症例は26歳の男性で，発熱と腰背部痛を主訴に外来を受診した．血清クレアチニン1.81 mg/dlと上昇がみられ，病歴の再聴取により，発症12時間前に無酸素運動を行っていることが判明した．運動後急性腎障害（acute renal failure with severe loin pain and patchy renal ischemia after anaerobic ...exercise：ALPE）を強く疑い，確定のための画像診断を考慮したが，気管支喘息の既往もあったことから造影CT（computed tomography）施行がためらわれた．代替検査としてMRI（magnetic resonance imaging）撮像を施行し，拡散強調像で両側腎に楔状の高信号域を認め，ALPEと確定診断した．
Ultra-high-pressure (UHP) peridotites found along collisional zones record rare information from deep within the Earth. However, the estimation of depth of origin for these UHP rocks has been ...controversial. A major controversy remains related to the conjectural proposition of mantle transition zone (410-660 km) origin of the Alpe Arami (AA) garnet peridotite massif in the Swiss Alps. In this contribution, we show micro-textural evidence of precursor majoritic garnet by documenting exsolved rutile, high-Al orthopyroxene, jadeite-rich clinopyroxene and olivine within the AA garnets in this peridotite. We also document an unforeseen texture of olivine with 'necklace' like enstatite corona in the kelyphite formed after decomposition of relict garnet. These olivines bear FeTiO
3
and Cr-spinel exsolution needles indicating retrogression from high-pressure Mg
2
SiO
4
. Thus, the occurrence of retrogressed high-pressure Mg
2
SiO
4
with enstatite corona in kelyphite suggests majorite breakdown to precipitate high-pressure Mg
2
SiO
4
near mantle transition zone (MTZ) depth. The SiO
2
released during decompression of majoritic garnets reacts with the high-pressure Mg
2
SiO
4
to produce the enstatite corona. Our documented micro-textures show high-pressure Mg
2
SiO
4
are breakdown product of precursor majoritic garnet, indicating that these micro-textures of the AA peridotite massif are sourced from the mantle transition zone (MTZ).
The Alpe di Roscioro, is a site of an unstable rock slope located above the village of Preonzo in southern Switzerland. There have been numerous rock-slope failures with a major event that happened ...in May 2012. After that event, several seismic stations were set up at the site of the remaining highly fractured and unstable rock mass. The analysis of continuous seismic recordings has shown a high number of permanent micro-deformations and tilts, recorded by a seismometer located on top of the unstable part of the slope. In terms of the ground motion, the directions of these disturbances are parallel to the mean strike of the mapped fracture network, implying a connection to the ongoing deformations of the rock mass. The static deformation field of the fractured rock mass is modeled by finite-difference method (FD). The FD method enables us to apply a reciprocal approach by tilting the affected body of block 1, closest to the stable massif, by measured values and observing the deformations below the seismometer and in the neighboring blocks. The numerical model explains the following features observed in situ: feature 1. The combination of the horizontal displacement and tilt observed approximately at the same measurement point; feature 2. The block 1 center of rotation is shifted towards SSE by ~10 m off its center; feature 3. The sensors placed on the stable massif did not record any micro-deformation and tilt signals above the background noise.
In the light of the numerical modeling, the weak coupling between the micro-tilt active block 1 and neighboring media explains the absence of detected events in the reference stations placed on the stable massif. The simplified “shear and bending” force system FD model, indicates that the aftermath of the May 2012 main failure consisted of numerous episodic elementary relaxations of the SSE part of block 1 after the collapse of its NNW compartment, which was previously connected to it.
•Micro-tilts and displacements of unstable rock slope recorded by seismometer•Micro-deformations of rock mass are distinguished from instrumental artifacts•The micro-deformations are not present in the stable massif•The deformations are modeled by Finite Differences in “shear and bending” scenarios•Coupling of the deformations between blocks is realized through bedrock.
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 + Fe
tot
2+
) 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 ε
Nd
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 SiO
2
and H
2
O, 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 H
2
O-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.
Geothermometry of eclogites and other high pressure (HP)/ultrahigh‐pressure (UHP) rocks has been a challenge, due to severe problems related to the reliability of the garnet–clinopyroxene Fe–Mg ...exchange thermometer to omphacite‐bearing assemblages. Likewise, reliable geobarometers for eclogites and related HP/UHP rocks are scarce. In this paper, a set of internally consistent geothermobarometric expressions have been formulated for reactions between the UHP assemblage garnet–clinopyroxene–kyanite–phengite–coesite, and the corresponding HP assemblage garnet–clinopyroxene–kyanite–phengite–quartz. In the system KCMASH, the end members grossular (Grs) and pyrope (Prp) in garnet, diopside (Di) in clinopyroxene, muscovite (Ms) and celadonite (Cel) in phengite together with kyanite and coesite or quartz define invariant points in the coesite and quartz stability field, respectively, depending on which SiO2 polymorph is stable. Thus, a set of net transfer reactions including these end members will uniquely define equilibrium temperatures and pressures for phengite–kyanite–SiO2‐bearing eclogites. Application to relevant eclogites from various localities worldwide show good consistency with petrographic evidence. Eclogites containing either coesite or polycrystalline quartz after coesite all plot within the coesite stability field, while typical quartz‐bearing eclogites with no evidence of former coesite fall within the quartz stability field. Diamondiferous coesite–kyanite eclogite and grospydite xenoliths in kimberlites all fall into the diamond stability field. The present method also yields consistent values as compared with the garnet–clinopyroxene Fe–Mg geothermometer for these kinds of rocks, but also indicates some unsystematic scatter of the latter thermometer. The net transfer geothermobarometric method presented in this paper is suggested to be less affected by later thermal re‐equilibration than common cation exchange thermometers.
