Igneous Petrology Research Articles

A pedagogical approach to estimating the CO 2 budget of magmas

On a planetary scale, the carbon cycle describes the movement of carbon between the atmosphere and the deep Earth. Carbon species are involved in diverse Earth processes, ranging from sedimentary, metamorphic and igneous petrology to the long-term viability of life at the Earth's surface. Volcanoes, and their associated magmatic systems, represent the interface through which carbon is transferred from the deep Earth to the surface. Thus, quantifying the CO 2 budget of volcanic systems is necessary for understanding the deep carbon cycle and, concomitantly, the CO 2 budget of the near surface, including the atmosphere. In this review, Kilauea volcano (Hawaii) is used as a case study to illustrate simple calculations that can account for processes that affect the amount and distribution of CO 2 in this relatively well-studied volcanic system. These processes include methods to estimate the concentration of CO 2 in a melt derived by partial melting of a source material, enrichment of CO 2 in the melt during fractional crystallization, exsolution of CO 2 from a fluid-saturated melt, trapping and post-entrapment modification of melt inclusions, and outgassing from the volcanic edifice. Our goal in this review is to provide straightforward example calculations that can be used to derive first-order estimates regarding processes that control the CO 2 budgets of magmas and that can be incorporated into global carbon cycle models.

Geikie and the development of petrography, particularly in Scotland

Abstract The British Geological Survey (BGS) petrology collections contain almost 1500 Scottish rock samples (with thin sections) deposited by Archibald Geikie, including BGSS1, an analcime gabbro from Salisbury Crags, Edinburgh. High-quality thin section images are now available from the BGS's Britrocks online database. The geospatial distribution of these samples is analysed. They reflect the development of geological mapping and igneous petrology in Scotland from the 1850s to the 1890s. Geikie had the opportunity to study Nicol's original thin sections in 1851 and he met both Sorby and Zirkel, early pioneers of petrography. Lacking management support, he cut many of his own thin sections while mapping the Clyde Plateau lavas during the 1860s, leading to publications on Carboniferous and Tertiary volcanism. When appointed Director of the newly formed Geological Survey of Scotland in 1867, he was able to establish a petrological laboratory in Edinburgh. Time pressures resulting from his subsequent promotion to Director-General, and increasing quantities of metamorphic rocks, then necessitated the appointment of Hatch and Teall as petrographers for the Survey. Teall's work was particularly important in the detailed petrography of the gneisses and mylonites associated with the Highlands Controversy.

About this title - Paleozoic–Mesozoic Geology of South Island, New Zealand: Subduction-related Processes Adjacent to SE Gondwana

This volume presents a set of research papers that provide new data and interpretations of the Permian–Triassic terranes of SE Gondwana, now exposed in South Island, New Zealand. Following an introduction for general readers, a historical summary and a review of biostratigraphy, the individual papers primarily focus on the Permian magmatic arc of the Brook Street Terrane, the classic Permian Dun Mountain ophiolite and the Permian–Triassic Maitai Group sedimentary succession. The new results emphasize the role of subduction and terrane displacement adjacent to the Permo-Triassic Gondwana margin, and present fundamental insights into three crustal processes: subduction initiation, supra-subduction zone oceanic crust genesis and forearc basin evolution. The volume concludes with a wide-ranging summary and synthesis of the regional Cambrian to Early Cretaceous tectonostratigraphy of New Zealand's South Island in relation to the wider areas of Zealandia, East Australia and West Antarctica. The volume will interest geoscientists, including stratigraphers, sedimentologists, palaeontologists, igneous petrologists, geochemists, geochronologists and economic geologists, and is aimed at professional geologists and advanced students of geology.

Igneous petrology, zircon geochronology and geochemistry of multiply emplaced granitoid bodies from the Palaeoproterozoic Usagaran domain in central Tanzania

