Major late Paleozoic faults, many with documented strike-slip motion, have dissected the Ordovician-Devonian Appalachian orogen in the Maritime Provinces of Atlantic Canada. Activity alternated between east-west faults (Minas trend) and NE-SW faults (Appalachian trend). NW-SE faults (Canso trend) were probably conjugate to Minas-trend faults. Major dextral movement, on faults with Appalachian trend, in total between 200 and 300 km, began in the Late Devonian. This movement initiated the Maritimes Basin in a transtensional environment at a releasing bend formed around a promontory in the Laurentian margin and thinned the crust, accounting for the major subsidence of the basin. Appalachian-trend strike slip continued in the Mississippian but was accompanied by major movement on E-W Minas-trend faults culminating around the Mississippian-Pennsylvanian boundary, juxtaposing the Meguma and Avalon terranes of the Appalachians close to their present-day configuration. However, strike slip continued during the Pennsylvanian-Permian interval resulting in transpressional deformation that reactivated and inverted earlier extensional faults. A final major episode of transtension, mainly sinistral, occurred during the Mesozoic opening of the Atlantic Ocean. Restoration of movements on these faults, amounting to several hundred kilometers of slip, explains anomalies in the present-day distribution of terranes amalgamated during early Paleozoic Appalachian tectonism. In the restored geometry, the Nashoba and Ellsworth terranes of Ganderia are adjacent to one another, and the Meguma terrane lies clearly outboard of Avalonia. A restored post-Acadian paleogeography, not the present-day geometry of the orogen, should be used as a basis for reconstructions of its earlier Paleozoic history.

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Charnockite and homophanous leptynite are two quartz–feldspar neosomes in the late Archaean granulite-migmatite Eastern Ghats terrane of Orissa, India. Three phases of deformation and metamorphism are recognised to have preceded a late phase, or phases in which deformation was not intense. An early granulite facies event (D1–M1) produced basic granulites and khondalite (sillimanite-garnet aluminous paragneiss). A second event (D2–M2) involved some retrogression but temperatures and pressures remained high (possibly c. 750°C—>5 kb). D3–M3 was associated with the development of open folds (F3) with axial planar shear zones in pinched antiforms; temperatures and pressures were also falling (c. 650°C— 4kb), but the shear zones acted as a control on the development of firstly homophanous leptynite, and secondly charnockite. In both cases, neosomes of quartz and potassium feldspar have myrmekitic textures and intergranular occurrence. The palaeosome became strained and garnet–biotite and garnet–biotite–clinopyroxene ± orthopyroxene mineral assemblages were formed in association with the development, respectively, of homophanous leptynite and charnockite. The persistence of straining in the palaeosome and the presence of poikilitic textures indicate that this typical assemblage does not represent one in thermodynamic equilibrium. This has important consequences for geothermobarometry.The structural control on neosome development reflects a regional characteristic where shear zones are the site of peralkaline plutons, fenitisation, carbonatites and epigenetic graphite development. The peculiar features of charnockite are seen as just one of several aspects related to the fluxing of hot CO2-dominated fluids from either the deep crust or mantle during the late Archaean development of the Indian craton.

Serpentinites are a major component in a distinctive suite of metasedimentary and metamorphosed igneous rocks, the Outokumpu association, in the early–middle Proterozoic Svecokarelides of eastern Finland. Like the adjacent mica schists and associated supracrustal rocks, they show the effects of at least six phases of deformation (D1–D6). The tectonic history began with the emplacement of the Outokumpunappe (pre-D1), but a study of relict assemblages in the serpentinites and theirenvelope rocks reveals evidence for a complex pre-nappe history involving ultramaficmagmatism with extensive high-temperature hornfels development, and low-temperature serpentinisation contributing to sea-floor exhalation of sulphide ores.The serpentinites subsequently underwent recrystallisation during several phases of regional metamorphism giving rise to mineral fabrics, including a pressure-solution initiated segregation (M1–D1), anthophyllite growth during the thermal climax (D2–M2—600–680°C, 2·5–4 kb), and steatitisation (D2c–M2c). Steatitisation is structurally controlled, occurring where serpentinite bodies impinge upon localised shear zones (wrench faults—D2c). Talc–carbonate–brucite assemblages reflect the influx of CO2 in this environment. Deformation during late metamorphic retrogression (greenschist—D3–D4) has a dichotomous expression with crenulations developed in strongly anisotropic phyllonitised serpentinite and irregular fracturesin massive rock.The implications of such polyphase reconstitution for geochemical and isotopic studies are assessed and discussed.

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For much of its length in eastern Finland, the contact between the late Archaean granitoid terrane and early Proterozoic supracrustal rocks is that of a depositional unconformity tectonically modified during the Svecokarelian orogeny. In the Kaavi district, this modification has been extensive, particularly because of thrusting which resulted in tectonic slices of basement being present as inliers within the cover rocks and cover rocks as outliers within the main basement outcrop. Both basement and cover have undergone repeated deformation and metamorphic recrystallisation reflected by the presence of multiple tectonic fabrics and sequential mineral growths. However, it is only locally in major zones of movement that the basement rocks of the Presvecokarelides show major modification as the result of the deformation which had such a profound effect on the cover rocks during the development of the Svecokarelides. Over large areas, the products of four phases of deformation (DI–IV) remain in the basement gneisses together with the products of basic and acidic intrusion whose positions in the deformational sequence can be established‥In the cover rocks, early nappe emplacement (Outokumpu nappe) was followed by the development of isoclinal folds associated with prograde metamorphism (D1). Regionally expressed asymmetrical folds, overturned to the E, with attenuation of overturned limbs and thrusting, involving basement, followed (D2). Subsequent deformation related to wrench faulting (D2c) was followed by the development of more open folds associated with declining geotherms (D3, D4); F3–F4 interference structures are expressed as domes, some of which were a locus of granitoid emplacement (Maarianvaara granitoid suite). D5 and D6 are expressed as cleavages and fractures.Correlation of the structural features in the Kaavi district with those in the Outokumpu and adjacent districts forms the basis both for establishing the regional disposition of basement and cover units and for determining the structural evolution of this part of the Svecokarelides.

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The Partridge Island block is a newly identified tectonic element in the Saint John area of southern New Brunswick, located south of and in faulted contact with Proterozoic and Cambrian rocks of the Ganderian Brookville and Avalonian Caledonia terranes.