Laser Ablation Microprobe-inductively Coupled Plasma-mass Spectrometry Research Articles

Evolution of the Archaean Karelian Province in the Fennoscandian Shield in the light of U–Pb zircon ages and Sm–Nd and Lu–Hf isotope systematics

Abstract: In situ Lu–Hf (laser ablation microprobe–inductively coupled plasma mass spectrometry (LAM-ICPMS)) and U–Pb (LAM-ICPMS, secondary ionization mass spectrometry (SIMS)) analyses of zircon, and whole-rock Sm–Nd isotope analyses were performed on rocks formed during magmatic events in three Archaean complexes in the Karelian Province of Fennoscandia (Pudasjarvi, Koillismaa and Iisalmi). These complexes have U–Pb ages ranging from 3.5 to 2.6 Ga. In Pudasjarvi, sparse xenocrystic cores give ages of 3.6–3.7 Ga and initial 176 Hf/ 177 Hf suggesting influence of a crustal component T ≥ 4.0 Ga (assuming a CHUR-like mantle source). Ages and Nd and Hf isotope patterns indicate magmatic events at 3.6–3.7 Ga (Siurua, Pudasjarvi with ≥4.0 Ga precursor), 3.2 Ga (Iisalmi, Koillismaa), 2.8 Ga (Pudasjarvi) and 2.7 Ga (Pudasjarvi, Iisalmi). In the Meso- and Palaeoarchaean events, there is no evidence of sources equivalent to present-day depleted mantle; such sources were, however, involved in the 2.8–2.7 Ga events. e Hf and e Nd are strongly correlated. Contrasts between the Archaean complexes indicate that they evolved separately until c . 2.7 Ga. The age and e Hf pattern of ≤2.8 Ga rocks in the Karelian Province is compatible with a scenario in which the Karelia, Superior, Yilgarn and Slave cratons were part of a late Archaean supercontinent, but does not constitute proof of the existence of such a supercontinent. Supplementary material: U–Pb and Lu–Hf data are available at http://www.geolsoc.org.uk/SUP18430.

Laser ablation microprobe inductively coupled plasma mass spectrometry study on diffusion of uranium into cement materials

Abstract The diffusion of uranium (U(VI)) in solid cement monoliths of ordinary portland cement (OPC) and low-heat portland cement containing 30[wt.]% fly ash (FAC) was measured by an in-diffusion technique. Detailed sharp depth profiles of uranium in the solid cement matrices were successively and quantitatively measured using laser ablation microprobe inductively coupled plasma mass spectrometry (LAMP-ICP-MS), and the apparent (D a) and effective (D e) diffusion coefficient of uranium in cement matrix were calculated as: D a=∼4×10−16 m2 s−1 and D e=∼3×10−11 m2 s−1 for OPC, and D a=∼2×10−17 m2 s−1 and D e=∼6×10−13 m2 s−1 for FAC.

LAM-ICP-MS zircon dating of the Falcon Lake Intrusive Complex and Caddy Lake granite, southeastern Manitoba, Canada

The Falcon Lake Intrusive Complex is a layered, compositionally zoned intrusion that intrudes the western end of the Wabigooti-Kenora Greenstone Belt of the Superior province, Canada. Cross-cutting field relations indicate that it is post-tectonic; internal contacts are complex and preserve evidence of multiple phases of magma emplacement and magmatic erosion. Xenoliths of country rock are common, as are cognate xenoliths, particularly in the central part of the intrusion. Zircon separates were collected from three of the six principal magmatic phases and dated using LAM-ICP-MS (laser ablation microprobe-inductively coupled plasma-mass spectrometry). Zircon crystals typically preserve internal textures including sector zoned cores mantled by oscillatory zoned overgrowths. These give an age of emplacement for the Falcon Lake Intrusive Complex of between 2733 ± 15 Ma and 2723 ±9 Ma. Zircon crystals from the Caddy Lake granite were also sector zoned and give an age of emplacement of 2687 ± 7 Ma.

