The dikes of the area can be divided into three groups having different directions of remanent magnetization after demagnetization in the AC field. One of these groups has a direction which coincides with that measured for the Jotnian dolerites in the Satakunta and Vaasa archipelago. The direction of the second group differs but slightly from this and the third one has a reversed orientation. The age relations and the origin of the magnetization are discussed. CONTENTS Introduction 57 Samples 58 Measurements and demagnetization 59 Discussion 61

The Laukunkangas Ni-Cu deposit in a Svecokarelidic synorogenic plutonite is located at the southeastern end of the Kotalahti nickel belt. The mineralization is associated with the norites, olivine gabbros and peridotites of an olivine tholeiitic suite. It contains about 4.5 million tons of ore in situ averaging 0.33 %> Ni and 0.10 %> Cu. The intrusive is a rather small pipelike body with an elliptical surface plan. It extends to a depth of at least 300 m; its largest horizontal dimension is about 1 km and its width in the middle of the intrusive is some 200 m. The variations in the Ni and Fe contents in silicates, the MgO content in rock types and the Ni content in the sulphide phase clearly indicate the internal layering in the intrusive. Emplacement probably took place in two or three stages. The boundaries between the layers show contamination that is reflected in the distribution of MgO and trace elements. »The model crystallization temperatures» suggest that the intrusion was emplaced in three separate phases. The mineralization occurs near the contact zone at the eastern end of the intrusive. The few nickel-rich portions encountered inside the intrusive are small and discontinous lenses or slabs. The mineralization is characterized by the following parameters: Ni/Co = 17.31, Ni/Cu = 3.15, Cu/Co = 5.49, and the Ni content in sulphide phase 4.81 %>.