Platinum-group minerals in the Lillefjellklumpen nickel-copper deposit, Nord-Trøndelag, Norway

The Lillefjellklumpen Ni-Cu deposit occurs in the Gjersvik Nappe in the Upper Allochthon of the central Norwegian Caledonides. The area has been interpreted by earlier workers as part of an ensimatic island are of Lower to Middle Ordovician age. The mineralization is associated with a small body of metagabbro occurring at the contact between gabbro and greenstone. The massive sulphide body consists of pyrrhotite, pyrite, pentlandite, chalcopyrite, magnetite and silicates. The average Ni content is 3.6% and the Cu content is 1.2 %. The total platinum group element (PGE) content is 5.6ppm, Pt (1.8 ppm) and Pd (3.1 ppm) accounting for 4.9 ppm. The Pt + Pd/Ru + Ir +Os ratio is 9.8, within the range reported for gabbro related deposits. The average chondrite normalized PGE pattern is similar to that of the Kanichee deposit although Lillefjellklurnpen has lower absolute PGE values. Merenskyite is the main platinumgroup
mineral (PGM), but sperrylite, moncheite and temagamite (?) also occur. The PGM occur as small
( < 20 µm) inclusions in pyrrhotite and chalcopyrite as well as on grain boundaries. The Lillefjellklumpen deposit probably represents a magmatic sulphide segregation related to a layer 3 (ensimatic) gabbro body later remobilized during a tectonic event and redeposited in its present position.