Southwest of the well-known Skellefte Dist
rict, no
rthe
rn Sweden, a new gold o
re p
rovince, the so called Gold Line, is p
resently being explo
red. Du
ring the past decade a numbe
r of gold occu
rrences have been discove
red in this a
rea. The la
rgest known gold occu
rrence is the Fäboliden deposit. Late-to post-o
rogenic, ca. 1.81 to 1.77 Ga, Revsund g
ranite constitutes the main
rock type in the Fäboliden a
rea and su
rrounds a na
rrow belt of mine
ralized metag
reywackes and metavolcanic
rocks. The sup
rac
rustal
rocks a
re st
rongly defo
rmed within a
roughly N–S t
rending subve
rtical shea
r zone. The mine
ralization constitutes a 30 to 50 m wide, N–S st
riking, steeply dipping zone. The mine
ralization is commonly hosted by a
rsenopy
rite-bea
ring qua
rtz-veins within the sup
rac
rustal
rocks. The qua
rtz veins pa
rallel the main foliation in the shea
r zone. Gold is closely associated with a
rsenopy
rite-löllingite and stibnite and found in f
ractu
res and as inte
rg
rowths in the a
rsenopy
rite-löllingite. Gold is also seen as f
ree g
rains in the silicate mat
rix of the host
rock.
The proximal alteration zone displays positive correlation with Ca, S, As, Ag, Sb, Sn, W, Pb, Bi, Cd, Se, and Hg, whereas K and Na show a slightly negative correlation. The hydrothermal mineral assemblage in the proximal alteration zone is diopside, calcic amphibole, biotite, and minor andalusite and tourmaline. This type of assemblage is commonly recognized in hypozonal orogenic gold deposits worldwide. Garnet-biotite geothermometry indicates amphibolite facies in the Fäboliden area.
The ductile fabric that hosts the mineralization is also found in the margin of the surrounding Revsund granitoid. It is therefore suggested that at least the final stages of the gold mineralization are syn- to late-kinematic, and the minimum age for the mineralization is thus constrained at ca. 1.80 Ga (Revsund age).