Amphibolite facies metamorphism of the adjacent Vijayan Complex VC to the east is less well constrained but apparently somewhat younger Holzl et al. Additionally, the timing and nature of juxtaposition via thrusting of the HC above the VC is uncertain. The contact between the HC and VC, characterized by strong deformation, exotic tectonic slivers, migmatites, local serpentinite bodies, magnetite deposits, and gold mineralization is a major suture separating the Paleoproterozoic HC from the Grenville-age VC. West of the boundary granulite terrain , coarse garnet-sillimanite-graphite gneiss with 5 mm euhedral inclusion-rich garnets are locally sheared with garnet elongate in the foliation plane. Within the boundary zone, garnet- amphibole -biotite gneisses exhibit a strong mesoscopic fabric consisting of ribbon quartz and compositional layering. Microscopically, static annealing is prevalent.
Hydrothermal xenotime dates polymetallic mineralization at Abra to c. Abstract The Proterozoic Capricorn Orogen is a major tectonic zone that records the assembly and subsequent reworking of the West Australian Craton. Recent seismic transects across the orogen have identified major crustal structures, some of which are spatially associated with hydrothermal mineral deposits.
The sedimentary-rock-hosted Abra deposit, which is the largest base-metal accumulation in the Capricorn Orogen, is localized within the crust-cutting Lyons River—Quartzite Well fault zone. Robust radiometric dates for the timing of sediment deposition and hydrothermal mineralization are essential for understanding the geological history of this long-lived orogen and the processes that formed the ore deposits. Our results suggest that the Lyons River—Quartzite Well Fault, which is one of the principal structures in the Capricorn Orogen, has a long history of tectonic reactivation, spanning more than million years and involving crustal extension and sediment deposition, hydrothermal mineralization and multiple episodes of fluid flow.
Definition: The term “ore” is defined in the current study to describe a concentration of non-metallic, e.g., feldspar, or metallic minerals, e.g. spodumene, in pegmatitic rocks irrespective of its structure and position in the deposit which was or is currently mined for a profit.
Markley, a Steven R. Dunn, a Michael J. Jercinovic, b William H. Peck, c Michael L. Copyright remains with the author s or their institution s. Permission for reuse free in most cases can be obtained from RightsLink. Paper handled by Associate Editor Toby Rivers.
Canadian Journal of Earth Sciences
Decay routes[ edit ] The above uranium to lead decay routes occur via a series of alpha and beta decays, in which U with daughter nuclides undergo total eight alpha and six beta decays whereas U with daughters only experience seven alpha and four beta decays. The term U—Pb dating normally implies the coupled use of both decay schemes in the ‘concordia diagram’ see below. However, use of a single decay scheme usually U to Pb leads to the U—Pb isochron dating method, analogous to the rubidium—strontium dating method.
Finally, ages can also be determined from the U—Pb system by analysis of Pb isotope ratios alone. This is termed the lead—lead dating method. Clair Cameron Patterson , an American geochemist who pioneered studies of uranium—lead radiometric dating methods, is famous for having used it to obtain one of the earliest estimates of the age of the Earth.
ability to non-destructively date in situ REE-phosphate (monazite or xenotime) using the U-Th-Pb total dating technique (Montel et al., ; Chem. Geol. , ).
For more information on current and featured projects, go to http: Around 35 people from various research institutions, service providers and the mining industry attended the workshop from across Australia. Dr Mark Aylmore, recently appointed to take on the role of Applied Mineralogist in the JdLC, chaired the workshop that included presentations from: Thanks to all at Curtin and AXT staff who were involved in the workshop.
Special thanks goes to Petrina Beeton who organised the venue, catering and parking. With the success of this function it is anticipated further workshops on automated mineralogy will be held on an annual basis. He said reidite is important because it is only known to form in nature during meteorite impact events. All natural occurrences of reidite are associated with the transformation of the mineral zircon during the high pressures and temperatures associated with meteorite impact events.
However, the record of Precambrian impacts is poorly constrained due to the dynamic nature of plate tectonics, erosion and deposition of younger rocks, which may destroy or cover the evidence of ancient impacts.
