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Russian Geological Research Institute (VSEGEI)
Research
Laboratory and analytical service
Centre of Isotopic Research
Analitical Potantial

Centre of Isotopic Research

ANALYTICAL POTENTIAL

To solve current urgent problems of geology and nature management, as well as ecology, physics, nuclear energy, biology, medicine, etc., our Center has the following basic equipment:

CamScan MX 2500S digital scanning electron microscope (SEM) (CamScan Electron Optics, Ltd, UK) with an X-ray microanalyzer and a cathodoluminescent detector

SEM is designed to observe microscopic objects at magnifications from 8x to 500’000x, study their topography (morphological elements of the surface), phase inhomogeneity and electron beam positioning for subsequent x-ray and cathodoluminescent measurements. The Everhart-Thornley Secondary Electron Detector (SE) is designed to detect low-energy secondary electrons forming a topographic image (with a resolution of <3 nm at 30 kV accelerating voltage). A backscattered electron detector (BSE) can detect the phase inhomogeneity of an object.

For electron probe microanalysis, the SEM is equipped with an INCA Energy 200 system with an Oxford Instruments energy dispersive spectrometer, which enables determining the chemical composition of an object in wide elemental range (from B to U). The electron probe microanalysis and raster electron microscopy are used to solve a wide range of problems:

The CLI/QUA 2 cathodoluminescent detector included in the SEM set significantly expands the capabilities of electron microscopy. The main reason for cathodoluminescence in minerals is the presence of REE microcomponents (Sm3 +, Dy3 +, Th3 +, Tb3 +, Eu2 +, Eu3 +) and Mn2 + in the crystal lattice.
In the case of uneven occurrence of microcomponents during the crystallization of minerals, even the thinnest crystal growth zones will have different characteristics of the cathodoluminescence spectrum that makes these zones visually distinguishable and makes it possible to identify internal morphology of crystals and the evolution of growth forms.


Using the detector, it is possible to qualitatively determine, which microcomponents control the cathodoluminescence in a particular zone of the crystal. The phenomenon of cathodoluminescence occurs in minerals, which do not contain major oxides (FeO, MgO, etc.) in leading positions, since they are quenchers of this type of luminescence. Major objects of cathodoluminescent study are diamonds, zircons, fluorite, apatite, carbonate, feldspar and barite.
When solving isotope-geochemical and geochronological problems, scanning electron microscopy and cathodoluminescence are of great importance at the stage of preliminary mineralogical investigation of substance. These methods make it possible to finally determine the choice of the most correct and effective method of isotope analysis, as well as to identify areas of the sample suitable for research.


SIMS SHRIMP-II Multicollector Secondary-ion High-resolution Microprobe (ASI, Australia)

The device uses in situ ionization of the sample substance by bombarding its surface with oxygen or cesium ions focused by the Kohler system into a beam with a diameter of 5 to 25 microns. Ionization of the subsurface layer of the sample allows obtaining positive or negative ions in an amount sufficient for isotopic analysis. This approach eliminates complicated, time-consuming aspects of sample preparation inherent in traditional mass spectrometry. High mass resolution of the device is achieved by using double focusing (simultaneously in energy and mass) and a very large radius of rotation of the magnet and the electrostatic analyzer.


The principle of the device operation is as follows. A beam of ions with an energy of 10 kV (O- or Cs+) is focused on a small area of the target surface. The ion bombardment knocks atoms and molecules out of the target, ionizing them. These secondary ions are collected using electrostatic lenses and sent to the mass spectrometer in which they are separated in accordance with their mass. Usually, in the spectrum of secondary ions of complex compounds, isobars have a mass difference of <3 x 10-4. High mass resolution of the device is achieved by using double focusing (simultaneously in energy and mass) and a very large turning radius of the magnet (magnet radius is 1 m, radius of the electrostatic analyzer is 1.27 m). Totally, the device weighs about 14 tons and has an ion beam length of more than 7 meters.
SHRIMP-II has the highest sensitivity and resolution of all existing microprobes. Besides, the device available at CIR is also the first microprobe with a multicollector of the SIMS SHRIMP family. This significantly improves its measurement accuracy and performance.
In 2017, SIMS SHRIMP in the CIR was significantly updated by the manufacturer to the level of SHRIMP-IIe/MC.

Applicable scope
SIMS SHRIMP has a large applicable scope. The main one is the U-Pb dating based on uranium-containing minerals (e.g., zircons). Other possible uses include:
• Local analysis of stable isotopes (O, S, N) in minerals
• Local elemental rare earth analysis in minerals

The studied grains of the substance are coated with resin and, upon solidification, they are ground and polished in order to bring their internal parts to the surface. The grain size should be at least from 2 to 2.5 of diameters of the primary beam (the most commonly used spot size is 15 microns). The surface containing the analyzed material should be as flat and smooth as possible; scratches and caverns, as well as relief of any kind, disrupt the process of secondary ions emission.


TRITON TI Multicollector Thermal Ionization Isotopic Mass Spectrometer (ThermoQuest Finnigann MAT, Germany)

The device enables applying techniques for measuring the concentration of U-Th-Pb, Rb-Sr, Sm-Nd, Lu-Hf, Re-Os natural isotopes in rock and mineral samples.


