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The present study aims to apply the principles of circular economy, using special inorganic waste (in particular, red gypsum muds from a TiO2 plant in Tuscany, Italy) to produce ceramic materials for the construction and building industries. Red gypsum (RG) muds produced during more than 10 years of industrial processing were chemically and mineralogically characterized by X-ray fluorescence spectrometry (XRF), X-ray powder diffraction (XRPD), scanning electron microscopy with energy dispersive X-ray spectrometer (SEM/EDS), and thermal analyses (TA). The analyses testify that RG waste production is chemically and mineralogically constant over time, and therefore suitable to be used as a secondary raw material in industrial ceramic production. Ceramic specimens have been realized using an extremely high amount of the RG waste (up to 70%) and characterized using the same chemical-mineralogical techniques, revealing that anhydrite, pyroxene, and Fe/Ti oxides are the main crystalline phases, embedded in a glassy compact matrix. Overall results indicate that the production of ceramic materials could represent a definitive and sustainable solution for the problematic management of the large volumes of RG waste deriving from TiO2 plants.

The products of cement–asbestos treated in air at 1100°C were characterized by a multi-methodological approach to determine: (i) the effective deactivation of harmful asbestos fibers; (ii) the mineralogy and microstructure of the inert product and its possible use as a secondary raw material (SRM); and (iii) any potential health hazard of the SRM. For this purpose, energy-dispersive X-ray fluorescence spectrometry (EDXRF), X-ray powder diffraction (XRPD), scanning, and transmission electron microscopy (SEM and TEM) analyses were performed. The powdered SRM was also analyzed by dynamic laser scattering and solution leaching experiments, to determine grain size distribution and possible elements release. Our results confirm the deactivation of crocidolite and chrysotile asbestos fibers, but at the same time evidence a significant fraction of nanoparticles in the SRM and some critical releases of SO42–, F– and Cr6+ in solution. Both the nanoparticle fraction and the critical elemental release may pose human health concern and adversely affect potential applications of the SRM. Strategies to control the grain size distribution through adjusted thermal treatment conditions and microwave-assisted grinding operations are discussed. Possible routes to safely reuse the SRM are indicated.

The Pennine Basal Thrust (PBT) is an exhumed megathrust developed during continental collision from late Eocene to Miocene. To trace its evolution, five samples, with indications for up to three microstructurally diachronous white-mica generations, were investigated by laser in-situ and step-heating Ar-40-Ar-39 dating. Three deformation-related crystallization ages can be distinguished: (1) D-1, characterized in the PBT hanging wall by an S-1 foliation defined by white mica + chloritoid, began at or before similar to 38.0 Ma; (2) D-2 formed a pervasive S-2 cleavage and synchronous white-mica rich veins dated at similar to 27 Ma; (3) D(3)produced an S-3 crenulation cleavage and chlorite + white-mica veins dated at similar to 23 Ma. Older ages of similar to 96 Ma (footwall) and similar to 115 Ma (hanging wall) are interpreted as minimum ages for the detrital component. Finally, discrete faulting produced fault gouge, with an illite K-Ar age of similar to 19 Ma. A simplified back-restored reconstruction provides a tectonic context for the dated structures. In this framework, D-1 occurred during middle to late Eocene tectonic accretion. After late Eocene initiation of continental collision, D-2 reflects Oligocene top-to-NW shearing, with both in- and out-of-sequence thrusting. D-3 then developed from 23 to 19 Ma during the progressive deactivation of the PBT.

Nowadays, asbestos-containing wastes (ACW) still represent an important environmental problem and a severe health hazard due to the well know pulmonary diseases derived from asbestos fibres inhalation. Except for a very few cases, ACW are currently confined in controlled landfills, giving rise to increasingly high amounts of still hazardous wastes. A promising alternative to landfill confinement is represented by ACW inertization, but the high cost of the inertization processes so far proposed by the scientific community have hampered the creation of actually operative plants. In this paper, we explore the possibility to use an innovative process that ensures the obtainment of asbestos-free inert material in an exceptionally short processing time, thus greatly reducing cost-related problems. The efficacy of the inertization process has been verified through accurate mineralogical investigations on both chrysotile and crocidolite de-activated fibres, through X-ray diffraction, scanning and transmission electron microscopy. Overall mineralogical, microstructural and granulometric characteristics of the inert bulk material suggest that it could be successfully re-used as a secondary raw material in ceramic industries. This innovative inertization procedure could therefore provide an effective and economically sustainable solution for ACW management.

Alkaptonuria (AKU) is a hereditary disorder that results from altered structure and function of homogentisate 1,2 dioxygenase (HGD). This enzyme, predominantly produced by liver and kidney, is responsible for the breakdown of homogentisic acid (HGA), an intermediate in the tyrosine degradation pathway. A deficient HGD activity causes HGA levels to rise systemically. The disease is clinically characterized by homogentisic aciduria, bluish-black discoloration of connective tissues (ochronosis) and joint arthropathy. Additional manifestations are cardiovascular abnormalities, renal, urethral and prostate calculi and scleral and ear involvement. While the radiological aspect of ochronotic spondyloarthropathy is known, there are only few data regarding an exhaustive ultrastructural and histologic study of different tissues in AKU. Moreover, an in-depth analysis of tissues from patients of different ages, having varied symptoms, is currently lacking. A complete microscopic and ultrastructural analysis of different AKU tissues, coming from six differently aged patients, is here presented thus significantly contributing to a more comprehensive knowledge of this ultra-rare pathology.

Alkaptonuria (AKU) is a disease caused by a deficient homogentisate 1,2-dioxygenase activity leading to systemic accumulation of homogentisic acid (HGA), that forms a melanin-like polymer that progressively deposits onto connective tissues causing a pigmentation called "ochronosis" and tissue degeneration. The effects of AKU and ochronotic pigment on the biomechanical properties of articular cartilage need further investigation. To this aim, AKU cartilage was studied using thermal (thermogravimetry and differential scanning calorimetry) and rheological analysis. We found that AKU cartilage had a doubled mesopore radius compared to healthy cartilage. Since the mesoporous structure is the main responsible for maintaining a correct hydrostatic pressure and tissue homoeostasis, drastic changes of thermal and rheological parameters were found in AKU. In particular, AKU tissue lost its capability to enhance chondrocytes metabolism (decreased heat capacity) and hence the production of proteoglycans. A drastic increase in stiffness and decrease in dissipative and lubricant role ensued in AKU cartilage. Multiphoton and scanning electron microscopies revealed destruction of cell-matrix microstructure and disruption of the superficial layer. Such observations on AKU specimens were confirmed in HGA-treated healthy cartilage, indicating that HGA is the toxic responsible of morphological and mechanical alterations of cartilage in AKU.

