Sr and Nd Characteristics of Brasiliano/Pan-African Granitoid Plutons of the Araçuaí Orogen, Southeastern Brazil: Tectonic Implications     

Veridiana T. de S. Martins  Wilson Teixeira  Carlos M. Noce  Antonio C. Pedrosa-Soares 《Gondwana Research》2004,7(1):75-89

Nd and Sr isotope data were obtained for three plutonic suites (595–505 Ma) and distinct young granitoid intrusions (503 Ma), from the southern part of the Neoproterozoic Araçuaí Orogen. The Sr and Nd isotopes (⁸⁷Sr/⁸⁶Sr, eNd) and TDM values from the plutons and distinct basement rocks are used to constrain the magma genesis of the granitoid plutons. These isotopic parameters, with e_Nd values ranging from −4 to −24 and T_DM ages from 1.3 to 2.8 Ga, for the granitoid suites, and −5 to −40 and 3.5 to 1.5 Ga, for the distinct Archean and Proterozoic basement complexes, suggest that the Jequitinhonha Complex metasediments are the main crustal source for most of these plutons, except for the youngest granitoid intrusions, which may have a protolith similar to the Mantiqueira and Guanhães complexes. Furthermore, the isotope data indicate a minor, but important, participation of Neoproterozoic oceanic lithosphere in the granite genesis, which corroborates with a confined orogenic model and a narrow oceanic consumption (B-subduction) for the Araçuaí Orogen.  相似文献   

Multi-criteria analysis for the identification of waste disposal areas   总被引：1，自引：0，他引：1  

Maria Lúcia Calijuri  Eder T. Marques  Juliana F. Lorentz  Roberto F. Azevedo  Carlos A. B. Carvalho 《Geotechnical and Geological Engineering》2004,22(2):299-312

The municipality of Cachoeiro de Itapemirim (ES) is currently the largest domestic producer and exporter of marble and granite in Brazil. The processing of the rock, especially the sawing results in a large volume of waste, including the abrasives used during sawing and the off-cut pieces. Presently these waste products are disposed of without proper environmental protection and cause pollution to surface water and groundwater resources, including silting, an increase in hardness and increased aluminium values in the groundwater. In order to minimize the harmful effects of these practices on the environment, a research project was undertaken to identify potential disposal sites for the generated waste. A multi-criteria approach was followed during which a database was compiled of all the companies generating waste products and also including a baseline environmental study of the region, integrated analysis (multi-criteria analysis) of the restriction factors and the preliminary identification of possible disposal sites. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Experimental investigation of the effect of dissolution on sandstone permeability, porosity, and reactive surface area     

Carlos F.Jové Colón  Eric H Oelkers 《Geochimica et cosmochimica acta》2004,68(4):805-817

The temporal permeability, porosity, and reactive surface area evolution during dissolution of nonfractured/clay-free Fontainebleau sandstone cores was measured using a flow through percolation reactor. Four core dissolution experiments, each of ∼1000 h duration, were performed on sandstone cores having initial porosities ranging from 5.1 to 16.6%. All experiments were performed at 80°C and at far from equilibrium conditions using a 0.1 M NaOH input solution with a calculated in situ pH of 11.4. Permeability evolution was determined using Darcy’s law together with in situ measured differential pressures. Reactive surface area and porosity evolution were quantified from the mass of Si leaving the core during the experiments. The 5.1 and 8.9% initial porosity sandstone cores experienced porosity increases of 1.2 and 1.4 percent, respectively, during the experiments. These cores experienced a corresponding permeability increase from 0.27 to 0.74 mD and 0.57 to 0.87 mD, respectively. In contrast, the 10.6 and 16.6% initial porosity sandstone cores had permeabilities that were essentially constant during the dissolution experiments despite porosity increases of 6.3 and 2.5%, respectively. Only the 5.1% initial porosity core experienced a permeability evolution roughly consistent with a cubic law dependence on porosity. Reactive surface areas increased during the experiments for all cores; those for the 5.1, 10.6, and 16.6% initial porosity cores increased by 21±6% for each percent porosity increase. The reactive surface area of the 8.9% initial porosity core, however, increased by 148% for each percent porosity increase. These results suggest that dissolution of the 8.9% initial porosity core opened a substantial number of isolated pores, exposing new quartz grain surfaces to dissolution.  相似文献   

Laboratory Kinetic Studies of the Reactions of Cl Atoms with Species of Biogenic Origin: δ3-Carene, Isoprene, Methacrolein and Methyl Vinyl Ketone     

