Dating and geochemistry of zircon and apatite from rhyolite at the UNESCO geosite Rupnica (Mt. Papuk, northern Croatia) and the relationship to the Sava Zone

The Rupnica geosite, a key locality of the UNESCO-protected Papuk Geopark in northern Croatia, is well-known for an excellent exposure of columnar jointing in volcanic rock. This rock is defined as an albite rhyolite that comprises almost pure albite phenocrysts within a fine-grained matrix composed of microphenocrysts of albite, quartz and devitrified volcanic glass. Primary accessory minerals are clinopyroxene, apatite, zircon and magnetite. Haematite, apatite and anatase were found as inclusions in zircon. The albite rhyolite is characterized by a highly siliceous, peraluminous, oxidized (ferroan), dry, alkali-calcic to alkalic composition, with low CaO, MgO, and MnO contents and high FeOT/(FeOT+MgO) ratios. Normalized trace element contents display positive anomalies of K, Pb, and Zr as well as negative anomalies of Nb, P, Ti, Ba and Eu, together with an enrichment of light rare-earth elements (REE) relative to heavy REE. Zircon from the rhyolite of Rupnica is characterized by ratios of Th/U=1.13 and Zr/Hf=55 and contents of HfO2=1.04 wt. % typical for an early-stage igneous zircon crystallized from a dry high-temperature magma in a deep magma chamber. Apatite REE patterns show enrichment of light REE over heavy REE and a pronounced Eu anomaly, typical for apatite from granitoids formed in an oxidizing environment. The magma is of A-type and was generated at high temperatures at 800–900 °C by partial melting of lower- to mid-crustal rocks. The age of the albite rhyolite of Rupnica is Late Cretaceous at 80.8±1.8 (2σ) Ma, according to U-Pb dating of zircon, coeval with geochemically similar igneous rocks of Mt. Požeška Gora and Mt. Kozara within the Sava Zone

Multilayer corona textures in the high-pressure ultrabasic amphibolite of Mt. Nieddu, NE Sardinia (Italy): equilibrium versus disequilibrium

Rocks with coronitic textures around igneous relics of olivine and plagioclase were sampled from the ultrabasic amphibolite of Mt. Nieddu being part of the so-called Migmatite Complex of northeast Sardinia. These textures are characterized by layers of orthopyroxene and clinopyroxene around olivine, and a symplectite of clinopyroxene+spinel and garnet around plagioclase; all these minerals were overgrown by amphibole. We applied conventional geothermobarometry and pressure-temperature (P-T) pseudosection modelling of microdomains in order to constrain the main steps of the evolution of the sampled rocks. The igneous crystallization occurred at 0.2-0.5 GPa and minimum T of 780-850 °C. Garnet is the last coronitic phase formed at estimated pressures of 1.3-1.7 GPa at 680-730 °C. As similar conditions were previously determined for the pressure peak on an adjacent rock, we conclude that during corona formation chemical equilibrium was reached probably over a much wider range than of mm-sized microdomains. Slow reaction kinetics is responsible for the partial preservation of the igneous phases

Garnet‐rich veins in an ultrabasic amphibolite from NE Sardinia, Italy: An example of vein mineralogical re‐equilibration during the exhumation of a granulite terrane

A complex system of mono‐ and polymineralic centimeter‐thick veins occurs within the ultrabasic amphibolites of Montigiu Nieddu hill in northeastern Sardinia, and they are filled with garnet, amphibole, chlorite, and epidote. Some garnet‐rich veins are margined by an amphibole layer at the interface with the host rock and/or show replacement of epidote concentrated in the vein core. Together with homogeneous matrix garnet (Grt1), millimetric, euhedral, and strongly zoned garnet porphyroblasts occur within these veins. The estimated pressure–temperature conditions (P = 1.0–1.7 GPa, T = 650–750 °C) for the formation of Grt1 match the metamorphic peak and early exhumation derived previously for the host rocks and confirm that the garnet veins also formed under high‐pressure (HP) conditions. The igneous protolith of the host rocks experienced HP metamorphism in a subduction zone and underwent exhumation in an exhumation channel. The vein system in the ultrabasic amphibolites formed by cyclic hydrofracturing as rapid and transient events such as crack‐seal veining. The growth of multiple vein‐filling mineral assemblages indicates the formation of separate vein‐producing cycles

Pressure–temperature–deformation–time path of a deformed garnet-bearing granite from the Paleoproterozoic Tandilia Belt, Río de la Plata Craton of Argentina

