Direct dating of gold by radiogenic helium

Here we report the application of this method to dating of gold mineralization, through the case study of an auriferous deposit in Diamantina in Brazil.A gold rush that took place ∼300 yr ago in Diamantina, Minas Gerais, southeastern Brazil (Fig.But the effort pays, for with a feel for deep time comes a sense of its great power: Given enough time, almost anything energetically possible can happeneven at very large scales.And so it goes with the bending of seemingly rigid rocks, the cutting of majestic canyons, the raising and erasing of entire mountain ranges, the opening and closing of globe-girdling oceans, and the incessant splitting and regrouping of the dancing continents.The first results of the U-Th-He dating of native gold from the Pedrolampi (central Karelia) and Witwatersrand (South Africa) deposits are in adequate agreement with available independent geochronological data. This allows us to consider native gold as a U-Th-He mineral geochronometer for the direct dating of ore-forming processes. These ages tie the Diamantina gold mineralization to the Brasiliano orogenic event, in the context of the Gondwana amalgamation.

A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons.In this paper, we consider the application of the U-Th-He method of isotope geochronology for native gold dating. It was shown that inclusions of uranium- and thorium-bearing minerals, including rare earth element phosphates, are one of the main form of uranium and thorium occurrence and, consequently, the main source of radiogenic helium in native gold. The planet's had ample time for all of this, even if it's out of our ken.Under great confining pressures, or at depths where temperatures reach a significant fraction of their melting points (typically 10-15 km), rocks that are quite brittle at the surface become sufficiently plastic to deform without fracture at rates comparable to the rate at which fingernails grow (~10 mm/yr).