The history of predation is recorded primarily from drilling in Cenozoic invertebrates. Quantitative data are uncommon from the Triassic, a period before the appearance and radiation of many known ...drill hole producers such as various gastropod families and octopods. We present quantitative evidence of drilling from the Late Triassic (Carnian) Cassian Formation of Italy and the Middle Triassic (Anisian) Lower Muschelkalk of Poland, documenting the first drill holes in Triassic brachiopods. A single brachiopod with a cylindrical, complete drill hole was found in a brachiopod sample from of Poland (drilling percentage=0.3%, n=365). The Cassian Formation yielded drill holes in gastropods, bivalves, and brachiopods, indicating that more species are drilled than was known previously. The minimum drilling percentage exclusive of incomplete drill holes of a sample from the Stuores Wiesen (Cassian Formation) is 1.7% (n=116.5). Prey selectivity is evident: complete drill holes are primarily present in one gastropod species, Polygyrina lommeli (11.8% of specimens with a complete drill hole), whereas other common species were not drilled. Single drill holes in brachiopods are cylindrical and complete and may be predatory in origin. Multiple drill holes in mollusks are common, and drill holes are parabolic and often incomplete with a central boss, resembling the shape of drill holes produced by extant naticid gastropods. A survey of the Paleozoic literature showed that such drill holes are also present in Devonian and Carboniferous brachiopods. However, naticids did not evolve until the Cretaceous so we propose the term “drill hole convergence” for similar-shaped drill holes produced by different organisms. The Triassic parabolic drill holes are not caused by domicile-seeking or boring organisms. Instead, we favor a predatory origin of these drill holes, but we cannot entirely rule out parasitism. Surveying other Triassic invertebrate assemblages should yield more evidence of drilling.
Display omitted
•We report on rare drill holes in mollusks and brachiopods from the Triassic.•The drill holes are most likely made by predators or, perhaps, parasites.•Most drill holes resemble those produced by modern naticid gastropods.•Similar holes also occur in the Paleozoic, when naticids were also absent.•“Drill hole convergence”: similar-shaped holes drilled by different organisms.
Little is known about water in nominally anhydrous minerals of orogenic garnet peridotite and enclosed metabasic rocks. This study is focused on peridotite‐hosted eclogite and garnetite ...(metarodingite) from the Erzgebirge (EG), Germany, and the Lepontine Alps (LA), Switzerland. Newly discovered, peridotite‐hosted eclogite in the Erzgebirge occurs in the same ultra‐high pressure (UHP) unit as gneiss‐hosted coesite eclogite, from which it is petrologically indistinguishable. Garnet is present in all mafic and ultramafic high pressure (HP) rocks providing for an ideal proxy to compare the H2O content of the different rock types. Garnet composition is very similar in EG and LA samples and depends on the rock type. Garnet from garnetite, compared to eclogite, contains more CaO (garnetite: 10.5–16.5 wt%; eclogite: 5–11 wt%) and is also characterized by an anomalous REE distribution. In contrast, the infrared (IR) spectra of garnet from both rock types reveal the same OH absorption bands that are also identical to those of previously studied peridotitic garnet from the same locations. Two groups of IR bands, SW I (3,650 ± 10 cm−1) and SW II (3,570–3,630 cm−1) are ascribed to structural hydroxyl (colloquially ‘water’). A third, broad band is present in about half of the analysed garnet domains and related to molecular water (MW) in submicroscopic fluid inclusions. The primary content of structural H2O, preserved in garnet domains without fluid inclusions (and MW bands), varies systematically—depending on both the location and the rock type. Garnet from EG rocks contains more water compared to LA samples, and garnet from garnetite (EG: 121–241 wt.ppm H2O; LA: 23–46 wt.ppm) hosts more water than eclogitic garnet (EG: 84 wt.ppm; LA: 4–11 wt.ppm). Higher contents of structural water (SW) are observed in domains with molecular water, in which the SW II band (being not restricted to HP conditions) is simultaneously enhanced. This implies that fluid influx during decompression not only led to fluid inclusions but also favoured the uptake of secondary SW. The results signify that garnet from all EG and LA samples was originally H2O‐undersaturated. Combining the data from eclogite, garnetite and previously studied peridotite, H2O and CaO are positively correlated, pointing to the same degree of H2O‐undersaturation at peak metamorphism in all rock types. This ubiquitous water‐deficiency cannot be reconciled with the derivation of any of these rocks from the lowermost part of the mantle wedge that was in contact with the subducting plate. This agrees with the previously inferred abyssal origin for part of the rocks from the LA (Cima di Gagnone). A similar origin has to be invoked for the Erzgebirge UHP unit. We suggest that all mafic and ultramafic rocks of this unit not only shared the same metamorphic evolution but also a common protolith origin, most probably on the ocean floor. This inference is supported by the presence of peridotite‐hosted garnetite, representing metamorphosed rodingite.
PDF
