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1.
Natalia Astudillo Pierrick Roperch Brian Townley Cesar Arriagada Annick Chauvin 《Mineralium Deposita》2010,45(1):23-41
El Teniente porphyry copper deposit, the world’s greatest intrusion-related Cu–Mo ore body, is hosted within basaltic–andesitic
volcanic and gabbroic rocks (mafic complex). This ore body is strongly affected by multiple events of alteration/mineralization
with pervasive potassic and chloritic alteration and coetaneous with associated copper mineralization. We present paleomagnetic
results obtained from oriented samples at four locations within the mine and from two drill cores, 200 and 400 m long, respectively.
Samples are representative of all the main hydrothermally altered rock units, with emphasis on the mafic host rock and dacitic
(Teniente dacite porphyry) and dioritic porphyry intrusions. Magnetic experiments [hysteresis loop, isothermal remanent magnetization
(IRM), k–T curves, thermal, and alternating field demagnetization] show the presence of prevailing magnetite. Microscope and SEM observations
show two families of magnetite, (a) large multidomain magnetite grains, associated with biotite and chlorite of various different
hydrothermal alteration events, and (b) abundant small to medium grain-size magnetite (<10 μm) contained within plagioclase,
either related to an early Na–Ca–Fe alteration or included within plagioclase during magmatic crystal growth. While the Teniente
dacite porphyry and the quartz diorite–tonalite have low magnetic susceptibility (<0.0005 SI) and low natural remanent magnetization
(NRM, 10−4–10−3 Am−1), the mineralized mafic host rocks have usually high susceptibility (>0.01 and up to 0.2 SI) with NRM in the range 0.1–2 Am−1. Most mafic complex rock samples have univectorial magnetizations during alternating field or thermal demagnetization. Within
the mine, the magnetic polarity is spatially distributed. In the northern part of the deposit, the Teniente dacite porphyry,
the associated hydrothermal breccias, and the hosting mafic complex record a reverse polarity magnetization, also observed
in the El Teniente sub-6 mine sector immediately to the east and southeast. In the eastern part of the deposit, a normal polarity
is observed for samples of the mafic complex from the two long drill cores. There is no evidence for superimposed magnetizations
of opposite polarities in samples of the mafic complex. Anhysteretic remanent magnetization (ARM) in a DC field of 40 μT and
NRM have similar magnitude and comparable behavior upon alternating field demagnetization. The well-defined strong remanent
magnetizations associated with high unblocking temperatures (>500°C) indicate an acquisition of remanent magnetization during
mineralization by circulating high temperature fluids related with ore deposition. Paleomagnetic results and the recorded
polarity zonation suggest multiple mineralization events occurred at El Teniente, each one with its own evolution stages,
superimposed within the district. These results indicate that a simplified broad four-stage model for El Teniente, as presented
and overly employed by many authors, divided in (1) late magmatic, (2) main hydrothermal, (3) late hydrothermal, and (4) posthumous
stage, does not recognize various short-lived single mineralization events, some superimposed and some distinctly separated
in time and space. There is no paleomagnetic evidence for post-mineralization deformation 相似文献
2.
Christian Creixell Miguel ngel Parada Pierrick Roperch Diego Morata Csar Arriagada Carlos Prez de Arce 《Tectonophysics》2006,425(1-4):101-122
The Concón Mafic Dike Swarm (CMDS) consists of basaltic to andesitic dikes emplaced into deformed Late Paleozoic granitoids during the development of the Jurassic arc of central Chile. The dikes are divided into an early group of thick dikes (5–12 m) and a late group of thin dikes (0.5–3 m). Two new amphibole 40Ar/39Ar dates obtained from undeformed and deformed dikes, constrain the age of emplacement and deformation of the CMDS between 163 and 157 Ma. Based on radiometric ages, field observations, AMS studies and petrographic data, we conclude that the emplacement of the CMDS was syntectonic with the Jurassic arc extension and associated with sinistral displacements along the NW-trending structures that host the CMDS. The common occurrence of already deformed and rotated xenoliths in the dikes indicates that deformation in the granitoids started previously.The early thick dikes and country rocks appear to have been remagnetized during the exhumation of deep-seated coastal rocks in the Early Cretaceous (around 100 Ma). The remanent magnetization in late thin dikes is mainly retained by small amounts of low-Ti magnetite at high temperature and pyrrhotite at low temperature. The magnetization in these dikes appears to be primary in origin. Paleomagnetic results from the thin dikes also indicate that the whole area was tilted 23° to the NNW during cooling of the CMDS.The NNW–SSE extension vectors deduced from the paleomagnetic data and internal fabric of dikes are different with respect to extension direction deduced for the Middle–Late Jurassic of northern Chile, pointing to major heterogeneities along the margin of the overriding plate during the Mesozoic or differences in the mechanisms driving extension during such period. 相似文献
3.
