Deformation Textures in Pyrite from the Vangorda Pb-Zn-Ag Deposit, Yukon, Canada

D. Brown and K. R. McClay
Department of Geology, Royal Holloway, University of London, Egham, Surrey TW20 0EX, U.K.

Abstract: The Vangorda Pb-Zn-Ag orebody is a 7.1 M tonne, polydeformed stratiform massive sulphide deposit in the Anvil mining district, Yukon, Canada. Five sulphide lithofacies have been identified within the desposit with a typical mineralogy of pyrite, sphalerite, galena, and barite. Pyrrhotite-sphalerite-magnetite assembalges are locally developed. Etched polished sections of massive pyrite ores display relict primary depositional pyrite textures such as colloform growth zoning and spheroidal/framboidal features. A wide variety of brittle deformation, ductile deformation, and annealing textures have been identified. Brittle deformation textures include thin zones of intense cataclasis, grain indentation and axial cracking, and grain boundary sliding features. Ductile deformation textures include strong preferred grain shape orientations, dislocation textures, grain boundary migration, dynamic recrystallisation and pressure solution textures. Post deformational annealing has produced grain growth with lobate grain boundaries, 120° triple junctions and idioblastic pyrite porphyroblasts. The distribution of deformation textures within the Vangorda orebody suggests strong strain partitioning along fold limbs and fault/shear zones. It is postulated that focussed fluid flow in these zones had significant effects on the deformation of these pyritic ores.

Keywords: pyrite • deformation • textures • Vangorda deposit • Yukon • Canada

Mineralogical Magazine; March 1993 v. 57; no. 386; p. 55-66; DOI: 10.1180/minmag.1993.057.386.06
© 1993, The Mineralogical Society
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