Paul Sylvester

In the lower volcanic cycle (2750 Ma old) of the Michipicoten greenstone belt, Ontario, a basal mafic unit (MV1) consisting mainly of basalt-basaltic andesite (49.4-56.4 wt.% SiO/sub 2/, 8.77-12.36 wt.% FeO/sub t/) with enriched ((La/Sm)/sub n/=1.9-2.6, Th=2.0-4.1 ppm, Sr=310-570 ppm) and depleted ((La/Sm)/sub n/=0.55-1.07, Th=0.16-0.71 ppm, Sr<250 ppm) trace element characteristics is locally overlain by a felsic unit (FV1) dominated volumetrically by rhyolite (71.9-79.6 wt.% SiO/sub 2/) and subordinate dacite (62.2-68.8 wt.% SiO/sub 2/). The mafic rocks are pillowed, massive flows and hyaloclastites suggesting subaqueous emplacement, whereas the felsic rocks are dominantly subaerial to shallow subaqueous pyroclastic deposits. The basalts of MV1 are similar chemically to modern tholeiites formed in primitive island arc/marginal basin complexes. In contrast, the rhyolites and dacites of FV1 exhibit the calc-alkaline chemical characteristics and rock associations typical of some continental inner arc volcanics. The juxtaposition of primitive island arc/marginal basin and continental inner arc tectonic settings occurs at the present time in the Tonga-Kermadec-New Zealand island arc. According to this model, MV1 is analogous to the basalt/basaltic andesite-dominated volcanism of the Tonga-kermadec island arc/Lau back-arc basin, whereas FV1 is the equivalent of the voluminous rhyolitic ignimbrites of the Taupo inner arc basin. The model suggestsmore » that the lower volcanic cycle of the Michipicoten belt formed on a basement consisting of small blocks of continental crust surrounded by oceanic crust.« less

Rhyolitic rocks often are the dominant felsic end member of the biomodal volcanic suites that characterize many late Archean greenstone belts of the Canadian Shield. The rhyolites primarily are pyroclastic flows (ash flow tuffs) emplaced following plinian eruptions, although deposits formed by laval flows and phreatomagmatic eruptions also are presented. Based both on measured tectono-stratigraphic sections and provenance studies of greenstone belt sedimentary sequences, the rhyolites are believed to have been equal in abundance to associated basaltic rocks. In many recent discussions of the tectonic setting of late Archean Canadian greenstone belts, rhyolites have been interpreted as products of intracontinental rifting . A study of the tectono-stratigraphic relationships, rock associations and chemical characteristics of the particularly ell-exposed late Archean rhyolites of the Michipicoten greenstone belt, suggests that convergent plate margin models are more appropriate.

The Pb isotopic composition of detrital K-feldspar is a powerful means of constraining sandstone provenance. It has been shown that K-feldspar retains the Pb signature of its source despite erosion, transport and diagenesis. The continental crust exhibits broad (100s km) variations in Pb isotopes and thus potential sourcelands can be characterised on a scale appropriate to that of major drainage systems. Electron microprobe analysis and imaging (BSE and CL) of detrital grains means that heterogeneities (e.g. inclusions, alteration) can be avoided during in-situ LA-MC-ICPMS analysis. Furthermore, as K-feldspar is a common and likely first cycle component of sandstones, the technique provides a means of tracking grains directly back to their source. In this way, the method can constrain palaeodrainage pathways and lengthscales, with consequent application to palaeogeographic reconstuctions.

Detrital zircons from all major clastic units in the Jack Hills and Mount Narryer metasedimentary belts, Western Australia, were analyzed for morphology, internal zoning, inclusion mineralogy, age, and trace element concentrations (latter two obtained by laser-ablation microprobe ICPMS). The results show that zircons were derived from a wide diversity of rocks, including previously described, >4000 Ma grains that are older

