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[Display omitted] • Water-rich magma fractionation contributes to the formation of high Sr/Y rocks. • Quantifying crustal thickness by Sr/Y ratios should consider water-rich magma fractionation. • A Late Devonian-early Carboniferous continental arc setting developed in central Beishan. The petrogenesis of intermediate-silicic rocks with high Sr/Y ratios that are closely associated with porphyry Cu-Au mineralization and TTGs remains uncertain. This study presents new geochronological and geochemical data for high Sr/Y granodiorites and associated mafic microgranular enclaves (MMEs) from the Late Devonian–early Carboniferous Suanjingzi batholith in the Beishan orogen, NW China. The MMEs, dioritic and fine-grained, share mineral assemblages with their hosts but contain more amphibole. Similarities in ages and Sr-Nd-O isotopes between the MMEs and their hosts indicate that they share a common magma source. Our geochemical studies and quantitative modeling imply that upper crustal fractional crystallization of water-rich magma, represented by the associated MMEs, played a crucial role in forming the Late Devonian–early Carboniferous high Sr/Y rocks in central Beishan. High H 2 O contents promote amphibole crystallization and delay plagioclase appearance, giving rise to higher Sr and lower Y contents in evolved magma. Additionally, titanite fractionation can contribute to high Sr/Y ratios by decreasing Y contents. The MMEs, the best available proxy for the parental magma, originated from the partial melting of a mantle wedge metasomatized by subduction fluids. This study emphasizes the significance of upper crustal fractional crystallization of water-rich magma in forming high Sr/Y rocks. The possible increment caused by amphibole-dominated fractionation within the upper crustal level should be considered when employing Sr/Y ratios to quantify crustal thickness. Moreover, we argue that Late Devonian–early Carboniferous magmatism in central Beishan occurred in a continental arc setting, providing a stronger basis for understanding the Paleozoic tectonic evolution of the Beishan orogen. [ABSTRACT FROM AUTHOR]

Understanding how halogens are distributed among usual hydrous silicates in the lithosphere is important to constrain their deep geochemical cycle and fluid-rock interactions in subduction zones. This article presents first-principles modelling of halogen (F.sup.-, Cl.sup.-, Br.sup.-) incorporation in hydrous silicates including mica, chlorite, serpentine, amphibole, epidote and carpholite. The approach allows studying the impact of crystal chemistry on halogen partitioning by quantification of the energetic cost of halogen incorporation in minerals. Calculations are carried out in large systems where halogens are in minor to trace concentrations. Estimations show that F-bearing defects must be separated at least 9 Å from one another to reproduce trace element behaviour, this value increasing to at least 10 Å for Cl and Br. Results highlight the competition between the effects of electrostatic interactions and steric hindrance for incorporation of halogens, where steric hindrance has greater importance for heavy halogens, in particular for Br. Interaction with alkalis is a major control for F incorporation, especially in mica. Other parameters such as octahedral site occupancy, Si/Al ratio of tetrahedral sites and the nature of alkalis in amphibole and mica (K or Na) appear to play subordinate roles. Partition coefficients have been estimated in mineral assemblages in an effort to be representative of subduction zone metamorphism. Results show that pargasite, biotite and lizardite are favoured hosts for all three halogens, followed by clinochlore, tremolite and carpholite. The energetic cost of incorporating halogens into dioctahedral phyllosilicates and epidote is comparatively higher, and partitioning is predicted as unfavourable to these minerals. Fractionation between halogens in subduction zones is predicted by the evolution of mineral assemblages and partition coefficients, a consequence of the influence of crystal chemistry over halogen incorporation in hydrous silicates., Author(s): Sarah Figowy [sup.1], Benoît Dubacq [sup.1], Philippe D'Arco [sup.1] Author Affiliations: (1) grid.483106.8, 0000 0004 0366 7783, Sorbonne Université, CNRS-INSU, Institut Des Sciences de La Terre de Paris, ISTeP [...]

Background: pleural mesothelioma is a rare cancer in the general population, but it is more common in subjects occupationally exposed to asbestos. Studies with asbestos fiber quantification in pleural tissue are scarce: for this reason, we aimed at undertaking a scoping review to summarize the evidence provided by studies in which asbestos fibers were determined by electron microscopy (SEM or TEM) in human pleural tissues, whether normal or pathologic. Materials and methods: A scoping review of articles that quantified asbestos fibers in human pleural tissue (normal or pathologic) by electron microscopy (SEM or TEM), in subjects with asbestos exposure (if any) was performed. Results: The 12 studies selected comprised 137 cases, out of which 142 samples were analyzed. Asbestos fibers were detected in 111 samples (78%) and were below the detectable limit in 31 samples (22%). The concentration of asbestos fibers detected in the positive samples was distributed from as low as 0.01 mfgdt (millions of fibers per gram of dry tissue) up to 240 mfgdt. However, the minimum concentration of fibers overlaps in the three types of tissues (normal pleura, pleural plaque, mesothelioma) in terms of magnitude; therefore, it is not possible to distinguish a definite pattern which differentiates one tissue from the other. Conclusions: The studies included were heterogeneous as to the representativeness of the samples and analytical techniques; the possibility of false negatives must be considered. It would be desirable to systematically search for asbestos fibers to fill the knowledge gap about the presence of asbestos fibers in normal or pathological pleural tissue in order to better understand the development of the different pleural diseases induced by this mineral.

Exposures of arc crustal sections represent rare opportunities to directly evaluate lower crustal magmatic processes and their link to arc products in the middle and upper crust. Within the southernmost Sierra Nevada batholith, the Bear Valley Intrusive Suite (BVIS) exposes a contemporaneously constructed ~ 30 km thick intrusive suite, and thus is ideal for this type of examination. Here we present detailed petrography and mineral major and trace element data for the BVIS. The deepest exposed portion of the BVIS (8-9 kbars) is composed of heterogeneous mafic igneous intrusions of olivine metagabbro, olivine-hornblende orthopyroxenite, olivine-bearing hornblende norite, hornblende norite, hornblende gabbronorite, hornblendite and hornblende gabbro. Shallower crustal intrusions (3-7 kbars) are comparatively homogeneous and dominated by hypersthene-bearing and hypersthene-free tonalites. Using amphibole-plagioclase geothermometry, we show that the mafic lower crustal intrusions crystallized over a wide temperature range from 850 to 1070 °C, highlighting mafic igneous fractionation during isobaric cooling in the lower crust of the Sierran arc, while tonalitic liquids were emplaced at temperatures < 800 °C in the middle and upper crust. Calculated trace element melt compositions in equilibrium with amphibole in lower crustal gabbros are similar to measured tonalite bulk compositions and support the generation of tonalites through fractionation of the observed gabbros. Further, petrography and mineral chemistry suggest multiple distinct crystallization sequences recorded in the different types of gabbro, requiring the presence of coexisting parental melts with contrasting compositions and H.sub.2O contents. Using available experimental data, we develop a model by which mixing of variably fractionated dry and wet magmas with similar viscosities followed by crystallization-differentiation in the deep crust to explain the formation of uniform tonalitic melts at shallower crustal levels in the BVIS. This process also explains the unusual predominance of orthopyroxene in the BVIS, and the limited aluminum enrichment compared to experimental differentiation sequences of hydrous basalts. Considering the similar geochemical characteristics of intermediate and felsic igneous rocks from the Sierra Nevada batholith and the Cascades, mixing magmas of variable H.sub.2O contents in the lower crust represents a viable petrological process to produce SiO.sub.2-rich liquids that may be more common than previously recognized., Author(s): Hervé Rezeau [sup.1], Benjamin Z. Klein [sup.1] [sup.2], Oliver Jagoutz [sup.1] Author Affiliations: (1) grid.116068.8, 0000 0001 2341 2786, Department of Earth, Planetary and Atmospheric Sciences, Massachusetts Institute of [...]

