Geology, petrology and alteration geochemistry of the Palaeoproterozoic intrusive hosted Älgträsk Au deposit, Northern Sweden

Abstract

The Älgträsk intrusive hosted Au deposit, Skellefte district, northern Sweden, is situated in the oldest, most heterogeneous part of the c. 1.89–1.86 Ga Jörn granitoid complex, which intruded a complex volcano–sedimentary succession in an island arc or continental margin arc environment. The Tallberg porphyry Cu deposit, situated only 3 km west of Älgträsk, is associated with quartz feldspar porphyritic dykes. These dykes are suggested to be genetically related to similar porphyry dykes in Älgträsk and the tonalitic host rock in Tallberg. The granodiorite hosting the Älgträsk Au-deposit does not appear to be genetically related to the tonalite or the porphyry dykes.

Geology and Age Constraints on the Origin of the Intrusion-Related, Sheeted Vein-Type Åkerberg Gold Deposit, Skellefte District, Sweden

“…A good candidate for the source of gold may be the granodiorite itself. This rock which occasionally shows a porphyritic texture is, petrologically and age-wise, similar to gold-related porphyries elsewhere in the Skellefte district, as exemplified by those at Älgträ sk [11], Vinliden and Storklinten [8], and a genetic connection between porphyry magmatism and gold formation seems likely.…”

“…Gold mineralization in the overall Skellefte district are of different types and occur in different geological environments [11,16,[35][36][37][38]. Generally, many gold-only mineralization can be described as structurally controlled orogenic gold deposits.…”

“…In contrast, other gold deposits in the Skellefte district region, such as, e.g., Grundfors [16], may exemplify an orogenic type of gold deposit, which is widely held to result from crustal-scale flow in connection with metamorphic dehydration [20]. (1) SOD = Skellefte ore district; (2) qz=quartz; (3) py=pyrite; (4) po=pyrrothite; (5) cpy=chalcopoyrite; (6) apy=arsenopyrite; (7) sp=sphalerite; (8) sch=scheelite; (9) tour=tourmaline; (10) cc=calcite; (11) loell=loellingite; (12) amp =amphibole.…”

Palaeoproterozoic porphyry Cu–Au, intrusion-hosted Au and ultramafic Cu–Ni deposits in the Fennoscandian Shield: Temporal constraints using U–Pb geochronology

“…1), situated close to the contact between the JIC and the volcanosedimentary succession of the SD. The Palaeoproterozoic Tallberg porphyry Cu ±Au ±Mo deposit comprises disseminated and quartz vein stockwork sulphides associated with propylitic, chloritic and phyllic alteration hosted by a GI intrusion of tonalitic composition (Bejgarn et al, 2011;Weihed, 1992b). It is associated with a younger intrusive at depth (Fig.…”

Granite-related ore deposits: an introduction

“…The petrology and alteration geochemistry of Palaeoproterozoic intrusions that host Au deposits in Sweden is the main theme of the contribution by Bejgarn et al (2011) who studied a structurallycontrolled mineralization that occurs within zones of proximal phyllic/silicic and distal propylitic alteration. It comprises mainly pyrite, chalcopyrite, sphalerite with accessory Te-minerals, gold alloys, and locally abundant arsenopyrite.…”