— Watson, which was found in 1972 in South Australia, contains the largest single silicate rock mass seen in any known iron meteorite. A comprehensive study has been completed on this unusual meteorite: petrography, metallography, analyses of the silicate inclusion (whole rock chemical analysis, INAA, RNAA, noble gases, and oxygen isotope analysis) and mineral compositions (by electron microprobe and ion microprobe). The whole rock has a composition of an H‐chondrite minus the normal H‐group metal and troilite content. The oxygen isotope composition is that of the silicates in the HE iron meteorites and lies along an oxygen isotope fractionation line with the H‐group chondrites. Trace elements in the metal confirm Watson is a new HE iron. Whole rock Watson silicate shows an enrichment in K and P (each ∼2X H‐chondrites). The silicate inclusion has a highly equilibrated igneous (peridotite‐like) texture with olivine largely poikilitic within low‐Ca pyroxene: olivine (Fa20), opx (Fs17Wo3), capx (Fs9Wo41) (with very fine exsolution lamellae), antiperthite feldspar (An1–Or5) with <1 μm exsolution lamellae (An1–3Or>40), shocked feldspar with altered stoichiometry, minor whitlockite (also a poorly characterized interstitial phosphate‐rich phase) and chromite, and only traces of metal and troilite. The individual silicate minerals have normal chondritic REE patterns, but whitlockite has a remarkable REE pattern. It is very enriched in light REE (La is 720X C1, and Lu is 90X C1, as opposed to usual chonditic values of ∼300X and 100–150X, respectively) with a negative Eu anomaly. The enrichment of whole rock K is expressed both in an unusually high mean modal Or content of the feldspar, Or13, and in the presence of antiperthite.Whole rock trace element data for the silicate mass support the petrography. Watson silicate was an H‐chondrite engulfed by metal and melted at > 1550 °C. A flat refractory lithophile and flat REE pattern (at ∼1x average H‐chondrites) indicate that melting took place in a relatively closed system. Immiscible metal and sulfide were occluded into the surrounding metal host. Below 1100 °C, the average cooling rate is estimated to have been ∼1000 °C/Ma; Widmanstätten structure formed, any igneous zoning in the silicates was equilibrated, and feldspar and pyroxene exsolution took place. Cooling to below 300 °C was completed by 3.5 Ga B. P. At 8 Ma, a shock event took place causing some severe metal deformation and forming local melt pockets of schreibersite/metal. This event likely caused the release of Watson into interplanetary space. The time of this event, 8Ma, corresponds to the peak frequency of exposure ages of the H‐chondrites. This further confirms the link between HE irons and the H‐chondrites, a relationship already indicated by their common oxygen isotope source.Watson metal structures are very similar to those in Kodaikanal. Watson, Kodaikanal and Netschaëvo form the young group of HE meteorites (ages 3.7 ± 0.2 Ga). They appear to represent steps in a chain of events that must have taken place repeatedly on the HE parent body or bodies from which they came: chondrite engulfed in metal (Netschaëvo); chondrite melted within metal (Watson); and finally melted silicate undergoing strong fractionation with the fractionated material emplaced as globules within metal (Kodaikanal). Watson fills an important gap in understanding the sequence of events that took place in the evolution of the IIE‐H parent body(ies). This association of H‐chondrite with HE metal suggests a surface, or near surface process‐a suggestion made by several other researchers.

... 344 Figure 1. Location of kimberlite and ultramafic lampro-phyre dykes in Labrador. Page 3. DHC WILTON, RC TAYLOR, PJ SYLVESTER AND GT PENNEY ... McConnell and Ryan (1996), however, suggest that the White Point breccias are not kimberlite pipes. ...

Three spinel-rich, perovskite-bearing, pyroxene-rimmed, hibonite-free inclusions from the Murchison C2 chondrite have volatility controlled, modified group II REE patterns. Two have high Eu/Yb ratios, two have small positive Ce anomalies and one has high refractory siderophiles for a group II inclusion. Two additional spinel-rich inclusions have subchondritic Ce/La ratios and negative Eu and Yb anomalies, the Eu anomalies being larger than the Yb ones. One of these inclusions is enriched in La relative to all HREE and the other is enriched in HREE relative to all LREE except La, possibly suggesting the presence of an ultrarefractory component in the latter. One hibonite-rich inclusion has a group III REE pattern with a negative Ce anomaly. A calcium dialuminate-bearing inclusion known to have crystallized from a melt at 2100-1800K has a modified group II REE pattern, rather than a pattern which would be predicted from the evaporation expected from such a droplet, e.g., a group III o...

Publisher Summary Potassium-rich granite, contrary to some opinions expressed in the past is a widespread and voluminous constituent of Archean cratons. Some of the granite occurs as highly metamorphosed banded gneiss but the majority forms massive to moderately foliated, medium- to coarse-grained plutons that largely retain an igneous mineralogy. Most of the plutons have areal exposures of 5-500 km2 but a few exceed 1000 km2. Condie (1993) estimated that granite plutons make up ∼20% of the rock exposed in Archean shields, placing them far ahead of tholeiite (∼10%) and second only to the tonalite-trondhjemite-granodiorite (TTG) suite (∼50%) in abundance. Until recently, there have been only a handful of detailed studies of Archean granite plutons and, with few exceptions, almost no attempt to place what is known about these rocks in a general context.

