1. Introduction
Uranium Series Chronology Laboratory in the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS) was founded in 2014. Based on the radioactive decay of ²³⁸U-²³⁴U-²³⁰Th, the ages of stalagmites, tufa and evaporites formed in the surface environment, and corals, cold spring carbonates and hydrothermal sulfides formed in the marine environment are determined using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) for use in oceanography, paleoclimatology, paleoenvironmentology and archeology. Researchers are welcome to cooperate in the laboratory.

2. Facilities
We have one Thermo-Fisher-Scientific Neptune-Plus multi-collector inductively coupled plasma mass spectrometer, to provide high precision measurements for uranium and thorium isotopic ratios using isotope dilution techniques. The Neptune-Plus has a mass detection range of 4-310 amu (atomic mass units), and a highest resolution (5%, 95%) of ≥ 8000.

Fig.1. Neptune Plus MC-ICP-MS

This instrument was equipped with nine Faraday cups (with 10¹⁰ Ω,10¹¹ and 10¹³ resistors) and one secondary electron multiplier (SEM) with one retarding potential quadruple lens (RPQ) system in the back. An Aridus II desolvator (CETAC) and an auto-sampler ASX-112FR were used for sample introduction to reduce solvent interference, improve signal stability.

3. Experimental conditions
We have two clean rooms (Class 1000) for chemical separation and instrumental analysis, and there are six fume hoods (Class 100) and one central working bench for chemical treatment. The temperature and relative humidity are set at 21±2℃ and 55±3% respectively, and could be precisely controlled by the computer.

Fig.2. The ultra-clean chemical room

The water purification system includes a pretreatment system, Milli-Q Elix-35 and Milli-Q Advantage A10. The system has a 200 L tank, which can produce 15 MΩ water in 35 L/h for supplying 18.2 MΩ water continuously. The U-Th blank of the water is low and suitable for the U-series work.

4. Analysis item
a) U-Th ages (<600 ka): 
    1) Quaternary carbonate: stalagmite, coral, tufa, etc.; 
    2) Quaternary sulfide: submarine iron sulfide, copper sulfide, zinc sulfide, etc.; 
    3) Quaternary evaporite minerals: gypsum, halite, etc.
b) U-Th isotope analysis (²³⁴U/²³⁸U, ²³⁸U/²³⁵U etc.):