What is TIMS
Thermal ionization mass spectrometry (TIMS) is one of the most precise methods for determining the isotopic composition of elements and compounds. Using PTIMS (positive thermal ionizion mass-spectrometry) and NTIMS (negative thermal ionizion mass-spectrometry), it is possible to analyze the relative abundance of isotopes of alkaline, alkaline earth, rare earth elements, platinum group metals, uranium, thorium, lead, transuranium elements, etc. PTIMS and NTIMS allow studying the variations of isotopic compositions in natural and space objects caused by various processes. The main advantage of these methods of analysis is the simplicity and uniqueness of the interpretation of mass spectra, high accuracy and sensitivity, as well as the absence of mass lines corresponding to multicharge ions.

Product Description
One of the best developments of the Finnigan MAT Company in the field of mass-spectrometric instrument engineering is the TRITON TI Multicollector Thermal Ionization Mass Spectrometer. It is capable of working in both PTIMS and NTIMS modes. The device includes an ion source equipped with a device that enables to carry out sequential analysis of 21 samples, a recording system of ion currents consisting of nine Faraday cylinders and a secondary electron multiplier, as well as electrometric amplifiers corresponding to these elements. The ion current recording channels have extended linearity in the range from 0 to 50 volts. The device is equipped with an ion-optical system with a variable focal length and a system that allows changing the order of connection of amplifiers and Faraday cylinders. Using TRITON TI, it is possible to analyze samples, the mass of which is only a few nanograms of the substance, with very high accuracy. So, the reproducibility error characterizing the systematic error in a series of analyzes of the Sr and Nd isotopic standards is at the level of 5 ppm (0.0005%).

Tasks solved by the device
One of the areas where the use of this device is most relevant is geology. By precise determination of isotopic compositions of a number of elements made at TRITON TI, it is possible to obtain the most important geochronological and isotope-geochemical information on the age and genesis features of a wide variety of geological formations. In the field of isotope geochronology, TRITON TI enables investigations using U-Th-Pb, Rb-Sr, Sm-Nd, K-Ca, Re-Os and Lu-Hf methods. In this case, fundamental issues related to the reconstruction of the geological history of the Earth as a whole and its individual regions are resolved. By dating magmatic, metamorphic and sedimentary rocks, planetary and regional epochs of magmatism and ore formation are identified, the relationship of these processes with global stages of activation of the endogenous activity of the planet's interior is established. The device makes it possible to date “barren” and non-stratified objects, etc.
In the field of isotopic geochemistry, TRITON TI is used to determine the isotopic composition of Pb, Sr, Nd, Os and Hf. By analyzing the isotopic composition of these elements, it is possible to identify rock and ore provenances at the level of large reservoirs (crust, mantle and their mixtures), to determine the nature of the relationship between magmatism and mineralization, as well as the degree of “relationship” of igneous rocks. Based on these isotopic data, it is possible to solve general petrological and metallogenic problems, as well as particular tasks. For example, studying the Sr isotopic composition in marine carbonate is used in stratigraphy to correlate barren sedimentary strata, and the Pb isotopic composition in stratiform polymetallic deposits indicates the dimensions of mineralization with a certain degree of probability.


NEPTUNE Multicollector Isotopic Plasma Mass Spectrometer (MC-ICP-MS) (ThermoQuest Finnigann MAT, Germany)

The device allows applying techniques for measuring the mass concentration of natural isotopes of metals (including Li, Cu, Ni, Pb, U) in rock and mineral samples.
The high-resolution mass spectrometer has been designed on the basis of the world's best Multicollector isotope platform. The system combines the unique characteristics of the TRITON TI analyzer and the plasma source and ELEMENT2 interface. It is successfully used for solving tasks in geochronology, geochemistry, cosmology and many other applications where the accuracy and efficiency of isotopic measurements are of importance.


The device allows applying isotope-geochemical methods that require isotope analysis of difficultly ionized elements, such as W, Hf, Pt, Os that makes it possible to use Lu-Hf, Pt-Pt and Re-Os geochronological methods. Sample input from the solution, entire ionization of all components, stable mass discrimination and high accuracy of the multicollector measuring unit make it possible to simplify preliminary chemical procedures for sample preparation and increase accuracy and productivity when implementing standard geochronological methods (U-Pb, Sm-Nd, Rb-Sr).
An important feature of the device is its capability to work in combination with the laser ablation system that permits implementing high-local techniques of isotope-geochemical investigations. The existing New Wawe DUV-193 laser ablation system is based on the Lambda Physics excimer ultraviolet laser that minimizes effects of elemental fractionation and provides minimum size of the laser spot (6-10 microns). The system makes it possible to perform high-local isotope-geochemical studies of mineral growth zones directly from the polished section or even standard petrographic thin section.


ELEMENT-2 Elemental High-resolution, High-sensitive Plasma Mass Spectrometer (HR-ICP-MS) (ThermoQuest Finnigann MAT, Germany)

The device allows implementing techniques for measuring the mass concentration of a wide range of chemical elements in rock and mineral samples, in oil, natural, drinking water and distillates. The studied object can be represented both in liquid and in solid phase.