Simulating Stable Isotope Ratios in Plumes of Groundwater Pollutants with BIOSCREEN‐AT‐ISO 
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下载免费PDF全文 Patrick Höhener Zhi M. Li Maxime Julien Pierrick Nun Richard J. Robins Gérald S. Remaud 《Ground water》2017,55(2):261-267
BIOSCREEN is a well‐known simple tool for evaluating the transport of dissolved contaminants in groundwater, ideal for rapid screening and teaching. This work extends the BIOSCREEN model for the calculation of stable isotope ratios in contaminants. A three‐dimensional exact solution of the reactive transport from a patch source, accounting for fractionation by first‐order decay and/or sorption, is used. The results match those from a previously published isotope model but are much simpler to obtain. Two different isotopes may be computed, and dual isotope plots can be viewed. The dual isotope assessment is a rapidly emerging new approach for identifying process mechanisms in aquifers. Furthermore, deviations of isotope ratios at specific reactive positions with respect to “bulk” ratios in the whole compound can be simulated. This model is named BIOSCREEN‐AT‐ISO and will be downloadable from the journal homepage. 相似文献
4.
Mustafa Y. Kaya Guillaume Dupont‐Nivet Jean‐Noël Proust Pierrick Roperch Laurie Bougeois Niels Meijer Joost Frieling Chiara Fioroni Sevin
zkan Alt&#x;ner Ezgi Vardar Natasha Barbolini Marius Stoica Jovid Aminov Mehmut Mamtimin Guo Zhaojie 《Basin Research》2019,31(3):461-486
The proto‐Paratethys Sea covered a vast area extending from the Mediterranean Tethys to the Tarim Basin in western China during Cretaceous and early Paleogene. Climate modelling and proxy studies suggest that Asian aridification has been governed by westerly moisture modulated by fluctuations of the proto‐Paratethys Sea. Transgressive and regressive episodes of the proto‐Paratethys Sea have been previously recognized but their timing, extent and depositional environments remain poorly constrained. This hampers understanding of their driving mechanisms (tectonic and/or eustatic) and their contribution to Asian aridification. Here, we present a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy as well as a detailed palaeoenvironmental analysis for the Paleogene proto‐Paratethys Sea incursions in the Tajik and Tarim basins. This enables us to identify the major drivers of marine fluctuations and their potential consequences on Asian aridification. A major regional restriction event, marked by the exceptionally thick (≤ 400 m) shelf evaporites is assigned a Danian‐Selandian age (ca. 63–59 Ma) in the Aertashi Formation. This is followed by the largest recorded proto‐Paratethys Sea incursion with a transgression estimated as early Thanetian (ca. 59–57 Ma) and a regression within the Ypresian (ca. 53–52 Ma), both within the Qimugen Formation. The transgression of the next incursion in the Kalatar and Wulagen formations is now constrained as early Lutetian (ca. 47–46 Ma), whereas its regression in the Bashibulake Formation is constrained as late Lutetian (ca. 41 Ma) and is associated with a drastic increase in both tectonic subsidence and basin infilling. The age of the final and least pronounced sea incursion restricted to the westernmost margin of the Tarim Basin is assigned as Bartonian–Priabonian (ca. 39.7–36.7 Ma). We interpret the long‐term westward retreat of the proto‐Paratethys Sea starting at ca. 41 Ma to be associated with far‐field tectonic effects of the Indo‐Asia collision and Pamir/Tibetan plateau uplift. Short‐term eustatic sea level transgressions are superimposed on this long‐term regression and seem coeval with the transgression events in the other northern Peri‐Tethyan sedimentary provinces for the 1st and 2nd sea incursions. However, the 3rd sea incursion is interpreted as related to tectonism. The transgressive and regressive intervals of the proto‐Paratethys Sea correlate well with the reported humid and arid phases, respectively in the Qaidam and Xining basins, thus demonstrating the role of the proto‐Paratethys Sea as an important moisture source for the Asian interior and its regression as a contributor to Asian aridification. 相似文献
5.