QUANTITATIVE MASS BALANCE OF PLATINUM GROUP ELEMENTS IN THE KELLY LAKE Ni-Cu-PGE DEPOSIT, COPPER CLIFF OFFSET, SUDBURY

A mineralogical mass balance has been calculated for the fraction of platinum group elements (PGE) incorporated as solid solution in sulfides and sulfarsenides and the fraction that occurs as major constituents in platinum group minerals (PGM) in the Kelly Lake Ni-Cu-PGE sulfide deposit in the Copper Cliff offset, Sudbury. Low levels of PGE in sulfides were determined quantitatively for the first time in Sudbury ores by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS), providing significantly more accurate data on the inventory and mineralogical distribution of the PGE than in previous studies. The majority of the Pt (98%), Rh (97%), and Ir (86–91%), and lesser but still large fractions of Pd (77–87%) and Ru (67–71%), occur as discrete PGM with the remainder occurring (in decreasing abundance) in solid solution in gersdorffite (1,700 ppm ∑PGE), pentlandite (1.35 ppm), chalcopyrite (0.5 ppm), and pyrrhotite (0.3 ppm). Although the PGE are present in low concentrations in sulfides, the abundances of these phases can be high enough to constitute a significant fraction of the total PGE. In particular, significant proportions of the Pd (14–23%) and Ru (~30%) in the Kelly Lake samples are hosted by sulfides and sulfarsenides. This has important implications for the genesis of the PGE, for the redistribution of the PGE during cooling and hydrothermal alteration, and for metal recovery during ore beneficiation.

Trace element partitioning in lamproitic magmas—the Gaussberg olivine leucitite

Partition coefficients for compatible and incompatible trace elements for use in modelling the origin and evolution of lamproitic and other potassic rocks are reported. These are based on values obtained by in situ determination using laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) on mineral/glass pairs in examples of the Gaussberg olivine leucitite, a classic leucite lamproite. Leucite/melt partition coefficients for 32 elements show values above 1 only for Cs and Rb, whereas values for Ni, Ga and Co are 0.4–0.1. D Lc/Lq for most other elements are in the range 0.07–0.0005, and delineate a gently sloping pattern to lower values for elements generally considered to be “incompatible”. Olivine/melt partition coefficients show higher values for the compatible elements Ni, Co, Mn and Cr than in all basaltic systems investigated experimentally to date. D Ol/Lq for heavy rare earth elements (HREE) are slightly lower than in basalts, whereas most other elements give similar values. Clinopyroxene/melt partition coefficients appear to vary widely as a function of the Al 2O 3 content of the rock. Values obtained here for the Gaussberg rock consistently show appreciably higher D Cpx/Lq than in basaltic systems for the incompatible elements Cs, Rb, Ba, Th, U, Nb, Ta, La and Ce, which is attributed to a larger M2 site. Early salitic cores have patterns with lower D-values for these elements and higher values for HREE, similar to those known from alumina-rich potassic rocks. Thus, the values obtained here should be applied only with caution to nonlamproitic rocks. Other notable characteristics are high D U/ D Th and low D Zr and D Hf, the latter of which is attributed to structural characteristics of peralkaline melts.

Paleoproterozoic crustal genesis: calc-alkaline magmatism of the Torngat Orogen, Voisey’s Bay area, Labrador

Abstract A suite of metaplutonic rocks representing a mafic to intermediate calc-alkaline batholith has been identified in the Voisey’s Bay area of northern Labrador. The suite represents the southern extension of similar metaplutonic rocks occurring along some 500 km of the Paleoproterozoic Torngat Orogen. The rocks have been metamorphosed at upper amphibolite to granulite facies conditions that only mildly disturbed their igneous characteristics. Two magma series are present, one comprising gabbros, diorites and quartz diorites, and another composed of tonalites. The gabbro to quartz diorite series evolved by fractional crystallization of a mantle-derived mafic magma. Two samples of the metaplutonic suite yield U–Pb zircon thermal ionization mass spectrometry (TIMS) ages of 1893±1 and 1890±2 Ma. Based on U–Pb zircon laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) geochronology, one of these samples contains inherited cores, some 50–100 Ma older than the igneous population, but no Archean cores were found. Metatonalite rocks formed from a separate tonalitic magma during a slightly younger magmatic event dated at 1883±5 Ma. Both the gabbro to quartz diorite and tonalite series rocks are enriched in Rb, Ba, Sr, Zr and light rare earth elements relative to primitive mantle; and have negative Nb–Ta anomalies, which are thought to reflect subduction processes. They have fractionated REE patterns, with the extent of fractionation greatest for the tonalites (chondrite normalized La/Yb=30–50), suggesting that their parent magmas left more residual garnet in their source regions than did the gabbro to quartz diorite magmas. Sr–Nd–Pb isotope compositions of the metaplutonic suite indicate significant involvement of a lower crustal component in their genesis. When combined with previous data for the suite, and excluding data thought to be disturbed by metamorphism, 87 Sr / 86 Sr (1890 Ma ) =0.7036 –0.7048, e Nd (1890 Ma ) =+4.7 to −6.9, and μ∗ (time-integrated 238 U / 204 Pb of the mantle and crustal sources) = 7.66–7.98. A model for the metaplutonic suite is presented in which the gabbro to quartz diorite series formed by partial melting of the mantle wedge in a subduction zone and interacted with a lower crustal contaminant, possibly in the source region. The tonalites were derived by partial melting of a mixture of subducting oceanic crust and lower crustal detritus. An important role for lower crustal recycling is thus indicated. Crustal genesis by both mantle wedge and slab melting in the Paleoproterozoic may mark the transition from Archean to post-Archean subduction processes.

