Nick W. Rogers

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Verified

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• PhD (London), BSc(London)
• Professor Emeritus at The Open University

The initial interaction between material rising from the African Large Low Shear Velocity Province and the African lithosphere manifests as the Eocene continental large igneous province (LIP), centered on southern Ethiopia and northern Kenya. Here we present a geographically well-distributed geochemical dataset comprising the flood basalt lavas of...

Mt. Takahe is a large, late Quaternary trachyte shield volcano that rises through 2000 + m of the West Antarctic ice sheet. It is composed mostly of ne-trachyte, hy-ol-trachyte, and qz-trachyte flows, with subordinate basanite, intermediate rocks, and pantellerites. All rock types can be adequately modeled by fractional crystallization of basanite...

Basalt-trachyte volcanoes in the Marie Byrd Land (MBL) Cenozoic province lie along the Amundsen Sea coast on the north flank of the West Antarctic rift. Basalts here are characterized by OIB-like geochemistry, restricted ranges of 87Sr/86Sr (0.702535 – 0.703284) and 143Nd/144Nd (0.512839–0.513008) and a wide range of 206Pb/204Pb (19.357–20.934).

Bunburra Rockhole is a unique basaltic achondrite that has many mineralogical and petrographic characteristics in common with the noncumulate eucrites, but differs in its oxygen isotope composition. Here, we report a study of the mineralogy, petrology, geochemistry, and chronology of Bunburra Rockhole to better understand the petrogenesis of this m...

Basalt dykes from the regional dyke swarm of the British Palaeogene Igneous Province (BPIP) were emplaced parallel to structural lineaments linking onshore and offshore volcanic edifices. Basalts that underwent minimal interaction with the crust have Mg# 60–75, εNd58 c. 8, 206Pb/204Pb c. 17.5, δ18O 5.9 ± 0.3‰, and 87Sr/86Sr <0.7040. Basalts with co...

The Plinian eruption in October 1902 of 8.5 km ³ of dacitic pumice and minor basaltic andesite scoria and ash at Volcán de Santa María, Guatemala violently interrupted a 25 kyr period of repose that had followed ∼75 kyr of cone-growth via extrusion of 8 km ³ of basaltic andesite lava. Two-oxide and pyroxene thermometry reveal an oxidized (Ni-NiO+2...

Cenozoic volcanism within Mongolia forms part of a large central Asian province of intra-plate magmatism. Numerous small-volume volcanic cones and alkali basalt lava flows have been formed since c. 30Ma; from c. 12 Ma activity has been focused on the uplifted Hangai dome. A mechanism for melting beneath the dome has, however, thus far remained enig...

We measured trace element concentrations in Nantan, Toluca, Cape York, Carthage, Gibeon and Dronino. Poikiloblastic daubreelite in Gibeon indicates shock metamorphism. There is a volatile depletion in metal and sulphides.

High-grade migmatitic and mylonitic gneisses from the Day Nui Con Voi massif in northern Vietnam record temperatures of 760–810 °C at pressures of 6–10 kbars. High temperature conditions have resulted in the development of major element diffusional profiles in garnet. Laser ablation ICP-MS analyses of trace elements indicate that REE and Hf closely...

The earliest basalts erupted by largest mantle plumes are typically hotter than those derived from convecting upper mantle at mid-ocean ridges. They originate from a thermal boundary layer deep in Earth that is assumed to be the core-mantle boundary. Consequently the first plume-derived basalts provide constraints on Earth structure and differentia...

We present new compositional data on samples of the high-Ti/Y Paranapanema and Pitanga basaltic magma types from the northern and western parts of the Early Cretaceous Paraná flood basalt province in South America. A comparison of whole rock compositions with ol-plag-cpx cotectics allows crystallization pressures to be estimated for both magma type...

The Marie Byrd Land province includes 18 large (up to 1,800km3) central volcanoes distributed across an active volcano-tectonic dome. The typical volcano structure consists of a basal 1,000–5,000m of basanite surmounted by trachyte and subordinate intermediate rocks, plus phonolite, or pantellerite, or comendite. The volumes of felsic sections are...

Prior to the ad 1902 Plinian eruption of 8 km(3) of dacite and subsequent growth of the > 1 km(3) Santiaguito dacite dome complex, Santa Maria volcano grew into an 8 km(3) composite cone over similar to 75 kyr in four phases (at 103-72, 72, 60-46, and 35-25 ka). The 1902 eruption occurred after an similar to 25 kyr period of repose in growth of the...