The ophiolites of the northern slope of the Kuznetsk-Alatau Ridge are the most representative fragments of the sub-oceanic crust in the region. In this article, we present the results of a study of the metabasites from ophiolite paragenesis of the Severnaya, Zelenaya, Barkhatnaya mountains and Semenovsky massif. The selected samples from the gabbroid and subvolcanic complexes were studied in microsections, and the compositions of the main rock-forming minerals (plagioclases, amphiboles) were investigated in detail on an electron microscope equipped with micro-dispersion analyzer. It was established that feldspars are represented by a wide spectrum of composition: from albite to bitovnite; not less common amphiboles are also characterized by a wide diapason: edenite, ferro-edenit, ferropargasit, magneziogastingsit, magnesian, ferrous and actinolite hornblendes. Chlorite, which observed in all samples, represents ripidolit and piknochlorite. Accessories are apatite, ilmenite, sphene and, in rare cases, rutile. The data obtained by the phase relationship, and changing chemical composition of essential minerals (feldspars, amphiboles) allow suppose several steps of the transforming investigated metamorphic rock because signs of both progressive and retrograde metamorphism are found. The behavior of accessory minerals also expresses the variability of the thermodynamic parameters of metamorphism. This is confirmed by the traditional geothermobarometry methods (using the plagioclase-amphibole mineral pair). Observed retrograde metamorphic processes reflect the movement of ophiolite mass in the upper layers of the crust, and this makes it possible to connect metamorphism with obduction of ophiolites. For most of the investigated regions the early stage of ophiolite obduction in terms of location the “Riphean” oceanic island arc can be associated with episode of epidote-amphibolite facies of regional metamorphism at (T = 500-700°C and P = 2-6 kbar). The collision of Kuznetsk-Altai island arc to the structures of the Central Asia and Siberian Craton superterrane in Late Cambrian-Ordovician was controlled by vertical movement along submeridional tectonic discontinuities and resulted the metamorphism at low temperatures (350-510°C) and high pressure (6-9 kbar). The completion of these processes is characterized by a decrease in pressure (2-6 kbar) at the same temperatures. The result of these events is the formation of serpentinite melange on the Semenovsky massif.

New for Bulgaria, orbicular rocks among monzodiorite from the NW part of the Plana pluton are presented. They comprise a central core of mafic segregation with gabbro composition (mainly of amphibole and plagioclase), surrounded by pyroxene and plagioclase-rich "shells" or rims, with the outer rim in sharp contact with the monzodiorite matrix. [ABSTRACT FROM AUTHOR]

Alternating layers of pelitic and basic bands with occasional semi-pelitic band, millimeter to centimeter in width, occur between the epidote-amphibolite (metagabbro) and the pelitic schist in the epidote-amphibolite facies region of the Sanbagawa metamorphic belt, central Shikoku. The whole-rock major, trace, and rare earth element compositions of the semi-pelitic band are intermediate between those of the basic and pelitic bands. The peak metamorphic conditions were estimated at 1.0-1.2 GPa/600-630 °C for the mineral assemblage of the pelitic and semi-pelitic bands. The evolution of the CO.sub.2-rich fluid [X(CO.sub.2) = CO.sub.2/(CO.sub.2 + H.sub.2O)] at the lithologic boundary between the epidote-amphibolite and the pelitic schist, during the Sanbagawa prograde metamorphism, is discussed in the context of a titanite, rutile, calcite, dolomite, and quartz assemblage. The X(CO.sub.2) of the semi-pelitic band and basic and the pelitic bands increased during prograde metamorphism from the stability field of titanite to those of rutile + dolomite + amphibole + quartz and rutile + calcite + amphibole + quartz, respectively. The X(CO.sub.2) values of the metamorphic fluid at the peak metamorphic stage estimated by the matrix assemblages were higher in the order of the pelitic schist and epidote-amphibolite (less than 0.12-0.23), basic and pelitic bands (0.23-0.38), and semi-pelitic band (0.38-0.57), suggesting variations in the fluid compositions on a millimeter to centimeter scale. The CO.sub.2-rich fluid in the alternating layers, especially in the semi-pelitic band, was probably generated by a redox reaction between Fe.sup.3+-bearing silicate phases, such as amphibole and epidote in the basic band and carbonaceous material in the pelitic band. This reaction is thought to have been triggered by the chemical and/or mechanical mixing of these two bands during prograde metamorphism, resulting in the formation of the semi-pelitic band., Author(s): Masaki Enami [sup.1], Yuki Wakasugi [sup.1], Motohiro Tsuboi [sup.2] Author Affiliations: (1) grid.27476.30, 0000 0001 0943 978X, Institute for Space-Earth Environmental Research, Nagoya University, , Chikusa-ku, 464-8601, Nagoya, Japan [...]

Like the Moldanubian parts of the Bohemian Massif and the French Massif Central, the Vosges Mts (NE France) comprise an uppermost tectonic unit that consists of retrograded (U)HP/UHT granulites, eclogites and garnet peridotites, originally metamorphosed at pressures of [greater than or equal to] 4 GPa and temperatures of [greater than or equal to] 950 °C. Two amphibole-garnet-spinel-bearing peridotite bodies located near to Col des Bagenelles (CB) and Crébimont (CR) show a pronounced retrograde evolution. Primary garnet was completely transformed to a symplectite of orthopyroxene + clinopyroxene + Cr-poor spinel ± amphibole, partially surrounded by a discontinuous outer zone of coarser grains of pyroxenes ± amphibole. Such symplectites are typical for the sliding reaction garnet + olivine ± Na.sub.2O ± K.sub.2O ± H.sub.2O = orthopyroxene + clinopyroxene + spinel ± amphibole. Both peridotites contain 'primary' Cr-Al-spinel. In the sample from CB, such grains occur only within the symplectites after garnet, but never in the matrix, while in the sample from CR, Cr-Al-spinel is present as inclusions within the symplectites and as isolated grains within the surrounding matrix. In the peridotite from CR, that is more depleted than that from CB, these Cr-Al-spinel grains show intense chemical zoning with Cr and Fe.sup.2+ decreasing, but Al and Mg increasing from core to rim. This pattern is interpreted as retrograde zoning during decompression. Primary P-T conditions deduced from compositions of matrix pyroxenes under the assumption of equilibration with earlier garnet are [greater than or equal to] 1.6-1.7 GPa/ [greater than or equal to] 900 °C for sample CB, but [greater than or equal to] 2.3 GPa/ [greater than or equal to] 860 °C for sample CR. Temperature conditions during the breakdown of garnet are indicated by pyroxenes from the symplectites and are 833 ± 18 (CB) and 812 ± 11 °C (CR) using the Ca-in-Opx thermometer at a chosen pressure of 1.3 GPa., Author(s): Rainer Altherr [sup.1] Author Affiliations: (1) grid.7700.0, 0000 0001 2190 4373, Institute of Earth Sciences, Heidelberg University, , Im Neuenheimer Feld 234-236, 69120, Heidelberg, Germany Introduction Like many other [...]

Equilibrium isotope fractionation factors are the basis for application of stable isotopes in geological studies. Experimental calibration and theoretical calculations have been employed to determine Fe isotope fractionation factors for a variety of minerals, however, these methods have their limitations. An alternative approach to calibrating inter-mineral Fe isotope fractionation factors is to use well-characterized geological samples; this approach has unique advantages over the other methods including attainment of equilibrium at relatively low temperatures. In this study, we investigated the Fe isotope composition of magnetite (Mt), garnet (Grt), amphibole (Amp) and biotite (Bt) from the metamorphosed Yingshan iron formation in South China. Two independent geothermometers, quartz–magnetite oxygen isotope and amphibole–garnet–biotite Fe–Mg exchange geothermometers, give a consistent metamorphic temperature of 538 ± 39 °C. The Fe isotope composition of the different Fe-bearing minerals is highly variable in different ironstone samples, with δ56Fe values (relative to IRMM-014) ranging from −0.23 to +0.37‰ in magnetite, −0.44 to +0.09‰ in amphibole, −0.78 to +0.02‰ in garnet, and −0.61 to +0.04‰ in biotite. Despite that, the offsets of δ56Fe values for mineral pairs are consistent, implying attainment of equilibrium isotope fraction between these minerals. Inter-mineral Fe isotopic fractionations (±2 standard deviation) measured from the multiple mineral pairs are Δ56Fe Mt–Grt = +0.55 ± 0.08‰, Δ56Fe Mt–Amp = +0.25 ± 0.06‰, Δ56Fe Mt–Bt = +0.42 ± 0.11‰, Δ56Fe Amp–Grt = +0.34 ± 0.15‰, Δ56Fe Amp–Bt = +0.26 ± 0.04‰, and Δ56Fe Bt–Grt = +0.13 ± 0.08‰. Based on the well-defined metamorphic temperature (538 ± 39 °C) and internally consistent inter-mineral fractionation factors, the temperature-dependent functions for equilibrium Fe isotope fractionation between the following mineral pairs are derived: 103lnα Mt–Grt = 0.36(±0.05) × 106/T2, 103lnα Mt–Bt = 0.28(±0.07) × 106/T2, 103lnα Mt–Amp = 0.16(±0.04) × 106/T2, 103lnα Amp–Grt = 0.22(±0.10) × 106/T2, 103lnα Amp–Bt = 0.17(±0.03) × 106/T2, and 103lnα Bt–Grt = 0.09(±0.05) × 106/T2, where Fe3+/ΣFe ratio is 0.05 ± 0.02 in garnet, 0.29 ± 0.04 in biotite, and 0.24 ± 0.06 in amphibole for the above functions. The equilibrium Fe isotope fractionation factors derived in this study enable estimation of the metamorphic temperature of rocks that contain these mineral pairs, and identification of secondary processes that may have induced disequilibrium Fe isotope distribution in rocks, such as retrograde metamorphism and hydrothermal alteration. [ABSTRACT FROM AUTHOR]

