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This New Mineral Names has entries for 11 new minerals, including cesiodymite, cryptochalcite, feodosiyite, fluoro-tremolite, itelmenite, ozerovaite, ramazzoite, redcanyonite, selivanovite, vanderheydenite, and wrightite

Calcic, igneous amphiboles are of special interest as their compositional diversity and common occurrence provide ample potential to investigate magmatic processes. But not all amphibole-based barometers lead to geologically useful information: recent and new tests reaffirm prior studies (e.g., ), indicating that amphibole barometers are generally unable to distinguish between experiments conducted at 1 atm and at higher pressures, except under highly restrictive conditions. And the fault might not lie with experimental failure. Instead, the problem may relate to an intrinsic sensitivity of amphiboles to temperature ( ) and liquid composition, rather than pressure. The exceptional conditions are those identified by : current amphibole barometers are more likely to be useful when < 800 °C and Fe# = Fe / (Fe +Mg ) < 0.65. Experimentally grown and natural calcic amphiboles are here used to investigate amphibole solid solution behavior, and to calibrate new thermometers and tentative amphibole barometers that should be applicable to igneous systems generally. Such analysis reveals that amphiboles are vastly less complex than may be inferred from published catalogs of end-member components. Most amphiboles, for example, consist largely of just three components: pargasite [NaCa (Fm Al)Si Al ], kaersutite [NaCa (Fm Ti)Si Al (OH)], and tremolite + ferro-actinolite [Ca Fm Si (OH) , where Fm = Fe+Mn+Mg]. And nearly all remaining compositionalvariation can be described with just four others: alumino-tschermakite [Ca (Fm Al )Si Al (OH) ], a Na-K-gedrite-like component [(Na, K)Fm AlSi Al (OH) ], a ferri-ferrotschermakite-like component [Ca (Fm Fe )Si Al (OH) ], and an as yet unrecognized component with 3 to 4 Al atoms per formula unit (apfu), 1 apfu each of Na and Ca, and <6 Si apfu, here termed aluminous kaersutite: NaCaFm Ti(Fe , Al) Si Al (OH). None of these components, however, are significantly pressure ( ) sensitive, leaving the Al-in-amphibole approach, with all its challenges, the best existing hope for an amphibole barometer. A new empirical barometer based on successfully differentiates experimental amphiboles crystallized at 1 to 8 kbar, at least when multiple estimates, from multiple amphibole compositions, are averaged. Without such averaging however, amphibole barometry is a less certain proposition, providing ±2 kbar precision on individual estimates for calibration data, and ±4 kbar at best for test data; independent checks on are thus needed. Amphibole compositions, however, provide for very effective thermometers, here based on , , and amphibole compositions alone, with precisions of ±30 °C. These new models, and tests for equilibrium, are collectively applied to Augustine volcano and the 2010 eruption at Merapi. Both localities reveal a significant cooling and crystallization interval (>190–270 °C) at pressures of 0.75 to 2.2 kbar at Augustine and Merapi, respectively, perhaps the likely depths from which pre-eruption magmas are stored. Such considerable intervals of cooling at shallow depths indicate that mafic magma recharge is not a proximal cause of eruption. Rather, eruption triggering is perhaps best explained by the classic “second boiling” concept, where post-recharge cooling and crystallization drive a magmatic system toward vapor saturation and positive buoyancy.

Greyish-purple tremolite jade has become well known in the past few years, and the origin of its color has attracted the attention of gemologists. In this study, FT-IR spectra, EPMA, EPR spectra, micro-XRF, UV–Vis–NIR spectra, and LA-ICP-MS in situ mapping were analyzed to investigate the chromophore elements. The study sample was chosen from the Sanchahe mine, Qinghai Province, NW China, which has the typical characteristics of a gradual color change. The FT-IR and EPMA results revealed that the mineral composition of the dark and light greyish-purple regions of the sample are primarily composed of tremolite. UV–Vis–NIR spectra demonstrated that the greyish-purple color is mainly due to strong absorptions at 560 nm and 700 nm and weak absorption at 745 nm in the visible range. The EPR spectra presented ~3400 G six hyperfine lines resulting from the hyperfine interactions of the unpaired electron with the Mn2+ nucleus in the octahedral site. The UV–Vis–NIR and EPR spectra analyses demonstrated that Mn2+ is the origin of the purple color. A comparison of the major elements in the light and dark regions indicated that the chromogenic elements have strong positive correlations with Mn, Cu, and Fe. LA-ICP-MS mapping used to analyze the first transition metals indicated possible positive correlations between the greyish-purple color and the trace chromogenic elements. This suggested that the Mn, Cu, and Fe contents are significantly high in the dark band region. Combining in situ LA-ICP-MS mapping of trace elements, UV–Vis spectra, and EPR analysis results, it was suggested that Mn, Cu, and Fe are the major contributors to the greyish-purple color. This study provides a reference for the specific experimental methods to determine chromophores and the origin of color in tremolite jades.

