Paul Sylvester | Texas Tech University (original) (raw)

Papers by Paul Sylvester

Research paper thumbnail of Heterogenous and Fractionated Metal in Canyon Diablo (IA) Graphite-Metal Rock

LPI, Mar 1, 2000

Introduction: Iron meteorites are widely believed to be igneous rocks derived from cores or impac... more Introduction: Iron meteorites are widely believed to be igneous rocks derived from cores or impact melt pools of planetesimals. In any case, iron meteorites allegedly formed by crystallization from a metal melt [e.g., 1-4]. On the other hand, it is known for a long time that iron meteorites are very old and carry abundant signs of primitiveness, like daughter nuclei of short-lived radioactive parents [5-11]. Inclusions of minerals and rocks in iron meteorites are common and clearly indicate that metal and inclusions (silicates, sulfides, oxides, phosphides, carbides, etc.) must have been brought together in the solid state. A liquid metal-solid xenocryst/xenolith mixing would not have worked as surface tension of the liquid metal and any gravity field would have quickly separated these phases [e.g., 12]. In addition, the fractionation trends exhibited by the chemical groups require different solid metal/liquid metal distribution coefficients [e.g., 3]. In order to overcome these problems, complex fractional crystallization-mixing models have been proposed [e.g., 4,13,14]. Recently, very clear evidence was found for a sub-solidus formation of IAB iron meteorites [e.g., 15-17]. Previous findings of inhomogeneous distribution of Ir in some iron meteorites [18-20] already gave a strong signal in favor of a low temperature origin of at least some iron meteorites. Here we report on the investigation of metal present in a graphite-metal rock from the Canyon Diablo (IA) iron meteorite. The results extend those obtained previously on a similar graphite nodule [21] and show that metals with highly different trace element contents co-exist on a sub-mm scale.

Research paper thumbnail of U/Pb geochronology of fossil fish dentine from Romualdo Formation, Araripe Basin, northeast of Brazil

Journal of South American Earth Sciences, 2022

Research paper thumbnail of Abstract: Provenance and paleodrainage patterns of Late Jurassic to Early Cretaceous synrift sandstones in the Flemish Pass Basin, offshore Newfoundland

Syn-rift sandstone from two industry exploratory wells in the Flemish Pass Basin, offshore Newfou... more Syn-rift sandstone from two industry exploratory wells in the Flemish Pass Basin, offshore Newfoundland, was studied for provenance analysis. The sandstone units were deposited during the Late Jurassic to Early Cretaceous (Tithonian and Neocomian) North Atlantic rifting stage, during which rifting intensified between Iberia and the Grand Banks, culminating in seafloor spreading between these continental blocks. The major sources of first-cycle detritus, based on U-Pb geochronology of detrital zircon, qualitative analysis of detrital zircons and chemical discrimination of detrital tourmalines, include the Late Neoproterozoic (650–600 Ma) arc-phase igneous rocks of the Avalon Zone as well as the Ordovician to Early Devonian (400–460 Ma) Taconic and Acadian magmatic rocks and metasedimentary rocks present in the Central Mobile Belt. Also, a large component of the source material is interpreted to be recycled, as indicated by significant populations of rounded detrital zircons and enric...

Research paper thumbnail of Abstract: LA-ICPMS measurements of gold abundance in sulphide and rock-forming minerals from granitoids, southwestern New Brunswick, Canada: insights into the genesis of intrusion-related gold systems

The abundances of gold and selected trace elements in magmatic sulphide and rock-forming minerals... more The abundances of gold and selected trace elements in magmatic sulphide and rock-forming minerals from SilurianDevonian granitoids in southwestern New Brunswick, a part of Canadian Appalachians, were quantitatively analyzed by laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICPMS). Major elements in these minerals were analyzed by electron microprobe. Gold is mainly hosted in sulphide minerals (i.e., chalcopyrite, pyrrhotite, and pyrite) as sub-micron inclusions (nano-nuggets). Gold in major rock-forming minerals (i.e., plagioclase, K-feldspar, biotite, hornblende, muscovite) and oxides (i.e., magnetite, ilmenite) are undetectable (< 0.02 ppm). Gold distribution coeffi cients between sulphide minerals and granitoid melt are empirically established as:

