Arafura Basin. Bremer Sub-basin study. Nitrogen in estuaries. Diatoms and water quality. Geochronology boost. Wind risk in Australia.
Professor William Bill Compston is a renowned geophysicist who began his research career fingerprinting and dating rocks at the University of Western Australia before moving to the Research School of Earth Sciences at the Australian National University. Bill, you were born in in Western Australia, a state founded on its mineral wealth, and your mother came from the WA goldfields.
But I believe your connection to geology and minerals goes back even further.
dating of monazite using a field–emission electron probe microanalyzer (FE–EPMA) equipped with This problem has been overcome by a new interference correction method using Cooma Granodiorite was dated by SHRIMP as ±.
Always quote above citation when using data! You can download the citation in several formats below. High- to very-high-grade migmatitic basement rocks of the Wilson Hills area in northwestern Oates Land Antarctica form part of a low-pressure high-temperature belt located at the western inboard side of the Ross-orogenic Wilson Terrane. Zircon, and in part monazite, from four very-high grade migmatites migmatitic gneisses to diatexites and zircon from two undeformed granitic dykes from a central granulite-facies zone of the basement complex were dated by the SHRIMP U-Pb method in order to constrain the timing of metamorphic and related igneous processes and to identify possible age inheritance.
There is only minor evidence of age inheritance in zircons of these four samples. Zircon from two other samples metatexite, posttectonic granitic dyke gave scattered PbU ages. In the metatexite, a major detrital contribution from – Ma old source rocks can be identified. The new age data support the model that granulite- to high-amphibolite-facies metamorphism and related igneous processes in basement rocks of northwestern Oates Land were confined to a relatively short period of time of Late Cambrian to early Ordovican age.
An age of approximately Ma is estimated for the Ross-orogenic granulite-facies metamorphism from consistent ages of monazite from two migmatites and of the older zircon age population in one metatexite. The presence of inherited zircon components of latest Neoproterozoic to Cambrian age indicates that the high- to very-grade migmatitic basement in northwestern Oates Land originated from clastic series of Cambrian age and, therefore, may well represent the deeper-crustal equivalent of lower-grade metasedimentary series of the Wilson Terrane.
Very old rocks and a shrimp!
Radioactive dating is a method of dating rocks and minerals using radioactive isotopes. This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Over naturally-occurring isotopes are known. Some do not change with time and form stable isotopes i. The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.
dating methods, but disparate results were obtained, even by the same method (Table 1). Until now, the ore-forming age of the HQL deposits has not been well.
Jelinek I ; Artur C. Bastos-Neto I ; Jayme A. McNaughton III. These ages were obtained by U-Pb isotopic determinations with the sensitive high mass-resolution ion microprobe on igneous zircons from Pedras Grandes Suite in Santa Catarina State. Euhedral zircons remained unaltered close to a fluorite vein deposited at ? C or more.
Sensitive High Resolution Ion Micro Probe Facility
SHRIMP is an analytical instrument that the Australian National University ANU has begun to develop since , and secondary ion mass spectrometry to analyze the secondary ions generated by irradiating a primary ion beam on the sample surface. SHRIMP has specialized in carrying out the analysis of minute areas by particular focused ion beam, and is referred to as “ion microprobe “. High secondary ion detection sensitivity and high mass and spatial resolution enable to produce reliable data worldwide.
The secondary ion mass spectrometry is a technique of analysis in microscale of sample surface.
U-Pb and U-series analyses of four U-rich opal samples using sensitive high-resolution ion microprobe (SHRIMP) demonstrate the potential of this technique for.
We implement several procedures that help combat these analytical issues. Pb and U. To decrease molecular interferences at Pb peaks and increase the signal:noise ratio, we also use the energy filter to only accept high-energy ions into the collector. Because common lead and the amount of molecular interferences vary by sample, energy filtering is not always used. Grey shaded area outlined in black represents published age of standard measured by TIMS Luvizotto et al.
Individual rutile U-Pb analyses typically take minutes per spot.
