Cosmogenic nuclides are the products of nuclear reactions between cosmic rays and elements in atmosphere and lithosphere on earth. Their production is the function of geomagnetic field intensity, surface exposure times and erosion rates. Exposure ages of rock and sediment/soil surfaces can be determined at timescales of ~1000 years to several million years. Erosion rates in a range of ~0.1 mm/k.y. up to 10,000 mm/k.y. are measurable on quartz-bearing geological materials. The measurements of multiple cosmogenic isotopes in sediment, such as fluvial terraces and cave sediments, also allow us to calculate deposition ages of the sediment. As such cosmogenic nuclide dating has become indispensable in earth sciences, particularly, in the field of geomorphology and landscape evolution over the last few decades.

The most widely used nuclides include beryllium-10 (10Be) and aluminium-26 (26Al). Both isotopes are produced within quartz lattice from oxygen and silicon, respectively. Quartz is widely available on the globe, chemically resistant, and its simple crystal structure means that production rates for 10Be and 26Al are well constrained.   

The sample preparation therefore requires extraction of pure quartz. The process includes isolation of quartz via physical and chemical mineral separation techniques, such as magnetic separation, heavy density liquid separation, acid leaching. The extracted quartz needs to be purified via etching with dilute HF. Pure quartz is then dissolved in concentrated HF. Beryllium and aluminium are isolated from unwanted cations (e.g., Fe, Ti) via anion and cation exchange chromatography. Be- and Al-hydroxides are precipitated by pH control and finally calcined to oxides at 1000°C.

The resulting some milligrams of Be and Al oxides are mixed with pure niobium and silver powder, respectively, packed into AMS sample holder. The measurements of 10Be and 26Al isotopes are carried out in our collaborating AMS facilities.