Research paper thumbnail of Abstract: In situ Hf-isotope zircon data from two Paleoproterozoic bimodal volcanic segments of the Aillik Group, Makkovik Province, Labrador

The Makkovik Province of eastern Labrador is part of an accretionary orogenic belt that formed du... more The Makkovik Province of eastern Labrador is part of an accretionary orogenic belt that formed during the Paleoproterozoic Makkovikian orogeny. The Aillik domain of the Makkovik Province is largely composed of: a) the Aillik Group, a package of Paleoproterozoic, polydeformed, bimodal volcano-sedimentary rocks, and b) abundant variably deformed Paleoproterozoic intrusive suites that intrude the Aillik Group. Two areas are the focus of this study. Middle Head is dominated by lower amphibolite facies arkosic sandstone, felsic tuff, rhyolite and basalt. Pomiadluk Point is composed primarily of lower amphibolite to upper greenschist facies felsic tuff and polymictic conglomerate with lesser preserved rhyolite and basalt. Recent detailed 1:10 000 scale bedrock mapping in conjunction with in situ Hf-isotopic geochemistry of zircon illustrate that the Aillik Group was deposited on ca 2.5 Ga crust at Middle Head, and mainly on ca 2.8 Ga crust at Pomiadluk Point. Hf-isotope data was collected...

Research paper thumbnail of Abstract: The Voisey’s Bay footprint - tracking the geochemical signal of magmatic Ni-Cu-Co sulphide mineralization in northern Labrador

Research paper thumbnail of Grain Size Fractionation of Detrital Zircon in an Ancient Deltaic Environment (Late Cretaceous Trinidad Sandstone and Pierre Shale, Raton Basin, Colorado): Implications for U-PB Zircon Provenance Studies

Geological Society of America Abstracts with Programs, 2019

Research paper thumbnail of The secret magmatic history of Archean anorthosites told by Lead isotopes in plagioclase

Research paper thumbnail of Origin of Hree-Depleted Archean Dacites: A Case Study from the

Research paper thumbnail of Determinations of Platinum-Group Element (PGE) Distributions Using Whole-rock, SEM, EMPA, Image Analysis, and LA-ICP-MS Techniques in the Kelly Lake Ni-Cu-PGE Deposit, Sudbury

The Kelly Lake deposit is a Ni-Cu-PGE offset-style deposit that occurs at the south end of the Co... more The Kelly Lake deposit is a Ni-Cu-PGE offset-style deposit that occurs at the south end of the Copper Cliff Offset (CCO), Sudbury. The deposit consists of four ore bodies (710, 720, 725, and 740) that were first identified in 1997 and contain a published 10.5 million tonnes of ore at 1.77% Ni, 1.34% Cu, and 3.6 g/tonne combined Pt + Pd + Au. The ore bodies have a sub-vertical orientation and plunge to the south. The CCO consists of an inclusion-and sulfide-poor marginal zone of quartz diorite (QD) and an inclusion- and sulfide-rich core of QD. The sulfide assemblage is similar to other deposits along the CCO, comprising pentlandite (Pn), pyrrhotite (Po), and chalcopyrite (Ccp) with minor pyrite (Py) and trace amounts of galena [PbS]. The platinum-group mineral assemblage consists of michenerite [(Pd,Pt)BiTe], sperrylite [PtAs2], and microinclusions of hollingworthite [(Rh,Pt,Pd)AsS] and ruarsite [RuAsS], which are associated with the bismuth-telluride, tsumoite [BiTe] and the sulfar...

