Contact an author. Update request. If you are one of the authors’ document, you have the possibility to update some of its metadata by using the editor form. Advanced search. Browse by More informations. Home Titles list Advancing U-Pb high-temperature thermochronology by combining single grain and intra-grain dating. Doctoral Thesis.
Skip to Content. James Metcalf. This automated He extraction and analysis system, optimized for reliably charac- terizing small gas amounts, is the heart of the CU TRaIL. Samples are loaded into an ultra-high vacuum chamber with a sapphire viewport attached to an automated stage. The evolved gas is then spiked with isotopically pure 3 He, cleaned with active gettering systems, and finally analyzed with a Pfeiffer Balzers QME quadrupole mass spectrometer.
for dating volcanic rocks by low-temperature thermochronology and for and U-Pb double datingJournal of Analytical Atomic Spectrometry.
Skip to content. Skip to navigation. In geology, thermochronologists investigate temperature-histories of rocks. One way to investigate cooling of rocks is Helium-dating. The radioactive isotopes Uranium, Uranium, Thorium and Samarium, which can be found in many minerals, decay via alpha-decay and thus produce alpha-particles 4 He atoms in the process. But only if the crystal or rock in which the crystal is found is below a certain temperature the so called ‘closure temperature’.
If the temperature is higher vibrations of the crystal lattice framework of atoms that make up the crystal allows the Helium to be lost through diffusion. So: if I measure both apatites and zircons found in the same rock with this method I will be able to tell when the rock was last at a temperature of 70 o C and o C – or in other words at depths of about 2km and 6km beneath the surface. The second method I am using uses spontaneous fission of U into two smaller atoms with masses between and This process creates a small fissure in the crystal lattice which is typically about micrometers long.
This tiny little ‘path of destruction’ can be made visible within the crystals by etching them. As with the Helium-method this techniques is also depending on temperature. If it is too hot vibrations of the crystal lattice will ‘heal’ the fission tracks by allowing atoms to jump back into their original position.
Fission-Track Thermochronology and its Application to Geology
The lab manager supports user training, sample processing, equipment maintenance, and planning and design in both labs. The He dating lab at the UofA supports training and analyses for diverse projects and workshops involving both external and internal PIs, undergraduate and graduate students, postdocs, and faculty. The lab conducts research in tectonic and geomorphic applications and experimental development and innovative applications of He dating.
Comparing with isotopic dating methods, luminescence thermochronometry has several advantages in determining the crustal uplift rates and.
It is widely believed that much of the SE Asian region has experienced large-scale uplift and erosion during the Cenozoic. In many places Cenozoic sedimentation is notable only by its absence, material presumed to be lost to the regions unusually deep sedimentary basins. Thermochronology provides a method of quantifying the magnitude and timing of rock uplift and erosion experienced across the region. By combining the results of analyses upon different minerals, and using different isotopic systems, it is thus possible to model the thermal history of an individual rock sample.
The SE Asia Research Group is actively involved in maintaining the rock crushing, sedimentary processing and mineral separation facilites required to go from sample to laboratory analyses. Click here for more information on the facilities. Much of our thermochronological work is done in conjunction with collaborators from other institutions. Granites, such as these boulders from the Malay Peninsula, provide a mineralogy ideal for thermochronology via multiple minerals.
In turn this information can provide vital information about the rates of uplift and erosion a region has experienced, providing clues to the driving forces and processes behind it, and the magnitude and timing of erosion from a given region. We have recently started to investigate the recent exhumation of the Se Asian region, beginning with the peninsular region of Malaysia. Max Webb et al. The history of Cenozoic magmatism and collision in NW New Guinea — New insights into the tectonic evolution of the northernmost margin of the Australian Plate.
Geochronology & Thermochronology
There are many isotopes and minerals that can be used for radiometric dating and therefore many different ways to perform a thermochronology study. Toggle navigation. Search open E I.
Low temperature thermochronometry (LTT) dating is a powerful tool in geoscience, used worldwide, to provide unique information on the.