U–Pb analyses of rutile and titanite commonly yield ages that constrain the timing of cooling rather than the timing of their crystallization. Rutile which grew at or close to peak temperature conditions in a mafic granulite, intermediate granulite and mafic amphibolite within juxtaposed litho/tectonostratigraphic units in the Greater Himalayan Seq...

New major- and trace-element data of bulk-rocks and constituent minerals, and whole-rock Re–Os isotopic compositions of samples from the Lherz Massif, French Pyrenees, reveal complex petrological relationships between the dominant lithologies of lherzolite ± olivine-websterite and harzburgite. The Lherz peridotite body contains elongate, foliation...

Isotopic variations in lavas from regions of low tectonic extension, such as the western branch of the East African Rift (EAR), can be used to probe regional variability in the underlying continental lithospheric mantle. Volcanic rocks from the western branch of the EAR are isotopically among the most extreme young samples on Earth. Pb, Hf, Nd and...

Analyses of the Re–Os isotope system and PGE abundances have been used to investigate the timing and origin of mineralisation in the Vaal Reefs section of the Witwatersrand Basin, the world's largest gold deposit. Consistent interelement PGE fractionation in both organic and sulphide phases intimately associated with gold mineralisation suggests th...

New 238U-230Th and Sr isotope data from 40Ar/39Ar-dated mafic lavas of the composite cone, A.D. 1902 dacitic tephra, and 1922–present dacitic dome lavas from the Santa María–Santiaguito volcanic complex in northwestern Guatemala indicate that genesis of magma beneath the western end of the Central American volcanic arc requires sources much differe...

Variations in the Fe/Mn ratio and Osmium isotopes in magnesium-rich mafic rocks from plume-related volcanic provinces have been exploited to imply the entrainment of core material in mantle plumes and the involvement of ancient recycled oceanic lithosphere. Here we present new major and trace element, 187Os/188Os ratios and precise Fe/Mn ratios on...

The Foça volcanic centre (FVC) occupies a NNE-SSW-oriented highland between two EW-trending structural grabens in western Anatolia, and includes early-middle Miocene mafic and felsic extrusive suites. Its evolutionary history consists of an older volcano stage (16.6-16.1Ma) and a younger volcano stage (15.2-14.1Ma), which are characterized by diffe...

Gallium abundances, determined bylaser ablation-inductively coupled plasma-mass spectrometry, are presented for phenocrysts and glassy matrices from a metaluminous trachyte and five peralkaline rhyolites from the Greater Olkaria Volcanic Complex, Kenya Rift Valley. Abundances in the glasses range from 28.9 to 33.3 ppm, comparable with peralkaline r...

Spinel lherzolite xenoliths from Mont Brianc ßon, French Massif Central, retain evidence for multiple episodes of melt depletion and melt/fluid infiltration (metasomatism). Evidence for primary melt depletion is still preserved in the co-variation of bulk-rock major elements (MgO 38.7–46.1 wt.%; CaO 0.9–3.6 wt.%), and many samples yield unradiogeni...

Prior to the 1902 plinian eruption of 8 km3 of dacite, and subsequent >1 km3 growth of the Santiaguito dacite dome, Volcán Santa Maria grew into an 8 km3 composite cone over 67 ka in four phases (103, 74, 53, 36 ka), constrained by 40Ar/39Ar geochronology. The eruption of 1902 interrupted a 36 ka period of repose. To provide context for processes t...

One of the largest regions of Cenozoic intra-plate volcanism stretches across central Asia from the Baikal Rift in Siberia, through central Mongolia to China. In Mongolia this is expressed as numerous small-volume alkali-basaltic cones and lavas, erupted since ca. 30 Ma. Currently, accepted models of melt generation for intraplate magmatism, such a...

The Marie Byrd Land (MBL) volcanic province is associated with the rise of a large tectonomagmatic dome, over the past 25-30 m.y. Since 14-15 Ma, five volcanoes have produced pantellerites and three others have produced comendites. Together they display a range in SiO2, Al2O3, FeOt, and peralkalinity that is comparable with the full range of compos...

Following a 68 ka period of episodic cone-building via basaltic andesitic lava extrusion, and 36 ka of repose, Volcán Santa Maria erupted explosively 8 km3 of dacitic pumice with minor basaltic andesitic scoria and ash in October, 1902. Two-oxide and pyroxene thermometry reveal an oxidized (Ni-NiO+2 log units) and thermally-zoned magma body in whic...

Re-Os isotopes provide pertinent age information in the Lherz peridotite (the type locality of terrestrial mantle lherzolite), and are used to constrain the composition and evolution of bulk silicate Earth.