Research paper thumbnail of Laser-ablation-ICPMS in the Earth Sciences: principles and applications

Quaternary Science Reviews, 2002

Research paper thumbnail of An Analogue Mission in Support of Moonrise and Other Sample Return Missions to the South Pole-Aitken Basin

Research paper thumbnail of Abstract: LAM-ICP-MS geochronological studies from the Botwood Basin and Buchans areas, Newfoundland

Research paper thumbnail of Significance of U-Pb detrital zircon geochronology for mudstone provenance

Geology, Mar 8, 2022

Detrital zircon U-Pb studies of mudstone provenance are rare but may preferentially fingerprint d... more Detrital zircon U-Pb studies of mudstone provenance are rare but may preferentially fingerprint distal zircon sources. To examine this issue, Pierre Shale and Trinidad Sandstone deposited in a Late Cretaceous deltaic environment in the Raton Basin, Colorado (USA), were measured for detrital zircon U-Pb age by laser ablation-inductively coupled plasma-mass spectrometry. Two major detrital zircon age peaks at ca. 70 and 1690 Ma are found in both Pierre Shale and Trinidad Sandstone but in inversely varying proportions: 68% and 16%, respectively, for the finest zircon fraction (∼15-35 μm) in the shale, and 25% and 32%, respectively, for the coarsest zircon fraction (∼60-80 μm) in the sandstone. Proximal sources in the Sangre de Cristo Mountains, directly west of the Raton Basin, contain coarse-grained, ca. 1690 Ma zircon, whereas distal sources in Laramide uplifts and basins in Colorado, New Mexico, and Arizona contain fine-grained, ca. 70 Ma zircon. The results indicate that U-Pb zircon provenance of mudstone reflects availability of volcanic and other fine-grained source rocks rather than simply distal sources. U-Pb zircon provenance studies should routinely include mudstone units because these units may identify fine-grained zircon sources more reliably than sandstones alone.

Research paper thumbnail of U-Pb Geochronology and Geochemistry of the Povungnituk Group of the Cape Smith Belt: Part of a Craton-Scale Circa 2.0 Ga Minto-Povungnituk Large Igneous Province, Northern Superior Craton

Lithos, 2018

Magmatism of the Povungnituk Group of the Cape Smith Belt, northern Superior craton, was formed i... more Magmatism of the Povungnituk Group of the Cape Smith Belt, northern Superior craton, was formed in three stages: (i) early alkaline magmatism and associated carbonatites (undated), (ii) a main flood basalt sequence (Beauparlant Formation) (constrained between 2040-1991 Ma), and (iii) a late stage alkaline pulse (Cecilia Formation) (ca. 1959 Ma). We suggest that the main stage of magmatic activity (middle pulse) was of short duration. A new U-Pb baddeleyite age of 1998±6 Ma is obtained from a dolerite sill intruding the uppermost section of the Beauparlant Formation. This age has regional significance because it matches the previously obtained 1998±2 Ma age for the Watts Group (Purtuniq) ophiolite of the northern Cape Smith Belt and the 1998±2 Ma U-Pb age of the Minto dykes intruding the craton to the south. These coeval units, along with additional units correlated on paleomagnetic grounds (Eskimo Formation), are interpreted to define a large igneous province (LIP), extending over an area of >400,000 km 2 , which we herein define as the Minto-Povungnituk LIP. Geochemical comparison between the Watts Group ophiolite, Minto dykes and the mafic Povungnituk Group shows significant differences allowing these data to be divided into two groups and domains within the LIP. A northern domain, comprising the Povungnituk and Watts groups, shows mixing between a depleted mantle source and a more enriched mantle plumesourced melt. A southern domain comprising the Minto dykes and the paleomagnetically linked Eskimo Formation shows signs of an even more enriched source, while these magmas also show the effect of crustal contamination.

Research paper thumbnail of Variations in zircon Hf isotopes support earliest Proterozoic Wilson cycle tectonics on the Canadian Shield

