Earth’s youngest exposed granite and its tectonic implications: the 10–0.8 Ma Kurobegawa Granite
Professor Bill Compston, isotope geochemist
It is an indisputable fact that geochronology plays a vital role in geosciences. However, the application and relevant research of experimental results were constrained because traditional dating methods required dissolving samples in chemical reagent, which made it hard for researchers to obtain all information of the structurally-complex zircon.
With an irreplaceable advantage in testing ages of zircon, SHRIMP II ushered in a new age of micro-area and in situ analysis of zircon chronology, producing far-reaching influence worldwide. Following the principle of emphasizing key points, strengthening integration, optimizing allocation and scientific utilization, Beijing SHRIMP Center is the service lab featuring on open research established to meet the demand of the development of geoscience China.
Provenance of north Gondwana Cambrian–Ordovician sandstone: U–Pb SHRIMP dating of detrital zircons from Israel and Jordan – Volume Issue 3 – K.
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.
Radioactive decay is a natural process and comes from the atomic nucleus becoming unstable and releasing bits and pieces.
Rutile U-Pb Geochronology
The Jinjiang basic-intermediate dike swarms from southeast Fujian are further divided into two groups. The early-stage dike consist of hornblende diabases. Two groups of dike intruded always along joints of the late Mesozoic granitic gneiss. Geochemically, they are calc-alkaline series of basalt to andesite compositions with MgO varying from 5. The Jinjiang basic-intermediate dike rocks have limited ranges of I sr values from 0.
Other rutile dating methods. Rutile can be analyzed via TIMS and LA-ICPMS. TIMS provides very precise ages within ~%. However, TIMS destroys the grain.
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.
Background of Platform
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. The secondary ion, which is sputtered from sample surface by a focused ion beam primary ion beam in high vacuum, is analyzed.
福建晋江中-基性岩墙群的锆石SHRIMP U-Pb定年和岩石地球化学 along EW direction and are dated at 90 ± 2Ma by the zircon SHRIMP U-Pb method.
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 the dating of opals with ages ranging from several tens of thousand years to millions of years. The major advantages of the technique, compared to the conventional thermal ionisation mass spectrometry TIMS , are the high spatial resolution???
There are two major limitations to this method, determined by both current level of development of ion probes and understanding of ion sputtering processes. First, sufficient secondary ion beam intensities can only be obtained for opal samples with U concentrations in excess of??? However, this restriction still permits dating of a large variety of opals. Nevertheless, an assumption of similar behaviour of standard and unknown opals under similar analytical conditions allowed successful determination of ages with precisions of???
All rights reserved. The Santa Ba?? It comprises three highly fractionated metaluminous to peraluminous within-plate A-type granite units emplaced in older medium-grade metamorphic rocks. Sn-mineralization is closely associated with the late-stage unit. U-Pb monazite conventional dating of the early-stage Serra do Cicero facies and late-stage Serra Azul facies yielded ages of ??
Conventional multigrain U-Pb isotope analyses of zircon demonstrate isotopic disturbance discordance and the preservation of inherited older zircons of several different ages and thus yield little about the ages of Sn-granite magmatism. The textural complexity of the zircon crystals of the Santa Ba??
Shrimp Dating – Sensitive high-resolution ion microprobe
For geological purposes, this is taken as one year. Another slideshare of expressing this is the half-life period given the symbol T. The half-life is the time it takes for half of the parent atoms to decay. The relationship between the two is: Many different radioactive isotopes and techniques are used for dating.
the discordia which ionises the shrimp and releases the isotopes. This is a common dating method mainly used by archaeologists, as it can only date.
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?
In this paper, we review the methodology associated with in-situ apatite dating and.
Such a sophisticated ion probe, which can attain a high sensitivity at a high mass resolution, based on a double focusing high mass-resolution spectrometer, designed by Matsuda , was constructed at the Australian National University. Since its installation, our focus has been on the in-situ U—Pb dating of the mineral apatite, as well as zircon, which is a more common U-bearing mineral.
In this paper, we review the methodology associated with in-situ apatite dating and our contribution to Earth and Planetary Science over the past 16 years. Since the monumental studies reported in , 1 an enormous amount of work related to the Pb—Pb dating of meteorites has been reported via the use of TIMS Thermal Ionization Mass Spectrometry. After this, following cleaning with ethanol, to minimize surface contaminating Pb, the thin section was gold-coated to prevent a charge from developing on the sample surface during SHRIMP analyses.
The positive secondary ions were thereby extracted and detected on a single electron multiplier by peak switching. A similar equation also describes the U—Pb secondary ion emission data from other minerals such as monazite, titanite, baddeleyite, rutile. In the case of ion microprobe U—Pb zircon dating, the expected initial lead based on the U—Pb evolution model is subtracted from the observed lead signals. Moreover, it should be noted that it would be a demerit where only one or two in some cases age information data sets from a number of apatite grains are obtained by an isochron method in comparison with the conventional calibration for zircon.
The crucial advantages of this method are that it is not necessary to know the isotopic composition of common Pb in contrast to the conventional Concordia diagram, and that both U and U decay schemes are used simultaneously, yielding a smaller justifiable age uncertainty for the case of U—Pb systematics. In this case, both the upper and lower intercept ages are geologically valid, corresponding to a formation age and an alteration age, respectively.
Although the upper intercept age is not a geological age in case II, the lower intercept ages are geochronologically valid in both cases I and II.