Brian J. Fryer

ICP-MS — A powerful tool for high-precision trace-element analysis in Earth sciences: Evidence from analysis of selected U.S.G.S. reference samples

Abstract Inductively coupled plasma-mass spectrometry (ICP-MS) is a powerful analytical technique, with considerable application to geochemistry. In this paper, we demonstrate the power of ICP-MS as a tool in petrogenetic studies. Data for 28 elements in seven U.S.G.S. basalt and andesite reference samples (AGV- 1 , BCR- 1 , BHVO- 1 , BIR- 1 , DNC- 1 , W- 1 and W- 2 ) are presented. Accuracy and precision (standard deviation) for 26 of these elements is either excellent ( A detailed description of the ICP-MS technique we have developed is given. A simple HF-HNO 3 dissolution in screwtop Teflon® bombs was used for sample preparation. ICP-MS instrumental sensitivity was measured by external solutions, with surrogate calibration for 4 elements. Matrix correction was made by use of standard addition. Naturally occurring internal standards (Rb, Y, Ce and Pb) were used to correct for instrumental drift between sample and spiked-sample measurements. We report data for the elements: Li, Cs, Rb, Sr, Ba, Zr, Hf, Nb, Ta, Y, Sc, U, Th, Pb and all 14 of the REE. In addition, the procedure acquired data for Be, Mo, W, Tl and Bi. Many elements in this array are crucial for the evaluation of petrogenetic models and source tracing. Herein lies the real power of ICP-MS — one technique, one dissolution, small sample size, good limits of detection, good to excellent accuracy and good precision for many geochemically important elements.

Inductively coupled plasma-mass spectrometric analysis of geological samples: A critical evaluation based on case studies

Inductively coupled plasma-mass spectrometry (ICP-MS) is a relatively new and promising analytical technique, with the potential to be an excellent analytical tool in earth sciences. In this paper, we provide an overview of the use of ICP-MS in earth sciences, based on our experience with this technique over the last five years. This paper discusses a variety of calibration techniques, chemical separation and preparation procedures, followed by various data acquisition protocols to determine a variety of elements in samples ranging from mineral separates, Fe formations, to ultramafics. The procedures evaluated include methods for the determination of 33 trace elements using a modified standard addition procedure and its adaptation to mg quantities of mineral separates; a procedure for the determination of Y, all the rare-earth elements (REE), and Th using a Na2O2 sinter, with quantification using internal standards; and techniques for the determination of very low-level REE in ultramafic samples using ion-exchange concentration. To solve dissolution difficulties involved in Fe formation samples a procedure using oxalic acid to complex the Fe is demonstrated on the reference material IF-G. Precious-metal determination of all the Pt-group elements along with Re and Au is summarised. The application of ICP-MS to isotope ratios is discussed with reference to the determination of 147Sm144Nd and Pb-Th-U isotope ratios. From the results of these studies, it is clear that the future for ICP-MS in earth sciences is very promising.

Determination of partition coefficients for trace elements in high pressure-temperature experimental run products by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS)

Abstract This paper reports the first trace element partition coefficients measured on experimentally produced products (clinopyroxene, garnet, rutile, and glass) by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS). A 266 nm (UV) laser microprobe was used to improve ablation characteristics and to achieve a fourfold reduction in ablation pit diameter compared to the previously used 1064 nm beam. Results are compared with PIXE analyses on the same experimental products, and literature values, where available, for similar systems, and include the first simultaneously measured partition coefficients for Zr, Nb, and Ta between rutile and glass. Advantages of the LAM technique include rapid results and simultaneous determination of a wide range of major and trace elements, thus ensuring sampling integrity through time-resolved analysis of the sampled material.

Trace element partition coefficients for clinopyroxene and phlogopite in an alkaline lamprophyre from Newfoundland by LAM-ICP-MS

Mineral/rock matrix partition coefficients have been determined for clinopyroxene (Cpx) and phlogopite from a Mesozoic alkaline lamprophyre from Newfoundland, Canada, by Laser Ablation Microprobe (LAM-ICP-MS). Values for twenty-one elements were obtained for Cpx, whereas only eleven were possible for phlogopite due to REE abundances below detection limits ( 1 ppm). Ablation pits of 40–50 μm diameter enabled investigation of zonation in phenocryst phases. In general, phenocrysts exhibit little trace element zonation except in the outermost overgrowths of Cpx. In these, a fourfold to fivefold increase in many trace element abundances correlates strongly with increasing Ti and Al contents, in agreement with recent experimental studies. Only Li shows appreciable zonation in phlogopite, being enriched in the rims. Comparison of the partition coefficients determined by in-situ laser analysis with those obtained from apparently pure mineral separates by solution ICP-MS indicates that, for several elements, considerable differences exist, e.g., DBa 0.0006 vs. 0.0255. These differences are attributable to the inclusion of trace element-rich overgrowths, and zones of trace element enrichment and micro-inclusions, in addition to the possibility of small amounts of matrix or glass (1–2%) in the nominally clean clinopyroxene mineral separates. Partition coefficients for Cpx are lower than most published values for basaltic rocks, but are comparable to experimental values for basalt determined by SIMS. Comparison with experimental values from lamproite discounts a strong bulk compositional effect, so that the discrepancy with earlier values for basalt should probably be attributed to problems with mineral separates, emphasizing the need for high quality partitioning determinations with in-situ microbeam methods. The phlogopite data extend considerably the published range; the new values are also generally lower than published values, although the discrepancy here may be due to bulk compositional effects, as many published values are from more silicic systems. The lamprophyre values are within the range of sparse experimentally determined values.

