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2021 ◽  
Vol 8 (2021) (1) ◽  
pp. 1-34
Author(s):  
Josiane SANTOS ◽  
◽  
Marcondes COSTA ◽  
José Francisco SILVA ◽  
◽  
...  

The techniques of investigation of heavy minerals using new analytical instruments were used to evaluate the contribution of the Barreiras Formation sediments as source material of the sediments of the Marapanim River estuary, in the northeast of Pará: bottom sediments and muddy plains (mangroves, mainly). The most suitable granulometric fraction is very fine sand, where they stood out in decreasing order of abundance: zircon, tourmaline, staurolite, kyanite and rutile, besides sillimanite, andalusite and amphibole. The frequency of these minerals, morphological aspects, inclusions, cavities, fractures indicate that the Barreiras Formation is the main source of these minerals. However, the semi-quantitative chemical data show that there seems to be an external contribution, perhaps from the sediments of the continental platform.


2021 ◽  
pp. 118481
Author(s):  
A. Viney ◽  
J.F. Nicolás ◽  
N. Galindo ◽  
J. Fernández ◽  
V. Soriano-Gomis ◽  
...  

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 304
Author(s):  
Hairui Sun ◽  
Zhilong Huang ◽  
Zhicheng Lü ◽  
Xiaofei Yu ◽  
Yongsheng Li

The Great Hinggan Range (GHR) hosts many large Mo deposits and vein-type Pb-Zn deposits and is one of the most important polymetallic metallogenic belts in China. Although Mo and Pb-Zn deposits are locally closely related in space in the GHR, it is disputed whether the Mo and Pb-Zn deposits have a genetic relationship. The Diyanqinamu Mo deposit located at the middle part of the northern GHR is a Late Jurassic large porphyry Mo deposit and closely adjacent by vein-type Pb-Zn deposit. In this work, we discussed the relationship between Mo and Pb-Zn deposits in Diyanqinamu mine based on the data of S and Pb isotopic geochemistry and geological information. In this mine, the Mo deposit is concentrated in the southern area with a distance of 500 m to the vein Pb-Zn deposit. The δ34SCDT values of the galena and sphalerite from the Mo deposit range from +1.73‰ to +7.29‰ with average of +5.04‰. By contrast, δ34SCDT values of the galena and sphalerite from the Pb-Zn deposit, ranging from +2.38‰ to +5.46‰ with average of +4.04‰, is similar to that of the Mo deposit. The formation temperatures of the Pb-Zn deposit calculated based on the sulfur isotope balance fractionation between sphalerite and co-existed galena range from 220 °C to 315 °C (average 247 °C), which is lower than that of the Mo mineralization (292–510°C). Pb isotopic results show that the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of the Pb-Zn deposit range from 18.326–18.364, 15.541–15.589, and 38.054–38.214, respectively, which are slightly higher than those of the Mo deposit ranging from 18.287–18.331, 15.532–15.569, and 38.034–38.139, respectively. In the 206Pb/204Pb˗207Pb/204Pb diagram, sulfides sampled from the Mo and Pb-Zn deposits overlapped with each other and formed a linear distribution, indicating that they are derived from a mixed metal source with more external contribution to the Pb-Zn mineralization. This mixed signal is further confirmed by the geologic facts that the host rocks of the vein-type Pb-Zn deposit have abnormally high contents of Pb, Zn, and Ag, and experienced strong hydrothermal alteration. Combined with the ore geology, mineral assemblage, and isotopic geochemistry of the two types of mineralization, we propose that the Mo and Pb-Zn deposits in the Diyanqinamu mine represent different faces of the same porphyry system. This Mo-Pb-Zn metallogenic system would provide important clues on further prospecting of Mo and Pb-Zn resources in the GHR.