Neon Inductively Coupled Plasma for Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

The use of a neon inductively coupled plasma (Ne ICP) in place of an argon inductively coupled plasma (Ar ICP) for laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) is demonstrated. Gas blank mass spectra were obtained comparing the signals obtained with an Ar ICP with the Ne ICP. Sensitivity (signal/concentration) data were also obtained for a number of analytes using solid reference materials. The sensitivity data is complicated by significant changes in optimum Ne ICP parameters (especially nebulizer gas flow) for analytes of varying mass. The sensitivity of the Ne ICP is in general also lower than that obtained for the Ar ICP. The potential for the Ne ICP to reduce the formation of argides, both in the background and from sample induced interferences, is demonstrated. Clearly shown is the reduction of the interferences of 63Cu40Ar and 65Cu40Ar on 103Rh and 105Pd in a Cu2S sample, as well as the reduction of the interferences of 58Ni40Ar and 60Ni40Ar on 98Ru and 100Ru in a NiS sample.

Depositional and tectonic setting of the Paleoproterozoic Lower Aillik Group, Makkovik Province, Canada: evolution of a passive margin-foredeep sequence based on petrochemistry and U–Pb (TIMS and LAM-ICP-MS) geochronology

The Paleoproterozoic Lower Aillik Group is a deformed metasedimentary–metavolcanic succession located in the Makkovik Province of Labrador, eastern Canada. The group is situated near the boundary between reworked Archaean gneiss of the Nain (North Atlantic) craton and juvenile Paleoproterozoic crust that was both tectonically accreted and formed on or adjacent to this craton during the ca. 1.9–1.78 Ma Makkovikian orogeny. The Lower Aillik Group is structurally underlain by Archaean gneiss and structurally overlain by ca. 1860–1807 Ma bimodal, dominantly felsic volcanic and volcaniclastic rocks of the Upper Aillik Group. We present geochemical data from metavolcanic rocks and U–Pb geochronological data from several units of the Lower Aillik Group in order to address the depositional and tectonic history of this group. U–Pb data were obtained using both thermal ionization mass spectrometry (TIMS) and laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS). Two quartzite units near the structural base of the Lower Aillik Group contain detrital zircons only of Archaean age, and are interpreted to have been deposited on the Nain craton during post-2235 Ma rifting and initiation of a passive continental margin. Overlying mafic metavolcanic rocks contain thin horizons of intermediate tuff, one of which is dated at 2178±4 Ma. This relatively old age, and an inferred stratigraphic relationship with underlying sedimentary units, suggest that the volcanic rocks represent transitional oceanic crust, consistent with their geochemical similarity to tholeiitic rifted margin sequences of Mesozoic age in eastern North America. A package of interlayered psammitic and semipelitic metasedimentary rocks that appears to stratigraphically overlie the mafic volcanic unit is dominated by Paleoproterozoic detrital zircons but also contains Archaean grains. This package was deposited after 2013 Ma, the age of the youngest concordant zircon. The U–Pb data imply a minimum 165 m.y. time gap between mafic volcanism and sedimentation, and are consistent with deposition of the psammite–semipelite unit in an evolving foredeep that heralded the approach of a Paleoproterozoic arc terrane. Accretion of this terrane to the Nain cratonic margin at ca. 1.9 Ga initiated the Makkovikian orogeny. Although the Lower Aillik Group is highly deformed and may contain internal tectonic boundaries or be incomplete, the U–Pb and geochemical data allow quantitative assessment of a prolonged rift-drift-basin closure cycle that characterized the Early Paleoproterozoic evolution of the southern Nain cratonic margin.

