Marked Anomalies Research Articles

Geochemical evolution of the Tertiary succession of the NW shelf, Bengal basin, Bangladesh: Implications for provenance, paleoweathering and Himalayan erosion

Whole rock major, trace and rare earth element (REE) compositions of Paleogene to Neogene sedimentary rocks of the NW shelf succession (Province 1) of Bangladesh contain a record of interaction of the India and Asian plates, Himalayan tectonism, and climatic development. Analyses of 66 sandstones and mudrocks from the Tertiary succession of Bangladesh were made to examine provenance, source weathering, and the influence of paleoclimate and tectonism. The sediments display linear geochemical trends due to quartz dilution, and varying quartz–clay ratios produced by hydrodynamic sorting. Chondrite-normalized REE patterns for both sandstones and mudrocks from different groups are similar to upper continental crust, with moderate to high LREE enrichment (lithotypes within formations average LaN/YbN 5.31–11.41) and marked negative Eu anomalies (Eu/Eu* 0.51–0.69). Based on geochemical criteria the succession can be divided into three parts (Jaintia; Barail–Surma; and Dupi Tila). Very high silica contents in Jaintia Tura sandstones and high Chemical Index of Alteration (CIA) indices in Kopili mudrocks (Fe-shales) suggest derivation from a deeply weathered and stable cratonic source (India). The Tura sandstones are interpreted as first-cycle quartz arenites, produced while the Indian plate drifted across equatorial regions during the Paleocene–Eocene Thermal maximum (PETM). The Barail–Surma and Dupi Tila sediments were derived from a felsic orogen (the Himalaya). The Barail–Surma sediments were mainly derived from the Trans Himalayan Batholith and associated granitoids, with significant contribution from the Lesser Himalaya. Mafic input is also evident, probably from intraoceanic arc material within the Himalaya. Barail mudrocks have uniformly high CIA values (92–95), suggesting intense steady-state weathering of their proto-Himalayan source, and warm and humid climate. In contrast, CIA values of Surma mudrocks range from 66 to 93 (average 84), suggesting non-steady state weathering related to active uplift in the Himalaya. The Dupi Tila sediments were derived from a more felsic Lesser Himalaya source, with significant contribution from the Trans-Himalaya and very little or no ophiolitic or arc material. Dupi Tila mudrocks have CIA ratios of 62–99 (average 72), also indicating non-steady state weathering in the rising Himalayan source. Geochemical compositions of the NW shelf sediments are comparable to coeval successions in the Surma basin (Province 2) of Bangladesh and the Siwaliks (India), indicating similar source. Evolution of the Indian monsoon and associated high precipitation caused intense chemical weathering of the Surma and Dupi Tila source, despite rapid uplift. The Surma Group thus bears the signature of evolution of the Asian monsoon in the Bengal basin at 21Ma, simultaneous with the development of the East Asian monsoon. This supports proposals that both monsoon systems developed at the same time.

High-Field Phase Diagram of SmRu4P12Determined by Ultrasonic Measurements in Pulsed Magnetic Field up to 55 T

Elastic constant measurements were performed for the filled skutterudite compound SmRu4P12 in a pulsed magnetic field up to 55 T of \(H\parallel\langle 111\rangle\) to create a high-field phase diagram. The field dependence of the transverse elastic constant \(C_{\text{T}} = (C_{11} - C_{12} + C_{44})/3\) shows two marked anomalies, one of which was assigned as a magnetic transition \(T^{*}\). The other anomaly was newly discovered. The newly discovered phase boundary is immersed in the known phase III, and joins to the known II–III boundary. This particular behavior is compared with the recently proposed theory, and discussed on the basis of the octupole model for this system.

A crustal–upper mantle model for southeastern Sicily (Italy) from the integration of petrologic and geophysical data

An interdisciplinary approach is proposed to investigate the structure and composition of the Permo-Triassic basement of the Hyblean Plateau and Sicily Channel. Comparisons of published data on peridotites and spinels from different geodynamic settings, and new data on Hyblean spinels, reveal the affinity of the Hyblean basement with an ultra-slow spreading oceanic lithosphere, rather than with the Africa continental plate. Similar results derive from volcanic rocks of the studied area, whose Nb/Yb vs. Th/Yb ratio hints at their affinity with the MORB–OIB array, even excluding any possible contamination with continental crust lithologies, unlike North Africa lavas. The comparison of He isotopic ratios from Hyblean Plateau and Sicily Channel highlights their similarity with values measured in fluids emitted from the Rainbow and Logatchev hydrothermal fields in Mid-Atlantic Ridge. Based on petrologic and geochemical evidence for the oceanic nature of the Permo-Triassic basement in southeastern Sicily, and the occurrence of serpentinized harzburgite xenoliths in Hyblean diatremes, the P-wave velocity model proposed for the investigated area is used to estimate lithospheric pressure, density, degree of serpentinization and magnetic susceptibility also considering both abyssal and ophiolitic serpentinites. The resulting values suggest the presence of peridotites affected by different degrees of serpentinization (35–100vol.%) ranging to a depth of 8–19km. As a whole, combined seismic, gravimetric and magnetic data indicate the presence of a marked anomaly at a depth of about 19km. As a consequence, we consider the Moho discontinuity as a serpentinization front, by fixing the relative top at a depth of 19km. Our results suggest that the oceanic lithospheric model for southeastern Sicily could be broadened to the Sicily Channel, which is possibly correlated to the adjacent Ionian oceanic basin, inferred as belonging to the Oman–Iraq–Levantine–Sicily seaway.