Walther Kinetics of quartz dissolution at low temperature Chemical Geology, Vol. Brewster On circular polarization, as exhibited in the optical structure of amethyst, with remarks on the distribution of the colouring matter in that mineral Transactions of the Royal Society of Edinburgh, Vol. Wooster Growth and properties of large crystals of synthetic quartz Mineralogical Magazine, Vol.
In situ zircon and monazite dating tied to garnet crystallisation using trace element equilibrium partitioning allows for precise and robust estimates of the timing and .
Chris Marone Previous Speakers EarthScope speakers are selected based on their outstanding research accomplishments involving EarthScope as well as their abilities to engage a variety of audiences. Each speaker presents science-based lectures on their own EarthScope-related project, and their talks include an introduction highlighting broader EarthScope objectives and accomplishments. Her research focuses on using GPS and imaging geodesy to examine tectonic phenomena including long-term plate motions, the distribution of relative motion within plate boundary zones, earthquakes, and transient tectonic deformation as well as non-tectonic signals such as glacial isostatic adjustment and glacier dynamics.
Julie is PI of an ongoing EarthScope project using GPS to look at fault locking and possible transient tectonic signals along the eastern edge of the Alaska subduction zone. Continuously operating GPS sites, such as those in the Earthscope Plate Boundary Observatory PBO , have allowed us to reduce measurement uncertainty and capture transient events such as slow slip episodes, postseismic motion, and seasonal variations, providing a more complete image of the deformation field.
The deformation field here is complex, with contributions from long-term tectonic motion, earthquakes, postseismic deformation, slow slip episodes, seasonal snow loading, and the adjustment of the Earth to current and past ice loss. Tectonic models constrained by the long-term motion reveal a wide and heterogeneous plate boundary zone, a sharp contrast to textbook descriptions of the interaction between the Pacific and North American plates.
While there are major fault systems, such as the Fairweather-Queen Charlotte transform and the Aleutian megathrust, where most of the motion occurs along a main structure, there are also instances of relative plate motion being partitioned across multiple faults. Some areas appear to behave as rigid, rotating blocks while other areas are more aptly described as zones of distributed deformation.
Her research focuses on using seismic waves to constrain the structure of the mantle and crust to better understand dynamic processes inside the Earth. Karen joined the faculty at Brown in , following a B. At Brown Karen enjoys teaching courses that range from introductory physical geology to graduate level seismology.
Canadian Journal of Earth Sciences, , 51 6: Matrix grains in these rocks show complex internal textures consistent with extensive corrosion and overgrowths which are attributed to partial dissolution of earlier monazite in anatectic melt followed by new growth during melt crystallization or subsequent fluid infiltration. The new monazite data show the following: The wide age range of the main Grenvillian metamorphism suggests episodic growth of monazite over a wide time span, consistent with protracted residence of the host rocks under high-temperature conditions.
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Diplom-Geologe Date of birth: Research Fellowship of the Deutsche Forschungsgemeinschaft – Reconstruction of metamorphic P-T-t-d paths: Postdoc and Research Fellowships of the Deutsche Forschungsgemeinschaft. Deformation, metamorphism and petrography of the Austroalpine basement to the south of the Tauern Window, Eastern Alps. Korrespondent of the Geologische Bundesanstalt at Vienna. Appointment as Professor apl.
Memberships in Scientific Review Boards — Earth Sciences Panel for the evaluation of geoscientific base research in the Republic of Ireland — My research interest centers on metamorphic rocks.
Irka Hajdas, Susan Ivy-Ochs 9: Geochemical dataset of the Rhone River delta Lake Geneva sediments — disentangling human impacts from climate change 9: Holocene seismic activity of the Yavansu fault, western Turkey 9: Landscape evolution of the northern Alpine Foreland:
Examples of glass-like carbon from Gainey, Bay M31, and Topper. Quantities for selected markers are shown in Table 1 , and abundances of all markers are given in SI Table 4. Discussion Age of the YDB. Therefore, it appears that the Bay markers are identical to those found elsewhere in the YDB layers that date to Although the Bays have long been proposed as impact features, they have remained controversial, in part because of a perceived absence of ET-related materials.