Precambrian Research, 2016

Sedimentary basins provide an archive of magmatic and tectonic events in their detrital zircon re... more Sedimentary basins provide an archive of magmatic and tectonic events in their detrital zircon record, which can be dated and coupled with Hf isotopic data to reveal secular changes in the production of juvenile and evolved magmatism and track the history of orogenic events. The Rae craton, which forms a substantial portion of the northern Canadian Shield, experienced successive orogenic events along its margins during most of the Paleoproterozoic Era. Yet, some of these orogenic events are poorly defined and their details remain controversial. We present coupled detrital zircon U-Pb age and εHf data from Paleoproterozoic metasedimentary successions of the eastern Rae craton. The zircon preserve an archive of ~600 million years of magmatic and tectonic history on the Rae craton and its periphery. The U-Pb and Hf isotopic data indicate that zircon provenance was dominantly from the northern and western Rae craton, where magmatic and tectonic activity was focused during the ~2.5 to 2.3 Ga Arrowsmith orogeny and the 2 ~2.0 to ~1.93 Ga Taltson and Thelon events. Our detrital zircon dataset holds a more complete record of these Proterozoic orogenic events than is currently defined from known and dated crustal rocks on the Rae craton and shows that juvenile magmatism is more common than current models for either event suggest. Notably, an inverted U or horseshoe-shaped εHf array (-15.5 to +5.0) in our zircon dataset reflects a Wilson cycle that began in the earliest Paleoproterozoic on the Rae craton.

Research paper thumbnail of Tectonic significance of bimodal volcanism in the Archean Michipicoten greenstone belt, Ontario

In the lower volcanic cycle (2750 Ma old) of the Michipicoten greenstone belt, Ontario, a basal m... more 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

Research paper thumbnail of Rhyolitic components of the Michipicoten greenstone belt, Ontario: Evidence for late Archaen intracontinental rifts or convergent plate margins in the Canadian Shield?

Rhyolitic rocks often are the dominant felsic end member of the biomodal volcanic suites that cha... more 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.

Research paper thumbnail of Paleodrainage reconstruction using Pb isotopes in K-feldspar sand grains: Examples from the NW European Triassic

The Pb isotopic composition of detrital K-feldspar is a powerful means of constraining sandstone ... more 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.

Research paper thumbnail of Detrital Zircons From the Jack Hills and Mount Narryer, Western Australia: Geochronological, Morphological, and Geochemical Evidence for Diverse >4000 Ma Source Rocks

Detrital zircons from all major clastic units in the Jack Hills and Mount Narryer metasedimentary... more 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

Research paper thumbnail of Heterogenous and Fractionated Metal in Canyon Diablo (IA) Graphite-Metal Rock

LPI, Mar 1, 2000

Introduction: Iron meteorites are widely believed to be igneous rocks derived from cores or impac... more Introduction: Iron meteorites are widely believed to be igneous rocks derived from cores or impact melt pools of planetesimals. In any case, iron meteorites allegedly formed by crystallization from a metal melt [e.g., 1-4]. On the other hand, it is known for a long time that iron meteorites are very old and carry abundant signs of primitiveness, like daughter nuclei of short-lived radioactive parents [5-11]. Inclusions of minerals and rocks in iron meteorites are common and clearly indicate that metal and inclusions (silicates, sulfides, oxides, phosphides, carbides, etc.) must have been brought together in the solid state. A liquid metal-solid xenocryst/xenolith mixing would not have worked as surface tension of the liquid metal and any gravity field would have quickly separated these phases [e.g., 12]. In addition, the fractionation trends exhibited by the chemical groups require different solid metal/liquid metal distribution coefficients [e.g., 3]. In order to overcome these problems, complex fractional crystallization-mixing models have been proposed [e.g., 4,13,14]. Recently, very clear evidence was found for a sub-solidus formation of IAB iron meteorites [e.g., 15-17]. Previous findings of inhomogeneous distribution of Ir in some iron meteorites [18-20] already gave a strong signal in favor of a low temperature origin of at least some iron meteorites. Here we report on the investigation of metal present in a graphite-metal rock from the Canyon Diablo (IA) iron meteorite. The results extend those obtained previously on a similar graphite nodule [21] and show that metals with highly different trace element contents co-exist on a sub-mm scale.