¿Hay lugar en atención primaria para las enfermedades poco frecuentes? El caso de la fibrodisplasia osificante progresiva

Fibrodysplasia ossificans progressiva is one of the most devastating constitutional diseases of the bone, and may be a valid example to establish the role of Primary Care in the care of rare diseases. Although rare diseases usually present with marked anomalies, they can mimic signs and symptoms of common disorders, with the risk of going unnoticed. For this reason, all health professionals should proceed with a reasonable suspicion when confronted with a patient with an apparently common disease with atypical symptoms and a non-conventional progress. The care given by the Primary Care team along with other health care services are fundamental in the integrated and individualised follow-up. The quality of care in rare diseases must not be inferior to that provided to the other chronic diseases, since, besides being a requirement of justice and fairness, these patients are, in essence, the “paradigm of chronicity”.

Petrological and zircon evidence for anatexis of UHP quartzite during continental collision in the Sulu orogen

AbstractPetrological evidence is provided for anatexis of ultrahigh‐pressure (UHP) metamorphic quartzite in the Sulu orogen. Some feldspar grains exhibit elongated, highly cuspate shapes or occur as interstitial, cuspate phases constituting interconnected networks along grain boundaries. Elongated veinlets composed of plagioclase + quartz ± K‐feldspar also occur in grain boundaries. These features provide compelling evidence for anatexis of the UHP quartzite. Zircon grains from impure quartzite are all metamorphic growth with highly irregular shape. They contain inclusions of coesite, jadeite, rutile and lower pressure minerals, including multiphase solid inclusions that are composed of two or more phases of muscovite, quartz, K‐feldspar and plagioclase. All zircon grains exhibit steep REE patterns, similar U–Pb ages and Hf isotope compositions with a weighted mean of 218 ± 2 Ma. Most grains have similar δ18O values of −0.6 to 0.1‰, but a few fall in the range −5.2 to −4.3‰. Thus, these grains would have grown from anatectic melts at various pressures. Zircon O isotope differences indicate that anatectic melts were derived from different sources with contrasting O isotopes, but similar Hf isotopes, that is, one from the quartzite itself and the other probably from the country‐rock granitic gneiss. Zircon grains from pure quartzite contain relict magmatic cores and significant metamorphic overgrowths. Domains that contain eclogite facies minerals exhibit flat HREE patterns, no Eu anomalies and concordant U–Pb ages of c. 220 Ma. Similar U–Pb ages are also obtained for domains that contain lower pressure minerals and exhibit steep REE patterns and marked negative Eu anomalies. These observations indicate that zircon records subsolidus overgrowth at eclogite facies conditions but suprasolidus growth at lower pressures. Zircon enclosed by garnet gave consistent U–Pb ages of c. 214 Ma. Such garnet is interpreted as a peritectic product of the anatectic reaction that involves felsic minerals and possibly amphibole and titanite. The REE patterns of epidote and titanite also record multistage growth and metasomatism by anatectic melts. Therefore, the anatexis of UHP metamorphic rocks is evident during continental collision in the Triassic.

Radon measurements over a natural-gas contaminated aquifer

Abstract Radon and thoron concentrations in soil pores in a gas production region of the Anzoategui State, Venezuela, were determined by active and passive methods. In this region, water wells are contaminated by natural gas and gas leaks exist in the nearby river. Based on soil gas Radon data surface hydrocarbon seeps were identified. Radon and thoron concentration maps show anomalously high values near the river gas leaks decreasing in the direction of water wells where natural gas is also detected. The area where the highest concentrations of 222Rn were detected seems to indicate the surface projection of the aquifer contaminated with natural gas. The Radon/Thoron ratio revealed a micro-localized anomaly, indicating the area where the gas comes from deep layers of the subsoil. The radon map determined by the passive method showed a marked positive anomaly around abandoned gas wells. The high anomalous Radon concentration localized near the trails of ascending gas bubbles at the river indicates the zone trough where natural gases are ascending with greater ease, associated with a deep geological fault, being this the main source of methane penetration into the aquifer. It is suggested that the source of the natural gas may be due to leaks at deep sites along the structure of some of the abandoned wells located at the North-East of the studied area.

