Ar-Ar Geochronology Laboratory

Ar-Ar Geochronology Laboratory

The institute attaches great importance to the construction and management of its laboratories. The strategic objectives of the supporting system are to establish fully-opened national experimental research platforms concerning the significant scientific issues based on important scientific research projects, yield data which reach international standards and earn peer recognition through the development of new technologies and methods, therefore making it a responsible popular science base. The Laboratory was established for the purpose of conducting fundamental research relating microstructure and chemical composition characteristics to the fields of geochronology, geosphere deep dynamics, Earth evolution, cosmochemistry, comparative planetology, mineral resources etc. The three facilities are all equipped with Energy Dispersive Spectrometers EDS , which can provide composition information. Students and researchers can use these facilities once they have acquired basic training. These facilities allow direct in situ measurement of the isotopic and elemental composition of nearly all the elements in the periodic table from H to U, on both the micro- and nanometric scales. The laboratory plays an important role in the fields of geochronology, geosphere deep dynamics, Earth evolution, cosmochemistry, comparative planetology, mineral resources research, and global change. The double focusing system is includes a large radius magnetic sector and electrostatic analyzer ESA , which provides very high mass resolving power MRP without significant loss of secondary ion intensity.


Time is a fundamental parameter in the Earth Sciences whose knowledge is essential for estimating the length and rate of geological processes. The 40 Ar- 39 Ar method, variant of the K-Ar method, is based on the radioactive decay of the naturally occurring parent 40 K half-life 1. The 40 Ar- 39 Ar method, applied to K-bearing systems minerals or glass , represents one of the most powerful geochronological tools currently available to constrain the timing of geological processes.

It can be applied to a wide range of geological problems and to rocks ranging in age from a few thousand years to the oldest rocks available.

The lab is now equipped with two 40Ar/39Ar dating systems, for conventional furnace step-heating and laser ablation analyses: Conventional Furnace System:​.

The extensive calibration and standardization procedures undertaken ensure that the results of analytical studies carried out in our laboratories will gain immediate international credibility, enabling Brazilian students and scientists to conduct forefront research in earth and planetary sciences. Modern geochronology requires high analytical precision and accuracy, improved spatial resolution, and statistically significant data sets, requirements often beyond the capabilities of traditional geochronological methods.

The fully automated facility will provide high precision analysis on a timely basis, meeting the often rigid requirements of the mineral and oil exploration industry. We will also discuss future developments for the laboratory. The project enabled importing the most advanced technology for the implementation of this dating technique in Brazil. Funding for the acquisition of instrumentation i.

Argon Geochronology Laboratory

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40Ar/39Ar dating of quartz samples (J12Q) from breccia ore yields a The argon isotope analyses were undertaken in the Key Laboratory of.

The effects of food additives will also influence biological activity. When a sample has dried out, it is no longer viable to the point of being detectable. While this data may show that the sample material is stable, it does not necessarily mean that a subject sample may be an exact match to a known source. Frequency , Standard Of Comparison , Density 1. For example, temperature will impact biological activity. In his new book, Bill Clinton blames the culture On Sunday, Bill Clinton defended his decision to use an Arkansas governors mansion for a fundraiser.

Federal Government, U. Clintons campaign blamed the culture, arguing it was inappropriate because Clinton knew he would be there. Storage conditions will vary. This will impact how samples perform compared to a known standard or a known average sample. The data are not designed to predict how samples will react or react to an unknown variable – that is, whether a sample will deteriorate or not.

The data reported are for a standard of known age, not the actual age of the sample. Other variables must be taken into consideration as well.

Argon–argon dating

Potassium, an alkali metal, the Earth’s eighth most abundant element is common in many rocks and rock-forming minerals. The quantity of potassium in a rock or mineral is variable proportional to the amount of silica present. Therefore, mafic rocks and minerals often contain less potassium than an equal amount of silicic rock or mineral. Potassium can be mobilized into or out of a rock or mineral through alteration processes.

Due to the relatively heavy atomic weight of potassium, insignificant fractionation of the different potassium isotopes occurs.

Samples are co-irradiated with monitor standards to define the “J-value”, used for age calculations. The is used to measure the Ar isotope compositions and.

Western Australian Argon Isotope Facility. The Ar technique can be applied to any rocks and minerals that contain K e. Typically, we need to irradiates the sample along with known age standards with fast neutrons in the core of a nuclear reactor. This process converts another isotope of potassium 39 K to gaseous 39 Ar. This allows the simultaneous isotopic noble gas measurement of both the parent 39 Ar K and daughter 40 Ar isotopes in the same aliquot.

The main advantage of Ar-Ar dating is that it allows much smaller samples to be dated, and more age and composition e. The extraction line is associated with a Nitrogen cryocooler trap and two AP10 and one GP50 SAES getters that altogether allow purifying the gas released by the sample during laser heating.

This allows the measurement of a larger dynamic range of Ar ion beam signal on much smaller and thus likely purer and younger sample aliquots. Their second advantage is the ability to measure the 36Ar on the CDD multiplier while other masses are measured on the faraday detectors, resulting in analytical precision one order of magnitude better than with previous generation instruments. Their third advantage is much faster sample analysis i.

A new dedicated low volume Noble Gas extraction line capable of collecting and cleaning the gas extracted from a variety of samples, using a PhotonMachine CO2 laser capable of delivering a homogenous laser beam of up to 6mm wide, is attached to the ARGUS VI mass spectrometer. Collaborative research resulting in publication written by F.

