Abstract
Gold occurrences have been found in the Palaeoproterozoic Ketilidian Mobile Belt of South Greenland within the past ten years. The mineralization occurs in various settings with different element associations: Au in the Archaean; Au in the Palaeoproterozoic border zone; the association Au-Bi-(Ag-As-W-Cu-Mo) in the Julianehåb batholith; the association Au-As in supracrustal rocks; and the association Au-Cu within a volcano-sedimentary sequence at the edge of the Julianehåb batholith.The emplacement of the juvenile I-type Julianehåb batholith lasted from 1850 to 1800 m.y. with late-stage intrusions until 1770 m.y. Emplacement of the gold mineralization is considered to have taken place in the late stage of formation of the batholith (1800-1770 m.y.) and during the regional deformation and metamorphism before the intrusion of rapakivi granites. Local remobilization of metals, however, was caused by hydrothermal activity around some rapakivi granitoids. In essence, therefore, gold deposition in South Greenland is restricted to a quite narrow time interval.Lead isotopes from different occurrences in South Greenland indicate two main stages of gold emplacement. The first was related to the Palaeoproterozoic regional deformation and metamorphism (1792-1785 m.y.), during which sediment-hosted gold was epigenetically remobilized into shear zones and vein systems. Pb in these occurrences is indicative of a ca 2000-m.y. source, which is compatible with the direct basic host rocks to these occurrences. The second stage of gold deposition appears to have been temporally related to late stages of emplacement of the Julianehåb batholith. The source of the slightly more evolved Pb in these occurrences is difficult to assess, but a mixture of juvenile Pb from the batholith with some contributions from the host rocks may explain the scatter of data around a 1780-m.y. reference line.
Published Version
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