Determination of the precious metals in geological materials by inductively coupled plasma-mass spectrometry (ICP-MS) with nickel sulphide fire-assay collection and tellurium coprecipitation

Abstract A procedure has been developed for the routine determination of the precious metals (Ru, Rh, Pd, Os, Ir, Pt and Au) in geological materials using inductively coupled plasma-mass spectrometry (ICP-MS). The precious metals were isolated using a combination of the nickel sulphide fire-assay and Te coprecipitation procedures and quantified by ICP-MS using two internal standards to correct for matrix and drift effects; Cd for the light elements (Ru, Rh and Pd) and Tl for the heavy elements (Os, Ir, Pt and Au). Over 8 analytical runs, mean instrumental detection limits for a 15-g sample ranged from 0.07 ppb for Ir to 0.7 ppb for Au. Long-term mean reagent blank concentrations were Data from the analysis of Indian Ocean basalts demonstrate the ability of the procedure to make useful determinations at baseline levels in rocks for the full set of elements. Thus, the procedures described here extend the use of PGE geochemistry from mineral deposit studies to normal basaltic and mantle systems.

The role of fluids in the formation and subsequent development of early continental crust

AbstractA petrogenetic model is developed to explain the evolution and geochemical character of granitic rocks in early Archean (pre 3.6 Gyr) continental crust taking into account the following important geological constraints, viz.:1.High geothermal gradients (probably in excess of 90 ° C/km) and resulting widespread granulite facies metamorphism even at relatively shallow depths2.The fractionation of certain major and trace elements under granulite facies conditions3.The composition and geochemical behaviour of fluids which emanate from or pass through terrains undergoing granulite facies metamorphism viz. carbonic fluids containing significant amounts of SO2 and halogens. In this model tonalitic and trondhjemitic intrusives are regarded as being derived dominantly by partial melting of mafic granulite. The ubiquitous potassic granites, which typical post-date sodic plutonic activity are interpreted to be anatectic melts generated under granulite or amphibolite facies conditions from the previously formed ‘plagiogranites’. The presence of a postulated granulite facies source area for Archean tonalitic rocks, and the geochemical character of fluids which accompany metamorphism under such conditions explains the HREE geochemistry of these suites and casts doubt on the validity of applying currently used trace element fractional melting or crystallization models to these terrains. Similarly it suggests that petrogenetic interpretations based on Sr and Pb isotopic systems must be reevaluated because of the extreme mobility of both parent and daughter elements under granulite facies conditions.

Volatile control of contrasting trace element distributions in peralkaline granitic and volcanic rocks

Anomalous enrichments of Zr (>500 ppm), Zn (> 100 ppm), Nb (>25 ppm), Y (>60 ppm), Th (>20 pm), U (> 5 ppm), LREE (>230 ppm) and HREE (>35ppm), and high Rb/Sr (>5) characterize peralkaline granites, in contrast to their peraluminous and calc-alkaline equivalents. Within the peralkaline suite, comenditic and pantelleritic volcanics exhibit two- to five-fold increases in the concentrations of these trace elements over comagmatic granites. These cannot be explained by crystal- liquid fractionation processes, and require the evolution of a sodium-enriched fluid. Corresponding trace element increases in the granites in areas of alkali metasomatism support this argument, and reflect the partial confinement of this volatile phase within the high-level magma chambers. REE studies in particular might eventually allow an evaluation of the role of Cl− versus F− and CO3-complexing in the evolution of the volatile fluid.