The spatial/temporal proximity of Mt. Etna to the Hyblean Plateau and the Aeolian slab makes the discussion on the nature of its mantle source/s extremely controversial. In this study, a detailed geochemical overview of the entire Mt. Etna evolutionary sequence and a comparison with the magmatism of the Hyblean Plateau was proposed to: (i) simulate the composition of Mt. Etna tholeiitic to alkaline primitive magmas in equilibrium with a fertile mantle source; (ii) model the nature, composition and evolution of the mantle source from the tholeiitic stage (600 ka) to present magmatism. According to our simulations, two amphibole + phlogopite-bearing spinel lherzolite sources are able to explain the wide range of Etnean primary magmas. The enrichment in LILE, 87Sr/86Sr, Rb and H2O of the magmas emitted after 1971 (but also discontinuously generated in both historic and prehistoric times) are caused by different melting proportions of amphibole and phlogopite in a modally and compositionally homogeneous mantle domain, with melting degrees analogous to those required to produce magmas erupted prior to 1971. The behaviour of the hydrous phases during melting could be ascribed to a variable H2O/CO2 activity in the mantle source, in turn related to the heat/fluxes supply from the asthenospheric upwelling beneath Mt. Etna. All these considerations, strengthened by numerical models, are then merged to review the complex Pliocene/Lower Pleistocene to present day's geodynamic evolution of eastern Sicily. [ABSTRACT FROM AUTHOR]

The origin of the felsic volcanic rocks in the Okinawa Trough (OT) remains uncertain. In the middle Okinawa Trough (MOT), two types of rhyolites (type 1 and type 2 rhyolites) have been recognized. Research on the diverse volcanic rocks should be prioritized to determine the magmatic origins of these rocks. Consequently, in this article, the geochemical differences and controlling factors for these two types of MOT rhyolites are systematically discussed. Type 2 rhyolites have higher Dy/Yb and Nb/Ta ratios than type 1 rhyolites, implying that the former might be influenced by a greater contribution of amphibole. Quantitative models suggest that type 1 rhyolites could have formed via the remelting of andesites when amphiboles remain in the source, whereas type 2 rhyolites could have formed without residual amphiboles. These two distinct melting models effectively explain most discrepancies between the major and trace element compositions of type 1 and 2 rhyolites. Additionally, the lower Mg# and δEu values of type 2 rhyolites are partly caused by significant magmatic differentiation. Quasi-linear correlations between some major oxides, trace element ratios and Sr-Nd isotopic ratios for type 2 rhyolites suggest that these rhyolites might have been contaminated by crustal rocks or melts with compositions similar to those of the Kueishantao (KST) andesites or the Middle Miocene upper crustal rocks of SW Japan. Therefore, isotopically enriched crustal materials likely remain in the OT crust. [ABSTRACT FROM AUTHOR]

Amphibole fractionation during the early evolution of arc magmas has been widely inferred on the basis of distinctive geochemical fingerprints of the evolved melts, although amphibole is rarely found as a major mineral phase in arc volcanic rocks, so-called cryptic amphibole fractionation. Here, we present a detailed case study of xenoliths of amphibole-rich cumulate from the Zhazhalong intrusive suite, Gangdese arc, which enables an investigation of this differentiation process using a combination of petrological observations and in situ geochemical constraints. Evidence that the xenoliths represent fragments of igneous cumulates includes: (1) the presence of an amphibole-dominated crystal framework; (2) mineral and whole-rock Fe–Mg exchange coefficients; (3) rare-earth element patterns that are similar in the amphiboles and the xenoliths; (4) the compositions of basaltic to andesitic liquids in equilibrium with amphiboles; and (5) enrichment of the xenoliths in compatible elements and depletion in incompatible elements. The amount of trapped liquid based on La, Ce, and Dy abundances varies from ~12 to ~20%. Actinolitic cores within amphibole grains likely represent reaction between olivine precursor and hydrous melt, as evidenced by their high Cr and Ni contents. Amphibole thermometry and oxybarometry calculations indicate that crystal accumulation occurred over temperatures of 857–1014 °C, at mid-crustal pressures of 312 to 692 MPa and oxygen fugacity between 0.4 and 1.9 log units above the nickel–nickel oxide buffer. Quantification of the major-element compositions of the parent liquids indicates that the Zhazhalong amphibole cumulates crystallized from basaltic to andesitic magmas, probably with a shoshonitic affinity, and with SiO2 contents of 46.4–66.4 wt%. Appropriate partition coefficients, calculated using a parameterized lattice strain model and an empirical partitioning scheme, were employed to calculate the trace-element compositions of the liquids in equilibrium with amphibole. Our results confirm that Dy/Yb and Dy/Dy* ratios, which decrease with increasing degrees of differentiation, can be used as robust signatures of amphibole fractionation. This work presents a direct snapshot of the process of amphibole fractionation and provides a natural example of the hidden amphibole "sponge" in arc crust. In particular, this study also suggests that some appinites likely represent amphibole-rich cumulates, which may help to explain the genesis of other unusual but petrologically significant rocks. [ABSTRACT FROM AUTHOR]

A comprehensive petrological study and age dating of a young clinopyroxenite–gabbro–hornblendite series intruded deformed dunites, clinopyroxenites, and tilaites of the Kytlym mafic–ultramafic massif have been carried out. The convergent 40Ar–39Ar age of amphibole from clinopyroxenite and U–Pb isotope data of zircons from melanocratic gabbro correspond to 415 Ma and indicate that the termination of ultramafic magmatism in the Ural Platinum Belt took place in the Early Devonian. [ABSTRACT FROM AUTHOR]

Oceanic transform faults represent abundant yet relatively unexplored components of the hydrologic cycle in the mantle lithosphere. Current models limit fluid circulation to 600 °C, the thermal limit of earthquakes recorded by teleseismic surveys. However, recent ocean‐bottom seismic surveys have located earthquakes at depths corresponding to >1000 °C in modeled thermal structure. To constrain the depth extent of brittle deformation and fluid infiltration, we analyzed peridotite mylonites dredged from the Shaka Transform Fault, Southwest Indian Ridge. Samples range from high strain mylonites that preserve ductile microstructures to lower strain mylonites that are fractured and overprinted by hydrothermal alteration. Microstructural analysis of the high strain samples reveals brittle deformation of pyroxene concomitant with ductile deformation of olivine and growth of amphibole. Porphyroclasts preserve healed fractures filled with fluid inclusions, implying repeated episodes of fracture, fluid infiltration, and healing. The association of hydration features with brittle structures points to seawater, rather than melt, as the fluid source. Textural analysis indicates that strain localization was initiated by grain boundary pinning and that olivine grain size was reduced to ~1 μm in the presence of amphibole. Comparing the amphibole stability field to thermometry estimates for the limit of recrystallization suggests that fluid flow extended to ~650-850 °C. Our results indicate that the hydrologic cycle extends past the brittle‐ductile transition and promotes strain localization via hydrolytic weakening and hydration reactions. We propose that seawater infiltration on oceanic transform faults is driven by the seismic cycle and represents a first order control on the rheology of the oceanic lithosphere. [ABSTRACT FROM AUTHOR]

Tremolite schists in Ordovician meta-volcanic units in central New South Wales (NSW) consist of fine fibrous tremolite-actinolite. They host tremolite asbestos occurrences, and small quantities of asbestos were mined from narrow vein deposits in central NSW during the last century. When pulverized, the tremolite schist releases mineral fragments that fall into the classification range for countable mineral fibers and may be classed as asbestos despite not having an asbestiform habit. The ambiguity in classification of this type of natural material raises significant health and safety, legal, and environmental issues that require clarification. While the health effects of amphibole asbestos fibers are well known, the consequences of exposure to non-asbestiform, fibrous varieties is not well studied. This group of elongated mineral particles deserves more attention due to their widespread occurrence in metamorphic rocks in Australia. Toxicological studies are needed to assess the health risks associated with disturbance of these minerals during mining, civil construction, forestry, and farming practices. [ABSTRACT FROM AUTHOR]