The nephrite belt in the Altun Mountain–Western Kunlun Mountain region, which extends about 1300 km in Xinjiang, NW China, is the largest nephrite deposit in the world. The Qiemo region in the Altun Mountains is a crucial nephrite-producing area in China, with demonstrated substantial prospects for future exploration. While existing research has extensively investigated secondary nephrite deposits in the Karakash River and native black nephrite deposits in Guangxi Dahua, a comprehensive investigation of black nephrite from original deposits in Xinjiang is lacking. Margou black-toned nephrite was recently found in primary deposits in Qiemo County, Xinjiang; this makes in-depth research on the characteristics of this mine necessary. A number of technical analytical methods such as polarizing microscopy, Ultra-Deep Three-Dimensional Microscope, electron microprobe, back-scattered electron image analysis, X-ray fluorescence, and inductively coupled plasma mass spectrometry were employed for this research. An experimental test was conducted to elucidate the chemical and mineralogical composition, further clarifying the genetic types of the black and black cyan nephrite from the Margou deposit in Qiemo, Xinjiang. The results reveal that the nephrite is mainly composed of tremolite–actinolite, characterized by Mg/(Mg + Fe2+) ratios ranging from 0.86 to 1.0. Minor minerals include diopside, epidote, pargasite, apatite, zircon, pyrite, and magnetite. Bulk-rock rare earth element (REE) patterns exhibit distinctive features, such as negative Eu anomalies (δEu = 0.00–0.17), decreasing light REEs, a relatively flat distribution of heavy REEs, and low total REE concentrations (1.6–38.9 μg/g); furthermore, the Cr (6–21 μg/g) and Ni (2.5–4.5 μg/g) contents are remarkably low. The magmatic influence of granite appears to be a fundamental factor in the genesis of the magnesian skarn hosting Margou nephrite. The distinctive black and black cyan colors are attributed to heightened iron content, mainly associated with FeO (0.08~6.29 wt.%). Analyses of the chemical composition allow Margou nephrite to be classified as typical of magnesian skarn deposits.

Metasomatized mantle xenoliths containing hydrous minerals, such as amphiboles, serpentine, and phlogopite, likely represent the potential mineralogical compositions of the metasomatized upper mantle, where low seismic velocities are commonly observed. This study presents the first experimentally determined single‐crystal elasticity model of an Fe‐free near Ca, Mg‐endmember amphibole tremolite at high pressure and/or temperature conditions (maximum pressure 7.3(1) GPa, maximum temperature 700 K) using Brillouin spectroscopy. We found that sound velocities of amphiboles strongly depend on the Fe content. We then calculated the sound velocities of 441 hydrous‐mineral‐bearing mantle xenoliths collected around the globe, and quantitatively evaluated the roles that amphiboles, phlogopite and serpentine played in producing the low velocity anomalies in the metasomatized upper mantle. Plain Language Summary Amphiboles are the most widely distributed hydrous minerals resulting from metasomatism in the upper most mantle. We measured sound velocities of tremolite (Ca, Mg endmember of the amphibole series) at high pressures and high temperatures by Brillouin spectroscopy. Based on global hydrous‐mineral‐bearing mantle xenoliths record, we quantitively evaluated the contributions of amphiboles, serpentine, and phlogopite to low velocity anomalies and water storage in the upper most mantle. We found the existence of hydrous minerals (amphiboles, serpentine, and phlogopite) remains a viable explanation for the low velocity anomalies in the upper most mantle (e.g., mid‐lithosphere discontinuity). Compared to serpentine and phlogopite, although the amount of velocity reduction caused by amphibolization is moderate, the formation of amphiboles does not require K, Al, Si‐rich environments like phlogopite, or exceedingly water‐rich environments like serpentine. Key Points The single‐crystal elasticity of tremolite is determined by Brillouin spectroscopy up to 7.3 GPa and 700 K Sound velocities of uppermost mantle amphiboles mainly depend on Fe content Hydrous minerals (amphiboles, serpentine, phlogopite) are plausible causes of the low velocity anomalies in the uppermost mantle

