The diffusion kinetics of CO2 in cordierite: an HT-FTIR microspectroscopy study     

Francesco Radica  Giancarlo Della Ventura  Fabio Bellatreccia  Gianfelice Cinque  Augusto Marcelli  Mariangela Cestelli Guidi 《Contributions to Mineralogy and Petrology》2016,171(2):12

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Fault geometries from the space distribution of the 1990–1997 Sannio–Benevento earthquakes: inferences on the active deformation in Southern Apennines     

Giuseppe Vilardo  Rosa Nappi  Palma Petti  Guido Ventura 《Tectonophysics》2003,363(3-4):259-271

In this study, we analyze the recent (1990–1997) seismicity that affected the northern sector (Sannio–Benevento area) of the Southern Apennines chain. We applied the Best Estimate Method (BEM), which collapses hypocentral clouds, to the events of low energy (M_{d max}=4.1) seismic sequences in order to constrain the location and geometry of the seismogenetic structures. The results indicate that earthquakes aligned along three main structures: two sub-parallel structures striking NW–SE (1990–1992, Benevento sequence) and one structure striking NE–SW (1997, Sannio sequence). The southernmost NW–SE structure, which dips towards NE, overlies the fault that is likely to be responsible for a larger historical earthquake (I_{o max}=XI MCS, 1688 earthquake). The northernmost NW–SE striking structure dips towards SW. The NE–SW striking structure is sub-vertical and it is located at the northern tip of the fault segment supposed to be responsible for the 1688 earthquake. The spatio-temporal evolution of the 1990–1997 seismicity indicates a progressive migration from SE (Benevento) to NW (Sannio) associated to a deepening of hypocenters (i.e., from about 5 to 12 km). Hypocenters cluster at the interface between the major structural discontinuities (e.g., pre-existing thrust surfaces) or within higher rigidity layers (e.g., the Apulia carbonates). Available focal mechanisms from earthquakes occurred on the recognized NW–SE and NE–SW faults are consistent with dip-slip normal solutions. This evidences the occurrence of coexisting NW–SE and NE–SW extensions in Southern Apennines.  相似文献   

Age and sources of gold mineralization in the Marmato mining district, NW Colombia: A Miocene–Pliocene epizonal gold deposit     

Colombo Celso Gaeta Tassinari  Fabio Diaz Pinzon  Juaquin Buena Ventura 《Ore Geology Reviews》2008,33(3-4):505-518

Epigenetic gold mineralization occurs in the Marmato mining district, within the Calima Terrain of the Setentrional Andes, Colombia. Regional rocks associated with this mineralization include: graphite- and chlorite-schists of the Arquia Complex; metamorphosed during the Cretaceous, Miocene sandstones, shales and conglomerates of the Amagá Formation; as well as pyroclastic rocks (clasts of basalt, andesites and mafic lavas) and subvolcanic andesitic/dacitic bodies of the Combia Formation (9 to 6 Ma). The subvolcanic Marmato stock hosts mesothermal and epithermal low-sulfidation Au–Ag ores in the form of distensional veins, stockwork, and quartz veinlets within brecciated zones. Ore minerals are pyrite, sphalerite and galena with subordinate chalcopyrite, arsenopyrite, pyrrhotite, argentite and native gold/electrum.Sericitized plagioclase from a porphyry dacite yielded a K–Ar age of 5.6 ± 0.6 Ma, interpreted as the age of ore deposition. This is in close agreement with the age of reactivation of the Cauca–Romeral Fault System (5.6 ± 0.4 Ma), which bounds the Calima Terrain. A porphyry andesite–dacite (6.7 ± 0.1 Ma), hosting the Au–Ag veins, shows a measured ⁸⁷Sr/⁸⁶Sr between 0.70440 and 0.70460, ε_Nd between + 2.2 and + 3.2 and ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of 18.964 to 19.028; 15.561 to 15.570; and 38.640 to 38.745, respectively. The ⁸⁷Sr/⁸⁶Sr and ε_Nd values of rocks from the Arquia Group range from 0.70431 to 0.73511 and − 12.91 to + 10.0, respectively, whereas the corresponding Pb isotopic ratios (²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb) range from 18.948 to 19.652; 15.564 to 15.702; and 38.640 to 38.885, respectively. ⁸⁷Sr/⁸⁶Sr and ε_Nd values obtained on sulfides from the gold quartz veins, which occur at shallow and intermediate levels, range from 0.70500 to 0.71210 and from − 1.11 to + 2.40. In the deepest veins, ε_Nd values lie between + 1.25 and + 3.28 and the ⁸⁷Sr/⁸⁶Sr of calcite and pyrite fall between 0.70444 and 0.70930. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of all mineralization are in the ranges 18.970 to 19.258; 15.605 to 15.726 and 38.813 to 39.208, respectively. Carbonates have an average ⁸⁷Sr/⁸⁶Sr ratio of 0.70445, which is within the range of values measured in the host dacite. The Sr isotopic data indicate that carbonic fluids have a restricted hydrothermal circulation within the host igneous body, while the Sr, Pb and Nd isotopic compositions of the sulfides suggest that the fluids not only circulated within the Marmato stock, but also throughout the Arquia Complex, inferring that these rocks offer a potential target for mineral exploration. Based on geological and geochronological evidence, the epizonal Marmato gold ores formed during the Miocene to Pliocene, as a result of cooling of the Marmato stock and reactivation along a crustal-scale fault zone related to thermal processes in an accretionary oceanic–continental plate orogen.  相似文献   