The pressure–temperature (P–T) evolution of a deformed garnet-bearing granite of La Virgen hill, located 25 km south of the town of Azul, Argentina, was studied as an example of the slightly peraluminous and deformed granites widespread in the Paleoproterozoic Tandilia Belt of the Rio de la Plata Craton. An early isobaric magmatic–submagmatic cooling path followed by exhumation was derived by the appraisal of microstructures, chemical compositions of minerals and P–T pseudosection modeling in the system Si–Ti–Al–Fe–Mn–Mg–Ca–Na–K–O–H (1 wt.% of H2O) using the software PERPLE_X. Slightly zoned magmatic garnet with a core composition of pyr4(grs + adr)11sps10alm75 equilibrated with plagioclase (XAn = 0.37) at 6.0 kbar and 655 °C in a crystal mush with < 7 vol.% of melt. The garnet rim composition of pyr3(grs + adr)12sps14alm71, texturally equilibrated with biotite (Mg/(Mg + Fe) = 0.21) at the granitic solidus of 5.9 kbar and 645 °C. The subsequent cooling path is constrained by isopleths of low-Ti muscovite with Si contents of 3.17 per formula unit commonly located around K-feldspar and recrystallized plagioclase (XAn = 0.35). Ductile deformation at low amphibolite- to greenschist-facies metamorphic conditions produced the subvertical main foliation. Forty-two chemical analyses in seven monazite grains of the granite yielded two groups of U–Th–Pb ages at 2126 ± 10 (2σ) Ma and 2089 ± 3 Ma, interpreted to be inherited from widespread magmatic events of the Tandilia Belt and resulted from the granite crystallization, respectively. The exhumation of the deformed granite from middle (~ 22 km) to upper and cold crustal levels was probably a long-lasting process after 1.9 Ga.Fil: Angeletti, Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentina. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Martinez, Juan Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Frisicale, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Massonne, Hans Joachim. China University Of Geosciences; China. Universität Stuttgart. Fakultät Chemie; Alemani

Petrochronological study of chloritoid schist from Medvednica Mountain (Zagorje Mid-Transdanubian zone, Croatia)

The metamorphic conditions and evolution of the Palaeozoic-Mesozoic metamorphic complex of Medvednica Mountain (Zagorje-Mid-Transdanubian zone, Croatia) are still a matter of debate. The results of the investigation of five samples of metapelitic schists with the mineral association of quartz, white mica and chlorite are presented. The studied schists are part of the continental margin of Adria and were metamorphosed under upper greenschist- to amphibolite-facies conditions. The focus of this study is a sample representing the highest metamorphic grade that additionally contains chloritoid blasts. Pressure-temperature pseudosection modelling together with classical geothermobarometric calculations yielded peak metamorphic conditions of 0.94 ± 0.05 GPa and 550 ± 20 °C for chloritoid schist. Monazite in-situ U-Th-total Pb electron microprobe dating indicates two metamorphic events at 167 ± 2 Ma and 143 ± 2 Ma, which are interpreted as the time of monazite growth during two distinct metamorphic phases. The formation of the chloritoid paragenesis is related to the older event (around 167 Ma) and linked with the Middle Jurassic subduction-accretion processes of Neotethys-derived ophiolitic lithologies. The younger metamorphic event (around 143 Ma) is related to the obduction of ophiolites onto the continental margin of Adria

Ashes of oxyfuel- and air-fired pulverised fuel combustion processes - mineralogical characterisation and long-term modification

The focus of our work was the mineralogical analysis of ashes obtained from the combustion of soft brown coal (93.4 % huminite, 4.2 % liptinite, 0.8 % inertinite, 1.6 % pyrite and quartz; detectable amounts of Ca, Fe, Na, K, Mg, Al, Si, S, Cl in the macerals) from the open mine site Welzow-Süd in Lower Lusatia (East Germany). The combustion process was achieved in the Atmospheric Pulverized Fuel Combustion Rig (KSVA) of the Institute of Combustion and Power Plant Technology (IFK), formerly Institute of Process Engineering and Power Plant Technology (IVD) at Universität Stuttgart in air and in the oxyfuel mode. Such ashes, which form during the combustion (oxyfuel process) for power production, were characterised with the methods of polarising microscopy, X-ray diffractometry, electron microprobe analysis and carbon/water-analytics and compared with ashes from the conventional combustion process in air

Crustal Evolution of the Northeast Laurentian Margin and the Peri-Gondwanan Microcontinent Ganderia Prior to and During Closure of the Iapetus Ocean: Detrital Zircon U–Pb and Hf Isotope Evidence from Newfoundland