A new integrated micropalaeontological study on planktonic and benthic foraminifera, calcareous nannofossils and diatoms was performed on three sediment cores from the Storfjorden Trough Mouth Fan to reconstruct the Late Quaternary palaeoenvironmental and climatic history. Two main intervals were discussed: the last deglaciation (16.2–11.7 ka BP) and the Holocene. The age model relies on palaeomagnetic parameters together with 10 radiocarbon dates. Deglacial sediments had largely diluted the biogenic content which was scarce and poorly preserved. The first occurrence of Cibicidoides wuellerstorfi (benthic foraminifer), together with Turborotalita quinqueloba (planktonic foraminifer) and Coscinodiscus spp. (diatoms) at 11.3 ka BP followed the end of the Younger Dryas cold event and marked the beginning of the early Holocene warm period. Diatoms and planktonic foraminifers indicated a warming of the surface water from 10.5 to 9.2 ka BP, identifying the Holocene Thermal Maximum event. Bottom water fauna registered these warming conditions less clearly. Cooling events were identified during the Holocene, in particular the 8.2 ka BP event and the Neoglacial between 3.2 and 2 ka BP, as shown by the presence of cold-water taxa such as Gephyrocapsa muellerae (nannoplankton) and Neogloboquadrina pachyderma (planktonic foraminifer). These events were influenced by sea ice extent, cold or relatively warm current influxes.

The inner Northern Apennines belt (i.e., northern Tyrrhenian Sea and Tuscany) is an Alpine chain affected by high-P metamorphic conditions during its evolution. Although Elba Island is structurally located close to the Adria-Europe suture zone, for several authors it represents a sector of the orogen affected by low-P metamorphism. The involvement of Elba Island tectonic units in high-P metamorphism was only suspected for the sparse presence of phengitic white mica in the metasedimentary rocks. This paper presents the first clear evidence of high-P and low-T metamorphism found in metabasite rocks embedded in the Cretaceous calcschist of eastern Elba Island. Mineral composition of metabasite includes Gln + Cpx + Ep + Ab + Act + Qtz + Ilm ± Ti-oxide ± Spn and is indicative of a former equilibration in the epidote blueschist subfacies and subsequent retrogression in the greenschist facies. Recorded metamorphic conditions are P = 0.9–1.0 GPa and T = 330–350 °C. Tectonic discrimination using immobile elements in the metabasite does not point to an oceanic setting. As a consequence, the metasedimentary succession containing metabasite is explained as belonging to the Tuscan continental domain and not to the Ligurian-Piedmont Ocean, as previously interpreted. Our results have two significant implications: (i) it is confirmed and strengthened that the tectonic stacking of the Elba Island units did not occur in a low-pressure context; (ii) Elba Island is now completely reconciled in the tectonic and metamorphic evolution of the inner Northern Apennines.

The present study deals with heavy mineral analysis of late Early Miocene marine sediments recovered in the McMurdo Sound region (Ross Sea, Antarctica) during the ANDRILL—SMS Project in 2007. The main objective is to investigate how heavy mineral assemblages reflect different source rocks and hence different provenance areas. These data contribute to a better understanding of East Antarctica ice dynamics in the Ross Sea sector during the Early Miocene (17.6–20.2 Ma), a time of long-term global warming and sea level rise. The AND-2A drill core recovered several stratigraphic intervals that span from Early Miocene to Pleistocene and it collected a variety of terrigenous lithologies. The heavy mineral assemblages of the lower 650-m-thick sedimentary succession were analyzed through SEM observations and SEM–EDS microanalyses on heavy mineral grains. The heavy mineral analysis shows that the sediments are a mix of detritus dominated by McMurdo Volcanic Group sources most likely located in the present-day Mount Morning area (Proto-Mount Morning) with minor contribution from Transantarctic Mountains source rocks located west of the drill site. The heavy mineral assemblages in Interval 1 indicate that between 20.2 and 20.1 Ma, the grounding line of the ice sheet advanced to a position near the present-day Mount Morning volcanic center. During deposition of Interval 2 (20.1–19.3 Ma), the ice sheet most likely experienced a dynamic behavior with interval of ice advance alternating with periods of ice retreat, while Interval 3 (19.3–18.7 Ma) records further retreat to open water conditions. A dynamic behavior is noted in Interval 4 (18.7–17.6 Ma) with a decreasing contribution of materials derived from the basalts of the Mount Morning volcanic center located to the south of the drill site and a consequent increasing contribution of materials derived from the Transantarctic Mountains to the west of the drill site.

Alteration minerals, assemblages, and textures were studied in a 175-m-thick volcanic sequence found between 759.32 and 584.19 m below seafloor within the 1285-m-long ANDRILL (Antarctic Geological Drilling project) McMurdo Ice Shelf core (MIS AND-1B). Three main alteration zones were identified through the application of different analytical methods (optical and scanning electron microscopy, electron microprobe, and X-ray diffraction). Alteration zoning is guided by the texture of the volcanic deposits, which is in turn determined by the eruptive style, transport mechanisms, and paleodepositional conditions. In particular, alteration reflects the evolution of paleodepositional conditions from submarine or shallow water to subaerial due to the growth of a nearby volcanic edifice. The general alteration trend is also influenced by the contribution of volcanogenic sediments derived from the reworking of silica-rich pyroclasts from earlier volcanic activity.

Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23-14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3-4 degrees C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major dis-conformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO2 concentrations were at or below preindustrial levels (similar to 280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (similar to 500 ppm) atmospheric CO2. These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO2 during the early to mid-Miocene.

Stratigraphic drilling from the McMurdo Ice Shelf in the 2006/2007 austral summer recovered a 1284.87 m sedimentary succession from beneath the sea floor. Key age data for the core include magnetic polarity stratigraphy for the entire succession, diatom biostratigraphy for the upper 600 m and 40Ar/39Ar ages for in-situ volcanic deposits as well as reworked volcanic clasts. A vertical seismic profile for the drill hole allows correlation between the drill hole and a regional seismic network and inference of age constraint by correlation with well‐dated regional volcanic events through direct recognition of interlayered volcanic deposits as well as by inference from flexural loading of pre‐existing strata. The combined age model implies relatively rapid (1 m/2–5 ky) accumulation of sediment punctuated by hiatuses, which account for approximately 50% of the record. Three of the longer hiatuses coincide with basin‐wide seismic reflectors and, along with two thick volcanic intervals, they subdivide the succession into seven chronostratigraphic intervals with characteristic facies: 1. The base of the cored succession (1275–1220 mbsf) comprises middle Miocene volcaniclastic sandstone dated at approx 13.5 Ma by several reworked volcanic clasts; 2. A late-Miocene sub-polar orbitally controlled glacial–interglacial succession (1220–760 mbsf) bounded by two unconformities correlated with basin‐wide reflectors associated with early development of the terror rift; 3. A late Miocene volcanigenic succession (760–596 mbsf) terminating with a ~1 my hiatus at 596.35 mbsf which spans the Miocene–Pliocene boundary and is not recognised in regional seismic data; 4. An early Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession (590–440 mbsf), separated from; 5. A late Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession (440–150 mbsf) by a 750 ky unconformity interpreted to represent a major sequence boundary at other locations; 6. An early Pleistocene interbedded volcanic, diamictite and diatomite succession (150–80 mbsf), and; 7. A late Pleistocene glacigene succession (80–0 mbsf) comprising diamictite dominated sedimentary cycles deposited in a polar environment.