The application of laser ablation microprobe−inductively coupled plasma−mass spectrometry (LAM-ICP-MS) to in situ (U)-Pb geochronology

Abstract The direct dating of single pitchblende and zircon grains is reported, using a laser ablation microprobe (LAM) which has been coupled to a commercial inductively coupled plasma-mass spectrometer (ICP-MS). The system has been designed for micro sampling minerals in petrographic sections. Major advantages of this technique, compared to other in situ dating techniques, are the: (1) separation of the sampling process from the excitation (dissociation and ionization) processes; (2) minimal complex and variable ion species in the mass analyzer; (3) ability to monitor and adjust the analysis characteristics during ablation; (4) ease of isolation and analysis of the isotopic data at all stages during an ablation sampling; (5) ability to date diverse materials; and (6) relatively low capital costs. Direct dating of uranium-rich phases such as pitchblende is rapid, precise and requires no chemical pretreatment. The ability to analyze small areas (diameters of 20–30 μm) facilitates studies on the timing of primary and secondary U mineralization. Micro sampling of an individual pitchblende grain from the complex Collins Bay uranium deposit in Saskatchewan, Canada, illustrates this new techniques potential and the equivalence of conventional and LAM-ICP-MS age determinations. Analysis of 100-μm-diameter late Archean zircons further demonstrates that LAM-ICP-MS has the potential to become a rival of competing techniques for regional reconnaissance and sediment provenance age studies. In addition, this technique is uniquely capable of providing simultaneous monitoring of chemical and isotopic homogeneity during analysis of accessory minerals used in UPb geochronology.

Petrogenesis and paleotectonic history of the Wild Bight Group, an Ordovician rifted island arc in central Newfoundland

The Wild Bight Group (WBG) is a sequence of early and middle Ordovician volcanic, subvolcanic and epiclastic rocks, part of the Dunnage Tectonostratigraphic Zone of the Newfoundland Appalachians. A detailed geochemical and Nd-isotopic study of the volcanic and subvolcanic rocks has been carried out to determine the geochemical characteristics of the rocks, interpret their palcotectonic environments and constrain their petrogenetic history. The lower and central stratigraphic levels of the WBG contain mafic volcanic rocks with island-arc geochemical signatures, including LREE-enriched are tholeiites with εNd(t)=-0.1 to +2.2 (type A-I), LREE-depleted arc tholeiites with εNd(t)=+5.6 to +7.1 (type A-II) and an unusual suite of strongly incompatible-element depleted tholeiites in which εNd(t) ranges from-0.9 to +4.6 and is negatively correlated with147Sm/144Nd (type A-III). High-silica, low-K rhyolites occur locally in the central part of the stratigraphy, associated with mafic rocks of arc affinity, and have εNd(t)=+4.7 to +5.4. The upper stratigraphic levels of the WBG dominantly contain rocks with non-arc geochemical signatures, including alkalic basalts with εNd(t)=+4.6 to +5.5 (type N-I), strongly LREE- and incompatible element-enriched tholeiites that are transitional between alkalic and non-alkalic rocks with εNd(t)=+4.4 to +7.0 (type N-II) and rocks with flat to slightly LREE-enriched patterns and εNd(t)=+5.1 to +7.4 (type N-III). Rocks with non-arc and arc signatures are locally interbedded near the stratigraphic type of the WBG. Nd-isotopic data in the type A-I and A-II rocks are generally compatible with mixing/partial melting models involving depleted mantle, variably contaminated by a subducted crustally-derived sediment. The petrogenesis of type A-III rocks must involve source mixing and multi-stage partial melting, but the details are not clear. The geochemistry and Nd isotope data for types N-I, N-II and N-III rocks are compatible with petrogenetic models involving variable partial melting of a source similar to that postulated for modern oceanic island basalts. Comparison of the WBG with modern analogues suggests a 3-stage developmental model: stage 1) island-arc volcanism (eruption of type mafic volcancs); stage 2) arc-rifting (continued eruption of type A-I, A-I, eruption of types A-II and A-III mafic volcanics and high-silica, low-K rhyolites); and stage 3) back-arc basin volcanism (continued minor eruption of type A-I basalts, eruption of types N-I, N-II, N-III basalts). Stages 1 and 2 volcanism involved partial melting of subduction contaminated mantle, while stage 3 volcanism utilized depleted-mantle sources not affected by the subducting slab. This model provides a basis for interpreting coeval sequences in central Newfoundland and a comparative framework for some early Paleozoic oceanic volcanic sequences elsewhere in the Appalachian orogen.

River-plume use during the pelagic larval stage benefits recruitment of a lentic fish

Similar to coastal marine systems, Lake Erie exhibits open-water river plumes that differ physicochemically and biologically from surrounding waters. To explore their importance to yellow perch (Perca flavescens) recruitment in western Lake Erie, we tested two related hypotheses: (i) contributions of larvae to the juvenile stage (when recruitment is set) would be greater from nutrient-rich Maumee River plume (MRP) waters than from less-productive non-MRP waters; and (ii) warmer temperatures and higher zooplankton (prey) production in the MRP (versus non-MRP waters) would underlie this expected recruitment difference through “bottom-up” effects on larval growth. Peak larval yellow perch density was 10-fold and 5-fold less in the MRP than in non-MRP waters during 2006 and 2007, respectively. However, otolith microchemical analyses demonstrated that disproportionately more juvenile recruits emanated from the MRP than from non-MRP waters during both years. Although temperature and zooplankton production were ...