Research paper thumbnail of U/Pb geochronology of fossil fish dentine from Romualdo Formation, Araripe Basin, northeast of Brazil

Journal of South American Earth Sciences, 2022

Research paper thumbnail of Abstract: Provenance and paleodrainage patterns of Late Jurassic to Early Cretaceous synrift sandstones in the Flemish Pass Basin, offshore Newfoundland

Syn-rift sandstone from two industry exploratory wells in the Flemish Pass Basin, offshore Newfou... more Syn-rift sandstone from two industry exploratory wells in the Flemish Pass Basin, offshore Newfoundland, was studied for provenance analysis. The sandstone units were deposited during the Late Jurassic to Early Cretaceous (Tithonian and Neocomian) North Atlantic rifting stage, during which rifting intensified between Iberia and the Grand Banks, culminating in seafloor spreading between these continental blocks. The major sources of first-cycle detritus, based on U-Pb geochronology of detrital zircon, qualitative analysis of detrital zircons and chemical discrimination of detrital tourmalines, include the Late Neoproterozoic (650–600 Ma) arc-phase igneous rocks of the Avalon Zone as well as the Ordovician to Early Devonian (400–460 Ma) Taconic and Acadian magmatic rocks and metasedimentary rocks present in the Central Mobile Belt. Also, a large component of the source material is interpreted to be recycled, as indicated by significant populations of rounded detrital zircons and enric...

Research paper thumbnail of Abstract: LA-ICPMS measurements of gold abundance in sulphide and rock-forming minerals from granitoids, southwestern New Brunswick, Canada: insights into the genesis of intrusion-related gold systems

The abundances of gold and selected trace elements in magmatic sulphide and rock-forming minerals... more The abundances of gold and selected trace elements in magmatic sulphide and rock-forming minerals from SilurianDevonian granitoids in southwestern New Brunswick, a part of Canadian Appalachians, were quantitatively analyzed by laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICPMS). Major elements in these minerals were analyzed by electron microprobe. Gold is mainly hosted in sulphide minerals (i.e., chalcopyrite, pyrrhotite, and pyrite) as sub-micron inclusions (nano-nuggets). Gold in major rock-forming minerals (i.e., plagioclase, K-feldspar, biotite, hornblende, muscovite) and oxides (i.e., magnetite, ilmenite) are undetectable (< 0.02 ppm). Gold distribution coeffi cients between sulphide minerals and granitoid melt are empirically established as:

Research paper thumbnail of Abstract: In situ Hf-isotope zircon data from two Paleoproterozoic bimodal volcanic segments of the Aillik Group, Makkovik Province, Labrador

The Makkovik Province of eastern Labrador is part of an accretionary orogenic belt that formed du... more The Makkovik Province of eastern Labrador is part of an accretionary orogenic belt that formed during the Paleoproterozoic Makkovikian orogeny. The Aillik domain of the Makkovik Province is largely composed of: a) the Aillik Group, a package of Paleoproterozoic, polydeformed, bimodal volcano-sedimentary rocks, and b) abundant variably deformed Paleoproterozoic intrusive suites that intrude the Aillik Group. Two areas are the focus of this study. Middle Head is dominated by lower amphibolite facies arkosic sandstone, felsic tuff, rhyolite and basalt. Pomiadluk Point is composed primarily of lower amphibolite to upper greenschist facies felsic tuff and polymictic conglomerate with lesser preserved rhyolite and basalt. Recent detailed 1:10 000 scale bedrock mapping in conjunction with in situ Hf-isotopic geochemistry of zircon illustrate that the Aillik Group was deposited on ca 2.5 Ga crust at Middle Head, and mainly on ca 2.8 Ga crust at Pomiadluk Point. Hf-isotope data was collected...