This study reports igneous petrology, zircon ages and geochemistry for Palaeoproterozoic I-type granitic, granodioritic, Qtz-monzonitic, Qtz-monzodioritic and monzodioritic rocks from the Usagaran domain of southwestern Tanzania. These rocks can be subdivided into three groups according to their age, T-t evolution and geochemistry. The oldest group is made up of amphibolite-facies calcic-alkalic gneisses, ranging in age between ∼1984 and ∼1910 Ma, which have been divided into two subgroups regarding their T-t evolution. The first subgroup shows a constant increase in T, and the second subgroup first shows a decrease in T, followed by an increase in T. The second group consists of alkalic to calcic-alkalic greenschist- and/or amphibolite-facies gneisses that vary in age between ∼1895 and ∼1863 Ma. This group could also be subdivided regarding its T-t evolution. The first subgroup experienced an increase in T, followed by a decrease in T, whereas the second subgroup shows a constant decrease in T-t conditions. The third group consists of slightly deformed gneisses ranging in age between ∼1847 and ∼1817 Ma. The T-t evolution of these rocks is indicative of a decrease in T, followed by an increase in T.We interpret the different T-t paths, coupled with the emplacement of several granitoid bodies over a time period of ∼170 Ma, as a history of multiple injection of granitoid bodies into Archaean and early Palaeoproterozoic crustal material as indicated by zircon xenocrysts. This is also suggestive of a continuation of the Archaean Tanzania craton into the lower crust of the Usagaran domain. We explain the geochemical differences as well as the various T-t paths as an interaction between granitoid melts with primary arc basaltic magma signatures originating by partial melting from a hydrated mantle wedge above a downgoing slab. The interaction between these primary magmas with more differentiated magmas can produce various combinations of assimilation, differentiation, fractionation, crystallization and magma mixing. We conclude that large parts of the Usagaran domain formed during magmatism at different times and at different locations. The granitoid precursors are interpreted to have formed in a continental arc environment during the continent-wide Eburnian crust-forming event.

Timescales of magmatic differentiation from alkali basalt to trachyte within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia

A fundamental goal of igneous petrology is to quantify the duration of time required to produce evolved magmas following influx of basalt into the crust. However, in many cases, complex field relations and/or the presence of a long-lived magmatic system make it difficult to assess how basaltic inputs relate to more evolved magmas, therefore, precluding calculation of meaningful timescales. Here, we present field relations, geochemistry, 40Ar/39Ar ages, and 36Cl ages for volcanic rocks from the Harrat Rahat volcanic field, Saudi Arabia. These data document a systematic and repeated temporal progression from alkali basalt to trachyte for the youngest eruptives. From ~ 150 to ~ 17 ka the following eruptive sequence occurred four times: (1) alkali basalt, (2) hawaiite, mugearite, or benmoreite, and (3) trachyte. We interpret each eruptive sequence to result from injection of basalt into the crust, and its subsequent differentiation and eruption of progressively evolved magmas. We use the interval time between successive eruptions within a given sequence to calculate the duration of time required to produce trachyte from alkali basalt. Differentiation from alkali basalt to intermediate compositions (hawaiite, mugearite, benmoreite) took ≤ 2 kyr on average. Differentiation from intermediate compositions to trachyte took a maximum of 6.6 ± 3.5 to 22.5 ± 1.6 kyr. Thus, the total duration of differentiation was ~ 9 to ~ 25 kyr. Timescales presented here are insensitive to processes evoked to drive differentiation because they are based solely on the ages and compositions of eruptive products from a system characterized by a simple, repeated differentiation sequence.

Magmatic-hydrothermal evolution at the Lyangar redox-intermediate tungsten-molybdenum skarn deposit, western Uzbekistan, Tien Shan: Insights from igneous petrology, hydrothermal alteration, and fluid inclusion study