Load distribution in large pile groups under static and dynamic loading     

J. Dowling  W. D. L. Finn  C. E. Ventura  M. Taiebat 《Bulletin of Earthquake Engineering》2016,14(6):1461-1474

Research on the action of pile groups in resisting lateral loading is usually based on analysis, field and centrifuge tests of small pile groups. The interaction between piles in these groups is modelled by modifying the lateral resistance p–y curves developed for a single pile using row dependent reduction factors or a group factor for the entire group to simulate the effect of soil–pile–soil interaction. The modifying factors for the p–y curves and the appropriate group factors for pile groups are based entirely on static tests and there is no direct verification that these factors are appropriate to handle the dynamic loading of earthquake induced ground motions. In this paper we investigate the interaction effects between piles under static and seismic loading using the computer program VERSAT-P3D, which uses an equivalent linear constitutive model for the soil. The analytical procedure is calibrated using data from a static field load test on a single pile. Several pile groups, 2 × 2, 3 × 3, 4 × 4, 5 × 5, 8 × 8, 10 × 10, 10 × 2 and 15 × 2 were analysed for the study. Each group was subjected to static pushover and earthquake loading and the distribution of static and dynamic shear forces at various lateral displacements were evaluated. The study shows that the distribution of load within a pile group under dynamic loading varies significantly from the distribution under static loading and is strongly load intensity dependent. Current practice assumes that the distributions are similar.  相似文献   

Pattern and pathways for mercury lifespan bioaccumulation in Carcinus maenas     

Coelho JP  Reis AT  Ventura S  Pereira ME  Duarte AC  Pardal MA 《Marine pollution bulletin》2008,56(6):1104-1110

Carcinus maenas is an important and exploited natural resource in temperate estuaries, being consumed by local populations and also used as fish bait. Through bioaccumulation and bioamplification processes occurring in polluted estuarine ecosystems, this species may directly or indirectly represent a major pathway for Human contamination. No information is available on the overall lifespan bioaccumulation pattern of mercury for this species, which would be an invaluable tool for assessing the risks associated with C. maenas harvest in contaminated areas. Taking that in mind, the main objectives of this work were to clarify the lifespan bioaccumulation pattern of mercury for this species. A consistent lifespan accumulation pattern was found for this species, both for total and organic mercury, and coherent differences were found between genders, suggesting different physiological responses to contamination. From our results two scenarios emerge: (a) for low mercury contamination areas where the diet is the major pathway for metal uptake, with higher levels in muscle and hepatopancreas (twice as high as in gills) and higher organic mercury fractions (as high as 80-90% in muscle), crabs bioaccumulate with age and (b) on high contaminated areas, environmental exposure is predominant, with higher levels found in gills (reaching 0.8 mg kg(-1)), lower organic fractions and no mercury increment with age. Detoxification strategies, dietary differences and species mobility may account for these two accumulation patterns.  相似文献   

