TY - JOUR
T1 - A lead isotope study of an Archaean gold prospect in the Attu region, Nagssugtoqidian orogen, West Greenland
AU - Stendal, Henrik
AU - Frei, Robert
AU - Stensgaard, Bo Møller
PY - 2006/12/5
Y1 - 2006/12/5
N2 - This paper presents a lead isotope investigation of a gold prospect south of the village Attu in the northern part of the Nagssugtoqidian orogen in central West Greenland. The Attu gold prospect is a replacement gold occurrence, related to a shear/mylonite zone along a contact between orthogneiss and amphibolite within the Nagssugtoqidian orogenic belt. The mineral occurrence is small, less than 0.5 m wide, and can be followed along strike for several hundred metres. The mineral assemblage is pyrite, chalcopyrite, magnetite and gold. The host rocks to the gold prospect are granulite facies 'brown gneisses' and amphibolites. Pb-isotopic data on magnetite from the host rocks yield an isochron in a
207Pb/
204Pb vs.
206Pb/
204Pb diagram, giving a date of 3162 ± 43 Ma (MSWD = 0.5). This date is interpreted to represent the age of the rocks in question, and is older than dates obtained from rocks elsewhere within the Nagssugtoqidian orogen. Pb-isotopic data on cataclastic magnetite from the shear zone lie close to this isochron, indicating a similar origin. The Pb-isotopic compositions of the ore minerals are similar to those previously obtained from the close-by ∼2650 Ma Rifkol granite, and suggest a genetic link between the emplacement of this granite and the formation of the ore minerals in the shear/mylonite zone. Consequently, the age of the gold mineralisation is interpreted to be late Archaean.
AB - This paper presents a lead isotope investigation of a gold prospect south of the village Attu in the northern part of the Nagssugtoqidian orogen in central West Greenland. The Attu gold prospect is a replacement gold occurrence, related to a shear/mylonite zone along a contact between orthogneiss and amphibolite within the Nagssugtoqidian orogenic belt. The mineral occurrence is small, less than 0.5 m wide, and can be followed along strike for several hundred metres. The mineral assemblage is pyrite, chalcopyrite, magnetite and gold. The host rocks to the gold prospect are granulite facies 'brown gneisses' and amphibolites. Pb-isotopic data on magnetite from the host rocks yield an isochron in a
207Pb/
204Pb vs.
206Pb/
204Pb diagram, giving a date of 3162 ± 43 Ma (MSWD = 0.5). This date is interpreted to represent the age of the rocks in question, and is older than dates obtained from rocks elsewhere within the Nagssugtoqidian orogen. Pb-isotopic data on cataclastic magnetite from the shear zone lie close to this isochron, indicating a similar origin. The Pb-isotopic compositions of the ore minerals are similar to those previously obtained from the close-by ∼2650 Ma Rifkol granite, and suggest a genetic link between the emplacement of this granite and the formation of the ore minerals in the shear/mylonite zone. Consequently, the age of the gold mineralisation is interpreted to be late Archaean.
KW - Archaean
KW - Geochronology
KW - Gold
KW - Magnetite
KW - Pb isotopes
KW - West Greenland
UR - http://www.scopus.com/inward/record.url?scp=33846853346&partnerID=8YFLogxK
U2 - 10.34194/geusb.v11.4916
DO - 10.34194/geusb.v11.4916
M3 - Article
SN - 2597-2154
SN - 1904-4666
SN - 1604-8156
VL - 11
SP - 53
EP - 60
JO - Geological Survey of Denmark and Greenland Bulletin
JF - Geological Survey of Denmark and Greenland Bulletin
ER -