This book is focused on the basics of applying thermochronology to geological and tectonic problems, with the emphasis on fission-track thermochronology. It is conceived for relatively new practitioners to thermochronology, as well as scientists experienced in the various methods. The book is structured in two parts. Part I is devoted to the fundamentals of the fission-track method, to its integration with other geochronologic methods, and to the basic principles of statistics for fission-track dating and sedimentology applied to detrital thermochronology.
Part I also includes the historical development of the technique and thoughts on future directions. Part II is devoted to the geological interpretation of the thermochronologic record. The thermal frame of reference and the different approaches for the interpretation of fission-track data within a geological framework of both basement and detrital studies are discussed in detail.
Facilities & Equipment
MARIN 1. Repeated analyses of fragments of Durango fluorapatite crystals yields an average age of This overlaps the long-term average of Durango fluorapatite measured in laboratories worldwide. The analysis of multiple single apatite crystals of a Precambrian basement sample from Serra do Mar, southeastern Brazil, yields an average He age
There may be opportunities to combine these with FT, U/Pb, and Ar dates too, through collaborations with co-instructors. Antarctichron/Chronothon is aimed.
Geochronology and thermochronology on detrital material provides unique constraints on sedimentary provenance, depositional ages, and orogenic evolution of source terrains. Typically these ages correspond to crystallization and exhumation or eruption ages, and their combination can be used to more confidently resolve candidate source terrains, establish maximum depositional ages, and constrain the thermal histories of orogenic source regions. We present examples from Mesozoic aeolian sandstones, both modern and Paleogene fluvial sediments, and active margin turbidite assemblages from the Cascadia and Kamchatka margins.
Important results include the fact that detritus from ancient orogens may dominate sediments thousands of kilometers away, crustal melting and exhumation appear to be spatially-temporally decoupled in at least two orogens, and first-cycle volcanic zircons older than depositional age are surprisingly rare in most settings except in the continental interior.
In the case of the Kamchatkan, and possibly Olympic, turbidites, zircon He ages are partially reset. User Name Password Sign In. Abstract Geochronology and thermochronology on detrital material provides unique constraints on sedimentary provenance, depositional ages, and orogenic evolution of source terrains. This Article doi:
Low temperature thermochronology from Knox Rift region
The most important of these methods are the U-Th-He 7. Thus, not only Pb content, but also the He content increases relative to U and Th through time, forming the basis of the U-Th-He chronometer: 7. It was Ernest Rutherford who first proposed that the U-Th-He decay scheme could be used as an absolute dating technique, making it the oldest radiometric chronometer.
This was correctly attributed to the volatile nature of the helium atom, which diffuses out of most minerals at low temperatures and therefore yields only minimum ages. Let C x,y,z be the He-concentration as a function of the spatial coordinates x, y and z.
Meanwhile, dating mineralizing age is another frontier topic in the world. The author successfully applied fission track thermochronology to determining the.
The signals from K-feldspar have provided multiple thermometers for thermochronological study. These two protocols were further applied to the samples from the Nujiang River valley and both explicitly demonstrated the thermal history of the samples. They are suitable for K-feldspar thermochronology study. They, as a parallelism of the previous studies of quartz TL and ITL signals, can provide multiple measures for a rock sample with the same thermal history in geo-thermochronological studies.
The regional erosion of an uplifted positive landform is always a step behind the instantaneous crust uplift. The exhumation or denudation rates recorded by this later regional erosion could only represent a prolonged average exhumation rate. For this reason, the better way to estimate the instantaneous crustal uplift rate is to study the erosional responses immediately following the uplift, such as river incision, glacial denudation, and normal faulting of a horst boundary.
Limited methods, including optically stimulated luminescence OSL dating, cosmogenic nuclide 10 Be dating, and Carbon dating, can be applied to estimate the rates of these incision and denudation within the last 10— ka. They are very sensitive to environmental conditions Herman et al. Comparing with isotopic dating methods, luminescence thermochronometry has several advantages in determining the crustal uplift rates and reconstructing the relief evolution.
Firstly, it has multiple thermochronometers which correspond to a group of closure temperatures Li and Li, ; Tang and Li, ; Qin et al.