The Kokchetav subduction-collision zone (KSCZ) hosting ultrahigh- and high-pressure (UHP-HP) rocks underwent the multistage Vendian-Early Ordovician geodynamic evolution. The subduction of the Paleoasian oceanic lithosphere bearing blocks of continental crust and the collision of the Kokchetav microcontinent with the Vendian-Cambrian island-arc system ultimately led to the formation and exhumation of UHP-HP rocks. In the Vendian-Early Cambrian the margin of the Kokchetav microcontinent deeply subsided into the subduction zone (150–200 km), which led to UHP-HP metamorphism (the maximum at about 535 Ma) and to partial melting of its rocks. In next stage (535–528 Ma), the generated acidic melts including blocks of UHP-HP rocks quickly, at a rate of 1 m/year, ascended to depths of 90 km for 1 Myr. During subsequent 5 Myr, the UHP-HP rocks ascending at a rate of 0.6–1 cm/year reached the base of the accretionary prism (depths of 60–30 km). Then, in the period from 528 to 500 Ma, the UHP-HP rocks ascended along the faulting structures of the lower crust as a result of jamming the subduction zone by the Kokchetav microcontinent. During the period from 500 to 480 Ma, the UHP-HP rocks became part of the upper crust. This process led to the KSCZ, which comprises terranes of the Vendian-Early Arenigian subduction zone occurring at different depths, separated by zones of garnet-mica and mica schists, blastomylonites and mylonites. In the same period there was a jump of subduction zone, which led to the formation of the Ordovician Stepnyak island arc. As a result of the Late Arenigian-Early Caradocian microcontinent-island arc collisions (480–460 Ma), the KSCZ overrided upon the fore-arc trough of the Stepnyak island arc to form a thick accretion-collision orogen, which having experienced anatectic melting was intruded by collisional granites of the Zerenda complex 460–440 Ma in age.

Vesuvianite-group minerals (VGM) are widespread and occur in different geological formations including regional metamorphic rocks, skarns, rodingites, etc. Specific crystal-chemical features of these minerals reflect conditions of their crystallization. As a rule, high-temperature VGM have high-symmetry structures (space group P4/ nnc), whereas low-temperature samples are characterized by the symmetry P4/n or P4nc (Allen and Burnham 1992).

Many geologists, particularly those in industry, have commented adversely on the adequacy of university geology courses as a realistic precursor to a vocational career in any branch of the earth sciences other than in the universities themselves. This volume, among other things, is evidence that university staff are concerned about this situation and are introducing the reality, stringency and urgency of industry into areas where, until recently, they have been absent or poorly represented. In this context the study of volcanic processes belongs almost entirely to academics, whereas ore genesis, although a fascinating intellectual subiect, is of prime concern to the mining industry.

Production of this book has depended on generous financial support from sponsors of the Key Centre for Ore Deposit and Exploration Studies, in particular, the Tasmanian Department of «Mines, Aberfoyle Resources, ВНР Exploration, CRA Exploration, Geopeko, Pancontinental, Pasminco, RGC Exploration and Western Mining Corporation.

Although the material presented comes principally from the collections of J.McP and RLA. we made use of some thin-sections, hand specimens and photographs contributed by colleagues: Stephen Abborr, Guillermo Alvarado. David Cooke. Keith Corbea, Bruce Gemmell. Bruce Houghton, John Waters, Matthew While and Colin Wilson. We are further indebted tо Aberfoyle Resources and Pasminco for usc of many sample from drillcore stores at Hellyer and Rosebery.

Professor Ross large initiated the projecr and provided much appreciated cncouragement throughout irs realisation. The first draft was substantially revised after reviews by Stuart Bull and Ross Large (CODES); Fergus Fitzgerald (Pasminco Exploration), Malcolm Howells (British Geological Survey/, Noel White (ВНР) and Hiromitsu Yamagishi (Geological Survey of Hokkaido).

The production team included June Pongratz (design and desktop publishing), Jcancttc I lankin and Kirst)' Whalcy (typing!- Debbie Flardmg (draughting). Simon Stephens and Naomi Dcards (thin-section and slab preparation). Fred Koolhof (technical advice and some photography) and Alison Jones (final editing).