This paper accounts for a new finding of High Pressure–Low Temperature (HP-LT) metamorphism documented in continental-derived rocks exposed in the central part of the Middle Tuscan Range, representing the easternmost location, in the Tyrrhenian Region, where blueschist facies metamorphism has been documented. It describes the development mechanism of Mg–carpholite bearing quartz veins in the framework of the deformational events described for the inner Northern Apennines. The HP-LT peak metamorphism can be estimated in P ≥ 1.1 GPa and T = 370°–420 °C as supported by the mineralogical assemblage consisting of quartz–muscovite–chloritoid–pyrophylite–hematite ± chlorite ± paragonite ± Ti-oxides, documented in the aluminous metasediments (pelites and quartzose sandstones) of the Triassic Verrucano succession. This paragenesis defines the S 1 schistosity, an axial planar tectonic foliation associated to map- and mesoscale isoclinals folds (F 1 ); S 1 schistosity is a composite foliation resulted from a non-coaxial progressive deformation associated to the DE 1 collisional event (Late Oligocene–Early Miocene). Mg–carpholite bearing quartz veins developed as tension gashes in en-echelon arrays within brittle/ductile shear zones. The development of quartz veins was guaranteed by the high volumes of Si-rich fluids produced by the dynamic recrystallization process on the siliciclastic rocks.

This paper deals with a structural and petrographic study carried out on key outcrops belonging to the Tuscan Nappe exposed in the Colline Metallifere region (Montieri-Poggio Prugnoli). Here, the Tuscan Nappe was affected by polyphase deformation characterised by superposed folding events (F1, F2 and F3) and related tectonic foliations (S1 and S2) in agreement with the structural setting described for the Tuscan Nappe exposed both in other places of southern Tuscany, and in the Alpi Apuane region. The development of F1 folds was accompanied by metamorphism which produced a sin-kinematic mineralogical assemblage developed on the S1 tectonic foliation. This paragenesis, consisting of calcite + quartz ± muscovite ± Fe- and Ti-oxides, is indicative for a temperature of about 200-300°C according to the T values estimated for the F1 folding event documented for the Tuscan Nappe of the Apuan Alps, suggesting a very low grade metamorphism which affected the Tuscan Nappe during its stacking in the Northern Apennines collisional belt

The conversion of volcanic glass to secondary alteration products is one of the most common mineralogical transformations during low-temperature hydrothermal alteration of submarine basalts. To better understand the mechanism and kinetics of this transformation, porphyritic and formerly glassy trachybasalt, recovered from Conical Seamount, Papua New Guinea, was studied in detail. Low-temperature interaction of trachybasalt with hydrothermal fluids at this submerged volcano occurred in response to the formation of submarine epithermal-style gold mineralization. Alteration of the coherent volcanic rocks is heterogeneous with pronounced differences in alteration intensity occurring between igneous minerals and the surrounding glassy groundmass. In comparison to the volcanic glass, the crystalline phases were less prone to hydrothermal alteration with the alteration susceptibility decreasing from clinopyroxene through biotite to feldspar. Low-temperature alteration of clinopyroxene resulted in the formation of abundant saponite-like smectite with no topotactic relationship being observed between the two phases. In contrast, the conversion of biotite to smectite involved structural inheritance as the orientation of common structural blocks was maintained during alteration. Transmission and analytical electron microscopy revealed that pervasive alteration of interstitial glass in the groundmass of the trachybasalt resulted in the formation of montmorillonite- and saponite-like smectite whereby smectite composition is strongly influenced by the glass chemistry. The occurrence of poorly crystalline domains with a 0.3 to 0.4 nm layer spacing in the altered interstitial glass suggests that the transformation of glass to smectite involved the formation of a transitional alteration product. Comparison with the results of previous studies highlights the fact that the glass-to-smectite transformation can proceed through more than one reaction pathway. Reaction style and reaction progress are controlled by kinetic factors such as the mode of fluid transport triggering alteration in the low-temperature hydrothermal environment. Alteration of the trachybasalt at Conical Seamount is inferred to have taken place at a comparably low fluid-rock ratio as the low permeability and the absence of primary fractures and joints restricted fluid circulation through the coherent volcanic rocks.

The cryosphere in the McMurdo Sound region has undergone significant modifications during the last 1 Ma. Consequently, the sedimentary sequences underlying the modern McMurdo Ice-Shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, grounding line position and main ice-stream flow directions during glacial and interglacial periods. The present study aims to investigate the clay and heavy mineral assemblages of the late Pleistocene subglacial and glaciomarine sediments recovered during the ANDRILL-McMurdo Ice Shelf Project in Windless Bight (South of Ross Island). The analyses show that the sediments are a mix of detritus from the McMurdo Volcanic Group (MVG) and the Transantarctic Mountains (TAM) from the south and west. MVG-derived minerals prevail with respect to TAM-derived minerals. The down-core mineralogical variations are determined by changes in the source rocks and the sedimentary processes. Sediments at the drill site are nourished by ice coming from the South which delivered rocks from the McMurdo Volcanic region; the enrichment of a TAM component in massive diamictites testifies that the ice sheet collected debris from the Transantarctic Mountains. When open marine conditions prevailed, only sediments from a local source (i.e. McMurdo volcanics) were deposited.

Sea floor sediments beneath the McMurdo/Ross Ice Shelf in a 900-m-deep depression behind Ross Island have been cored through access holes at two sites. At Site 1, 31 cm of mud and lesser sand, deposited over the last 22 ka, overlies a 30-cm-thick diamictite of the Last Glacial Maximum. At Site 2, the entire core is mud deposited over the last 12 ka. Analyses of very fine sand-sized, heavy minerals and geochemical analyses of the sand and silt fractions have been carried out on samples from both sites to track variations in sediment provenance through the Late Quaternary. The heavy minerals were identified by optical and electron scanning microscope (SEM-EDAX) analysis. Major and trace elements were determined on fused glass discs by X-ray fluorescence (XRF) spectrometry. Heavy mineral assemblages have high concentrations of pyroxenes (titanoaugite, augite, pigeonite, low-Ca augite and enstatite), olivines and glass grains. Amphiboles (Mg-hornblende, actinolite and kearsutite), oxides (titanite and titanomagnetite) and stable minerals (epidote, garnet, and apatite) are present in minor amounts. Olivine, titanoaugite and glass dominate the heavy mineral assemblages both in upper part of core 1 and in all of core 2. In the diamictite, an increase of augite, pigeonite, low-Ca augite, hornblende and stable minerals are observed. The sediment geochemistry is linked to their mineralogical composition both in the sand and in the silt fractions. K and Rb trends probably represent variations in alkali feldspar and/or mica content. The variation of Si/Al ratio is due to sialic minerals and/or to quartz content variation. Mg, Ca, Ti, Sr are probably comprised in femic minerals. The sets of analyses show that the sediments are a mix of local McMurdo Volcanic Group (MVG) rocks and Transantarctic Mountains (TAM) source rocks to the south and west. The diamicton was a strong TAM provenance, suggesting that the main ice streams drained into the Ross Sea from the West at least prior to 18 ky and later than 25 ky. The overlying mud is dominated by a MVG signal, sediments in the two sampled sites derive from basal melting of the ice sheet which entrapped debris from MVG cropping out to the South of the Ross Embayment. Small quantities of minerals from the TAM can be supplied by marine currents inflowing under the shelf from NW.