Carlos E. Canosa-Mas  Hilary R. Hutton-Squire  Martin D. King  David J. Stewart  Katherine C. Thompson  Richard P. Wayne 《Journal of Atmospheric Chemistry》1999,34(1):163-170

The rate coefficients for the reaction between atomic chlorine and a number of naturally occurring species have been measured at ambient temperature and atmospheric pressure using the relative rate technique. The values obtained were (4.0 ± 0.8) × 10^-10, (2.1 ± 0.5) × 10^-10, (3.2 ± 0.5) × 10^-10, and (4.9 ± 0.5) × 10^-10 cm³ molecule^-1 s^-1, for reactions with isoprene, methyl vinyl ketone, methacrolein and ³-carene, respectively. The value obtained for isoprene compares favourably with previously reported values. No values have been reported to date for the rate constants of the other reactions.  相似文献   

An old old friend revisited     

Carlos L. Aiken  John R. Sturgul 《Mathematical Geosciences》1971,3(4):381-381

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Construction of a high-resolution gridded rainfall dataset for Peru from 1981 to the present day     

Cesar Aybar  Carlos Fernández  Adrian Huerta  Waldo Lavado  Fiorella Vega  Oscar Felipe-Obando 《水文科学杂志》2020,65(5):770-785

ABSTRACT

A new gridded rainfall dataset available for Peru is introduced, called PISCOp V2.1 (Peruvian Interpolated data of SENAMHI’s Climatological and Hydrological Observations). PISCOp has been developed for the period 1981 to the present, with an average latency of eight weeks at 0.1° spatial resolution. The merging algorithm is based on geostatistical and deterministic interpolation methods including three different rainfall sources: (i) the national quality-controlled and infilled raingauge dataset, (ii) radar-gauge merged precipitation climatologies and (iii) the Climate Hazards Group Infrared Precipitation (CHIRP) estimates. The validation results suggest that precipitation estimates are acceptable showing the highest performance for the Pacific coast and the western flank of the Andes. Furthermore, a meticulous quality-control and gap-infilling procedure allowed us to reduce the formation of inhomogeneities (non-climatic breaks). The dataset is publicly available at https://piscoprec.github.io/ and is intended to support hydrological studies and water management practices.  相似文献   

Metamorphic rocks of the Araya Peninsula,Eastern Venezuela     

Dr. Carlos Schubert 《International Journal of Earth Sciences》1971,60(4):1571-1600

Two grades of metamorphism, both subfacies of the greenschist facies of regional metamorphism, were mapped on the Araya Peninsula: 1. the quartzalbite-epidote-almandine subfacies, consisting mainly of a sequence of garnet and kyanite quartz-mica schists, interlayered with quartzites; and 2. the quartzalbite-muscovite-chlorite subfacies, which consists of chloritic phyllites, quartzmica schists and phyllites, metaconglomerates, calcareous quartz-mica schists, limestones and marbles, and calcareous epidote schists of volcanic origin. The two subfacies are separated by faults. The probable age of these rocks ranges from Triassic(?)-Jurassic to Lower and Middle Cretaceous. Serpentinites intrude rocks of the lower metamorphic grade, and are interpreted as tectonically emplaced. The foliation of these rocks is highly folded by mesoscopic folds, whose axes trend east-northeast and which are overturned to the south-southeast. Lineations parallel to the fold axes and thrusting to the south-southeast are common. These structures reflect a macroscopic structure of antiforms and synforms, all affected by a dominant north-northwest to south-southeast tectonic transport. A system of high-angle or vertical longitudinal faults crosses the peninsula from west-southwest to east-northeast. Evidence of recent strike-slip movement was found, although vertical movement has also been important along these faults. Two tectonic styles exist in the metamorphic rocks. The older one is characterized by compression and thrusting in a south-southeast direction. The younger one is represented by longitudinal faults oriented in an east-northeast direction, with vertical and strike-slip movement. They probably reflect the eastward movement of the Caribbean region with respect to South America.  相似文献   

Geological development and mineralization in the Atacama segment of the South American Andes,northern Chile (26°15′–27°25′S)     

Carlos M. Palacios  Brian C. Townley  Alfredo A. Lahsen  Antonio M. Egaña 《International Journal of Earth Sciences》1993,82(4):652-662