New ideas on the Proterozoic-Early Palaeozoic evolution of NW Iberia: insights from U–Pb detrital zircon ages

U–Pb ages were obtained on single detrital zircon grains separated from six samples of Neoproterozoic and Lower Palaeozoic sedimentary and volcanosedimentary rocks from NW Iberia using the laser ablation microprobe-inductively coupled plasma mass spectrometry (LAM-ICP-MS) method. Precambrian greywackes yielded abundant zircons with Neoproterozoic (800–640 Ma) and Mesoproterozoic (0.9–1.2 Ga) ages, and a smaller proportion of Palaeoproterozoic (1.8–2 Ga) and Archaean zircons. Palaeozoic samples (Lower Cambrian and Ordovician) yielded abundant zircons with younger Neoproterozoic (ca. 550 and 620 Ma) and Mesoproterozoic (0.9–1.2 Ga) ages. Palaeoproterozoic (1.8–2 Ga) and Archaean zircons were also found. This data set, used in conjuction with previous paleogeographic and isotopic studies sheds new light on the Precambrian-early Palaeozoic evolution of NW Iberia and is consistent with the following sequence of events: (1) Early Cadomian-Avalonian subduction and arc construction (ca. 800–640 Ma). This magmatic episode created the main arc edifice (Avalonia); (2) full development of a back arc basin upon which the Neoproterozoic sediments were deposited (ca. 640–600 Ma). The combined U–Pb ages of detrital zircons and Nd isotopic features of these sedimenary rocks suggest that they were mostly shed from the main magmatic arc. On the basis of the presence of Grenvillian age detrital zircons with short waterborne transport before incorporation in the sediment, we propose that the basin was possibly located in a peri-Amazonian realm close to West Avalonian terranes. These basins were developed upon a cratonic basement that possibly involved both Grenvillian (ca. 0.9–1.2 Ga) and Transamazonian (ca. 1.9–2.1) igneous rocks. The reported zircon ages suggest a long-lived subduction, starting at ca. 800 Ma and terminated by ca. 580–570 Ma with no geological record of a final collision event; (3) the continuation of extension gave rise to the undocking of Avalonia from the back-arc. Detrital zircon ages in Lowermost Cambrian strata suggest that the main arc edifice had drifted away by ca. 550–540 Ma and was no longer shedding detritus into the back-arc basin. (4) During the Lower Ordovician, further extension of an already thinned crust gave rise to the Lower Ordovician ‘Ollo de Sapo’ magmatic event (ca. 480 Ma). Coeval volcanism in neighbouring areas displaying within-plate geochemical signatures is consistent with an extensional setting for the generation of the Lower Ordovician igneous and sedimentary rocks. Detrital zircon ages and Nd isotopic features of the Ordovician greywackes reflect both an increase in the contribution from older crustal components and the addition of newly accreted crust. A progressively thinning crust is a likely scenario that would explain the simultaneous exhumation of lower crustal (Grenvillian+Transamazonian/Icartian) material and the generation of coeval magmatism. This latter scenario is consistent with models proposed for other circum-North Atlantic Avalonian-Cadomian terranes where repeated episodes of melting occurred in response to subduction and subsequent rifting events.

The non-destructive determination of REE in fossilized bone using synchrotron radiation induced K-line X-ray microfluorescence analysis

The sensitivity and applicability of the synchrotron radiation induced X-ray microfluorescence (μ-SRXRF) spectrometer at the Hamburg synchrotron laboratory Hasylab for the determination of the distribution of trace concentrations of rare-earth elements (REE) in fossilized bone are discussed and critically compared to those of other trace analytical methods such as instrumental neutron activation analysis (INAA) and LAMP-ICPMS (laser ablation microprobe inductively-coupled plasma mass spectrometry). Measurements were carried out on two bone samples from contrasting terrestrial depositional environments at Olduvai Gorge (Tanzania). Results indicate that the microdistribution of the REE in these biological materials is not homogeneous and that the relative abundance of these elements can provide information on the palaeoenvironment during the fossilization process. The heterogeneous distribution of the REE can be determined in a quantitative and completely non-destructive manner provided the concentrations of individual REE are above 10 μg/g.