Synexhumation anatexis of ultrahigh-pressure metamorphic rocks: Petrological evidence from granitic gneiss in the Sulu orogen

Petrological evidence is provided for partial melting of ultrahigh-pressure (UHP) metamorphic granitic gneiss in the Sulu orogen. Petrographic observations show the occurrence of elongated, highly cuspate feldspars in grain boundaries, interstitial cuspate feldspars in triple junctions, felsic veinlets mainly consisting of K-feldspar+quartz, and feldspar crystal faces against quartz. These features indicate that the feldspar and quartz would have grown from anatectic melts in the granitic gneiss. Zircon domains grown from these melts were identified based on CL images, mineral inclusions and REE patterns. Some large zircon grains (>100μm) contain small relict domains of magmatic origin, suggesting nearly complete dissolution of the protolith zircon during the anatexis. All newly grown zircon domains are categorized into two groups based on the presence or absence of coesite inclusions. One group of domains contain no coesite inclusion and exhibit high U contents but low Th/U ratios (<0.1), steep REE patterns with strong negative Eu anomalies, and UPb ages of 217±2 to 224±2Ma. The other group of domains contain coesite inclusions and exhibit low U contents and very low Th/U ratios (<0.01), steep REE patterns with strong negative Eu anomalies, and UPb ages of 221±5 to 226±3Ma. The two groups of zircon domains are thus interpreted as growing from the anatectic melts at different pressures because they exhibit marked negative Eu anomalies that are absent for metamorphic zircons grown from aqueous fluids. The zircon UPb ages of 217±2 to 226±3Ma are close to, but slightly younger than, known ages for major UHP metamorphism in the Sulu orogen. Therefore, the UHP gneiss experienced incipient melting during the initial exhumation subsequent to the peak UHP metamorphism and extensive anatexis later at lower pressures. Muscovite relicts coexist with cuspate feldspars, suggesting that the anatectic melts originate from dehydration melting due to decompression breakdown of phengitic muscovite in the UHP granitic gneiss. As the degree of partial melting increases with temperature, significant fractions of the anatectic melts would be produced in the regional gneiss provided that the UHP rocks experienced “hot” exhumation. Such melts can be gathered together, being eventually emplaced as synexhumation granitic intrusions.

Arsenic-induced oxidative stress in the common bean legume, Phaseolus vulgaris L. seedlings and its amelioration by exogenous nitric oxide.

The adverse effects of arsenic (As) toxicity on seedling growth, root and shoot anatomy, chlorophyll and carotenoid contents, root oxidizability (RO), antioxidant enzyme activities, H2O2 content, lipid peroxidation and electrolyte leakage (EL%) in common bean (Phaseolus vulgaris L.) were investigated. The role of exogenous nitric oxide (NO) in amelioration of As-induced inhibitory effect was also evaluated using sodium nitroprusside (100μM SNP) as NO donor and 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (200μM PTIO) as NO scavenger in different combinations with 50μM As. As-induced growth inhibition was associated with marked anomalies in anatomical features, reduction in pigment composition, increased RO and severe perturbations in antioxidant enzyme activities. While activity of superoxide dismutase and catalase increased, levels of ascorbate peroxidase, dehydroascorbate reductase and glutathione reductase decreased significantly and guaiacol peroxidase remained normal. The over-accumulation of H2O2 content along with high level of lipid peroxidation and electrolyte leakage indicates As-induced oxidative damage in P. vulgaris seedlings with more pronounced effect on the roots than the shoots. Exogenous addition of NO significantly reversed the As-induced oxidative stress, maintaining H2O2 in a certain level through balanced alterations of antioxidant enzyme activities. The role of NO in the process of amelioration has ultimately been manifested by significant reduction of membrane damage and improvement of growth performance in plants grown on As + SNP media. Onset of oxidative stress was more severe after addition of PTIO, which confirms the protective role of NO against As-induced oxidative damage in P. vulgaris seedlings.

Petrogenesis of Late Cretaceous lava flows from a Ceno-Tethyan island arc: The Raskoh arc, Balochistan, Pakistan

The Raskoh arc is about 250km long, 40km wide and trends in an ENE direction. The oldest rock unit in the Raskoh arc is an accretionary complex (Early to Late Jurassic), which is followed in age by Kuchakki Volcanic Group, the most wide spread unit of the Raskoh arc. The Volcanic Group is mainly composed of basaltic to andesitic lava flows and volcaniclastics, including agglomerate, volcanic conglomerate, breccia and tuff, with subordinate shale, sandstone, limestone and chert. The flows generally form 3–15m thick lenticular bodies but rarely reach up to 300m. They are mainly basaltic–andesites with minor basalts and andesites. The main textures exhibited by these rocks are hypocrystalline porphyritic, subcumulophyric and intergranular. The phenocrysts comprise mainly plagioclase (An30–54 in Nok Chah and An56–64 in Bunap). They are embedded in a micro-cryptocrystalline groundmass having the same minerals. Apatite, magnetite, titanomagnetite and hematite occur as accessory minerals.Major, trace and rare earth elements suggest that the volcanics are oceanic island arc tholeiites. Their low Mg # (42–56) and higher FeO (total)/MgO (1.24–2.67) ratios indicate that the parent magma of these rocks was not directly derived from a mantle source but fractionated in an upper level magma chamber. The trace element patterns show enrichment in LILE and depletion in HFSE relative to N-MORB. Their primordial mantle-normalized trace element patterns show marked negative Nb anomalies with positive spikes on K, Ba and Sr which confirm their island arc signatures. Slightly depleted LREE to flat chondrite normalized REE patterns further support this interpretation. The Zr versus Zr/Y and Cr versus Y studies show that their parent magma was generated by 20–30% melting of a depleted mantle source. The trace elements ratios including Zr/Y (1.73–3.10), Ti/Zr (81.59–101.83), Ti/V (12.39–30.34), La/YbN (0.74–2.69), Ta/Yb (0.02–0.05) and Th/Yb (0.11–0.75) of the volcanics are more consistent with oceanic island arcs rather than continental margin arcs. It is suggested that the Raskoh arc is an oceanic island arc which formed due to the intra-oceanic convergence in the Ceno-Tethys during the Late Cretaceous rather than constructed on the southern continental margin of the Afghan block, as claimed by previous workers. It is further suggested that the Semail, Zagros, Chagai–Raskoh, Muslim Bagh, and Waziristan island arcs were developed in a single but segmented Cretaceous Ceno-Tethyan convergence zone.

