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61.
Abdurrahman Dokuz Erkan Tanyolu Salim Genç 《International Journal of Earth Sciences》2006,95(3):370-394
The Yusufeli area, in the Eastern Black Sea Region of Turkey, contains a crystalline complex that intruded into the Carboniferous metamorphic basement and is composed of two intrusive bodies: a gabbro-diorite and a tonalite-trondhjemite. The mafic body (45–57 wt% SiO2) displays a broad lithological spectrum ranging from plagioclase-cumulate to quartz diorite. Primitive varieties of the body have Mg-number, MgO and Cr contents that are close to those expected for partial melts from mantle peridotite. Data are consistent with the magma generation in an underlying mantle wedge that was depleted in Zr, Nb and Ti, and enriched in large ion lithophile elements (K, Rb, Ba, Th). However, high Al2O3, CaO and generally low Ni (<65 ppm) contents are not in agreement with the unfractionated mantle-derived primitive magmas and require some Al2O3- and CaO-poor mafic phases, in particular, olivine and orthopyroxene. Absence of orthopyroxene in crystallization sequence, uralitization, and a common appearance of clinopyroxene surrounded by hornblende imply an anhydrous phase fractionated from highly hydrous (5–6%) parent. Geochemical modelling suggests derivation by 15–20% melting of a depleted-lherzolitic mantle. The tonalite-trondhjemite body (58–76 wt% SiO2) ranges in composition from quartz diorite to granodiorite with a low-K calc-alkaline trend. Although LILE- and LREE- enriched characteristics of the primitive samples imply a metasomatic sub-arc mantle for their source region, low MgO, Ni and Cr concentrations rule out direct derivation from the mantle wedge. Also, lack of negative Eu anomalies suggests an unfractionated magma and precludes a differentiation from the diorites of mafic body, which show negative Eu anomalies. Their Na enrichments relative to Ca and K are similar to those of Archean tonalites, trondhjemites and granodiorites and Cenozoic adakites. However, they exhibit important geochemical differences from them, including low-Al (<15 wt%) contents, unfractionated HREE patterns and evolution towards the higher Y concentrations and lower Sr/Y ratios within the body. All these features are obtained in experimentally produced melts from mafic rocks at low pressures (≤5 kbar) and also widespread in the rocks of arc where old (Upper Cretaceous or older) oceanic crust is being subducted. Major and REE modelling supports formation of the quartz dioritic parent to the felsic intrusive rocks by 70% partial melting of a primitive gabbroic sample (G694). Therefore, once taking into account the extensional conditions prevailing in the Pontian arc crust in Early Jurassic time, former basic products (gabbros) seem to be the most appropriate source for the tonalite-trondhjemite body. Magmatic emplacement of stratigraphically similar lithologies in the Pulur Massif, just southwest of the Yusufeli, was dated to be 184 Ma by the 40Ar/39Ar method on amphibole, and is compatible with the initiation of Early Jurassic rifting in the region. 相似文献
62.
Karim Saheb Ettabaa Manel Ben Salem Med Salim Bouhlel 《Arabian Journal of Geosciences》2017,10(18):412
Segmentation-based anomaly detectors proceeds to the clustering of the hyperspectral image as a first step. However, most of the well-known clustering methods cluster anomalous pixels as a part of the background. This paper presents a new hyperspectral image clustering approach based on the betweenness centrality measure. The proposed approach starts by the construction of an adaptive spatial and spectral neighborhood for each pixel. This neighborhood is based on the selection of the nearest spectral and spatial neighbors in multiple windows around each pixel to allow well-suited representation of the image features. In the next step, this neighborhood is clustered based on the edge betweenness measure algorithm that splits the image into regions sharing similar features. This approach (1) allows the reduction of intercluster relationship, (2) favors intracluster relations, and (3) preserves small clusters that can hold anomalous pixels. Experimental results show that the proposed approach is efficient for clustering and overcomes the state of the art approaches. 相似文献
63.
Saif Salim Al-Qaydi 《GeoJournal》1999,47(4):583-586
Within universities there has developed a clear theoretical convergence between Geographical Information Systems (GIS) and
geography (Antenuccl, 1991). Studies have revealed that one of the qualified departments to teach GIS within universities
is the geography department. This study focuses on: the importance of establishing GIS as a major curriculum element within
universities. In geography departments, economic geography students require a strong statistical/mathematical background to
allow them to work with major databases. They should know how to design a specific database for economic activities, such
as agriculture and manufacturing, and tertiary industry and how to relate this database to a map, so that changes can be monitored
more accurately. In any aspect of geography spatial location is a key factor and GIS allows spatial patterns to be interpreted
with great facility. Therefore it is important that students have a good knowledge not only of computers and related software
on economic geography, but also on GIS systems (Burrough, 1993). The work of geography students from the United Arab Emirates
(UAE) and other Gulf Co-operation Council (GCC) geography departments is examined to evaluate the importance of training in
GIS technology. This paper evaluates the effects of implementing GIS as a tool in teaching economic geography. At present
there are 15 geography departments in the GCC which offer economic geography. Of those 15 departments, only 3 provide GIS
courses within their curriculum, and 4 have basic equipment, although 6 additional departments are to introduce GIS in the
near future.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
64.
Wahyudi A’an J. Rahmawati Susi Irawan Andri Hadiyanto Hadiyanto Prayudha Bayu Hafizt Muhammad Afdal Afdal Adi Novi S. Rustam Agustin Hernawan Udhi. E. Rahayu Yusmiana P. Iswari Marindah Y. Supriyadi Indarto H. Solihudin Tubagus Ati Restu Nur Afi Kepel Terry L. Kusumaningtyas Mariska A. Daulat August Salim Hadiwijaya L. Sudirman Nasir Suryono Devi D. Kiswara Wawan 《Ocean Science Journal》2020,55(1):85-97
Ocean Science Journal - Seagrass meadows provide critical ecosystem services for coastal areas, e.g., as nursery habitats for various fish species, help with water filtration of suspended sediment,... 相似文献