Although we now report that Bay sediments contain impact-related markers, we cannot yet determine whether any Bays were or were not formed by the YD event. We investigated whether peaks in YDB markers might be attributed to terrestrial processes. The presence of identical markers found under such a wide range of conditions argues against formation by terrestrial processes and is consistent with an impact origin. We also examined whether the YDB might represent an interval of reduced deposition, allowing the accretion of interplanetary dust particles enriched in ET markers, such as Ir, Ni, and ET helium.
At Blackwater Draw, based on 24 calibrated 14C dates from Furthermore, abundances of microspherules and magnetic grains decrease with increasing distance from the Great Lakes region see SI Fig. Magnetic Microspherules and Grains. High concentrations of microspherules glass, clinopyroxene, spinel, or metallic are accepted as evidence for at least 11 older ET impact events Analysis suggests an ET origin, but because of high titanium Ti concentrations, the microspherules differ from typical meteoritic ones.
Symposium Sessions, Saturday November 19th
Advanced Search Abstract Paulsens is a mesothermal orogenic gold deposit located in the Wyloo Inlier on the southern margin of the Pilbara craton of Western Australia. Monazite and xenotime in the veins and from hydrothermally altered country rocks yield three distinct U-Pb dates of ca. Regional-scale hydrothermal events at ca.
Thus, in situ U-Pb dating of xenotime by LA-ICP-MS could provide accurate and precise ages, even for young samples. (2) Necessity of a reliable matrix-matched external standard. Our study also suggests that accurate ages of xenotime can be obtained in various ablation conditions, if .
It is easy to imagine diffusion in liquid phase as ink spreading in water. Solid-state diffusion of Pb is the net exchange of Pb in the solid mineral with the external environment, which is usually a fluid. In most of the cases, Pb is transported from the mineral to the fluid, resulting in Pb loss and thus age resetting. However, as the mineral cools and the crystal structure becomes more complete, the diffusions of parent and daughter isotopes slows down and finally become insignificant at a certain temperature.
Once the temperature falls below Tc, the system is closed and the clock starts counting. A Reaction ceased due to recrystallisation of precipitating phase dark orange. B Reaction ceased due to change in reaction system blue. Unlike solid-state diffusion, fluid-assisted dissolution-precipitation occurs below Tc. Interaction between mineral phase and coexisting fluid phase during geological events directly contributes to this process.
It is a chemical reaction driven by the system stabilisation from minimising Gibbs free energy.
Back-Scattered Electrons image of a zircon grain with outlined: While cooling ages and fission-track data allow well constraining exhumation paths, determining the duration of prograde metamorphism is not trivial. In situ zircon and monazite dating tied to garnet crystallisation using trace element equilibrium partitioning allows for precise and robust estimates of the timing and duration of prograde evolution from HP to UHP. Moreover, oxygen isotopes can be measured accurately at the microscale in the same mineral zones and provides insights into the fluid history.
The widely-studied coesite and pyrope-bearing whiteschists from the Dora Maira unit, Western Alps, underwent metamorphism to UHP conditions and subsequent rapid exhumation. They represent a metasomatised granite, the timing of the metasomatic event being debated.
Title. Records of the evolution of the Himalayan orogen from in situ Th-Pb ion microprobe dating of monazite: eastern Nepal and western Garhwal.
Volume 69 , September , Pages Review Pegmatites and aplites: Their genetic and applied ore geology Author links open overlay panel Harald G. Dill Show more https: Pegmatites are treated in this study together with aplitic rocks, which are compositionally similar to pegmatites but strikingly different from them by their fine-grained texture. Rocks of the granitic suite take an intermediate position between the two and, locally, they are transitional into both end-member types, emphasized in the denomination by supplements such as aplite granite or pegmatitic granite.
A similar scenario can be reported for syenitic and, less frequently, for granodioritic through dioritic rocks which are found to be associated in time and space with pegmatites and aplites. Pegmatites sensu stricto are found as immigrations into environments different from their birthplace where they were trapped in structures providing the accommodation space necessary for their emplacement and sealed off by impervious roof rocks.
In principle, granites and pegmatites are two sides of the same coin, both are undergoing mobilization and migration; the granite mirrors diffusion and dissemination, the pegmatite reflects trapping and concentration. Fractionation and separation can be recognized in the petroleum as well as in the pegmatite—granite systems.