Presentation on theme: "New gold discovery in the Paleoproterozoic Mauken greenstone belt."— Presentation transcript:
New gold discovery in the Paleoproterozoic Mauken greenstone belt
Mauken greenstone belt The Paleoproterozoic Mauken greenstone belt is situated in an unexplored and untested terrain in Northern Norway. The main economic mineral potential in the Mauken prospect is associated with orogenic and epithermal gold mineralisation. Structurally the greenstone belt is associated with two crustal scale deformation and shear zones. The principal NW−SE direction of the structures are analogue to the regional deformation zones, faults and shear zones in central Lapland, Finland, where a large number of gold deposits are distributed along major deformation zones.
Regional setting Modified after Koistinen et al. (2001).
Geology The greenstone belt is dominated by basalts, amphibolites, chlorite- and sericite schists with lesser carbonate lenses and metaarkosic sandstone. Silicification (i.e. addition of silica), carbonatisation and quartz veining are the dominating alteration types. The greenstone belt is intruded by Paleoproterozoic 1.8 − 1.7 Ga granodiorites. Metamorphic grades from greenschist facies to lower amphibolite facies.
Geology & mineralisation
Mauken greenstone belt The main economic mineral potential in the Mauken prospect is associated with orogenic and epithermal gold mineralisation. The deposit consists of three types of auriferous mineralisations: I)silicification of mafic tuffites with gold-bearing arsenopyrite-pyrite mineralisation. II)gold-bearing arsenopyrite-pyrite en echelon quartz vein and quartz-stockworkgold mineralised system. III)shear-hosted gold-bearing chalcopyrite-pyrite mineralisation in a quartz-ankerite alteration system.
Mineralisations and alteration Close-up of gold mineralised arsenopyrite (silvery needles) rich silicified rock. Gold mineralised arsenopyrite-rich silicified rock with secondary quartz veining. Ankerite-calcite vein with late quartz fracture fillings in sericite schist. Fe-carbonate and magnetite alteration in breccia form in pillow basalt unit.
Grades Mineralised surface rock samples have been collected along a 1750 m almost straight line. The typical Au content of the samples, range between 1 − 4 ppm. Presently the maximum Au grade is 5.79 ppm in a rock grab from an arsenopyrite rich silicified amphibolite. The dilatant zone with the en echelon quartz vein and quartz stockwork systems show a remobilised arsenopyrite, typical with an Au contant range between 0.5 – 1.0 ppm. The shear zone hosted schist with the ankerite-calcite alteration system show a low-grade Au mineralisation, but may prove to be significant in size.