REE geochemistry of carbonates from the Guanmenshan Formation, Liaohe Group, NE Sino-Korean Craton: Implications for seawater compositional change during the Great Oxidation Event

The worldwide 2.33–2.06Ga positive δ13Ccarb excursion has been correlated with the Great Oxidation Event (GOE) and termed as the Lomagundi Event. The 2.3−1.85Ga Guanmenshan Formation in the Liaohe Group of the northeastern Sino-Korean Craton is characterized by positive δ13Ccarb excursion and is a potential candidate to evaluate the Lomagundi Event using REY (rare earth element and yttrium, REE+Y) chemical fingerprints. Here we present major and trace element analysis of 42 samples from the Guanmenshan Formation which are pure marine chemical sediments and use the data to trace the seawater composition during 2.3–1.85Ga. 15 least altered dolomicrite samples (>600m strata) have ∑REE values of 0.739–4.175ppm (2.414±1.184ppm) and the Y/Ho ratios of 34.5–56.6 (44.1±5.7). They show uniform positive LaSN/LaSN* (1.04±0.27) and GdSN/GdSN* (1.64±0.40) anomalies, and notable LREE depletions indicated by NdSN/YbSN values of 0.24–0.92 (average 0.56±0.19). These features are consistent with the geochemistry of well-oxygenated, shallow ambient seawater, and suggest that these samples provide a robust record of the primary REY signature of seawater during the Lomagundi Event. The REY patterns of 15 silicified dolomites/marbles (locally with veinlets) from the Pb–Zn mining camps in the region, with average EuCN/EuCN*=1.56±0.95, are identical to those of high-temperature hydrothermal fluids (>250°C), characterized by a flat pattern and marked positive Eu anomalies, indicating that these rocks were subjected to metasomatism by hydrothermal fluids. The Guanmenshan Formation shows average CeSN/CeSN* of 0.93±0.09 and SmCN/YbCN of >1 which are higher than those of the Archean (>2.33Ga) chemical sediments (generally <1), suggesting that the REY geochemical characteristics of the carbonates from our study area were dominantly controlled by the nature of atmosphere–hydrosphere system, such as fO2 and pCO2. The REY in the dolomicrite were mainly sourced from fluxes of solutes from terrestrial weathering, and also from seafloor hydrothermal processes on a subordinate scale. The Guanmenshan dolomicrites have EuSN/EuSN* values of 1.34–2.55, i.e. around 1.53, indicating that they were deposited during 2.33–2.06Ga, as the EuSN/EuSN*≈1.53 can be used as a proxy for the 2.33–2.06Ga marine chemical sediments. Our study shows that the Guanmenshan Formation was formed at a critical turning point in Earth history when the global atmosphere–hydrosphere system witnessed a dramatic change from reducing to oxidizing conditions.

Consideration of a Safe Protocol for Hepatocyte Transplantation Using Infantile Pigs

Hepatocyte transplantation is hoped to be an alternative treatment to certain cases of liver transplantation. The most promising indication is for congenital metabolic diseases, especially in infants. To establish a safe protocol for hepatocyte transplantation into infants, we examined physiological changes during treatment using infantile pigs. Recipient pigs (domestic, crossbred with Large-Yorkshire, Landrace, and Duroc; 2.5 kg; 7-14 days old) were anesthetized with isoflurane; a midline incision of minimum length provided access to the superior mesenteric vein. A double lumen catheter was inserted through the vein to within 1 cm of the hepatic portal region. Physiological parameters such as heart rate, systemic blood pressure, and portal pressure were monitored. Cryopreserved porcine hepatocytes isolated from the same strain were suspended in physiological saline and transfused through the catheter. In experiments requiring tracing, cells were stained with fluorescent dye prior to transfusion. Recipient pigs were kept for 1 day and sacrificed for histological liver examination. After preliminary experiments, the optimized number and concentration for hepatocyte transplantation were determined to be 1 × 108 cells/kg and 1 × 107 cells/ml. The cell suspension was transfused at a rate of 0.67 ml/min. No marked anomaly of physiological parameters was observed, whereas light tachycardia occurred in preliminary trials when the transfusion rate was faster than our standard protocol. All five pigs transfused with the established method recovered from anesthesia and survived with good vital signs. Histology revealed that the transfused hepatocytes were integrated in the hepatic tissue.