The relationship between the Ricker Hills Tillite (RHT), which represents the northernmost outcrop of lithified continental glacial deposits in Victoria Land, is discussed with respect to the glacial landscape assemblage of the Ricker Hills, a nunatak at the internal border of the Transantarctic Mountains. A warm-based ice sheet deposited the tillite and induced syn- to post-depositional glacial deformation under wet conditions both of the tillite and of the bedrock. The thickness of the ice sheet on the nunatak is estimated to have been 600 m, at most. The area had been deeply eroded before deposition of the RHT as documented by the low elevation of tillite outcrops located in overdeepened depressions of the nunatak. Micropaleontological analysis evidences only the presence of Permian to Jurassic palynomorphs. X-ray diffraction and SEM–EDS analyses of clay minerals in the RHT indicate continental chemical weathering under wet conditions after the RHT deposition. As documented by clay mineral assemblage variation in CRP drillholes, the progressive cooling of the Antarctic continent allowed chemical weathering in “warm” conditions until the Late Oligocene period in southern Victoria Land, leading to a chronological constrain for RHT deposition. Conservatively estimating the sea level to have been between the tillite outcrops and the erosional trimline limiting horns in the Ricker Hills, at the time of RHT deposition, we suggest that the maximum uplift of the area would not have exceeded 900–1500 m since at least Late Oligocene.

Variably altered dacite from the PACMANUS vent field in the eastern Manus back-arc basin, Papua New Guinea, was studied to determine the textural and mineralogical characteristics of hydrothermal alteration taking place in the immediate subsurface of this modern seafloor hydrothermal system. Detailed textural investigations show that fluid flow through the glassy dacite has been strongly controlled by the primary volcanic textures. Quench fractures and networks of interconnected perlitic cracks linking vesicles provided pathways for hydrothermal fluids flowing up to the seafloor. Hydrothermal alteration along these pathways resulted in the formation of pseudoclastic textures. Textural evidence suggests that alteration of the glassy dacite has not been sustained. The samples have been affected by incipient hydrothermal alteration that is typically not preserved in ancient volcanic-rock-hosted massive sulfide deposits. Interaction of the glassy dacite with hydrothermal fluids primarily resulted in the conversion of volcanic glass to dioctahedral smectite. Only minor amounts of trioctahedral smectite were formed. Destruction of the volcanic glass and the formation of smectite caused pronounced changes in the chemistry of the dacite samples, in particular a decrease in the SiO2 whole-rock content and the Na2O/K2O ratio. The two alkali elements behaved differently during hydrothermal alteration due to preferential incorporation of K into the interlayer position of the newly formed dioctahedral smectite. Smectite formation occurred under rock-dominated conditions although the addition of Mg was required to form trioctahedral smectite from the silicic volcanic glass. Primary plagioclase was resistant to hydrothermal alteration highlighting the fact that the destruction of volcanic glass and feldspar are not necessarily contemporaneous in massive sulfide forming hydrothermal systems. Incipient alteration of the glassy dacite close to the seafloor occurred at temperatures below 150 °C in an environment that allowed the development of steep temperature gradients. Comparison of the new data to the findings of deep drilling during ODP Leg 193 suggests that the smectite-rich alteration in the immediate subsurface of the PACMANUS hydrothermal vent field represents the low-temperature equivalent of illite- and chlorite-rich alteration associations forming in the upflow zones of the hydrothermal fluids in the deeper portion of the volcanic sequence.

The upper continental slope of the Storfjorden-Kveithola Trough Mouth Fans (NW Barents Sea) contains a several m-thick late Pleistocene sequence of plumites composed of laminated mud interbedded with sand/silt layers. Radiocarbon ages revealed that deposition occurred during about 130 years at a very high sedimentation rate of 3.4 cm a−1, at about 7 km from the present shelf break. Palaeomagnetic and rock magnetic analyses confirm the existence of a prominent, short-living sedimentary event. The plumites appear laterally continuous and were correlated with the sedimentary sequences described west of Svalbard and neighboring glacial depositional systems representing a major event at regional scale appointed to correspond to the deep-sea sedimentary record of Meltwater Pulse-1a. We also present new sedimentological and geochemical insights, and multi-beam data adding information on the palaeoenvironmental characteristics during MWP-1a and ice sheet decay in the NW Barents Sea.

Alkaptonuria (AKU) is a rare genetic disease that affects the entire joint. Current standard of treatment is palliative and little is known about AKU physiopathology. Chondroptosis, a peculiar type of cell death in cartilage, has been so far reported to occur in osteoarthritis, a rheumatic disease that shares some features with AKU. In the present work, we wanted to assess if chondroptosis might also occur in AKU. Electron microscopy was used to detect the morphological changes of chondrocytes in damaged cartilage distinguishing apoptosis from its variant termed chondroptosis. We adopted histological observation together with Scanning Electron Microscopy and Transmission Electron Microscopy to evaluate morphological cell changes in AKU chondrocytes. Lipid peroxidation in AKU cartilage was detected by fluorescence microscopy. Using the above‐mentioned techniques, we performed a morphological analysis and assessed that AKU chondrocytes undergo phenotypic changes and lipid oxidation, resulting in a progressive loss of articular cartilage structure and function, showing typical features of chondroptosis. To the best of our knowledge, AKU is the second chronic pathology, following osteoarthritis, where chondroptosis has been documented. Our results indicate that Golgi complex plays an important role in the apoptotic process of AKU chondrocytes and suggest a contribution of chondroptosis in AKU pathogenesis. These findings also confirm a similarity between osteoarthritis and AKU. J. Cell. Physiol. 230: 1148–1157, 2015. © 2014 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

article i nfo Article history: An integrated system, based on Inductively Coupled Plasma-Sector Field Mass Spectrometry (ICP-SFMS) and Inductively Coupled Plasma-Atomic Emission Spectrophotometry (ICP-AES) techniques, was optimised for the geochemical characterisation of soils and marine sediments. Sample mineralization was carried out with HF, HNO3 and HClO4. Operative blanks were at least two orders of magnitude lower than the lowest concentration measured in real samples. For ICP-SFMS, the detection power of the method in high resolution mode was sufficientforanaccuratequantificationofmetals,yetavoidingREEs'(RareEarthElements)isobaricinterferences. Once tested the accuracy on six certified materials, the methods were applied to the analysis of 39 major and trace metals on the top 90 m of sediments from the ANDRILL AND-1B core, covering the last million years. Stratigraphies of REEs and of normalised markers from this core clearly highlight a discontinuity at about 660,000 years before present. This pattern is well shown by the results of a PMF (Positive Matrix Factorization) statistical analysis, revealing two different sources for the sedimentary material, whose relative contribution changed around that time. Such a result is consistent with previous studies and confirms the net change in the provenance of glacial fluxes in the McMurdo region (Ross Ice Shelf, Antarctica) in the last million years.