Inductively coupled plasma ion mass spectrometry (ICP) is the most advanced method for determining elemental composition. The double focusing ELEMENT2 ICP mass spectrometer is the most advanced instrument of this type in technical performance. The device has a mass measurement range from 6 (Li) to 260, which is standard for ICP mass spectrometers and allows determining over 70 elements of natural and artificial origin. Three levels of resolution makes it possible to solve a variety of problems. In low-resolution mode is it possible to reach the detection limits at the level of ppq (10-14 - 10-15 g/g) for many elements. In the medium and high-resolution mode, it is possible to measure complex samples free from oxides, carbides, etc. This significantly increases the accuracy of determination and maintaining sensitivity at a level of 10-11 - 10-13 g/g. In terms of scanning speed, this device is comparable with standard quadrupole ICP/MS systems and significantly surpasses those equipped with collision chambers. The dynamic range of the detector enables during one sample shooting to analyze the matrix and microimpurities that differ in concentration from each other up to nine orders, and in some cases even more, without diluting and concentrating the sample.
The registration and processing system allows obtaining accurate results of quantitative analysis and using it for isotope screening. The accuracy of determining isotope ratios is hundredths of a percent that allows solving many geological, environmental (including pollution sources) and technical problems. The technical parameters of ELEMENT2 make it indispensable in environmental control, nuclear energy, geology and geochemistry, oil refining, metallurgy, the semiconductor industry, etc.
The device uses the mobile laser ablation system DUV-193 in conjunction with the NEPTUNE device, which also enables the implementation of high-local techniques of geochemical and technical studies.


DUV 193 Laser Ablation System (Lambda Physics Compex 102, USA)

  • Wavelength of the ultraviolet laser is 193 nm.
  • Energy density up to 80 J/cm2.
  • Minimum spot size is 5 μm.
  • Carrier gas in the ablation cell is helium.
  • A microscope with a magnification of 200 to 1000 provides a means of observing micro-features of the studied surface, and a multifunctional manipulator similar to the joystick makes it possible to control the position of the sample-target. Hardware (high-resolution video camera and image capture board) and software give the possibility to display a picture of the sample surface directly on the computer monitor to select the point of analysis. There are various modes of bypassing a given sequence of points on the sample surface.


    Micromass-NG5400 isotope gas static mass spectrometer (UK)

    The NG-5400 is a static mass spectrometer designed to analyze noble gases. It gives the possibility to implement techniques of measuring the isotopic composition of He, Ne, Ar, Kr, Xe, as well as elements present in natural gases, waters, oil, microinclusions and the crystal lattice of minerals and rocks (3He/4He, 22Ne/20Ne, 40Ar/36Ar, 36Ar/38Ar et al.).


    A collector with resolution > 600 makes it easier to separate 3He+ peaks from HD+ and 3H+. Electro-polishing of the internal metal surfaces and heating them to 350°C minimizes degassing and background at the mass 38 (interference 12C3 + and 1H35Cl), respectively. This device is also equipped with a Faraday collector, an ion counter with an electronic multiplier and an analogue Daly detector.
    The sample preparation system of this mass spectrometer is equipped with a furnace. Its controller with a microprocessor allows programming the heating of samples. The furnace can work with temperatures up to 2000°C. In the furnace, there is a carousel for 10 samples with a total weight of several grams, sequentially loaded into the thermal element.


    DELTA Plus and DELTA Plus XL mass spectrometers (ThermoQuest Finnigann MAT, Germany) for studying the isotopy of light stable isotopes

    For studying the isotopic composition of H, C, S, O in water, organic liquids, solid and gaseous organics, carbonates, silicates.


    DELTA Plus mass spectrometers are the standard in stable isotope mass spectrometry due to their flexibility, reliability, sensitivity and accuracy for applications in geology and paleoclimatic studies, determining the origin of many products, medical diagnostics, environmental monitoring, falsification control, and criminalistics. The version of the device with extended DELTA Plus XL optics is designed for applications where hydrogen/deuterium and oxygen isotope ratios are measured with complete suppression of helium interference.

    The devices are equipped with a wide range of peripheral instruments:
    • gas chromatograph
    • elemental analyzer
    • a universal system for sample preparation and injection of gas samples, operating on-line
    • a device for direct measurement of the H/D isotope ratio from water


    Highly sensitive CT-1220 Quantulus counter of intensity of alpha and beta radiation (Finland)

    The device is designed to measure extremely low levels of alpha and beta activity. It is a liquid-scintillator counting system with a multi-channel analyzer. The optimized design and the combination of active and passive protection makes it possible to maximize the sensitivity and reduce the background of the instrument. The tasks to be solved are the analysis of trace concentrations of tritium, S-14, Sr-90, Cs-137, Pb-210, Ra-226 isotopes. The scope includes radiocarbon dating, environmental studies, geophysical and other studies, when it is required to determine the presence of small amounts of alpha and beta emitters.


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