2016 ◽  
Vol 23 (1) ◽  
pp. 187-199 ◽  
Author(s):  
José María López Morales ◽  
María Jesús Such Devesa

Tourism is among the most important activities in the Spanish economy, with Spain being one of the most significant tourism destinations worldwide. The external contribution of the international demand for tourism in Spain is a factor that must be taken into account, particularly when assessing the cyclical behaviour of tourism activities and therefore the contribution made by this sector to the overall economy. For this reason, the article examines the evolution of tourism in Spain during recent years, its contribution to economic growth and its level of external dependence using an analysis methodology which examines the cyclicality of the demand for the economy and the primary components of tourism.


2016 ◽  
Vol 59 (3) ◽  
Author(s):  
Bejo Duka ◽  
Eni Duka ◽  
Klaudio Peqini

<p>The differences between monthly mean values of the observed geomagnetic field and monthly values predicted by different models of the internal geomagnetic field (named “model biases”) for the time period 2000-2015 at several geomagnetic observatories are analyzed. We notice that increasing the maximum degree of the model is not always followed by the decrease of such “model bias”. The time series of these “model biases” reduced by their average resulted to be approximately the same for all models and should represent the external (non-modeled) contribution to the observed geomagnetic field. These time series for different observatories (close or away to each other) are compared and their power spectra are analyzed. Such spectra have common features like the annual and semi-annual variation with some possible sporadic cases of seasonal variation.</p>


2013 ◽  
Vol 458-460 ◽  
pp. 459-465 ◽  
Author(s):  
Alberto Maurizi ◽  
Felicita Russo ◽  
Francesco Tampieri

2013 ◽  
Vol 55 (6) ◽  
Author(s):  
Roberta Tozzi ◽  
Guido Dominici ◽  
Paola De Michelis ◽  
Antonio Meloni

<p>The influence of solar activity on magnetic measurements taken during the Italian repeat station surveys performed in 1999/2000 and 2009/2010 has been investigated. A method to estimate the difference between the 2000.0 and 2010.0 surveys in terms of the "residual" (i.e. not completely reduced) external contribution is proposed. This method is also based on the removal of the contribution due to the magnetic field of internal origin by means of CHAOS3 model from magnetic repeat station measurements. The origin of the observed differences is interpreted in terms of the very different level of solar activity between 2000.0 and 2010.0. Indeed, results seem to suggest that differences could be attributed to the enhanced ring current intensity during a phase of solar maximum. The investigation of the spatial patterns of these differences suggests that they could be reduced by introducing a larger number of variometer stations, especially during surveys performed under conditions of high solar activity.</p>


2009 ◽  
Vol 46 (11) ◽  
pp. 791-800 ◽  
Author(s):  
David C. Evans ◽  
Rebecca Bavington ◽  
Nicolás E. Campione

The lambeosaurine hadrosaurid Parasaurolophus is known from rare occurrences in Campanian deposits of western North America. A previously undescribed large hadrosaurid braincase from the Dinosaur Park Formation (Alberta, Canada) is assigned to the genus Parasaurolophus on the basis of several derived characters associated with the frontal–nasal articulation at the base of the crest. This identification is supported by two separate phylogenetic analyses, in which the specimen clusters with other more completely known Parasaurolophus exemplars. If correctly identified, the specimen represents the third and largest cranial specimen of the genus from the Late Cretaceous of Alberta. The specimen occurs in the same deposits as the holotype specimen of Parasaurolophus walkeri and may represent a late ontogenetic stage of this taxon. As opposed to a small frontal dome in the holotype of P. walkeri , the external contribution of the frontal to the skull roof is obliterated in the new specimen. If these hypothesized ontogenetic changes in the skull roof correlate with the size and posterodorsal development of the crest, as in other lambeosaurines, it suggests that the crest had not reached its full expression in the holotype. When placed into a detailed biostratigraphic context for the first time, the limited Parasaurolophus material from the Belly River Group is distributed in the lower half of the Dinosaur Park Formation at Dinosaur Provincial Park. This suggests that Parasaurolophus may be associated with the lower Centrosaurus – Corythosaurus assemblage zone and may have preferred more inland environments than other hadrosaurids, such as Lambeosaurus and Prosaurolophus .


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