Tuscan black glosses on ancient pottery have been characterized using high resolution techniques. Ancient (4 th -1 st century B.C.) pottery from southern and northern Tuscany is coated with black glosses which show different visual appearance. Misfired red-black, matt, shining, metallic, and bluish black glosses have been studied with X-ray diffraction, scanning and transmission electron microscopes to establish their mineralogical, textural and chemical characteristics. The glosses are chemically homogeneous and they are all comprised of a Si-Al rich, amorphous matrix where nanometer-sized crystals of different nature are embedded. Crystals occur both as euhedral grains and as grains with a high aspect ratio. The misfired gloss contains hematite as the only mineral phase, both in the red and black portion of the coating. The matt black gloss contains mainly homogeneous hercynite crystals. In a small portion of the gloss, few magnetite crystals have been detected. However, no gradual variations either along or perpendicular to the gloss layer have been observed. Magnetite is the only mineral phase occurring in the shining metallic black gloss. The bluish-black gloss shows spinel grains with variable characteristics. Most grains are comprised of homogeneous hercynite with magnetite in solid solution. Other crystals are zoned: the core has hercynitic composition with relatively high content in magnetite, ulvospinel, and spinel s.s. in solid solution; Al and Mg increases towards the rim. These results clearly indicate that microanalytical techniques provide accurate mineralogical and microtextural characterizations at the nanometer scale. It has been shown that visually different glosses have different mineralogy which are mainly caused by different oxygen fugacities (f O2 ) during firing.

Metastable intermediate Na–K mica represents a product of hydrothermal alteration in volcanic rocks from the alteration halo of the Waterloo massive sulfide deposit, Australia. The XRD pattern of this solid solution between paragonite and muscovite is characterized by a rational series of basal reflections with d values intermediate between the end members. Transmission electron microscopy revealed that the intermediate Na–K mica forms thick stacks that belong to a two-layer polytype. Na-rich intermediate Na–K mica typically occurs together with paragonite whereas K-rich intermediate Na–K mica is intergrown with muscovite. The intermediate Na–K mica is interpreted to have formed as a result of the incomplete transformation of K-rich mica to Na-rich mica through dissolution and recrystallization processes driven by compositional changes of the hydrothermal fluids interacting with the volcanic rocks. Alteration must have proceeded under non-equilibrium conditions because the composition of the solid solution falls into the miscibility gap separating paragonite and muscovite.

The Wilkes Land continental rise is characterised by mounds and channels with approximately a north–south elongation, perpendicular to the margin. Proximal mound relief is up to 1000 m, decreasing to about 300 m in the central part. During the geophysical and geological survey conducted on in February–March 2000 by the joint Italian and Australian WEGA Project, onboard R/V Tangaroa, 11 piston cores were collected along two transects crossing the channel-mound system. All cores were logged for physical (magnetic susceptibility and density) and acoustic properties (P-wave velocity). Split cores were X-rayed and samples were analysed for clay mineral assemblages, chemical and micropaleontological (diatoms, foraminifera and nannofossils) content. Glacial and interglacial intervals have been recognised in the sediment cores. The interglacial facies consists of massive mud, distinguished by: (a) bioturbated massive mud occasionally with fine-grained ice-rafted debris (IRD), and (b) structureless massive mud with abundant fine to coarse-grained IRD, containing well-preserved open-ocean diatoms. The glacial facies is represented by laminated mud with planar and/or cross laminations, with occasional isolated dropstones, and rare, poorly preserved, sea-ice diatoms. The sharp boundary, characterizing the limit between massive to laminated facies, is interpreted to indicate a fast glacial onset. In contrast, the smooth passage presents from laminated to massive sediments, indicates a gradual glacial waning. Recent down-slope gravity flows have been identified in a turbidite, a normally graded coarse-grained sand, recovered in the thalweg of Jussie Canyon, and probably also in the massive debris facies from the steep side of Mound A. The massive debris is characterised by structureless and unsorted gravel and pebbles within a muddy matrix. Clay mineral assemblages and grain lithologies indicate a hinterland Wilkes Basin and continental shelf provenance for the terrigenous fraction.

Microanalytical data on Plio-Pleistocene sediments from a Salton Sea Geothermal Field well define the evolution of textures and mineral assemblages from sediment to metamorphic rock in an open hydrothermal system.At shallow depths detrital grains occur within a fine-grained matrix of I-S and illite. As depth and temperature increase, grains lose their detrital characteristics; they subsequently form a continuous intergrown array of irregular domains, with phyllosilicates occupying the progressively decreasing pore space.Illite and chlorite are authigenic phyllosilicates down to 2500 m, where biotite occurs. Authigenic phyllosilicates occur as subhedral crystals (200 –600 Å thick). Alkali feldspar has end-member compositions, implying exchange of alkalis with convected fluids. Changes in texture imply dissolution of detrital phases and neocrystallization of authigenic phyllosilicates directly from pore fluids. Changes with depth are not time-dependent for phyllosilicates: they formed simultaneously at all depths as a result of a single hydrothermal event in an open system.

Background. Alkaptonuria, a rare autosomal recessive metabolic disorder caused by deficiency in homogentisate 1,2-dioxygenase activity, leads to accumulation of oxidised homogentisic acid in cartilage and collagenous structures present in all organs and tissues, especially joints and heart, causing a pigmentation called ochronosis. A secondary amyloidosis is associated with AKU. Here we report a study of an aortic valve from an AKU patient.Results. Congo Red birefringence, Th-T fluorescence, and biochemical assays demonstrated the presence of SAA-amyloid deposits in AKU stenotic aortic valve. Light and electron microscopy assessed the colocalization of ochronotic pigment and SAA-amyloid, the presence of calcified areas in the valve. Immunofluorescence detected lipid peroxidation of the tissue and lymphocyte/macrophage infiltration causing inflammation. High SAA plasma levels and proinflammatory cytokines levels comparable to those from rheumatoid arthritis patients were found in AKU patient.Conclusions. SAA-amyloidosis was present in the aortic valve from an AKU patient and colocalized with ochronotic pigment as well as with tissue calcification, lipid oxidation, macrophages infiltration, cell death, and tissue degeneration. A localHGDexpression in human cardiac tissue has also been ascertained suggesting a consequent local production of ochronotic pigment in AKU heart.