Research paper thumbnail of Abstract: The Voisey’s Bay footprint - tracking the geochemical signal of magmatic Ni-Cu-Co sulphide mineralization in northern Labrador

Research paper thumbnail of Grain Size Fractionation of Detrital Zircon in an Ancient Deltaic Environment (Late Cretaceous Trinidad Sandstone and Pierre Shale, Raton Basin, Colorado): Implications for U-PB Zircon Provenance Studies

Geological Society of America Abstracts with Programs, 2019

Research paper thumbnail of The secret magmatic history of Archean anorthosites told by Lead isotopes in plagioclase

Research paper thumbnail of Origin of Hree-Depleted Archean Dacites: A Case Study from the

Research paper thumbnail of Determinations of Platinum-Group Element (PGE) Distributions Using Whole-rock, SEM, EMPA, Image Analysis, and LA-ICP-MS Techniques in the Kelly Lake Ni-Cu-PGE Deposit, Sudbury

The Kelly Lake deposit is a Ni-Cu-PGE offset-style deposit that occurs at the south end of the Co... more The Kelly Lake deposit is a Ni-Cu-PGE offset-style deposit that occurs at the south end of the Copper Cliff Offset (CCO), Sudbury. The deposit consists of four ore bodies (710, 720, 725, and 740) that were first identified in 1997 and contain a published 10.5 million tonnes of ore at 1.77% Ni, 1.34% Cu, and 3.6 g/tonne combined Pt + Pd + Au. The ore bodies have a sub-vertical orientation and plunge to the south. The CCO consists of an inclusion-and sulfide-poor marginal zone of quartz diorite (QD) and an inclusion- and sulfide-rich core of QD. The sulfide assemblage is similar to other deposits along the CCO, comprising pentlandite (Pn), pyrrhotite (Po), and chalcopyrite (Ccp) with minor pyrite (Py) and trace amounts of galena [PbS]. The platinum-group mineral assemblage consists of michenerite [(Pd,Pt)BiTe], sperrylite [PtAs2], and microinclusions of hollingworthite [(Rh,Pt,Pd)AsS] and ruarsite [RuAsS], which are associated with the bismuth-telluride, tsumoite [BiTe] and the sulfar...

Research paper thumbnail of Laser-ablation-ICPMS in the Earth Sciences: principles and applications

Quaternary Science Reviews, 2002

Research paper thumbnail of An Analogue Mission in Support of Moonrise and Other Sample Return Missions to the South Pole-Aitken Basin

Research paper thumbnail of Abstract: LAM-ICP-MS geochronological studies from the Botwood Basin and Buchans areas, Newfoundland

Research paper thumbnail of Significance of U-Pb detrital zircon geochronology for mudstone provenance

Geology, Mar 8, 2022

Detrital zircon U-Pb studies of mudstone provenance are rare but may preferentially fingerprint d... more Detrital zircon U-Pb studies of mudstone provenance are rare but may preferentially fingerprint distal zircon sources. To examine this issue, Pierre Shale and Trinidad Sandstone deposited in a Late Cretaceous deltaic environment in the Raton Basin, Colorado (USA), were measured for detrital zircon U-Pb age by laser ablation-inductively coupled plasma-mass spectrometry. Two major detrital zircon age peaks at ca. 70 and 1690 Ma are found in both Pierre Shale and Trinidad Sandstone but in inversely varying proportions: 68% and 16%, respectively, for the finest zircon fraction (∼15-35 μm) in the shale, and 25% and 32%, respectively, for the coarsest zircon fraction (∼60-80 μm) in the sandstone. Proximal sources in the Sangre de Cristo Mountains, directly west of the Raton Basin, contain coarse-grained, ca. 1690 Ma zircon, whereas distal sources in Laramide uplifts and basins in Colorado, New Mexico, and Arizona contain fine-grained, ca. 70 Ma zircon. The results indicate that U-Pb zircon provenance of mudstone reflects availability of volcanic and other fine-grained source rocks rather than simply distal sources. U-Pb zircon provenance studies should routinely include mudstone units because these units may identify fine-grained zircon sources more reliably than sandstones alone.