The tremolite nephrite deposit in Dahua county, Hechi City, Guangxi province, China is a new genetic type of nephrite deposit. It is hosed by Mg-poor limestone (~1.30 wt.% MgO) and intruded by diabase (~45 wt.% SiO2). The Mg and Si contents of these rocks are lower than those of the tremolite (58.18 wt.% SiO2, 13.18 wt.% CaO, 24.16 wt.% MgO), indicating an obviously insufficient source for the metallogenic material that generated the deposit. In particular, some tremolite nephrite ore bodies have no clear contact metamorphism between the host and intrusive rocks, which have the characteristics of stratified mineralization (stratified tremolite nephrite). The origin and mineralization of stratified tremolite nephrite remain poorly constrained. To address this shortcoming, the mineralogy, geochemistry and Sr isotopic of host rock, altered marble, stratified tremolite nephrite and intrusive rock in the Dahua stratified tremolite nephrite deposit were studied. The results show: stratified tremolite nephrite mainly consists of aggregates of microcrystalline-cryptocrystalline tremolites with content exceeding 95%. The in situ rare earth elements (REEs) distribution pattern of hydrothermal calcite in the contact position between stratified tremolite nephrite and marble is similar to that of marine carbonate rock, showing obvious enrichment of HREE, which is different from calcite in limestone and marble. 87Sr/86Sr of stratified tremolite nephrite is relatively uniform, with an average value of 0.7070, within the range of Permian seawater. The mean value of Y/Ho in the hydrothermal calcite is 51.24, indicating that the marine fluid has not been impregnated by terrigenous materials. In summary, the hydrothermal fluid rich in Ca and Si is formed after marine carbonate rocks are altered by marine fluids. Hydrothermal fluids alter diabase rocks formed by altered minerals like titanite, chamosite, zoisite, etc. This process leads to the formation of metallogenic hydrothermal fluids abundant in Si, Ca, Fe and Mg. The metallogenic hydrothermal fluids migrate in faults and fractures of marble and crystallize to form tremolite nephrite under suitable ore-forming conditions.

Tremolite asbestos is classified as a carcinogenic substance because it can cause a number of diseases when inhaled. The tremolite breakdown temperature reported in the literature varies by about 280 °C and has not been fully characterized from a thermal perspective. In order to address this gap in the scientific literature, a systematic study of the thermal behavior was conducted of twelve tremolite samples using thermogravimetric and differential scanning calorimetry (TG/DSC) supplemented by PXRD, SEM/EDS, EPMA/EDS and TEM/EDS. Tremolite samples from different locations (i.e., Italy, Switzerland and USA) were selected for their social, health, economic and industrial relevance. Data reveal that the breakdown of tremolite occurs in a temperature range of about 200 °C. The implications of this finding are discussed in light of chemical and morphological data. Variations in the breakdown temperature are mainly ascribed to the morphology of the studied tremolite samples. This study suggests that thermal analysis could be a new method for effectively distinguishing between asbestos and non-asbestos tremolite samples. The thermal oxidation of iron in the various tremolite samples occurs at different temperatures, and hence reduction of tremolite reactivity through the thermal oxidation of iron should be planned on a sample-by-sample basis. Given the different temperatures recorded for tremolite breakdown, the effectively detecting the presence of tremolite in bulk natural samples by thermal analysis can only be carried out if a thermogram of that specific sample is available. This is an important issue, especially in areas with a natural occurrence of asbestos outcrops. Graphical Abstract