The Lyangar W-Mo skarn deposit is situated in a metallogenic belt of W-Mo, Cu-Mo, W-Au, and Au deposits and is related to an Early Permian multiphase (monzodiorite)-granodiorite-granite-leucogranite pluton that was emplaced in a tectonic domain with possible ancient continental crust. The latter, coupled with an inferred ascent of hot asthenospheric material, has defined an enrichment in Mo and fluorine, together with W and Au, to form a distinct metallogenic assemblage in a post-collisional environment. The parental moderately- to high-K, transitional metaluminous to peraluminous, weakly oxidized-weakly reduced, ilmenite-titanite-series granitoids are accompanied by hydrothermal alteration and mineralization that formed in redox-intermediate environment.The deposit incorporates prograde and retrograde pyroxene and garnet skarns composed of hedenbergitic pyroxene and grossular- to almandine+spessartine-rich garnet, respectively. Fluorite is present in the retrograde skarn together with scheelite and sulfides, the latter including most abundant pyrrhotite and molybdenite. Hydrosilicate (amphibole-epidote-chlorite-quartz, locally with albite, sulfides, and scheelite) assemblage has limited development. Phyllic (quartz-sericite-Fe-carbonate, locally with albite, fluorite, scheelite, and sulfides, also Bi and Au minerals) alteration assemblage partially overprints altered skarns and extends over much larger areas. Overall, the deposit represents a superposition of the early W-Mo mineralization related to retrograde skarn and hydrosilicate alteration, and the late Au-W-Cu-Bi mineralization in phyllic alteration assemblages.Prograde and retrograde skarns were formed from dominantly magnesian-sodic-chloride, moderately-saline (11.7–13.9 wt% to 8.6–10.5 wt% NaCl-eq.), high pressure (1500 to 1350 bars), hot aqueous fluids that were followed by moderately-saline (12.3–14.5 wt% NaCl-eq.), Ca-rich, lower pressure (600 bars) fluids during deposition of most scheelite. Hydrosilicate (propylitic) assemblages were formed from boiling fluids at the temperatures of 380–430 °C and pressures of 600±300 bars, whereas phyllic alteration assemblages - from boiling carbonic-aqueous, low-salinity fluids at the temperatures of 300–320 °C and pressures of ~1000 bars. δ18OH2O values range from +7.8 to +8.6‰ for retrograde skarn, and from +6.6 to +7.0‰ for phyllic alteration, whereas δ13CCO2- from −3.3 to −0.5‰ for retrograde skarn, and from −5.5 to −4.5‰ for phyllic alteration. δ34S increases from retrograde skarn (δ34S = +2.0 to +2.3‰) to phyllic alteration (δ34S = +4.3 to +4.6‰) stages.

Trajan's Forum (Hemicycle) and the Via Biberatica (Trajan's Markets): an HHpXRF Study of the Provenance of Lava Paving in Ancient Rome (Italy)

This paper reports on geochemical data collected using a He‐enabled handheld portable XRF (HHpXRF) from lava paving stones in Trajan's Forum (Hemicycle) and the Via Biberatica (Rome). Issues relating to HHpXRF field use and calibration are also addressed in detail. By means of this instrument, 355 analyses of the paving stones were collected and the data were processed using the standard techniques of igneous petrology and petrography. Provenancing was based on comparisons between the HHpXRF data and geological data from the abundant literature on Roman volcanic rocks. These comparisons placed the provenance of the paving stones in the Colli Albani, south‐east of Rome. Further analysis using Zr/Y versus Nb/Y discriminant diagrams suggests that the paving stones were quarried from two sources, both of which are represented in Trajan's Forum and the Via Biberatica. The diagrams suggest that the sources lie within the Faete and Vallerano lava complexes. The latter were probably transported to the construction site by barge on the River Tiber and the former were easily accessible by carts along the Via Appia. The study establishes the potential of HHpXRF equipment for non‐destructive analysis of paving stones both in Rome and at other sites in central Italy, and challenges a number of assumptions about the supply of building materials to Rome based on intuition alone.

Cladistic methods as a tool for terrane analysis: a New Zealand example

ABSTRACTA cladistic analysis of New Zealand's basement terranes was conducted using 44 present/absent characters that were derived from the literature for a broad range of geological characters, including zircon age profiles, clastic source, metamorphic grade and igneous petrology. The analysis resulted in a classification showing that both the Eastern and Western provinces are natural groupings. Two monophyletic clades (natural historical groupings) were identified within the Eastern Province: a Central Arc clade of South Island terranes (Maitai/Dun Mountain, Murihiku and Brook Street), and the younger greywacke terranes plus the North Island Murihiku Terrane. The Rakaia and Kaweka terranes of the older Torlesse are basal to (less derived than) the Central Arc and Eastern Province younger greywacke terranes. Although cladistic methodologies have been developed for biological systems, these results demonstrate a proof of principle for their application to terrane analysis.