The Calaveras Dam Replacement Project (CDRP) pioneered technical approaches for addressing community exposure to naturally occurring asbestos (NOA) via the inhalation pathway. Over the course of the CDRP, approaches were developed for key issues, including determining the NOA particles of interest, defining the toxicity limits to apply to various types of NOA particles, establishing dust control, and creating appropriate feedback loops for using laboratory data. Specific issues of interest included whether to count only structures above a certain length and the inhalation unit risk value to use for amphiboles. The knowledge gained on the CDRP can and is being used to optimize NOA evaluation and control at other, similar projects. [ABSTRACT FROM AUTHOR]

The Calaveras Dam Replacement Project, a major construction project completed in 2019, involved hundreds of workers using heavy earth-moving equipment and mining operations, including blasting, drilling, rock crushing, and other operations designed to move millions of cubic yards of earth. Much of the material was composed of serpentinite, blueschist, and other rocks that contain chrysotile and a variety of amphibole minerals, including glaucophane, winchite, actinolite, tremolite, and other asbestos-related amphiboles. This article explores the unique characteristics of the blueschist that required extensive protective measures to be undertaken by the contractor to protect workers and surrounding sensitive receptors. This article will provide an overall summary of the dimensional characteristics of the airborne blueschist elongate mineral particles encountered during construction activities to compare and contrast current understanding of cleavage fragments versus asbestiform mineral fibers. [ABSTRACT FROM AUTHOR]

Petrography of mélange matrix and clastic sedimentary rocks in coastal California reveals the occurrence of detrital serpentine and detrital asbestiform sodic amphibole (glaucophane). Many sandstones of the Franciscan Complex have small amounts of detrital serpentine, with amounts of up to several percent in some cases. Detrital amphibole, including asbestiform glaucophane, is also present in some sandstones. Whereas rare sandstones have so much detrital glaucophane that they appear blue in hand specimen (up to nearly half of the rock volume), most glaucophane-bearing sandstones lack blue color, and the detrital glaucophane is not apparent in hand specimen. Most of the occurrences of detrital glaucophane are in blueschist facies sandstones, some of which also contain neoblastic (grew in place) glaucophane, but a notable exception is a widespread prehnite-pumpellyite facies unit that crops out primarily in Sonoma and Marin Counties. The detrital mineralogy of sandstones mirrors the block and matrix compositions of Franciscan mélanges that can be thought of as scaled-up equivalents of these clastic sedimentary rocks (mega-conglomerates/sedimentary breccias). Franciscan mélanges range from having a detrital siliciclastic to a detrital serpentinite matrix, and interfingering and gradation of the two matrix types is common. These findings suggest that clastic sedimentary rocks associated with current or past active orogenic settings elsewhere in the world may contain naturally occurring asbestos (NOA) even if the NOA component minerals are not visible in hand specimen. [ABSTRACT FROM AUTHOR]

The c.a. 259–260 Ma Emeishan mantle plume caused extensive flood basalts and associated peralkaline rocks; petrogenesis of these peralkaline rocks can provide detailed information about the melting process in the mantle. In this paper, we present detailed petrology, chronology, major and trace element geochemistry, Sr-Nd isotope and in situ zircon Hf isotope for an amphibole syenite from Panxi area, inner zone of the Emeishan large Igneous province (ELIP). The amphibole syenite has a zircon U-Pb ages of 260 ± 2 Ma (MSWD = 1.2, n = 22), which is synchronous with Emeishan mantle plume. It displays moderate SiO2 (64.89–65.67 wt.%), high Na2O (7.35–7.71 wt.%) and K2O (4.78–4.96 wt.%) contents, with A/CNK values of 0.86 to 0.90, with high Rittman index of 6.6 to 7.1, showing peralkaline affinity. It displays significantly negative Sr anomalies (133 to 200 ppm) and slightly negative Eu anomalies (Eu/Eu* = 0.78–1.04). The rock displays high εNd(t) values of +2.4 to +2.5. Zircons from the amphibole syenite display positive εHf(t) values from +8.9 to +11.0, with single-stage Hf model ages ranging from 0.47 to 0.55 Ga, combined with the well-developed correlation of TFe2O3, CaO/Al2O3, TiO2, Ni and Cr with MgO, suggesting the amphibole syenite was derived from the mantle source, and the fractional crystallization played a significant role in the generation of the magma. The MELTS model results show that Houzishan amphibole syenite can be formed by the high degree (~80%) fractional crystallization of ~24% clinopyroxene, ~4% orthopyroxene, ~35% plagioclase and ~5% oxide from parental magma resembling high-Ti basalts. These results indicate that Houzishan amphibole syenite represents the juvenile mantle-derived peralkaline melts addition to the continental lower crust in the inner zone of the ELIP and assimilating with minor crust material. [ABSTRACT FROM AUTHOR]

This study presents a new petrological–geochemical data set for the Monte Capio and Alpe Cevia mafic–ultramafic sequences, which are exposed in the deepest levels of the Ivrea–Verbano Zone. These sequences are composed of a peridotite core, with dunite in the center, mantled by minor orthopyroxene-dominated pyroxenites and subordinate hornblende gabbronorites. Amphibole is ubiquitous in the peridotites and the pyroxenites (≤ 15 vol % and 10–40 vol %, respectively), and the peridotite–pyroxenite associations are frequently crosscut by amphibole-rich (45–90 vol %) veins/dykes showing sinuous-to-sharp planar boundaries towards host rocks. The whole-rock Mg# [100 × Mg/(Mg + Fetot2+)] decreases from the peridotites to the pyroxenites and the crosscutting amphibole-rich dykes (84–81, 80–77, and 73–66, respectively), consistently with the Mg# variations shown by included orthopyroxene, clinopyroxene, and amphibole. Olivine has relatively low forsterite and NiO amounts (84–78 mol % and ≤ 0.14 wt%), and spinel is characterized by low Cr# [100 × Cr/(Cr + Al)] of 7–24. The anorthite content of plagioclase varies from 91 to 88 mol% in plagioclase-bearing pyroxenites to 91–75 mol% in amphibole-rich dykes. The chondrite-normalized REE patterns of amphibole from peridotites and pyroxenites show nearly flat MREE–HREE, no evident Eu anomaly, and LREE that are slightly depleted to slightly enriched with respect to MREE. Amphibole from the amphibole-rich veins/dykes exhibits slight LREE depletion. Whole-rock and amphibole separates show substantial variations in initial Nd–Sr isotopic compositions (e.g., whole-rock εNd calculated at 290 Ma ranges from − 0.3 to − 4.7), irrespective of the rock-type and of incompatible element amphibole compositions. We propose that the Monte Capio–Alpe Cevia dunites formed by cooling of magma lenses that intruded the lowermost continental crust of the Ivrea–Verbano Zone. The chemically evolved signature of the dunites documents earlier crystallization of chemically primitive dunites at lower levels, or olivine fractionation within the dunites during melt ascent. Associated pyroxene-bearing peridotites show a magmatic evolution ruled by reaction of a melt-poor crystal mush with migrating melts relatively rich in SiO2 and H2O, which developed orthopyroxene and amphibole at the expenses of olivine ± clinopyroxene. These migrating melts may be reconciled with those feeding the crosscutting amphibole-rich veins/dykes, whose compositions suggest formation by chemically evolved H2O-rich basalts with an arc-type incompatible trace-element fingerprint. Unraveling the origin of the Monte Capio–Alpe Cevia pyroxenites is hampered by the complex open-system magmatic evolution, which also included assimilation of material released by basement metasediments and/or involvement of primary melt batches with different compositions. [ABSTRACT FROM AUTHOR]