The Greater Olkaria Volcanic Complex is a young (20 ka) multi-centred system in the central Kenya Rift Valley, mainly represented at outcrop by peralkaline rhyolites. The rhyolites show significant compositional variation; peralkalinity [mol. (Na2O + K2O)/Al2O3] varies from 1·01 to 1·55, Zr contents from 442 to 3640 ppm and Rb contents from 262 to...

Pantellerites, trachytes, and phonolites, of mid-Miocene (~14Ma) to Holocene age, occur in close proximity to each other in 6 large felsic shield volcanoes along the coast of western Marie Byrd Land (MBL). Work on pantellerites in the Afar region of Ethiopia, a good analog for MBL, showed that low-pressure fractional crystallization of transitional...

The Greater Olkaria Volcanic Complex is a young (≤ 20 ka) multi-centred lava and dome field dominated by the eruption of peralkaline rhyolites. Basaltic and trachytic magmas have been erupted peripherally to the complex and also form, with mugearites and benmoreites, an extensive suite of magmatic inclusions in the rhyolites. The eruptive rocks com...

This undergraduate textbook integrates results from geophysics, geochemistry, and petrology to describe the structure, composition, and dynamic processes that operate throughout the solid Earth. It presents an Earth system science approach to studies of the Earth's interior and develops a global view of solid Earth cycles to explain geodynamic and...

Solution ICP-MS determinations for >32 elements from individual, well characterised Semarkona chondrules. Coarse grained chondrules are less abundant in volatile elements than fine grained. Type I and II chondrules have very similar compositions.

XRD, EBSD and solution ICP-MS analysis techniques have been combined to show that dark inclusions within Allende (CV3) were most likely formed and altered in the nebula and that their precursor material may have been Allende matrix-like material.

This study expands on the current bulk carbonaceous chondrite (CC) data set, using ICP-MS techniques. This precise and accurate technique provides an insight into volatile element depletion patterns in CCs, and a comparison between fall and find samples.

Germanium abundances, determined by laser ablation-inductively coupled plasma-mass spectrometry, are presented for phenocrysts and glass matrices from a metaluminous trachyte and four peralkaline rhyolites from the Greater Olkaria Volcanic Complex, Kenya Rift Valley, Africa. Abundances (in ppm) are: sanidine 0.45-0.61; fayalite 4.8-11.7; hedenbergi...

The massifs of the eastern Pyrenees have been the focus of a number of extensive studies and have made a significant contribution to our understanding of mantle composition and evolution. Specific problems remain, in particular the relationship between adjacent harzburgites and lherzolites, which have been proposed to be either; (1) melt depletion...

The enstatite chondrites are a group of metal- and sulphide-rich meteorites with a highly reduced composition. They have an oxygen isotope composition that is indistinguishable from that of the Earth-Moon system [1], and partly on this basis have been cited as model precursors for the Earth [2]. However, it has proven difficult to reconcile the bul...

Trace element and Sr-Nd-Pb isotope compositions of basaltic lavas from 11 volcanoes spanning 1300 km of the Aleutian Island arc provide new constraints on the recycling of elements in melts and fluids derived from subducted oceanic crust and sediment. Despite a nearly twofold variation in the flux of sediment subducted along the Aleutians, proxies...

The authors have used a high-purity multielement solution, containing known quantities of individual Pare earth elements, as a reference standard in neutron activation analysis of rare earths in several international standard rocks. The data obtained by the authors have been compared with those obtained using the international standard rock Basalt...

New data are presented for the analysis of the elements: REE, Na20, Fe2O3, Cr, Co, Rb, Cs, Ba, Hf, Ta, Th and Il in twenty-five less well known carbonate and industrial geological reference materials by instrumental neutron activation analysis. The materials include NBS 1c, 15e, 88a and 120b from the National Bureau of Standards, Washington DC; GFS...

Ion-microprobe analyses of the Li concentration and Li isotopic composition of zoned clinopyroxene and olivine phenocrysts from within primitive arc lavas from the New Georgia Group in the Solomon Islands reveal that both Li and δ7Li vary widely from rim to core. The Li content of the rims is between 2 and 8 times that of the cores whereas Li isoto...

The origins of Late Bronze Age glass artefacts found throughout the Mediterranean and Near and Middle East remain controversial. Previous analyses of major and minor elements in both Egyptian and Mesopotamian glasses have proven equivocal, revealing no significant compositional differences between glasses from these two regions. Here we present new...

