نتایج جستجو برای: crustal contamination
تعداد نتایج: 61183 فیلتر نتایج به سال:
The Yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world. An understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk. Using a joint local and teleseismic earthquake P-wave seismic inversion, we revealed a basaltic lower-crustal magma body that provides a magmatic link between the Yellowston...
Oxygen isotope data are reported for clinopyroxene phenocrysts from volcanic rock samples from Filicudi island, Italy, with the aim of investigating mechanisms of magma evolution and mantle source characteristics in a continental arc volcano. Filicudi rocks range from calc-alkaline basalt to high-K andesite and dacite. Mafic rocks have MgO 6-7 wt%, Mg# 60, Ni < 50 ppm and Cr < 200 ppm, suggesti...
Significant crustal movements were caused by the 2011 Tohoku, Japan Earthquake. A method for capturing the surface movements from TerraSAR-X intensity images is proposed in this study. First, the buildings were extracted from the preand post-event images using a segmentation approach. Then, the unchanged buildings were detected by matching the buildings in the preand post-event images at simila...
: Despite that, in the Alvand complex, the mafic-intermediate rocks (gabbros, diorites and tonalites) are mostly older than felsic rocks (granodiorites and monzogranites), and mineralogical and geochemical discontinuity is seen between them, there are evidence that indicate they have sometimes been co-existed. With the studies on field relationship of rocks, xenocrysts assemblages, synplutonic ...
Reducing scatter in measurements of regional-phase amplitude ratios is desirable for seismic discrimination applications and also provides insight into crustal structure controls on energy partitioning of regional seismic waves. Our previous analysis (Fan and Lay, 1998) of the regional seismic discriminant, Pg/Lg, indicated that variations in crustal structure cause path-specific fluctuations o...
The ongoing collision between the Indian plate and the Eurasian plate brings up N-S crustal shortening and thickening of the Tibet Plateau, but its dynamic mechanisms remain controversial yet. As one of the most tectonically active regions of the world, South-Eastern Tibet (SET) has been greatly paid attention to by many geoscientists. Here we present the latest three-dimensional GPS velocity f...
........................................................................................................................2 INTRODUCTION...............................................................................................................3 THE NATIONAL MAIZE ECONOMY.............................................................................4 GUATEMALA’S AGRICULTURE AND MAIN MAIZE PRODUC...
To directly access the sub-seafloor microbial communities, seafloor drilling has been done in a deep-sea hydrothermal field of the Suiyo Seamount, Izu-Bonin Arc, Western Pacific. In the present study, crustal fluids were collected from the boreholes, and the bacterial and archaeal communities in the fluids were investigated by culture-independent molecular analysis based on 16S rRNA gene sequen...
Crustal rejuvenation is a key process that has shaped the characteristics of current continental structures and components in tectonic active continental regions. Geological and geochemical observations have provided insights into crustal rejuvenation, although the crustal structural fabrics have not been well constrained. Here, we present a seismic image across the North China Craton (NCC) and...
[1] We estimate crustal structure and thickness of South America north of roughly 40°S. To this end, we analyzed receiver functions from 20 relatively new temporary broadband seismic stations deployed across eastern Brazil. In the analysis we include teleseismic and some regional events, particularly for stations that recorded few suitable earthquakes. We first estimate crustal thickness and av...
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