The detailed mineralogical-geochemical study of eclogites and their retrograde products (amphibolites in a rim of eclogite boudin) from Vichennaya Luda Island (Keret Archipelago, White Sea) revealed systematic variations in major-, trace and rare-earth element composition of rock-forming minerals, which should be taken into account in geochronological and thermobarometric studies. Garnets from garnet–amphibole interlayers in the eclogites demonstrate a prograde zoning. In addition, garnet rims differ from their cores in a "hump-like" REE pattern owing to the elevated Sm, Eu, Gd and Dy contents and a negative slope of HREE pattern, as well as in an increase of Sm/Nd and a decrease of Lu/Hf ratio. It has been established that the eclogites contain clinopyroxene with depleted (to chondritic level) REE content, a positive Eu anomaly, and lowered Ti, V, Cr, Y, Zr, and Hf contents. Based on these geochemical features, the Cpx can be ascribed to relict that have preserved during peak eclogite metamorphism. Amphiboles in amphibolite rim of boudin differ sharply from amphiboles in eclogite in the lowered contents of LREE and some HREE. In addition to almost a two-fold decrease of Ti content in the eclogite–amphibolite sequence, amphiboles demonstrate a significant decrease of V, Sr, Y, Nb, and Hf contents. All biotites have sinusoidal REE pattern, which is typical of minerals formed through fluid-induced disequilibrium processes. Biotite from eclogites has higher Ti content and elevated contents of REE, Nb, V, Cr, Ba, and Hf as compared to biotites from the amphibolization rim. The eclogites and amphibolites developed after them are similar in major, trace, and rare-earth element composition. [ABSTRACT FROM AUTHOR]

The processes that result in arc magmas are critical to understanding element recycling in subduction zones, yet little is known about how these systems evolve with time. Nicaragua provides an opportunity to reconstruct the history of a volcanic arc since the Cretaceous. Here we present the stratigraphy of the Cretaceous–Eocene volcanic units in Nicaragua and their relationship to the different tectonic units where the arc developed. We discovered an evolution from an arc‐dominated by calc‐alkaline compositions in the Cretaceous–Eocene, to transitional compositions in the Oligocene–Miocene, to finally tholeiitic magmas common in the modern volcanic front. Our petrographic studies confirm that in the Cretaceous–Eocene the olivine + clinopyroxene cotectic was followed by clinopyroxene + plagioclase ± amphibole. Given the abundance of amphibole and the lack of this mineral in the modern volcanic front, the Cretaceous–Eocene Arc melts were likely more water‐rich than modern Nicaragua, suppressing the crystallization of plagioclase after olivine. We also found temporal changes in element ratios that are sensitive to variations in sediment input. The Cretaceous–Eocene Arc is characterized by a lower Ba/Th compared to the Oligocene–Miocene and modern volcanic front samples, suggesting that the sediment input was lower in Ba, possibly analogous to old deep siliceous sediment subducting in the western Pacific. Both U/Th and U/La are higher in the modern volcanics, reflecting higher U/Th in the subducting sediments following the 'Carbonate Crash'. Finally, we found that the orientation of the arc axis also changed, from northeast‐southwest in the Cretaceous–Eocene to northwest‐southeast after the Oligocene. This change probably records variations in the location of the subduction zone as this region shaped into its current geographic configuration. [ABSTRACT FROM AUTHOR]

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The thermoelastic behavior of a crystal of Fe-rich holmquistite with crystal-chemical formula A(K0.01Na0.01)B(Li1.88Mg0.10Na0.02)C(Mg1.68Fe1.422+ Mn0.022+ Al1.88)TSi8.00O22W[(OH)1.97F0.03] was studied by single-crystal X‑ray diffraction at temperatures up to 1023 K, where isothermal annealing in air for 160 h yielded the loss of 0.85 H apfu coupled with oxidation of M1Fe. A complex pattern of cation exchanges was deciphered by comparing structure refinements done before and after annealing. Li migration from the M4 to M3 site is responsible for nonlinearity of the c parameter around 600 K during the first annealing. Cooling of the partially deprotonated crystal to room temperature (RT) showed discontinuities in trends of the b and c parameters around 820–800 K, which cannot be ascribed to a phase transition and can be explained by a rearrangement of the structural units affecting the geometry of the M4 polyhedron. Such discontinuities have never been observed in amphiboles before and must be related to dimensional constraints deriving from the peculiar composition of this amphibole, which contains the smallest possible homovalent constituents, i.e., BLi, CAl, and TSi. The calculated thermoelastic parameters are: Fe-rich holmquistite: αa = 1.36(2)×10–5; αb = 0.55(1)×10–5; αc = 1.5(1)×10–5 – 6.7(9)×10–9; αV = 3.5(3)×10–5 – 0.8(3)×10–8 (polynomial); 2.58(6)×10–5 (linear); partially deprotonated Fe-rich holmquistite: αa = 1.324(9)×10–5 (RT-1023 K); αb = 0.60(1)×10–5 (RT-773 K); αc = 0.68(2)×10–5 (RT-773 K); αV = 2.59(2)×10–5 (RT-773 K). Fe-rich holmquistite is much stiffer than all the previously studied orthorhombic Pnma and Pnmn amphiboles. The results of this work allow progress toward a general model that may explain how the amphibole structure responds to non-ambient conditions, and allows the release of water in diverse geological environments. [ABSTRACT FROM AUTHOR]

Constraining crystallization pressure and thus intrusion depth of granites in various geodynamic settings remains challenging, yet important to further our understanding of magma system and crustal evolution. We propose that titanite, which is a common accessory in metaluminous and weakly peraluminous granites, can be used as a barometer if it crystallized in magmatic, near-solidus conditions and in equilibrium with amphibole, plagioclase, K-feldspar, quartz, biotite, and magnetite ± ilmenite. Titanite Al 2 O 3 increases with pressure (P) according to: P (in MPa) = 101.66 × Al 2 O 3 in titanite (in wt%) + 59.013 (R 2 = 0.83) with estimated uncertainties of ~±60 to ~±100 MPa for crystallization between ~150 and 400 MPa. We highlight that the current calibration dataset is limited, and that systematic experimental studies are needed to rigorously quantify the relation. The most important use of this empirical barometer will be for rocks in which amphibole is present but significantly altered, or in combination with amphibole barometry, as titanite can be easily dated by LA-ICP-MS. [ABSTRACT FROM AUTHOR]

The phase relations upon eclogitization of basalt and melting of H2O-bearing eclogite were studied experimentally for basalt–H2O in the range of P = 3.7–4.0 GPa and Т = 1000–1300°C. It is shown that the phase relations depend on temperature. The formation of a supercritical fluid/melt occurs at T = 1000°C and P = 3.7 GPa; the eclogite‒garnetite transition, at T = 1000–1100°C and P = 3.9 GPa; and partial melting of eclogite with the formation of a Na-alkaline silicate melt and clinopyroxenite restite, at 1150 and 1300°C. the supercritical fluid/melt has a high reactivity, which results in the formation of garnet megacrysts, enrichment of garnet in Ti, and replacement with clinopyroxene, the formation of ilmenite, K-bearing amphibole, and the transformation of eclogite into garnetite due to the mass crystallization of garnet. [ABSTRACT FROM AUTHOR]

Amphibole is a rock‐forming mineral widely existing on the earth. It is easily dissolved and altered during the later stage of diagenesis and mineralization, and often forms chloritization, which is an important indicator for prospecting. To explore amphibole's dissolution process and alteration mechanism, dissolution experiments were carried out under acidic conditions using pargasite‐rich amphibole as raw material, and the effects of temperature, pH, and experiment duration on amphibole alteration were investigated. Experimental samples and products were analyzed using X‐ray diffractometer, field emission scanning electron microscope, electron probe micro analyzer, and transmission electron microscopy. It was found that many pores and erosion edges are produced after amphibole dissolution, and there is a clear interface between the dissolved residual portion and the parent. The dissolved residual portion remains in the amphibole phase, but as the temperature and time increase, the intensity of the diffraction peak of the phase in the product decreases, and the peak position shifts to a small angle. Many clay minerals such as chlorite and griffithite formed on the amphibole surface. In an environment with strong acidity (pH=3), the amount of chamosite increases with temperature (180°C→210° C→240°C), whereas clinochlore is only increased in a 150–210°C environment. Griffithite growth was observed in the acidic (pH=6) and low temperature (<180°C) environments. Based on this analysis, large radius Cl– enters the amphibole lattice or cracks to promote dissolution. The Al‐poor and Ca‐ and Fe‐rich regions between the edge and core of the amphibole are caused by dynamic equilibrium in amphibole dissolution and alteration process, which is an essential indicator for the beginning of amphibole dissolution‐alteration. Diffusion and the coupled dissolution‐reprecipitation mechanism accomplishes the process of dissolution and alteration to form clay minerals. The energy of the system determined by temperature and pH is the key to controlling the rate of growth and nucleation of clay minerals. High temperature and strong acidity will dissolve more iron from amphibole, which is conducive to chlorite growth. Compared to chlorite, griffithite is more sensitive to temperature. Griffithite attaches on the amphibole surface with a star‐like in a weak acid and low‐temperature environment. The results of this study can provide a mineralogical basis for the analysis of hydrothermal alteration processes and the division of alteration zones. [ABSTRACT FROM AUTHOR]