Lead isotopes were used to determine sources of high quantities of lead in soilsin urban St. John’s, Newfoundland. Highest lead levels are found near roads(mean=674 ppm) and along the drip line of houses built prior to 1945(mean=2107 ppm) and are an order of magnitude higher than background levelsfrom C-horizon tills (40 ppm). In many cases values exceed national guidelines(CCME, 140 ppm). Sources likely include atmospheric precipitation, coal ashwastes and deposition of lead-based paints along drip lines of buildings. Leadwas likely contributed to the atmosphere from burning of coal for home heatingand from leaded gasoline.Previous measurements of lead isotopes in lake sediments in and aroundthe city suggested that the sources of lead used in the manufacture of dispersedcontaminants changed in about 1960 from ores with low 206Pb/207Pb ratios(~1.064 in the Sullivan mine in Trail, British Columbia or ~1.037 in Broken Hill,Australia) to ores with much higher 206Pb/207Pb ratios (~1.16 in Bathurst, NewBrunswick or 1.28-1.33 from southeastern Missouri, U.S.A.). This studydetermined lead isotopes ratios in 27 soils, 7 C-horizon tills, 2 exterior paints anda piece of archived coal to constrain the sources of lead and their relativecontributions.A linear trend from bedrock-derived lead in tills with high 206Pb/207Pb(~1.18-1.20) and low 208Pb/206Pb (~2.06-2.08) ratios to leads from clapboard driplines and paint from >100 year-old houses with low 206Pb/207Pb (~1.12-1.13) andhigh 208Pb/206Pb (~2.13-2.14) ratios is apparent. Coal and paint from a 50 yearoldhouse fall mid-way along the trend (as do ratios from ores from Bathurst).Soils with moderate lead levels from vacant lots and parks plot toward higher206Pb/207Pb values, whereas lead-rich soils from residential settings plot towardlower 206Pb/207Pb. Contamination of open spaces is dominated by lead fromCape Breton coal and/or gasoline residues and 50 year-old paint derived in part from Sullivan leads.Lead isotope compositions of some soils collected along roads and open spacesin the city trend away from the main data array toward a lead source with higher206Pb/207Pb and lower 208Pb/206Pb than the natural background source. Theseareas may be contaminated by residues of gasoline lead from SE Missouri ores.Anthropogenic lead in St. John’s soils thus appears to be derived from up to fourexotic sources.

The Birchy Complex of the Baie Verte Peninsula, northwestern Newfoundland, comprises an assemblage of mafic schist, ultramafic rocks, and metasedimentary rocks that are structurally sandwiched between overlying ca. 490 Ma ophiolite massifs of the Baie Verte oceanic tract and underlying metasedimentary rocks of the Fleur de Lys Supergroup of the Appalachian Humber margin. Birchy Complex gabbro yielded a Late Ediacaran U–Pb zircon ID–TIMS age of 558.3 ± 0.7 Ma, whereas gabbro and an intermediate tuffaceous schist yielded LA–ICPMS concordia zircon ages of 564 ± 7.5 Ma and 556 ± 4 Ma, respectively. These ages overlap the last phase of rift-related magmatism observed along the Humber margin of the northern Appalachians (565–550 Ma). The associated ultramafic rocks were exhumed by the Late Ediacaran and shed detritus into the interleaved sedimentary rocks. Psammite in the overlying Flat Point Formation yielded a detrital zircon population typical of the Laurentian Humber margin in the nor...

The mineralogy, petrology, and geochemistry of an igneous-textured clast in the Peace River L6 chondrite meteorite was examined to determine the roles of nebular processes, accretion, and parent-body metamorphism in its origin. The centimetre-scale clast is grey and fine grained and is in sharp contact with the host chondrite. Two sub-millimetre veins cut across both the clast and host, indicating that the clast formed prior to the impact (shock) event(s) that produced the numerous veins present in the Peace River meteorite. The clast and host are indistinguishable in terms of mineral compositions. In contrast, there are differences in modal mineralogy, texture, as well as trace element and oxygen isotope composition between the clast and host. These differences strongly suggest that the clast was formed by impact melting of LL-group chondritic material involving loss of Fe–FeS and phosphate components, followed by relatively rapid cooling and incorporation into the Peace River host...

