Timescales & Rates

Major developments in the field of geochronological methodology and instrumentation between 2005 and 2015 made possible our ability to rapidly (laser ablation) and precisely (multi-collection TIMS, zircon chemical abrasion) date a variety of geological materials with a wide range of closure temperatures.

PCIGR has established a chemical abrasion technique (CA-TIMS) that allows us to achieve precision better than 0.1% (and now approaching 0.02% for specific samples) on dates of U-Th-Pb-bearing accessory minerals in mafic and ultramafic rocks. These advances have allowed important discoveries related to the crystallization ages and duration of magmatism in major mafic layered intrusions (MLI).

Researchers can now obtain the age of formation of a rock unit, burial (subduction) and uplift (exhumation) rates by thermochronology, or the residence time of crystals in a magma chamber before eruption.

Innovative geochronological research at PCIGR includes:

– integrated geochronology (U-Pb, Lu-Hf, (U-Th)/He, ³He/⁴He) to study in detail the orogenic cycles in the Western Canadian Cordillera;

– precise dating of intrusive-related hydrothermal ore deposits and fluid circulation history in continental arc environments;

– emplacement history of Phanerozoic large igneous provinces to evaluate rapid (~1 million years) vs. protracted magmatism and potential effects on the environment; and

– high-precision dating of large layered mafic-ultramafic intrusions to derive magma production/flux and cooling rates.

PCIGR is also a major contributor to the “EARTHTIME Initiative” with the goal to produce a highly resolved, calibrated geologic timescale through intercalibration of common enriched isotope spikes and synthetic U–Pb isotope solutions.

Below are some snapshots of the projects that fall under this research theme.

Researchers:
Scoates, James
Mortensen, Jim
Hickey, Ken
Weis, Dominique
Smit, Matthijs
Dipple, Greg
Jellinek, Mark
Marshall, Dan
Russell, Kelly
Kennedy, Lori
Thorkelson, Derek
Tosdal, Richard