We studied the chemical composition and morphostructural features of micron and submicron-sized particles of native gold in apocarbonate tremolite–diopside skarns of the Ryabinovoye deposit located on the southeastern margin of the Aldan Shield (Far East, Russia). Polished sections of lump ore samples containing native gold were analyzed by scanning electron microscopy in combination with X-ray microanalysis using different modes of visualization and X-ray diffraction methods. Gold particles, clearly visible after etching the surface of some polished sections with acids and partial or complete dissolution of some host minerals, were also examined. Native gold from the studied deposit is of high fineness (above 970‰) and contains (in wt.%) <1.59 Ag and less commonly <0.37 Cu and <0.15 Zn. Native gold is found intergrown with tremolite, diopside, and other magnesian silicates, as well as calcite, fluorite, magnetite, and sphalerite. Rare microinclusions of pyrrhotite, galena, and clinohumite are present in gold grains. It was found that native gold inherits the morphology of tremolite crystals and aggregates, which is determined by the size and shape of the voids bounded by its crystals. Gold localized in the intercrystalline spaces and in the zones of conjugation with remobilized calcite has irregular, lumpy shapes and partially or completely faceted grains with a dense structure. The nature of the localization and distribution of native gold in ores is due to the crystallization of the tremolite component of skarns. Apparently, the processes of gold accumulation are caused by the thermal activation of solid-phase differentiation of the substance of carbonate rocks, in which the processes of destruction of the original minerals and collective recrystallization play a significant role. It is likely that at some gold skarn deposits, carbonate rocks could be the source of gold. Data on the morphology and sizes of native gold segregations, as well as on the intergrown minerals, can be used to improve gold extraction technologies. A specific group of minerals intergrown with native gold in gold skarn deposits can be used as a diagnostic feature in the primary search for placer gold. The obtained results will help to better understand the formation of native gold in apocarbonate tremolite–diopside skarns.

This study aimed at investigating the surface modifications occurring on amphibole asbestos (crocidolite and tremolite) during leaching in a mimicked Gamble’s solution at pH of 4.5 and T = 37 °C, from 1 h up to 720 h. Results showed that the fibre dissolution starts with the release of cations prevalently allocated at the various M - and (eventually) A -sites of the amphibole structure (incongruent dissolution). The amount of released silicon, normalized to fibre surface area, highlighted a leaching faster for the crocidolite sample, about twenty times higher than that of tremolite. Besides, the fast alteration of crocidolite promotes the occurrence of Fe centres in proximity of the fibre surface, or possibly even exposed, particularly in the form of Fe(II), of which the bulk is enriched with respect to the oxidized surface. Conversely, for tremolite fibres the very slow fibre dissolution prevents the underlying cations of the bulk to be exposed on the mineral surface, and the iron oxidation, faster than the leaching process, significantly depletes the surface Fe(II) centres initially present. Results of this work may contribute to unravel possible correlations between surface properties of amphibole asbestos and its long-term toxicity.

Metasomatism of the subducting slab and mantle wedge influences the rheological and chemical properties of rocks at the subduction zone interface. We investigated a serpentinite body that originated from the mantle wedge in the Tomisato area of the Sanbagawa metamorphic belt, SW Japan. At the boundary between the serpentinite body and a pelitic schist, metasomatic reaction zones have developed, consisting of pelitic schist, albite schist, muscovite rock, chlorite rock, tremolite schist, talc schist, talc + serpentine rock, and serpentinite. Using petrological observations, we showed that metasomatism at the interface occurred around the peak P–T conditions (0.8–1.0 GPa and 530–570 °C), which correspond to those at the mantle wedge corner. Mass balance calculations revealed that the metasomatism of the pelitic schist was accompanied by the removal of Si and Ca and the addition of Mg, whereas the metasomatism of the serpentinite was accompanied by the addition of Ca and Al. The Ca was supplied externally, and Na, K, and C were released to an external system. Fluid-mediated mass transfer induces formation of tremolite-rich rocks after serpentinite and chlorite-rich rocks after metasediments, which could be widespread along the subduction interface and the mantle wedge corner. We propose that metasomatism at the mantle wedge corner redistributes elements between fluids and rocks, introduces spatial heterogeneities in the mineral assemblages in the mantle wedge and subducting slab, and that it could produce fluid overpressure. Consequently, such metasomatism would influence slab–mantle decoupling and seismicity.