Between the Late Jurassic and the Middle Miocene, widespread magmatism, tectonic events and hydrothermal mineralization characterized the geological evolution of the Atacama segment of the South American Andes. A characteristic feature of this zone is the coincidence in time and space between subduction-generated igneous activity, crustal deformation and mineralization in the magmatic arcs, which formed longitudinal belts migrating eastward.Mineralization in the last 140 Ma is generally restricted to four longitudinal metallogenic belts, in which hydrothermal activity was channelled along crustal-scale faults (1) the Atacama Fault System, along which Early Cretaceous Cu-Au-bearing breccia pipes, veins and stockwork were formed; (2) the Inca do Oro Belt, which contains Upper Cretaceous low sulphur precious metal epithermal mineralization, and Middle Eocene Cu-Mo-Au-bearing breccia pipes; (3) the West Fissure System, which hosts Upper Eocene to Early Oligocene porphyry copper deposits and high sulphur precious metal epithermal mineralization; and (4) the Maricunga Belt, when contains Upper Oligocene to Middle Miocene high sulphur precious metal epithermal deposits and Au-rich porphyry mineralization.  相似文献   

Volcanic emissions and atmospheric pollution:A study of nanoparticles     

Erika M.Trejos  Luis F.O.Silva  James C.Hower  Eriko M.M.Flores  Carlos Mario González  Jorge E.Pachón  Beatriz H.Aristizábal 《地学前缘(英文版)》2021,12(2):746-755

The influence of emissions of an active volcano on the composition of nanoparticles and ultrafine road dust was identified in an urban area of the Andes.Although many cities are close to active volcanoes,few studies have evaluated their influence in road dust composition.Air quality in urban areas is significantly affected by nonexhaust emissions(e.g.road dust,brake wear,tire wear),however,natural sources such as volcanoes also impact the chemical composition of the particles.In this study,elements from volcanic emissions such as Si>Al>Fe>Ca>K>Mg,and Si-Al with K were identified as complex hydrates.Similarly,As,Hg,Cd,Pb,As,H,Cd,Pb,V,and salammoniac were observed in nanoparticles and ultrafine material.Mineral composition was detected in the order of quartz>mullite>calcite>kaolinite>illite>goethite>magnetite>zircon>monazite,in addition to salammoniac,a tracer of volcanic sources.The foregoing analysis reflects the importance of carrying out more studies relating the influence of volcanic emissions in road dust in order to protect human health.The road dust load(RD₁₀)ranged between 0.8 and 26.8 mg m^?2in the city.  相似文献   

Phase equilibrium modelling of the amphibolite facies metamorphism in the Yelapa-Chimo Metamorphic Complex,Mexico     

Fabian Gutierrez-Aguilar  Peter Schaaf  Gabriela Solís-Pichardo  Gerardo F.Arrieta-García  Teodoro Hernandez-Trevino  Carlos Linares-Lopez 《地学前缘(英文版)》2021,12(1):293-312

The Yelapa-Chimo Metamorphic Complex forms part of the Jalisco Block in western Mexico and exposes a wide range of Early Cretaceous metamorphic rocks;such as paragneiss,orthogneiss,amphibolites,and migmatites.However,the pressure-temperature(P-T)conditions of metamorphism and partial melting remain poorly studied in the region.To elucidate metamorphic P-T conditions,phase equilibrium modelling was applied to two sillimanite-garnet paragneisses,one amphibole-orthogneiss,and one amphibolite.Sillimanite-garnet paragneisses exhibit a lepidoblastic texture with a biotite+sillimanite+kyanite+garnet+quartz+plagioclase+K-feldspar mineral assemblage.Amphibole-orthogneiss and amphibolite display a nematoblastic texture with an amphibole+(1)plagioclase+quartz+(1)titanite assemblage and an amphibole+(2)plagioclase+(2)titanite+ilmenite retrograde mineral assemblage.Pseudosections calculated for the two sillimanite-garnet paragneiss samples show P-T peak conditions at~6-7.5 kbar and~725-740℃.The results for amphibole-orthogneiss and the amphibolite yield P-T peak conditions at~8.5-10 kbar and~690-710℃.The mode models imply that metasedimentary and metaigneous units can produce up to~20 vol%and~10 vol%of melt,respectively.Modelling within a closed system during isobaric heating suggests that melt compositions of metasedimentary and metaigneous units are likely to have direct implications for the petrogenesis of the Puerto Vallarta Batholith.Our new data indicate that the Yelapa-Chimo Metamorphic Complex evolved through a metamorphic gradient between~23-33℃km^-1and the metamorphic rocks formed at depths between~22 km and~30 km with a burial rate of~2.0 km Ma^-1.Finally,the P-T data for both metasedimentary and metaigneous rocks provide new constraints on an accretionary framework,which is responsible for generating metamorphism and partial melting in the YelapaChimo Metamorphic Complex during the Early Cretaceous.  相似文献