Research paper thumbnail of U-Pb Geochronology and Geochemistry of the Povungnituk Group of the Cape Smith Belt: Part of a Craton-Scale Circa 2.0 Ga Minto-Povungnituk Large Igneous Province, Northern Superior Craton

Lithos, 2018

Magmatism of the Povungnituk Group of the Cape Smith Belt, northern Superior craton, was formed i... more Magmatism of the Povungnituk Group of the Cape Smith Belt, northern Superior craton, was formed in three stages: (i) early alkaline magmatism and associated carbonatites (undated), (ii) a main flood basalt sequence (Beauparlant Formation) (constrained between 2040-1991 Ma), and (iii) a late stage alkaline pulse (Cecilia Formation) (ca. 1959 Ma). We suggest that the main stage of magmatic activity (middle pulse) was of short duration. A new U-Pb baddeleyite age of 1998±6 Ma is obtained from a dolerite sill intruding the uppermost section of the Beauparlant Formation. This age has regional significance because it matches the previously obtained 1998±2 Ma age for the Watts Group (Purtuniq) ophiolite of the northern Cape Smith Belt and the 1998±2 Ma U-Pb age of the Minto dykes intruding the craton to the south. These coeval units, along with additional units correlated on paleomagnetic grounds (Eskimo Formation), are interpreted to define a large igneous province (LIP), extending over an area of >400,000 km 2 , which we herein define as the Minto-Povungnituk LIP. Geochemical comparison between the Watts Group ophiolite, Minto dykes and the mafic Povungnituk Group shows significant differences allowing these data to be divided into two groups and domains within the LIP. A northern domain, comprising the Povungnituk and Watts groups, shows mixing between a depleted mantle source and a more enriched mantle plumesourced melt. A southern domain comprising the Minto dykes and the paleomagnetically linked Eskimo Formation shows signs of an even more enriched source, while these magmas also show the effect of crustal contamination.

Research paper thumbnail of Variations in zircon Hf isotopes support earliest Proterozoic Wilson cycle tectonics on the Canadian Shield

Precambrian Research, 2016

Sedimentary basins provide an archive of magmatic and tectonic events in their detrital zircon re... more Sedimentary basins provide an archive of magmatic and tectonic events in their detrital zircon record, which can be dated and coupled with Hf isotopic data to reveal secular changes in the production of juvenile and evolved magmatism and track the history of orogenic events. The Rae craton, which forms a substantial portion of the northern Canadian Shield, experienced successive orogenic events along its margins during most of the Paleoproterozoic Era. Yet, some of these orogenic events are poorly defined and their details remain controversial. We present coupled detrital zircon U-Pb age and εHf data from Paleoproterozoic metasedimentary successions of the eastern Rae craton. The zircon preserve an archive of ~600 million years of magmatic and tectonic history on the Rae craton and its periphery. The U-Pb and Hf isotopic data indicate that zircon provenance was dominantly from the northern and western Rae craton, where magmatic and tectonic activity was focused during the ~2.5 to 2.3 Ga Arrowsmith orogeny and the 2 ~2.0 to ~1.93 Ga Taltson and Thelon events. Our detrital zircon dataset holds a more complete record of these Proterozoic orogenic events than is currently defined from known and dated crustal rocks on the Rae craton and shows that juvenile magmatism is more common than current models for either event suggest. Notably, an inverted U or horseshoe-shaped εHf array (-15.5 to +5.0) in our zircon dataset reflects a Wilson cycle that began in the earliest Paleoproterozoic on the Rae craton.

Research paper thumbnail of Tectonic significance of bimodal volcanism in the Archean Michipicoten greenstone belt, Ontario

In the lower volcanic cycle (2750 Ma old) of the Michipicoten greenstone belt, Ontario, a basal m... more 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

Research paper thumbnail of Rhyolitic components of the Michipicoten greenstone belt, Ontario: Evidence for late Archaen intracontinental rifts or convergent plate margins in the Canadian Shield?

Rhyolitic rocks often are the dominant felsic end member of the biomodal volcanic suites that cha... more 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.

Research paper thumbnail of Paleodrainage reconstruction using Pb isotopes in K-feldspar sand grains: Examples from the NW European Triassic

The Pb isotopic composition of detrital K-feldspar is a powerful means of constraining sandstone ... more 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.

Research paper thumbnail of Detrital Zircons From the Jack Hills and Mount Narryer, Western Australia: Geochronological, Morphological, and Geochemical Evidence for Diverse >4000 Ma Source Rocks

Detrital zircons from all major clastic units in the Jack Hills and Mount Narryer metasedimentary... more 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