To understand the relationships between eclogite‐facies mineral assemblages, deformation microstructures, and the seismic properties of subducting oceanic crust, eclogites from the Yuka terrane, North Qaidam ultrahigh‐pressure metamorphic belt, NW China, were studied. Observations of mineral textures, deformation microstructures, and petrofabrics in the eclogites indicate that garnet, omphacite, and phengite were deformed by intracrystalline deformation (i.e., dislocation creep) during prograde metamorphism. In contrast, amphibole, which was formed by the topotactic replacement of omphacite at fluid‐present conditions, is considered to have been deformed by diffusional flow (dissolution‐precipitation creep) during amphibolite‐facies retrogression associated with exhumation. Based on the petrofabrics in the samples, the seismic properties of the eclogites were calculated depending on eclogite‐facies mineral assemblages such as garnet + omphacite, garnet + omphacite + phengite, garnet + omphacite + phengite + lawsonite, garnet + omphacite + phengite + amphibole, and garnet + omphacite + amphibole. We found that the seismic signatures of each of the eclogite‐facies mineral assemblages were different. In particular, phengite‐bearing eclogites (the garnet + omphacite + phengite/garnet + omphacite + phengite + amphibole assemblages), depending on phengite content, produced the strongest seismic anisotropy (AVp and AVs), with a strong polarization anisotropy, that was at least three times higher than bimineralic (phengite‐absent) eclogites (garnet + omphacite assemblage). Our results indicate that phengite, as a stable phase at high‐pressure and high‐temperature conditions, can play an important role in the creation of trench‐parallel seismic anisotropy in the eclogite‐facies mineral assemblages found in subduction zones. Key Points: Seismic signatures are distinct for different eclogite‐facies mineral assemblagesPhengite‐bearing eclogite produces the strongest seismic anisotropy among different eclogite‐facies mineral assemblagesPhengite in eclogite‐facies mineral assemblages can play an important role in the creation of seismic anisotropy in subduction zones [ABSTRACT FROM AUTHOR]

Background: Lung cancer screening with low‐dose computed tomography (CT) scanning (LDCT) is accepted as a screening tool, but its application to populations exposed to recognized occupational or environmental carcinogens is limited. We apply LDCT to a population with a predominantly nonoccupational exposure to a recognized human lung carcinogen, Libby amphibole asbestos (LA). Methods: Patients in an asbestos disease clinic in Libby, Montana who were aged 50 to 84 years, greater than or equal to 20 pack‐year history of tobacco use (irrespective of quit date), and asbestos‐related pleuropulmonary disease on high‐resolution CT scan were offered free annual lung cancer screening over a 39‐month period. Results: Of 2897 clinic patients, 1149 (39.7%) met eligibility criteria, and 567 (49%) were screened with 1014 low‐dose CT scans. Most screened patients had principally environmental (333 or 59%) or household exposure (145 or 25%) to LA. Seventeen primary lung cancers were identified, mostly in early stages: 10 at stage 1, two at stage 2, three at stages 3 to 4, and two at limited small‐cell cancers. The screening yield was 1.9 at baseline scan and 1.5% on the first annual scan. Conclusions: Consistent with the guidelines of the National Comprehensive Cancer Network and American Association of Thoracic Surgery, LDCT for early lung cancer detection should be offered to people with significant exposure to occupational or environmental human lung carcinogens. [ABSTRACT FROM AUTHOR]

The crystal preferred orientation (CPO) of amphibole has a large effect on seismic anisotropy in the crust. Previous studies have reported four CPO types (I–IV) of amphibole, but the genesis of type IV CPO, which is characterized by [100] axes aligned in a girdle subnormal to the shear direction, is unknown. In this study, shear deformation experiments on amphibolite were conducted to find the genesis of type IV CPO at high pressure (0.5 GPa) and temperature (500–700 °C). The type IV CPO was found under high shear strain (γ > 3.0), and the sample exhibited grains in a range of sizes but generally smaller than the grain size of samples with lower shear strain. The seismic anisotropy of type IV CPO is lower than that of types I–III. The weak seismic anisotropy of highly deformed amphibole could explain weak seismic anisotropy observed in the middle crust. Plain Language Summary: Amphibolite is one of the major constituent rocks of the middle to lower crust and amphibole is a major constituent mineral of amphibolite. The crystal preferred orientation (CPO) of amphibole has a large effect on seismic anisotropy in the crust. In many previous studies on natural amphibolites, four amphibole CPO types (types I–IV) were observed. Types I, II, and III CPOs were found in previous deformation experiments at a pressure of 1 GPa, but the genesis of type IV CPO is unknown. In this study, shear deformation experiments on amphibolite were conducted at a high pressure (0.5 GPa) and temperature (500–700 °C) to find the origin of the type IV CPO. We found the type IV CPO of amphibole, for the first time, through deformation experiments under high shear strain (shear strain > 3.0), where the sample showed a wide range of grain size and/or small grain size. The type IV CPO of amphibole shows smaller seismic anisotropy than those of other amphibole CPO types. Our result show that even highly deformed amphibolites can exhibit weak seismic anisotropy. This weak seismic anisotropy of amphibole may be important to interpret the regional low seismic anisotropy in the middle crust. Key Points: We conducted shear deformation experiments on amphibolite at a pressure of 0.5 GPa and temperatures of 500‐700°CType IV CPO of amphibole developed under high shear strain, where the sample showed wide range of grain sizes and/or small grain sizeSeismic anisotropy of amphibole for type IV CPO is weaker than for other CPO types [ABSTRACT FROM AUTHOR]

Coronitic microstructures have been used to interpret the late-stage solidification history of igneous rocks and to constrain the corresponding chemical and/or physical changes. Coronas with three shells were also recognized in the Miaowan olivine norite, Yangtze Craton, South China. In our study, orthopyroxene intergrowth with vermicular magnetite in the inner shell is in optical continuity with magnetite-free orthopyroxene in the middle shell. In the outer shell of brown amphibole remaining magnetite-free orthopyroxene inclusions sporadically occur. Meanwhile Mg# values of orthopyroxene (76–80) in the inner and middle shells are basically consistent with olivine (78–81). In this paper, we propose a multi-stage genetic model for the formation of coronas in the Miaowan olivine norite. In the first stage, the magnetite-free orthopyroxene shell formed through reaction between primocrystal olivine with the residual Si-rich melt at 990–1 053 °C and 6.2–6.5 kbar. In the second stage, the orthopyroxene-magnetite symplectite shell formed when primocrystal olivine reacted with the late-stage residual Fe-rich melt promoted by high oxygen fugacity condition at 927–1 035 °C and 6.0–6.5 kbar. In the third stage, the brown amphibole shell formed as the presence of residual hydrous melt and replaced the middle shell at 821–900 °C and 5.5–6.0 kbar. [ABSTRACT FROM AUTHOR]

Camarioca Sur is a sector in Moa-Baracoa ophiolitic complex composed of pyroxene ultramaphites, gneissic amphiboles, chromium-spinels and amphibolitic granofels, in which the presence of compact and hard rock dykes has been documented, white to dark gray color and poor weathering crust development. The aim of this research is to characterize the associated leucocratic dykes and the ultramafic lithological association of Moa-Baracoa ophiolitic complex in Camarioca Sur sector by using petrological and geochemical techniques. It was found harzburgite dunites are the predominant rocks. Peridotites are mainly composed of olivine, with the presence of chromium-spinels and to lesser extent pyroxenes. The rocks are partial or totally transformed into minerals of serpentine group (antigorite, lizardite and chrysotile). Some peridotites are metamorphosed, developing talcum + tremolite + chlorite. The leucocratic rocks, which cut through the peridotite dikes, consist mainly of plagioclase (oligoclase-andesine), quartz and actinolite, and apatite, Muscovite and rutile as accessories. These dikes show a slight metamorphism, developing a foliation and the formation of albite + clinozoisite + kaolinite, which denotes conditions of metamorphism of degree from low to medium. [ABSTRACT FROM AUTHOR]

