Instrument
The Alphachron
Alphachron — Automated Helium Thermochronology
Exceptionally accurate turn-key helium measurement solution for (U-Th)/He thermochronology.
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The first commercially available automated helium extraction system
The Alphachron is the first commercially available, automated, integrated, and compact turnkey system designed for the extraction and measurement of gases from mineral samples. Developed by the CSIRO Division of Exploration and Mining (DEM) and Patterson Instruments, it is now manufactured and marketed by Thermochron Systems.
During the course of research on the 4D evolution of ore systems, the CSIRO DEM found the need to develop instrumentation for rapid and automated analysis of mineral samples, which became the Alphachron. The Alphachron technology, based on an innovative helium extraction/measurement instrument, is being adopted by the market as a standard analytical platform allowing an accurate determination of the thermal history of the Earth's crust.
Up to 25 mineral samples can be loaded into the laser chamber and heated — approximately 1000°C for apatite and approximately 1250°C for zircon — under vacuum for five to fifteen minutes with a 980 nm diode laser. The extracted gas is analyzed to determine its radiogenic helium-4 content, with the gas extraction process repeated to ensure complete removal. Parent mineral concentrations are subsequently determined by ICP-MS analysis.
Technical Details
Specifications
The Alphachron is a turnkey system for the automated extraction and measurement of radiogenic helium from mineral samples. The instrument integrates a laser-heating module with a gas-handling module and an optional quartz-halogen heating system. The system is delivered prefabricated and is ready to use for measurement after installation and minimal commissioning. After extraction of the helium by diode laser or quartz-halogen heating (with the optional Diffusion Cell add-on), mineral grains are digested and analyzed using standard ICP-MS techniques.
High Vacuum System
Oil-free diaphragm fore pump, hybrid turbomolecular pump with controller, and ion pump with controller
Pressure Gauges
Pirani gauge at the fore pump; Full Range gauge (< 5×10⁻⁹ torr) at the turbo pump
Quadrupole Mass Spectrometer (QMS)
Range: 1–100 amu · Detector: Faraday / secondary electron multiplier · Detection limit: < 2×10⁻¹¹ mbar · Sensitivity of Ar: > 5×10⁻⁴/200 A/mbar
Laser System
915 nm diode laser with lens system, power supply, safety shield, and automated X-Y stage with machine vision
Reference Standards
3 × 3.3 L stainless steel tanks: ³He spike, ⁴He analytical standard, and ⁴He reference standard
Sample Capacity
25-sample laser chamber with sapphire window
Diffusion Cell Option
Maximum operating temperature 600°C with integrated automation software
Gas Handling
Two SAES getters with getter control and activation power supply; stainless steel high-vacuum line with automatic and manual valves
Included With Every System
- Dedicated computer system (Windows PC) interfaced to the Alphachron digital I/O system, quadrupole, laser controller, CCD camera, and X-Y stage controller
- Solenoid system and control panel for automatic valve control
- Alphachron system software and drivers for laser automation, gas handling, and measurement of radiogenic helium
- Data reduction software
- Installation and training
- Instrument manuals
Automation Software
A powerful visual software package based on LabVIEW allows users to create and adjust the operational sequence of system experiments without any previous programming knowledge. An intuitive interface is included to help users manage experiments using simple textual files. These 'scripts' are able to control tightly all aspects of the system's automated operation. Users can define separate scripts for each of the samples present on the sample disk, allowing multiple tests on varying samples during one automated run, without the need for user intervention or loading/reloading of samples between tests.
Application Notes
From mineral exploration to plate tectonics
An increase in the number of research institutions around the globe utilizing (U-Th)/He thermochronometry for applications including mineral and petroleum exploration, geohazards assessment, and continental evolution studies, has prompted demand for a world-first technology developed by CSIRO Exploration & Mining and manufactured by Thermochron Systems.
Uranium-thorium-helium thermochronometry is a highly sensitive and cost-effective method of radiometric age dating that can be used to determine the thermal history of the Earth's crust. The major benefit of this technology to the mineral resources industry lies in the ability to quantitatively determine the low-temperature thermal histories of mineral belts and petroleum basins. Helium thermochronometry also has applications in several fields of geological research such as landscape evolution, plate tectonics, sedimentary provenance studies, and more.
Research Applications
- Mineral and petroleum exploration
- Low-temperature thermal history determination of mineral belts and petroleum basins
- Landscape evolution studies
- Geohazards assessment
- Plate tectonics and continental evolution
- Sedimentary provenance analysis
- Ore deposit research
Literature
Selected References
Recent publications demonstrating the application of this technology in ore deposit research include:
McInnes, B.I.A., Evans, N.J., Fu, F.Q. and Garwin, S., 2005. Application of thermochronometry to hydrothermal ore deposits, in Reiners, P. and Ehlers, T. (Eds.), Thermochronology, Reviews in Mineralogy & Geochemistry, Vol. 58, p. 467–498 (ISSN 1529-6466).
McInnes, B.I.A., Evans, N.J., Fu, F.Q., Garwin, S., Belousova, E., Griffin, W.L., Bertens, A., Sukarna, D., Permanadewi, S., Andrew, R.L. and Deckart, K., 2005. Thermal history analysis of selected Chilean, Indonesian and Iranian porphyry Cu-Mo-Au deposits; in Porter, T.M. (Ed.), Super Porphyry Copper & Gold Deposits: A Global Perspective, Vol. 1; PGC Publishing, Adelaide, pp. 27–42.
McInnes, B.I.A., Farley, K.A., Sillitoe, R.H. and Kohn, B., 1999. Application of (U-Th)/He dating to the estimation of the sense and amount of vertical fault displacement at the Chuquicamata Mine, Chile, Economic Geology 94, 937–948.
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