[en] The geological model of the Olkiluoto site consists of four submodels: the lithological model, the ductile deformation model, the brittle deformation model and the alteration model. The lithological model gives properties of definite rock units that can be defined on the basis the migmatite structures, textures and modal compositions. The ductile deformation model describes and models the products of polyphase ductile deformation, which enables to define the dimensions and geometrical properties of individual lithological units determined in the lithological model. The brittle deformation model describes the products of multiple phases of brittle deformation. The alteration model describes the types, occurrence and the effects of the hydrothermal alteration. The rocks of Olkiluoto can be divided into two major classes: (1) supracrustal high-grade metamorphic rocks including various migmatitic gneisses, tonalitic-granodioriticgranitic gneisses, mica gneisses, quartz gneisses and mafic gneisses, and (2) igneous rocks including pegmatitic granites and diabase dykes. The migmatitic gneisses can further be divided into three subgroups in terms of the type of migmatite structure: veined gneisses, stromatic gneisses and diatexitic gneisses. On the basis of refolding and crosscutting relationships, the metamorphic supracrustal rocks have been subject to polyphased ductile deformation, including five stages. In 3D modelling of the lithological units, an assumption has been made, on the basis of measurements in outcrops, investigation trenches and drill cores, that the pervasive, composite foliation produced as a result a polyphase ductile deformation has a rather constant attitude in the ONKALO area. Consequently, the strike and dip of the foliation has been used as a tool, through which the lithologies have been correlated between the drillholes and from the surface to the drillholes. The bedrock in the Olkiluoto site has been subject to extensive hydrothermal alteration, which has taken place at reasonably low temperature conditions, the estimated temperature interval being from slightly over 300 deg C to less than 100 deg C. Two types of alteration can be observed: (1) pervasive (disseminated) alteration and (2) fracturecontrolled (veinlet) alteration. Kaolinisation and sulphidisation are the most prominent alteration events in the site area. Sulphides are located in the uppermost part of the model volume following roughly the lithological trend (slightly dipping to the SE). Kaolinite is located also in the uppermost part, but the orientation is opposite to the main lithological trend (slightly dipping to the N). The third main alteration event, illitisation, appears to form a wedge- or dome-like body located outside and north of the ONKALO access tunnel but penetrating the planned eastern repository panel. 1700 fault planes and fault striation orientations, and sense-of-shear of the faults were measured from drillholes OL-KR1 - OL-KR33. On the basis of the statistical analysis of the orientation data, faults have tentatively been divided in five main fault groups: A, B, C, D and E. Fault-slip vector directions are subhorizontal, N-S trending for group A, gently NE or SW plunging for group B, gently SSE plunging for group C, gently ENE plunging for group D and gently SE plunging for group E. On the basis of drillhole data, 98 fault zones were determined from the drillholes and modelled in 3D. In addition, the model includes 3 fault or fracture zones observed both at the surface and in the ONKALO access tunnel, and two zones interpreted on the basis of charge potential survey. (orig.)