Detrital zircon populations in sedimentary rocks from the Laurentian margin and the accreted microcontinent Ganderia on both sides of the main Iapetus suture (Red Indian Line) in central Newfoundland have been studied by combined U–Pb and Lu–Hf isotope analyses. Variation in εHf(t) values with age of zircon populations of distal provenance (&gt;900 Ma) reflect the crustal evolution within the source continents: in zircon derived from Laurentia, episodes of juvenile magma production in the source could be detected at 1.00 – 1.65 and 2.55 – 3.00 Ga, and mixing of juvenile and recycled crust in continental magmatic arcs occurred at 0.95 – 1.40, 1.45 – 1.60, 1.65 – 2.05 and 2.55 – 2.75 Ga. These ages are consistent with the crustal history of northeastern Laurentia. Similarly, zircon of distal provenance from Ganderia reveals times of juvenile magma production in the source at 0.70 – 0.90, 1.40 – 1.75, 1.85 – 2.40 and 2.7 – 3.5 Ga, and episodes of mixing juvenile and recycled crust at 0.95 – 1.35, 1.45 – 1.60, 1.70 – 2.15 and 2.6 – 2.8 Ga. These data reflect the crustal evolution in the present northern part of Amazonia, its likely source craton.      The evolution of magmatic arcs at the margins of both continents can be studied in a similar way using detrital zircon having a proximal provenance (&lt;900 Ma). In contrast to the Laurentian margin, Ganderia is characterized by development of Neoproterozoic – Cambrian continental arcs (ca. 500 – 670 Ma) that were built on the margin of Gondwana. εHf(t) values indicate recycling of Neo- and Mesoproterozoic crust. During and following accretion of the various elements of Ganderia to Laurentia, the syn-tectonic Late Ordovician to Silurian sedimentary rocks deposited on the upper plate (composite Laurentia) continued showing only detritus derived from Laurentia. These sedimentary rocks contain detrital zircon from Iapetan juvenile, continental and successor arcs that were active between ca. 440 and 550 Ma, and from continuing magmatic activity until 423 Ma. Arrival of the first Laurentian detritus at the outermost part of Ganderia indicates that the Iapetus ocean was closed at ca. 452 Ma. The magmatic arcs along the former Laurentian margin in Newfoundland evolved differently. In the northwestern part, εHf(t) values point to recycling of Mesoproterozoic and Paleoproterozoic crust. In the southwest, εHf(t) values indicate addition of juvenile crust, recycling of Mesoproterozoic crust and mixing with juvenile magma. SOMMAIRELes populations de zircons détritiques des roches sédimentaires issus de la marge laurentienne et du microcontinent d’accrétion de Ganderia, des deux côtés de la principale suture Iapetus (linéation de Red Indian) dans le centre de Terre-Neuve, ont été étudiés par analyses combinées U–Pb et Lu–Hf.  Les variations des valeurs εHf(t) en fonction de l’âge des populations de zircons distaux (&gt;900 Ma) reflètent l’évolution de la croûte des continents sources : les zircons de Laurentie ont permis de détecter des épisodes magmatiques juvéniles dans la source entre 1,00 - 1,5, et 2,55 - 3,00 Ga, ainsi que des épisodes de mélange de croûte juvénile avec des croûtes d’arcs magmatiques continentaux recyclés entre 0,95 – 1,40, 1,45 – 1,60, 1,65 – 2,05, et 2,55 – 2,75 Ga.  Ces datations correspondent bien à l’histoire de la croûte de la portion nord-est de la Laurentie.  De même, le zircon distal de Ganderia révèle des épisodes de production de magmas juvéniles dans la source entre 0,70 - 0,90, 1,40 - 1,75, 1,85 - 2,40, et 2,7 - 3,5 Ga, ainsi que des épisodes de mélanges de matériaux juvéniles et de croûtes recyclés entre 0,95 - 1,35, 1,45 - 1,60, 1,70 - 2,15, et 2,6 - 2,8 Ga.  Ces données reflètent l’évolution de la croûte dans la portion nord actuelle de l’Amazonie, son craton source probable.     L’évolution des arcs magmatiques à la marge de ces deux continents peuvent être étudiées de la même manière en utilisant le zircon détritique proximal (&lt;900 Ma).  Contrairement à la marge laurentienne, celle de Ganderia est caractérisée par le développement d’arcs continentaux Néoprotéozoïque-Cambrien (env. 500 – 670 Ma) qui se sont constitués à la marge du Gondvana.  Les valeurs de εHf(t) indiquent un recyclage de la croûte au Néoprotérozoïque et au Mésoprotérozoïque.  Durant et après l’accrétion des divers éléments de Ganderia et de la Laurentie, les roches sédimentaires syntectoniques de la fin de l’Ordovicien et du Silurien qui se sont déposées sur la portion supérieure de la plaque (Laurentie composite) ne montrent toujours que des débris provenant de la Laurentie.  Ces roches sédimentaires renferment des zircons détritiques juvéniles iapétiques, et d’arcs continentaux et d’arcs subséquents, qui ont été actifs entreentre (env. 440 et 550 Ma) et  d’une activité magmatique continue jusqu’à 423 Ma.  L’apport des premiers débris à la marge extrême de Ganderia indique que l’océan s’est fermée il y a env. 452 Ma.  Les arcs magmatiques le long de l'ancienne marge laurentienne à Terre-Neuve ont évolué différemment.  Dans la portion nord-ouest, les valeurs de εHf(t) indiquent un recyclage de la croûte au Mésoprotérozoïque et au Paléoprotérozoïque.  Dans la portion sud-ouest, les valeurs de εHf(t) indiquent l’ajout d’une croûte juvénile, un recyclage de la croûte mésoprotérozoïque et un mélange avec un magma juvénile