Orogens or zones of the plate convergence show a great variability of style in respect of the plate‘s character and their relative motion. The variability of style is reflected in the variability of volcanic phenomena, which is directly related to processes in the mantle and deep crust. The most common model of orogenic volcanism relates volcanic activity to the contemporaneous subduction of “oceanic crust”. Primary magmas are in this case generated by partial melting of metasomatized mantle above the subduction zone. Volcanic rocks are generally of the calc-alkali composition. However, a significant variability from low-K to high-K suites has been observed across volcanic arcs and in the succession from oceanic arcs to continental margins. Bimodal andesite/rhyolite suites are characteristic of evolved arcs and continental margins. Each subduction is eventually concluded by the slab detachment during arc/continent or continent/continent collision. The slab detachment accelerates com...

Jan was a vibrant and creative analytical geochemist and geoscientist with more than 80 publications to his name. He hailed from Prague in the Czech Republic, where he met and married his wife, Alena, and his daughter Anna and son Josef were born. He spent his early research career at Charles University in Prague, graduating with an MSc in Geochemistry, becoming Lecturer and Assistant Professor (after attaining his PhD from the University of Glasgow under the supervision of Prof. Donald Bowes), with research fellowships at The Open University, Czech Geological Survey and Memorial University of Newfoundland during this time. Jan then began an association with University of Bergen where he remained, eventually becoming full Professor in 2007. Jan continued to keep links with Charles University, supervising a stream of postgraduate students who now make their own impact on the geoscience community. It is perhaps this travelling for career, conferences and fieldwork, which typified Jan’s enthusiasm for his science. He escaped the damp Bergen winters regularly to attend the Winter Conference on Plasma Spectrochemistry in the southern USA, where he co-taught a short course on Laser Ablation ICP-MS fundamentals. He participated enthusiastically in field geologic research excursions to Namibia, Antarctica and the Eastern Nepal Himalaya, and aboard the G.O. Sars research vessel to the Arctic island, Jan Mayen. He had in fact returned to Bergen only a few weeks prior to his passing, from a year-long sabbatical at the Geological Survey of Canada in Ottawa, which, gladly, he and his family (including his beloved Emma, a gorgeous Nova Scotia Duck Tolling Retriever) had enjoyed immensely.

Mineral liberation analysis (MLA), combined FIB-SEM-TEM techniques, synchrotron and light stable isotope microanalysis, hot and cold cathodoluminescence, X-ray-computed tomography, refl ectance and imaging spectroscopy, high-resolution heavy-mineral analysis, computer-controlled scanning electron microscopy (CCSEM), U–Pb and fi ssion-track geochronology of zircon and apatite, Hf and Pb isotope geochemistry of zircon and feldspar—this is the impressive menu of the novel, exciting techniques currently applied in the study of sedimentary deposits and illustrated in full detail in the relatively slim volume Quantitative Mineralogy and Microanalysis of Sediments and Sedimentary Rocks.

Summary The Orphan and Flemish Pass basins are frontier offshore deep water basins, located approximately 400 km northwest of the Avalon Peninsula, Newfoundland. Mesozoic sandstone intervals from three wells (Mizzen L-11, Baccalieu I-78 and Blue H-28) were studied for provenance analysis using heavy minerals. Three techniques were used for provenance analysis and correlations of units: detrital zircon geochronology, heavy mineral ratios and detrital tourmaline geochemistry. In the Northern Flemish Pass Basin, a change in sediment source occurred between the Late Jurassic and Early Cretaceous from dominantly Paleozoic with minor Mesozoic and Early Neoproterozoic sources to dominantly Early Neoproterozoic sources. This is interpreted to represent an switch from sediment derived from the south (Avalon Uplift area) to locally derived sediment (local Avalon zone basement). In the West Orphan basin, sources from a Cretaceous sandstone interval are dominantly Paleozoic with subordinate Ear...

Isotopics composition of Li in volcanic arc lavas reflects the composition of their sources and can be potentially used to determine the relative contributions of subducted oceanic crust, sediments and material derived from the overlying mantle wedge (Moriguti and Nakamura 1998, Tomascak et al. 2000, Chan et al. 2002). Li was extracted from samples of mid-Miocene (15–10 Ma) early-arc tholeiites collected from the southern shore of the Viti Levu Island (southern Fiji) and from the late-arc rift-related calc-alkaline basalts and shoshonites of late Miocene – Pliocene age (5.5 to 3 Ma) from the northern coast of Viti Levu. We have used a two-stage ion exchange chromatography to separate Li from the matrix prior to the analysis on ICPMS to avoid the matrix induced bias of isotopic data. We have utilized low volume (2 mL) polyethylene and PFA columns and conventional ion exchange techniques (Dowex anion 1-X8 and cation 50W-X8 ion exchangers) to achieve quantitative separation of Li. Isot...

Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) has been used for more than 30 years to determine the elemental composition of natural and synthesized objects. A focused laser beam ablates a small volume of target material, and the aerosol produced is transferred in a gas stream to an ICP–MS for elemental and/or isotopic analysis. Through the increasing use of deep ultraviolet lasers and ultra-sensitive mass spectrometers, the technique has evolved towards higher sampling resolution and to generating 2-D (and 3-D) images of compositional variations. The future is likely to see femtosecond lasers and simultaneous mass spectrometers in common use, making new research areas possible.

Niobium/uranium ratios in greenstone-belt basalts and gabbros indicate that parts of the Late Archean mantle beneath Western Australia underwent a level of melt extraction, resulting in formation of the continental crust, comparable to that seen in the present mantle. The implication is either that (i) the amount of continental crust that formed before 2.7 × 10 9 years ago was much greater than generally thought or (ii) crustal growth occurred by severe depletion of small volumes of the mantle rather than by moderate depletion of a large volume of mantle.

Page 1. In situ determination of sulfur isotopes in sulfur-rich materials by laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) Paul RD Mason,*a Jan Kosˇler,b Jan CM de Hoog,ac Paul J. Sylvesterd and Simon Meffan-Maine ...

Scheelite (CaWO 4 ) is a widespread accessory mineral associated with hydrothermal veins in the Archean gold deposits of the Kalgoorlie-Norseman region of Western Australia. Rare earth element (REE) and other trace element abundances in scheelite have been determined in situ by excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS) in order to constrain the composition and sources of the mineralizing fluids. The scheelites can be grouped according to the two distinct types of chondrite-normalized REE (REE N ) patterns which they exhibit: hump-shaped (type I) and flat (type II). Type I scheelites have higher total and Na concentrations than type II samples and can be further subdivided into type Ia which has maximum REE N concentrations between Sm and Gd, and type Ib which has maximum REE N concentrations displaced toward Dy. Type I scheelites are dominant at Coolgardie, Kalgoorlie, and Kambalda, whereas type II samples are most abundant at Norseman. A few scheelite grains exhibit both type I and type II characteristics.The two types of REE N patterns with different Na abundances suggest that the trivalent REE substituted into the Ca site of scheelite by two different mechanisms: 2Ca (super 2+) = REE (super 3+) + Na (super +) for the type I scheelites and 3Ca (super 2+) = 2REE (super 3+) + Ca (where Ca is a Ca site vacancy) for the type II samples. The parabolic shape of REE N patterns in the type I scheelites can be used to calculate the ionic radius of the REE (super 3+) that preferentially substitutes into the scheelite structure. When type I REE patterns are normalized to account for variations in light REE abundance, the average value obtained is 1.060 Aa for type Ia and 1.055 Aa for type Ib scheelites. These values are smaller than the value of 1.12 Aa for the Ca site but are in excellent agreement with the value of 1.06 Aa predicted by the coupled Na (super +) -REE (super 3+) substitution mechanism, assuming size as well as charge compensation. This result implies that Na (super +) and REE (super 3+) substitute into adjacent sites in the crystal structure of type I scheelites. In contrast, the incorporation of REE into type II scheelites appears to be independent of size. It is suggested that in this type of scheelite, involvement of a Ca site vacancy relaxes the size constraint on the substitution of the REE (super 3+) . The influence of REE speciation in the hydrothermal fluid on the systematic difference between scheelite-fluid partition coefficients for type I and II scheelites is of secondary importance compared with crystal chemistry effects.The distinctive REE N patterns and high Na contents of type I scheelites imply that they crystallized from hydrothermal fluids with higher Na activities than those that formed type II samples. Type I scheelites exhibit no changes in the size of the Eu anomaly with REE concentration, implying a predominance of Eu (super 3+) and crystallization under relatively oxidized conditions. Type II scheelites have variable Eu anomalies and trivalent REE concentrations and thus appear to contain mostly Eu (super 2+) and to have formed under reduced conditions. Type Ia and II scheelites have (Ce/Lu) N > 1 and are interpreted to have crystallized from light REE-enriched fluids, whereas type Ib scheelites with (Ce/Ln) N < 1 formed from light REE-depleted fluids.The fluid characteristics inferred from the REE and trace element systematics in the scheelites can be attributed to the rock types and estimated physical conditions in the Kalgoorlie-Norseman region at the time of hydrothermal activity. High Na activities are consistent with buffering of fluids by greenschist facies mafic rocks, whereas low fluid Na activities are a product of fluid-rock reactions at higher metamorphic grades. Oxidized fluids are consistent with near-surface derivation, whereas reduced fluids are indicative of generation at elevated temperatures and pressures. The range and distribution of fluid (Ce/Ln) N ratios are similar to those of the major rock types in the region.