Volatile concentrations in olivine-hosted melt inclusions from meimechite and melanephelinite lavas of the Siberian Traps Large Igneous Province: Evidence for flux-related high-Ti, high-Mg magmatism

The origin of high-Mg melts remains one of the most highly debated questions in igneous petrology. There are two contrasting points of view, namely, (1) melt initiation in a rising high-temperature plume, and (2) mantle melting due to fluxing by water. To address this question we determined H2O, CO2, F, Cl and S concentrations in olivine-hosted melt inclusions of high-Mg volcanic rocks of the Siberian Traps Large Igneous Province that bracket the main pulse of volcanism at about 252–250 Ma, and can be classified as melanephelinites and meimechites. Both rock types belong to the high-Ti rock series. Correcting measured H2O, CO2, F, Cl and S concentrations in homogenized primary meimechite melt inclusions to primary meimechite melt composition using experimental melt compositions resulted in corrected melt-inclusion, volatile compositions of ~3.88 wt% H2O, ~1477 ppm CO2, ~4214 ppm F, ~2.08 wt% Cl and ~2490 ppm S. These values are viewed as minimum estimates for the original volatile concentrations in the melt because of the high probability for degassing during melt crystallization and/or during experiment homogenization. Olivine-hosted homogenized melt inclusions from melanephelinites yielded lower corrected concentrations of ~1.06 wt% H2O, ~998 ppm CO2, ~3242 ppm F, ~607 ppm Cl and ~2131 ppm S. We also measured water concentrations in clinopyroxenes of melanephelinites by FTIR, obtaining values as high as 133 ppm H2O, which corresponds to 0.91 wt% in the melt, in general agreement with data obtained by SIMS on the olivine-hosted melt inclusions. Olivine grains from melanephelinites are characterized by evolved compositions (Fo 0.80–0.86). Extrapolation to a primitive melanephelinite melt by simple fractional crystallization suggests that it could also contain high H2O concentrations (up to ~ 3 wt%). Analyzed meimechite and melanephelinite whole-rock samples are characterized by trace-element patterns that are typical of mantle-derived melts and by Sr-Nd isotope ratios that exclude crustal contamination or derivation from ancient lithospheric mantle. Thus, high volatile concentrations can be attributed to sublithospheric mantle source regions. This supports the notion that high-Mg melts form by volatile fluxing of the asthenospheric mantle rather than by decompression melting under relatively dry conditions of a rising abnormally high-temperature mantle plume.

IG-Mapper: A new ArcGIS® toolbox for the geostatistics-based automated geochemical mapping of igneous rocks

This work introduces a user-friendly, fast and effective tool for the automated geochemical mapping of igneous rocks, to provide a geospatial representation of petrological parameters through the application of either deterministic or stochastic interpolation techniques. The geostatistical approach allows mapping to be extended to areas where igneous rocks are hidden under sedimentary cover, also introducing an estimate of the interpolation reliability. This new GIS-based automated procedure, which is mostly constructed with the ArcGIS® Model-Builder as a graphical code designer, can generate three main types of outputs: 1) interpolation maps of major and trace elements, isotopic compositions, and derived parameters, to provide valuable geospatial information regarding the genetic and structural relationships between magmatic bodies; 2) lithological maps, that are based on the geostatistical interpolation of major element data and mirror the main geochemical classification diagrams of plutonic rocks; and 3) interpolation checking maps, which provide an estimate of the geostatistical interpolability for one specific parameter at a time. This last output is expressed in the form of an empirical index (Stochastic Interpolation Index), which highlights the randomness level of a specific value distribution. This automated lithological mapping function is an entirely new tool based on five original python scripts, which makes it possible to interpolate on a georeferenced map the compositions deriving from the most used geochemical classification diagrams. This new tool package is presented here by using a portion of the Serre Batholith in central Calabria (southern Italy), to illustrate the potential of this method to open new research perspectives in igneous petrology.

Trace-element composition of minerals and rocks in the Belaya Zima carbonatite complex (Russia): Implications for the mechanisms of magma evolution and carbonatite formation

The nature of petrogenetic links between carbonatites and associated silicate rocks is a matter of discussion for several decades and still remains controversial among igneous petrologists. The Belaya Zima plutonic complex in southern Siberia is a typical intrusion, in which carbonatites are spatially and temporally associated with the ijolite series rocks and nepheline syenites. In this study we use whole-rock compositions and trace element characteristics of the major and accessory minerals for reconstructing the magmatic evolution of the complex and clarifying the origin of carbonatites. We conclude that the observed gradual increase of Zr, Nb and REE concentrations in the magma is consistent with the process of extensive fractional crystallization and gradual transition from silicate rocks to carbonatites, and inconsistent with the formation of carbonatites by liquid immiscibility. Magma differentiation by fractional crystallization continued during the carbonatite formation. The textural and analytical evidence indicates that the early calcitic carbonatites evolved to dolomitic and ankeritic carbonatites. In addition, maximum Nb and Zr concentrations occur in the calcitic carbonatite, whereas the REE content increases in the dolomitic and ankeritic facies.