Phase equilibrium experiments are essential for robustly and accurately constraining the intensive parameters of magma systems and their fractionation history, which is particularly true for A‐type granites crystallized from H2O‐rich melts and at reducing conditions. Here, we constrain the crystallization conditions of the ferroan (A‐type), Sn‐mineralized Qitianling granite of South China, which formed during a major event of crustal formation and reorganization in the Mesozoic. To characterize the magma system conditions and fractionation, we have carried out a series of experiments on three representative, amphibole‐bearing samples. The experiments were performed at 100–700 MPa (mainly at 200 and 300 MPa), at an fO2 of ~NNO−1.3 (1.3 log unit below the Ni‐NiO buffer) or ~NNO+2.4, at 660 to 900 °C, and at variable H2Omelt (~3–9 wt %). They show that the Qitianling magmas last crystallized at ≥300–350 MPa, at a H2Omelt ≥ 6.5–8.0 wt %, and that magmatic fO2 was ~NNO−1.3 ± 0.5 at above‐solidus conditions. Amphibole texture in the rocks suggests an early crystallization of this mineral, hence that water‐rich (≥4 wt % H2O in melt) conditions prevailed early during the magmatic evolution, prior to amphibole crystallization. At all investigated conditions, amphibole crystallization requires at least 5–6 wt % dissolved H2O, being even absent in the more potassic composition. We interpret this as resulting from the elevated K2O content of the investigated compositions that inhibits amphibole crystallization in metaluminous granitic systems. The experimental liquid line of descent obtained at 200–300 MPa mimics the geochemical trend expressed by the pluton suggesting that fractionation occurred in the upper crustal reservoir. Key Points: A‐type Qitianling magmas were produced at high temperature (>900 °C) and with initial H2Omelt ≥ 4 wt %Crystallization of Qitianling granites occurred at ≥300–350 MPa, NNO−1.3 ± 0.5, and near‐solidus H2O melt ≥ 6.5–8.0 wt %Fractionation of the magmas occurred at or close to the level of final emplacement and crystallization [ABSTRACT FROM AUTHOR]

Thermobarogeochemical study of melt inclusions and investigation of clinopyroxenes and amphiboles from effusive rocks of the Uksichan and Ichinsky Volcanoes gave an insight into the parameters of deep-seated melts and the evolution of magmatic systems during the formation of minerals in intermediate chambers. Study of melt inclusions from the Uksichan volcanic rocks made it possible to estimate the pressure during the liquidus crystallization of clinopyroxenes and plagioclases from basaltic magmas and to establish four depth intervals of the formation of these minerals: ~60, 45-30, 27-18, and from 12 km to the subsurface. Comparison of the results of calculation based on melt inclusion data and of the clinopyroxene and amphibole data helped to establish the evolution paths of the P-T parameters of ascending melts of the Uksichan Volcano. The most high-temperature magmas, generated at a depth of ~60 km, are characterized by a successive temperature decrease during their ascent (1320-1240-1200 °C). Based on the representative data on the compositions of amphiboles from the Uksichan and Ichinsky Volcanoes, we have elucidated the general regularities of the evolution of intermediate and acid magmatic systems, with three depths of crystallization in intermediate chambers. Amphiboles of the Ichinsky Volcano andesites and the Uksichan Volcano latites crystallized at depths of 22.0-18.5 and 18-16 km and at temperatures of 980-930 and 1010-985 °C, respectively. As melt ascended to a depth of 15.5-11.0 km and a temperature decreased from 945 to 880 °C, amphiboles of andesites and dacites of both volcanoes were produced. At the final stage (a temperature decrease to 900-810 °C and ascent of melts to a depth of 3 km), only amphiboles of dacites of both volcanoes crystallized. [ABSTRACT FROM AUTHOR]

Based on a compilation of the vast literature, we typify the peculiar mantle-derived adakitic volcanic rocks in the Sea of Okhotsk, Kamchatka, and Bering Sea regions. The low-silica (LSA) and high-silica (HSA) types are distinguished in each region. The prevailing adakite type corresponds to the bimodal basalt–andesite series in the Kamchatka region and the basanite–dacite series in the Bering Sea region. In the Kamchatka region, the formation of LSA was related to the fractionation and melting of pyroxene, while the origin of HSA was related to the fractionation, melting, and breakdown of amphibole. Alkaline metasomatism plays a subordinate role in these processes. In the Bering Sea region, the formation of both types of adakites was mainly controlled by amphibole, with the assistance of alkaline metasomatism. The isotope–geochemical compositions of the adakites and within-plate volcanic rocks shows that both these rock types can be equally regarded as indicators of plume petrogenesis and geodynamics. Based on a comparison of the compositions of the adakites and glasses derived by xenolith melting, a two-stage genetic model is proposed: formation of black pyroxenites through melting of mantle lherzolites and generation of the entire rock complex owing to the repeated melting of the same lherzolites and newly formed pyroxenites. The formation of adakitic and within-plate signatures in the volcanic products beginning from the Eocene indicates the transition of the spacious territory of the NE continental margin from subduction-related compression to a setting of rift extension. [ABSTRACT FROM AUTHOR]

Thermal diffusivity is an important physical parameter for assessing thermal damage to granite. In this paper, hornblende granite and alkaline granite were subjected to cooling and heating cycles at different temperatures. The quenching cycles of hornblende granite are 1, 5, 10, 15 and 20 times between 250 °C and 650 °C. The quenching cycle of the alkaline granite is 1, 5, 10 and 15 times in the range of 250 °C–450 °C, respectively. The thermal diffusivity of the two types of granite was measured. The experimental results show that the thermal diffusivity of amphibole granite and alkaline granite decreases with the increase of the number of cycles at a given heat treatment temperature. When the number of cycles is constant, the thermal diffusivity decreases as the temperature increases. • We conducted different quenching experiments of granite up to 15 cycles and 650 °C. • As the temperature and number of cycles increases, the thermal diffusivity decreases. • Quartz and feldspar are used to evaluate the thermal diffusivity change of granite. [ABSTRACT FROM AUTHOR]

Exposure to Libby Asbestiform Amphibole (LAA) is associated with asbestos-related diseases, including mesothelioma, pulmonary carcinoma, pleural fibrosis, and systemic autoimmune diseases. The pleural fibrosis can manifest as a rapidly progressing lamellar pleural thickening (LPT), which causes thoracic pain, dyspnea, and worsening pulmonary function tests (PFT). It is refractory to treatment and frequently fatal. Objective: Because of the immune dysfunction that has been described in the LAA-exposed population and the association of pleural manifestations with the presence of autoantibodies, this study tested whether specific immunological factors were associated with progressive LPT and whether they could be used as markers of progressive disease. Methods: Subjects were placed into three study groups defined as (1) progressive LPT, (2) stable LPT, (3) no LPT. Serum samples were tested for antinuclear autoantibodies, mesothelial cell autoantibodies, anti-plasminogen antibodies, IL1 beta, and IL17; which have all been shown to be elevated in mice and/or humans exposed to LAA. Results: Group 1 had significantly higher mean values for all of the autoantibodies, but not IL1 or IL-17, compared to the control Group 3. All three autoantibody tests had high specificity but low sensitivity, but ROC area-under-the-curve values for all three antibodies were over 0.7, statistically higher than a test with no value. When all LPT subjects were combined (Progressive plus Stable), no marker had predictive value for disease. Conclusion: The data support the hypothesis that progressive LPT is associated with immunological findings that may serve as an initial screen for progressive LPT. [ABSTRACT FROM AUTHOR]

The paper reports results of an experimental study of amphibole crystallization from the highly magnesian andesite melt of Shiveluch volcano, Kamchatka. The experiments were carried out in IHPV at 300 MPa and 940–980°С in iron-saturated platinum capsules, using rapid quenching and temperature oscillations (in some experiments). The redox state of iron in the system was measured before and after the experiments using Mössbauer spectroscopy. The maximum size of the experimental amphibole crystals (up to 200 μm) was close to those of natural amphibole phenocrysts in the volcanic rocks of Shiveluch volcano. The experimental data show that the content of octahedrally coordinated Al (Al6) in the amphibole considerably varies with small variations in the intensive parameters (P, T, and ) and composition of the melt, and the maximum Al6 concentration can be evaluated only by using a reasonably large dataset of amphibole analyses. A modified 13eCNK method is suggested to calculate the values of Al6 and Fe3+/Fe2+ with regard for the Ti concentration and the probable partial transfer of Mg into site B in high-Mg amphibole. Calculations with this modified technique yield lower Fe3+/Fe2+ and higher Al6 values. Our experimental data show that the temperature of amphibole liquidus crystallization decreases from about 990°C to 960°C when the oxygen fugacity drops from NNO + 1.5 to NNO + 0.4. In view of this, the transition from amphibole-bearing to anhydrous mineral assemblage in the magmas of Shiveluch volcano might have been caused by variations of the oxygen fugacity but not water. The application of our geobarometer to amphiboles from Shiveluch volcano (extrusions Krasnaya and Karan) yields the highest pressure estimate of above 1 GPa, corresponding to the P–T conditions of the melting of garnet-bearing amphibolite in the lower crust. [ABSTRACT FROM AUTHOR]