Origin of the Maoduan Pb–Zn–Mo deposit, eastern Cathaysia Block, China: geological, geochronological, geochemical, and Sr–Nd–Pb–S isotopic constraints

The Maoduan Pb–Zn–Mo deposit is in hydrothermal veins with a pyrrhotite stage followed by a molybdenite and base metal stage. The Re–Os model ages of five molybdenite samples range from 138.6 ± 2.0 to 140.0 ± 1.9 Ma. Their isochron age is 137.7 ± 2.7 Ma. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating of the nearby exposed Linggen granite porphyry gave a 206Pb/238U age of 152.2 ± 2.2 Ma and the hidden Maoduan monzogranite yielded a mean of 140.0 ± 1.6 Ma. These results suggest that the intrusion of the Maoduan monzogranite and Pb–Zn–Mo mineralization are contemporaneous. δ 34S values of sulfide minerals range from 3.4‰ to 4.8‰, similar to magmatic sulfur. Four sulfide samples have 206Pb/204Pb = 18.252–18.432, 207Pb/204Pb = 15.609–15.779, and 208Pb/204Pb = 38.640–39.431, similar to the age-corrected data of the Maoduan monzogranite. These isotope data support a genetic relationship between the Pb–Zn–Mo mineralization and the Maoduan monzogranite and probably indicate a common deep source. The Maoduan monzogranite has geochemical features similar to highly fractionated I-type granites, such as high SiO2 (73.7–75.2 wt.%) and alkalis (K2O + Na2O = 7.8–8.9 wt.%) and low FeOt (0.8–1.3 wt.%), MgO (~0.3 wt.%), P2O5 (~0.03 wt.%), and TiO2 (~0.2 wt.%). The granitic rocks are enriched in Rb, Th, and U but depleted in Ba, Sr, Nb, Ta, P, and Ti. REE patterns are characterized by marked negative Eu anomalies (Eu/Eu* = 0.2–0.4). The Maoduan monzogranite, having (87Sr/86Sr) t = 0.7169 to 0.7170 and eNd(t) = −13.8 to −13.7, was probably derived from mixing of partial melts from enriched mantle and the Paleoproterozoic Badu group in an extensional tectonic setting.

ERK2 Contributes to the Control of Social Behaviors in Mice

Signaling through extracellular signal-regulated kinase (ERK) is important in multiple signal transduction networks in the CNS. However, the specific role of ERK2 in in vivo brain functions is not fully understood. Here we show that ERK2 play a critical role in regulating social behaviors as well as cognitive and emotional behaviors in mice. To study the brain function of ERK2, we used a conditional, region-specific, genetic approach to target Erk2 using the Cre/loxP strategy with a nestin promoter-driven cre transgenic mouse line to induce recombination in the CNS. The resulting Erk2 conditional knock-out (CKO) mice, in which Erk2 was abrogated specifically in the CNS, were viable and fertile with a normal appearance. These mice, however, exhibited marked anomalies in multiple aspects of social behaviors related to facets of autism-spectrum disorders: elevated aggressive behaviors, deficits in maternal nurturing, poor nest-building, and lower levels of social familiarity and social interaction. Erk2 CKO mice also exhibited decreased anxiety-related behaviors and impaired long-term memory. Pharmacological inhibition of ERK1 phosphorylation in Erk2 CKO mice did not affect the impairments in social behaviors and learning disabilities, indicating that ERK2, but not ERK1 plays a critical role in these behaviors. Our findings suggest that ERK2 has complex and multiple roles in the CNS, with important implications for human psychiatric disorders characterized by deficits in social behaviors.

Intraseasonal and interannual zonal circulations over the Equatorial Indian Ocean

El Nino Southern Oscillation (ENSO) and given phases of the Madden–Julian Oscillation (MJO) show similar regional signatures over the Equatorial Indian Ocean, consisting in an enhancement or reversing of the convective and dynamic zonal gradients between East Africa and the Maritime Continent of Indonesia. This study analyses how these two modes of variability add or cancel their effects at their respective timescales, through an investigation of the equatorial cellular circulations over the central Indian Ocean. Results show that (1) the wind shear between the lower and upper troposphere is related to marked regional rainfall anomalies and is embedded in larger-scale atmospheric configurations, involving the Southern Oscillation; (2) the intraseasonal (30–60 days) and interannual (4–5 years) timescales are the most energetic frequencies that modulate these circulations, confirming the implication of the MJO and ENSO; (3) extreme values of the Indian Ocean wind shear result from the combination of El Nino and the MJO phase enhancing atmospheric convection over Africa, or La Nina and the MJO phase associated with convective activity over the Maritime Continent. Consequences for regional rainfall anomalies over East Africa and Indonesia are then discussed.

