Sample Submission

Lu-Hf, Sm-Nd geochronology typically requires a total of 800mg of clean garnet fractions and at least 1 gram of whole rock powder. That would provide for 2 whole rock and 4 garnet fractions for each rock sample. 

In specific cases, the required amount of garnet can be more or less than 800mg. Please contact us if your sample falls into one of the following situations: 1) known or suspected low Hf (<0.1ppm) of garnet. 2) large amount of LREE-rich inclusions in garnet; if doing Sm-Nd dating, additional material is needed for leaching. 3) other specific analyses (e.g. micro-sampled garnet zones).   

The garnets should be crushed to fragments of 250-375 µm and handpicked under the binocular microscope to avoid inclusions to the extent possible. Detailed procedures for rock fragmentation and mineral sorting are generally searchable on the internet and are not described here. There are also labs and companies (like Zirchron) offering mineral separation services.

The whole rock powder should be prepared from either a total rock or (preferably) garnet-free rock chips. An agate mortar is preferred for the grinding but almost all methods will be acceptable EXCEPT tungsten-carbide grinding equipment. Avoid this as it makes the sample unusable because of tungsten interferences on hafnium. 

Whole rock power for Sr, Nd, Hf and Pb isotopic analyses should be prepared the same way as that for geochronology analyses except that tungsten-carbide grinding equipment could be used when Hf isotope is not an interest of analysis.  

Please put each fraction in a separate well-labeled vial describing its contents. Glass DRAM vials are recommended as they are made of anti-static materials, but any securely closed vial, even delicately folded weighing paper envelopes, will work fine as long as sample loss is prevented during sample transport.