lutetium176

Lutetium-176, written as 176Lu, is a long-lived radioisotope of the lanthanide element lutetium. It has a mass number of 176 and occurs alongside the more abundant stable isotope lutetium-175 in natural lutetium.

176Lu decays by beta minus emission to hafnium-176 (176Hf). It has a half-life of about 3.78 × 10^10 years (approximately 37.8 billion years), making it one of the most long-lived radioactive nuclides. The natural abundance of 176Lu is about 2.6% of lutetium, with the remainder dominated by 175Lu, which is stable.

In geochronology, 176Lu is central to the Lu–Hf dating system. As 176Lu decays to 176Hf over time, the 176Hf/177Hf isotopic ratio in rocks and minerals records the history of Lu/Hf differentiation. This method is especially valuable for dating crust formation and differentiation events, and for studying the early evolution of planetary bodies. Zircon minerals are commonly analyzed because they can retain isotopic information while preserving Lu/Hf systematics.

176Lu is produced in stellar nucleosynthesis and persists in Earth's crust in trace amounts due to its long half-life. Its radiological activity is very low, reflecting its slow decay; it does not have widespread medical or industrial use, unlike some other lutetium isotopes.