K–Ar ages from white mica are commonly interpreted to record cooling below a certain temperature with the implicit assumption that all the requirements of the volume diffusion theory are fulfilled. Nevertheless, studies on metamorphic white micas have highlighted discrepancies with previously inferred closure temperatures and have evidenced a close link between petrology and argon isotope age records. This study uses the in situ 40Ar–39Ar laserprobe method in conjunction with scanning electron microscopy, electron microprobe and transmission electron microscopy (TEM) techniques to examine the relations between argon isotope records and microtextural, microchemical and microstructural variations in white mica. Gneisses and micaschists belonging to three different tectono-metamorphic complexes of the Lanterman Range (Antarctica) contain multiple generations of potassic white micas and are well-suited to investigate the relation between petrology and argon dating. Texturally resolvable white mica generations show microchemical and microstructural (TEM scale) variations that suggest development under different P–T deformation regimes, ranging from an eclogite facies stage down to low greenschist facies conditions. In situ 40Ar–39Ar laserprobe analyses on white mica samples from the three complexes reveal a complex intragrain and intergrain spatial distribution of argon ages which is closely linked to microtextural, microchemical and microstructural variations: texturally, compositionally and microstructurally older generations yield older ages whereas the younger ones yield younger ages. Results show that in the absence of re-crystallisation, white mica preserves argon isotope records pertaining to the high-pressure stage which survived amphibolite retrogression at temperatures of 550–650°C. The texture, petrology and isotope record of white micas in the studied samples preserve a nearly continuous record of P, T and deformation history within the same orogenic cycle.

A late Quaternary, current-lain sediment drift deposit over 30 m in thickness has been discovered on the continental shelf of East Antarctica in an 850 m deep glacial trough off George Vth Land. Radiocarbon dating indicates that a period of rapid deposition on the drift (averaging 290 cm/kyr) occurred in the mid-Holocene, between about 3000 and 5000 yr before present. Slower rates of around 10 cm/kyr, during the past 0-3000 yr and from 5000 to about 13000 yr BP, coincides with deposition of bioturbated, ice-rafted debris (IRD) rich, sandy mud under an energetic bottom current regime. In contrast, the mid-Holocene (3000-5000 yr BP) sediments are fine-grained, laminated to cross-laminated with minimal IRD content, and are contemporaneous with a period of warmer marine conditions with less sea ice production. This pattern suggests that bottom currents were weaker than present day in the mid-Holocene, and that the rate of dense bottom water production was reduced at that time. This scenario is consistent with the hypothesis of non-steady state rates of Antarctic bottom water production through the Holocene as recently proposed by Broecker and his colleagues.

The evolution of texture, structure and chemical composition of chloritic clays in coeval pairs of metabasites and metapelites of a prograde sequence from the Bukk Mountains has been investigated using electron microscopy techniques. Samples are from the Bukkium (innermost Western Carpathians, Hungary) that underwent Alpine metamorphism, ranging from late diagenesis to epizone for pelites and from prehnite-pumpellyite to greenschist facies for the metabasites. Although bulk-rock compositions, textures and primary minerals are different, chlorite evolved at similar rates in coeval metabasites and metasediments, but along different paths. The principal similarities in the prograde sequence are a decrease in the percentage of interstratified material in both dioctahedral and trioctahedral phyllosilicates and increase in thicknesses of chlorite and illite crystallites. The principal difference is in the type of interstratification in chlorite, with berthierine in metapelites, and smectite (saponite) in metabasites, although smectitic mixed layers also occur in the former. The evolution of trioctahedral phyllosilicates is marked by a decrease in the number of mineral species with increasing grade, chlorite, sensu stricto, being the only trioctahedral mineral at higher grades. This is consistent with the trend in reaction progress where both metastable systems (metabasites and metapelites) tend toward the same end-member, thermodynamically stable chlorite, as well as texture (crystal size), and where all intermediate states are metastable, and determined by the Ostwald step rule.

Marbles from different geometrical and structural positions within the Alpi Apuane metamorphic complex show a large variability in microfabric types as indicated by microstructure, c-axis orientation and temperature analysis. Statically recrystallized samples showing a granoblastic microstructure and polygonal grain boundaries are characterized by a grain size variation from east to west from 80–100 μm to 250–300 μm. This is correlated with an equilibration calcite-dolomite temperature from 360–380°C to 420°–430°C. Two kinds of dynamically recrystallized microstructures have been investigated: a first one exhibiting coarse grains (150–200 μm) with lobate grain boundaries and a strong shape preferred orientation and a second one characterized by a smaller grain size (40–50 μm) and predominantly straight grain boundaries. These microstructural types, associated with localized post-thermal peak shear zones and meter- to kilometer-scale folds, are interpreted as related to high strain and high temperature crystal plastic deformation mechanisms (dislocation creep) associated with predominant grain boundary migration (type-B1) or subgrain-rotation recrystallization (type-B2). These differences in dynamically recrystallized microstructures are related to equilibration temperatures higher in type-B1 (390°C) than in type-B2 (370–340°C). We have been able to relate the development of the different microfabric types to the successive stages of deformation of the Alpi Apuane metamorphic complex.

An XRD-TEM study was carried out on low-grade metapelites (Transantarctic Mountains) to determine the cause of apparent inconsistences in grade as determined by IC and independent geologic relations. The illite crystallinity (IC) data indicate that the three units investigated (BT, RBT, MS) were affected by very low- (IC = 0.24°Δ2θ in BT) to low-grade metamorphism (0.19°Δ2θ in MS). In all three samples, mica crystals are of a size typical of the epizone, but the mean size increases from BT to RBT and MS, due to the increasing strain features from BT to MS. These results indicate that strain-induced reduction in crystal size was retained in BT samples (with anomalously high IC values). Microtextures in RBT and MS (with smaller IC) samples suggest a recovery of sub-grain boundaries. A decrease in crystal size may occur with increasing grade where strain rates are high relative to the rate of recrystallization.

A study of the metamorphic and tectonic evolution of the Massa Unit in the Alpi Apuane Metamorphic Complex shows that this unit suffered relatively high-pressure conditions (peak higher than 0.8 GPa) and was exhumed during a multiphase history. The first stage of exhumation occurred during Tertiary continental collision between Adria and Sardinia/Corsica and was associated with the thrusting of the more deeply buried chloritoid + kyanite-bearing Massa Unit on top of the less deeply buried chloritoid + pyrophyllite-bearing Apuane Unit. The subsequent stages of exhumation were shared by the two metamorphic units and were coeval with the beginning of crustal extension related to the opening of the Tyrrhenian Sea. Copyright © 2000 John Wiley & Sons, Ltd.

