, 2007; 307(5): 793 - 832. [Abstract] [Full Text] [PDF]

				I. K. Pitcairn, D. A. H. Teagle, D. Craw, G. R. Olivo, R. Kerrich, and T. S. Brewer Sources of Metals and Fluids in Orogenic Gold Deposits: Insights from the Otago and Alpine Schists, New Zealand Economic Geology, December 1, 2006; 101(8): 1525 - 1546. [Abstract] [Full Text] [PDF]

				S. E. Kesler Ore-Forming Fluids Elements, January 1, 2005; 1(1): 13 - 18. [Abstract] [Full Text] [PDF]

				C. M. Breeding, J. J. Ague, and M. Brocker Fluid-metasedimentary rock interactions in subduction-zone melange: Implications for the chemical composition of arc magmas Geology, December 1, 2004; 32(12): 1041 - 1044. [Abstract] [Full Text] [PDF]

				C. M. Breeding, J. J. Ague, M. Grove, and A. L. Rupke Isotopic and chemical alteration of zircon by metamorphic fluids: U-Pb age depth-profiling of zircon crystals from Barrow's garnet zone, northeast Scotland American Mineralogist, July 1, 2004; 89(7): 1067 - 1077. [Abstract] [Full Text] [PDF]

				J. J. Ague Fluid Infiltration and Transport of Major, Minor, and Trace Elements During Regional Metamorphism of Carbonate Rocks, Wepawaug Schist, Connecticut, USA Am J Sci, November 1, 2003; 303(9): 753 - 816. [Abstract] [Full Text] [PDF]

				N. Mortimer A provisional structural thickness map of the Otago Schist, New Zealand Am J Sci, September 1, 2003; 303(7): 603 - 621. [Abstract] [Full Text] [PDF]