A regional ocean model was used to simulate the annual cycle of the upper-ocean dynamics and its influence on ocean properties in the tropical western Indian Ocean. Surface winds and heat fluxes from the National Centers for Environmental Prediction (NCEP) reanalysis forced the model (Model_NCEP) with initial and lateral boundary conditions derived from the Simple Ocean Data Assimilation (SODA). The model findings were in good agreement with previous research, satellite and observational data as well as another model configuration forced by Comprehensive Ocean and Atmosphere Data Sets (COADS). The initial and lateral boundary conditions for Model_COADS were extracted from World Ocean Atlas 2001. Anticyclonic wind stress curl occurred to the north of Madagascar, and extended towards the Tanzanian coast throughout the year, leading to Ekman convergence and downwelling in that region. The lowest sea-surface height values during the year occurred between 5° and 12° S with an elongated and contracted shape. The East African Coastal Current (EACC) was in phase with the westward North-East Madagascar Current (NEMC) throughout the year with volume transports peaking in June through July in the model forced by NCEP reanalysis. The variability of the volume transport, ocean currents, temperature and salinity to the north of Madagascar on the path of the NEMC mirrored those in the middle Tanzanian shelf on the path of the EACC throughout the year. The NEMC seemed to influence the water masses on the Tanzanian shelf, with cooler and lower-salinity water in the South-West Monsoon, and warmer and saltier water during the North-East Monsoon. 相似文献
6.
Lin Li Yani Najman Guillaume Dupont-Nivet Mauricio Parra Pierrick Roperch Mustafa Kaya Niels Meijer Paul O'Sullivan Gilby Jepson Jovid Aminov 《Basin Research》2023,35(2):530-550
Knowledge of the tectonic history of the Pamir contributes to our understanding of both the evolution of collisional orogenic belts as well as factors controlling Central Asian aridification. It is, however, not easy to decipher the Mesozoic–Cenozoic tectonics of the Pamir due to extensive Neogene deformation in an orogen that remains largely understudied. This study reports detrital apatite and zircon fission-track (FT) ages from both the eastern Tajik Basin sedimentary rocks and Pamir modern river sands. These FT data, supported by vitrinite reflectance and zircon and apatite U–Pb double dating, suggest that the majority of the FT ages are unreset and record exhumation stages of the Pamir, which has served as the source terrane of the Tajik Basin since the Cretaceous. Furthermore, we combine the new data with a compilation of published detrital apatite and zircon FT data from both the Tajik Basin sedimentary rocks and Pamir modern river sands, to explore the Mesozoic–Cenozoic tectonic history of Pamir. Deconvolved FT Peak Ages document two major Mesozoic exhumation events associated with the Late Triassic–Early Jurassic Cimmerian orogeny that reflects accretion of the Pamir terranes, as well as the Early–early Late Cretaceous deformation associated with the northward subduction of the Neo-Tethys Ocean beneath Pamir. The compiled data also show significant Late Eocene–Neogene exhumation associated with the ongoing formation of the Pamir, which peaks at ca. 36, 25, 14 and 7 Ma. 相似文献
7.
Kristensen Lene Czekirda Justyna Penna Ivanna Etzelmüller Bernd Nicolet Pierrick Pullarello José Santiago Blikra Lars Harald Skrede Ingrid Oldani Simon Abellan Antonio 《Landslides》2021,18(6):1963-1980
On September 5, 2019, the Veslemannen unstable rock slope (54,000 m3) in Romsdalen, Western Norway, failed catastrophically after 5 years of continuous monitoring. During this period, the rock slope weakened while the precursor movements increased progressively, in particular from 2017. Measured displacement prior to the failure was around 19 m in the upper parts of the instability and 4–5 m in the toe area. The pre-failure movements were usually associated with precipitation events, where peak velocities occurred 2–12 h after maximum precipitation. This indicates that the pore-water pressure in the sliding zones had a large influence on the slope stability. The sensitivity to rainfall increased greatly from spring to autumn suggesting a thermal control on the pore-water pressure. Transient modelling of temperatures suggests near permafrost conditions, and deep seasonal frost was certainly present. We propose that a frozen surface layer prevented water percolation to the sliding zone during spring snowmelt and early summer rainfalls. A transition from possible permafrost to a seasonal frost setting of the landslide body after 2000 was modelled, which may have affected the slope stability. Repeated rapid accelerations during late summers and autumns caused a total of 16 events of the red (high) hazard level and evacuation of the hazard zone. Threshold values for velocity were used in the risk management when increasing or decreasing hazard levels. The inverse velocity method was initially of little value. However, in the final phase before the failure, the inverse velocity method was useful for forecasting the time of failure. Risk communication was important for maintaining public trust in early-warning systems, and especially critical is the communication of the difference between issuing the red hazard level and predicting a landslide.
相似文献8.