The Katla subglacial caldera is one of the most active and hazardous volcanic centres in Iceland as revealed by its historical volcanic activity and recent seismic unrest and magma accumulation. A petrologic and geochemical study was carried out on a suite of mid-Pleistocene to Recent lavas and pyroclastic rocks originated from the caldera. The who...

Implications for volatile depletion from trace element composition of Allende matrix via micromill and solution ICP-MS.

We present in situ trace element data from both matrix and fine grained chondrule rims (FGRs) within a section of Vigarano (CV chondrite). LA-ICP-MS allows selection of specific sites for analysis-matrix and FGRs can be distinguished with ease.

Trace element and U-series isotope analyses are presented for a suite of recent (10×chondrite and the LREE between 60 and 200×chondrite. REE fractionation is consistent with melting a garnet lherzolite source region with between 2% and 6% modal garnet. Other trace element ratios are distinct from OIB, notably Zr/Hf which ranges from 43 to 48, whils...

Evaluating volcanic hazards requires knowledge of the processes that trigger eruptions and the nature and timing of geophysical signals related to these processes. One approach to addressing this need is to link geophysically observable signals (e.g., those related to seismic, aeromagnetic, inflationary, or degassing processes) to pre-eruptive magm...

St Kitts forms one of the northern group of volcanic islands in the Lesser Antilles arc. Eruptive products from the Mt Liamuiga centre are predominantly olivine + hypersthene-normative, low-K basalts through basaltic andesites to quartz-normative, low-K andesites. Higher-Al and lower-Al groups can be distinguished in the suite. Mineral assemblages...

U-series isotopes have been measured in the dissolved phase, suspended load and bedload of the main rivers draining basaltic catchments in Iceland. For the dissolved phase, (234U/238U) and (238U/230Th) range between 1.08 and 2.2, and 7.4 and 516, respectively. For the suspended load and bedload, (234U/238U) and (238U/230Th) range from 0.97 to 1.09...

The major and trace element and radiogenic isotope compositions of basalts from throughout the East African rift system are reviewed in the context of constraints from previous geophysical studies. The data indicate the presence of two mantle plumes, the East African and Afar plumes, which dynamically support the East African and Ethiopian plateaus...

Comprehensive major-, trace-element and rhenium–osmium (Re–Os) isotope data are presented for abyssal peridotites from Ocean Drilling Program (ODP) Leg 209, in the North Atlantic. The samples are from a single core (Site 1274A) located on the western wall of the axial rift valley of the Mid-Atlantic ridge, and their study allows elemental and isoto...

This study presents Os isotope and comprehensive major and trace element data for the dissolved load, suspended particulates and bedload for Icelandic rivers, draining predominantly basaltic catchments that range in age from historic to ca. 12 Ma. Hydrothermal waters and precipitation have also been analysed. Both Os and Re concentrations are great...

Comprehensive major-, trace-element and rhenium-osmium (Re-Os) isotope data are presented for abyssal peridotites from Ocean Drilling Program (ODP) Leg 209, in the North Atlantic. The samples are from a single core (Site 1274A) located on the western wall of the axial rift valley of the Mid-Atlantic ridge, and their study allows elemental and isoto...

Abyssal peridotites represent residual mantle that has lost variable but generally large amounts of melt, which subsequently forms mid-oceanic ridge basalts (MORB). Evidence suggests that much of this melting is very recent, and isotope variations that do exist are usually explained by compositional heterogeneity in the source rather than by age di...

Evaluating the potential role of crustal assimilation in modifying the compositions of flood basalt magmas is critical if we are to better understand the ultimate mantle origins and tectonic driving forces behind these immense episodes of melting. This question is particularly important for flood basalts such as the Early Cretaceous Paraná-Etendeka...

15th Annual Goldschmidt Conference (Moscow, ID)

Bulk chondritic meteorites and terrestrial planets show a monotonic depletion in moderately volatile and volatile elements relative to the Sun's photosphere and CI carbonaceous chondrites. Although volatile depletion was the most fundamental chemical process affecting the inner solar nebula, debate continues as to its cause. Carbonaceous chondrites...

We present a mathematical model for the evolution of the (226Ra/230Th) activity ratio during simultaneous fractional crystallization and ageing of magma. The model is applied to published data for four volcanic suites that are independently known to have evolved by fractional crystallization. These are tholeiitic basalt from Ardoukoba, Djibouti, MO...