Lucchi, Renata G. ... et al.-- 18 pages, 9 figures, 2 tables, The depositional history of the Storfjorden and Kveithola trough-mouth fans (TMFs) in the northwestern Barents Sea has been investigated within two coordinated Spanish and Italian projects in the framework of the International Polar Year (IPY) Activity 367, NICE STREAMS. The investigation has been conducted using a multidisciplinary approach to the study of sediment cores positioned on high-resolution multibeam bathymetry and TOPAS/CHIRP sub-bottom profiles.Core correlation and the age model were based on 27 AMS 14C samples, rock magnetic parameters, lithofacies sequences, and the presence of marker beds including two oxidized layers marking the post Last Glacial Maximum (LGM) inception of deglaciation (OX-2) and the Younger Dryas cold climatic event (OX-1).Sediment facies analysis allowed the distinction of a number of depositional processes whose onset appears closely related to ice stream dynamics and oceanographic patterns in response to climate change. The glacigenic diamicton with low water content, high density, and high shear strength, deposited during glacial maxima, indicates ice streams grounded at the shelf edge. Massive release of IRD occurred at the inception of deglaciation in response to increased calving rates with possible outer ice streams lift off and collapse. The presence of a several-meter-thick sequence of interlaminated sediments deposited by subglacial outbursts of turbid meltwater (plumites) indicates rapid ice streams' melting and retreat. Crudely-layered and heavily-bioturbated sediments were deposited by contour currents under climatic/environmental conditions favorable to bioproductivity.The extreme sedimentation rate of 3.4cma-1 calculated for the plumites from the upper-slope area indicates a massive, nearly instantaneous (less than 150years), terrigenous input corresponding to an outstanding meltwater event. We propose these interlaminated sediments to represent the high-latitude marine record of MeltWater Pulse 1a (MWP-1a). Different bathymetric and oceanographic conditions controlled locally the mode of glacial retreat, resulting in different thickness of plumites on the upper continental slope of the Storfjorden and Kveithola TMFs. It is possible that the southern part of Storfjorden TMF received additional sediments from the deglaciation of the neighboring Kveithola ice stream. © 2013, This study was supported by the Spanish IPY projects SVAIS (POL2006-07390/CGL) and IPY-NICE STREAMS (CTM2009-06370-E/ANT), the Spanish project DEGLABAR (CTM2010-17386), and the Italian projects OGS-EGLACOM, and PNRA-MELTSTORM

We have examined the nature and origin of smectites in glaciomarine sediments of the AND-2A drill core (McMurdo Sound, Antarctica) by means of X-ray diffraction (XRD) analyses on the clay fraction, field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM) observations and SEM-EDS microanalyses on smectite particles. Relying on the smectite variation throughout the drill core it was possible to split the sequence into three units. Smectites throughout the core are either detrital or authigenic. Detrital smectites are close to montmorillonite-beidellite in composition while newly-formed smectites frequently have higher Fe-Mg contents and intermediate compositions between the saponite and nontronite field, with lower amounts in the montmorillonite-beidellite field. In the upper sedimentary sections (Unit I, and Unit II, 36-440 mbsf, 0.7-16.5 Ma) smectites are interpreted to be predominantly detrital, whereas in the lower portion of the core (Unit III, 440-1123.20 mbsf, 16.5-20.2 Ma) authigenic smectites are the most common feature. The predominance of mica, the abundance of chlorite, and the nature of smectites in the upper units indicate physical weathering under cold and dry climate, and a dominant provenance for the clay minerals from the Transantarctic Mountains. Smectites in the lower unit are considered mostly authigenic and they are most likely to be the result of early diagenetic processes, being formed from the alteration of volcanic material (glass, pyroxenes and feldspars) and/or through precipitation from fluids of a possible hydrothermal origin. Our survey attests to the importance of discriminating between a detrital and authigenic nature of smectites as the occurrence of authigenic clay minerals in ancient sedimentary successions might lead to incorrect palaeoclimatic interpretations, since they can be affected by diagenetic processes, thus obliterating the climatic signal.

The Sienese “archaic” majolica coated with enamels and glazes was produced in many workshops within the city from the thirteenth to the end of the sixteenth century AD. This type of ceramics has been the subject of few, but detailed archaeometric studies (Grassi et al. 2003; Fortina et al. 2005). Fortina et al. (2005) reconstructed the production technology of ceramics recovered from the Convent of the Carmine (Siena) according to petrographic and mineralogical evidence. Optical microscopy, X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and Raman spectroscopy helped reveal the texture and the mineralogical compositions of the ceramic bodies and the coatings, both glaze and enamel. However, it was not possible to properly characterise very fine-grained, newly-formed phases with these micron-scale techniques. Nanometric-size mineral phases grown in artefacts can be recognised by high-resolution techniques, such as analytical-electron, transmission-electron microscopy (AEM–TEM), as it has been done in few recent studies. The characterisation of reaction processes and mineral phases at a nanometric scale led to the determination of technological processes (Mata et al. 2002), mineralogy of coatings in Renaissance pottery (Viti et al. 2003) and of Tuscan black glosses (Giorgetti et al. 2004).

Rock varnishes on subaerially exposed surfaces of magmatic rocks in northern Victoria Land (Antarctica) have been analyzed using XRD, SEM-EDS and TEM-AEM techniques. The varnishes are tens of micron in thickness and consist of laminae with different chemical compositions. They always show sharp contacts with the underlying rocks. X-ray microanalysis enables two components to be recognized from their chemical compositions: a component rich in Si with minor Al, Fe, and Mg, and a S and Fe-rich component with minor Al, K, and P. Results of XRD and TEM work reveal that the Si-rich component is made of amorphous material containing few nanometer-thick smectite crystals, most of which have formed in situ . The S-rich component forms subrounded areas and laminae oriented parallel to the outer surface of the rock substrate and may be amorphous or crystalline. The crystals are sulphates of the alunite-jarosite series. The varnish is inferred to have formed by accretion onto the external surface of the rock substrate of airborne dust, followed by remobilization of some constituent and subsequent crystallization of clays and sulphates. The sulphur may have been derived from marine spray and/or fallout of active volcanoes.

The occurrences of natural coexisting feldspars including hyalophane and also celsian delineate two-, three- and possibly four-phase fields in the system BaAl2Si2O8—CaAl2Si2O8—NaAlSi3O8—KAlSi3O8. Hyalophane occurs with albite and microcline in a very low grade (anchizonal to epizonal) metasedimentary association from the Uppony Mountains, Hungary, and in Grenville marbles from Ontario. Analyses show very little Ba in albite and only limited Na in hyalophane. One marble from the garnet zone has albite (Ab95–98), oligoclase (An17Sl3Ab80), hyalophane (Cn65Sl3An2Ab9Or24) and celsian (Cn92Sl3An1Ab2Or2). The albite and oligoclase are complexly intergrown and may indicate unmixing during cooling. A marble in the sillimanite zone contains albite (Ab95–98Or2–3), oligoclase (An17An2Sl3Ab33Or24), hyalophane (Cn65Sl3An2Ab9Or24), and an inclusion of celsian (Cn67An1Sl2Ab2Or91) in an albite. Sanidine from the Peshtigo monzonite in Wisconsin unmixed to a symplectic perthite with barian microcline (Cn8–11An2Ab8–13Or75–80) and oligoclase (CnlAn18Ab79Or2). The former compositions of the ternary igneous feldspars (Cn3An9Ab46Or42, Cn1An18Ab69Or12) were obtained by reintegration. The Na content of hyalophane equilibrated with albite is correlated with metamorphic grade. Hyalophane has 5 ± 2 mol % Ab in very low-grade associations, 10 ± 3 mol % Ab in the greenschist facies, 16 ± 2 mol % Ab in the low to middle amphibolite facies, and 30 mol % Ab in the upper amphibolite to granulite facies even when not buffered with albite. The limited Na content of celsian equilibrated with albite in the greenschist facies is in striking disagreement with the narrow solvi obtained from unreversed experiments on the join BaAl2Si2O86-NaAlSi3O8. Up to 8 four-feldspar and 24 three-feldspar assemblages may be stable in the system BaAl2Si2O8-CaAl2Si2O8-NaAlSi3O8-KAlSi3O8. In contrast, the repeatedly observed and variably located discontinuities within zoned hyalophane grains may represent changes in the environment during mineral growth rather than internal miscibility gaps. Given its miscibility gaps with microcline and celsian, the name hyalophane is justified for intermediate feldspars near the Cn-Or join.