Scheelite (CaWO 4 ) is a widespread accessory mineral associated with hydrothermal veins in the Archean gold deposits of the Kalgoorlie-Norseman region of Western Australia. Rare earth element (REE) and other trace element abundances in scheelite have been determined in situ by excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS) in order to constrain the composition and sources of the mineralizing fluids. The scheelites can be grouped according to the two distinct types of chondrite-normalized REE (REE N ) patterns which they exhibit: hump-shaped (type I) and flat (type II). Type I scheelites have higher total and Na concentrations than type II samples and can be further subdivided into type Ia which has maximum REE N concentrations between Sm and Gd, and type Ib which has maximum REE N concentrations displaced toward Dy. Type I scheelites are dominant at Coolgardie, Kalgoorlie, and Kambalda, whereas type II samples are most abundant at Norseman. A few scheelite grains exhibit both type I and type II characteristics.The two types of REE N patterns with different Na abundances suggest that the trivalent REE substituted into the Ca site of scheelite by two different mechanisms: 2Ca (super 2+) = REE (super 3+) + Na (super +) for the type I scheelites and 3Ca (super 2+) = 2REE (super 3+) + Ca (where Ca is a Ca site vacancy) for the type II samples. The parabolic shape of REE N patterns in the type I scheelites can be used to calculate the ionic radius of the REE (super 3+) that preferentially substitutes into the scheelite structure. When type I REE patterns are normalized to account for variations in light REE abundance, the average value obtained is 1.060 Aa for type Ia and 1.055 Aa for type Ib scheelites. These values are smaller than the value of 1.12 Aa for the Ca site but are in excellent agreement with the value of 1.06 Aa predicted by the coupled Na (super +) -REE (super 3+) substitution mechanism, assuming size as well as charge compensation. This result implies that Na (super +) and REE (super 3+) substitute into adjacent sites in the crystal structure of type I scheelites. In contrast, the incorporation of REE into type II scheelites appears to be independent of size. It is suggested that in this type of scheelite, involvement of a Ca site vacancy relaxes the size constraint on the substitution of the REE (super 3+) . The influence of REE speciation in the hydrothermal fluid on the systematic difference between scheelite-fluid partition coefficients for type I and II scheelites is of secondary importance compared with crystal chemistry effects.The distinctive REE N patterns and high Na contents of type I scheelites imply that they crystallized from hydrothermal fluids with higher Na activities than those that formed type II samples. Type I scheelites exhibit no changes in the size of the Eu anomaly with REE concentration, implying a predominance of Eu (super 3+) and crystallization under relatively oxidized conditions. Type II scheelites have variable Eu anomalies and trivalent REE concentrations and thus appear to contain mostly Eu (super 2+) and to have formed under reduced conditions. Type Ia and II scheelites have (Ce/Lu) N > 1 and are interpreted to have crystallized from light REE-enriched fluids, whereas type Ib scheelites with (Ce/Ln) N < 1 formed from light REE-depleted fluids.The fluid characteristics inferred from the REE and trace element systematics in the scheelites can be attributed to the rock types and estimated physical conditions in the Kalgoorlie-Norseman region at the time of hydrothermal activity. High Na activities are consistent with buffering of fluids by greenschist facies mafic rocks, whereas low fluid Na activities are a product of fluid-rock reactions at higher metamorphic grades. Oxidized fluids are consistent with near-surface derivation, whereas reduced fluids are indicative of generation at elevated temperatures and pressures. The range and distribution of fluid (Ce/Ln) N ratios are similar to those of the major rock types in the region.

... Trace element analysis of scheelite by excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS) using a synthetic silicate glass standard. ... REE patterns determined by ELA-ICP-MS for the scheelites vary smoothly as a function of atomic number. ...