P. J. Patchett H.S. Pettingill 1981 <p><span>Lu-Hf total-rock data for the Am&icirc;tsoq gneisses of West Greenland yield an age of 3.55&plusmn;0.22Gy(2&sigma;), based on the decay constant &lambda;</span>¹⁷⁶<span>Lu=1.96&times;10</span>^&minus;11<span>y</span>^&minus;1<span>, and an initial</span>¹⁷⁶<span>Hf/</span>¹⁷⁷<span>Hf ratio of 0.280482&plusmn;33. The result is in good agreement with Rb-Sr total-rock and U-Pb zircon ages. In spite of severe metamorphism of the area at 2.9 Gy, zircons from two of the samples have remained on the total-rock line, and define points close to the initial Hf ratio. The initial</span>¹⁷⁶<span>Hf/</span>¹⁷⁷<span>Hf lies close to a chondritic Hf isotopic evolution curve from 4.55 Gy to present. This is consistent with the igneous precursors to the Am&icirc;tsoq gneisses having been derived from the mantle at or shortly before 3.6 Gy. Anomalous relationships between Hf concentration and the</span>¹⁷⁶<span>Lu/</span>¹⁷⁷<span>Hf ratio may suggest that trace element abundances in the Am&icirc;tsoq gneisses are partly controlled by processes related to metamorphism.</span></p> application/pdf 10.1016/0012-821X(81)90093-5 en Elsevier Lu-Hf total-rock age for the Amîtsoq gneisses, West Greenland article