Cryptic metasomatism in the upper mantle beneath Southeastern Austria: A laser ablation microprobe-ICP-MS study

Upper mantle xenoliths from the classical location, Kapfenstein, Styria, as well as from Fehring, Styria, and Tobaj, Burgenland, have been analyzed by laser ablation microprobe inductively-coupled plasma mass spectrometry (LAM-ICP-MS). At all locations spinel lherzolite is the predominant xenolith type and thus our sample contains nine spinel lherzolites and only one harzburgite (from the richest location, Kapfenstein, sample Ka 167). All the rocks have protogranular to protogranular — porphyroclastic transitional textures. Mineral compositions are typical for fertile upper mantle rocks with 0.89 〈mg〉 0.92 for silicates and 0.10 〈cr〉 0.12 for spinel (0.18 for the harzburgite). The minerals are equilibrated with respect to major, minor and trace elements, except for clinopyroxenes in the sample from Tobaj (To 100) and one sample from Fehring (Feh 002) which have variable incompatible trace element contents.

Single zircon dating by LAM-ICPMS technique

A UV laser ablation microprobe-inductively coupled plasma mass spectrometry (LAMICPMS) is used to determine the Pb/Pb and Pb/U ages of several zircon grains whose ages have been measured by the conventional U-Pb thermal ionization mass spectrometry (TIMS) method. The mass fractionation factor of Pb isotope ratio was typically between 0.010-0.012 and corrected by NIST610 glass standard. Several factors that influence the stability of Pb/U ratio have been investigated and optimized. The precision of207Pb/206Pb and206Pb/238U from each sampling crater is within 0.6%—2.4% and 1%—10% respectively, while the precision for the average of mean ratios from different craters is 0.7% and 6% correspondingly. The207Pb/206Pb and206Pb/238U age differences compared with TIMS results are ≪ 1% and < 3% respectively.

Clinopyroxene/Orthopyroxene Trace Element Partition Coefficients in Spinel Peridotite Xenoliths

The distribution of incompatible trace elements between clinoand ortho-pyroxenes from spinel peridotite xenoliths has been investigated. The xenoliths came from three localities within the Pannonian Basin, Eastern Central Europe, namely Szigliget, Szentbekalla and Bondoro-hegy (EmbeyIsztin et al., 1989). All upper mantle xenoliths selected for this study are anhydrous and include the following textural types; protogranular, porphyroclastic, equigranular and poikilitic. Both metasomatised and unmetasomatised xenoliths were analysed. However, there were no significant interor intragranular trace element variations in the clinoand orthopyroxenes, and the homogeneity of the major elements in the mineral phases also suggest equilibrium. The four major mineral phases (clinoand orthopyroxene, olivine and spinel) were analysed by laser ablation microprobe inductively coupled plasma mass spectrometry (LAM-ICP-MS) at Memorial University of Newfoundland; for analysis details see Jenner et al. (1993). REE, Sr, Nb, Zr, Hf and Ti are above detection limits for the clinoand orthopyroxenes; however, these elements are generally too low in the olivines and spinels for quantitative analysis. The U, Th and Ta content of orthopyroxene was also below detection limits. The averages and standard deviations of the calculated orthopyroxene/clinopyroxene partition coefficients are given in Fig 1. This figure which is based on the averages of 37 xenoliths strongly confirms the observation of Rampone et al. (1991), McDonough et al. (1992) and Sun and Kerrich (1995) that the orthopyroxene/clinopyroxene partition coefficients of the HFSE elements (which substitute in the M1 sites in the pyroxenes) are significantly higher than those of the neighbouring REE (substituting in the M2 sites). The figure also illustrates orthopyroxene/clinopyroxene partition coefficients from some spinel peridotite xenoliths from British Columbia (Sun and Kerrich, 1995). These later data were calculated using solution ICPMS data on separated clinoand ortho-pyroxenes. The U-shaped pattern for the REE partition coefficients (i.e. the increase of the partition coefficients towards the LREE) is probably the result of impurities in the orthopyroxene separate. Highly incompatible trace elements reside not only in the pyroxene lattice but in fluid inclusions and along the grain boundaries. The REE partition coefficients based on in situ analysis show regular variation with ionic radii, e.g. Fig. 2, where there is illustrated an almost linear trend of the logarithm of the partition coefficients in the D (opx/cpx) versus ionic radii. There is increased scatter of the D values as lower trace element abundances in orthopyroxene are approached. However, the higher scattering in the case of some LREE and Sr (all have relatively large ionic radii) is not simply a result of analytical uncertainty; the orthopyroxene/clinopyroxene partition coefficents of these elements tend to increase with increasing equilibrium temperatures (Fig. 3.). This variation is intrepreted to be the result of a temperature dependence of Ca partitioning between