Potassic-jeanlouisite, ideally K(NaCa)(Mg4Ti)Si8O22O2, is the first characterised species of oxo amphibole related to the sodium–calcium group, and derives from potassic richterite via the coupled exchange CMg–1W ${\rm OH}_{{\rm \ndash 2}}^{\ndash}{} ^{\rm C}{\rm Ti}_1^{{\rm 4 +}} {} ^{\rm W}\!{\rm O}_2^{2\ndash} $. The mineral and the mineral name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification, IMA2018-050. Potassic-jeanlouisite was found in a specimen of leucite which is found in the lava layers, collected in the active gravel quarry on Zirkle Mesa, Leucite Hills, Wyoming, USA. It occurs as pale yellow to colourless acicular crystals in small vugs. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: A(K0.84Na0.16)Σ1.00B(Ca0.93Na1.02Mg0.04 ${\rm Mn}_{{\rm 0}{\rm. 01}}^{2 +} $)Σ2.00C(Mg3.85 ${\rm Fe}_{{\rm 0}{\rm. 16}}^{2 +} $ Ni0.01 ${\rm Fe}_{{\rm 0}{\rm. 33}}^{3 +} {\rm V}_{{\rm 0}{\rm. 01}}^{3 +} $ Ti0.65)Σ5.01T(Si7.76Al0.09Ti0.15)Σ8.00O22W[O1.53F0.47]Σ2.00. The holotype crystal is biaxial (–), with α = 1.674(2), β = 1.688(2), γ = 1.698(2), 2Vmeas. = 79(1)° and 2Vcalc. = 79.8°. The unit-cell parameters are a = 9.9372(10), b = 18.010(2), c = 5.2808(5) Å, β = 104.955(2)°, V = 913.1(2) Å3, Z = 2 and space group C 2/ m. The strongest eight reflections in the powder X-ray pattern [ d values (in Å) (I) (hkl)] are: 2.703 (100) (151); 3.380 (87) (131); 2.541 (80) ($\bar 2$ 02); 3.151 (70) (310); 3.284 (68) (240); 8.472 (59) (110); 2.587 (52) (061); 2.945 (50) (221, $\bar 1$ 51). [ABSTRACT FROM AUTHOR]

Amphibole is thought to be a key control on the differentiation of arc magmas but the fractionation of this mineral remains enigmatic because it is rarely present in erupted lavas. This study presents detailed petrological, mineralogical, and geochronological data for newly identified Late Triassic (217–215 Ma) mafic intrusive rocks from the Gangdese arc of southern Tibet. These gabbros host an amphibole-rich cumulate enclave and clinopyroxene crystal clots, including two mineral assemblages in chemical disequilibrium: (1) amphibole and Type-1 clinopyroxene within the enclave and clots; and (2) small crystals of Type-2 clinopyroxene, plagioclase, and biotite within the host. Textural and geochemical evidence indicate that the enclave and clots represent captured fragments of amphibole- and clinopyroxene-dominated lower crustal crystal mushes, respectively, whereas small host crystals formed by the shallow crystallization of evolved melts extracted from these crystal mushes. The compositional variations between the two types of clinopyroxene also reveal this melt segregation process. Amphibole with similar rare earth element patterns to associated Type-1 clinopyroxene inclusions suggest that the former formed through peritectic reactions consuming clinopyroxene. Enhanced amphibole fractionation may also have occurred as a result of the presence of high-density clinopyroxene inclusions. This indicates that the fractionation of amphibole together with precursory clinopyroxene inclusions within the deep crust controls the early chemical evolution of mafic arc magmas, a process that is consistent with the geochemical variations in lavas from three other active arc volcanoes. The associated cumulates can efficiently delaminate back into the mantle, ultimately leading to the generation of SiO 2 -rich continental crustal material. • Late Triassic mafic rocks represent early products of Indus–Yarlung Zangbo Tethyan subduction. • The amphibole-rich enclave and clinopyroxene crystal clots were derived by crystal fractionation. • The fractionation of amphibole and clinopyroxene precursors occurs in the deep arc crust. • This fractionation controls the early chemical evolution of arc magmas. [ABSTRACT FROM AUTHOR]

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Exposure to the Libby amphibole (LA) asbestos-like fibers found in Libby, Montana, is associated with inflammatory responses in mice and humans, and an increased risk of developing mesothelioma, asbestosis, pleural disease, and systemic autoimmune disease. Flaxseed-derived secoisolariciresinol diglucoside (SDG) has anti-inflammatory, anti-fibrotic, and antioxidant properties. We have previously identified potent protective properties of SDG against crocidolite asbestos exposure modeled in mice. The current studies aimed to extend those findings by evaluating the immunomodulatory effects of synthetic SDG (LGM2605) on LA-exposed mice. Male and female C57BL/6 mice were given LGM2605 via gavage initiated 3 days prior to and continued for 3 days after a single intraperitoneal dose of LA fibers (200 μg) and evaluated on day 3 for inflammatory cell influx in the peritoneal cavity using flow cytometry. LA exposure induced a significant increase (p < 0.0001) in spleen weight and peritoneal influx of white blood cells, all of which were reduced with LGM2605 with similar trends among males and females. Levels of peritoneal PMN cells were significantly (p < 0.0001) elevated post LA exposure, and were significantly (p < 0.0001) blunted by LGM2605. Importantly, LGM2605 significantly ameliorated the LA-induced mobilization of peritoneal B1a B cells. LGM2605 reduced LA-induced acute inflammation and WBC trafficking supporting its possible use in mitigating downstream LA fiber-associated diseases. Following acute exposure to Libby amphibole (LA) asbestos-like fibers, synthetic SDG (LGM2605), a small synthetic molecule, significantly reduced the LA-induced increase in spleen weight and peritoneal inflammation in C57BL/6 male and female mice. Our findings highlight that LGM2605 has immunomodulatory properties and may, thus, likely be a chemopreventive agent for LA-induced diseases. • Libby Amphibole (LA)-induced diseases are linked to early inflammatory events. • We demonstrate that LGM2605 significantly reduces LA-induced splenomegaly. • LGM2605 reduces LA-induced peritoneal influx of white blood cells (WBCs). • LGM2605 specifically reduces WBC subtypes associated with autoimmune responses. • LGM2605's immunomodulatory properties may be linked to potential chemoprevention. [ABSTRACT FROM AUTHOR]

The paper presents new geological, petrological, and geochemical data on the dunite–clinopyroxenite–gabbro massifs of the Tamanvayam area. The time of formation of the intrusions is specified using U–Pb zircon dating. The Machevna Massif is mainly composed of gabbroids and clinopyroxenites, which are related by gradual facies transitions and intruded by amphibole gabbro, leucogabbro, and monzogabbro. The youngest rocks, cutting across all of the above-described varieties, are granites and granodiorites (tonalites), which make up composite injection bodies and small stocks in the central part of the massif. According to the new U–Pb dates, all of the intrusive rocks of the Machevna and Poputny intrusions were formed in a narrow time range of 73.1–67.7 Ma. The obtained range overlaps the formation interval of the siliceous volcanogenic sequences of the Achaivayam Formation (biostratigraphic studies, retrospective data). The geochemical similarity of the gabbroids and pyroxenites with intersecting amphibole gabbros and leuco- and monzogabbros allows us to attribute them to a single magmatic complex. The geochemical affinity and the penecontemporaneous formation of the intrusive rocks of the Tamanvayam area and volcanics of the Achaivayam Formation indicate their formation during a single tectonomagmatic event. At the same time, the gabbroids and pyroxenites can be considered as comagmatic rocks of the basalts and picrobasalts of the Achaivayam Formation. The high-Ca picrobasalts of the Achaivayam Formation that developed near the Machevna intrusion were presumably derived from parental melts of concentrically zonal massifs. [ABSTRACT FROM AUTHOR]

The Zorin and Chingandzha floras significantly differ in their systematic composition, but they are buried at the same stratigraphic level. On this basis, they are considered to be of the same age and are assigned to the Turonian–Coniacian period. The revealed features of the lithological composition of the plant-bearing deposits, their sequence, and the composition of the overlaying volcanic rocks indicate that both floras represent the first stage of the development of the outer zone of the Okhotsk–Chukotka Volcanic Belt. However, they are separated by one or two local geological events, and hence by a significant period of time. It can be confirmed that the Zorin flora was formed and existed earlier than the Chingandzha flora. [ABSTRACT FROM AUTHOR]