Selected trace and minor elements in sandstones from Paraguay

Abstract Selected trace and minor elements analyzed by XRF in sandstone samples were Rb-Sr-Zr-Nb-Ba-La-Ce-Nd as well as Ti-Mn-Fe with which they are often correlated. Refractory elements like REE are considered useful indicators of geochemical processes and, in this case, of provenance . Usually they maintain their original relationships and are transferred almost directly into sediments. The values here found, absolute and normalized, show correlations among the samples, allowing the establishment of their origin. Most of them in the spidergram patterns display positive spikes of Zr, and negative anomalies at Nb, Sr, Ti: differences in their height/depth could be in relation with the different Series or Formations. Strikingly, spidergrams of samples collected from the Patiño Formation show marked negative anomalies interalia of Ba, as well as positive spikes of Nb and Zr, very similar to those found in magmatic specimens from Misiones, Carapeguá-Acahay and Alto Paraguay Province and quite different from the other analyzed samples. In addition a remarkable presence of Precambrian signatures were found in the analyzed sandstones from the Paleozoic.

Origin of the Mt Ashmore structural dome, west Bonaparte Basin, Timor Sea

New insights into the 3D structure, composition and origin of the Mt Ashmore dome, west Bonaparte Basin, Timor Sea, are enabled by reprocessed seismic-reflection data and by optical microscopic, X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM) analyses of drill cuttings. The structural dome, located below a major pre-Oligocene post-Late Eocene unconformity and above a ∼6 km-deep-seated basement high indicated by marked gravity and magnetic anomalies, displays chaotic deformation at its core and a centripetal kinematic deformation pattern. A study of drill cuttings of Lower Oligocene to Lower Jurassic sedimentary rocks intersected by the Mt Ashmore 1B petroleum-exploration well reveals microbrecciation and extreme comminution and flow-textured fluidisation of altered sedimentary material. The microbreccia is dominated by aggregates of poorly diffracting micrometre to tens of micrometres-scale to sub-millimetre particles, including relic subplanar fractured quartz grains, carbonate, barite, apatite and K-feldspar. A similar assemblage occurs in fragments in basal Oligocene sediments, probably derived from the eroded top section of the dome, which protrudes above the unconformity. SEM coupled with EDS show the micrometre to tens of micrometres-scale particles are characterised by very low totals and non-stoichiometric compositions, including particles dominated by Si, Al–Si, Si–Ca–Al, Si–Al–Ca, Si–Mg, Fe–Mg–Ca, Fe–Mg and carbonate. XRD analysis identifies a high proportion of amorphous poorly diffracting material. TEM indicates internally heterogeneous, fragmented and recrystallised structure of the amorphous grains, which accounts for the low totals in terms of the high-volatile and porous nature of the particles. Another factor for the low totals is the uneven thin-section surfaces which affect the totals. No volcanic material or evaporites were encountered in the drillcore, militating against interpretations of the structure in terms of magmatic intrusion or salt diapirism. Such models are also inconsistent with the strong gravity and magnetic anomalies, which signify a basement high below the dome. An interpretation of the dome in terms of a central rebound uplift of an impact structure can not be proven due to the lack of shock metamorphic effects such as planar deformation features, impact melt or coesite. However, an impact model is consistent with the chaotic structure of the domal core, centripetal sense of deformation, microbrecciation, comminution and fluidisation of the Triassic to Eocene rocks. In this respect, an analogy can be drawn between the Mt Ashmore structural dome and likely but unproven impact structures formed in volatile (H2O, CO2)-rich sediments where shock is attenuated by high volatile pressure, such as Upheaval Dome, Utah. In terms of an impact hypothesis the Mt Ashmore dome is contemporaneous with a Late Eocene impact cluster (Popigai: D = 100 km, 35.7 ± 0.2 Ma; Chesapeake Bay: D = 85 km, 35.3 ± 0.1 Ma).

Trace element chemistry of mineral inclusions in eclogitic diamonds from the Premier (Cullinan) and Finsch kimberlites, South Africa: Implications for the evolution of their mantle source