David Brown Lars Ceranna Mark Prior Pierrick Mialle Ronan J. Le Bras 《Pure and Applied Geophysics》2014,171(3-5):361-375
The International Data Centre (IDC) in Vienna, Austria, is determining, as part of automatic processing, sensor noise levels for all seismic, hydroacoustic, and infrasound (SHI) stations in the International Monitoring System (IMS) operated by the Provisional Technical Secretariat of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). Sensor noise is being determined several times per day as a power spectral density (PSD) using the Welch overlapping method. Based on accumulated PSD statistics a probability density function (PDF) is also determined, from which low and high noise curves for each sensor are extracted. Global low and high noise curves as a function of frequency for each of the SHI technologies are determined as the minimum and maximum of the individual station low and high noise curves, respectively, taken over the entire network of contributing stations. An attempt is made to ensure that only correctly calibrated station data contributes to the global noise models by additionally considering various automatic detection statistics. In this paper global low and high noise curves for 2010 are presented for each of the SHI monitoring technologies. Except for a very slight deviation at the microseism peak, the seismic global low noise model returns identically the Peterson (1993) NLNM low noise curve. The global infrasonic low noise model is found to agree with that of Bowman et al. (2005, 2007) but disagrees with the revised results presented in Bowman et al. (2009) by a factor of 2 in the calculation of the PSD. The global hydroacoustic low and high noise curves are found to be in quantitative agreement with Urick’s oceanic ambient noise curves for light to heavy shipping. Whale noise is found to be a feature of the hydroacoustic high noise curves at around 15 and 25 Hz. 相似文献
9.
Christian Creixell Miguel Ángel Parada Diego Morata Pierrick Roperch César Arriagada 《International Journal of Earth Sciences》2009,98(1):177-201
Five mafic dike swarms between 30° and 33°45′S were studied for their geochemical signature and kinematics of magma flow directions
by means of AMS data. In the Coastal Range of central Chile (33°−33°45′S), Middle Jurassic dike swarms (Concón and Cartagena
dike swarms, CMDS and CrMDS, respectively) and an Early Cretaceous dike swarm (El Tabo Dike Swarm, ETDS) display the presence
of dikes of geochemically enriched (high-Ti) and depleted (low-Ti) basaltic composition. These dikes show geochemical patterns
that are different from the composition of mafic enclaves of the Middle Jurassic Papudo-Quintero Complex, and this suggests
that the dikes were injected from reservoirs not related to the plutonic complex. The mantle source appears to be a depleted
mantle for Jurassic dikes and a heterogeneous-enriched lithospheric mantle for Cretaceous dikes. In the ETDS, vertical and
gently plunging magma flow vectors were estimated for enriched and depleted dikes, respectively, which suggest, together with
variations in dike thickness, that reservoirs were located at different depths for each dike family. In the Elqui Dike Swarm
(EDS) and Limarí Mafic Dike Swarm (LMDS), geochemical patterns are similar to those of the mafic enclaves of the Middle Jurassic
plutons. In the LMDS, east to west magma flow vectors are coherent with injection from neighbouring pluton located to the
east. In the EDS, some dikes show geochemical and magma flow patterns supporting the same hypothesis. Accordingly, dikes do
not necessarily come from deep reservoir; they may propagate in the upper crust from coeval shallow pluton chamber.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Jérôme Jourde Christine Dupuy Hien T. Nguyen David Mizrahi Nyls de Pracontal Pierrick Bocher 《Estuaries and Coasts》2017,40(4):1159-1170
In tropical South America, the mudflats of the Amazonian coast are unique because of their large size and unrivaled migration dynamics. On Guiana’s coast, macrofaunal communities are believed to be well-adapted to these dynamic conditions. In this study, the benthic macrofauna was sampled in April 2012 in the Awala-Yalimapo region of western French Guiana and at two sites in Suriname: Warappa Kreek and Bigi Pan. These sites are found 800, 920, and 1140 km from the Amazon delta, respectively. The richness, diversity, and densities of the macrofaunal communities in these mudflats are here described for the first time. Only 38 operational taxonomic units (OTUs) were recorded, among which two species were common and widely distributed: the tanaid crustacean Halmyrapseudes spaansi and the polychaete Sigambra grubii; the former represented 84% of all individuals collected, with densities reaching up to 73,000 individuals m?2. Most of the OTUs consisted of relatively small individuals (<10 mm in length). The very low richness and diversity and the small sizes of the organisms are likely linked to the instability and softness of the substrate on these mudflats. This study suggests that the differences in macrofaunal community composition among sites could be due to the migration stage of banks rather than the distance from the Amazon delta and associated effects of river discharge. 相似文献