Geochronology and Isotopes

The potassium-argon K-Ar isotopic dating method is especially useful for determining the age of lavas. Developed in the s, it was important in developing the theory of plate tectonics and in calibrating the geologic time scale. Potassium occurs in two stable isotopes 41 K and 39 K and one radioactive isotope 40 K. Potassium decays with a half-life of million years, meaning that half of the 40 K atoms are gone after that span of time.

Its decay yields argon and calcium in a ratio of 11 to The K-Ar method works by counting these radiogenic 40 Ar atoms trapped inside minerals.

CO2 laser and a double resistance furnace used to perform 40Ar/39Ar dating, a variant of K/Ar dating. Our clients comprise faculty and graduate students both.

The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes. The sample is generally crushed and single crystals of a mineral or fragments of rock hand-selected for analysis. These are then irradiated to produce 39 Ar from 39 K.

The sample is then degassed in a high-vacuum mass spectrometer via a laser or resistance furnace. Heating causes the crystal structure of the mineral or minerals to degrade, and, as the sample melts, trapped gases are released. The gas may include atmospheric gases, such as carbon dioxide, water, nitrogen, and argon, and radiogenic gases, like argon and helium, generated from regular radioactive decay over geologic time.

The J factor relates to the fluence of the neutron bombardment during the irradiation process; a denser flow of neutron particles will convert more atoms of 39 K to 39 Ar than a less dense one. However, in a metamorphic rock that has not exceeded its closure temperature the age likely dates the crystallization of the mineral.

Thus, a granite containing all three minerals will record three different “ages” of emplacement as it cools down through these closure temperatures. Thus, although a crystallization age is not recorded, the information is still useful in constructing the thermal history of the rock. Dating minerals may provide age information on a rock, but assumptions must be made. Minerals usually only record the last time they cooled down below the closure temperature, and this may not represent all of the events which the rock has undergone, and may not match the age of intrusion.

Western Australian Argon Isotope Facility

Dating geological events is essential for putting quantitative constrain on the processes that have shaped the Earth on which we live today e. The lab features the latest technical developments for measuring such ratios at the highest temporal and spatial resolution using continuous CO 2 Current projects are aimed at 1 Providing temporal constraints on active volcanic fields southern Ethiopian and Pantellerian rifts, volcanic unrest at Tenerife, Mount Vesuvius and Phlegrean fields, Canaries archipelago and Italy , 2 Restoring the thermal-strain evolution of extensional detachment and exhumation of High-Pressure metamorphic units Cyclades, Aegean Sea , 3 Constraining the thermal structure of the Scottish Caledonides, 4 Investigating deformation vs.

Work currently underway is dedicated to calibrating the diffusion of Ar in micas to quantitatively constrain their thermochonometric potential as a function of composition and mineral structure. Finally, we are currently expanding the lab capabilities for tracing heavy halogens via the determination of noble-gas isotopes produced by thermal-neutron capture on Cl, Br, and I.

The GSU K-Ar Geochronology laboratory published its first data ca W., Munsterman, D., , The implications of K-Ar glauconite dating of the Diest.

The temporal resolution of the stratigraphic record, the only account of the 4. As a consequence of the scientific pursuit to temporally dissect the geological record and decode Earth history, the NERC Argon Isotope Facility AIF was established through community demand nearly 20 years ago. For example, AIF establish dates and rates for the expansion of humans from Africa 1 , facilitates temporal integration of palaeoclimate signals to allow investigation of past global climate change 10 , determine timescales and frequencies of volcanic activity and super-eruptions to mitigate risk to the general populous 6 , reconstruct timescales of fluid-rock interaction with respect to the mineralisation of mineable resources 17 and generation of hydrocarbons As such, the Facility ethos is strongly aligned with the evolving NERC Strategy with output having direct societal and economic benefits to the UK and beyond.

However, as a versatile Facility that prides itself on being responsive to community demand, the AIF maintains scientific capability and intellectual leadership in deep time geochronology, for example, in studies of mass extinctions 16 , geochemical evolution of the atmosphere and oceans 14 15 , changes to ocean circulation 2 , dating of ancient volcanic eruptions 4 , geomagnetism and inner core processes 7 , resolution of the interplay between climate and tectonics 5.

The AIF is internationally established as a cutting-edge dating facility, due to the expertise and experience of AIF personnel, the quality of its scientific output peer-reviewed publications, PhD theses, conference presentations , technical innovation and training of chronology-literate scientists. Skip to main content. Search icon.


Isotopic dating is a critical tool in the earth sciences as it adds the essential dimension of time to a myriad of geological processes. Arguably the most versatile of all the modern dating methods uses the decay of an isotope of potassium into an isotope of argon. The most useful version of this dating method employs nuclear reactions to convert potassium, calcium and chlorine into a variety of argon isotopes. This so-called argon-argon dating method not only provides valuable time information but also gives us important chemical signals from the sample being analyzed.

Our Argon Geochronology Laboratory is equipped with two mass spectrometers This allows for better irradiation of the sample prior to dating. a Coherent 10W continuous Ar-ion laser and a custom-built, Berkeley-type, resistance furnace.

Ajoy K. Leonardo da Vinci, ca. Herein, I set out some simple guidelines to permit readers to assess the reliability of published ages. I illustrate the use of the techniques by looking at published age data for hotspot tracks in the Atlantic Ocean the Walvis Ridge , as well as newly published ages for the British Tertiary Igneous Province. In these experiments, a sample is heated in steps of increasing laboratory extraction temperature, until all the argon is released.

The resulting figure is called an age spectrum e. For unmetamorphosed igneous rocks, the latter would normally represent the crystallization age. This is the isochron technique see York , ; Roddick , ; Dalrymple et al. These tests are outlined herein. This work followed the first efforts Brooks et al.

What Is Argon Dating?

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