Although diamonds of eclogitic paragenesis are commonly encountered in the productions of many Southern Africa kimberlites, the nature and evolution of the protolith to eclogitic diamonds are still poorly understood. There is some evidence that these protoliths (and possibly also the diamonds) may be related to subduction of oceanic crust, although this is not a universally accepted view. In order to further investigate the protolith/diamond relationship, garnets and (in some cases) clinopyroxene inclusions in 23 diamonds from Premier mine and 16 diamonds from Finsch were analysed for their trace element composition. From both mines a strong correlation between the garnet Ca content and the chondrite-normalised rare earth element (REE) pattern is evident. Garnets with comparatively low Ca content are characterised by REE patterns which show a steady increase in abundance from light rare earths (LREE) to heavy rare earths (HREE). With increasing Ca content in garnet, the abundance of LREE (La, Ce, Pr, and Nd) as well as the middle rare earths (MREE; Sm, Eu, Gd, and Tb) progressively increases, ultimately giving the trace element pattern a distinct ‘humped’ appearance. Bulk-rock trace element abundance patterns have been reconstructed from measured trace element contents in garnet as well as calculated trace element concentrations in clinopyroxene, based on known clinopyroxene–garnet partition coefficients ( Harte and Kirkley, 1997). At both Premier and Finsch, the low-Ca group samples (2.6 to 5.0 wt.% CaO in garnet) are LREE depleted, and have relatively flat calculated bulk-rock trace element abundance patterns at approximately 10 times chondrite concentrations, but with marked positive Sr and negative Zr anomalies. The intermediate-Ca group samples (5.2 to ∼9 wt.% CaO in garnet) are LREE depleted, show Sr and Zr anomalies, have somewhat higher concentrations of Zr and MREE, and have HREE contents that overlap with the low-Ca group ( Fig. 6). High-Ca group samples (∼ 9 to 14.8 wt.% CaO in garnet) are LREE depleted, show Sr and Zr anomalies, are MREE-enriched, and have HREE contents that are slightly less than the low- and intermediate-Ca group samples. Based on both the calculated bulk eclogite trace element abundances and their patterns, as well as previously published radiogenic isotope data, our preferred model of protolith evolution for the eclogitic diamonds from Premier and Finsch is one in which both the major and trace element chemistry of the inclusions are ultimately inherited from low-pressure oceanic protoliths, consisting of varying mixtures of oceanic basalt + cumulate gabbro for diamonds from both Premier and Finsch. Of particular importance in the current data are the presence of marked negative Zr anomalies, marked positive Sr anomalies, and a general absence of Eu anomalies in all compositional groupings. The Zr anomaly can arise in reconstructed bulk eclogite trace element abundance patterns if rutile is not included in the calculations, but the Sr anomalies (coupled with an absence of Eu anomalies) can only be explained through the mixing of oceanic gabbro and mid-ocean ridge basalt. The averaged eclogite bulk trace element compositions for Premier and Finsch are also markedly similar to that of clinopyroxene in a typical cumulate gabbro, and a role for cumulate clinopyroxene in protolith evolution may therefore also be inferred. It is likely that prior to and during diamond crystallisation, the major and particularly the trace element compositions of the high-pressure eclogite source rock to these diamonds may have been slightly modified by metasomatic fluids and melts. However large-scale fluid- or melt-related metasomatic processes are not indicated.

Carboniferous high-potassium I-type granitoid magmatism in the Eastern Pontides: The Gümüşhane pluton (NE Turkey)

The Gümüşhane pluton, a high-K calc-alkaline I-type granodiorite/granite complex, forms an important component of the pre-Liassic basement of the Eastern Pontides (NE Turkey). In its eastern part, the pluton shows a compositional zonation ranging from biotite–hornblende granodiorite in the NW through biotite–hornblende granite to leucogranite/granophyre in the SE. Numerous mafic microgranular enclaves (up to ∼ 40 cm in diameter) suggest the former presence of globules of mafic melt during crystallization. Emplacement of the pluton occurred during the latest Early Carboniferous, as shown by the 320 ± 4 Ma 40Ar– 39Ar biotite/hornblende and 324 ± 6 Ma LA-ICP-MS U–Pb zircon ages. In Harker diagrams, samples of the different rock types exhibit well-defined data trends. With increasing SiO 2, the abundances of TiO 2, Al 2O 3, Fe 2O 3 tot, MnO, MgO, CaO, P 2O 5 and Sc decrease, but those of K 2O and Rb increase. However, the variations of Sr, Ba, (La/Yb) cn, Sr/Y and ∑ REEs vs. SiO 2 form distinctive groupings, which cannot be explained by a simple fractional crystallization. Chondrite-normalized (cn) REE patterns of granodiorite/granite samples show concave-upward shapes with (La/Yb) cn ranging from 5.2 to 12.4 and Eu/Eu* from 0.84 to 0.47, while there is almost no fractionation of the middle REE relative to the heavy REE. In primitive mantle-normalized element concentration diagrams, all rocks display marked negative anomalies in Ba, Nb/Ta, Sr, P and Ti, but positive anomalies in K and Pb. These geochemical features imply a fractionating mineral assemblage of clinopyroxene, amphibole and plagioclase without significant involvement of garnet. The granophyres are, on the other hand, characterized by higher K 2O/Na 2O and Rb/Sr ratios, lower (La/Yb) cn ratios (1.3 to 4.8) and more pronounced negative anomalies in Ba, Nb/Ta, Sr, Eu, P and Ti. Initial ε Nd values range from − 3.78 to − 5.30 and Nd model ages from 1.38 to 163 Ga. The magmas of the granite/granodiorite portion were probably generated by partial melting of high-potassic amphibolitic rocks, and those of the granophyres by a relatively felsic micaceous crustal source. The Gümüşhane pluton was emplaced at the wake of the low-pressure–high-temperature metamorphism, and is regarded as a late phase of Hercynian orogeny in the Eastern Pontides.