The P21/m↔ C2/m phase transition in synthetic amphibole Na NaMg Mg5 Si8 O22 (OH)2: thermodynamic and crystal-chemical evaluation     

F. Cámara  R. Oberti  G. Iezzi  G. Della Ventura 《Physics and Chemistry of Minerals》2003,30(9):570-581

The P2₁/mC2/m displacive phase transition in the synthetic end-member amphibole Na NaMg Mg₅ Si₈ O₂₂ (OH)₂ has been studied by monitoring changes in unit-cell parameters and the intensities of superlattice reflections at 25–400 °C. This amphibole allows investigation of the effects of compositional variations at the A- and B-group sites upon the transition. Polynomial fitting of a 24 Landau potential to the evolution of the order parameter with T yielded a T _c of 257 ± 3 °C, and Landau coefficients compatible with a second-order transition. Structure refinement of single-crystal data collected at 25, 140, 270 and 370 °C allowed modelling of the structural changes as a function of T and symmetry. Crystal-chemical analysis suggests that differences in T _c in cummingtonites and in the crystal of this work depend mainly upon the relations between the aggregate ionic radii of the B- and C-group cations. Electronic Supplementary Material: of Table 5 is available in the online version of this article at http://dx.doi.org/10.1007/s00269-003-0348-9  相似文献   

Structural features of the shallow plumbing system of Vulcano Island Italy     

C.?Chiarabba  N.?A.?Pino  G.?Ventura  G.?VilardoEmail author 《Bulletin of Volcanology》2004,66(6):477-484

In this study, we integrate information gathered from surface geology and tectonics with the results of a shallow (0–2 km b.s.l.) seismic tomography of Vulcano Island (Italy), obtained from the analysis of local earthquakes. The observed low Vp regions correspond to caldera filling products, mainly consisting of pyroclastics, tuffs, lava flows and hyaloclastites. High-velocity anomalies represent intrusive bodies. The striking correspondence between the stratigraphy from deep wells and the calculated velocity structure allows us to reconstruct the geometry and distribution of a main intrusion and to recognize some intra-caldera depressions. The shape and location of the high and low Vp anomalies are consistent with NW–SE and N–S strikes. Eruptive centres younger than 42 kyr, as well as the structural depressions of Vulcano and of the neighbour Lipari Island, align along a N–S direction. The combined interpretation of the available structural data and of the results from the tomography suggests that magmatic reservoirs of Vulcano at shallow depth (>0.5 km) align along a NW–SE strike but their shape is controlled by N–S striking normal faults and/or cracks that accommodate the right-lateral movements of the NW–SE strike-slip fault system.Editorial responsibility: T. Druitt  相似文献   

1-D and 2-D analyses of weak motion data in Fraser Delta from 1966 Duvall earthquake     

W. D. Liam Finn  E. Zhai  T. Thavaraj  X. -S. Hao  C. E. Ventura 《Soil Dynamics and Earthquake Engineering》2003,23(4):323-329

The 1996 Duvall earthquake in Washington State triggered ground motion stations in the Fraser Delta, British Columbia, located on varying depths of Holocene and Pleistocene soils to a maximum depth of 800 m and one station on bedrock. Recorded ground motions were used to examine the applicability of 1-D and 2-D site response analyses for amplification studies in the Delta. 1-D response analysis gave a good indication of the period of peak response. Response spectra computed by 1-D analysis did not compare well with recorded spectra except at very deep sites. The use of 2-D analyses to include buried topography generally improved the predictions of site response spectra at the shallow sites. However, for the shallow earth sites, the recorded motions showed a strong spectral response at short periods in the range of 0.1–0.25 s. Neither 1-D nor 2-D analysis predicted this response.  相似文献   

