Search results for "BELT"

The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation

2017

Ortiz, José Luis et. al.

Noble gas magmatic signature of the Andean Northern Volcanic Zone from fluid inclusions in minerals

2021

Trace volatile elements like He are key for understanding the mantle source signature of magmas and to better constrain the relative roles of subduction and crustal processes to the variability of along-arc chemical and isotopic signatures of magmatic fluids. Here we report on noble gas abundances and isotopic data of Fluid Inclusions (FIs) in eruptive products and/or fumarolic gases from the Colombia-Ecuador segment of Andean Northern Volcanic Zone (NVZ). FIs in olivine phenocrysts from Ecuador (El Reventador, Cotopaxi and Tungurahua) yield air-normalized corrected He-3/He-4 ratios of 7.0-7.4 R-A, within the MORB range (8 +/- 1 R-A). With exception of the Cotopaxi lavas (opx = 50 km at the…

The oldest granite clast in the Moodies conglomerate, Barberton greenstone belt, South Africa, and its likely origin

2018

Igneous petrology, zircon geochronology and geochemistry of multiply emplaced granitoid bodies from the Palaeoproterozoic Usagaran domain in central …

2019

Abstract This study reports igneous petrology, zircon ages and geochemistry for Palaeoproterozoic I-type granitic, granodioritic, Qtz-monzonitic, Qtz-monzodioritic and monzodioritic rocks from the Usagaran domain of southwestern Tanzania. These rocks can be subdivided into three groups according to their age, T-t evolution and geochemistry. The oldest group is made up of amphibolite-facies calcic-alkalic gneisses, ranging in age between ∼1984 and ∼1910 Ma, which have been divided into two subgroups regarding their T-t evolution. The first subgroup shows a constant increase in T, and the second subgroup first shows a decrease in T, followed by an increase in T. The second group consists of a…

Neoproterozoic eclogite- to high-pressure granulite-facies metamorphism in the Mozambique belt of east-central Tanzania: A petrological, geochemical …

2017

Abstract This study investigated Neoproterozoic (Pan-African) eclogite- and high-pressure-granulite (E-HPG) facies rocks from the Mozambique belt of east-central Tanzania, collected close to the town of Ifakara and the adjacent Furua area from different tectonic settings, the Palaeoproterozoic Usagaran and the Neoproterozoic Mozambique belt. The studied rocks are E-HPG facies granite- and diorite-gneisses and a meta-gabbroic rock, which are retrogressed to amphibolite- and greenschist-facies conditions. Four different clockwise P-T paths were constructed. The first P-T path for a granodioritic gneiss displays peak metamorphic conditions at ~ 830 °C and ~ 13.0 kbar. The second P-T path for a…

New P-T-X conditions for the formation of gem tsavorite garnet in the Voi area (southwestern Kenya)

2018

International audience; Tsavorite nodules-bearing deposits from southwestern Kenya are located in the Kurase Group, a metasedimentary unit of the Neoproterozoic Metamorphic Mozambique Belt. This unit is composed of graphitic paragneisses intercalated with metacarbonates and metaevaporites, surrounded by migmatites. The rocks underwent high grade metamorphism at 615-600 Ma. The main goal of this work is to link tsavorite formation to the metamorphic evolution of the Kurase Group. The new thermobarometric data indicate widespread granulite facies conditions at 800 +/- 50 degrees C and 10 +/- 1 kbar, with no significant difference between the tsavorite-bearing metasediments and the surrounding…

Active tectonics along the south east offshore margin of Mt. Etna: New insights from high-resolution seismic profiles

2018

The offshore margin of Mt. Etna has been shaped by Middle Pleistocene to Holocene shortening and extension and, more recently, by gravity-related sliding of the volcanic edifice. These processes have acted contemporaneously although the gravitational component largely prevails over the tectonic one. In order to investigate this issue, we focused on the main role of active tectonics along the south-eastern offshore of Mt. Etna by means of marine high-resolution seismic data. Seismic profiles revealed post-220 ka sedimentary deposits unconformably overlaying the Lower-Middle Pleistocene Etnean clayey substratum and volcanics of the Basal Tholeiitic phase and the Timpe phase. Offshore Aci Trez…

Thermal and structural modeling of the Scillato wedge-top basin source-to-sink system. Insights into the Sicilian fold-and-thrust belt evolution (Ita…

2019

AbstractTemperature-dependent clay mineral assemblages, vitrinite reflectance, and one-dimensional (1-D) thermal and three-dimensional (3-D) geological modeling of a Neogene wedge-top basin in the Sicilian fold-and-thrust belt and its pre-orogenic substratum allowed us to: (1) define the burial history of the sedimentary succession filling the wedge-top basin and its substratum, (2) reconstruct the wedge-top basin geometry, depocenter migration, and sediment provenance through time in the framework of a source-to-sink system, and (3) shed new light into the kinematic evolution of the Apennine-Maghrebian fold-and-thrust belt.The pre-orogenic substratum of the Scillato basin shows an increase…

Age and sedimentary record of inland eolian sediments in Lithuania, NE European Sand Belt

2015

We present a study based on four inland eolian locations in Eastern, Central and Southeastern Lithuania belonging to the northeastern part of the ‘European Sand Belt’ (ESB). Although there have been several previous studies of the ESB, this north-eastern extension has not been investigated before in any detail. The sedimentary structural–textural features are investigated and a chronology was derived using optically stimulated luminescence on both quartz and feldspar. The sedimentary structures and the rounding and surface characteristics of the quartz grains argue for a predominance of eolian transport. Additionally, some structural alternations and a significant contribution of non-eolian…

The north-eastern aeolian ‘European Sand Belt’ as potential record of environmental changes: A case study from Eastern Latvia and Southern Estonia

2016

Abstract The Latvian and Estonian inland dunes belong to the north-eastern part of the ‘European Sand Belt’ (ESB). These dunes are widely distributed over broad glaciolacustrine plains and Late Glacial alluvial deltas, considered to be potential sources for the aeolian material. Little is known about these aeolian sediments and their substratum; here we present a detailed sedimentary structural and textural characterisation together with a luminescence-based chronology. Through a comparison between grain-size, rounding of quartz grains and surface characteristics in medium/coarse (0.5–0.8 mm) sand, and the light mineral content, we found an alternation of aeolian and periglacial components.…