Geochronologies of the Huaixi copper-gold deposit and the Caomen alkaline granite, SE China: implications for tectonic evolution

The Huaixi copper-gold polymetallic deposit of SE Zhejiang Province, China, is a typical hydrothermal-vein ore body. The Caomen K-feldspar granite porphyry, the dominant intrusion in the mining district, has been dated by laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) analyses of zircon, which yielded a weighted mean 206Pb/238U age of 101.6 ± 0.9 Ma (MSDW = 1.3). Rb-Sr dating of fluid inclusions in auriferous quartz from ore bodies yielded an isochron age of 101 ± 2 Ma. These results indicate that intrusion of the Caomen pluton and Cu-Au mineralization was contemporaneous and corresponds to the third episode of Mesozoic magmatism and metallogenesis in South China. Calculated δ18O values of fluid inclusions from ore-bearing quartz range from −0.89 to −1.98‰ and δD from −42.60 to −60.20‰, suggesting that the ore-forming fluids are derived from a mixed source of magmatic and meteoric waters. δ18S values of 8 pyrites range from −2.14 to +4.14‰ with a mean of +1.67‰, similar to magmatic sulphur. These isotope data support a genetic relationship between the Huaixi copper-gold deposit and the Caomen alkaline granite and probably indicate a common deep source. Petrography and chemical compositions show that the Caomen alkaline granite crystallized from shoshonitic magmas characterized by high SiO2 (75.64–78.00%) and alkali (K2O + Na2O = 7.96–8.82%) but low FeOT (1.34–3.31%), P2O5 (0.05–0.13%) and TiO2 (0.12–0.18%). The granitic rocks are enriched in Ga, Rb, Th, U, and Pb but depleted in Ba, Nb, Sr, P, and Ti. REEs are characterized by marked negative Eu anomalies (Eu/Eu* = 0.06–0.13) and exhibit right-dipping ‘V’ patterns with LREE enrichment. These are similar to the Late Cretaceous alkaline granites in the coastal areas of Zhejiang and Fujian provinces, implying that the Caomen granite formed in a post-collisional extensional tectonic setting. Combined with previous studies, we interpret the Huaixi copper-gold deposit and the associated Caomen alkaline granite as related to back-arc extension due to high-angle subduction of the palaeo-Pacific plate, caused by northward movement of the Indian plate.

Underplating and assimilation–fractional crystallization of Mesozoic intrusions in the Tongling area, Anhui Province, East China: evidence from xenoliths and host plutons

This paper presents new petrographic observations and geochemical and microprobe analyses for the Laomiaojishan, Xiaotongguanshan, and Tianebaodanshan intrusions in the Tongguanshan mineral district, East China. The plutons vary in composition from quartz monzonitic diorite to pyroxene monzonitic diorite, and contain gabbroic to dioritic xenoliths. The Xiaotongguanshan intrusion yields a SHRIMP zircon U–Pb age of 139.5±2.9 Ma, indicating Late Jurassic to Early Cretaceous magmatism in the Lower Yangtze River Valley. Relative to host rocks, the gabbro and diorite xenoliths are low in SiO2 (52.03–54.61 wt‐%), Al2O3 (12.87–14.43 wt‐%), and total alkalis (Na2O+K2O; 5.26–6.30 wt‐%), but high in MgO (5.41–11.66 wt‐%); the host rocks have high SiO2 (59.97–64.44 wt‐%), Al2O3 (16.43–17.59 wt‐%), and total alkalis (6.67–8.25 wt‐%), but are low in MgO (1.52–2.50 wt‐%). Concentrations of rare earth elements (REEs) in the xenoliths (165.70–190.40 ppm) are similar to those in the host rocks (166.12–185.95 ppm), although the ratio of light REEs to heavy REEs in the xenoliths (3.39–4.27) is lower than that in the host plutons (4.86–5.94). All of the analysed rocks show similar REE patterns, although the xenoliths display marked positive Eu anomalies and the host rocks show slightly negative Eu anomalies. Values of epsilon Nd (t) ranges from −4.9 to −9.9 in the gabbro xenoliths and from −11.4 to −11.9 in the host intrusives. Initial 87Sr/86Sr ratios are 0.7064–0.7073 in the xenoliths and 0.7072–0.7084 in the quartz monzonitic diorite host rocks. Crystallization temperatures of hornblende and plagioclase in the gabbro xenoliths, diorite xenoliths, and host rocks are 816, 773–790, and 664–725°C, respectively, based on an amphibole–plagioclase geothermometer. The pressures recorded by these phases indicate that they formed at depths of 26, 12–15, and 3–4 km, respectively, based on an aluminum‐in‐hornblende geobarometer. The petrological and geochemical features of the analysed intrusions and xenoliths are consistent with their derivation from basic to intermediate‐acidic magmas that possibly formed via a series of complex interactions between underplated, mantle‐derived basaltic magma and varying amounts of middle‐ to lower‐crustal material, followed by assimilation–fractional crystallization.