Simultaneous acquisition of isotope compositions and parent/daughter ratios by non-isotope dilution-mode plasma ionisation muti-colector mass spectrometry (PIMMS)

Holland, Grenville; Tanner, Scott D.; Nowell, Geoff; Parrish, Randall R.

doi:10.1039/9781847551696-00298

Cited by 21 publications

(19 citation statements)

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“…Yb ratio calibrated for Hf mass bias using Yb-doped JMC475 solutions (c.f. Nowell and Parrish, 2001). Additionally, Plešovice and Yb-doped synthetic zircons (Zr141 and Zr142; Fisher et al, 2011) were analysed to assess the accuracy of the Hf ratio normalization and Yb ratio correction, respectively.…”

Section: Laser Ablation Zircon Hf Isotopesmentioning

confidence: 99%

Geochronology of the central Tanzania Craton and its southern and eastern orogenic margins

Thomas

Spencer

Bushi³

et al. 2016

Precambrian Research

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Geological mapping and zircon U-Pb/Hf isotope data from 35 samples from the central Tanzania Craton and surrounding orogenic belts to the south and east allow a revised model of Precambrian crustal evolution of this part of East Africa. The geochronology of two studied segments of the craton shows them to be essentially the same, suggesting that they form a contiguous crustal section dominated by granitoid plutons. The oldest orthogneisses are dated at ca. 2820 Ma (Dodoma Suite) and the youngest alkaline syenite plutons at ca. 2610 Ma (Singida Suite). Plutonism was interrupted by a period of deposition of volcano-sedimentary rocks metamorphosed to greenschist facies, directly dated by a pyroclastic metavolcanic rock which gave an age of ca. 2725 Ma. This is supported by detrital zircons from psammitic metasedimentary rocks, which indicate a maximum depositional age of ca. 2740 Ma, with additional detrital sources 2820 and 2940 Ma. Thus, 200 Ma of episodic magmatism in this part of the Tanzania Craton was punctuated by a period of uplift, exhumation, erosion and clastic sedimentation/volcanism, followed by burial and renewed granitic to syenitic magmatism.In eastern Tanzania (Handeni block), in the heart of the East African Orogen, all the dated orthogneisses and charnockites (apart from those of the overthrust Neoproterozoic granulite nappes), have Neoarchaean protolith ages within a narrow range between 2710 and 2630 Ma, identical to (but more restricted than) the ages of the Singida Suite. They show evidence of Ediacaran "Pan-African" isotopic disturbance, but this is poorly defined. In contrast, granulite samples from the Wami Complex nappe were dated at ca. 605 and ca. 675 Ma, coeval with previous dates of the "Eastern Granulites" of eastern Tanzania and granulite nappes of adjacent NE Mozambique. To the south of the Tanzania Craton, samples of orthogneiss from the northern part of the Lupa area were dated at ca. 2730 Ma and clearly belong to the Tanzania Craton. However, granitoid samples from the southern part of the Lupa "block" have Palaeoproterozoic (Ubendian) intrusive ages of ca. 1920 Ma. Outcrops further south, at the northern tip of Lake Malawi, mark the SE continuation of the Ubendian belt, albeit with slightly younger ages of igneous rocks (ca. 1870-1900 Ma) which provide a link with the Ponte Messuli Complex, along strike to the SE in northern Mozambique.In SW Tanzania, rocks from the Mgazini area gave Ubendian protolith ages of ca. 1980-1800 Ma, but these rocks underwent Late Mesoproterozoic high-grade metamorphism between 1015 and 1040 Ma. One granitoid gave a crystallisation age of ca. 1080 Ma correlating with known Mesoproterozoic crust to the east in SE Tanzania and NE Mozambique. However, while the crust in the Mgazini area was clearly one of original Ubendian age, reworked and intruded by granitoids at ca. 1 Ga, the crust of SE Tanzania is a mixed Mesoproterozoic terrane and a continuation from NE Mozambique. Hence the Mgazini area lies at the edge of the Ubendian belt which was re...

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Section: Laser Ablation Zircon Hf Isotopesmentioning

confidence: 99%

Geochronology of the central Tanzania Craton and its southern and eastern orogenic margins

Thomas

Spencer

Bushi³

et al. 2016

Precambrian Research

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“…The residue remaining after ion exchange separation of U and Pb, was evaporated to incipient dryness and redissolved in 2% HNO 3 -0.1M HF ready for Hf isotope analysis by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) following a procedure modified after Nowell & Parrish (2000). A Thermo-Elemental Axiom MC-ICP-MS was used, coupled to a Cetac Technologies Aridus desolvating nebuliser.…”

Section: Geochronology and Isotope Geochemistrymentioning

confidence: 99%

“…A Thermo-Elemental Axiom MC-ICP-MS was used, coupled to a Cetac Technologies Aridus desolvating nebuliser. Corrections for Lu and Yb isobaric interferences were determined and applied following Nowell & Parrish (2000). Data were normalised to equivalent washes of the 91500 zircon standard prepared at the same time, according to 176 Hf/ 177 Hf and 176 Lu/ 177 Hf values of 0.282284 and 0.000288 (Wiedenbeck et al, 1995) respectively.…”

Section: Geochronology and Isotope Geochemistrymentioning

confidence: 99%

Two Mesoarchaean terranes in the Reguibat shield of NW Mauritania

Key

Loughlin

Gillespie

et al. 2008

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“…Our main rationale is that the positive ions produced by the plasma source at such high masses generally have relatively simple mass spectra that are less likely to be significantly influenced by molecular ions. In addition, although interfering isobaric elemental ions are efficiently generated by the plasma, it has been shown that such interferences can be accurately corrected for (e.g., Nowell and Parrish, 2002;. Although previous publications have outlined the use of MC-ICP-MS for the analysis of Os isotope measurements, these studies have primarily addressed the measurement of 187 Os/ 188 Os ratios (e.g., Schoenberg et al, 2000; N.J. Pearson et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Precise and accurate 186Os/188Os and 187Os/188Os measurements by multi-collector plasma ionisation mass spectrometry (MC-ICP-MS) part I: Solution analyses

et al. 2008

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We present new high precision Os isotope data obtained by solution-mode MC-ICP-MS for 4 different Os isotope reference materials and compare the data to that obtained by the N-TIMS method. Mass fractionation effects for MC-ICP-MS are evaluated and we demonstrate excellent adherence to the exponential law. An improved and robust method for the derivation of interfering element isotope ratios is presented and evaluated via analysis of solutions with widely varying interfering element/analyte ratios. We show experiments that illustrate the extent of memory with a conventional solution introduction system and establish a protocol that reduces washout time and memory effects to the same level as those common for other elements typically analysed at high precision by MC-ICP-MS.

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Simultaneous acquisition of isotope compositions and parent/daughter ratios by non-isotope dilution-mode plasma ionisation muti-colector mass spectrometry (PIMMS)

Cited by 21 publications

References 0 publications

Geochronology of the central Tanzania Craton and its southern and eastern orogenic margins

Geochronology of the central Tanzania Craton and its southern and eastern orogenic margins

Two Mesoarchaean terranes in the Reguibat shield of NW Mauritania

Precise and accurate 186Os/188Os and 187Os/188Os measurements by multi-collector plasma ionisation mass spectrometry (MC-ICP-MS) part I: Solution analyses

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