Search results for " petrology"

Robert Thomas Pidgeon

2009

Zircon ages of metamorphic and magmatic rocks within peridotite-bearing mélanges: Crucial time constraints on early Carboniferous extensional tectoni…

2013

Abstract We dated and geochemically characterized peridotite-bearing melanges in the Chinese South Tianshan and within the Main Tianshan Shear Zone. The Yushugou-Tonghuashan melange in the Chinese South Tianshan exposes a tectonic juxtaposition of a diapirically emplaced metaperidotite (predominantly lherzolite) massif with a high-grade metamorphic terrane (ca. 10 km long; protolith age ≥ ca. 445–466 Ma). Metamorphic zircons of a mafic granulite (eNd(t) = 5.0) yielded a weighted mean 206Pb/238U age of 341 ± 8 Ma that we interpret as the time of granulite-facies metamorphism. The youngest zircon rims of an intermediate granulite (eNd(t) = − 4.3) have a mean age of 332 ± 13 Ma that records a …

Kimberlite, carbonatite, and potassic magmatism as part of the geochemical cycle

2013

M20 M21

Is the Crucible Reproducible? Reconciling Melting Experiments with Thermodynamic Calculations

2011

Experimental studies and thermodynamic modelling have advanced our understanding of partial melting in the crust and have provided a frame-work for the interpretation of migmatites, residual granulites and granites. Each approach has advantages and pitfalls, and each is more appropriate than the other for investigating particular aspects of the melting process. A comparison of these two approaches may be useful because, together, they potentially give more information. A comparison of a small number of experiments with model calculations using equivalent bulk compositions shows important consistencies between the results, especially regarding the overall topologies of key melting equilibria…

Chemical variability in volcanic gas plumes and fumaroles along the East African Rift System: New insights from the Western Branch

2022

The origin of magmatic fluids along the East African Rift System (EARS) is a long-lived field of debate in the scientific community. Here, we investigate the chemical composition of the volcanic gas plume and fumaroles at Nyiragongo and Nyamulagira (Democratic Republic of Congo), the only two currently erupting volcanoes set on the Western Branch of the rift. Our results are in line with earlier conceptual models proposing that volcanic gas emissions along the EARS mainly reflect variable contributions of either a Sub-Continental Lithospheric Mantle (SCLM) component or a Depleted Morb Mantle (DMM) component, and deeper fluid. At Nyiragongo and Nyamulagira, our study discards a major contrib…

Processes in granulite metamorphism

2008

Anatectic amphibole and restitic garnet in Variscan migmatite from NE Sardinia, Italy: insights into partial melting from mineral trace elements

2014

We report results of a laser-ICP-MS investigation of trace element contents in the main constituent minerals of an amphibole-bearing migmatite from the Variscan orogen in northeastern Sardinia. The migmatite is associated with migmatised orthogneiss and Al-silicate-bearing pelitic migmatites. The protolith of the amphibole-bearing migmatite was a mid-Ordovician igneous rock of intermediate composition characterised by a biotite + plagioclase + quartz assemblage. The migmatite consists of mesosomes and tonalitic (or, less frequently, granodioritic) leucosomes, characterised by amphibole crystals (potassian ferropargasite) up to 2 cm in size. The tonalitic leucosomes are made up of quartz, pl…

Rubies and Sapphires from Snezhnoe, Tajikistan

2015

Photostability assessment of natural pyrethrins using halloysite nanotube carrier system

2022

Natural pyrethrins are one of the most used pesticides and insect repellents employed for domestic or agronomic use. However, they are highly hydrophobic and suffer from insolubility in water media and ready decomposition by photochemical, and oxidative actions. These aspects hamper their long-term storage and applicability. Herein, we report the synthesis and characterization of a nanomaterial based on the loading of pyrethrum extract (PE) into natural, low-cost, and eco-compatible halloysite nanotubes (Hal). The Hal/PE nanomaterial was thoroughly characterized, and the morphology was imaged by TEM and SEM investigations. Release experiments showed a slow release of pyrethrins from the car…

Partial melting of metabasic rocks in Val Strona di Omegna, Ivrea Zone, northern Italy

2014

Field and petrographic observations combined with major and trace element bulk rock geochemistry show that metabasic rocks within Val Strona di Omegna in the central Ivrea Zone partially melted during granulite facies regional metamorphism. A transition from granoblastic amphibolite facies metabasic rocks at the lowest metamorphic grades to metatexitic and diatexitic migmatites in the granulite facies records the effects of in situ fluid-absent partial melting. Coarse-grained euhedral clinopyroxene porphyroblasts within leucosomes are consistent with anatexis via incongruent fluid-absent melting reactions consuming hornblende, plagioclase and quartz to form clinopyroxene and melt. Field obs…