Dacitic lava recovered from the immediate subsurface of the submarine PACMANUS hydrothermal vent field exhibits variable degrees of hydrothermal alteration resulting from the interaction of the glassy volcanic rocks with mineralizing hydrothermal fluids at relatively low temperatures. Transmission electron microscopic (TEM) investigations revealed that the felsic volcanic glass transformed to nm-thick smectitic flakes of the montmorillonite-beidellite series via a dissolution and reprecipitation mechanism. The process of smectite formation did not proceed through X-ray amorphous or poorly crystalline transitional phases. Alteration of the glass was found to be most pronounced adjacent to perlitic cracks and vesicles that form an interconnected network focusing fluid flow. Glass dissolution adjacent to these fluid pathways resulted in a characteristic alteration texture at the nm scale; the intensely altered groundmass contains round cavities that are partially coated or filled by smectitic flakes. The Mg content of the smectite broadly increases towards the fluid pathways. Smectitic flakes with compositions corresponding to saponite occur in the intensely altered groundmass adjacent to perlitic cracks. In addition, anatase, apatite and rare kaolinite were formed during the alteration of the volcanic glass. Primary minerals including plagioclase show only minor textural evidence of alteration. However, some primary plagioclase laths show X-ray amorphous rims depleted in Na, Ca and Al. The TEM investigations of the dacitic lava samples from the PACMANUS vent field demonstrate that volcanic glass has a higher susceptibility to hydrothermal alteration at low temperatures than most associated primary phases. The findings of the study suggest that the interaction between the volcanic rock and the hydrothermal fluids proceeded under open-system conditions leading to a mobilization of alkali elements and a redistribution of Ti at the nm scale. The Mg required for the formation of trioctahedral smectite was supplied by the hydrothermal fluids.

Pliocene–Quaternary marine sediments from Wilkes Land continental rise were investigated using clay mineral analysis and quartz grain surface texture observations. The studied piston cores were collected during a geophysical and geological survey in the framework of the Italian and Australian WEGA Project. The cores were collected along two transects crossing the channel-mound system that characterizes the Wilkes Land continental rise. Massive and laminated facies were recognized in these sedimentary sequences. The clay mineral assemblages are dominated by illite. Smectite and chlorite occur in intermediate amounts, whereas kaolinite is scarce. Illite derives from the hinterland of the Mertz and Ninnis glaciers. Smectite and kaolinite derive from the Ross Sea area and they are transported by westward marine bottom currents. Chlorite is derived both from the adjacent continent and from the Victoria Land. Different concentrations of individual clay minerals in the massive and laminated facies are controlled by the interplay between different source areas and the main sedimentary processes. Glacial and eolian quartz grains prevail in the massive units indicating short transportation and rapid deposition from melting ices, with no further significant transport action by marine currents. In the laminated facies the high amount of quartz grains affected by high-energy subaqueous transport features are related both to turbiditic processes and to bottom current transport.

Pelitic and basic rocks occurring within prograde sequences in Portugal, Spain and Hungary have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The minerals formed in typical prograde reactions define the general sequences, but smectite, chlorite-smectite (corrensite) and/or berthierine were found to have replaced chlorite, whereas kaolinite and mixed-layer illite-smectite replaced illite-muscovite. Alteration occurred under conditions normally associated with diagenesis, subsequent to regional metamorphism, and we therefore refer to such processes with the term "retrograde diagenesis". In the cases studied and in other cited examples, reactions occurred on a regional basis via pervasive fluids under open-system conditions inferred to be related to tectonic stress. The observed alterations could generally not be inferred from XRD data, although the presence of pure smectite in sediments other than bentonite is suggestive of retrograde relations, especially where other minerals are consistent with a higher grade of diagenesis. Retrograde diagenesis is readily observed through imaging of textures by TEM, however. Textural features show that retrograde reactions are more common than generally assumed, and that care should be used in interpreting geological events where appropriate textural relations are not seen.

12 páginas, 11 figuras, 3 tablas, Interleaved phyllosilicate grains (IPG) of various compositions are widespread in low-grade Verrucano metasediments of the northern Apennines (Italy). They are ellipsoidal or barrel shaped, up to 300–400 μm long and they are often kinked and folded; phyllosilicate packets occur as continuous lamellae or as wedge-shaped layers terminating inside the grain. Using electron microscopy techniques (SEM, TEM) six types of IPG have been distinguished on the basis of their mineralogical composition: (1) Chl+Ms ± Kln; (2) Chl+ Ms+Pg ± Kln; (3) Ms+Prl ± Pg; (4) Ms+Prl+Su; (5) Ms+Prl+Chl+Su; (6) Su+Ms. Types (1) and (2) are mainly composed of chlorite, with Ms and Pg as minor phases; Kln grows on Ms in highly weathered samples. Types (3), (4), (5), and (6) are composed of muscovite, with intergrown Prl, Chl, Su and new-formed muscovite. The IPG show all kinds of contacts: from coherent grain boundaries with parallel basal planes and along-layer transitions to low- and high-angle grain boundaries. The IPG formed on pristine minerals such as chlorite and muscovite. The transformations took place during the prograde and retrograde metamorphic path of the rocks: they were facilitated by deformation and they occurred in equilibrium with a fluid phase, which allowed cation diffusion. Prograde reactions [Chl = Ms (or Pg); Ms = Prl; Ms = Chl] involve dehydration and sometimes a decrease in volume, whereas retrograde reactions (Ms = Kln; Ms = Su) involve hydration and an increase in volume. These transformations do not simply occur through an interchange of cations, but often involve deep structural changes: transitions from one phyllosilicate to another generally proceed through dissolution-recrystallization reactions. In conclusion, Verrucano IPG represent microstructural sites which have not completely equilibrated with the whole rock and whose mineral assemblage depends on the original composition of the microstructural sites., Financial support was supplied by the Italian Ministry of University and Scientific and Technological Research grants (MURST to I.M.) and Research Projects nº PB92-0961 and PB92-0960 of the Spain Ministry of Education as well as Research Group 4065 of the Junta de Andalucia