Gneiss domes exposed by the North Himalayan antiform in southern Tibet provide evidence for protracted melting of the mid-crust during convergent tectonics. Anatexis was initiated during underthrusting and recurred during the southwards extrusion of a low-viscosity crustal sheet. Sr–Nd isotope systematics establish that the cores of the domes, domi...

A suite of peralkaline trachytes from Longonot volcano, Kenya, which erupted during the last 6000 years, has been analysed for major and trace elements, Pb and Nd isotopes, and U–Th–Ra disequilibria. The lavas are divided into three stratigraphic groups of trachytes (Lt2a, Lt2b and Lt3), and hybrid lavas, designated LMx1 and LMx2, which, respective...

In the marine environment, authigenic ferromanganese (Fe–Mn) oxides precipitate from seawater, incorporating many dissolved trace elements (such as Nd, Pb) whose isotopic composition is a direct proxy for ambient seawater. Thus, isotopic studies of the Fe–Mn oxyhydroxide component leached from sedimentary records can provide information on changes...

Diffusional smoothing of Fe–Mg compositional gradients in clinopyroxene crystals from the 1944 eruption of Vesuvius is used to determine the preeruption residence times of crystals at magmatic temperatures. The result is a distribution of crystal residence times from one sample that can be used to constrain magma chamber volumes. Diffusional zones...

We have analysed trace element volatiles in chondrules and matrix from Mighei. Chondrules in Mighei are depleted compared to matrix. The volatile fractionation pattern in both materials suggests differing degrees of incomplete condensation.

Lherzolite inclusions (with some harzburgite) from kimberlites are divided into depleted and fertile types according to their Mg/Fe ratio, and Al2O3, CaO, Na2O, and TiO2 content. The depleted (lithospheric) types, however, are enriched in LRE and incompatible elements contrasting with the deeper fertile (asthenospheric types) which have near chondr...

Granite sheets emplaced into the migmatite zone of the eastern contact aureole of the Bushveld Complex resulted from fluid-enhanced, incongruent biotite melting of the underlying Silverton Formation shales during prograde metamorphism. Ba concentrations are extreme in both the sheets (>1000 ppm) and the hornfels (>800 ppm) into which they have been...

Compositional differences in the present day characteristics of basalts derived from the Afar and East African (Kenyan) mantle plumes are well established, particularly for Sr and Nd isotopes. What is less clear is whether those differences existed during the earlier phases of plume activity or whether a single mantle source region can account for...

Silicate weathering is often considered as one of the most important sinks of atmospheric CO2 over geological timescales, but the palaeovariations of the silicate weathering rates are still debated and depend on the reliability of the chosen proxies. It has recently been suggested that Li isotopes significantly fractionate during continental erosio...

Pyroxenites are an important mantle lithology, comprising about 5% of the mantle. They may represent remnants of oceanic lithosphere streaked out by mantle convection, high-pressure cumulates, or the products of dynamic recrystallisation in melt conduits, according to current models. These give rise to different residual mineralogies, additionally...

Long-term oceanographic records of transition metal stable isotopes have demonstrated that there have been significant variations in the isotope composition of Fe, Cu and Zn. Speculation as to the course of the variation in Fe isotopes has focussed on the role of continental weathering and the release of dissolved metals into the oceans. Fractionat...

A recent study by Hodell et al. (2001) suggests that the carbonate record from ODP Site 1089 in the South Atlantic represents a qualitative, high resolution record of the temporal evolution of the deep-sea carbonate ion concentration. The carbonate content of these sediments is high during full glacial periods and lower during interglacial stages-...

Mantle plumes represent a major component of heat transfer within the mantle. They are thought to be instrumental in the process of continental break-up, and are likewise considered responsible for the associated voluminous outpourings of the basic lavas, which make up continental flood basalt provinces. The 660 km discontinuity and the core-mantle...

Analysis of trace elements in fossil foraminiferal tests is widely used by palaeoceanographers to reconstruct past environmental conditions in the oceans. However, there remain a number of problems associated with the interpretation of these trace element data. Firstly, there is a lack of understanding as to the controls on the uptake of trace elem...

We used laser ablation and solution ICP-MS to analyse the trace element composition of matrix in a range of carbonaceous chondrites. In most cases our results are broadly consistent with an incomplete condensation model of volatile fractionation.

Diffused barium compositional distributions in sanidines from the deposits of the AD472 (Pollena) eruption of Vesuvius were accurately measured at the micrometre scale using Back-Scattered Electron (BSE) microscopy. The profiles measured yield residence times of 40 years or less for a reasonable magmatic temperature of 905°C and imply growth rates...