Ultra‐Trace Element Analysis of NIST SRM 616 and 614 using Laser Ablation Microprobe‐Inductively Coupled Plasma‐Mass Spectrometry (LAM‐ICP‐MS): a Comparison with Secondary Ion Mass Spectrometry (SIMS)

The microanalytical capability of laser ablation microprobe‐inductively coupled plasma‐mass spectrometry (LAM‐ICP‐MS) to determine ultra trace elemental concentrations has been demonstrated by the analysis of two low concentration glass standard reference materials, NIST SRM 614 and 616. Results for fifty two elements at concentrations in the low ng g‐1 range are compared with those determined using secondary ion mass spectrometry (SIMS). Both techniques provide results at these concentrations that generally agree within 95% confidence limits, demonstrating the accuracy for ultra‐trace level of in situ determinations by the two techniques. At concentrations of less than 20 ng g‐1 in NIST SRM 616, an accuracy and precision of better than 10% has been obtained for most mono‐isotopic rare earth elements, when a spot size of 50 μm is used. Limits of detection for selected elements were as low as 0.5 ng g‐1.

In situ trace-element analysis of individual silicate melt inclusions by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS)

This paper reports the successful application of laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) to the in situ analysis of a diverse suite of twenty trace elements including Zr, Hf, Nb, Ta, Y, and REEs, in individual silicate melt inclusions in phenocrysts from Fantale volcano, Ethiopia. The UV laser, a frequency quadrupled Nd: YAG operating at 266 nm, significantly improves the ablation characteristics of minerals that do not absorb strongly at near-IR wavelengths (e.g., quartz and feldspar). Furthermore, it allows for a significant reduction in ablation pit size to ca. 10 μm, thereby permitting numerous applications that require high-resolution sampling. Multiple ablations in individual melt inclusions in the size range 10–50 μm demonstrate both the effectiveness of the technique and the generally homogeneous character of the inclusions. Comparison of the LAM-ICP-MS data for international reference material RGM-1 (a rhyolite), with recommended values, indicates an analytical precision of <10% for most of the trace elements determined in this study. The trace element abundances of the Fantale melt inclusions, determined by LAM-ICP-MS, are typical of those of pantellerites (i.e., peralkaline rhyolites), and are consistent with their origin as tiny volumes of melt trapped in quartz and alkali-feldspar phenocrysts during the final stage of fractional crystallization of the host peralkaline magma.

Determination of the three-dimensional distributions of precious metals in sulphide minerals by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAMP-ICP-MS )

Precious metals are o f great financial importance and the form of their occurrence will dictate the economics of their recovery from ore. It has been postulated that “invisible” gold in sulphides occurs in solid solution, as particulates, or associated with micro-inclusions of other minerals in the host. This study applied the high spatial resolution (< 20 μm) and high sensitivity (sub-μg g −1 detection limits) of the laser ablation microprobe-inductively coupled plasma-mass spectrometer to identify both the form and concentration of gold in sulphides. Data are presented demonstrating the three-dimensional distribution of gold in minerals from Hemlo, Ontario, Canada, and Penjom Prospect, Kuala Lipis, Malaysia. Gold at μg g −1 ` levels was determined and, through its correlation with other trace elements, identified as either particulates or associated with micro-inclusions.

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)

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.

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

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 technique's 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.