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21.
An Example of Island-Arc Petrogenesis: Geochemistry and Petrology of the Southern Luzon Arc, Philippines 总被引:7,自引:1,他引:6
DEFANT MARC J.; MAURY REN? C.; RIPLEY EDWARD M.; FEIGENSON MARK D.; JACQUES DARIO 《Journal of Petrology》1991,32(3):455-500
Volcanism throughout the Luzon arc is associated with eastwardsubduction of the South China Sea floor along the Manila Trench.The southern section of the arc, the focus of this study, extendsfrom the Lingayen-Dingalan fault to the small islands just southof Luzon. Two segments appear to exist along this section ofthe arc the northern Bataan and southern Mindoro segments whichare separated by the Macolod Corridor. The volcanic rocks have typical arc phenocryst mineralogies:olivine, clinopyroxene, plagioclase, and titanomagnetite inthe most mafic rocks and clinopyroxene, plagioclase, orthopyroxene,titanomagnetite, ? amphibole in the more felsic samples. Complexzoning, sieve textures, and decoupling of incompatible traceelements suggest that processes such as assimilation have takenplace. The rocks from the study area range from basalts to rhyolitesand show typical calc-alkaline features. The rocks of the MacolodCorridor and Mindoro segment are particularly enriched in largeion lithophile elements (LILE), light rare earth elements (LREE),and radiogenic Sr compared with the Bataan segment. The datafall within the mantle array on Sr-Nd isotopic diagrams andgrade toward higher Sr and lower Nd isotopic values from northto south. A likely source for the volcanics of this study is either amid-ocean ridge basalt (MORB)-type mantle that undergoes higherdegrees of partial melting than regions involved in MORB generationor a previously depleted source. We suggest that the high fieldstrength element (HFSE) anomalies have been derived throughdifferential element partitioning during fluid transport fromthe subducted lithosphere to the mantle wedge. Continental crustal material seems to play a significant roleparticularly in the Macolod Corridor and the Mindoro segment,based on the high LILE, La/Sm ratios, radiogenic Sr isotopes,and 18O values. The Macolod Corridor and the Mindoro segmenthave undergone source contamination by crustal material fromthe North Palawan-Mindoro crustal block either during the collisionof this block with the Manila Trench or by subduction of sedimentsrich in this crustal material. A similar component has alsobeen detected in the Bataan segment but in minor amounts. Thetrace element and isotopic differences between the northernand southern sections of the arc are interpreted in terms ofvariable composition (i. e., variable amounts of a crustal componentintroduced from the Palawan-Mindoro crustal terrain) of themetasomatic fluids released into the source. 相似文献
22.
The influence of compressibility of media on both the statistical acceleration and the turbulent diffusion of cosmic-ray particles is investigated. The averaging over an ensemble of random velocity fields of the medium was performed in the kinetic equation. The kinetic coefficients, which are responsible for the particle acceleration, were obtained in the cases of weak and strong scattering due inhomogeneous magnetic fields. 相似文献
23.
Vladmír Skalský 《Astrophysics and Space Science》1991,181(2):313-322
The Friedmannian model of the Universe with ultra-relativistic equation of statep=–1/3 withk=0 is nondecelerative, i.e., it expands with the constant velocityv=c during the whole expanding phase of evolution of the Universe. The ultrastable nondecelerative model is the only model of the Universe which fulfills all conditions resulting from the quantum-mechanical and relativistic analysis of the Universe. 相似文献
24.
The 5-dimensional Jordan-Brans-Dicke cosmologies in vacuum are found for the Bianchi type I metric, their relation with general relativity cosmologies is studied. Two solutions are possible, both produce effective pressure and energy density in the 4-dimensional G.R.-universes. One is a power-law relation, with two cases, the first one is forp
eff=eff and the other forp
eff=eff(– 1 < < 1) has a behaviour as the open flat universe. The second solution is an exponential only valid forp
eff=–eff. In all cases the three-space expansion reaches infinity ast and the fifth dimension can be made to decrease approaching zero. The scalar field can increase or decrease with time. 相似文献
25.
On the coronograph spectrophotographic records taken on 31.372 UT, August 1979, some faint emission features were found which can be ascribed to Siii and Niii. These emissions were obviously a transient phenomena which were detected only 10 hr after the supposed fall of Comet 1979 XI in the Sun's photosphere. It cannot be excluded that the appearance of Si and Ni lines was triggered by the evaporation of dust particles with a high abundance of heavier elements in the solar corona. This assumption is also supported by intensity distribution of the Fex coronal line around the Sun's limb. The maximum coincide with the position angle of the projected path of the comet. 相似文献
26.