The S content of silicate melts at sulfide saturation: New experiments and a model incorporating the effects of sulfide composition

The extent to which sulfur dissolves in silicate melts saturated in an immiscible sulfide phase is a fundamental question in igneous petrology and plays a primary role in the generation of magmatic ore deposits, volcanic degassing, and planetary differentiation. In igneous systems, sulfide melts can be described as FeS-NiS-CuS 0.5 solutions with Fe/(Fe+Ni+Cu) significantly less than 1. Despite the presence of Ni and Cu in the sulfide, however, most experimental studies to date have concentrated on the effects of silicate melt composition on sulfur solubility and have used essentially pure FeS as the sulfide liquid. We have carried out 49 new experiments at pressures of 1.5–24 GPa and temperatures of 1400 to 2160 °C to investigate the effects of sulfide composition on sulfur solubility as well as extending the pressure and temperature ranges of the available data on sulfide saturation. We find that in the compositional range of most igneous sulfide melts [Fe/(Fe+Ni+Cu) > 0.6] sulfur solubility decreases linearly with Fe content such that at Fe/(Fe+Ni+Cu) of 0.6 the sulfur content at saturation is 0.6 times the value at pure FeS saturation. At lower values of Fe/(Fe+Ni+Cu), however, deviations from this ideal solution relationship need to be taken into consideration. We have treated these non-idealities by assuming that FeS-NiS-CuS 0.5 liquids approximate ternary regular solutions. We have fitted our data, together with data from the literature (392 in total), to equations incorporating the effects of silicate melt composition, sulfide liquid composition, and pressure on the solubility of sulfur at sulfide saturation ([S] SCSS ). The temperature dependence of [S] SCSS was assumed either to be an unknown or was taken from 1 bar thermodynamic data. The most important best-fit silicate melt compositional term reflects the strongly positive dependence of [S] SCSS on the FeO content of the silicate melt. The best-fit value of this parameter is essentially independent of our assumptions about temperature dependence of [S] SCSS or the solution properties of the sulfide. All natural compositions considered here exhibit positive dependences of [S] SCSS on temperature and negative dependences on pressure, in accord with previous studies using smaller data sets.

Forensic igneous petrology: locating the source quarry for the “black granite" Titanic headstones in Halifax, Nova Scotia, Canada

In Halifax, Nova Scotia, 149 victims of the 1912 sinking of the Titanic lie beneath petrologically identical "black granite" headstones. Those headstones, supplied by the White Star Line, arrived in Halifax in late 1912, but no known historical document reveals their source. They consist of medium- to coarse-grained olivine-bearing gabbro, with cumulus phases consisting of randomly oriented euhedral plagioclase laths, corroded olivine, and titaniferous magnetite, and intercumulus material consisting of augite with reaction rims of hornblende, both of which are variably altered to actinolite and biotite. Three types of forensic evidence [quantitative – radiometric age of 422.1 ± 1.3 Ma (n = 17), mean olivine FeO/(FeO + MgO) values ranging from 0.43 to 0.46, augite rim trace- element compositions (35 elements), and whole-rock chemical compositions (48 elements), including statistical analysis of all these data showing no significant differences between the headstones and their putative source quarry; qualitative – mineral assemblages, modal proportions, textural parameters, style and degree of alteration; and circumstantial – regional reputation, quarrying history, local logistics, regional transportation, McGrattan marker] connect the Titanic headstones to the Saint George Batholith in southwestern New Brunswick. Precise matching of any dimension stone to its source quarry is problematic, because that material connects only to a void in the quarry. Ideally, all physical-chemical-temporal properties of the dimension stone and source quarry should match, both quantitatively and qualitatively, but in reality only the ages must almost certainly match. Thus it is remotely possible for the right quarry to mismatch most of the properties of the dimension stone, and for a wrong quarry to match most of the properties of the dimension stone. However, in the case of the Titanic headstones, the cumulative weight of all the quantitative, qualitative, and circumstantial evidence, combined with a process of elimination and application of Ockham’s razor, indicate that the Charles Hanson quarry near Bocabec, southwestern New Brunswick, is the likely source for the gabbroic Titanic headstones in Halifax, Nova Scotia.

