Search results for "BELT"
showing 10 items of 204 documents
Constrains on mantle, slab and crustal contributions to major volatiles and noble gases along the Andean Volcanic Belt
2020
Isothermal decompression history in the “Western Granulite” terrain, central Tanzania: Evidence from reaction textures and trapped fluids in metapeli…
2008
Abstract The Mozambique Belt (MB) of the East Africa Orogen contains large areas of granulite-facies migmatitic gneisses with Archaean and Palaeoproterozoic protolith ages and that were recycled during the Neoproterozoic Pan-African orogeny. The study area is situated along the Great Ruaha River and within the Mikumi National Park in central Tanzania where migmatitic gneisses and mafic to intermediate granulites are interlayered with Neoproterozoic granulite-facies migmatitic metapelites. Mineral textures suggest isothermal decompression, with the peak mineral assemblage comprising Grt–Bt–Ky–Kfs–Pl–Qtz ± Phn ± Ti-Oxide ± melt and amphibolite-facies retrograde assemblage Grt–Bt–Sil–Ms–Kfs–Pl…
Padure (Beltes) piliakalnio (Latvija) osteologinė medžiaga: rūšių pasiskirstymas ir skerdimo technologija
2013
In the excavated Padure (Beltes) hill-fort in Latvia, cultural layers from the Late Bronze Age and the Early Iron Age (Stage 1), and the Middle Iron Age and the Late Iron Age (Stage 2), were detected, which, besides the archaeological material typical of that period, provided abundant zooarchaeological material. This article presents the investigation data from the zooarchaeological material of both stages: the data relate to the butchering techniques used, and the identification of the composition of the faunal species. The investigation was carried out in the bioarchaeological laboratory of the Institute of Baltic Region History and Archaeology at Klaipėda University. As is proven by the …
On the Co-Occurrence of Warm Conveyor Belt Outflows and PV Streamers
2014
Abstract The co-occurrence of warm conveyor belts (WCBs), strongly ascending moist airstreams in extratropical cyclones, and stratospheric potential vorticity (PV) streamers, indicators for breaking Rossby waves on the tropopause, is investigated for a 21-yr period in the Northern Hemisphere using Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) data. WCB outflows and PV streamers are respectively identified as two- and three-dimensional objects and tracked during their life cycle. PV streamers are more frequent than WCB outflows and nearly 15% of all PV streamers co-occur with WCBs during their life cycle, whereas about 60% of all WCB outflows co…
Ko atklāj Ķīnas Ceļa un jostas iniciatīvas investīcijas? Nestriktas kopas kvalitatīvā salīdzinošā analīze
2020
Maģistra darbā “Ko atklāj Ķīnas Ceļa un jostas iniciatīvas investīcijas? Nestriktas kopas kvalitatīvā salīdzinošā analīze” tika analizēts Ķīnas Ceļa un jostas iniciatīvas (BRI) investīciju daudzums 78. Eirāzijas valstīs, lai noteiktu, kādi valstis raksturojoši faktori vai apstākļi ietekmē to vēlmi pievienoties BRI. Izvēlētajām valstīm pēc detalizētas pētnieciskās literatūras analīzes tika noteikti astoņi investīcijas veicinošie faktori (gan politiskie, gan ekonomiskie). Izvēlētie faktori tika pretnostatīti Ķīnas BRI investīciju apjomam uz vienu iedzīvotāju konkrētā valstī, lai varētu secināt, kādi valsti raksturojoši apstākļi un priekšnoteikumi veicina Ķīnas BRI investīciju plūsmu uz konkrē…
Backthrusts and passive roof duplexes in fold-and-thrust belts. The case of Central-Western Sicily based on seismic reflection data
2012
Seismic reflection profiles crossing the area bounded by the M. Kumeta Ridge and the M. Maranfusa-M. Galiello-Rocca Busambra morphostructural feature (central-western Sicily) were used to constrain the deep structural setting of the Sicilian-Maghrebian fold-and-thrust belt (FTB). By integrating seismic, field and well data, we attempted to correlate outcropping and deep-seated contractional structures, shedding light on the internal geometries of the thrust system. Results of the new seismostratigraphic analysis presented in this paper reveal structural variations along the tectonic edifice. This suggests dividing the study area into two sectors: the western sector is characterized by forel…
Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa)
2019
A well-preserved sequence, by Archean standards, of mantle-derived metabasalts and metakomatiites forms large parts of the lower Onverwacht Group of the Barberton Greenstone Belt (South Africa). To elucidate the origin of mafic and ultramafic rocks from this 3.55 to 3.45 Ga sequence, we present a comprehensive geochemical dataset including major and trace elements as well as Lu-Hf and Sm-Nd isotope compositions for a variety of metavolcanic rocks. These include metabasalts of the amphibolite-facies Sandspruit and Theespruit Formations as well as metabasalts and metakomatiites of the lower greenschist-facies Komati Formation. Based on their incompatible trace element patterns, the basalts of…
Coupled silicon-oxygen isotope fractionation traces Archaean silicification
2011
International audience; Silica alteration zones and cherts are a conspicuous feature of Archaean greenstone belts worldwide and provide evidence of extensive mobilisation of silica in the marine environment of the early Earth. In order to understand the process(es) of silicification we measured the silicon and oxygen isotope composition of sections of variably silicified basalts and overlying bedded cherts from the Theespruit, Hooggenoeg and Kromberg Formations of the Barberton Greenstone Belt, South Africa.The δ30Si and δ18O values of bulk rock increase with increasing amount of silicification from unsilicified basalts (-0.64‰ 30Si 18O 30Si and δ18O values as high as + 0.81‰ and + 15.6‰, r…
GEOCHEMICAL CONSTRAINTS ON THE ORIGIN OF CALCALKALINE AND ALKALINE MAGMAS OF THE EASTERN TRANS-MEXICAN VOLCANIC BELT
1988
Se presentan datos de elementos mayores, elementos trazas y tierras raras de rocas calco-alcalinas y alcalinas de la parte este del cinturón volcánico transmexicano (TMVB), así como conclusiones acerca de su origen y de su significado tectónico. Las andesitas y dacitas muestran características geoquímicas que descartan su derivación de los magmas basálticos por el proceso de cristalización fraccionada. Las distribuciones gráficas de los elementos LIL y HFS son interpretadas como indicadoras de la formación de magmas en el manto superior modificado por procesos de subducción. Las riolitas se interpretan como resultado de la fusión parcial de la corteza continental.
Generation of early Archaean felsic greenstone volcanic rocks through crustal melting in the Kaapvaal, craton, southern Africa
2013
Abstract High-potassium felsic volcanic rocks interlayered with basalt and komatiite in early Archaean greenstone sequences in the Barberton Greenstone Belt of South Africa and Swaziland, previously considered to be derived from melting of mafic precursors, are shown to be the result of melting of significantly older felsic crust. This is documented by a combination of SHRIMP zircon dating with Hf-in-zircon and whole-rock Lu–Hf and Sm–Nd isotopic data. Zircons from felsic rocks of the oldest Barberton unit, the 3.53 Ga Theespruit Formation, yielded predominantly negative e Hf ( t ) -values, whereas whole-rock e Hf ( t ) - and e Nd ( t ) -data are slightly negative to slightly positive. Simi…