Дата публикации:

Radiocarbon Dating at SUERC

Ashley, M. Silberman; Direct dating of mineralization at Goldfield, Nevada, by potassium-argon and fission-track methods. Economic Geology ; 71 5 : — Potassium-argon dating of hypogene alunite and K-mica from hydrothermally altered rocks at Goldfield, Nevada, yields mineralization ages of 20 to 21 m.

Radio-carbon dating is a method of obtaining age estimates on of the radioactive isotope that is measured in the same units as “A.” The value.

The first U—Pb geochronological results on the magmatic alignment of the Los Pedroches batholith are presented. The batholith is composed of a main granodioritic unit, several granite plutons and an important acid to basic dyke complex, all of them intrusive after the main Variscan regional deformation phase, D1, along the boundary between the Ossa-Morena and Central Iberian zones SW Iberian Massif.

Zircons from samples on both extremes of the granodiorite massif record nearly simultaneous magmatic crystallization at ca. The U—Pb results combined with new field and textural observations allow to better constrain the age of Variscan deformations D2 and D3 across the region, while the age of D1 remains imprecise. D3 faults and shear bands bearing a strong extensional component developed at ca. Together with available geochemical and geophysical information, these results point to the Variscan reactivation of lithospheric fractures at the origin and subsequent emplacement of hybrid magmas within this sector of the Massif.

In recent models on the lithosphere features of the southern Iberian Massif, it is generally considered that the main structural traits of the area are essentially the consequence of the Variscan orogenic activity e.