P.4.016 - Drunk bugs: chronic vapour alcohol exposure induces marked changes in the gut microbiome in mice

The study of volcanic and igneous plumbing system is a scientific discipline that builds on multi-disciplinary research on magma movement, evolution, and storage from the fields of volcanology, igneous petrology and geochemistry, geophysics and volcano geodesy. As outlined in the chapters of this book, research has revealed a complex picture of the processes that occur within the plumbing system. However, much work remains to be done, and this chapter discusses a number of challenges in future volcanic and igneous plumbing systems research based on recurring questions in the previous chapters. These challenges or directions include the link between nature and models, the time scales of magma transport, storage and eruption, the interplay between the rheology of magma and its host rock, as well as the relationship between magma plumbing and stress fields at different scales.

Forensic Igneous Petrology: Locating the Source Quarry For the “Black Granite” Titanic Headstones In Halifax, Nova Scotia, Canada

Abstract In Halifax, Nova Scotia, 149 victims of the 1912 sinking of the Titanic lie beneath petrologically identical “black granite” headstones. These headstones, supplied by the White Star Line, arrived in Halifax in late 1912, but no known historical document reveals their source. They consist of medium- to coarse-grained olivine-bearing gabbro, with cumulus phases consisting of randomly oriented euhedral plagioclase laths, corroded olivine, and Ti-rich magnetite, and intercumulus material consisting of augite with reaction rims of hornblende, both of which are variably altered to actinolite and biotite. Three types of forensic evidence [ quantitative – radiometric age of 422.1 ± 1.3 Ma ( n = 17), mean olivine FeO/(FeO + MgO) values ranging from 0.43 to 0.46, augite rim trace-element compositions (35 elements), and whole-rock chemical compositions (48 elements), including statistical analysis of all these data showing no significant differences between the headstones and their putative source quarry; qualitative – mineral assemblages, modal proportions, textural parameters, style and degree of alteration; and circumstantial – regional reputation, quarrying history, local logistics, regional transportation, McGrattan marker] connect the Titanic headstones to the Saint George Batholith in SW New Brunswick. Precise matching of any dimension stone to its source quarry is problematic, because that material connects only to a void in the quarry. Ideally, all physical-chemical-temporal properties of the dimension stone and source quarry should match, both quantitatively and qualitatively, but in reality only the ages must almost certainly match. Thus it is remotely possible for the right quarry to mismatch most of the properties of the dimension stone, and for a wrong quarry to match most of the properties of the dimension stone. However, in the case of the Titanic headstones, the cumulative weight of all the quantitative, qualitative, and circumstantial evidence, combined with a process of elimination and application of Ockham9s razor, indicate that the Charles Hanson quarry near Bocabec, SW New Brunswick, is the likely source for the gabbroic Titanic headstones in Halifax, Nova Scotia.

Igpet software for modeling igneous processes: examples of application using the open educational version

We provide here an open version of Igpet software, called t-Igpet to emphasize its application for teaching and research in forward modeling of igneous geochemistry. There are three programs, a norm utility, a petrologic mixing program using least squares and Igpet, a graphics program that includes many forms of numerical modeling. Igpet is a multifaceted tool that provides the following basic capabilities: igneous rock identification using the IUGS (International Union of Geological Sciences) classification and several supplementary diagrams; tectonic discrimination diagrams; pseudo-quaternary projections; least squares fitting of lines, polynomials and hyperbolae; magma mixing using two endmembers, histograms, x-y plots, ternary plots and spider-diagrams. The advanced capabilities of Igpet are multi-element mixing and magma evolution modeling. Mixing models are particularly useful for understanding the isotopic variations in rock suites that evolved by mixing different sources. The important melting models include, batch melting, fractional melting and aggregated fractional melting. Crystallization models include equilibrium and fractional crystallization and AFC (assimilation and fractional crystallization). Theses, reports and proposals concerning igneous petrology are improved by numerical modeling. For reviewed publications some elements of modeling are practically a requirement. Our intention in providing this software is to facilitate improved communication and lower entry barriers to research, especially for students.