Verónica Oliveros Gilbert Féraud Luis Aguirre Luis Ramírez Michel Fornari Carlos Palacios Miguel Parada 《Mineralium Deposita》2008,43(3):281-293
The 40Ar/39Ar geochronological method was applied to date magmatic and hydrothermal alteration events in the Mantos Blancos mining district
in the Coastal Cordillera of northern Chile, allowing the distinction of two separate mineralization events. The Late Jurassic
Mantos Blancos orebody, hosted in Jurassic volcanic rocks, is a magmatic-hydrothermal breccia-style Cu deposit. Two superimposed
mineralization events have been recently proposed. The first event is accompanied by a phyllic hydrothermal alteration affecting
a rhyolitic dome. The second mineralization event is related to the intrusion of bimodal stocks and sills inside the deposit.
Because of the superposition of several magmatic and hydrothermal events, the obtained 40Ar/39Ar age data are complex; however, with a careful interpretation of the age spectra, it is possible to detect complex histories
of successive emplacement, alteration, mineralization, and thermal resetting. The extrusion of Jurassic basic to intermediate
volcanic rocks of the La Negra Formation is dated at 156.3 ± 1.4 Ma (2σ) using plagioclase from an andesitic lava flow. The first mineralization event and associated phyllic alteration affecting
the rhyolitic dome occurred around 155–156 Ma. A younger bimodal intrusive event, supposed to be equivalent to the bimodal
stock and sill system inside the deposit, is probably responsible for the second mineralization event dated at ca. 142 Ma.
Other low-temperature alteration events have been dated on sericitized plagioclase at ca. 145–146, 125, and 101 Ma. This is
the first time that two distinct mineralization events have been documented from radiometric data for a copper deposit in
the metallogenic belt of the Coastal Cordillera of northern Chile.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
27.
28.
A modified method of mine tremors location used in Lubin Copper Mine is presented in the paper. In mines where an intensive exploration is carried out a high accuracy source location technique is usually required. The effect of the flatness of the geophones array, complex geological structure of the rock mass and intense exploitation make the location results ambiguous in such mines. In the present paper an effective method of source location and location's error evaluations are presented, combining data from two different arrays of geophones. The first consists of uniaxial geophones spaced in the whole mine area. The second is installed in one of the mining panels and consists of triaxial geophones. The usage of the data obtained from triaxial geophones allows to increase the hypocenter vertical coordinate precision. The presented two-step location procedure combines standard location methods: P-waves directions and P-waves arrival times. Using computer simulations the efficiency of the created algorithm was tested. The designed algorithm is fully non-linear and was tested on the multilayered rock mass model of the Lubin Copper Mine, showing a computational better efficiency than the traditional P-wave arrival times location algorithm. In this paper we present the complete procedure that effectively solves the non-linear location problems, i.e. the mine tremor location and measurement of the error propagation. 相似文献
29.
Mirta Garrido Fernando Barra Eduardo Domínguez Joaquin Ruiz Victor A. Valencia 《Mineralium Deposita》2008,43(5):591-597
The La Voluntad porphyry Cu–Mo deposit in Neuquén, Argentina, is one of several poorly known porphyry-type deposits of Paleozoic
to Early Jurassic age in the central and southern Andes. Mineralization at La Voluntad is related to a tonalite porphyry from
the Chachil Plutonic Complex that intruded metasedimentary units of the Piedra Santa Complex. Five new Re–Os molybdenite ages
from four samples representing three different vein types (i.e., quartz–molybdenite, quartz–sericite–molybdenite and quartz–sericite–molybdenite
± chalcopyrite–pyrite) are identical within error and were formed between ~312 to ~316 Ma. Rhenium and Os concentrations range
between 34 to 183 ppm and 112 to 599 ppb, respectively. The new Re–Os ages indicate that the main mineralization event at
La Voluntad, associated to sericitic alteration, was emplaced during a time span of 1.7 ± 3.2 Ma and that the deposit is Carboniferous
in age, not Permian as previously thought. La Voluntad is the oldest porphyry copper deposit so far recognized in the Andes
and indicates the presence of an active magmatic arc, with associated porphyry style mineralization, at the proto-Pacific
margin of Gondwana during the Early Pennsylvanian. 相似文献
30.
Soil contamination from urban and industrial activity: example of the mining district of Linares (southern Spain) 总被引:1,自引:0,他引:1
J. Martínez J. F. Llamas E. de Miguel J. Rey M. C. Hidalgo 《Environmental Geology》2008,54(4):669-677
The Linares region (southern Spain) has been subjected to two important sources of pollution: the intensive mining works and
the urban-industrial activity. To obtain a geochemical characterisation of the soil, 31 trace elements were analysed and 669
soil samples were collected. By means of clustering analysis, we identified groups of elements and grid squares in which relations
could be established concerning soil lithology, urban and industrial activities and the degree of pollution impact; in addition,
we were able to characterise the geochemical background of the study area. The multivariate study led us to identify four
factors. Particularly important was factor 2, which represented the elements associated with mineral paragenesis (Cu, Pb,
As, Co, Mn, Zn, Sn, Ba). This factor also contains elements related with an urban-industrial activity, such as Pb, Cu, Zn,
As and Ba. Furthermore, we identified factor 4, associating Ni, V and Cr, and which is related to the use of fuels. 相似文献