A Reliable Method for Determining the Oxidation State of Manganese at the Microscale in Mn Oxides via Raman Spectroscopy     

Simone Bernardini  Fabio Bellatreccia  Giancarlo Della Ventura  Armida Sodo 《Geostandards and Geoanalytical Research》2021,45(1):223-244

Manganese oxides are important geomaterials, widespread in terrestrial and Martian environments. Characterisation of the oxidation state of Mn is a central issue in science; this task has been addressed up to the present by X‐ray spectroscopy or diffraction techniques. The former, however, requires access to synchrotron facilities, while the latter does not provide crystal‐chemical information at the local scale. In this work, we compare a large set of Raman data from well‐characterised samples, already published by the same authors of this paper or as found in the literature. We show a clear correlation between the oxidation state of Mn and the wavenumber of peculiar bands; octahedrally co‐ordinated Mn²⁺ is recognised by a band around 530 cm^?1, Mn³⁺ by a band around 580 cm^?1 and Mn⁴⁺ by a band around 630 cm^?1, while tetrahedrally co‐ordinated Mn²⁺ is recognisable by a band around 650 cm^?1. Strongly distorted Mn³⁺ octahedra are indicated by the appearance of Jahn–Teller modes. Our method allows a reliable, easily accessible tool to characterise the oxidation states of Mn in oxides, also suitable for microscale mapping. It provides a robust analytical basis for the use of these minerals as redox indicators in geology/geochemistry, in exoplanetary research or for monitoring technological processes.  相似文献   

Modeling the multi-level plumbing system of the Changbaishan caldera from geochemical,mineralogical, Sr-Nd isotopic and integrated geophysical data     

Jian Yi  Pujun Wang  Xuanlong Shan  Guido Ventura  Chengzhi Wu  Jiannan Guo  Pencheng Liu  Jiahui Li 《地学前缘(英文版)》2021,12(5):101171

Changbaishan, an intraplate volcano, is characterized by an approximately 6 km wide summit caldera and last erupted in 1903. Changbaishan experienced a period of unrest between 2002 and 2006. The activity developed in three main stages, including shield volcano(basalts), cone-construction(trachyandesites to trachytes with minor basalts), and caldera-forming stages(trachytes to comendites). This last stage is associated with one of the more energetic eruptions of the last millennium on Earth, the 946 CE, VEI 7 Millennium Eruption(ME),which emitted over 100 km3 of pyroclastics. Compared to other active calderas, the plumbing system of Changbaishan and its evolution mechanisms remain poorly constrained. Here, we merge new whole-rock,glass, mineral, isotopic, and geobarometry data with geophysical data and present a model of the plumbing system. The results show that the volcano is characterized by at least three main magma reservoirs at different depths: a basaltic reservoir at the Moho/lower crust depth, an intermediate reservoir at 10–15 km depth, and a shallower reservoir at 0.5–3 km depth. The shallower reservoir was involved in the ME eruption, which was triggered by a fresh trachytic melt entering a shallower reservoir where a comenditic magma was stored. The trachytes and comendites originate from fractional crystallization processes and minor assimilation of upper crust material, while the less evolved melts assimilate lower crust material. Syn-eruptive magma mingling occurred during the ME eruption phase. The magma reservoirs of the caldera-forming stage partly reactivate those of the cone-construction stage. The depth of the magma storage zones is controlled by the layering of the crust.The plumbing system of Changbaishan is vertically extensive, with crystal mush reservoirs renewed by the replenishment of new trachytic to trachyandesitic magma from depth. Unlike other volcanoes, evidence of a basaltic recharge is lacking. The interpretation of the signals preceding possible future eruptions should consider the multi-level nature of the Changbaishan plumbing system. A new arrival of magma may destabilize a part of or the entire system, thus triggering eruptions of different sizes and styles. The reference model proposed here for Changbaishan represents a prerequisite to properly understand periods of unrest to potentially anticipate future volcanic eruptions and to identify the mechanisms controlling the evolution of the crust below volcanoes.  相似文献