Granitoid magmas preserved as melt inclusions in high-grade metamorphic rock

This review presents a compositional database of primary anatectic granitoid magmas, entirely based on melt inclusions (MI) in high-grade metamorphic rocks. Although MI are well known to igneous petrologists and have been extensively studied in intrusive and extrusive rocks, MI in crustal rocks that have undergone anatexis (migmatites and granulites) are a novel subject of research. They are generally trapped along the heating path by peritectic phases produced by incongruent melting reactions. Primary MI in high-grade metamorphic rocks are small, commonly 5–10 μm in diameter, and their most common mineral host is peritectic garnet. In most cases inclusions have crystallized into a cryptocrystalline aggregate and contain a granitoid phase assemblage (nanogranitoid inclusions) with quartz, K-feldspar, plagioclase, and one or two mica depending on the particular circumstances. After their experimental remelting under high-confining pressure, nanogranitoid MI can be analyzed combining several techniques (EMP, LA-ICP-MS, NanoSIMS, Raman). The trapped melt is granitic and metaluminous to peraluminous, and sometimes granodioritic, tonalitic, and trondhjemitic in composition, in agreement with the different ![Formula][1] conditions of melting and protolith composition, and overlap the composition of experimental glasses produced at similar conditions. Being trapped along the up-temperature trajectory—as opposed to classic MI in igneous rocks formed during down-temperature magma crystallization—fundamental information provided by nanogranitoid MI is the pristine composition of the natural primary anatectic melt for the specific rock under investigation. So far ~600 nanogranitoid MI, coming from several occurrences from different geologic and geodynamic settings and ages, have been characterized. Although the compiled MI database should be expanded to other potential sources of crustal magmas, MI data collected so far can be already used as natural “starting-point” compositions to track the processes involved in formation and evolution of granitoid magmas. [1]: /embed/mml-math-1.gif

The Geochemical Complexity of Kimberlite Rocks and their Olivine Populations: a Reply to the Comment on Cordieret al.(2015) by Andrea Giuliani & Stephen F. Foley

We thank sincerely Giuliani & Foley for their discussion of the textures and compositions of olivine in kimberlites. We do not agree with many of their interpretations and therefore welcome the chance to respond, particularly because it provides an opportunity to explain once again the characteristics of olivine in kimberlites that we think are most important—features that have commonly been misinterpreted or overlooked in many other papers. In publications such as those by Kamenetsky et al. (2008), Brett et al. (2009) or Pilbeam et al. (2013), the emphasis has been on mineral compositions and internal zonation whereas in our paper (Cordier et al., 2015) and in an earlier study (Arndt et al., 2010), we emphasized the internal structures and fabrics of olivine grains. In the earlier paper, we described structures produced by solid-state deformation and showed that these could only have formed in the lithosphere. In our 2015 paper, we focused on grain boundary migration zones. These features, which typically develop during fluid-assisted recrystallization, may be unfamiliar to igneous petrologists but are well known to metamorphic and structural geologists. Like the internal deformation features, they form slowly or under high-stress conditions and could only have been produced within the lithosphere. We emphasize that these deformation or recrystallization features formed within rock of dunitic composition: the orthopyroxene, clinopyroxene and garnet–spinel that make up a large proportion of most mantle xenoliths were absent when these textures originated. In our opinion, these observations indicate clearly that orthopyroxene was eliminated before entrainment of xenoliths into the ascending kimberlite magma. If this interpretation is correct (and we have not heard or read any arguments to negate it), it calls into question the commonly accepted model that proposes loss of orthopyroxene within ascending kimberlite magma.

In Memoriam Udo Schwertmann (25 November 1927-20 January 2016)

It is with infinite sadness that I write these lines. I first met Udo Schwertmann in the spring of 1975. His department was seeking a scientist with experience in X-ray methods (XRD and XRF) and I was looking for a job. To me, a young upstart with a PhD and experience in igneous petrology and geochemistry, soils were something like ‘yukk.’ In the end, Schwertmann taught me to respect soils and practically all that I know about soils and clays. First, the sheer size of this 2 m-tall, wiry man was impressive. Then there was the reserved dignity of the North-German Hanseatic gentleman: style without a trace of aloofness. So much for …

Igneous petrology on the bases of rock forming minerals in the Hakone volcano.

Igneous petrology on the bases of rock forming minerals in the Hakone volcano.