Background of Platform
Methods recently advanced for discrimination on the genesis of metamorphic zircon, such as analysis of mineral inclusions and trace elements, provide us powerful means to distinguish zircon overgrowth during high-pressure metamorphism. No inherited core was identified in the analyzed zircons by means of cathodoluminescence images. The occurrence of high-pressure metamorphic mineral inclusions in zircon, such as garnet, omphacite, rutile, and the flat HREE pattern in zircon indicate that the zircon formed at high-pressure metamorphic conditions.
Therefore, a weighted average U-Pb age of This is a preview of subscription content, log in to check access.
Preparing zircons for dating is a long, tedious process which involves many in another lab at the GSC, which also dates rocks, but with a different method.
Fletcher, Birger Rasmussen , Neal Mcnaughton. N2 – SHRIMP Sensitive High-Resolution Ion MicroProbe analytical procedures have been developed to enable dating of the small, early diagenetic xenotime overgrowths that commonly occur on zircons in siliciclastic sedimentary rocks. The method will be particularly useful in Precambrian terranes, where diagenetic xenotime dating could play a role equivalent to biostratigraphic dating in the Phanerozoic.
In contrast, greenschist-facies metasediments of the Archaean Witwatersrand Basin, South Africa, contain both authigenic and alteration xenotime that record a complex history of growth from early diagenesis to the last major thermal event to affect the basin. Overview Fingerprint. Abstract SHRIMP Sensitive High-Resolution Ion MicroProbe analytical procedures have been developed to enable dating of the small, early diagenetic xenotime overgrowths that commonly occur on zircons in siliciclastic sedimentary rocks.
Access to Document Australian Journal of Earth Sciences , 47 5 , Fletcher, I. In: Australian Journal of Earth Sciences. U2 – Australian Journal of Earth Sciences.
We specialise in precise, accurate, high spatial resolution, uranium-thorium-lead geochronology of zircon, monazite, xenotime, titanite, allanite, columbite-tantalite, baddeleyite, rutile, cassiterite, opal, apatite, perovskite, gadolinite, chevkinite, ilmenorutile, uraninite and zirconite. A single collector ion probe doing in-situ U-Th-Pb age dating of zircon, monazite, xenotime and titanite in grain separates and thin sections.
Just a few of the application areas are listed below. Representative publications: How long-lived is ultrahigh temperature UHT metamorphism? Constraints from zircon and monazite geochronology in the Eastern Ghats orogenic belt, India.
In this study, the SHRIMP zircon U-Pb dating method has been adopted for six plutons, Ledong, Longhuashan,. Dawozi, Zhaidi, Baiyun and Jiangnan, in the.
Stella Poma 1 , Eduardo O. Mcnaughton curtin. Two episodes of different age and genesis have been identified. Hf isotope signature of the units indicates mantle sources as well as crustal components. The tectonic setting and age of the Gondwanan magmatism in NW Argentina allow to differentiate: a. Permian intra-plate magmatism developed under similar conditions to the upper section of the Choiyoi magmatism exposed in the Frontal Cordillera and San Rafael Block, Argentina; b.
Triassic magmatism belonging to a poorly known subduction-related magmatic arc segment of mostly NS trend with evidence of porphyry type mineralization in Chile, allowing to extend this metallotect into Argentina. It comprises epizonal plutonic and volcanic rocks, the latter including pyroclastic facies. The Cordillera Frontal outcrops are the most voluminous and have been the subject of study over the last 40 years e. This region is characterized by felsic rocks with subordinated basic and mesosilicic rocks.
Isolated Permian-Triassic plutons have been recognized in the Puna region of Salta province, Argentina, suggesting that the magmatic event reached that latitude Zappettini and Blasco, ; Page and Zappettini, ; Poma et al. The aim of this paper is to contribute to the knowledge of the Gondwanan magmatism through the presentation and interpretation of chemical and isotopic data of previously poorly known units that represent the northernmost outcrops identified in Argentina.
We present new zircon U-Pb SHRIMP and Hf isotope data and we explore the nature and characteristics of the magma sources to better constrain a petrogenetic model and characterize the crustal components of the Puna region.